I've been reading up on lots of threads about the rear conversion, CV joints, etc. etc. I'm not 100% clear on everything, but more importantly I'm not exactly sure what I have...

A few years ago I picked up a roller that was in the early stages of a -6 conversion. The owner worked at a Porsche shop here in socal, and had put a 1987 SC front end on the car, and started to do the 5-lug rear conversion.

So what I have are a pair of trailing arms with some stuff installed. From what I can tell from the other threads, I have a 74+ hubcentric wheel flange, early 911 stub axles, and on one of the trailing arms, a partially complete 911 handbrake. The other trailing arm has the dust shield portion installed, but no shoes, etc. The stub axle flanges measure 100 mm across in total diameter (edge to edge).

Now for the questions:

1. There were several threads about spacers required for the hubcentric wheel flanges, but I couldn't figure out where these spacers are supposed to go. Second, is there a way I can tell if this setup has them or not?

2. I'm hoping to use the 944 CV joints, 914 axle, and 911 coarse splined output flanges. Based on what I have are there any issues?

3. Brakes. I currently have the A calipers on the front and stock 914 rear calipers. When I finish this rear 5-lug conversion I will have to choose between upgrading the rears to the V-calipers or moving my A calipers to the rear, and using Boxster calipers on the front. As far as I can tell, there is little to convince me to go with the V-caliper. A set of Boxster calipers is ~$300 off ebay, and I figure I should be able to make a set of adapters on my milling machine. The V-calipers are nearly $600 and offer no change in pad size on the rear. I realize that fora narrow bodied car, the setup I'm proposing is overkill, but if in the future I decide to flare, I'd have the brakes already done. I have a 165 HP Subaru motor, and I'm sitting at about 1900 lb right now, with some weight still to come off. So the question here is any suggestions/opinions?

4. If I do put the A calipers on the back, are they strictly bolt-on or will I need to modify anything?

-Tony

Here's my understanding of what the CV joint/axle stackup looks like. Is this correct, and where does this spacer that I mentioned go?

The spacer goes on the hub that the studs stick out of and the brake rotor and wheel bolt to . The spacer goes on the shaft that goes into the bearing, it is on the wheel side of the bearing and presses up against the inner bearing race. It has been figured out by earlier crafters that the thickness of the spacer should be 5mm and can be had probably from some of the folks here , I got a set from an outside entity and was disappointed that the QUALITY control dept was on break when the set I got was made- 5.07 mm going around the ring to 5.87mm on the other side. These spacer rings need to be a little more consistant as they press against the race and when the stub shaft is installed and tourqued down a certain amount of squish happens giving your bearing a preload similar to preloading the front bearings but is not adjustable because of the rear stub axle / hub setup, SO make sure that the spacer rings you get are uniform in thickness around the circumference to get the disired preload. Hope this helps ther are threads here about this particular subject.

Jaxdream

Is there a way for me to know if I have such a spacer installed? I'm not sure but if I have to tear this apart to inspect do I ruin the bearings? Is there a measurement I could take, say between the face of the flange and the brake mounting ears?

Without the spacer, does the system bolt together properly or would there be some slack somewhere?

Thanks for the description of the location.

-Tony

If there was no spacer the flange and the stub axle being bolted together would flop around, what I see from your pics is the backing plate being installed upside down from waht others have executed for a 911 e-brake setup , you didn't show pics of the top side of the arm. You seem to have all the parts required to convert to 5 lug with the hubcentric flange I feel is a plus ( opinions vary ) just might look into the e-brake setup and how you will get it operational. Hopfully someone may have an idea as to getting that done as I'm sure you have pondered this also. It would be a shame to dismantle it to turn the backing plate 180 deg to get the pull bowtie setup to the bottom of the trailingarm , also look to get a block setup that goes between the shoes that sits above the actuating hrdwre , this is a must for safety reasons as it stops the shoes from rotating around if used for an emergency brake in whcih case with no stop , the whole shebang spins with the disc / drum. There are sevaral threads on here for this setup , use search for 911 parking brake conversion.Good luck and like I said search is your friend.

