I may track my car one day but it will never have slicks.
My arms will never be scientifically tested.
I feel empirically that I've added stiffness.
Do I even need stronger arms with my current tires ?
The modifications are for my own satisfaction.
There is of course artistic and technical pride.
Absolute maximum tire ? ...... maybe in the future, right now I have a combination
that is quite enough. A more powerful engine may change that.

God I am too cheap on everything I do..

The problem becomes that these items can get very expensive very quickly. Especially if you do the engineering. We are currently working with a known suspension company that makes race suspension to offer up a kit. We are hoping that thee may see the light of day in summer. We had thought about getting into this market, but when you start jacking up loads beyond the factory spec things can get dicey. This is why we offered to handle distribution once they have a turnkey kit.

Time will tell.

If you're running this kind of power, a narrow body car seems like a non-starter to me. HP without the ability to ground it is nearly worthless. Yes, modern rubber makes up for some limitations of tire size but let's not forget that when the factory moved to GT style horsepower, the flares were put there for a reson. Form follows function.

Once you go to flares, it solves the tire clearance problems.

There are other benefits that come with flares and the ability to run staggered tire sizes to balance the car. High HP needs more tractive effort at the rear while simultaneously offsetting the tendency toward throttle induced oversteer and drop throttle induced oversteer.

My point being the flares aren't an afterthought or for styling, but, are part of an engineered solution to manage the horsepower and balance the handling. Seems like you're after a complete re-engineering of the suspension in order to avoid flares and a repaint. I'm probably missing something else.

Of course, by my avitar photo, you'll notice I'm biased.

I would expect that Porsche intended the trailing arm to be the sacrificial element in a collision rather than the suspension console.. So agree for a street driven car reinforcing the trailing arm may well lead to much more expensive collision repairs.

Not sure how sophisticated structural analysis was back then, but now everything is modeled in 3D graphics which makes finite element structural analysis easy, so designers now can see exactly where deflections occur and design accordingly.

The large diameter tube reinforcements are a much better design than the small tubes seen in some other mods.
Remember that the stiffness of tubing increases with the 4th power of diameter. So you could have a much stiffer mod and lighter by using thin wall tubing.

Good points, and fully agree on the ability to put the power down (in general) as I enjoy a handling car over a power car. Of course, I don't mind when they're got both…

Some quick thoughts re: your thoughts of "this level of power" and narrow bodywork:

1) I'll take the blame for noting hp vs lb-ft when torque is what really matters, but nevertheless feel 185/195 & 215/225 15-inch and 205 & 225 16-inch are a good tire package for RS 2.7 > Carrera 3.2 power/torque. Porsche engineers—no dummies—also seemed to think so, and used those sizes on 911s with up to 210-230~ hp and 180~ lb-ft from 1973 through 1989, and then again with the standard 16s on the 1997-2004 986 with 200 hp/181 lb-ft—a car that is 700-900 lbs heavier than our 914s. Also: Tires today are better than tires of the 1970s, 1980s, and even the late 1990s/early 2000s.

2) The factory's decision to flare the competition 914-6s probably had more to do with increasing track and lowering lap times than an inability to put the torque down—as the 914 ran in the 2.0- and 2.5-liter categories and didn't have a lot in the way of torque, something that's never been the strong suit of Porsche's normally-aspirated flat sixes. We only think of the 3.0-4.0 engines as "torquey" because they are—relative to the 2.0-2.7 engines, anyway. But even the hottest NA flat sixes making 500+ hp post up pretty meager torque numbers against other engine configurations making 500 hp.

3) I have a fair bit of seat time in cars that can easily overwhelm their driven wheels. More often than not, they aren't my thing—I'd much rather have a car that handles well than one set up to spin its tires. Probably why I like 914s so much. My take with my 914 is that 185s in the rear, even very grippy vintage race tires, is almost CGT-ish (in a very perverse, CSOB way. ) Put another way: It doesn't feel all that reassuring. First step in optimizing my car's handling is tire selection, hence a lot of thinking at this stage.

