7 replies to this topic

[Bill Kowalewski-Barrera]

Not sure if this is the exact right forum, but here goes.  My car is essentially 1.8 Spec (2000), running in Nasa TTE.  Similar to an SM, with no restrictor, no suspension restrictions (other than no pickup point relocation), and 15x9 wheels, with normal 205/50 Toyo RRs.

 

Since I am using 9 inch wide wheels, does anyone have an opinion on what camber I should be using?  My latest setup is 3 degrees in the front, and 2 degrees in the back.  I can pretty much dial in whatever camber I want.  I have run around 4 degrees in the back at times.  Tire temps don't seem to be telling me anything.

 

Thanks.

[Bench Racer]

Not sure if this is the exact right forum, but here goes.  My car is essentially 1.8 Spec (2000), running in Nasa TTE.  Similar to an SM, with no restrictor, no suspension restrictions (other than no pickup point relocation), and 15x9 wheels, with normal 205/50 Toyo RRs.

 

Since I am using 9 inch wide wheels, does anyone have an opinion on what camber I should be using?  My latest setup is 3 degrees in the front, and 2 degrees in the back.  I can pretty much dial in whatever camber I want.  I have run around 4 degrees in the back at times. 

 

Tire temps don't seem to be telling me anything.

 

Thanks.

It would be helpful if you posted your tire temps. What ever the temps, there is information with the temps.

[Mike Collins]

Boxers or briefs?  How do you drive?  My answer wont be the same for all drivers.  I need video and data.....

[Bill Kowalewski-Barrera]

Thanks for the replies.

 

Next time I'm out,  I'll get tire temps.  In the past, they were as expected, hotter on the inside, and linear to the outside.

 

How do I drive?  What kind of answer would you like?  Please give me some typical answer examples to the "how" question.  I like a balanced car.  I'm currently a mid-pack driver.

 

I'm looking for general advice like:  "since you are using such wide wheels, you can use much less camber", or "even with wide wheels,  the camber suggestions are the same as for 7" wide wheels".  Something like that.....

[Mike Collins]

Do you drive at full slip angle on a constantly loaded arc or do you rotate the car in under braking and drive in a linear fashion off the corner?

 

How do you brake?  Do you go to the brake pedal and have no mercy then modulate with your toe gradually increasing pressure?  Or do you steadily increase pressure to achieve threshold without big initial bite?

 

Do you drive a loose car or would you rather it be set up to push at the limit to let you know you are getting ready to over drive the car?

 

How do you do air pressure?  Are you Ron Popeil and you set it and forget it, or do you try to keep it in a certain range?  Are you using tire pressure to increase or decrease spring rate?

 

These are just some of the questions I would need answered to even begin to give you set up advice....

[Mike Collins]

PS...The wheels make no difference on the size of the contact patch.....

[davew]

PS...The wheels make no difference on the size of the contact patch.....

 

Wrong my friend.

 

With a proper size wheel, you will get a full flat tire contact. Lets say 7" for discussion.

 

A wider wheel may give you lack of contact in the middle area of the contact patch. potentially giving you two patches 3inches wide with an inch in between.

 

Contrarely, too narrow of a wheel may give a ballooning effect creating a narrower contact

 

Way too many variables for anyone to answer the question with any authority. that is why chassis tuning is an art and not a science.

 

Dave

[Mike Collins]

Wrong my friend.

 

With a proper size wheel, you will get a full flat tire contact. Lets say 7" for discussion.

 

A wider wheel may give you lack of contact in the middle area of the contact patch. potentially giving you two patches 3inches wide with an inch in between.

 

Contrarely, too narrow of a wheel may give a ballooning effect creating a narrower contact

 

Way too many variables for anyone to answer the question with any authority. that is why chassis tuning is an art and not a science.

 

Dave

 

 

You are correct...except the Toyo RR he is on is too large for our 7" rim anyway...probably fits better on an 8" and not that bad on a 9"...  With the stiffness of that sidewall it comes down to air pressure...