Someone had to do it… there are just too many threads out there with people looking for answers on which front end to buy for what car. Do I get re-drilled 914 rotors, a full 911 suspension, just 911 struts, SC vs. T, Vintage Koni’s, Bilstein, Boge… torsion bars, sway bars, M-Calipers, S-Calipers, A-Calipers? Whew…
What we need is one thread with all of the info in one place.
It’s quite obvious that the classic Fuchs 5x130 wheel is a desirable option for us teeners. Be it polished paddles, or full painted centers, a nice set of Fuchs (or, a wide variety of modestly priced Fachs) can really make a 914 stand out in a crowd… wide body or not. The factory 914-6 had them. The GT’s had them. They offer wider and taller wheel choices and frankly, they just scream “Porsche”. For these reasons, many 914 owners embark upon the quest to install the coveted 5-Lug Fuchs wheel on their 914.
There are about as many ways to go about the process as there are days in the month which is when the questions begin to flow. Having gone through this process a number of times for not only myself but, for countless customers, I’ve honed in on a process which involves a bit more than throwing some money at wheels, tires and suspension goodies (more on that money aspect in a minute).
First, let’s ask a few questions:
1. Wide Body (914-6/GT flares, etc.) or Narrow body (stock)?
2. How much power do you have or do you plan have?
3. What is your driving style?
4. How many miles will you put on your car in a year?
You see… it’s more than just one extra lug nut and some expensive wheels we’re looking at here. With 911 suspensions come 911 brakes and torsion bars. With 911 brakes come larger pistons and some have a much larger pad contact patch. Nice huh? Until you find your brake bias is thrown off –or– “Gee… my 914 use to be fun to drive around town, now I dread every bump in the road. Maybe this boy-racer stuff isn’t all it was made out to be.”
So… before you get stuck with a mismatched system that cost you double what it should or, you wind up with a bone jarring ride you wish you never had, let’s take a look at the options.
Starting with the “Front-End” and going from least expensive to, the most comprehensive it looks like this:
Option #1. Drilled 914 Front Rotors – First a little information on the 914 rotor/hub system. The 914 front rotor is a different animal than that of its 911 brethren. The 914 rotor has the hub system built into the rotor. This can make a 914 rotor more expensive than the 911 unit in a few ways. First off; the rotor itself is more expensive. Second; you’ll need to replace the bearings on a 914 rotor each time you get new rotors. If you’re an aggressive AXer, you could easily cook your rotors before your bearings are due. If you’re a daily driver or a summer sunny day driver, this is probably OK. That said; a 911 system has a rotor that is separate from the hub. If you cook a rotor you simply unbolt it from the hub and bolt on a new rotor. Another difference is the spindle. The 911 has a beefier spindle than a 914 so… (to answer another common question) no, 911 hubs won’t bolt on 914 struts/spindles.
All this to preface the fact that you can drill a 914 front rotor to a 5x130mm pattern. The common way to do this is to machine the hubs from the backside and press in studs, in doing so; you will have to machine through the webbing that strengthens the rotor. This is why this is no longer my first choice anymore. My preference in doing this now would be to machine the rotors from the front and use screw in 14x1.5mm studs (yes, I can hear a few screaming in horror as I type this). IF DONE PROPERLY this would be my preferred method. First off; it will not cut into the webbing on the backside. Secondly; to do it properly would require Loctite “Red”… the permanent stuff. This is, after all, a permanent application. Late model rotors will need the centering ring machined off to work with Fuchs. This requires a bit more time and money at the machine shop but, a fairly common and easy practice. Here's a thread on just that subject:
Pros – This is the cheap way and, last I checked, 914’s seem to have a way of attracting the cheap-elite. It’s good for a daily driver that won’t be raced. It’s good for that weekend, top off, summer cruiser. It’s good for the narrow bodied cars. It retains all of your current suspension and brake bits which will save you a ton of dough.
Cons – If you need new rotors, you’ll need to do it all over again. You can salvage your studs with a MAPP torch but, all of that machine work will go in the scrap heap. Even with the Loctite Red, I’d make it a habit of checking them every-so-often (ask Mr. Lowe what can happen if these screw in studs are not installed properly). 911 struts offer a factory bolt on option for a little more up-front money.
This May Be For You If – You have a narrow bodied car. You are a daily driver. You are a weekend sunny-day driver. You don’t plan any engine upgrades beyond 140hp. You’re perfectly happy with your 914 the way it is now… you just want 5-Lug Fuchs.
Option #2. 911T Struts or 914-6 Struts (only) – OK, I’ll come right out and say it; this is one of my favorite options for 5-Lug on a 914. The factory thought so too… it’s what they used on the 914-6 to give it its 5-Lug suspension. Actually, the factory used 911 A-Arms and had a special t-bar made up in the 914 size with the 911 spline count (figure that one out for me). I’ve seen factory assembly videos and, I’m guessing it was easier for them to sub out the units as a whole as the entire front suspension is installed at one time.
