Track Report ACR on Kumhos Inde

[Pappy]

Went to Inde with a group of Vipers for a private track day yesterday. Weather was cool (55 degrees) with no rain. I tried a new alignment with -2.5 degrees camber, 6.7 degrees caster, zero toe, and a rebound setting of 7. Ride height was at the recommended 4.0 in. front and 5.5 rear. I started with 30 lbs air pressure and had to bleed down from around 40 lbs to 33 lbs after each of the first two sessions (8-10 laps). After the second bleed, the air pressures stayed at 33 lbs the rest of the day. Front tire temps consistently showed 20 degrees cooler on the outside edges compared to the middle and inside, which were about equal. The car felt good with no notable push. Looking at the front tires and the tire temps, it appears I could go to 2.3 degrees of camber without hurting anything. The tires have 2400 miles on them with two track days, and they don't look too bad. They did not feel like they were giving up any grip. They should be good for at least one more track day. The rears look fine and are wearing evenly. When I first got the car the rears were at 1.7 degrees camber left and 2.0 right. After the first track day you could see more inside wear on the tire with 2.0 degrees camber, so that was too much.

Pappy

Viper Kumho 2.jpg

Viper Kumho 1.jpg

[99RT10]

How were your times in the car? Set any personal records?

[Pappy]

How were your times in the car? Set any personal records?

Didn't really get to time any laps, but they were aggressive, fairly competitive laps - a little slower than Arizona Vipers ACR with 335/345 Hoosiers and more experience on this track, but that was to be expected. If the track was a little warmer I suspect there was room for 3-4 seconds improvement in my times. I will have video and timing capability the next time out.

Pappy

[stradman]

What rear wing are you running?

[Pappy]

What rear wing are you running?

Standard ACR wing still set on "2" high down force.

Pappy

[stradman]

Standard ACR wing still set on "2" high down force.

Pappy

Its interesting how there are quite a few variances with the camber/rear wing/caster. Of course we all want to try to save as much of the front tires as possible and it seems you feel maybe at 2.5 or lower camber could work and keep handling tidy. I'm off for a geo setup/corner balancing on my ACR-E tomorrow and will discuss with the guys there about all the options and let you all know what we figure too..

[Pappy]

Its interesting how there are quite a few variances with the camber/rear wing/caster. Of course we all want to try to save as much of the front tires as possible and it seems you feel maybe at 2.5 or lower camber could work and keep handling tidy. I'm off for a geo setup/corner balancing on my ACR-E tomorrow and will discuss with the guys there about all the options and let you all know what we figure too..

I think the low camber angles (-2.5 or less) will work best with increased caster (6.7 degrees vice the recommended 6.0). I decreased the static camber, but actually ended up with a higher dynamic negative camber number (wheels turned and suspension compressed) on the outside tire and decreased negative camber on the inside tire - all due to the increased static caster and caster gain during compression. This helps the inside tire do more work without destroying the inside edge of the tire like some have seen. Keep us posted on your alignment decisions.

Pappy

[stradman]

Well I finally got my geo/balance done today. Took about 8 hours as my guy was exceedingly detailed(its very good to be that!) He had all the latest geo Hunter equipment etc of course. Just to give you a lo down, my car is a 2016 ACR-E and has only done 1200 miles. I have not had the chance to take it on track yet so I just wanted to see what the car's settings were like out of the box-and get them to recommended levels and lower the car as well. Overall these are the figures before(before any lowering and another after lowering but before final adjusting and then of course after final adjustment.
The main imbalance was at the rear as you can see and which of course got worse upon lowering.

After rear after.jpg Beforebefore.jpgAfter rearweight.jpgfront after.jpg

As you will see I'm basically at about -2.75 degrees camber at the front with about 7 Caster and zero toe. At the rear I am now - 1.75 camber, 2.75 Caster with 0.1 Toe in to improve threshold braking and traction. Ride height went from 118mm front to 102 mm and rear from 159mm to 140mm.
I also corner weighed the car which actually didn't require much work/balancing as you can see as it was very good as is-note the total weight of the car was 1631kgs with 77kgs of driver full tank and 10kgs of balance/geo kit. So overall "wet" weight for the car is 1544kg or 3397 pounds.
As I said I have not tracked the car yet but will do so soon, but I thought it was a very useful exercise to get the car truly as recommended. I don't know ultimately how the car will behave on track yet, but at least I am certain some basics are in place and I can play around with dampers and wing if necessary. The car did have some very light steering pull to one side on acceleration and at constant speed before this so this has now disappeared.
Anyway I suppose this is good for general information or perhaps some idea for baseline for your ACR's but that's my experience so far. Stay tuned for more after tracking!

