ET Street R Bias Ply tire pressure?

I've got a set of ET Street R Bias Ply 28-11.5-17's for my 2018 M6. What kind of tire pressure are you guys starting with as a baseline with that size tire? Bout 20 psi and go down from there?

Thanks!

Start at 16 cold, After the first burn out I shoot for 16, but have gone as low as 11. At 11 they were hooking with no slip on an unpreped track, 700+hp. The "sway" with radial front tires gets bad below 14.

A stock gt will probably hook fine at 20psi... The more air pressure you can get away with the faster and safer the ride. I would try it at 20 and go from there.

I was running them on my buddy's whipple auto at 15psi hot and the sway was more than I liked. He was running bias fronts as well. I think the key to a good launch on a stick is a slight amount of slip when you release the clutch. I was able to manage 1.51 60 fts on my 2015 Manual on motor. I went a 11.4 at 119

thanks guys. My car is currently 100% bone stock, and I was concerned about rear sway. I forgot to mention that so I'm glad you guys took up that issue. Our track is only 1/8 mile so if I'm only turning, what, 86/87 mph(?) I may not notice too much sway if I can get by with 20 psi.

Ive been cutting 1.62-1.61 60's on 18psi with no sway or issues in the 1/8th with stock PP wheels and Continentals up front. Im still working my way up the RPMs on the launches but if it doesnt get much quicker then I might try 16psi and go from there.

Matt

what kind of rpm are you N/A guys launching at? Giving it any slip at all or just send it?

Ive gone as high as 5500rpm just dumping the clutch and it loves it.

Matt

any mods to the IRS to handle that? The BMR "Bread and Butter" kit is on my to do list, but these tarrs are my first mod at this point.

BMR Sp080 springs and CB005 lockouts. I did that to help with the hop on street tires and make it look better. Obviously didnt hurt with the Bias Ply's!

Matt

66sprint6 said:

Ive gone as high as 5500rpm just dumping the clutch and it loves it.

Matt

Click to expand...

Yup! Let them bias ply tires do the work instead of your clutch. :cheers:

I have that tire and 3.31 gear. I usually leave right around 6800-6900 rpm's.

I ran 15-16psi on my car.
5k sidestep almost stalled it.
Never got around to testing any further but I’d say higher pressures to create a small amount of tyre slip wouldn’t hurt at all.

so I took my car to the track for the first time yesterday. It was my first time racing a stick car in 11 years, as well as my first time ever launching on bias ply tires!

Either I'm going to need some serious advice on how to launch these particular cars on a bias ply, or the stock tune really has some kind of torque management even with all the nannies turned off.

Best I could manage were a few 8.24/8.26 passes at 86.7 or so mph with 1.84 60's. DA was 2460'. Bone stock 2018 was in Drag Mode, Advance Trac, Trac Control, and Launch Control all deactivated. I started off at 20 psi with a 5500 rpm side step... it would dead hook, then bog, forcing the rpms all the way down to about 2500. I raised launch rpm up to about 6500, eventually upped tire pressure to 23 psi, and it still did the same thing. Dead hook, then bog down. This method provided very disappointing 2.00-2.08 60's leading to 8.5x-8.6x ET's @ 86. Nothing I tried would give me any wheelspin at all, nor could I keep forward momentum out of the hole. Very disappointing to me because I've always been able to pull out 1.82-1.85 60' times on all season radials in just about every street car I've ever owned.

So just for the sake of trying to escape with a descent ET, I used my 23 years racing experience reverting to old street tire days, and tried a 5000 rpm launch with a hint of clutch slip. This kept momentum up, and managed 1.84 60's this way. This 60' immediately dropped the car down to 8.2x's consistently.

I was really disappointed, figuring these cars even bone stock make enough power to be able to do a high rpm clutch sidestep on a bias ply tire and not bog down like this. Even in Drag Mode w/ Advance Trac, Trac Control, and Launch Control turned off, is there still some sort of electronic nanny in the stock tune forcing this issue?

Despite the 2460 DA, I was really expecting a 1.67-1.73 60' time on a sidestep which should have provided me the 7.99 I was hoping for. Any tips, or is this just something in the stock tune that I'll eliminate when I begin my mods?

I've heard other people having issues with torque management but I never ran into it with stock tune or my current pp2 tune. I would think a aftermarket tuner could turn it off. I think some of the nannies on these cars can really vary from car to car.