914-6 Struts are simply 911T struts in all measures. The odd thing is they come with a 914 part number. That said, don't be confused; the 914-4 strut is quite different. One clue is a straight steering arm on the 914-4 version. Another is the smaller spindle. Yet another is the 16mm "coarse" thread (16x1.5) rotors attachment nut vs. a 16mm "fine" thread (16x1) attachment nut for the 914-6 and 911 versions. If the odd chance (they're not that common) you have 914-6 struts, you're good to go. Part number for the -6 struts is 914 341 091 00 and 914 341 092 00. Again, they are otherwise identical to the 911 version. Again, a "guess" would have it that these had to have 914 part numbers to be assembled as a complete unit into a 914-6. That "unit" (which would consist of the strut, inserts, hubs, rotors, backing plates, balljoints, a-arms, etc...) would basically have no other part numbers on it. Having the 914.341.xxx.xx number would signify that that "unit" had the proper 914-6 17mm torsion bars with the 911 spline count.
There are two basic versions of the 911 strut; early ball joint and late ball joint. I prefer the late ball joint style as its wedge pin was an improvement over the pinch style older ball joints that have been known to oval the hole in the bottom of the strut. That said, this is a “rare” occurrence and I wouldn’t pass up a set of pinch style struts if the price was right. Just make sure the holes are true on the bottom. These struts are made by Boge. The Boge manufacture means you can have your choice of inserts (Boge, Bilstein or Koni). They have a 3” caliper mounting ear spacing. The mounting is common for the 911 M-Caliper that, again, was used on the 914-6. You can also upgrade the calipers to the ultra-lightweight Brembo aluminum 3” calipers which has roughly the same pad area as the 911 S-Caliper or the 911 A-Caliper (both of with require the 3.5” struts… more on those to come). For rotors, these take the uber-common 20mm rotor used on such Porsche icons as the 914-6, 914-6/GT, 911RS, 911ST and 76 930 through the 911SC range (ending in 1983). You can find these struts for anywhere from $100 - $400 for a pair in all of the usual places (Pelican Parts 911 Classified Section, eBay, etc.). You’ll want to make sure the struts come with hubs and preferably calipers. Hubs are the most important item as they can vary from year to year (to clearance various calipers) and, they can be expensive at around $150-200 per pair. The rest I consider throw away or expendable items. Inserts – You’ll want new ones unless you can prove they are fairly new and have low miles. Rotors – Ditto. Calipers – Most I’ve seen on these bargain struts need a full restoration. Bearings – you get the picture. The M-Caliper or Brembo and the vented rotor are more than enough brake to handle any tire or braking situation you can throw under a narrow bodied car. Yes, it is my opinion that anything more than this on a narrow car is either Internet bragging rights or… a waste of money.
Here's a shot from the CFR site showing their raised spindle mod to a 911T strut:
Let’s talk about the “Struts Only” comment. I’m a fan of keeping the 914 spring rate on 90% of these cars. Again, look at the initial questions and ask yourself; “do I really want to mess with the stock suspension geometry all that much?” A well set up 914 with stock t-bars and awesome strut inserts and modern rubber can be a dream to drive (or a nightmare… you decide). These struts will bolt on to your existing arms and utilize your existing spring rates etc. This will generally save you money and dentist bills. You’ll have a 914 that not only looks great but still drives great.
If you are building a wide-body or a narrow road-racer, you may want to opt for the entire 911 suspension as their torsion bars are easier to find in the various larger sizes. If you’re on the path to tune your suspension, make your choices wisely.
If you’ve made it this far, your probably starting to get the picture that it’s not only about the wheels, It’s literally an entirely new suspension for your car.
Pros – These can be fairly inexpensive and plentiful. A lot of 911T owners have moved to a 3.5” strut for S-Calipers or A-Calipers or even Turbo calipers. I’d be willing to bet there are quite a few of these in piles in the backrooms of many race-shops. They are a neat and clean “factory” bolt on option (wanna do it the way the good Dr. did it?). They offer a vented rotor option for your 914. Inserts are plentiful and it’s “drivers choice” Bilstein, Koni and Boge all fit and are excellent choices depending on your driving style. With the discovery of the Brembo 3” caliper, brake upgrades no longer necessitate a change to the more expensive 3.5” struts.
Cons – Price may be the only obstacle I can think of. If you’re a member of the cheap-elite, these may leave you with an empty feeling in the pit of your wallet. Sure, you can get them fairly inexpensively but, don’t forget; inserts, calipers, bearings, rotors etc. That said, going 5-lug is rarely a “cheap” excursion.
This May Be For You If – You have a narrow bodied car. You are a daily driver. You are a weekend sunny-day driver. You insist on doing it the way the factory did it. You have a wide bodied car and have decided to go with the Brembo upgrade (this is the lightest caliper I’ve found). AXer, road-course racing… all good with this set-up.
Option #3. The Myriad of 3.5” Strut Options – Be careful here… I’m equally as biased and hopefully you’ll see why. There are many choices and some are quite plentiful. There are advantages and pitfalls to each. Let’s start by listing the struts:
Koni – As the Boge 911T option above these came in both the early pinch style and later wedge pin. These will only accept Koni inserts and it can be difficult to do any custom modifications (raising the spindles, etc.) Calipers that will work are (in order of preference) S-Calipers, Turbo Calipers, A-Calipers and Wide A-Calipers (Carrera Calipers). These struts are orange in appearance from the factory.
