ninefiveone

Here's the background:

'86 951 with M030 sway bars front and rear. New Koni Yellows all around. Stock springs.

I recently switched from street tires to DOT R-compound Michelin Pilot Sport Cups. It's been a nice improvement at the track although they are exceptionally finnicky about tire pressures.

The side effect seems to be sway bar issues. Admittedly I'm cornering quite a bit harder on the track meats but maybe someone can help me understand why I'm beating up the front sway bar so much.

First I snapped one of the center drop brackets at Watkins Glen. Replaced both with new 968 brackets.

Now I've shredded both of the main sway bar bushings at Pocono. They're both stretched about 3 inches from their proper positions in the central drop brackets.

I'm also now getting a clunk from the front suspension in right hand corners at the limit. I'm hoping it's the result of those shredded bushings but fear it could be a-arm bushings or worse, ball joint.

I've tracked this car for nearly three years on street tires with zero problems of this type. I can understand track tires putting greater stresses on parts but given the location of the sway bar and how I imagine forces should be acting on it, I don't understand why sway bar bushings are moving out of position the way they are.

Thoughts?

Water944t

If your bushings got any oil on them, they are certainly toast. Not a hard or expensive repair.

Rich Sandor

Are you leaking PS fluid or oil? at all? even a little amount can cause the bushings to swell, move, and thus get cut up.

Has your car ever been hit? If the front of the chassis has been hit, like my car, and is not 100% aligned, it can cause the sway bar mounts to be off centre, and put the wrong kind of stresses on the bar, trying to offset the whole sway bar.

Was the sway bar mounted correctly? I remember hearing something about being able to mount it upside down, or mounting it while the suspension is compressed.. Not sure.. I followed the book when doing mine..

Have you considered Delrin bushings? It's significantly harder to shred plastic compared to rubber!

Let me know what you find out..

Oddjob

Sounds like something is wrong. Far too many track cars running M030 bars w/o problems like that.

Ive seen hard tracked cars crack and deform the body frame rails at the center bracket upper mounting point (make sure those M8 bolts are tight). Ive also seen cars that the ends of the sway bar pop out of the control arm mounting link (w/o the C-Clip on the 968 M030 bar). And of course the bushings will erode over time (years) on cars that drip a lot of oil on the sway bar.

Has the car ever been hit in the front? Something could be out of whack.

How are the rubber block bushings on the end drop link mount on the control arms? It seems the bar assembly is moving around too much.

The clunk could be the sway bar shifting in the center brackets, but as a precaution check the ball joint (they also make a clunking noise when worn out).

Steve Lavigne

Sounds like not enough spring to me. I'm pretty sure the '86 951 has the lowest spring rates in the series. The bar is just working too damn hard and is wearing out the lowest strength parts.

ninefiveone

Thanks for the replies. In semi-chronological order...

-Bushings are fresh. I put in a fresh set with the new brackets so that should be solid.

-I'm not really worried about how hard the repair is to do. I've been in there at least three times now. What bothers me is that I keep having to go in there.

-The car's never been hit in the front and I've done this sway bar install a few times so I think I'm solid there as well.

Oddjob listed off a few of my symptoms. I have popped the c-clips right off the sway bar at track events and while I haven't deformed the frame rails where the brackets mount, I have broken one of the brackets at that spot before. Those bolts are well tightened, BTW. Note that none of this cropped up until the sport cups.

I've checked the bushings and tightness of the endlinks and everything seems proper. The endlinks are only threaded to a certain point and I'm sure the nut has been tightened to that point, but I do agree, it really seems the bar is moving around way too much.

I'm thinking Steve has nailed it on the head. Not enough spring. My guess is that I didn't have these problems with street tires because they simply don't generate the kind of grip I'm getting with the track tires now.

Oddjob is right, though. Plenty of track cars with M030 sways that aren't having my problem. But are they running stock spring rates?

If it really just comes down to stiffer springs, I may just dial back to street tires. If I head down the slippery slope of serious suspension upgrades, I really need to look into M030 spindles/hubs and other fundamentals first.

Dave in Chicago

Hey, is that Hugh from 2001 at Road America? If so, this picture may look familiar...

If so, we'll need to talk. I am perched on that slippery slope of buying a modified '86 951 to serve my growing HP appetite. If it's you, please drop me a note off-line at teamswanson@ameritech.net.

I'm heading back up to RA tomorrow for the Club Race & DE Weekend.

adrial

I was stupid enough to install the sway bar backwards, so I have to ask...

Are you sure its installed properly? Does it bolt up easily?

It is possible to bolt it up backwards, but it takes some effort.

Oddjob

Couple things on the spring rates:

Offhand I think the stock turbo springs are around 140 lbs/in. I ran a turbo S with the stock M030 springs (about 160 lbs/in) and struts with added 968 M030 bars on the track with no problems. And I know several guys who have run that setup for years (with R compound tires). Its possible the softer springs are not balancing out the stiffer sway bar, but the M030 springs are not significantly stiffer than whats on a stock turbo, and I would be surprised if that is the sole cause of your problem.