4) I don't claim to be "right" about this, as it's absolutely a best guess, but 20+ years of testing all sorts of Porsches + studying their development + speaking to the engineers behind many of them has me thinking 185/70 or 195/65 & 215/60 (15-inch) or 205/55 and 225/50 (16-inch) is a good setup for a narrow 914, neither over- or under-tired for a 914 with 180-230~ hp. Fenders that will accommodate would also provide space for 205/50R15 and 225/50R15, opening up a great selection of autocross and track tires—or maybe even 225/50R15 square, which was on what remains probably the best, most fun 914 I have driven.

5) Big six, as in 3.6, 3.8, or 4.0? Yeah, I'd want GT/M471 flares—but I don't need a big six in my 914 and don't want to flare this car. I wouldn't call narrowing my arms, or wanting to see a product for 914s like those for 911s, a complete re-engineering. One could argue big sixes, flares, and 245mm+ rear tires will prompt something much more like re-engineering of the 914. In exploring ideas to add 5-10mm of space where the 215/60 hit my trailing arms, I started to wonder if there's a better solution than doing what's been done to 50yo arms in the past.

The bodywork is no big deal, and has been done quite often. 225/50R15 has been snuck into a fair few narrow 914s with minor pulling/rolling, and 215/60R15 has been too. Still trying to nail down what was involved in sneaking 225/50R16 into this car. At the time I commissioned an article on the car for Excellence, it sounded like custom offsets + trailing arm tricks. Reading the piece above, I do wonder about the fenders…but whatever was done, it was subtle.

Bottom line, I'm interested in "adapting what I have." If I can sneak a 215 into my rear fenders with some pulling/rolling, that's a lot more attractive to me than welding on GT flares and changing the shape of my car—and I'm not sure the idea that the right answer is always GT flares, particularly for "small" or "mild" six conversions (i.e. warm or hot 2.2-2.7 or stock 3.0/3.2). Judging by the page views on this thread, I may not be alone. Now add in the brake and stub axle upgrades most people do with a six conversion. If we're gonna have to do it anyway…

From the link above:

The 16x7-inch Fuchs that the 914 rolls on may look stock, but they’re actually custom items that were made by Harvey Wiedman of Wiedman’s Wheels in Oroville, CA. “Having run aftermarket seven-inch rims on my race car, I knew 225s were possible,” explains Wolcott. “I also knew I wanted the classic Fuchs wheel. However the key to seven-inch rims with 225s on an early narrow-bodied car like 911s, 912s and 914s is the backspacing. Unfortunately, while made Porsche made seven-inch Fuchs, they never made one with the backspacing I needed, which is where Harvey Weidman came in.”

When Wolcott made a call to Weidman, it just so happened that Weidman had been dealing with a similar dilemna for his own early 911. “He had just finished work on a set of prototype wheels for his own early-bodied 911,” continues Wolcott. “He said once he shook down his own set, if all went well, he’d do a set for me. The way he described it, it was taking two sets of 16 x 7 Fuchs, cutting each in half, then welding the appropriate halves back together.” The outer rims pf the wheels were polished and the centers powdercoated to match the 914’s custom badging. Tires are BFGoodrich G-Force KDs that measure 225/50ZR16 at all four corners.

From our own Bruce Hinds:

I'm running Falken 215/60 x 15 all the way around. The wheels are 911 SC phone dials, 15 x 6 on front and 15 x 7 rears. As I understand most 911SCs had the 16" Fuchs, but that was an option and the phone dials were standard.

I did stretch the rears with a bat to get them to fit, but it's a nice set up. When I get new tires I may go 205s up front, I've been told the 215 is a little wide for a 6" rim.

From our own Keyser Sose:

Here, some 215x45x16 on 7" 911 SC Fuchs, front and rear:

Also from our own Keyser Sose:

And my son's car, 225x50x15's on 7” 911 cookie cutters:


If I remember right, this car had to have the fender support ahead of the LR cut and rewelded to allow the fender to come out of bit, where the RR fender did not require it.

