Track musings - camber, temperature and wear

[Ft.S]

Regardless of theory, real-world data overrides all others . Once you try the new alignment settings, hopefully you can update us

 

[CNBHOME]

All...
I have Thousands of laps racing 14 different cars, everything from a Sumbeam Tiger to 3 different Vintage F1 cars from 1983/84/85 and have learned a lot about setup. I currently have an Emira With UCA adjustables from GRP (Greg is a great source) with -3.5F, -3.2R, 1/8+ F toe out and 1/8 Toe in rear and Nitron race shocks with settings around 70 to 75% of max control, Inch wider F/R 20 inch wheels, Hoosier R's 265F / 305R (everything clears with the negative camber). These tires are Radials and probably all the other brands are also, in this range and designed for car weight of 3000 pounds are suprisingly heavy. For referance a 13" by 13" wide 3 piece wheel and a cross ply race tire for a 1350 pound sport racer weighs around 20 pounds .

This is the issue for tire wear. Radials need lots of camber. I now have 5 track days at Laguna Seca and Sears Point and am about at 50% wear measured at the DOT holes and the little .5in center tread. All within a few thousants of an inch. I was suprised on the tire pressure needing to be in the 40/42 PSI hot range to clear up the rubber pickup in the center. Did not think that a radial could do that but that is what was required to make the tire work.

Something else that matters at certian tracks. Laguna does not have any ESSES just turns, Sears Point has true ESSES and the Emira has a noticable role issue with conntected turns. The cure for this is not stiffer sway bars but stiffer front springs. The car at speed when a second turn , in a series, is needed, will roll twice as much as a single turn causing traction to fail on the second turn. The stiffer front spring prevents that dive into the forward force.

For referance and the only turn that ever mattered to me is turn 6 at Laguna. It took me a while to get it but this last session a few weeks ago, I was able to run it in 5th gear without lifting in the Emira. Fun to see the GT3 RS's fall behind going up the hill, O" for another 200HP.

 

[BruceN]

Hello,

This is an interesting thread overall, and my current experience is more inline with Bruce's, although I haven't tracked as much as he has.

The negative camber needs of the Emira maybe different than that of many other cars that use strut-type suspension. The big benefit of double-wishbone architecture is that it provides more control of dynamic changes at the wheels.

The resultant impact on camber changes is nicely depicted in the following diagram by Grassroots Motorsports,. This is not the rule, but general natural of strut-based vs. wishone-based.

View attachment 84636​

Interesting. I appreciate your explanation input

 

[BruceN]

I don't know how valid this is, but I did some "idiot math" on my track wheels. I measured the amount of wear on the inside and outside of the tires, and the outsides were worn much more. A little bit of trigonometry, and you can figure out the angle of the wheel. My front wheels were worn at about 1 degree from vertical, while the rear wheels were less than 0.5 degree from vertical. Now, given my camber on the car, of -1.5F and -2.0R, this would imply that I'd need about -2.5F and something less than -2.5R for more even track wear (a little more camber in front than rear)

There's a huge amount of error here, but the double wishbone camber doesn't seem to be helping me much. My tires are shredded on the outsides while looking barely worn on the insides.

Interesting. Do you have an engineering background? I appreciate this type of applied math!

 

[BruceN]

I am on Nitron ClubSports, which are borderline adequate, stiffness could be harder for the track, but I'm also street driving it, so I don't want to ruin streetability. I did not update the anti-roll bars, so the relationship changed. Relative to my spring rate my anti-roll bars are now softer, but on the flip side, the car doesn't lean as much.

I'm still figuring it out. All I know is that, for now, i need more negative camber. I'm going to try about -2.5f -2.3r and see how that does. It'll make the car much more likely to follow road imperfections on the street, but I can't be wasting one set of tires per track day.

Please lmk how that goes. It’s hard for me to imagine that increasing camber wouldn’t have significant benefit but I’d like more data (drivers experiences) before committing

 

[lynchy73]

I'm running circa 3.5F and 3.0R camber, using aftermarket upper control arms. I can fully confirm it's a significant improvement on track and the tyres do not get shredded on the outside edge on track any more. They now seem to wear very evenly on track and seem much happier than before (can't comment about inside edge wear on the road, as i haven't done much road driving with this setup). I'm running standard I4 Sport springs/dampers, but i have lowered the car by dropping the springs 10mm in the shock (moving the circlip 2 positions). I've also done ARBs (and various other suspension upgrades) and that seems to have reduced the roll noticeably. Recently went to 265,35/20 Front and 305/30/20 Rear tyres on 9R/11F rims (with more offset than OEM). The new Tyres are Sailun PT01 and i really like them, much prefer them to the Cup2 i was running previously. The Sailun seem to grip better and it is much less crashy on bad roads.

 

[BruceN]

I'm running circa 3.5F and 3.0R camber, using aftermarket upper control arms. I can fully confirm it's a significant improvement on track and the tyres do not get shredded on the outside edge on track any more. They now seem to wear very evenly on track and seem much happier than before (can't comment about inside edge wear on the road, as i haven't done much road driving with this setup). I'm running standard I4 Sport springs/dampers, but i have lowered the car by dropping the springs 10mm in the shock (moving the circlip 2 positions). I've also done ARBs (and various other suspension upgrades) and that seems to have reduced the roll noticeably. Recently went to 265,35/20 Front and 305/30/20 Rear tyres on 9R/11F rims (with more offset than OEM). The new Tyres are Sailun PT01 and i really like them, much prefer them to the Cup2 i was running previously. The Sailun seem to grip better and it is much less crashy on bad roads.