Here's a Koni insert on my GT clone with S-Calipers:
Bilstein – These also came in early and late configurations. These will only accept Bilstein inserts (starting to see some pitfalls here?) The straight tubes allow for spindle modifications. Calipers are the same as above. These struts are green in appearance from the factory.
Bilsteins for my 911
911SC Boge – These only came in the later ball joint configuration. As a Boge strut, inserts from all manufacturers have been made to fit, so… these are a bit more attractive for that versatility alone. Calipers are as above. These struts are black.
Here's some SC Boge's that went on PanelBilly's Ride. Complete with A-Calipers
For calipers alone, I am extremely cautious on this setup for a 914. You have two basic choices; the S-Caliper or the A-Caliper. The Turbo calipers are roughly the cost of a really nice 914 for a full set. The A-Caliper and its derivative the Wide A-Caliper both weigh over 9lbs. EACH! If you go Carrera (Wide A) you’ll add an additional 10lbs. of brake rotor to the equation. Compared to a Brembo caliper on a 20mm rotor, you’ll be adding over 20lbs. of un-sprung weight to your lightweight sports car with no additional stopping power. My favorite for this set-up is the S-Caliper but… they ain’t cheap. You can find them for $200-300 a pair but they will need “extensive” work. All of those calipers will need new pistons and probably new compensating lines. And… “should” have the factory anodizing re-done. Plan on spending another $500.00 on your bargain calipers.
That said; there’s plenty of 5-Lug 914’s driving around out there with A-Calipers and Wide A-Calipers. It’s a fine setup that will offer dependable braking day after day. A pair of 911SC Boge struts would be a very competent system for a wide body or higher horse power 914. I would caution against Wide A-Calipers and the 24mm rotors (Carrera suspension). While it sounds dreamy on the outside, this is an option that only adds weight with zero gain over the standard SC A-Caliper system. Those thicker rotors were designed for a much heavier 911 Carrera that needed to scrub off speed and shed heat a bit differently than our light weight 914’s. Porsche used the S-Caliper/Rear M-Caliper combination on the 911RS and first 930 with power in the 220hp to 240hp range.
Pros – You’ll have a larger choice of Porsche’s bigger calipers available “if you need them.” Because of the popularity of the 911SC these struts are fairly plentiful. Boge versions allow a wide variety of insert options.
Cons – The best calipers can be expensive. The cheapest calipers are the heaviest we’ve weighed for a 911 or a 914 (that’s a lot of un-sprung weight to add). A full set of Turbo calipers for these inserts can cost more than a great 914. Koni and Bilstein versions are usually expensive and limited to their proprietary brand inserts.
This May Be For You If – You have a wide-body car. You have 150hp or more. You want factory brake options. You’re building a GT replica and you want the exact set-up the factory cars had. You’re an S-Caliper fan. A buddy is offering you a set of SC struts complete for $200.00. You have gobs of horse power and don’t care how much your suspension components weigh.
With all of the above strut options you can opt to bolt on the entire 911 front end with the A-Arms and all. These do bolt right up (another common question). This will “generally” be more money and you will have the 911 T-Bars to add to your suspension geometry equation. You decide if you want/need a harsher ride or not… drivers choice.
Also with the above (with the exception of the drilled 914 rotors) you’ll have 48mm pistons in your front calipers. This can throw off your braking bias. This is especially true with the Brembo, S-Caliper and A-Caliper options as they all have larger pads as well (M-Calipers have the same size pad as a 914). You may want to look into a solution for the rear such as the expensive 914-6 caliper, modified Ferrari calipers, or 911 Rear M-Calipers and a handbrake solution (it adds up fast). Don’t forget a 19mm Master Cylinder.
Speaking of adding up fast; have you checked Fuchs wheel prices these days?
A final note on custom solutions… you can add almost “any” brake caliper you’d like to these struts. I won’t delve into all of the custom applications and adapters. Suffice to say… “It can be done” if you feel the need.
On to the Rear Hubs and Rotors:
This is a system that you will have to ask yourself; “how much power and torque do/will I have?” Torque kills, and in this case you are limited by your CV joints “not” your hubs.
Again, I’ll try to go through the options starting with the least expensive and going through to a more thorough high horse power solution. First, a little education on the nomenclature of the bits and pieces required. Starting at the outside of the car and moving inward toward the transmission:
1. The Hub – This is the round device our rotors sit on which is pulled into the control arm bearing.
2. The Stub Axle – This small piece slides through the center of the hub and is fixed by the splines in the hub and the large 30mm nut and cotter pin. It determines what CV you will use as it bolts to the CV moving inward.