Obviously, the less you have to pull, the better—which is also part of why I am looking at 911R offsets, custom spacers, and narrowing the trailing arms.

Nice set of well thought out counterpoints! You and I are on exactly the same page on point #3; I'd much rather drive a well sorted car than one that spins the tires in all the wrong places.

I tend to agree that you'll have more success managing tire fitment via custom rims and backspacing.

Double bonus points go to the picture of the 914 with the raft on top. Love crazy strapped to the top of sports cars. I have a long history of doing similar things.

James' car. I haven't seen it in a while. An amazing car built by a father and son
James moved back to NM a few years ago, I haven't seen him since. We used to race against each other a lot with his track car

If a custom Wiedman wheel takes two Fuchs, cutting, welding and finishing to make the end product, I'm guessing 300 each wheel, 400 to cut and weld, 300 to finish, 50x2 to ship each way. $1,100 + per wheel - My guess.

So there are multiple problems with the stock rear suspension. Addressing all of them isn't trivial. In no particular order:
1. Rear chassis is weak/flexes
2. Rear trailing arms are weak/flex
3. Rear suspension geometry isn't great. The roll center is relatively high, camber gain is less than ideal, it toes out as the suspension moves in bump, and has more scrub (side to side movement as the suspension moves up and down) than ideal.

1 and 2 require fabrication, but are possible without doing crazy mods, and can be a significant improvement for a racecar, or a car with a lot of power. #3 is harder because you have to change the suspension pickup points (major chassis mods) and build all new trailing arms. A big project.

I did a bunch of suspension geometry modeling for my racecar using a program called susprog. I actually redid the front using newly fabricated struts and A arms and all new pickup points. Made a big difference in the car's handling. (On the rear I basically did #1 and 2 above when I built the car.) I haven't redone the rear yet since it's more work. Someday ...

Probably about right. Harvey can likely widen my deep sixes without refinishing the fronts, but not sure I want to cut them.

Or one can just buy these, new and ready to go, for $500ea:
https://tremotorsports.com/exterior/fuch-st...deep-6-7-wheels

Selling a set of 15x6 flat Fuchs that are less than perfect would go a long ways or even cover a set of these.

There are also these:
https://www.stoddard.com/91136102011-rpb.html.html

From everything I can see, these are high-quality wheels, made for rallying and circuit racing. $435-500ea seems strong value to me.

"The large diameter tube reinforcements are a much better design than the small tubes seen in some other mods.
Remember that the stiffness of tubing increases with the 4th power of diameter. So you could have a much stiffer mod and lighter by using thin wall tubing. biggrin.gif "

Wow. Thank you Mr. Barefoot

Hey Pete how much do you need removed for tire clearance ?

Great inputs here.

Still think 986 wheel carrier idea from Chris has legs. Someone has pointed out that it has Weissach Axle geometry, but that's passive/active through the arc and I am not sure it matters if the carrier is literally just a carrier and rigidly attached to a trailing arm. Someone else pointed out that machining off the 986 carrier's strut mount may affect its strength, something that definitely has to be considered, but again the right trailing arm could account for that—and provide a lower mount for the 914's damper—maybe height adjustable for lowered cars?

So everything comes down to the trailing arm. I look at Tangerine's pickup point relocation kit and would do that in a second on a race car. I look at the trailing arms, and wonder what possibiities for correction with new arms. And if they're black, and not not blatantly hideous, one suspects there are some interesting corrections to be made. Look how far the 1964-1989 911's rear suspension was developed—both by Porsche and the aftermarket. Now consider the fact that, more often than not, even many 914 race cars have been built around trailing arms optimized for the 1970 914 & 914-6 and never revisited.

The engineering and construction of new trailing arms is way past my pay grade, but already this thread has brought out some interesting ideas. Worst case, I narrow/scallop some stock arms and sell mine. But one can hope…

Would have to really look at it, as the answer is "kinda" important, but after relocating the brake line…5mm? Maybe a bit more?

