caster problem

NCS2cab · 02-08-2006, 03:38 PM

I've been searching the board for some help on my alignment problem. I'm a newbie to this forum, but I know to look first then ask! (but then I accidentally posted in the 911 section - duh)

Anyhow, I recently put 996 wheels (BBS-made Sport Classic pattern) on my '90 944S2 cab - what a pain! The wheels wouldn't clear the bearing housings, so I bought 15mm spacers. They didn't clear either (?!) so I machined out the flanges to clear, and finally got the wheels on the car.

Now, I'm all over the road, tramlining like crazy - so it's off to the alignment shop. Toe was out - fixed that, camber was in spec, but caster was low - 2.0 deg - on the driver's side. The factory adjustment won't correct it...now what? The toe fix helped a little, but why can't the caster be increased to spec (2.25 to 3.0 deg)?

Britwrench · 02-08-2006, 04:53 PM

Did it tramline before you had the wheels changed? Probably it might have a little but changing wheels to both a different offset and size, particularly wider tires, make the car more sensitve to road surfaces.

If the caster can't be bought back into spec, then something is bent. As the toe was out I'd suspect it has been crashed at some point and a suspension part was bent. 0.25 of a degree out of spec won't make all that much difference, but the new wheels probably will. Put the old ones back on and compare. And adding spacers and machining flanges (of the wheel?) will change front steering geometry. as the wheel ends up in the wrong postion.

There are a multitude of 996 wheels, even with the same name, so saying "996 wheels and Sport Classic" doesn't give the size, offset or tire sizes to offer any further information.

NCS2cab · 02-08-2006, 05:18 PM

The car doesn't appear to have been crashed - especially underneath. There was zero tramlining with the original manhole cover 16" wheels. The 996 wheels are 18x7.5, 53mm offset, running Pirelli PZero Asimmetrico 205/40-18 - the original tires from the donor car and in great shape. They are made by BBS, but have Porsche p/n's. They are either 2 or 3-piece, with a mesh face (painted) and machined lip. Rears are 10", also 53mm offset, 265/35-18 tires.

The spacers are from Vertex (darn nice guys!) and are 15mm. They look like most of the other hub-centric spacers on the market, and bolt on. The wheels mount to studs mounted on the spacers. Due to the huge bearing covers on the hubs, the spacers would only get within about 10mm of seating. Therefore, I had the bores machined out to 67mm, which would seat after a bit of Dremel work to the step on the hub's bearing cover.

No one I've talked to so far can tell me why the hubs are such on this car that even the spacers wouldn't slide on. It is a low mile (67k) stock S2 without M030. I even tried removing the dust cap on one of the hubs - the wheel went on to the point that the bearing housing was flush with the outer wheel face (center cap off).

All of this is simply background - I just want to know how to fix the tramlining without giving up on these wheels - there are no rubbing issues, and everything fits under the fenders perfectly. Help....

NCS2cab · 02-10-2006, 07:45 PM

anybody that can help me get this fixed will be automatically upgraded to hero status...car looks great now, but its wearing me out to/from work trying to keep it straight....see my 1st 2 posts...

ae1969 · 08:54 PM

Camber/Caster plates....

Paragon has a couple of options...........

I am sure the suspension guys looked but the caster blocks on these cars sometimes look fine but the rubber deteriorates BADLY.

Britwrench · 02-11-2006, 07:19 AM

If it doesn't do it with the original wheels and tires, then the new ones are causing the geometry problem.

ae1969 · 02-11-2006, 07:22 AM

The other thing I remembered is that you do need 968 casters on wheels that are 18+. Although the tech bulletins don't recommend anything over 17 as I recall ....

NCS2cab · 02-11-2006, 09:52 AM

do you mean the adjustment blocks at the rearmost mounting point? That's where the alignment guy was trying to make the adjustment...

What about putting on hubs/spindles that would allow me to get rid of the spacers altogether? Know of any ones that will fit but not force me to change the brake setup? I want M030 front brakes, but can't really afford the swap right now....

ae1969 · 02-11-2006, 10:42 AM

Yup those are the caster blocks.

New hubs and spindles may help buy I am pretty sure you are still limited by the amount of caster adjustment available by the stock block.

Britwrench · 02-11-2006, 12:25 PM

The later caster blocks are used becasuse the older ones have a problem with wider wheels. It doesn't alter the caster angle.

I still think the new wheels have altered the "negative scrub radius" used by the later struts.

SoCal Driver · SoCal Driver's Garage

How was the alignment shop trying to set the castor? Moving the adjustment arm or trying to reposition the whole block?

Britwrench · 02-11-2006, 03:15 PM

The 944 with aluminum arms are adjusted by the eccentric on the castor block.

The eccentric bolt, 951 341 431 02...is from 85/2 - 95

The castor bush varies..
up to 89 951 341 023 30 with MO30 or Turbo S I think it's to 91 really
951 341 023 00 stock

968 951 341 023 01 for all versions

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by Britwrench
The 944 with aluminum arms are adjusted by the eccentric on the castor block.

Exactly why I asked. Might have tried to move the whole block not even noticing the eccentric adjustment.

NCS2cab · 02-12-2006, 02:01 PM

The guy was trying to set ti by loosening the two bolts and moving the arm's bushing in the block. I specifically asked him about an eccentric - he said there wasn't one...I'm beginning to wonder if he knows what he's doing.

I just looked - between the control arm and the block is a metal tang mounted on the control arm bolt - is that the eccentric adjuster? If it is, then it's official - the guy's an idiot! He claims to have worked at the Porsche/Audi/VW dealer....