3. The CV Joint – 914 and 914-6 CV joints are dimensionally the same as the VW Beetle CV joint.
4. The Axle – 914 Axles are 28mm longer than 911 axles.
5. Another CV.
6. The Axle Flange – This, like the stub axles on the other end, bolts the driveline up to the transmission.
As mentioned earlier, the hub component is not a problem area with 5-lug conversions. The problems begin when you have higher horse power and want a beefier CV. The 914 hubs have a different spline count than the 911 hubs so… they can only mate to 914 stub axles (more on that as we delve into this section). On the transmission side, the 914 transmission is basically an early 911 901 gearbox with a different nose cone and a flipped R&P so… an upgrade flange can be plentiful. With that bit of information in hand, let’s take a look at the options.
Option #1. Re-drilled 914 Hubs – There are a couple ways to go about this so I’ll explain the process. Most are machined from the backside and a flat surface is “spot-faced” on to the rear of the hub for the studs to mount flush against. Then 911 studs are pressed in. There’s a slight problem I’ve found when doing this; once you’ve spot-faced the hub to accept the 911 stud you only have 3mm of stud engagement left in the hub. This means you’ll only have 3mm of hub material for the stud to press through and bite into. Factory hubs have roughly 8-10mm of hub engagement. I don’t feel this is a strength issue (as I’ve never seen a properly drilled hub fail) as much as it is an issue with the studs eventually working their way loose from the hub. We’ve eliminated this problem with our hubs by spot facing a larger area and literally welding on a ring boss to the hubs bringing the engagement back up to the factory 10mm depth. As mentioned with the front 914 drilled rotors, you can also drill the hubs to a 5x130mm pattern and use the screw in studs and Loctite Red. This would do away with the stud engagement issue as there would be no need for spot-facing the hubs. Again, this will prove to be controversial to some but done properly, it can be a low-cost option.
This picture shows how thin the hub can be if it's just spot-faced:
Here's a picture of a 914 hub with stud bosses prior to welding
Early 914 hubs (1970 only) had extra bosses for stud engagement. In reviewing 914-6 hubs from a very early car (Bob Burton’s #41) it appears a similar pattern was used on that hub as well. This is odd because that hub had a 911 spline count in the center so… it is unclear if the 914 hub was going to win or the 911 hub was in the works for both 4 and 5-lug applications. In the end the factory decided upon two different hubs. These early 914 hubs have been coveted for their extra bosses that are in place for the use of 5x130 studs. You would simply drill them to the pattern and set the studs. The only issue I see there is, these bosses are only 5mm tall so, it really isn’t that beefy but again, this isn’t a real problem area.
Here's an early 914 hub with the factory bosses that was drilled to 5x130mm
If you decide to go with a 914 re-drilled hub you will be stuck with 914 CV joints. I say this because; if you plan to go to a higher horse power motor you may want to review this application. I’d rate these good for 140-150hp with a mature driver at the helm. Remember, 914 hubs only accept 914 stub axles. 914 stub axles only accept the smaller 914 CV’s “This” becomes your limiting factor when choosing a 5-lug system for your car.
That said, this can save you a ton of money in CV’s and custom axle applications. This is literally a bolt on application that will require new rear bearings and a 914-6 rear rotor or a 914 rear rotor drilled to the 5x130 pattern to match the hub. You'll have to mill 4mm off the diameter of the 914-6 rotor and they're kindof expensive. At this point, I'd go with a drilled 914-4 rotor for this application. Once this set-up is in your control arm, you simply bolt your 914 stub axle/CV/Axle assembly back in place and you’re good to go.
Pros – This is a very cost effective solution for the 914 owner that will stay under 140hp. It’s attractive to the cheap-elite as there are no further costs or modifications associated with the set-up. It uses all of your stock components. These do not fail. They are extremely durable and reliable for normal street and even race work.
Cons – The system itself limits you to the use of 914 CV joints.
This May Be For You If – You have a narrow bodied car and it’s a daily or a sunny day driver. You plan to stay under 140hp. You’re happy with your 914 just the way it is, you just want 5-lug wheels. This is also good for autocross or road race cars that are under the 140-150hp limit… more if you think you know how to be kind to your CV joints.
Option #2. The 911 Hub and a 914-6 Stub Axle – This will allow you to use the exact set-up that the factory used on a 914-6. I am “not” a fan of this set-up for practical applications for the following reasons. First off, 914-6 stub axles are expensive. Secondly, they have the same spline count as the 911 hub which (obviously) allows the use of the 911 hub which is great BUT… they go back and bolt to the 914 CV which, once again, will be your weakest link.
The way overpriced 914-6 Stub Axle (this is a stock one):
Pros – You can do it like the 914-6. No machine work to be done. Bolt on application.
Cons – 914-6 stub axles are way too much money. This, again, limits you to the use of 914 CV’s.
This May Be For You If – You didn’t read anything above?? You for some reason think that re-drilled 914 hubs are not a good idea. My advice, if you’re OK with 914 CV’s is to avoid the 911 hub and 914-6 stub axle combo and save yourself $5-600.00
Option #3. 944 CV’s and 911 Hub/Stub Axle/Flange Conversion - 944 CV’s have the same spline count as a 914 axle and will “almost” slide on. You’ll have to machine 4mm off your 914 axles where the bottom of the CV’s mounts up as the 944 CV’s are 4mm deeper than a 914 CV. The 944 CV at 100mm is slightly smaller than the 911 108mm but should be more than capable of handling extra power associated with engine conversions. While the fasteners are smaller (M8 vs. M10 in the next example) there are more of them, six vs. 4 and two pins.
