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How much neg camber out back for autox?

odessa.filez

Autocross Newbie
Location
Roswell, GA
Car(s)
2016 GSW 1.8tsi auto
Some context for my 2016 Golf Sportwagen car.

1. I run in a "modified club rules" class, not SCCA. I can pretty much do whatever I want suspension wise and remain in class. Big constraint is tires are limited to 205 width, min 140 tw.

2. I have both audi tt arms (recent mod) up front and vorshlag plates. Front camber should not a problem. Might be able to reach -6 if I wanted to. I've been running at -3 before adding the arms but need tire pressure to prevent the outsides from rolling over at -3. Arms and plates add about 1 degree caster (total +2).

3. Rear camber is somewhere between -1.25 to -1.5.

4. Car rotates reasonably well with some spring tricks out back - bump springs, slightly larger rear bar, spring rubbers all make it configurable and setting things to lift oversteer is easy.

5. Tires and tire pressures - have been running RE-71R at 50psi in the back, 46 front to limit rollover. I added more camber capacity up front in the hopes of lowering the pressure and slowing outside wear.

6. No LSD.

Given everything, I'm thinking of increasing neg camber out back to around -2 to -3 vs -4.5 up front.

Back camber doesn't get too much discussion. What do you folks think about the back in a car that has lots of potential grip up front?

Thanks,
Bill
 

odessa.filez

Autocross Newbie
Location
Roswell, GA
Car(s)
2016 GSW 1.8tsi auto
Your tire pressure seems really high. I aim for about 36 hot which is about 32 cold
agree. want to bring psi down.

first event with new re71r, we set everything at 38psi cold, front camber -3. Outside wear was horrendous, seemed worse in the back.

also worth mentioning tires are 205 50r15, 86 load rating vs 91 stock spec. Relatively heavy car given tire width for this activity imo.
 

jay745

What Would Glenn Danzig Do
Location
Slightly Outside Chicago
Car(s)
Mk6 racecar, Tacoma
agree. want to bring psi down.

first event with new re71r, we set everything at 38psi cold, front camber -3. Outside wear was horrendous, seemed worse in the back.

also worth mentioning tires are 205 50r15, 86 load rating vs 91 stock spec. Relatively heavy car given tire width for this activity imo.

Are you adjusting the toe after you increase the camber? The toe is really what wears the tires down, not the camber really.
 

jmason

Go Kart Newbie
Location
Frederick, MD
From my track experience, there isn't much suspension compression evident through a turn on the loaded side of the car. I suspect this is due to the high roll stiffness due to the larger diameter sway bars and higher spring rates provided by my mods. Thus, it appears that the car rolls about the outside tire contact patch. So the camber you get is pretty much the static camber (no camber gain from suspension compression). Increasing rear negative camber (AFAIK -2 is the max with stock components) should result in more tire grip at the rear. You could trade this off with increased rear roll stiffness, resulting in a more neutral-handling car; the higher grip accommodating greater weight transfer before loss of grip.
 

odessa.filez

Autocross Newbie
Location
Roswell, GA
Car(s)
2016 GSW 1.8tsi auto
Are you adjusting the toe after you increase the camber? The toe is really what wears the tires down, not the camber really.
I set toe as close to zero as possible, at street camber settings and autocross settings.

The wear I alluded to earlier is outside tire wear after about 10 miles of driving on the AX course.
 

odessa.filez

Autocross Newbie
Location
Roswell, GA
Car(s)
2016 GSW 1.8tsi auto
From my track experience, there isn't much suspension compression evident through a turn on the loaded side of the car. I suspect this is due to the high roll stiffness due to the larger diameter sway bars and higher spring rates provided by my mods. Thus, it appears that the car rolls about the outside tire contact patch. So the camber you get is pretty much the static camber (no camber gain from suspension compression). Increasing rear negative camber (AFAIK -2 is the max with stock components) should result in more tire grip at the rear. You could trade this off with increased rear roll stiffness, resulting in a more neutral-handling car; the higher grip accommodating greater weight transfer before loss of grip.
thank you!
 
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