Jaxdream

p.s YES if it is taken apart the bearing is usually destroyed hence my mention about it being a shame to take it apart to rotate the backing plate.

Depends on your setup. If you have the correct year 911 hub and stub axle combo, the bearing surface is the same as on a stock 914 and you won't need any spacers.
Andy

Hi Andy , look at the pics he posted , he has some arms he acquired with the 74+ hubs with the hubcentric ears and should already have the spacers installed , the ones you speak of are from the earlier than 74 911's . check out the pics of the arms .

Jaxdream

Hi Tony , one of your questions were about the calipers for the rear , your front A calipers won't fit , they have a 3.50 inch bolt spread and the 914 arm hasa 3.00 inch bolt spread.A lot of guys use the rear M type caliper ( up to 83) with the 20 mm thick rotor . The calipers require a 5mm spacer in between the caliper and the mounting ears on the 914 arm both bolts.This gives you the correct spacing for the caliper with pads over the 20 mm thick Vented rotor. This will give a Gr8 rear disc setup once you get the e-brake operational and there is no modification to the arms other than the 5mm spacer addition to bolt the calipers on. Some one on here is selling some M calipers ,IIRC correctly , check out the classifieds.
Look it over , post your thoughts.

I am in the process of doing the same as you , 5 lug conversion with 944 cv conversion.

Jaxdream

One word of caution in regards to the hub being able to "flop around" if the spacer wasn't installed, in a configuration where it should be.

It will not flop around due to the friction (inward and outward) on the inner race of the wheel bearing. Keep in mind that the hub needs to be pressed into place (plus removing it can do damage to the bearing).

Not having the spacer (where needed) will lead to problems due to the fact that the axle stub isn't adding compression to the bearing and the fact that under heavy side loading, the assembly could move outward.

Now this is all nit-picking on the wording "flop around", but I wouldn't want you to use that to indicate if the spacer is there or not. Even with the stub axle removed, the hub wouldn't flop around, unless the bearings were trashed.

You have no idea what the PO did. Take it apart to make sure.

(as a side note; don't tow your car with the (stub) axles removed.)

Wes

If my memory is correct (old age), Porsche went to a wider bearing when they went hub-centric. If I'm correct, all hub-centric flanges need spacers and perhaps they are installed already. If the flanges are flat face (like 69) no spacer is needed. Double check this info though.

jaxdream is correct on the spacers, if not properly machined, they cause problems. I machined some for a few members requesting them but several never sent payment so if you need a set PM me as I have two sets remaining.

Stop blocks are ESSENTIAL and must be welded on. There are numerous threads on this. Leave the old bearing in while you do the welding to prevent any distortion.

Numerous ways to do the axles. I used and prefer getting the proper length axles from Sway-a-Way but it cost a little more.

I hate it when people respond with "do a search" but in this case there are tons of threads with all the info and pics you need with plenty of different options for your budget.

Good luck, it's a worthy conversion.

Hi Tony,

You need to use a spacer to keep the rotor centered relative to the caliper. A spacer under the rotor will increase the track of the rear of the car. This can be a problem if your trying to squeeze 16 x 7 under the stock body work. If you space the caliper instead, you'll have an easier time fitting big meats under stock body work.

-Rob

oops,, different spacer you guys are talking about. My bad.

You're probably right. I don't recall the exact year when they went to the wider setup, but i'm pretty sure his '74 hubs need the spacers ...
Andy

Okay, so essentially the answer is that there is no way to know if the spacers are installed because the friction between the bearings and the stub axle and flanges would prevent any axial sliding (or what I was calling flop around). It sounds like there's nothing I can do besides sacrfice one set of bearings on one side to inspect. (Assuming that both sides were done the same way)

I will have to do more reading about the parking brake installation to see whether I hould have the cable enter at the top or the bottom and how to do this stop block.