Here's a picture of the 914 axles with the needed modification
Here's the fairly rare 6 bolt coarse splined flange and common 6 bolt stub axle
A completed axle along side a stock axle
For more on this system check this thread:
Pros – CV’s are common and available. Only a slight amount of machining needed to your 914 axles. Handles higher horse power applications. Concise system that, machining withstanding, uses bolt up stock components. Depending on the cost of machining and 944 components, this may be less expensive than the next system.
Cons – Coarse spline 6 bolt flanges have been harder to find (limited to a few years before the splines were changed). You’ll have to machine your 914 axles to make this work. 100mm CV’s are slightly smaller than the 911/930 108mm variety. Uses smaller M8 hardware to fasten CV’s (the last two are probably not issues AT ALL with this set-up). You don't have the advantage of the free floating axle as seen in the next set up.
This May Be For You If – You’re looking to install a big six. You’re installing a V8 or other high horse power conversion motor. You want an extremely clean “set-it and forget-it” combo. You have a wide body car with as much rubber and power you can humanly muster into a 914. You have access to a machine shop that is capable.
Option #4. The 911 “System” with Custom Length Axles – For higher horse power applications, this is my favorite. You simply use all of the 911 components and slip in a custom length axle shaft from “Sway-A-Way”.
What’s nice about this system is, it all bolts together with no extra machining and, you get an axle upgrade with the Sway-A-Way units. These axles allow for a free floating CV which will find natural center and allow for better handling of torque. This has long been a known upgrade in the off-road racing community and, for $308.00 a pair of these axles can make their way onto your car. The 911 components (read: CV joints) can easily handle upwards of 300hp without failure. 911 stub axles slide into 911 hubs and early coarse splined flanges bolt right on to our versions of the 901 transmission.
A shot of the custom length Sway-A-Way free floating axle nest to the 911 counterpart. Note the 914 length:
Here's a shot of the 911 stub axle and CV on the custom axle:
For more on this system check this thread:
Pros – Bolt together application. Handles gobs of horse power. Free floating axles handle torque better than stock.
Cons – Can be pricey for some. Expect to pay over $600.00 for a finished system using used 911 parts found cheap. Overkill for a standard 914 with under 150hp. 108mm CV’s no longer exist BUT 930 units can be modified for the dual pin conversion.
This May Be For You If – You’re looking to install a big six. You’re installing a V8 or other high horse power conversion motor. You want an extremely clean “set-it and forget-it” combo. You have a wide body car with as much rubber and power you can humanly muster into a 914.
There you have it. At close to 4,500 words, you can see that the options and issues are vast. All of my 5-Lug recommendations come after asking the questions I’ve posed herein. Everything depends on your driving style and overall intentions for your vehicle. While I did touch on calipers, I didn’t go into detail rear caliper solutions to retain proper brake bias. Suffice to say this can be accomplished with 914-6 calipers or modified Ferrari calipers or, 911 Rear M-Caliper solutions as mentioned previously. Again, with a handbrake modification, virtually any caliper combination can be achieved with these systems. All it takes is cubic dollars.
Speaking of which; a good 5-Lug system can run you $2,000 to $3,000 dollars, wheels, tires and all. You now transverse the slippery slope. Enjoy the ride.
Eric I really enjoyed reading through this, thanks for taking the time to put it together...tons of great info here! I know that when I was looking at doing this on my '74, I really started to get lost in all the ins and outs of the different approaches.
What an AMAZING asset you are to the 914 Community. This is an awesome thread, and I wanted to personally thank you for taking the time to do this.
You may have a sportomatic flange.
I'll have to go out and take a better shots...I think I have Andy's camera but you can sort of see here how the the 911 stub doesn't sit down in the bore, it will still work, but it has no support on the shoulder now.
Off to try to get better pic's......
Good job! Sums it all up!
After reading all that, I am dizzy as hell! I'll keep my 4 lugs and Mahle wheels. But thanks for the info. It will be a big help for those who want to convert. That's how I got my polished Mahle wheels.
Thanks for taking the time and posting that i should prove to be invaluable to anyone here wanting to update their 914 suspension (or going for the bling factor)
I agree Wayne (tat2dphreak) he was a great resource when i replacing the rear suspension bushings that i got from him.. A Class Act!
But what about Option #4 ???
Some of us lazy guys, like me, just went and unbolted a complete 911 front end out of the 911 and bolted it right into their 914.
I found a wrecked '84 carrera with a good front end.
I unbolted the crossmember and steering rack, the A-Arms in the front and the shocks at the towers.
Then i rolled the whole package over to my 914 and bolted it back up.
Sometimes, lazy is gud!
I guess the first pic is as good as it gets.... this pic shows how the 914 flange sits right down on the shoulder. You may have never noticed this before and it could be a non-issue on a 914 to 911 flange. BUT if you plan to do this mod the other way (as with me putting a 901 into a bug) around it is a big deal as it will cause big problems.
