FD - Camber adjustment based on tire temps

[jkstill]

Some particulars on the car:

3rd gen - lowered to ~ 25.5" at fender arch (with me in the car)

2.2 degrees camber front.
2.0 degrees camber rear ( I think - will have to double check)
Tires are 285/30/18 Kumho V710 at all corners/

Fronts at 26 PSI
Rears at 28 PSI

I took tire temps following several runs yesterday in 90f degree weather.

The temps were consistently hotter on the inside of the tire, indicating I could use a little less camber.

Tire temps would typically be 8-10f degrees hotter on the inside:

outside 90f
middle 95f
inside 99f

The focus here is on the range of temps, not the temps themselves.

I've already asked this question on another forum, and so far the replies are limited to "those temps are too low"

The actual temps are not terribly important IMO - what I am interested in is adjusting the camber to even out the temps across the tire.

Temperatures were taken on 3 cars - my FD, Josh18_2k's V8 FC, and a Corvette Z06. All were driven hard, with similar temps, though the highest I saw were on the FC, with 121f on the inside.

Based on experience, can anyone make some reasonable guesstimates as to how much camber I should take out to start with?

[josh18_2k]

i'm at 1.8 degrees rear, and running hot on the inside (possibly from my sliding shenanagins lol). plan to dial it back to 1.5 and see how that goes.
is your temp split same front and rear? 2 seems like a bit much in the back, since you ahve a good camber curve and stiff springs, but im no FD expert by any means

also- 26F?? i would assume we have similar weights front and rear, and i'm running 30F and 28R. grip seemed to go down any lower than like 29F. i know vette guys run 32F 29R

[jkstill]

Originally Posted by josh18_2k

i'm at 1.8 degrees rear, and running hot on the inside (probably from my sliding shenanagins lol). plan to dial it back to 1.5 and see how that goes.
is your temp split same front and rear? 2 seems like a bit much in the back, since you ahve a good camber curve and stiff springs, but im no FD expert by any means

Yes, the split is similar front and rear.

I've had recommendations in the past to use 1.8 degrees, maybe I will start there.

Originally Posted by josh18_2k

also- 26F?? i would assume we have similar weights front and rear, and i'm running 30F and 28R. grip seemed to go down any lower than like 29F. i know vette guys run 32F 29R

Yes, I know the pressures seem low.

If they were too low, I would expect to see cooler temps in the middle of the tire, but did not.

I initially started these tires out around 32PSI, and keep dropping it until the butt dyno and times said they were working. I may try increasing tire pressure, but first I want to get the camber dialed in.

Maybe a smaller bar in the TriPoint swaybar setup too. The .180 bar was OK yesterday, but when the temps are cooler, it still pushes too much.

One of these days it will be all sorted out, and I will run out of excuses.

[rx4ur7]

Toe set at 0? What are your pressures hot? Is there good roll over, are you using up to the tread markers or past them. Those little triangles that are located around the tire.

With the readings you show, which do seem low, it would seem that your pressures are right and that you might drop the camber .05 to 1 degree. I would try more air in the fronts or less in the rears. Haven't had a lot of exposure to the Kumhos for racing. Yoko, BFG, and Hoosier where the hot ones back when I was running DOT tires. If changing the air pressures doesn't do anything and you have adjustable shocks stiffen the rears or soften the fronts. But only do one thing at a time.

My suggestion for you is-
1 - Try equal pressures,
2 - change camber until you get even temps.
3 - If you still have understeer, soften front or stiffen rear.

How are your lap times compared to the fast guys?

When we were running the Firehawk and Toyo cars we ran same pressures on all four. The cars were all balanced and were 50/50.

[jkstill]

Originally Posted by rx4ur7

Toe set at 0? What are your pressures hot? Is there good roll over, are you using up to the tread markers or past them. Those little triangles that are located around the tire.

Toe is 0.
Pressures were measured after I got out of the car.
As per reply in another forum, I will try to get someone to measure them ASAP next time I run.
Using the tire up to the edge pretty well I think, but I will take a closer look when I get home.