Exactly, the engineers who designed our 914 probably were not planning on 225 or any wide tires, OR the loads wide tires will impose on the suspension/chassis/etc.
This is my first 914 and I am planning on going with 185 tires, to take advantage of the "wiping" technique described from 356 sporting drivers. But I am old school

It's tough to put fake Fuchs on your car once you have real ones. They look similar in pics but not so good in real life. And most are heavier.

Agree with your logic (as usual), but two things:

1) These aren't like the Fachs of the past, in quality or "almost" appearance—or, for that matter, focus on appearance and cheap cost. The Group 4s, in particular, look very close (probably close enough for me…still mulling having Harvey widen two of my 15x6s—but that brings up other questions).

2) My research indicates they're within a pound of forged Fuchs, and made by companies that supply rally wheels—so they appear to be quite strong. One can argue the merits of new cast 15s vs 50yo forged 15s with unknown # of heat cycles, impacts, etc. til the cows come home. I can see it either way, and it's probably six of one, half a dozen of the other.

Or one can look at it more simply: I'd rather have the tires I'm after on good (or good enough) wheels than be stuck with tires I don't want on real wheels.

I'd actually say it comes down to the trailing arm and also WHERE you attach it to the chassis. The relocation kits I've seen are an improvement over stock, but as far as I know they still assume a stock trailing arm. If you're building a custom arm anyway, there is a lot of improvement to be made by moving the pickup points around (not just moving them upward). It would need to be modeled to do it right. There are a few suspension analysis programs out there. I used susprog, but I believe there are others. Some of the changes that gave me the results I wanted were not intuitive at all. And of course there would be a lot of cutting and welding involved once you design it.

Scott

I have a question. Does anyone think we are pushing our suspension and chassis design in spirited street driving beyond the design limits?

I have never added chassis stiffeners or even anti-roll control to my Alien. I drive the hell out of it. I have to admit the torque kills the traction. I can throttle steer the car even with 255/50/16's on 9's on the rear. Maybe it's all the years of winter driving or something.

I guess I am wondering out load about the amount of re-engineering of a really good stock design. I am of the mind that on a narrow body car the design allows for a manageable spirited driving experience. Even on track day.

When I did the 7 of 9 I never felt I needed to do anything other than be sure I was in the right gear to stay in the torque zone. (narrow, factory anti-roll, 2.0 FI. Lightened flywheel) The lightened flywheel allowed for faster spin up but killed the inertia.

I agree it would be nice to have a low cost solution to trailing arm clearance. But my seat of the pants tells me we are discussing an option that would provide very little benefit for a cost well beyond a set of custom wheels.

I am all in for a low cost nip/tuck on the trailing arm though. Simple 914 solution to increase the foot print without the Rube Goldberg approach to modification for the sake of saying we did something.

I understand the desire for wanting more. The conversation started out as the need for tire clearance. I am wondering with the right compound on track day if the narrowed stock arm would be enough. Lets face it. I am not sure a redesigned trailing arm will stop the throttle lift spin condition when corning too hot. LOL! I think that is a bigger problem..

Great topic though. Just goes to show how great these cars are when we have to debate the benefit of changing something from the original design.

It is also a discussion on unsprung weight. Question: Is there always benefit in reducing unsprung weight? I feel like I should know the answer but alas I am just an old hot rod guy that fell into the seat of a 914 and never had a desire for the old iron again.

Pete - Would adding an LSD to your trans help you.

So many good inputs and gut checks here. Maybe someone can point out the blind spots, but I see them falling into three primary categories:

1) Handling dynamics
2) Engine power output and delivery characteristics
2) Driver skill/style/preferences

That last one is a biggie. Actually all three are.

Agree this discussion only highlights how great these cars are—and it's generally accepted that less unsprung weight is better (so long everything is strong enough, etc). This discussion has moved me away from the drive to reduce weight on the trailing arm—though any savings, even minimal, would of course be nice—if other objectives can be met.

