Zeppelin

The only thing is that by putting narrower tires on the rear you may be reducing some of the understeer but the car will not be any faster through the corner or around the track! You still have the same load on the front tire(same tire size) and the car will still understeer with front end grip being the limiting factor in your corner speed.

The only way to increase the corner speed is to increase front end grip or transfer the load off the front to the rear of the car. Front end grip is at a maximum with a 245 front tire and 2 degrees of camber(anything more will eat the inside of the tire) So the only thing left is to reduce the front tires workload by transferrring the weight to the rear of the car. This can only be done with the following:

A) Stiffer rear springs (won't work on a daily driver)
B) Stiffer rear swaybar ( No one makes a big enough one)
C) Softer front springs ( will bottom out)
D) Softer front swaybar

If you want this car to handle you will have to experiment on your own. There are no aftermarket parts available to give you what you want.

Fifth Ring

Or...

E) Go with a lighter battery (relatively easy to do).

F) Relocate your battery to the rear of the car (tougher but feasible).

In the end, a "neutral" car may be impossible to create without vastly altering the car's day-to-day performance. But that's no reason to despair. There are lots of very good, high performance cars, with worse weight distribution, but with solid track manners (VW GTI, Audi RS4, Audi S4).

dsC32

I agree. You first have to get the front tires at a proper operating pressure to give best traction for turn-in, then adjust the rears to dial out as much understeer as possible without going too low that the rears chunck out or roll over. I don't know the type of tires you are using but the Hoosiers seem to run best about 44-45 psi hot. I run the rears about 3 pounds less than the fronts, with the 4 wheels sized same as stock rears, and all 4 tires are 245/35-18. Different tires/wheels will require different pressure settings. We are just trying to get the thing to work on the track, have fun, and drive home. It ain't no race car. With negative camber bolts I can get at most -1.5 degrees of camber. Would love to get another degree.

CynCarvin32

might be wishful thinking to think that moving a 30-40 lb batt to the trunk will make a car prone to plowing corner better.

It nees different wheels, tires, allignment specs upgraded, stiffer everything etc etc etc. At that point it might think about turning.

I have driven C32's in all states of tune and anything near stock is just slow as heck at the track. I had a guy claim he was able to run a crazy fast lap in his c32 stock and he came out to prove me wrong. Funny thing was he came out with 4 pt harnesses, H&R coilovers, and H&R bars... yet he still was 2-3 seconds slower than his claimed lap time and slower than me. Oh he also ran off in turn 1 at 90 mph and almost made me wet my pants as i happened to be there for a ride along. Dumb idea....

The understeer can be reduced and the car feels nice around 2.5 - 3 degrees of negative camber but we still need to fine to the settings further as we now have excessive inside wear and none on the outside. Something is off... either the car is set to stiff, has too much caster (which could be at 12+ degrees) or some other item we have not come across. Most road racing cars have 2.5-3 degrees of negative camber and great tire wear across the tire. This understeer happy car could be no different.

dsC32

There is a big difference between the handling of my C32 and my C55 on the track. I believe it is partially due to the 18 inch wheels on the C55, which use tires with lower sidewall, with the result that the C55 turns in much better than the with the 17s on the C32. I also "think" the suspension may be a little tighter. Someone said that the front suspension is different on the C55 due to the CLK clip on the front to accomodate the V8 engine, i.e., it has the CLK55 suspension. Also, there is an improvement in handling because of the 4 18x9.5 inch BBS wheels on my C55, whereas I ran stock 17 wheels (staggared) on the C32. That change alone makes it hard to compare. If we could get the negative camber you are suggesting it would be great. With very slight modifications at the strut tower on BMWs, camber can be adjusted for track, and set back before driving home.

speedybenz

I know this sounds wrong but adding a larger frt swaybar will help control and stiffen the frt roll couple and keep your camber challanged frt strut C55 and C32 to roll less and keep the frt tires flatter to the pavement resulting in less understeer. It certainly works on my C43

spr

Adding a front sway doesn't reduce the front understeer unless you are softening the front sway. The effect you might find is that it effectively makes the spring rates a little stiffer only when the bar is torqued. This is likely what you notice. If you go over a bump straight or if both wheels take equal force of compression, it will not have that effect as the bar will be giving equal force to each side.