Just an FYI at this point, I'll let you know how I make out when I cut the 914 flange.
That's a very rare transmission and an odd flange.
Here's what it should look like. I just ran out to the garage to take this:
You may be able to use 911 axles with that flange or, you may want to get the proper flange.
No. I don't have any 914 flanges here any more. I did pull them off that transmission and bolted in these flanges if that helps appease things.
Fantastic write up not withstanding , just a note on the strut inserts , the 911 inserts are valved different than the 914 inserts- different rebound rate and compression . If the 911 inserts would work ok , then I will keep the Bilsteins I have - inserts and all , and just bolt them on , but from all that has been posted on the forums about the differences between the 911 inserts and the 914 inserts , I won't be using them.
Mark henry , Eric is right about the tranny flanges you are trying to use , I got a pair of 911 108's to do a swap onto my 914 side shift and there was no problem in the mounting of the 108 flanges. I did however switch to the 911 100mm flange to make use of the 944 cv setup , and again the 911 100 flanges slid right in no problem at all with the flange shaft length . You may have to hunt some more on the getting of the 108 tranny flanges . Heck before I found the forum I had got a pair of so called 911 6 bolt flanges off of evilbay , only to find out that they were the real early 6 bolt small circle flange IIRC about 93mm size - no real use to me or anyone else except some body restoring an early 911 that used this size of flange , heck I don't know of what cv would use with these . anywho , you may need to look some more, good luck.
Jack / Jaxdream
Regarding valving on inserts. I had a long conversation with an Engineer at Koni who stated the valving is only different slightly on the high speed rebound (he looked up the values while we were on the phone). An early 911 front end and a 914 front end are only a few pounds off from each other in the grand scheme of things. He stated the valving could be changed (for my Koni 911 strut inserts) but I probably wouldn't notice it at all.
Not sure what Bilstein would have to say. I would simply bolt them on if it were my car. If I recall, the 40 lbs. difference isn't worth the worry.
Quit looking I found one.
I also remember something the Dr. was thinking with the 912 diff, but that would have to be confimed.
I'll have to measure them proper, but they "ballpark" measure .150 longer overall.
They still sit on the seal OK.
Thanks , Eric , that's a great thing , just wasn't that sure considering all the debate over the valving difference between the 911 and 914 . Shoot I'll just run them and if I don't like em I'll just switch to the 911 spindle 914 strut hybrid I made up, used a 89 911 spindle pressed onto a 73 914 strut tube to use the Boge 914 inserts I have .
Thanks again , like I said in my earlier post , Mark has an as you put it rare tranny stub shaft setup.I have went through the same thing checking the differences between the 911 108's and the 914 tranny stubs .
Jack / Jaxdream
On the front, I did the "Sir Andy Way" after changing over to Koni's and new sway bar, torsion bars, etc. The back I first did the five lug mod to 914 hubs but am now doing the 911 hub, sway-a-way axles, and larger CV joints.
Excellent writeup and follow comments are very appropriate.
Sway-A-Axle set I believe to 20.25 inches long. Will look up the part number and see if it is available. We also need the 911 CV joint part number, size, etc. that is available. I believe the 100mm CV joint is still available.
Anyway, excellent information.
The only real issue I'll have is the smaller 914 flanges will need to be cut on a lathe a bit to fit the diff on the 911 into bug conversion .
Stunning Eric, but it has given me a whole bunch of new ideas and headaches...
Thanks Eric! This is so informative!! Appreciate all your guidance!
One question I have that you did not address directly, will 914 calibrated Koni, Bilstein inserts for Boge struts fit in 911 SC, Carrera Boge struts or do I have to use the 911 calibrated ones?
Great write-up Eric! I also second the notion that Eric is a great resource and vendor.
Can you expand on how the 108mm 930 CVs need to be modified? Or will it be obvious once I get to that step in my project...
Most excellent write up. You sure saved me a lot of thread surfing and confusion.
John, I'm not sure about that one but I believe they do. It has been discussed here but, I forgot the thread and the answer to be honest.
930 CV's - Good question. Because the 70's 911 108mm CV's are NLA, you can sub it with the same size 930 CV. It's the exact same issue we have with 914 CV's and Type 1 CV's. The 911 and the 914 are 4-bolt 2-pin systems and the 930 and the Type 1 CV's are 6-bolt systems. The 930 CV, stub axle and flanges can be modified for a pin or, the stub axles and flanges can be machined for a pair of M10x1.5 fasteners.
Thanks Guys. Happy to help. I've been thinking about this one for a few years it seems.
Eric, thank you for this. Perfect timing for me as I'm about to finally start working on my teener that's been sitting in the driveway for the last 4 years and a 5 lug set up is in the plans.
Most of that went right over my head BUT I think I now know what I'm going to do.
Very thorough write up Eric. Thanks for getting it all in one thread. I posted somewhere about some Bilsteins that the part number crosses to both the 914 and the 911, The part number is: F4-P36-0113 HO, also the bilstein gland nut number for the boge strut to hold the bilstein insert,(911T strut) is: B4-B36-U242E2 I got this from Victor at bilstein 1-858-836-5900
Also my preference on the emergency brake shoe expander/cable solution is the later angle pull 944 hardware. I will also use the 944 cables and a center eb handle probably but lately I have been thinking about the eb pedal in the wifes camry. You press it to set it and press it again to release it. I know theres not much room in the pedal area but we will see.