Sounds like the M calipers for the rear are the way to go.

Thanks for all the info. Hopefully today I can get one side opened up and see how it was done. I'll post pics.

-Tony

Okay so I tore apart one trailing arm and I figured out a way to determine whether there is a spacer on the other side. I will measure the exposed threads on the stub axle on the other side, and if it comes up the same as on the side I tore apart, then I know there is a spacer.

I also discovered that the PO had a great idea with regards to the stopping plate for the parking brake. The pictures below illustrate that...

Another interesting detail on the parking brake is that instead of the expanding butterfly style, this one uses a compound lever (that's the best way I can figure out how to explain it) You pull on this tab that comes out and the shoes expand. In the end its the same effect, but with a different mechanism and does not seem to require the special cable that uses the sheath as part of the compression system.
(Is that confusing or what?)

So, back to the original purpose of tearing this apart... There is a spacer in the stackup, and it measures 4.92 mm thick and seems to be made of stainless steel (not magnetic) and has a nicely machined curved inner radius to fit against the radiused flange surface.

Patrick Motorsports' website says that there is an inner and outer spacer, and that both must be used. I have not seen anywhere else, mention of this. Anyone know about that?

-Tony

First picture showing the stop block installation

axle stuff

Now, while you have it apart, get some longer wheel studs ...
Andy

Tony you've got most of the parts. The stop block really should be welded on the arm casting as it would be a lot stronger than being on the backing plate. The block should be 40mm wide. The spreader you have looks like the 84 up 944 spreader and it will work from a angled cable. I call it a angled spreader. They are even on bmw's. There is a earlier one that is straight but very similiar. Then there is the one you referred to as the one (butterfly) that needs the sheath to work properly. That's where the backing plates came from (65-68 steel arm 911) You could actually make a short extension from the 914 cable to reach the spreader. You will need to rotate the cable mount that anchors the 914 cable. It may already have been done. The spacer you checked on was because the 911 bearing is wider than the 914 bearing and the flange is cut back more to allow for it. The stop block is part of the aluminum housing on the 944, not part of the backing plate. Your backing plates seem to be on right to me the spreader goes on the same side as the emer. brake cables. As yours appear to be. Brad on the club has pictures of a boxter eb assembly and it is also nearly identical. The shoes may be narrower though.

I think I remember the part about the inner spacer as being one that spaces the cv out to allow for the 911 axles that are "almost long enough".

Yep, the stop block needs to be welded to the arm. On a 911 it is cast in. Here is a picture of a cast 911 and my 914.

Click to view attachment
Click to view attachment
Click to view attachment

Tony, I am in the middle of collecting parts for this myself. I have tried to read and study every thread on this topic that I can find. To answer your question about the two spacers...

The one you have is for the hub-centric 911 hub. The other (what I think Patrick calls the "inner") is to be used if you use a 944 stub axle. If you have the 911 stub axle, you don't need the other spacer.

I have also been working on a 914 wiki article on this entire subject. The article is not done (missing some info and has some errors that needs to be cleaned up), but here is it's current state...

http://www.roadglue.com/wiki/index.php?tit...sion_conversion

One thing I want to do for the article is to create various diagrams like you have above. Along with the diagram, I want to include actual Porsche part numbers and where to source them (i.e. what year range of 911, 944, etc.)

Richard

I forgot to mention above, that I agree 100% with the above comments about the stop block. It should NOT be welded to the backing plate. It should be welded to the arm as shown in the photos above. People have been welding it to the backing plate and not having issues, but in my opinion it's a matter of time before someone runs into trouble with that setup.

Wow, Richard that is a GREAT resource!!! I think that many will find that very very useful, thanks for putting that together!

Now I wonder whether I have 944 or 911 stub axles. Is there a characteristic feature of each?