This thread has me thinking the better/more likely place to reduce weight—both unsprung and rotational—is the steel caliper and one-piece cast-iron brake rotor. The only reason I've stuck with the [/u]hefty stock calipers is to have an e-brake, and all these photos have reminded me just how smart the 911/986/etc drum-brake e-brake is, by doubling the use of the inside of the brake rotor's "hat." Looking at the e-brake on the 986 carrier, it really doesn't look like a lot of extra weight. I also wonder if an aluminum hat is mechanically viable with a drum-type parking brake?

Another option for an e-brake is the RSR type clamp offered by Zuffenhaus alongside their insanely cool and period-right RSR/917-style finned calipers, but I am afraid these are simply outside my budget against 986 calipers…especially used/refurbished ones. And I'd switch to four-piston 986 calipers in a second, as I've also learned one of my other preferences: I prefer a sports car that's "over-braked" to one that's "under-braked," and have run into fade in some pretty serious machinery. You can always drive around it, but I don't like serving my brakes' needs—or even thinking about them—when pressing on.

Doesn't really affect my interest here, as the desire to go to 185/215 is about stability and handling dynamics in all conditions over an ability to put the power down. The latter is controlled with my right foot, and has been a non-issue so far.

An LSD is on the list, however, for whenever the transmission comes apart next as a good one does offer some stability/predictability advantages.

Here is a thought to reduce unsprung weight. What about a smart conversion to inboard brakes like the Jags have. This may be an easier conversion than anything we discussed to date.

I'm not sure what Pete has on his car now but if they are ATE steel calipers then going to 3" Brembo or 3.5" S calipers and PMB aluminum 914-6 calipers would save 8-10lbs.

I know the PMB rears are nla but there are always parts available if you look and ask.

I am still in the belief that front suspension is 75%, rear 25% so tuning the front suspension is more important. That's from my bike riding and racing experience so I realize I have a huge knowledge gap for cars.

There are at least two problems (that I can think of) with inboard brakes....

1. U-Joint/CV Joint Windup. It puts more load on the CV joint due to braking, and that causes windup in the drivetrain.

2. Heat Dissipation. It adds heat inboard where there is less airflow, causing both brake fade and possible other heat induced problems with the transmission.


I think the benefits of less unsprung weight are outweighed (pun intended) by the drawbacks. If it were a huge benefit, we would be seeing inboard brakes on a lot of modern performance cars.
Clay

Ya, you would need to change to real U joints like the Jags and Corvettes. I see the issue with the CV's

^ Yep on steel ATE rear calipers. Have 3' Brembo aluminum calipers up front that I guess could be moved to the rear if there are 911, 986, or RSR-type e-brakes, leaving room for a caliper upgrade up front. Would need to research what would be balanced with the Brembos if they move to the back. Or just go with a f/r system that's matched, whether 986 or 930.

But first, need to know what I am mounting said rear calipers to.

Losing 8-10 pounds would be worthwhile, and might be increased with the right rotors. I had a race shop drill my "hats" last time around, partly to cut a little weight but mostly for the fun of it…as it's a little detail I like on the 917s (not to mention modern Audis…with the common denominator being Piëch). Could a pound or two be shaved from each trailing arm? Or 3-5? Or maybe new arms would be even steven or even a bit heavier but offset by aluminum calipers and new features. Too early to tell, but a bit here and a bit there can really add up—and a lightweight battery plus 10-20 pounds out of the rear suspension and brakes might offset 30-50% of the weight gain with my six conversion in roughly the same area of the car, and I do miss the light, tossable feeling of my car as a -4.

Agree on importance of front suspension, but might put it closer to 50-75% (not sure where it falls, but I'd put it closer to 50%). Believe me, I have ideas for the front suspension, too. The difference is: Great options exist and are readily available—it's just a matter of budget…and figuring out what it will be paired to in the back!

Yep to all that.

A light battery is definitely low hanging fruit.

996/997 rear susp. Would make sense to fab a steel subframe that fit under a 914 that had the wheels tucking appropriately. Use the 914 axles if possible. Welding to the chassis would make it much stronger back there.