DSC, how did you fit 9.5" all around??? I was told that the most you could go in the front was 8.5 with 245 and anymore than that you're rubbing. Are you sure you don't have 8.5 all around? That seems to be pretty common.

I obtained a set of the negative camber/ aka crash bolts from the dealer yesterday. I was going to install them however they evidently change the toe and I do not have a toe guage at my house but with the race stuff at my fathers in LA. Of course I could use a tape measure but I much prefer the hunter machine

I also am going to wait for the machine as I want to take measurements before and after to settle how much the bolts give you. It is unclear whether they give 40 minutes or 20.

m3_eater

My apologies in advance for supporting a tangent to the thread...

If any C32 owner is viewing this thread and is considering a Quaife LSD, contact me privately or stay tuned to the W203 forum for more information as there is an issue (solvable but expensive) with earlier models of C32 that may make the Quaife too expensive to be worth it. C55s and later-model C32s do not have the problem.

speedybenz

spr,

I hate to say this but you are wrong to think that your already soft C32 or C55 will have less understeer by going to a softer frt swaybar, or softer Springs.

To reduce understeer you have to keep the tires flat to the pavement and by stiffening the front of the car you reduce the roll and keep your tires flatter.

Compare the pic of the C32 in this thread to the pic of my C43 with a 32mm front swaybar, 19mm rear bar and 700lb/in spring in the rear vs. 950lb/in in the front and look at the differnce in the camber of the tires and the amount of roll in each car. By the way that is a Lotus Elise behind me.

Jeff

dmatre

It is correct that in general, softening the front of the car (relative to the rear) will reduce the understeer/increase oversteer.

A good book on the subject is Engineer to Win by Carroll Smith.

While a car stiffer in front may be easier to drive fast (as it feels more stable), faster is measured by the clock (and isn't nearly as comfortable).

spr

I don't need others to confirm I'm right but I appreciate it dmate! You'd think I am personally assualting someone by actually making sure that others are not getting wrong information.

I personally always like to take the approach of stiffening the rear to reduce oversteer but you can of course do the same by softening the front. The main reason for the latter is for two reasons 1. maybe you cannot increase the rear that much and or the holes are maxed out etc. or 2. Because the increased stiffness of the swaybar does "relatively" increase the springs stiffness and changes the demand on the shock dampening again when the load is not even on that axle making it at times seem like the car is underdamped.

It's funny as there is such a flame war here when all of this information (correct) can be sought. Again, just because something is published (especially in magazines) doesn't mean its right, or course you would hope that it wouldn't be wrong!

I am just trying to gather information and help others gain insight and knowlewdge into correctly how to do things when the elicit and seek it.

ON a cool note, it appears that from speaking with another very knowledgable MB mechanic that the EUR alignment spec of the c55 is lower but doesn't use different components- curious!

It appears they just use different spring pads. This is GREAT as it means that you can swap in the same pad# e.g. height to obtain more camber and do so by factory spec and maintaining relative height balance.

I already got a set of the "crash" negative camber bolts but have not yet put them on as they require the toe to be realigned. However, after reading more about the EUR spec and with the other MB mechanic checking the WIS and noting that there is no difference in springs or shocks (other than the optional suspension of the performance studio) it would seem that changing the pads to the EUR #'s would be the ticket as well as maybe adding 8.5 rears to the front and the crash bolts for a bit more negative camber 20-40 minutes!

Fifth Ring

Unless I was misled (or unless the C32 and C55 are different in this regard) I believe spring pads are only used on the rear of the car. I discussed this with my dealer's tech and they even put the car up on a lift (I was not there) to confirm that there were no spacer pads in the front. I sure wish there were.