With the readings you show, which do seem low, it would seem that your pressures are right and that you might drop the camber .05 to 1 degree. I would try more air in the fronts or less in the rears. Haven't had a lot of exposure to the Kumhos for racing. Yoko, BFG, and Hoosier where the hot ones back when I was running DOT tires. If changing the air pressures doesn't do anything and you have adjustable shocks stiffen the rears or soften the fronts. But only do one thing at a time.

Going to try the camber first.
Following that I may put the .120 bar in the TriPoint sway bar, as the .180 just seems too stiff during cool weather.

How are your lap times compared to the fast guys?

I thought I was one of the fast guys that day, 6th overall.

1.9 seconds behind FTD (very fast 914-6) and , .8 seconds behind 2nd through 5th place, which were all within a 10th of a second.

I've made progress getting closer to that group, and trying to eliminate that .8 second gap.

[rx4ur7]

I am sure you are using the chauking tire trick to see if you are getting good roll over.

Let's get the tire temps with this setup then go from there. But yes you may be going to the smaller bar.

When I started out and was running solo and finally got fast enough to beat those in class I was running with a full tank of fuel and did not remove the spare tire or jack. Running light fuel and removing everything out of the back of the car turned a 50/50 car into a 58/42 car that was tail happy. I was also running 165 95 13 yokohamas (gumballs) on the 79 7 in CS. All the guys running 205 60s couldn't understand why they kept getting beat by this old ugly grey RX7. I still don't think any realized that I was driving a car that was 4 in shorter and 4 in narrower than they were and had probably a quarter of the contact patch. Solo is won by .001's of a second. My car was .04 faster at the start light because my course was shorter by a few feet. Hey when you only have 95 hp you look for time where ever you can find it.
Afraid the tires did cost a little more and wore out fast, that didn't matter. Trophies in the display case are what counted.

Hard to beat a well built and driven mid engine 914-6. Work on the other four in front of ya. When he sees you knocking them off one by one and then you are second you will start to make him think.


If you want some really good reading material, Get "WinningAutocross Solo II Competition" the art and the science by Turner & Miles. If you can get the companion video tape "Autocrossing with Dick Turner" get it. Also good is Bob Bondurant on High Preformance Driving when you want to make the transition to road racing.

[jkstill]

Originally Posted by rx4ur7

I am sure you are using the chauking tire trick to see if you are getting good roll over.

I haven't lately, as it seemed fairly obvious where the recent wear was, but I will do it again.

Hard to beat a well built and driven mid engine 914-6. Work on the other four in front of ya. When he sees you knocking them off one by one and then you are second you will start to make him think.

Working on it...

If you want some really good reading material, Get "WinningAutocross Solo II Competition" the art and the science by Turner & Miles. If you can get the companion video tape "Autocrossing with Dick Turner" get it. Also good is Bob Bondurant on High Preformance Driving when you want to make the transition to road racing.

Thanks, I don't have either of those books, I will look for them.

[josh18_2k]

Originally Posted by rx4ur7

Hard to beat a well built and driven mid engine 914-6. Work on the other four in front of ya. When he sees you knocking them off one by one and then you are second you will start to make him think.

im the one in 2nd- he's already thinking lol

jared- i looked at your tires, and your roll over looks perfect. right on the line on all 4 tires. i'm thinking camber and pressure need to move in unison
mine are rolled over worse stupid no camber curve in front

[jkstill]

Originally Posted by josh18_2k

im the one in 2nd- he's already thinking lol

Yeah, you are closing in on him.

Don't beat him too bad, we need them to continue letting RX-7's come out to play with them.

jared- i looked at your tires, and your roll over looks perfect. right on the line on all 4 tires. i'm thinking camber and pressure need to move in unison
mine are rolled over worse stupid no camber curve in front

Thanks Josh, working camber and pressure.

[josh18_2k]

oh btw- are you aware of how much treadwidth you lose with a 9.5" wheel?
i have my 285's mounted on 9.5 and 10.5 wheels, and a good half inch of tread disappears when theyre ballooned. they dont even look like the same tire. apparently 710's do better on a wide wheel
food for thought :-)

[jkstill]

Originally Posted by josh18_2k

apparently 710's do better on a wide wheel
food for thought :-)

Yeah, rear would be no problem.

Front, I'm not so sure a larger wheel will fit without flared fenders and less offset.