# Track and street Camber Settings Using GruvenParts Rear Control Arms



## eskimo87 (Sep 11, 2013)

Im running 1 set of GruvenParts lower rear control arms for my TT, wondering what camber settings you guys run for track days. Right now Im at -1.5 but the bars allow for up to -2.5 and +2.0. That adjustment range should be more than enough. 

Just wondering what you guys run for track and street.


----------



## 20v master (May 7, 2009)

-1.4 on the street.


----------



## Marcus_Aurelius (Mar 1, 2012)

-1.3 to -1.6 is the goldilock range street or track.


----------



## Teeguzi (Jul 22, 2011)

I run:

-2.8 Front
-2.0 Rear

Car feels very predictable and manageable/correctable with R888s. Never really drive on the street though.

Cheers! :beer:


----------



## Marcus_Aurelius (Mar 1, 2012)

Teeguzi said:


> I run:
> 
> -2.8 Front
> -2.0 Rear
> ...


Why so much static rear camber compensation? Is it a result of just feel or there was data or testing to lead you to this camber setting? (if you don't mind me asking) :beer:


----------



## Teeguzi (Jul 22, 2011)

Marcus_Aurelius said:


> Why so much static rear camber compensation? Is it a result of just feel or there was data or testing to lead you to this camber setting? (if you don't mind me asking) :beer:


Recently changed rear camber from -1.7. I've run two sessions at Thunderhill with no negative effect. Car feels very neutral and is easy to control using throttle modulation. No real testing beyond how the car feels to me. T10 trail braking oversteer at Laguna Seca that almost always led to a nasty snap back was the motivator for the change. Unfortunately I have not been back to LS since. :banghead:

Cheers :beer:


----------



## TheDeckMan (Sep 26, 2004)

-1.7 f
-1.3 r


----------



## eskimo87 (Sep 11, 2013)

what kind of tires? thats a total race set up ! how long do you get out of a set of rear tires ?



Teeguzi said:


> I run:
> 
> -2.8 Front
> -2.0 Rear
> ...


----------



## Teeguzi (Jul 22, 2011)

eskimo87 said:


> what kind of tires? thats a total race set up ! how long do you get out of a set of rear tires ?


This is my second set of Toyo R888s; I got 15 track days (plus drive to and from track) out of the prior set with these camber settings:

F: -2.0
R: -1.7

The current set of R888s have 10 days with old settings and 2 days with new settings; so far even tread wear. I do rotate front/rear between each track day. Basically it averages out that I am putting new tires on once a year. My car doesn't see street use outside of driving to and from track.

Max, would love to get your input on my set up as your way ahead of me regarding camber/toe, suspension set up, etc.

Cheers! :beer:


----------



## Marcus_Aurelius (Mar 1, 2012)

Teeguzi said:


> This is my second set of Toyo R888s; I got 15 track days (plus drive to and from track) out of the prior set with these camber settings:
> 
> F: -2.0
> R: -1.7
> ...


I actually wanted to post my opinion on your setup, but held back because people seem a bit touchy on Vortex nowadays about constructive technical analysis of their setup. So, unless asked, I try to keep comments to myself when it comes to people's setup. 

The track testing and empirical data gathered suggests that you have more static rear camber than needed. I don't have all your data (spring/bar rate being a determining factors in finding the sweet spot in the dynamic camber curve), so I can't be too exact. However the -1.3 to -1.6 range I posted (staying in the rear) seems to be the workable range. So everyone can follow, for track duty, the main reason to dial some static camber is to get a contact patch that has full contact and isn't lifted when loaded in a turn. An indication of a dialed camber compensation is an outside tire that's near perpendicular to the ground plane at full load (obviously while cornering). 

To expand a bit more, sometimes people make compromised choices based on feel or tire wear. For example, one may dial more static camber than needed just to have a more evenly spread tire wear on a car that isn't aggressive with the amount of cornering done (most street cars). Others may do it for the feel simply because it masks other problems like inherent understeer issues that have not been addressed. I think that's where your specific case lands, the less "understeery" feel of unsticking the rear end lead you to believe that it is a good move (or mask the fact that it's a bad one). In reality, unsticking the rear (whether it being with big rear swaybars or lots of camber) is never beneficial because overall grip is reduced 

Now, where do I get this arbitrary camber range that I mentioned? A lot of testing and data gathering, but at some point I also did the camber curving and it backed up the conclusions made from the track testing. When I first started autocrossing the TT, I did so on the stock suspension (despite the fact that I was running 315 race rubber). I killed a set of rear tires in short order (inside-middle portion cording first) and that was my first clue that the high stock camber specs where suboptimal. On my second set, I started recording tire temp, this told me that with 1.8-1.9 degree I had dialed at the time, I was still not fully using the outside of the contact patch for the use of the car. To make a long story short, from stock-like wheel rate, up to the very stiff 1300 lbs rear springs I use when racing, the ideal camber compensation that isn't influenced by the car's balance falls between that -1.3 to 1.6 static compensation range. So if you have a softly sprung car, -1.6 might be a good target, while more properly sprung cars would benefit from targeting around -1.3 static compensation. 