Remove the no longer needed inner trailing arm mount and a Boxster engine should fit. But that is a whole different ball of wax. But then you could likely do a Porsche -6 swap for $10k all in...

Ignore the red circles... best pic I could find quickly.

I love the idea.
......those upper links will extend well into the trunk/wheelhouse.
We're looking at the drivers rear hub from the roll bar down
.....but not exactly a DIY solution

I can see it for those willing to cut up their chassis and/or go to something other than a Type IV or 901 flat six, but will probably push the wheels well outside of the fenders outside of a narrow body 914 and require either modern wheel offsets even with M471 flares.

I've been thinking about your idea with the 986 carrier ever since you posted it, and the more I think about it, the more it makes sense. I even looked at whether optional lateral links could be adopted somehow, maybe off of a "saddle" added to or above the 901 or the transmission mounts, but it looks like an unnecessary complication and not sure the geometry would work out anyway? And I'm not sure the 914 suspension concept needs a rethink, though? It works well enough to have put these cars into the winner's circle for decades, and their handling is (rightly) legendary. Its execution, to a price, can be improved upon, however—just as with older 911s.

Anyone taking this on as a vendor needs to maximize market interest…and that's going to be for something that a) bolts on, b) doesn't require unibody mods, and c) is true to factory concepts and price sensitive (cap is somewhere around or a bit more than "the works" + 911 e-brakes on an old pair of 914 trailing arms).

I did the research on putting a Cayman rear suspension under a 914.

The track is about 6 inches wider. So you get 3 inches on each side. A different offset wheel (A Cayman wheel) would probably fit with no spacers under a narrow bodied car. For a flared car, just use a wheel with the correct offset.

The shock towers on the rear of a 914 lean forward, but the Cayman ones stand straight up (at least in the front/back reference plane). So you would have to remove the current shock towers and replace them with the ones from the Cayman chassis. The mounts points on the chassis would have to be removed from the Cayman donor, and welded in the correct location on the 914. The trailing arm mounts would have to be completely removed, and the mount for the front link added. From pictures, it looks like it would come out right where the trailing arm mounts are located, so maybe that could be salvaged. You would also need custom park brake cables, but those are not a big issue to get made.

If I did this, my car would have an advantage. I just remove the custom trans mount and support the trans with a jack stand. Then bolt the factory Cayman trans mounts to the trans, and bolt the other ends to the Cayman subframes. So now I would have references for the proper location of the chassis mounts.

It's a lot of chassis mods for something of unknown gains. How would it work with a stock 914 front suspension?? Would I need to go to coilovers and an RSR style suspension in the front to take advantage of it?

I have been thinking about this for years. For some reason, it intrigues me. But I think I am going to keep the stock 914 rear suspension for now. I have other things on my car I would like to finish before I even consider something of this magnitude.


Clay

Pete, PM sent.

You forgot the underscore in my user name, so I didn't get the notification.

Anyway, I do not remember who made the arms. I think it was on Porschephiles back in the 90s, and what I remember is:
- They made tubular trailing arms, not blade-style
- Adjustment was out at the wheel end
- They didn't sell, and were abandoned
- It was done at least a few years before I heard about them, so possibly in the 80s

That's it. Sorry I don't have any more information.


I'd be worried about the strength of blade-style arms. There's a lot of torsion going through the 914 arm, and a flat piece of metal will bend a lot in torsion. Multiple blades can deal with that to some extent, or a blade to carry the loads in one direction with an I-beam or a box to carry the rest. (Note that the 911 spring plate for the most part only carries the torsion bar loads. The cast arm carries the twisting loads and such.)

Sounds like this is a lot of work for little benefit, frankly.

--DD

Cayman/Boxster/996 wheels are only offset an additional inch, none of that will work as you think.

You need to narrow the subframe, which likely means fabbing a new steel frame which holds the susp arms, which would be built to fit the 914.

Sorry for forgetting the underscore, Dave!