If you do decide to upgrade your front springs, there are some very mild upgrades that do not require going to the M030 spindles, hubs, and late offset control arms. Just add the weltmeister 200 or 250 lbs/in progessive coils made for the standard strut perches.

Also, if you think the control arm links are tight, dont tighten them further. They are easy to tighten past the threads which damages the nut and chews up the threads when the nut is removed. I had to replace both links on my car because the previous owner had over tightened and stripped the threads on them.

ninefiveone

Hey, Dave! Yup, it's me. I'll drop you a line via email. That picture brings back memories!

Speaking of that picture, I had the M030 sway bar at that event 2 years ago. Ahh good times. No shredded bushings then!

Adrial, I'm sure the bar is installed right. I've done that install on my own car and a few other 951's so I'm pretty familiar with it. Besides, this is the same sway bar I've had for a couple years now.

Oddjob, I'm skeptical that a 20lb/in spring rate makes that much of a difference, too. I agree that there are simpler ways to get a stiffer spring rate but it seems that with the amount of track work I do, M030 spindles and hubs would be a good idea from a safety standpoint. There's no need to swap to late offset control arms, though. My intentions are to hang onto my 4 early offset 8X16 rims as long as possible. S4 brakes will fit under them if I do go with the M030 spindles.

It does seem like there's more to this though, right? I'll take a close look at the a-arm bushings and balljoints.

adrial

Standard turbo springs are 21.8 N/mm

Turbo S springs are 28.0 N/mm (both taken from the factory manuals)

That comes out to ~145 lb/in for the standard turbo and ~185 lb/in for the Turbo S.

Is a 40# difference enough...I dont know. I know it feels like a big difference riding in a Turbo S and then riding in a standard Turbo.

I do think there is something else at work here, though. I would imagine if there was an issue running 968 m030 bars up front on a turbo running R compounds, it would have been mentioned by now.

If you find everything in order, a solution you may want to look into is delrin bushings. But you will probably end up breaking brackets instead of rubber bushings then.

aka 951

If you stiffen the rates up significantly, invest in a strut brace if you don't have one already. I bent the strut towers on my 944 S with yellow konis, 275# springs, and a welt sway bar - on street tires w/cup wheels. After the strut brace, no more bending. I agree with the above re: sway bar bushings; sounds like you're asking the sway bar to do way to much work.

ninefiveone

Ah...so it's a 40# difference. It is a noticeable difference when you're driving or riding in an S vs. a regular 951. I suppose the proof is in the pictures. Pictures from my pocono event do show me leaned over quite hard. The inside front tire is basically skipping along on the inside tread.

http://members.rennlist.com/ninefiveone/pocono.zip

I've also got the KLA strut bar helping to keep the front end stiff so perhaps that also contributes to an odd combination of stiff (m030 sway bar, strut bar) and not so stiff (springs).

So how many people are running full interiored 951's with stock suspension, M030 sways and track meats? I haven't paid close attention but I do notice that the 951's I see at the track with track meats generally have more done to their suspensions than I do.

Oddjob

28N/mm works out to 160lb/in
21.8N/mm is 125lb/in

I used 1N = 0.225 lbf, 1mm = .0394in, double check my math.

I thought the stock turbo had a spring rate in between 21.8 and the 28, but apparently not.

So the Turbo S springs are about a 28% increase over the stock turbo springs. That could be significant, but I would still look for something else to be the problem first.

Correct me if Im wrong (I don’t have an 86), but if you put on M030 spindles and hubs, brakes and rotors on an 86, you need to put the 87+ control arms on too and run the later offset wheels. 86 control arms are shorter than the later models, and the rotor hats, hubs and spindles are designed for the 23.5mm (?) wheel offset. You can add the Turbo S calipers and rotors with adaptors, but you cant mix the other components, its all or none.

If youre concerned about the condition of your current spindles, have them magnafluxed to inspect for fatigue/stress cracks. M030 spindles are not a larger diameter (stronger) than non M030 spindles (87 and newer), just the knuckle is different to mount the larger calipers (bolt pattern). Do 86 and older cars have a smaller diameter spindle?

ninefiveone

'86 cars do have a weaker spindle. That's why I've been planning an upgrade at some point. You're right, I could just use 87+ spindles and hubs but since I do plan on making more power in the future, M030's would set me up a tad better for bigger brakes, later on.

You can put M030 or 87+ spindles, hubs, brakes and rotors on an '86 without changing the control arms. The offset difference is entirely in the control arm. What is affected is the range of camber you can achieve. The solution is to go with camber plates to regain the lost range in camber adjustment.

I'm not worried about my spindles just yet although it is good practice to magnaflux when one tracks the car often. More and more it's looking like there's some suspension work in my future.

28% is somewhat significant but I will continue to look for other causes of my suicidal sway bar bushings.