Great write-up Eric. I would add 2 things.....
All things being equal, the "hub centric" flanges are more desireable. They allow wheels to center off the hub instead of the lug nuts.
When I built my car with the 108mm 911 tranny flanges I ran into a set where the shaft area that fit into the diff was about .020 smaller. I doubt if anyone would even notice. It would have been catastrophic if used. I have played tag with too many trees and can't remember the exact details other than they looked perfect but were a different size. The point to remember is to slide the flanges in the diff (without seals installed) and make sure there is no movement. It was California Motorsports that got me the correct diameter flanges. Sorry I can't remember more details
Great write up Eric. And it is nice to have it all in one place!
Can we nail this to the top of the list with the other classic threads? I probably used all the wrong interweb bulletin board terms, but it would be great to keep thi one easy to find.
Does anyone have the answer to John's question? I'm in the same boat where I have bought a set of Koni sport adjustable shocks for a "914" but I don't know if the same insert fits the 911 Boge or Koni struts. I could check to see if my shock boxes have any part numbers left and compair that to the 911 numbers.
Also as far as brake caliper mountings go, does anyone have a thread that references caliper mounting hole spacings? Also curious to see spacings for calipers that don't use the "ear" style, like on the late model front end Brembo calipers. I believe from the 993 on (in the 911 circles) they switched to the bolt through the top of the caliper mount, but haven't crawled under too many 911 cars. I know 928's switched in 87 when the S4 came out but 944's never adopted this style.
I want to thank the op for this post, helped me solve my axle problems on my kit car.
Putting $2K to $3K into my 4x4 '74 ought to make fore pretty good suspension
This thread before Goldmember pic: Awesome.
After Goldmember pic: Epic.
I have a front end out of a '84 carrera. Back end is stock 914 with 5 lug rotors. I also have a 19mm mc. I am not happy with the performance. I really have to put out a lot of leg pressure to get the car to stop like the way I think it should. I have firm pedal feel but I have to really push down much harder then I thought I would. I thought by going this route I would have something similar to power brakes. I figured I would have fantastic brakes that wouldn't need so much pressure to get them to stop. Just want to know what I should expect? By the way 3.2 powered.
Believe it or not, this is a common syndrome.
The cars with the A-Calipers (911SC and 911 Carrera) have a brake booster (power brakes) so there's one issue.
You may be like most people driving a modern car most of the time which also has power brakes. That's another issue.
Modern pads tout "no squeal" performance. No squeal yes. Performance no. That may also be an issue.
You now have 24mm rotors performing the task of "rotating mass" on a 2,300lb car. These rotors have zero advantage on our cars and only a negative return of added, unsprung weight. The SC version carries the same caliper (so, same pistons, same pads, same everything...just smaller spacers) but it sits on a 20mm rotor. That rotor is lighter and easier to slow down on a light weight car.
You are now front bias heavy with the 48mm pistons up front and the 33mm pistons in the rear. That can be an issue.
Add all that up and here's what I get:
1. Unboosted brake systems from the 70's don't feel like modern day car brakes so... the brakes in someones Chevy Cruze may "feel" better to the average driver than those on a 914-6/GT equipped with 908 calipers and GT rears. (you have a lot of Porsches and a handful of vintage examples so, I doubt this is your issue... it is for a lot of people expecting that easy pedal and screeching halt stops though).
2. Pads can make a big difference. BEDDING your current pads can help as well. If everyone went and bedded their pads this weekend (yes, even old ones) following the bedding procedure on our site, they would come back reporting better brakes on Monday. That "may" be it.
3. 24mm rotors and Carrera calipers offer a ton of weight to a 914 braking system. Weight that is simply not needed. Weight in "rotating mass". Think you need them? Go watch Frank Beck in his 914 in HSR Series racing. Report back. He's one of the fastest guys I've seen in a 914. They are all using S-Calipers and 20mm rotors. If you have to run the A-Calipers (the heaviest caliper ever put on a 911) then I would default to the SC variety which uses the 20mm rotor.
Finally, make sure your rears are even in the hunt. I've said it before and I'll say it again here. "Most of the rear calipers on the cars on this site are probably not even working." Again, Buck, this isn't a crack toward you or anyone else for that matter. It looks like you have a wide variety of vehicles and I'm hoping they get maintained appropriately. Let's just make sure the venting clearance has been set and the rears are even doing their job. That should bring a 30% improvement for a lot of 914's out there. If the same guys who are going to bed their pads, set their venting clearance first, we should see a dramatic improvement.
I hope that helps.
You wasted so much time writing about guitars....
One thing that isn't called out explicitly:
What bearings are needed for 3.5" front struts? I know there's a front and back, but what about the washers and gaskets?
I have a set of Boge struts and it looks like there's a bearing chase stuck on there, but I can't be sure. I want to replace all the bearings, but also want to make sure I buy the right ones. When I look at the parts diagram, there seem to be a number of different pieces needed.
