Autocross set-up help and the Roe s/c kicks a$$ at the autocross

[1TONY1]

I know Chuck...its not 140 mph but Allstate thanks me for staying below 40mph (and off the wall)

Anyway, Sunday I did my third autocross with the Roe s/c. I also have Kumhos on all four corners and shims removed from the front upper control arms. I have done two short courses and one medium size course. If you take the go-carts out of the picture, I have had FTD (fastest time of the day) at all three. Not only FTD but beating everyone by one second and excepting a few cars/carts beating everybody else by two seconds or more. A Viper is supposed to **** on these short courses (25 - 35 seconds) but it is kicking butt. I am doing ok but the car is working very well......but I know there is more left. Rear alignment ? Bigger swaybars ? Any suggestions ? Kumhos and bottom end torque rules !!

Bragging on: Here are a few comments from the Knoxville group about coming down to the Chattanooga autocross-----

"I just want to know 1 thing......What kind of a course did chatt have to let a Viper have the fastest time of the day?????"

REPLY: "That was a venom 500 supercharged viper with kumhos. Not your typical run of the mill viper that you see at an autocross. You coulda taken him though John. "

ANOTHER REPLY: "It was tighter than the last WB course by far and had one painful spot. That Viper was well set up and very well driven."

Anybody up for this Saturday at the Knoxville autocross ?

 

[Daffy Duck Viper]

Awesome. What fun. Sounds like the kind of racing I would enjoy.

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[onerareviper]

1TONY1,

Kind'a off-topic, but was hoping you could help. I will soon be installing the Roe SC with a few other bolt ons ('98 GTS) within the next couple weeks. I currently have stock 18' pilots. Is this combo going to be a losing battle with the stock pilot and 600++ RW Torque (I have 3.07's)? Does Kuhmo make an 18' yet, or is there a comparable tire produced (Toyo, etc...)? Is your paint taking a beating - due to stones, and any method to protect the paint (3m stuff)? Stock half-shaft sufficient with increase traction of Kuhmo's? How are they for aggressive street driving? The last thing I want big HP and no traction.

Sorry for all the questions. Congrats on the victory....

 

[Daffy Duck Viper]

By the way, just what is the proper spelling for these Kumho/Kuhmo tires? I've seen them spelt both ways, back and forth, in several different threads.

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[Chuck 98 RT/10]

C'mon Tony, I'm not gonna slam anyone for enjoying some G's in their Viper, unless it's Red5 calling folks out. But even he gets credit for having fun in his ride.

Great job, congrats. Vipers are tough to AutoX no matter what the mods. Keep on trac...er, I mean coning.

 

[ChrisGTS]

Congrats Tony. Sometime, I am going to have to get some instructions from you about how to take out and replace those sport shims.

 

[1TONY1]

Daffy: http://www.kumhotire.com/int/index.jsp


onerare: I had Kumhos on my car before the s/c but my guess is traction will be at a minumum since its marginal with a stock engine anyway. I wouldn't call it a losing battle though. For the street a 18" BFG drag radial would be nice, not for autocross or roadcourse. I don't think Kumho makes a 18" yet...could be wrong. Paint and inner wheel well is taking a beating, I am going to stop running the Kumhos on the front for daily driving. Stock shafts would probably be ok on the street or track (not dragstrip) if you get out of the throttle if it starts to wheel hop. I have heard that stock radials and wheel hop are tuff on the shafts. The first mod that I did was to get shafts but I knew I was headed to the dragstrip.

1TONY1,

Kind'a off-topic, but was hoping you could help. I will soon be installing the Roe SC with a few other bolt ons ('98 GTS) within the next couple weeks. I currently have stock 18' pilots. Is this combo going to be a losing battle with the stock pilot and 600++ RW Torque (I have 3.07's)? Does Kuhmo make an 18' yet, or is there a comparable tire produced (Toyo, etc...)? Is your paint taking a beating - due to stones, and any method to protect the paint (3m stuff)? Stock half-shaft sufficient with increase traction of Kuhmo's? How are they for aggressive street driving? The last thing I want big HP and no traction.

Sorry for all the questions. Congrats on the victory....

 

[onerareviper]

THANKS!

 

[Tom F&L GoR]

Tony, congrats. AX is more "car control" than "car".

 

[1TONY1]

Come on guys.....no suspension help ? Seems like some of the road course set up would apply ?????

Chris, the shims are easy and I think they help. You going to the Atlanta autocross 6/14 6/15 ?

 

[Jack B]

A couple of questions:

1. Which Kuhmo's are you using.

2. There seems to be a divided response to the sport shim removal. Give me a short comment on the following:

a. How long to remove or reinstall the shims. Does a lift help.

b. Can you leave them out without adjusting the toe-in,

c. Can you permanently leave them out.

d' What is the advantage of removing them.

3. Does autocrossing require a different alignment than a road course and is there a happy medium that would work for both and be a compromise on the street. I'm willing to give up a little on the street to gain a little for the track.