As for the front, when it comes to static camber compensation, the universal rule of thumb for McCrapson based cars is "a lot". This holds true to the TT, and my personal recommendation to everyone that cares to listen is always 'RUN AS MUCH FRONT CAMBER AS YOU CAN GET'. 

(Toe settings for the track can be discussed if you're interested, but I'll leave it at that for now). :beer:


----------



## Marcus_Aurelius (Mar 1, 2012)

^^^

For visual purposes, this is what my car looked like (first pic) without the proper static camber compensation dialed. Even on a rare on-camber turn, I had positive outside dynamic camber angles. 

In the second pic, showing the only the front and taken later, you can see the desired dynamic. The loaded outside front tire is nearly perpendicular to the ground plane (the tel pole in the background is a perfect reference point).


----------



## Teeguzi (Jul 22, 2011)

Marcus_Aurelius said:


> I actually wanted to post my opinion on your setup, but held back because people seem a bit touchy on Vortex nowadays about constructive technical analysis of their setup. So, unless asked, I try to keep comments to myself when it comes to people's setup.
> 
> The track testing and empirical data gathered suggests that you have more static rear camber than needed. I don't have all your data (spring/bar rate being a determining factors in finding the sweet spot in the dynamic camber curve), so I can't be too exact. However the -1.3 to -1.6 range I posted (staying in the rear) seems to be the workable range. So everyone can follow, for track duty, the main reason to dial some static camber is to get a contact patch that has full contact and isn't lifted when loaded in a turn. An indication of a dialed camber compensation is an outside tire that's near perpendicular to the ground plane at full load (obviously while cornering).
> 
> ...


Thanks for all of the input! I'm no the type to get upset over constructive discussion; learning almost always requires an exchange of data and sometimes being wrong. I've got 4 track days left this season all at Sears Point/Sonoma. I may revert back to the -1.6 setting on the rear with a new set of tires.

I'm not totally sure I followed you regarding understeer/push vs. my rear camber settings. The reason I increased rear camber was with the thought of increasing the rear tire contact patch in turns to decrease the oversteer I was experiencing. Attempting throttle modulation while in oversteer always led to a very hard snap back which while controllable once expected still was very nerve racking.

I'll assume my rear springs (H&R SS Coils) are harder than stock but definately not super stiff.

Cheers,
Jim


----------



## Marcus_Aurelius (Mar 1, 2012)

Teeguzi said:


> I'm not totally sure I followed you regarding understeer/push vs. my rear camber settings. *The reason I increased rear camber was with the thought of increasing the rear tire contact patch in turns to decrease the oversteer I was experiencing*. Attempting throttle modulation while in oversteer always led to a very hard snap back which while controllable once expected still was very nerve racking.


You got the right idea, but remember that the concept is applicable to a bell-shaped curve. Say you are starting from scratch with zero static camber compensation (keeping wheel rates, ride height, and all else equal), adding negative camber compensation will keep increasing the contact patch by improving the dynamic camber angles when loaded in a turn. However, due to the bell shaped camber curve, this compensation process only works up to a specific point (when the dynamic angles lands at the top of the curve), and operating anywhere after that point in the curve gives the opposite of the desired effect. 

Therefore, adding static negative camber is good until you exceed that dynamic threshold, and adding more compensation than the advised range is too much for our rear multi-linked geometry. The ultimate goal is to have the tire patch perpendicular to the ground plane at the maximum lateral-G that the outside tire can generate. Ideally, you want to dial just enough compensation that you never cross the apex of the camber curve dynamically. With more compensation than needed, what happens is that you never get to use contact patch to its full potential... and even when fully loaded, the inner 2/3 of the tire is doing all the work (the rest just taken along for the ride). 

Another thing to also remember is that static compensation is always a calculated compromise. If we had a geometry that continuously gained camber proportionally throughout the entire curve, there would be no point to dial compensation because doing so also decreases acceleration and braking potential. By keeping the static compensation in the range that lets you make the most out of the dynamic angles, you maximize the cornering ability as well as braking and acceleration capability.

Since you mentioned that you were looking to reduce some oversteer you experienced, what were your toe settings before and after in the rear? And under what conditions did the oversteer happened (what turning phase, or is it mostly on throttle lift/braking)?


----------



## tedgram (Jul 2, 2005)

opcorn:


----------



## eskimo87 (Sep 11, 2013)

I went to a road race last year at Watkins Glenn and was looking at the BMWs in the pits. I thought the wheels were on wrong so I started talking to a pit crew guy on 1 of the teams. He said no one says exactly what their camber is but somewhere between -3 and -4 ! I think that was only on the left side, since its mainly a right turn course. So I guess those guys like lots of negative camber too, although its surely different from BMW to Audi cars.

Thanks for all this discussion, Im going to set mine at -1.2 for now, seems like good balance between tire wear and track handling.