On a 911 the ring needs to stay, the dust seal goes inside the hub and seals up to the ring. The inner wheel bearing sits inside the hub and slides on to the stub axle.
There is a very thin plastic washer under the collar as well that confuses people when looking at the diagram.
Any chance the stub lock nut is the same on the 3.5" struts as the 3"? I have 3" now and will be upgrading them shortly, and I already have fresh bearings. Just trying to figure out what I need to buy.
They have changed over the years. They could be the same, try them.
The spindle nut on a 914/4 is threaded different than its 911/914/6 counterpart.
The 16mm spindle nuts are NLA, for 911 struts to '73.
The available 18mm spindle nuts fit later '74 to '89 911 struts.
FYI... a few years ago I did some digging with a local bearing seller. We found two tapered roller bearings with the proper OD for a 911 hub, and the proper ID for a 914/4 spindle. We also found the proper seal.
I was going to buy a couple dozen sets and offer them for sale on world for easy 5 lug conversions. Just bolt on the rotor and an 3" M caliper.
When I went back a few months later, the manufacture had discontinued the inner bearing.
The kit was only about 60 bucks for both sides.
No, you were right Eric.
I have 911 "A" struts and M calipers on there now. I'm going home now to wrench for the rest of the day and I'll see what I've got. Either way, I can order new spindle nuts and make sure that I have the right thing.
As soon as I get the car stripped and off to the sandblaster, I'll start working on the suspension in earnest. I've got time to see what I need to order to make sure it's done right.
I have 3" on there now, and will be putting 3.5" on. So I think these bearings are for the 3", and not the 3.5" that I have. Right?
I couldn't find these bearings listed on any of the parts websites we all use. When I pulled the hubs off of the 3" struts, they slit right off. I couldn't get these bearings on the 3".
If anyone can follow all of that...I'll be impressed!
The spindles themselves are all the same on the 911's. Just the threaded end changes so those are good for either.
So, all you need to convert a four lug 914 strut to 5 lug is a 911 hub with bearings that fit the 914 spindle?
What is this? Amateur hour?
Ummm put'th thy crack'th pipe down'th.
It "was" an otherwise "accurate" "classic" thread.
Smallish 914 inner bearing measurement:
Not as smallish 911 inner bearing race measurement:
There you go dealing in facts again!
But hey! feel free to delete any of my posts to return this thread to classic status. Your "how to" threads are a blessing!
A few wraps of duct tape will take care of the mismatched diameters. Or grease. Just pack the gap with grease. Problem solved.
914-6 struts are the same as 911T struts yet have a 914.341.xxx.xx part number.
You should have verified what an actual 914 strut looks like as well. They are quite different.
Love the comments though, caps, quotation marks, red text and all.
Sorry my bad
No worries Tom. Thanks.
I'll grab the part number that Mark posted and include them.
Just a thought - could you not have a custom race made that would fit the larger diameter of the 911 with an inner diameter that would match the bearing portion of the 914 bearing (and thus match up with std 914 struts)?
Not sure this would be cheaper than the 911T strut option, but if made in quantity...
Clay was looking for such a bearing and, with so many bearing options, you would think it already exists. That's what he mentioned on the previous page... it doesn't seem to exist. The solution there would be to have a machinist spin up the "outer" race so it would fit the 911 hub with a 914 bearing in it. Then it has to be hardened. Costs are now mounting in the face of a proper strut.
Then you would have to deal with caliper and rotor offsets. The "early" 914 struts would probably be your only option but, it probably would line up properly for a vented rotor (which is the main advantage of a -6 over a -4 in terms of front braking). Add up machining adapters etc. and again... I believe we're back to the proper strut being a less expensive and less "kludged" option.
Eric, my next race car will be a historic 4 which will stay 4 lug. It will have more than 140 hp, so what is the best option for the CV's? I suspect it might be drill the dowell pin holes and use extra bolts, or will they just detonate the same.
This is my favorite system:
Not only do you get the largest CV's available, you get the real benefit of the free floating axles which allow the CV's to find their natural torque band and no adapters.
Wow great read, thanks for putting this together!
I have a older GT clone that came to me with a few issues. Car is rust free (pretty much), and was a race car/track car on the west coast, I am converting it back to a street car- I figured it easier to civilize a race car than fix rust.
One of the PO related problems is someone forgot to tighten the axle nut on one side which trashed the Hub's inner face.
What I have is Porsche P/N 901-331-605-06
I'm not sure what year 911 hub to look for.
Any help appreciated.
Great article and technical info...Really like the way you used the Pro and Con format, and took the time to explain these to the reader. As a relative new comer to the 914, your information is very valuable to me.
I did that 914-6 GT!
If this isn't already a "Classic" thread, it should be. Nicely done, Eric!
@http://www.914world.com/bbs2/index.php?showuser=1110 so adding to this informative & lively thread, I re-read it since Pete bumped it to the top & noticed that you left off "EARLY-early" front struts IE: -> 1968 available on 911/912's SWB as an option ?
Is that because they cant be used?
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