Thanks for sharing what you remember. I had the sense the trailing arm project you mentioned was more recent and failed to find buyers. I suspect the market is quite different 30-40 years later—consider the number of six-figure 914 projects in recent years, or upgrades to four-piston calipers and/or 911-style e-brakes. This thread already has 3,100 views, so it would seem there's at least some interest.

As to work and cost, a pair of brand new arms that allow use of factory parts that didn't exist in the 1980s or early 1990s might end up less expensive than restoring and modifying 50yo trailing arms. People are already doing a lot of work for little benefit, building trailing arm jigs to reinforce, add 911 e-brakes, change the caliper mounts, and/or narrow 50yo trailing arms. Sounds like there are quite a few of those jigs out there, with most presumably built for just two arms. One friend suggests "about a day" to build the jigs, and one has to hope the arms used to build them aren't bent 45-50 years later. Going rate for the work above sounds like $800-2400, without making jigs.

So the critical question seems to be: Can a simple multi-blade, blade/rod, or even partially boxed arm that works with existing 914 bushings up front and mounts a modified or unmodified 986 wheel carrier at the back be engineered? That's well past my pay grade, but solving the torsional loads seems do-able. The result would leave 914 owners with long-term parts availability and choices (stock rubber, poly, or needle bearings, not to mention used or new 986 brakes, wheel bearings, e-brake parts, etc). Added clearance for a 215 or 225 rear tire with less pulling on the outer fender would be a nice upside for those who don't want M471 flares or don't want to spend $5,000-20,000 extra to put M471 flares on a "mild" six conversion with ~200 hp. Multiple lower mounting points for the rear damper might be interesting, as fine adjustment for ride height as seen on Rennline's steel 911 spring plates for $250/pair would be.

And even if steel is the obvious choice for new trailing arms due to cost, killing any weight advantage, lighter 986 calipers and an e-brake design that makes use of the interior of the brake "hat" would offer significant advantages. A two-piece rotor with an aluminum hat would take that savings even further.

Pete...

Modding the trailing arms for wider tires won't help when the trailing arm is at the same relative location as the inner fender wall.


Clay

Maybe. When I did the test fit with a 215/60 on a 7R, the brake line was the only point of interference. Relocating the hard line alone might would help, particularly as the outer fender is pulled and the 15x7R is spaced out (and the less the better), but I got the sense the arm will also need to be narrowed at least a few millimeters so the tire can move around—and likely even more so with a 225/50.

While the ability to more easily sneak a 215 or 225 into stock-ish rear fenders is an upside that may or may not justify a new trailing arm for some, the far more compelling upside is no longer having to fuse 911 wheel carriers/e-brakes/caliper mounts/etc to 50yo trailing arms. I've seen that go wrong, to the point it had to be done over, even with a good shop doing the work. New arms + 986 carriers may be cheaper, as well. Any further advantages—adjustability, weight, off-the-shelf availability, etc—would be just that.

I can see a market for a good alternative to modded/restored trailing arms, no matter what sort of 914 hot rod someone is building—mild or wild. I have a tougher time seeing much a market for a setup that requires new pickup points, cutting the chassis, welding, etc. or anything else that isn't reversible.

FYI
Boxsters use 914 rear bearings, thus the compatibility I inferenced.
911 e-brakes bolt on with a welded on tab to secure the shoes. Not complicated.

The wheel well is like 10" deep. If you are hitting arm before inner you have a camber issue.

I think you are focused on a problem only you have because you want to run 80s 911/944 spec (and 80s tech) balloon tires.
15" tires are what was made at the time. 16s were new and pricey. Today 18s are stock on just about everything.

Camber is within spec; it was set when the PMB arms went in and more recently checked again.

The section width for Avon and Pirelli 215/60R15 tires is listed at 8.7-8.8", while a 225/50R16 Michelin Pilot Sport 4S is listed at 9", so I'd be thrilled if there was something like 10" to play with. My test fit suggested it's closer to 9".

