drnick

mark, i wondered if this was the reason - i know youve advised me to lower the car before now. if i lower it much more i run into a few different problems on the street - the overhang at the front being the main one with the strosek front end. i was concerned that i might be missing something. i spoke to carl at 928 motorsports and he says that 1.5 isnt an unusual number for camber to max out at with a conservative ride height.

im installing the drysump soon which will involve taking down the crossmember so i will wait till after this and then check my corner balance and re-align.

mark kibort

I think 1.5 is fine. in fact, i wish i could take a little out of mine now that i have progressively lowering my car over the years. Now its 108mm and the camber is near 1.8 to 2 degrees.

Vlocity

I have also been experimenting with the alignment specs and ended up with the following, which may seem pretty strange, but just this alignment picked up almost 2 seconds at Mid Ohio.

I still steet drive the car and I run at Mid Ohio and Putnam Park which are predominately right turn tracks.

I am running 2.5 degrees camber on the left front and 2 degrees camber on the right front.
.08 degrees of toe and all of the caster that I can dial in on the front.

On the rear I am running 1.5 degrees of camber on the left rear and 1.2 degrees of camber on the right rear. Factory toe setting.

The reason I am running the different angles is that too much camber will slow down the turn in of the car as it has to overcome that aggressive angle while making a right turn. This made the turn in better and the car settles quicker for mid corner off. If you ever look at a Nascar set up you will notice that the right side carries a lot of camber while the left front has little if any......thats because they make nothing but left turns.

I had experimented with more camber in the rear and went as high as 2.5, but I am running the Eibach progressive spring and the feel I had was that I didn't have enough spring for the 2.5 so I went back down to 1.5 on the left with again a little less on the right so I have to fight the car less on turn in.

At 95% the car feels like it is on rails, and when you want to push that last 5% it is very predictable.

Mark's comments about toe I belive are correct. I change my alingnment to toe out for autocross, but I run just a little bit toe in for high speed track and get less trammeling.

My ride heights are set at front factory minimum and two turns above factory minimum in the rear.

I was able to get the 2.0 degrees to 3.0 degrees range by installing a set of S-4 upper control arms with two flat washers on each mounting bolt that goes through the fender well, over the top of my S-3 lower contol arms. Without the washers I wasn't able to get below about 2.75 degrees minimum camber.

I recently just put in a set of Carl's poly upper control bushings and really like those as well.

I know this is a little outside the box.....but it works for me on the two primary tracks that I run which have many more fast rights than left turns.

Regards,

Ken

mark kibort

you probably picked up 2 seconds for many other reasons than .5 degree of camber difference on the front and rear end

camber alows the outside tire to be flat ( the most amount of contact)if you have a lot of body roll . The inside tire ends up drooping and has little or no camber, but also has little or sometimes no contact with the ground
a lot of camber can hurt straight line breaking as you dont get the tires to make even contact , but trail braking can be more effective. All of this is dependant on a bunch of factors such as ride high, bump steer, tire pressure, compound, driver input, car attitude, speed, temp ,surface ....... on and on.

I dont know what your times were at Mid ohio, but the fastest T1 cars run 1:32(a few of these T1s ran with us at laguna ) and cars i run even with, run near 1:34 to 1:36. since a more street/stock-ish 928 can run about 4-5 seconds slower on dots, I would say if you are near 1:40, you are runnng where your car should run regardless of minor alignment settings.

The reason nascar uses different camber settings is for the reasons i mentioned above. the car is going through body roll on the bankings and the outside tire will need more camber to fight the positive camber movement of body roll, while the inside has the opposite happen. a softer car gets more roll and can need more camber to couteract it. your turn in will be most responsive when you match the camber to the suspension dynamics. mismatching the cambers is not usually done, as you would loose contact on the few opposite direction turns. That, could kill your times in those areas, and not really help handling in others. For nascar its more of a tire wear preventitive technique. they make NO right turns, so they set the camber to be flat under negative and neutral loading.

.5 degree is not going to matter much in handling, however it surely could hurt wear patterns. Certaninly it cant be responsible for 2 seconds a lap.

mk

Vlocity

Mark,

You are certainly entitled to your strong opionions.

You may recall the corner balance thread where I had posted a question concerning my corner weights and the fact that I was fighting the car during turn in and could not transistion well to get the power down mid corner off. I did make a two round adjustment up on the rear ride height and while I was brainstorming decided to try this adjustment to the alignment specs. I am quicker now than before and the car is easier to drive.

So, it may not be imperical testing by your standards.....but it is working for me.