----------



## Teeguzi (Jul 22, 2011)

Marcus_Aurelius said:


> You got the right idea, but remember that the concept is applicable to a bell-shaped curve. Say you are starting from scratch with zero static camber compensation (keeping wheel rates, ride height, and all else equal), adding negative camber compensation will keep increasing the contact patch by improving the dynamic camber angles when loaded in a turn. However, due to the bell shaped camber curve, this compensation process only works up to a specific point (when the dynamic angles lands at the top of the curve), and operating anywhere after that point in the curve gives the opposite of the desired effect.
> 
> Therefore, adding static negative camber is good until you exceed that dynamic threshold, and adding more compensation than the advised range is too much for our rear multi-linked geometry. The ultimate goal is to have the tire patch perpendicular to the ground plane at the maximum lateral-G that the outside tire can generate. Ideally, you want to dial just enough compensation that you never cross the apex of the camber curve dynamically. With more compensation than needed, what happens is that you never get to use contact patch to its full potential... and even when fully loaded, the inner 2/3 of the tire is doing all the work (the rest just taken along for the ride).
> 
> ...


Love the Bell Curve visual in my head; totally makes sense. Went out and looked at contact patch on rears just sitting in the garage and I can see your point. A rough wag would be ~95% use of rear tires with outer 5% not in use. Not sure how pressure changes and turn induced roll will affect this. T2 offers a small chance to play with oversteer at Sears Point; I'll let you know if anything else feels different.

Oversteer in T10 at Laguna Seca was largely induced by high speed entry with braking (weight transfer onto front left wheel) followed by rapid transition to throttle at apex. Experimenting on inducing oversteer and then recovering smoothly was the point after the initial "Oh ****" moment. Unfortunately I could not recover without aggressive snap back. As I am only rocking 200HP (on a cold day) I don't have the option of powering through oversteer. Couple the lower power/AWD (Competition Controller) together and it may be that snap back is unavoidable meaning I shouldn't push to an oversteer situation to start with (no fun in that though). These type of "moments" are what tracking is all about and dialing in your car from the things you learn. I'll run this set up and probably change the rears back to -1.5 on the next set of tires.

Cheers!


----------



## Marcus_Aurelius (Mar 1, 2012)

Teeguzi said:


> Love the Bell Curve visual in my head; totally makes sense. Went out and looked at contact patch on rears just sitting in the garage and I can see your point. A rough wag would be ~95% use of rear tires with outer 5% not in use. Not sure how pressure changes and turn induced roll will affect this. T2 offers a small chance to play with oversteer at Sears Point; I'll let you know if anything else feels different.
> 
> Oversteer in T10 at Laguna Seca was largely induced by high speed entry with braking (weight transfer onto front left wheel) followed by rapid transition to throttle at apex. Experimenting on inducing oversteer and then recovering smoothly was the point after the initial "Oh ****" moment. Unfortunately I could not recover without aggressive snap back. As I am only rocking 200HP (on a cold day) I don't have the option of powering through oversteer. Couple the lower power/AWD (Competition Controller) together and it may be that snap back is unavoidable meaning I shouldn't push to an oversteer situation to start with (no fun in that though). These type of "moments" are what tracking is all about and dialing in your car from the things you learn. I'll run this set up and probably change the rears back to -1.5 on the next set of tires.
> 
> Cheers!


What are your rear toe settings? I'm asking because, from experience with these cars, rear toe is the most influential factor for medium-high speed cornering stability. Having your rear toe dialed transforms these car's on-track behavior and greatly instill driver confidence.


----------



## eskimo87 (Sep 11, 2013)

toe in or out on rear?


----------



## 20v master (May 7, 2009)

Toe in for the rear.


----------



## LF_gottron (Jan 24, 2013)

-3 front 
-10 rear
daily haha


----------



## Teeguzi (Jul 22, 2011)

Marcus_Aurelius said:


> What are your rear toe settings? I'm asking because, from experience with these cars, rear toe is the most influential factor for medium-high speed cornering stability. Having your rear toe dialed transforms these car's on-track behavior and greatly instill driver confidence.


OP, sorry for hijacking your thread. Hope all of this discussion is also helpful for you.

Max,

My front and rear toe was set to 0 (based on Toyo recommendation for track use on Spec Miatas). I'll be installing your rear control arms this weekend and then taking car in for rear alignment prior to Sonoma. I will probably have them set the camber to -1.6; although car felt fine at -2.0 I can see where I may have "Over-dialed" the rear settings. What are your recommendations for rear toe?

Cheers! :beer:


----------



## Marcus_Aurelius (Mar 1, 2012)

Teeguzi said:


> OP, sorry for hijacking your thread. Hope all of this discussion is also helpful for you.
> 
> Max,
> 
> ...


Yeah, -1.6 static compensation will serve you better in the rear. 

As far I rear toe settings, you need some toe-in to take away the liveliness of the rear at speed. Dialing some toe-in will make the car much more stable IMO and inspire confidence. This will allow you go faster by facilitating drriving closer to 10/10th without having to deal with unexpected twitchiness in the back. 1/32" to 1/8" seems to be the workable range for track duties, but personally I find 1/16" to be the sweet spot for my driving skills and aggressive habits (a smoother and calmer driver could probably live with less, maybe 1/32", but I feel that anything less than 1/16" is scary when you leave it all hang out). :beer:


----------