I will see to it that I get the stop block welded to the arm. It does make sense to have it attached there. I will have to see what angle the parking brake needs to be pulled by and give sufficient clearance for that. For access, I could weld on a block with tapped hole and have a bolt-in stop block. hmmm.

-Tony

Sorry about the mix up on the backing plate, I didn't catch the 914 e-brake holder tab in the 3rd pic of the first set, the pics didn't show the whole arm, Richard is on a very good track on the e-brake setup , there is a thread titled " A different way to hook up 911 e-brakes" it's a merged thread , should be able to search it out , check out the thread , you will get the I have three e-brake cabling spreader setups , 911 , 944 , 928 , I've worked all three around , I was going with the 928 spreader setup , but changed mind because it requires a stright pull from a cable similar to the 911, the 944 uses a pull by cable but at an angle from the backplate which I feel can be setup and executed a lot more easily than the other two because the cable would have to make a 90 deg bend going back to the hand brake lever , the 944 will just use a slightly angled setup , no need to 90 it and keep the cables out of the exhaust's way and not melt them .Richard is also right about the stop tab , it needs to be anchored to the casting , think about the drum brakes on American cars , the brake shoes butt up against the anchor pin that the springs attach to , this keeps the shoes from rotating around the hub in case of emergency handbrake pull ,Porscheses ( Porshi ??) are no different in this respect.You all the parts in the pics , except for calipers, caliper spacers ( don't forget them ) rotors, rotor holding screws, and pads. The studs should be decided upon depending on your wheel choice and the need or not to use wheel spacers . The stud thing should be done to the hubs before they are pressed into the bearings , unless you come up with a way to press them out and reinstall different length while the hub is mounted in the bearing.
Good luck , it can get crazy with the possibilities available ( $$$$$ )

Jaxdream

Yep, the reason it has worked is nobody has had a flow blown emergency. When the stop is welded to the sheetmetal and the brake is pulled hard at speed, the sheetmetal will wrap up like a pretzel. It works fine for holding your car in the driveway. Can you imagine stopping a 2000# car and expecting a piece of sheetmetal to take the force during an emergency stop? The thought scares me......

Yeah and when it does wrap up it will lock up and do a flat spin , like Tom Cruise in Top Gun , ziz ziz ziiz splat os something similarly baaaaddd !

I bought some aluminum rear trailing arm assemblies for a dune buggy application before I started working on the 914. One was bought as a 74 and the axle stub is flat where the cv bolts on. It uses the straight pull spreader. It also uses a narrower wheel. The second set was sold to me as turbo arms and they will hold a 11 inch wheel. They were sold as 84 year arms. They have the angle spreaders but the stub axle has a lip that goes over the edge of the cv. They are both 100mm axles. Also they both are hubcentric. AS a last resort if someone wants the latest parts the boxter has the same rear bearing as the 914 and the same eb parts as the 84 on 911/944. Brad has some pictures on a thread on the club forum. I also bought a stub axle assembly on ebay and the outercv is part of the axle stub, it was sold as a 944 stub. The stub axle spline and the cv outer case is one piece.

Tony;

Just a heads-up on using a "single pull" spreader (944 and BMW) and not a "push-pull" spreader (911 type).

As I understand it (standard disclaimer), the "single pull" spreaders function by bearing on a section of the backing plate or main hub.

It's simpler to talk about the straight pull ones but the function is the same with angle pull ones, so I'm just going to refer to the straight "single-pull" spreader.

As the cable pulls toward the center of the car, it pulls the spreader with it, toward the center of the car. What stops this (in the original car the parts are from) are the two bearing areas on the backing plate (or hub flange). If the backing plate wasn't there, the whole spreader assembly could move toward the center of the car. (this is partially resisted by the brake shoes, but that wasn't how it was designed or intended)

As the cable pulls the spreader and forces it against the backing plate, the spreader spreads.