 

[ceieio]

I'd have to wander out to the garage for the details and at 5:30 AM I am too lazy to do it. I will therefore subject you to my memory (that even scares me!)

The procedure for removing the shims can be done on jack stands, but I imagine a lift would be easier due to:

You do need to change the toe in when you add or remove the shims, also outlined in the manual.

It is not recommended that you run without the shims permanently, the additional camber will quickly wear out the inside corners of your tires.

The advantage is a better tire plant on hard cornering loads as experienced on a track... not a lot of help on the street.

Disclaimer: All of the above is from the manual... all I have ever done is look at the shims, but have not (yet) so much as turned a bolt there!

 

[Chuck 98 RT/10]

3. Does autocrossing require a different alignment than a road course and is there a happy medium that would work for both and be a compromise on the street. I'm willing to give up a little on the street to gain a little for the track.

My camber is -2.2 front, toe out 1/8, -2 back.

This is too radical for the street. I do drive it once a week for a few miles though.

You might want to start off with 1.5 and work from there.

These numbers are top secret. This post will self-destruct in one minute.

 

[ChrisGTS]

Tony, I am going to a BMWCCA autocross tomorrow, I avoid the Atlanta ones because they're too crowded.

 

[1TONY1]

A couple of questions:

1. Which Kuhmo's are you using. V700

2. There seems to be a divided response to the sport shim removal. Give me a short comment on the following:

a. How long to remove or reinstall the shims. Does a lift help. After the first time (55,000 miles) I can have the tires off and on in 15 minutes. A straight extension won't work. I use a wobble extention. Can also use a wrench. 3/4" I think. No lift needed.

b. Can you leave them out without adjusting the toe-in, I will have to look at the manual, I have not changed my toe-in at all.

c. Can you permanently leave them out. Mine were out for 3000 miles and was wearing the tires unevenly. I am now taking them in and out unless there are back to back autocrosses then I will leave the in for the week......then it rains....like today

d' What is the advantage of removing them. better grip (they say...I believe)

3. Does autocrossing require a different alignment than a road course and is there a happy medium that would work for both and be a compromise on the street. I'm willing to give up a little on the street to gain a little for the track. My guess is there would be a mild change that woul work for all three. Road course would be more than autocross ???? Maybe some more guys (Jannie) will chime in.

 

[1TONY1]

Chris is there a web site for the BMWCCA autocross ? I found the web site Also...you taking your Viper ? Looks like the past autocrosses had about 7 non BMW cars.

 

[pdmracing]

I have been doing my own alignments for years at home. Longacre sells some toe plates for around 50$ or so or you can make your own from some hard wood. Every time you mess with one of the alignment settings , you must check all & adjust all. So if you pull the shims you must check your toe, which is very easy to do with some patience. There are many different gauges available but the plates are the easiest & the most accurate. If you are really serious bur a good camber gauge too. The shim removal will give you close to -2 +- depending on your initial settings & condition of your bushings ect. this is a good overall setting for track & autocross. On most road courses you want more neg camber on the left front. The need & affect of negative camber can be observed as such: picture your car taking a right hand turn. As the weight shifts to the left & body roll takes place, the tire leans to the left. With 0 camber(the tire flat on the ground stationary) it will pick up the inside part of the tire, reducing the contact patch. So with negative camber(the top of the tire leaning in toward the car) you are anticipating this body roll & weight shift so that when you need it the most, the tire is now "flat " on the ground taking advantage of a larger contact patch. This is an overly simple explanation of a very important modification. You can put in too much neg camber , but I wouldn't worry about that with just the shim removal. For example on my scca ITS car I run 3.25 - on the left front & 2.75- on the right front, Our SRT4 grand am neon runs -3 on the front & that all we can get. We have been told to run even more. You will notice a great improvement in handling but like anything there trade offs.Make sure you test after making these changes.

On the homemade toe plates. Metal is preferred , but I originally used a high quality hard wood. Make it at least as high as the wheel bearing & as long as the wheel & tire plus an inch on both sides. Make a 3/4 inch deep cut on each side if the board. this should be 1 .5 inch or so up from the bottom. It must be placed identically on each board. the board must NOT BE WARPED AT ALL. The slots are for a tape measure to fit in. Place the board firmly against the tire/wheel. Have a helper do the same thing on the other side. Using a tape measure , through the slots, take a measurement on the rear. lets say its 60.25 inches. now leaving the boards in place take a measurement on the front slots, lets say this is 60 inches. 60.25-60= .25 toe in. If the front is larger than the rear its toe out.I do this at least 3 times to make sure of accuracy. The pre made toe plates are great, but if you cant find them & want to do it today, this is a very accurate way to do this. I do all my own corner balancing & alignments in my home garage & recently set up a fellow club members car. After we were done, being the anal retentive type he brought it to a well known Race alignment shop in town. Much to his surprise , my backyard set up was right on. You too can do this with careful measurement & a level surface. I can scan in a diagram of what to do if you email me
Pete