Adding 911 e-brakes doesn't concern me, but I've seen complications with adding tabs for 911 calipers that led to brake squeal. The remedy was a do-over. Having watched a friend deal with that after a good shop got it wrong, that is a consideration. 986 wheel carriers would eliminate that issue and make 986 four-piston Brembo calipers and drum-type parking brakes a bolt-on upgrade for a fraction of the price of 911 brakes plus 911 e-brakes, spot calipers, or RSR clamps. And unlike most caliper upgrades for the 914, which are 911 or 930 parts, 986 f/r calipers were sized and balanced for a mid-engined car. It's an idea worth exploring imo.





215/60R15
Avon CR6ZZ (vintage race/road rally available in three compounds)
Pirelli P6000 (N-spec summer)
Pirelli CN36 (N-spec w/period looks & modern technology)

215/55R15
Michelin TB 15 VHC Racing Tyre (Dry / Wet, road legal)

225/50R15
Pirelli P-Zero Trofeo R (R compound/summer)
Pirelli P Zero Asimmetrico (summer performance)
Pirelli Cinturato P7 N4 (period correct summer in modern construction/compound)
Toyo RA1 (R-compound track-day tire, retro looks)
Toyo R888R (R-compound track-day tire)
Yokohama Advan A052 (Extreme Performance Summer)

225/50R16
Michelin Pilot Sport 4 (Ultra-High Performance summer, O.E. 991/992)
Michelin Pilot Sport A/S (Ultra high-performance All-Season)
Pirelli Cinturato P7 N4 (High Performance Summer)
Pirelli P-Zero Trofeo (ultra high performance Summer)
Bridgestone Potenza S007A (Extreme Performance Summer)
Bridgestone Potenza RE-71R (Ultra high performance Summer)
Continental ExtremeContact Sport (Ultra High Performance)
Toyo Proxes RA1 (R compound track day/race tire)
Yokohama Advan Neova AD08 R (ultra-high performance summer)
Yokohama Advan A052 (Extreme Performance Summer)

Many/most of these are at the cutting edge of current tire tech, and some allow staggered sizing with 185, 195, or 205 fronts—and there are other summer tires, all-seasons, and near slicks not listed here.

So this is less about "80s balloon tires" or the idea I'm alone in wanting more tire without big flares—as others have snuck 215s or 225s into narrow 914s to varying degrees of success or failure. This is about charting a path that isn't going it alone and doesn't leave other 914 owners to do so. The keys to minimizing work on the outer fender (and all the ills it brings) appear to be wheel offset (15x7R or custom 16x7~) and inner fender/trailing arm clearance. My goal was to stoke discussion around a sensible, repeatable path to the best tires and brakes that will fit under a narrow 914 with the prospect of long availability for consumables. And maybe a trailing arm that offers benefits to any modified 914, including one with big flares.

"All" that's missing is an arm between the 914's pickup points and a pair of (modified?) 986 carriers. Can such an arm be reasonably engineered? I don't know, but I think it's a fair question to ask in a 914 forum…

Some of us really dig the look of fat vintage rubber. The trick is to stuff it into the wheel wells without having to pull the quarters. Or pulling them just enough to gain clearance. I like the narrow cars. I have a couple in storage that I hope to revive with the retro track day look. KISS.

Some of us really dig the look of fat vintage rubber. The trick is to stuff it into the wheel wells without having to pull the quarters. Or pulling them just enough to gain clearance. I like the narrow cars. I have a couple in storage that I hope to revive with the retro track day look. KISS.

Yeah, there's the aesthetics too. I ran 205/55R15s for a long time but have come to like the look of period correct enough performance tires on narrow and M471 cars. If space and budget permitted it, I'd probably have one of each, but I just have one, so I need to make the best of what I've got.

Chris' snark prompted me to take a fresh look at what's available, and I am actually shocked how many great 15- and 16-inch performance tires are available in 215 and 225 widths right now. Things have really changed in this regard.

You can see the tire rubbing on the inner wheelhouse in the pic below, but it does not look like it hits the trailing arm.

Click to view attachment


Maybe it's set up with a lot of negative camber and hitting the bump stop Hard?