So, what I'm getting at is that for you to use this type spreader (as intended by the factory), you also have to provide the bearing area for it. As with that 40mm wide spacer, I feel it should be welded to the hub.

Although I've read threads where people talk about using the angle "single pull" spreaders (and I like the idea!), I've yet seen anybody do it in a fashion that fully addresses all of the issues that are part of the factory design.

Wes

Click to view attachmentClick to view attachmentClick to view attachment[attachmentid=179
184]Click to view attachment
Click to view attachment
Top pic shows lft 944 spreader =angle pull , rgt 928 spreader slight straight/angle pull -requires a 90 deg bend in cable.
2nd pid shows 928 rear hub WITH steel shoe liner.
3rd pic shows liner - notice the factory welded on rubing block for the spreader.
5th pic shows where I layed the 928 liner on top of a early 911 shoe plate , marked to cut , did so , welded ( mig ) the 928 section onto the 911 section ( I am a very novice welder and this turned out Gr8 , but DA didn't take pics )
4th pic shows plate , shoes , spreader , cable mounted studing for the best angle to fab up a holder for the cable tube to mount the cable in, and fab the shoe stop / anchor tab.

Look these over , think what you want, maybe try it yourself.

944 spreader seems to be the ticket !!

Jaxdream

Good job!!!

It looks like you are covering all the bases.

Wes

This is excellent info! I will definitely put in the bearing plate for the angled 944 puller. I will also check to see if the PO had changed the location of the cable mount to account for the proper angle.


-Tony

Turns out the PO installed 'rubbing pads' on the brake frame...

Tony there is a chance that your backing plate is thicker than the early 911 backing plate. The one you have looks different from the 68 plate I have. If yours is thicker it may be alright. Those may be off of a boxter or later porsche. On the early 911 backing plate the opening is a lot bigger. At any rate I will just cut a piece of 1.5x1.5x .250 angleiron and fit it in the hole and let it do both jobs and weld it to the arm casting.

I have thought about it and I don't think the backing plate will twist up. I don't think it is that far out from the center. I think the tires will break loose first, but the block was always on the casting so thats where we should also put it.

Tony, just beware of the wiki info right now. I am still editing it and it probably has some incorrect info. I am hoping that I can get a handful of people to review it in the near future. I would hate to have someone spend $$$ on parts and then find they don't match up. But I will say it is probably mostly accurate and probably better than trying to peice together info from 20 different threads.

Jaxdream, I am also looking to do that same single/side pull spreader. My biggest issue yet (I still don't have all of the parts yet) is that the spreader fits into a notch on the shoes that doesn't exist on the 911 shoe. So it looks like you either have to use 944 shoes (which have the notch), but they mount on a slightly different style pin on the 944 backing plate. Or you have to notch the 911 shoes.

I am hoping to come to a parts combo that does not require modification to the consumable. Particularly trying to use the 944 shoes on the 911 backing plate.

Brads thread, boxter parts look a little familiar?
http://www.914club.com/bbs2/index.php?show...emergency+brake

Also I have both the 911 early shoes and the 944 versions and they are pretty much interchangeable on the backing plate, you might need to drill a coupla holes in the plate. In the case of the boxter, the shoes look narrower, But they are probably the right size for the lighter car.

Of course you still gotta do the support/rubbing block deal on the 914 casting. And on the boxter I don't think the backing plate will fit on the 914 casting but it might.

Charliew; (and others)

Just a word of caution; be careful about repeating stuff that Brad posts. (not to start a cross-site war!)

In that string he posts up a bunch of photos and aludes to the fact that it should work. If it was as straight forward as he would have you think, he would already be selling a kit.

The photos are worth looking at, but be careful on how you read what he says.

(for the record, I've been visiting both sites for about a year and a half and this is the first time I've done brad-bashing)

Wes V

I think the backing plate and the initial parts cost is their holdup. Not enough profit margin I'm sure. It could be Brads having too much fun racing right now too.