Best regards,

Ken

mark kibort

you may have changed other things during the changes like caster or toe and didnt realize it. the only thing that can give or take 2 seconds a lap is 75hp or 1/4" of tow out!

If you post a video of your turn in issue before and after it certainly would show what you are talking about. I have a better feel between tire sets during the races and qualifying, and there is a pretty significant "feel" difference. however, the lap times are within .5 seconds. Also, you can see my video when i raced Pobst in my car with the new wing, the car was almost undriveable (BIG PUSH) . this is a HUGE handling issue, but i ran my fastest times. It wasnt fun, or manuverable in traffic, but i could still get around the track as good as when the car "felt" good. Things like camber effect tire wear more than handling, unless we are talking extreme circumstances. your 2 second per lap change was certainly due to something else besides .5 degreeo of camber change. a whole differnent 928, with 20 less HP and .5 degrees camber, with different gearing, less aero, and maybe a lesser driver, will only amount to about 1-2 seconds, with the camber being the least of the factors

mk

Carl Fausett

On our lowered 928, we get flat tire temps across the whole tire (315 front and 335 rear) at .5 deg neg camber front and rear. But, I am using a Front Lower Frame Brace to keep the forward frame rail from twisting.

Before I installed that, I ran about 1.5 degrees neg camber in the front to be happy.

Just a FYI

I am not certain that camber/caster/toe angles from Car A can be dropped on car B with good results. Too many variables: wheel width, offset, tire sidewall, aspect ratio, size, spring rate, sway bar rate, shock settings. Even track temp on the day you test the setup.

My suggestion: get a pyrometer and use it. Tune your suspension on your car with it and screw what everybody else says.

mark kibort

Ive raced 4 928s and they all have the same tire temps, temp spreads , handling characteristics, and were set up near the same. One had very mild camber and burned up the outside edge of the tires. I dont know if you can really see that much twisting, and we are seeing 1.5 gs on some corners during our races. its not the twisting, (and there would have to be a lot to do that much change) but the rolling of the body , and geometry of the suspension that determines the camber. I can guarantee, you take your suspension bolted car and run .5 degrees at sears or Laguna and run in the 1:49s or 1:40s respectively, and you would see outside tire wear, poor handling and high outside tire edge temps. Even anderson has run less camber recently and got better tire wear up front and in the rear. the rears are a good example of this as well. how much the body rolls, will determine the camber required. and, this changes on every turn, so thats why in racing, you need settings that fit the overall goal. (thats why tuning for nascar tracks are different than tuning for road courses, and different road courses can require different set ups too)

I put a camera on the front wheel and watched the camber change for high g loading smooth turns. there was nothing that indicated, at least visually, that there was any twist (or bend) in the chassis that would create a need for 1-2 degrees of camber. this would require about a .5" visual movement on the wheel, and it just doesnt seem to be seen.

nothing wrong with strengthening the chassis with that bar, and it provides some protection if the car isnt too low, but the effects are no where near equal to 1 degree of camber. im getting 5 " of body rolll on 1.5 g turns, just do the math. It would require about 1.5 to 2 degrees just to keep the tire flat based on our suspension geometry, and thats exactly what we are seeing.

I use a pyrometer on every single session and after 10 years of racing, thats a ton of data. Now, if you have real sticky tires and have a real stiff suspension, and only get 2" of drop from a 1.5g turn, .5 to 1 degree might work, but i would bet dollars to donuts that it would be sliding around like it was on snow.(ie too stiff suspension setting) The racing thing is an art form. Ill I can say is that I run 138.7 at Laguna and 1:47.9 at Sears (Infinion). If i thought for one moment that running .5 degrees would work, i would do it in a heart beat, and so would Anderson and Fan. You are goint to need to provide us more data to prove this is a viable racing modification. what you might have done is tighten up the chassis (which in itself is part of the compliance) and made the car stiffer, but left the springs at the same rate. kind of like what anderson has done with all the chassis cage bars. THEN, you need to go softer on the springs and bars to allow for equal compliance.
So many factors.
this video has some "fender/wheel" cam to show the motion ratio and movement of the wheel. you can look closely and see the camber changes
go to 1:45 min in to the video. (turn off the volume. I didnt have the motorsports case at this time so the sound is distorted )


http://youtube.com/watch?v=sjbhDRkGkcw&feature=related#

or go to 9:15 in the following video for additional fender cam shots

http://youtube.com/watch?v=Qe2wzz_7-eg

Make sure you watch it in "High quality mode"

mk