Petevb

My car is a lightweight early 911. I've been running my V710s with a fair bit of camber- ~2 front, ~2.5 rear.

I was reading in the tire rack "care and feeding" guide, however, that Kumho suggests running much less camber on the V710 than most R compound tires. They're suggesting between .5 degrees and 1.5 degrees for the V710, vs between 1.5 and 3 degrees for the V700, for instance. So I'm wondering if anyone's played with setting camber for the V710s, and if so what they've figured out? Does less camber really work better?

V710 care and feeding:
http://www.tirerack.com/tires/tirete...jsp?techid=155

-Pete

Joe Weinstein

I ran 2-2.5. Your pyrometer will tell you whether you're doing the right thing
or not.
Joe Weinstein

Petevb

I would have thought that a pyrometer would be the best guide, but I just got done reading the new grass roots motorsports setup article in which they show that they were quicker on a camber setup that overheated the outside edge of the tires. They ended up fastest at 3 degrees negative on the MPSCs (Michelin recommends 1.5-3 degrees).

Makes me wonder if anyone's done any testing against a clock, especially since reading the Kumho setup guide makes it sound like they are almost trying to overheat the outside edge?

-Pete

Dr. Car

+1 on Joe's feedback.

The GRM example involves running a full 3 degrees negative, which you say still left the outside of the tire hotter than the inside and which was at the max of recommended cambers for that Michelin tire. Negative camber increases inside temps. What other cambers did they run - were they all less negative? If so it's no surprise the most negative camber was the fastest.

Some cars want more than 3 degrees negative to work their best. Comparing one model of car to another kind is apples-oranges.

Petevb

They also tested 3.5, 2 and 1 degrees, and found 3 degrees fastest even though the 3.5 degrees showed more even temps. The quote was "this is where practical examples diverge from complicated theories". Hence my desire for data beyond tire temps, particularly for these tires.

I'm not trying to compare a mini to my 911, obviously, and in fact it seems comparing optimum alignment for a 911 on one tire vs another is just as apples to oranges. Just compare the recommended camber for a few R compounds:

V710- .5 to 1.5 degrees
V700- 2 to 3 degrees
Hoosier A6- 2.5 to 3 degrees
Toyo R888- 2.5 to 5 degrees

So the minimum suggested camber for all of the rest of these is more than the max suggested for the V710. Hence the question...

Joe Weinstein

I wonder if their test also involved some braking and accelleration. Those
would favor a flat zero-camber setting, so camber becomes a trade-off.
A pure skidpad setting might want the most camber and get the best grip
with even tire heat. Autocross is more like skidpad than track racing.

Petevb

For the test they ran laps on the streets of willow, which is not quite ax course tight but is tighter than most road courses. They noted exactly what you mention- that breaking and power-down suffered as camber was added. Thus a car with more power or power-down issues would want less camber, etc.
But the V710 sounds very different than most R tires, in that it's very round, runs at lower pressures, and is supposed to squish to the road. I thought I might try running 1.25 front, 1.5 rear and see what the times look like. I liked them at 2/2.5, but did have some issues with braking/ power down...

KenJ

Pete,

On the Boxster, I've only got about 25-30 cycles on my V710s with -2.3 front and -2.5 rear and I'm watching the wear closely. I've been running ~30f/29r hot pressures and it's looking like slightly more wear on the insides than outsides.

Since I only AX, I can't compare times - just judge how the car feels/handles. The car is stiffer than stock and I've still got to dial in the ARB balance, but I'm leaning towards reducing the camber a bit too.


kj