FredR

Now that I have completed most of my work programme it was now time to tackle the problem with the rear camber adjustment pocket.

This all started when I was having trouble getting a rear camber setting I wanted. The problem seems to stem from two issues- the first being compressive distortion of the upper link [dog bone] bushes that I have as of yesterday resolved. The other contributor is the damage to the shoulders of the camber adjustment pocket. I am not sure when this damage occurred but I suspect it was prior to my owners ship [over 10 yeas ago] and possibly caused by inadequate tightening of the adjustment bolts.

The damage on both sides left a gap of two to three mm that the adjuster cannot go back to once the bolt has been turned and this can only be corrected by pushing the arm back- a pain.

A short while ago 928 Motorsports introduced an insert to help rectify this problem and I recently ordered a set from Carl and they arrived yesterday so today I set about trying to install them.

Superficially there does not appear to be too much to these items but in fact they appear to be a very nice precision piece of kit. the only slight problem I had with them was that because the bolt is such a snug fit in the slot, the edges need a chamfer to accommodate the shoulder of the bolt that I did not want to lay around with. 10 minutes with my Dremel and problem solved.

The bit I feared was the preparation of the rear cross member to accept the insert. I decided to tackle this using my Dremel to cut out the metal. The inboard shoulder is the one that is not damaged and I used that as a reference and tried to cut the face so that when the insert is in place the push point is the same as the stock finish. To do this I inverted the piece, aligned it as best and as square as I could and made an ink mark on both sides to tell me where my cutting limits were.

The trick with the Dremel is to take one's time and not push the cutting wheel too hard. I very carefully established an initial cut ensuring that the ink line remained visible. Once this was in place one simply works the cut until the depth is approximately to the required level. Once I had achieved this I then used the seating face the bolt sits on to help undercut the section to the cut line I had already made. To my amazement this went very well. I then did the other side and then worked the two lower corners- nothing needed for the top as that is flush. The cutting took me about an hour in total and I was delighted with the results. A little bit of minor trimming was needed and the insert sat nice and flush ready to be bolted back up.
Seems i have skills I never knew I had!

Hopefully the next insert will go well tomorrow and then I can box it all up. A really neat solution to what I perceive is probably a very common problem and all kudos to Carl for coming up with this simple but very effective piece of kit.

I would also add that my initial order seemed to go amiss with delivery being reported on the USPS tracking website and my courier stating nothing received. I reported this to Ms. Gretchen as there was a gap of about a week and my courier still denying its existence. Without any prompting from me, Indeed I asked Gretchen to hold back from taking any action, she nonetheless very kindly dispatched a replacement part at no cost to me. Needless to say the missing part turned up a few days later- probably got lost in the Black Friday deluge! A pretty stand up action- very much appreciated.

For those following this thread who have a similar problem I highly recommend you go down this path.

Rgds

Fred

Carl Fausett

Great job, Fred. Yes, there is no doubt that's why you could not get the same rear camber number side-to-side, those camber eccentric pockets of yours are some of the worse I have seen.

Good repair. It should hold its settings now!

Please post a finished pick of the camber pocket after its all assembled.

FredR

Carl,

Hopefully I can get some better shots in the daylight tomorrow as the light had faded by the time I finished the first one today. I will posts some pics of the finished assembly as well.

Maybe the problem has been accentuated by my wider rubber and my penchant for lateral acceleration!

I rather suspect one just does not notice the growth of the problem -although it cannot be seen on the photo of the damaged shoulder- in the flesh you can see how the shoulder has literally been compressed and the compressed indent had quite a noticeable surface bulge as a reaction to the compression.

Under use in the revamped condition I will monitor how it is performing and if I see any signs of future slippage I will pin it like you did- I rather feel that will not be necessary though.

Rgds

Fred

mark kibort

nice repair.. still wondering how this happened. again, ive never seen any movement in that adjuster area, and camber hasnt moved in 3 chassis in 15 years of racing, hard! (on big 335s and 320 slicks)
i wonder if its the alignment shop not tightening things down properly and then its able to move and wear down the adjuster area.
anyway, thats a great repair kit, similar to the water pump fix for the block. both should never happen if the original parts are working correctly .

FredR

Mark,

With hindsight I am pretty sure it was the alignment shop but I also have to put my hand up and say that I may have contributed to the problem.

The initial problem is that the main agents here do not have an alignment machine so initially they farmed out the work. Whether or not they checked the bolt torque is questionable- all I can say is that I had the camber problem from the day I purchased this car Just that in the first instance I did not know why. As we were setting up the car ready for the road [after fitting the engine], the mechanic I allow to work on my 928 showed me this problem on the shoulder of the cross arm. What has was alluding to was that when adjusting the camber the bolt would move off the inboard shoulder and could not return unless one slackened off the bolt completely and manually moved the arm so that with the bolt in the minimum camber position, the bolt was pushed hard into the inboard shoulder and then torqued uo- this left a gap to the outboard shoulder on both sides. Thus when we took the car to the alignment shop they did not touch rear camber- we simply measured what we had and it was minus 1.5 on one side and minus 1.7 on the other. I had no choice but to live with this whereas I actually wanted to run with 1.25 degrees to test the effect.