As you note, if your ride height is different, and the springs are the same, there has to be another explanation. (C32 rides higher than C55 up front.) I wonder if Euro-spec C32 springs are a different part number from US-spec.

spr

Hmm. Dunno I just noted that he stated that the springs and shocks were the same part #'s in the Wis US v. Eur but that the EUR spec alignment was significantly different. I remember that he said the pads were different. That would make sense that there woudln't be a pad in the front as it runs a strut, however maybe it uses a different upper mount that allows it to mount the strut higher?? I dunno. I will ask him more about the actual EUR alignment sepcs to make sure they're not just toe or something!

speedybenz

Yes I have Carrol Smiths Books and he is refering to a car that is already pretty close to being balanced and race ready. Not a street car with soft suspension and poor balance.

If you look at my avatar you can see I used to race motorcycles with AFM and AMA, Sears Pt. Laguna, Daytona, Thunderhill( outright lap record holder in 1999), Buttonwillow. AFM #1 in 1999 and 2000

Anyhow I know that the only thing I am concerned about at the track is lap times


While you may not believe what I have said, you jmust cannot have a car roll off the outer edge of it's fronts tires and expect to have any sort of grip.

I am also not trying to make a federal case about this, but you are just going in the wrong direction, sorry.

Zeppelin

I have W203 swaybars stacked in my garage like firewood. I picked up used ones from people who have upgraded swaybars to aftermarket ones. I have fronts and rears ranging from c240 versions, C32 versions and aftermarket versions. I have tried them all. The big front bar does work better initially, but I soon found out that it does not matter how big you go on a C32 in the front it will still understeer. Now that I have a near big enough rear bar on the car I found that the stock C32(22mm) front bar works better than the H&R(24mm) bar. I will eventually have an even bigger rear bar made to dial out the last of the understeer and maybe be able to put the H&R front back on if I go too far with the rear bar size.

Every car is different and the C43 is a much more nuetral car than the C32 and will require different soutions to suspension tuning.

spr

Just because a street car has "softer" suspension doesn't change the way suspensions work whether it be on a race car or a street car. Stiffening the rear bar reduces understeer. STiffening the front bar reduces oversteer. PERIOD. Furhtermore what does motorcycle racing have to do with anything? Motorcyles don't have swaybars. LOL!

dmatre

I'm not questioning your setup, or your driving. The way that you've got your car set up is most likely the best way that you can (I can't imagine that you would set it up to be slower than it could be).

BUT, given your setup, if you go to a smaller diameter front bar, or a larger diameter rear bar, you will certainly find the car more biased toward oversteer/less biased toward understeer.

This is the only point of my post.

No need to get into an internet fight here. We all come here to share info/experience, and to make our cars faster/quicker/better looking/etc. If there's conflicting information here, so be it. The simplest way to sort out the conflicting info is to make a change. If you're faster after the change, then you're going in the right direction. If you're slower after the change, then you're headed in the wrong direction.

Keep on driving. . .

spr

Well put.

Dknowz

Do you have any pictures? My c55 is due for a suspension upgrade.

kent426

Hate to say it but adding tire pressure to the rear increases rear grip making understeer worse. Use KMAC front bushings or SPC camber bolts to get 1.75 neg camber and balance out the tire pressure and you will have an oversteering monster.

kent426

Guys, I am sorry but there is some pretty horrible advice on this thread. For low dollars you can dramatically improve track handling of the car with changing the camber on the font, set the toe to zero both front and rear as well. With SPC and alignment, you can dial out understeer for about $300. I run 235/275 tire combo and I can't get enough rear tire if I take out my spare tire at the track.

Ok, here is some counter intuitive advice but if you get AutoCross Speed Secrets from Ross Bently, stiffening the rear bar or reducing rear tire pressure will induce oversteer, reducing the rear tire pressure allows more tire rolls to the outside. I tend to run 35 PSI at all four and adjust based on the course.