In Brad's defense, he's mostly focused on Boxster stuff right now. He loves 914s, but his priorities have recently shifted to making a living.

So the lack of a kit shouldn't infer anything regarding suitability. As I mentioned, BR just hasn't had the time to look at this in depth. I suspect (without having seen the pieces in person) that there will be enough advantages to the Boxster setup to make it a worthwhile pursuit. At the very least, it will be as functional as using any of the other, similarly designed (ie. 944), angle-pull spreaders.

On a slightly related topic, in the same thread, BR alluded to the Boxster's use of the 914 rear wheel bearing and suggested that as a result of this, the Boxster hubs and stubs would work in a 914 trailing arm.

Intriguing. Seductive, even. A new option to be added to the Rear Hub Conversion Parts Matrix? Anybody have any comments?

Boxster hubs on a 914 ?? That's GR8 - even more choices to choose from giving a wider field of parts availability to select to fab with

Jaxdream

If the Boxster uses the same wheel bearing, that means the OD and length of the mating surface on the hub is the same as the 914. Questions that remain are...

1. How far out is the hub mounting surface? Point being can you mount a rotor to it and still have it centered on the caliper correctly? If so, it might be an improvement over the 911 hub-centric hubs which require the custom 5mm spacer.

2. What is the spline count and diameter inside the hub? Or another way of saying this, what stub axle will work with that hub? Will only the Boxster stub axle work, or will others?

3. If only the Boxster stub axle works, then what is the CV joint situation with the Boxster stub axle?

Unless the Boxster stuff is cheaper than the current options, I am not sure what it will do to help. But I think it's something worth researching.

One last thing to mention. Brad may know something beyond what is listed in PET, but I just looked up the part number for the 986 and 987 and as far as I can tell they list a different part number for the bearing than they do for the 914. Frankly I would be suprised if they used the 914 bearing. They increased the bearing size in later cars (probably due to load from increased weight and performance of the newer cars) and I would not expect them to go backwards with the Boxster. But I don't know any more than what I can see in PET.

I've adapted the 944 e-brake spreader to my car and have been using it for 3 months now it it works great.

Click to view attachment

Craig: Nicely done! I think this is what mine will look like in theend. It looks like you left the cable end holder in the stock spot. Is the stop plate and 'rubbing pad' piece welded to the trailing arm? I can't quite tell from the picture.

Are those Boxster calipers?

Looks good Craig! I am also curious if you were able to leave the cable end mount in the stock place or not. I am assuming that is a stock 914 cable with a custom extension correct?

What a "teaser" photo!!

Looks like everything was addressed. I really like it.

How about more information and photos. Please don't tell me that you fab'd up the whole thing and didn't take photos.

Wes

It looks like he also used the angle iron to make the block and rubbing support. Great job.

According to BR, the Boxster and 914 bearings have identical dimensions, but the Boxster has a higher ball count, hence the different number.

Ok, drop in replacement, but not same bearing. Good info for me to use on the wiki article. Anyone checked the price yet of the 914 vs. Boxster bearings?

Boxster Bearings at Pelican Parts are $36.75 versus $77 for 914 bearings. I will probably use a Boxster bearing to replace my 914 bearing that I had to destroy in order to check if I had a spacer.

Tony use the junk bearing in the castings while you are welding on them to save ruining a good one.

BR indicated that the Boxster stub-axle and outboard CV are one piece and are non-serviceable.

Meaning that the Boxster stub-axle is a likely a dead-end for 914 driveline conversion, at least as far as a bolt-up solution is concerned.

I bought a 944 stub axle on ebay. When I got it, it had the outer part of a cv made onto the axle stub. You might be able to put the 914 cage and balls inside the cv/stub. I really don't know if it was a 944 or a boxter part. It was so cheap I thought I would see what it was.