[Pappy]

[QUOTE=stradman;269765]
As you will see I'm basically at about -2.75 degrees camber at the front with about 7 Caster and zero toe. At the rear I am now - 1.75 camber, 2.75 Caster with 0.1 Toe in to improve threshold braking and traction. QUOTE]

Cool. I don't see the -2.75 degrees camber up front. I think that would be a lot with 7 degrees caster. I like the -2.43/6.55 camber/caster I see in the last screen shot. I just backed my front camber down to -2.4 based on the tire temps and wear during the last track day.

Pappy

[Nemesis]

Dyslexia

[QUOTE=Pappy;269772]

As you will see I'm basically at about -2.75 degrees camber at the front with about 7 Caster and zero toe. At the rear I am now - 1.75 camber, 2.75 Caster with 0.1 Toe in to improve threshold braking and traction. QUOTE]

Cool. I don't see the -2.75 degrees camber up front. I think that would be a lot with 7 degrees caster. I like the -2.43/6.55 camber/caster I see in the last screen shot. I just backed my front camber down to -2.4 based on the tire temps and wear during the last track day.

Pappy

[stradman]

[QUOTE=Pappy;269772]

As you will see I'm basically at about -2.75 degrees camber at the front with about 7 Caster and zero toe. At the rear I am now - 1.75 camber, 2.75 Caster with 0.1 Toe in to improve threshold braking and traction. QUOTE]

Cool. I don't see the -2.75 degrees camber up front. I think that would be a lot with 7 degrees caster. I like the
-2.43/6.55 camber/caster I see in the last screen shot. I just backed my front camber down to -2.4 based on the tire
temps and wear during the last track day.



Pappy

Well you see 2 degrees .43 minutes is actually 2.75 degrees total as each degree has 60 minutes. So 43 minutes is 2/3 of a degree or about .75. I do wonder if some people are confusing what they see with what they report. I sure did until it
was pointed out to me!!

[ek1]

Well you see 2 degrees .43 minutes is actually 2.75 degrees total as each degree has 60 minutes. So 43 minutes is 2/3 of a degree or about .75. I do wonder if some people are confusing what they see with what they report. I sure did until it
was pointed out to me!!

0.75 is actually 3/4.

2/3 would be ~0.66

[Pappy]

[QUOTE=stradman;269852]

Well you see 2 degrees .43 minutes is actually 2.75 degrees total as each degree has 60 minutes. So 43 minutes is 2/3 of a degree or about .75. I do wonder if some people are confusing what they see with what they report. I sure did until it
was pointed out to me!!

Good point out. So 43/60 = .717 so you ended up with 2.7+ degrees of camber. I am anxious to see how that works out for you, but I suspect it will be too much negative camber and you may not get good tire temps at the outside edge of the tire. When are you going to the track?

Pappy

[stradman]

0.75 is actually 3/4.

2/3 would be ~0.66

Yes true. I just did it roughly in my head-clearly maths not my strong point!

[stradman]

[QUOTE=Pappy;269894]

Good point out. So 43/60 = .717 so you ended up with 2.7+ degrees of camber. I am anxious to see how that works out for you, but I suspect it will be too much negative camber and you may not get good tire temps at the outside edge of the tire. When are you going to the track?

Pappy

Well I guess we'll see however this is slightly less than the track setup video that SRT put out, in August 16' I believe, which suggested 2.8' of camber front here: https://www.youtube.com/watch?v=qHvZCQyzxdA . I'll report back accordingly once I've done my first track day at Silverstone March 6th.

[Arizona Vipers]

Man we've got some math geniuses on here.