Thanks. How did your lap time change after maximizing camber? My tire wear is pretty good on maxed OEM camber, so the temptation for UCAs is for faster laps

 

[Tracked Emira]

I'm running circa 3.5F and 3.0R camber, using aftermarket upper control arms. I can fully confirm it's a significant improvement on track and the tyres do not get shredded on the outside edge on track any more. They now seem to wear very evenly on track and seem much happier than before (can't comment about inside edge wear on the road, as i haven't done much road driving with this setup). I'm running standard I4 Sport springs/dampers, but i have lowered the car by dropping the springs 10mm in the shock (moving the circlip 2 positions). I've also done ARBs (and various other suspension upgrades) and that seems to have reduced the roll noticeably. Recently went to 265,35/20 Front and 305/30/20 Rear tyres on 9R/11F rims (with more offset than OEM). The new Tyres are Sailun PT01 and i really like them, much prefer them to the Cup2 i was running previously. The Sailun seem to grip better and it is much less crashy on bad roads.

I’m running 18 inch slicks. What alignment settings would you recommend?

 

[jp129]

I’m running 18 inch slicks. What alignment settings would you recommend?

Use tire temps and chassis balance to guide you, especially on racing slicks. Those are more setup and temperature sensitive then DOTs.

Cross referencing with folks that frequent your track and running the same tires gives you resolution on your setup.

 

[Tracked Emira]

As far as I know I’m the only one in America tracing 18 inch slicks with an Emira except for the race cars. Anybody else so you can tell me your alignment specs?
What alignment specs do the race cars run?

 

[OppositeLock]

What tires and in what sizes are you running @Tracked Emira . I'm sick of burning through the 20" tires, despite my pretty GRP forged wheels, and I'm considering 18"'s. It's REALLY expensive on 20's and I'm 7 sets of tires in already.

 

[mr.suntorytime]

What tires and in what sizes are you running @Tracked Emira . I'm sick of burning through the 20" tires, despite my pretty GRP forged wheels, and I'm considering 18"'s. It's REALLY expensive on 20's and I'm 7 sets of tires in already.

 

[OppositeLock]

I've already got your EPB adapters, @mr.suntorytime

 

[mr.suntorytime]

I've already got your EPB adapters, @mr.suntorytime

come get some wheels

 

[Honcho]

I'm running circa 3.5F and 3.0R camber, using aftermarket upper control arms. I can fully confirm it's a significant improvement on track and the tyres do not get shredded on the outside edge on track any more. They now seem to wear very evenly on track and seem much happier than before (can't comment about inside edge wear on the road, as i haven't done much road driving with this setup). I'm running standard I4 Sport springs/dampers, but i have lowered the car by dropping the springs 10mm in the shock (moving the circlip 2 positions). I've also done ARBs (and various other suspension upgrades) and that seems to have reduced the roll noticeably. Recently went to 265,35/20 Front and 305/30/20 Rear tyres on 9R/11F rims (with more offset than OEM). The new Tyres are Sailun PT01 and i really like them, much prefer them to the Cup2 i was running previously. The Sailun seem to grip better and it is much less crashy on bad roads.

What roll bars and control arms are you using?

 

[lynchy73]

What roll bars and control arms are you using?

The suspension upgrades all come from BoomGear in China. There was also various links and solid bushings for lower control arms too. My car is an I4.

 

[mr.suntorytime]

What roll bars and control arms are you using?

Do you have a v6 or i4?

 

[Tracked Emira]

Michelin pilot sport slicks
Front are 27/65/18 N2
Rear are 30/66/18 N3
Wheels from mr.suntorytime

 

[Super Roo]

I had my first track day this week. Car is lowered about 20mm on Modal 3-way dampers. -1.7F and -2.7R camber. LTS Goodyears.

I did about 130km on track, starting slowly and building up through the day. The rears aren’t too bad but the fronts are already pretty distressed and as I get the hang of the car, I can’t see them lasting beyond the next track day.

Has anyone tried these as a more cost effective alternative to UCAs? Any reason they are a bad idea? I will contact the vendor this week to understand what increase in camber can be achieved with the Stage 1 and Stage 2 options.

Camber plates for Lotus Evora, Exige and Emira – Stage1 – VTSRacing by Vali

More camber for the race track. A set consisting of 2 pairs of eccentric inserts each as shown, thickness 5mm (total 4 pcs.). ATTENTION: Our parts for sale here are for tracks and racetracks. They are not street legal !!

thomasschuhmann.de

 

[mr.suntorytime]

I had my first track day this week. Car is lowered about 20mm on Modal 3-way dampers. -1.7F and -2.7R camber. LTS Goodyears.

I did about 130km on track, starting slowly and building up through the day. The rears aren’t too bad but the fronts are already pretty distressed and as I get the hang of the car, I can’t see them lasting beyond the next track day.

Has anyone tried these as a more cost effective alternative to UCAs? Any reason they are a bad idea? I will contact the vendor this week to understand what increase in camber can be achieved with the Stage 1 and Stage 2 options.

Camber plates for Lotus Evora, Exige and Emira – Stage1 – VTSRacing by Vali

More camber for the race track. A set consisting of 2 pairs of eccentric inserts each as shown, thickness 5mm (total 4 pcs.). ATTENTION: Our parts for sale here are for tracks and racetracks. They are not street legal !!

thomasschuhmann.de

Those camber plates have been around for a while. Please note you will have to have someone cut into your frame to install these.