Initially I had wondered if running the car at the low end of ride height had something to do with this and indeed you confirmed you had no such problem running much lower ride height than me. The shoulder problem explained some of the problem but not all of it.

later on I fitted the 928 Motorsports lower frame brace and took the car to the Michelin depot for alignment ostensibly to reduce front camber to 2 degrees from the 3 it had been previously running. During the initial assessment we noticed the rear camber was now reading 2 degrees- durrgh. I had not intended to touch the rear but had to have a go at it and managed to reduce it a tad. However, by now the exhaust was fitted unlike at the main agents where the exhaust had not been fitted. This is where my mods kicked in. I have the Louie X-pipe, I have Bullet mufflers where the intermediate resonators used to be and an RMB- sounds great! The problem with the Bullet mufflers is that with them fitted one cannot use a torque wrench on the camber adjuster so the technician used an open ended wrench with a longer lever arm to increase the torque but in practice had no clue what the torque was. So with the possibility of too little torque and no shoulder to stop the bolt moving laterally was probably game set and match I suspect! Doubtless the thing moved and then induced ever more rear camber. Add that to my old heat aged rear rubber with no grip and it is not hard to see why the otherwise wonderful handling of my 928 slowly but surely went to pieces.

Hopefully by this time next week it will be a bad dream with my maintenance efforts and [hopefully] new rubber on board.

When I take the car for alignment I will simply let the car cool off and remove the exhaust and use my torque wrenches. I cannot fit them on the rear toe adjuster but then that is probably much less sensitive to load.

All part of life's rich tapestry!

Rgds

Fred

FredR

Carl,

Passenger side pocket as the bolt was being installed and bolted up. Then pics of the driver side that I cut out today but not yet bolted up. I may tidy the installation up a bit by grouting with two pack epoxy metal filler where I had to cut the bottom corners a bit tog et a flat surface but it does not really need such.

I tried to minimise metal removal and today's cut was even cleaner than yesterdays- both sitting nice and flush with no rocking.

A couple of more jobs to do and then off for alignment all being well.

Rgds

Fred

Herman K

This is the way to resolve this issue, however when I discovered the problem (8 years ago) I wasn't aware that Carl parts where available I did use a come along to pull across and get the proper alignment and after I tighten the bolt properly I never have had an issue since.

I do plan to install this mod at some point in time.

Nice job and description Fred

MainePorsche

Yes, good job Fred and thanks for bring this into the light.

mark kibort

is there room to rotate the eccentric in the incert? it looks like its maxed out in that one pic!

FredR

Mark,

The insert acts as a shoulder for the bolt- if you see the photo without the bolt but with the insert, you will see that the slot in the cross arm is parallel with the slot in the insert and the insert slot is a bit longer than the slot in the arm so basically the insert does not interfere as the bolt shaft "travels" laterally to increase or decrease the camber.

Now I am more or less back to the point where the eccentric bolt head is in permanent contact with both sides. The bolt itself has a travel of some 9mm from one extreme to the other. The pocket damage lost me some 3mm and the dog bone bushes about 2mm each end so no wonder I could not get the camber vaguely close to stock settings even if I wanted to.

Rgds

Fred

FredR

Herman,

Carl introduced this part a relatively short while ago. Once I knew I had a problem that needed resolving I was going to have something along these lines made at a local machine shop who does bits and pieces for me as needed at very reasonable pricing. As soon as I saw this mod it was game over- just had to have a set.

Your comment is interesting in that it suggests the shoulders may not be necessary to stop movement and that is a bit surprising to me- but they sure are needed to facilitate camber adjustment.

Rgds

Fred

mark kibort

again, great you were able to fix the pocket.. but as was said, i fyou tighten the eccentric properly, nothing rubs on anything. proof is on my car, runnng 335 slicks, and some of the hardest , turney tracks in the world. never had an issue. and still, after 15 years, and 100s of race days, nothing is worn in that area. camber still set at 2 degrees and could go to 1 if i wanted to convert the car back to street.

FredR

Well, set the camber at roughly half way across the adjustment range- this taking into consideration the revamped dog bones as well as the previously damaged shoulders. Figured that somewhere in this range is likely a good starting point to give something just over 1 degree of camber.

Took the 928 for a spin to settle the suspension and everything felt much grippier once more and that despite the age hardening of the rear tyres. After abut 20 miles the suspension is probably not totally settled but not too far off. Quick estimate of the total toe on the rear suggests about 0.4 degrees- great if is 0.2 both sides- still have to prove this] and the camber is approximately minus 1.4 degrees- more or less exactly where I want it.

It will be interesting to see what the alignment says it is but so far so good. So it seems the effort was worth it.

Rgds

Fred

mark kibort

if its total toe of .2dgrees you are fine as long as the wheel is straight. camber might be excessive , if you are not tracking the car. 1.2 might be a better number. I run 1.7, but im also a lot stiffer (less body roll) and very low. (lots of bump steer).
however, on street driving, I don't see that much inside wear, with DOTs do you probably will be ok. 928s are very easy on tires on the street.

those dog bone bushings are pretty tough.. my only failure was when one came apart, (no way to press it back in) so I bought a used one from Anderson. problem fixed. all my bushings are near 30 years old.... all of them.

FredR

Mark,

The total toe is roughly 0.4 degrees which is slightly less than the top end of the factory spec upper range [0.5 degrees]. This I expected to see assuming that the camber was reduced a bit as planned. I normally run about 0.15 degrees per side on the rear- I felt that 0.1 degrees per side results in a lack of grip driving out of tight corners or so I experienced in one of our autoX events.

When I hit the Hunter machine I intend to dial in 1.25 camber on the rear- a bit less than what I seem to have at the moment.

I agree with your observation that our cars are quite tame on tires. I have never seen any noticeably uneven wear on the rears with 1.5 degrees but then I do not run silly air pressures either.

I rather suspect your dog bone bushes will have taken a permanent, especially with your lateral loadings but as you run 1.7 camber you would probably not notice this. My bushes suggested a compression of 2mm either end if not more. Maybe our excessive heat plays a part in this.

Rgds

Fred