mdk

I've been doing HPDE for about a year now and looking for a way to control wheelspin on the straights. I'm running with pfadt coilovers(tried all settings) hoosier A-6 345/30/19 rears. I'm pushing 600hp at the wheels and loose alot of speed from wheelspin and throttle modulation. thanks for any input, Mike

Jason

If you can spin the tires from one corner to the next, I guess you have enough hp.

Solofast

Didn't Mark Donohue say that???

"If you can leave two black stripes from the exit of one corner to the braking zone of the next, you finally enough horsepower".....

Ok, all kidding aside, you have plenty of hp and you aren't using crap tires, so perhaps a bit less negative camber in the back and a bigger rear spoiler or wing would help. Also if your tires are getting old they won't be as sticky so fresh meats always seem to help... Finally, slight increases in rear ride height help to transfer weight aft so if your car is lowered too much it won't hook up as well. We found that rear ride height had a significant effect on forward bite in the lower gears, you just have enough power to make it an issue in higher gears...

The ride height and camber will hurt cornering speed a little bit, but with your power you can more than make it up on the straights... One last thing about forward bite, if you get it to hook, you will transfer more weight aft, which will let you put down more power which will hook it better. So apparently small improvements get multiplied and good things can happen fast.

I wish I had your problem....

mdk

great response, I only have 1 degree of negative camber in the back and plan on adding more negative camber front and rear to allow my slicks to last more than a weekend. I do plan on increasing the ride height in the rear(it is low), and my tires have to many heat cycles on them, I dont want to loose cornering speeds(thats where all the fun is at!), and not much of a fan of wings. Fouth gear wheel spin over 100mph can get tricky for newbies.

drivinhard

must be nice

I would think a pair of fresh 345 A6's (that's a LOT of stick) would hold up to 600 RWHP.

got any 18" wheels that'll fit that 345 size? more sidewall helps in a straight line...

sgsvette

I'm pushing about the same RWHP, but I run on true slicks, not DOT"s. Although I have slight wheel spin at corner exit, I have found that by going to a higher gear (third instead of second) you won't spin the tires and you really don't loose any time because you are getting the car hooked up. It will feel slower, but look at your lap times and that will tell the story. You might have to change your driving style a little if you are a hard braker to let the car roll through the corners more.
All previous posts will also help.

ajderzie

You may want to consider switching to R6 (roadracing tire) instead of the A6 which is an autocross tire. I believe the R6 is intended to function well at higher temps than the A6. If you think about it it makes sense since autocrossers spend long periods of time waiting for their one minute run. I'm wondering if this is the reason your tires spinning.

Another solution is to come out of the turn in a higher gear since you have so much power. You might actually be quicker since you will probably pull hard with that much power, wont have to upshift and your tires will likely stay planted.

Last choice is to actually buy real racing slicks, not DOT tires. The level of grip is way higher but you will wear them out in a day or two. A big waste of money if you are doing HPDEs and not actually racing. On the other hand, if there is some plastic trophy or plaque at the end and the event is timed.....

ajderzie

ARGH!!!! You beat me to it! We must have been posting at the same time.

sgsvette

Great minds think alike.

mdk

thanks, I never use second gear, but have tried staying in fourth around the track and that does control the wheel spin on the short straights but slows my exit speeds. I am wondering if my transmission gear ratio (Z-51) is the cause.

longdaddy

you can switch to a lower final ratio, which will decrease the torque in the lower gears but will allow you to stay in them longer.

your transmission and rear drive gears are optimized for 400hp (500 if you have c6z). there is a limit to how much power you can make stick in a short gear before you have to go to pro racing tires etc, sounds like you found it

i am not sure how you can have higher gear "limiting" your exit speed if lower gear does not allow you to hook it up on the straight (not to mention you have to make an extra upshift if you do a corner one gear lower)

increase your entry and corner speeds, that will put you closer to the powerband of a higher gear on the exit. there's more to this than just flooring it on the straights...

John Shiels

You cannot just slam the pedal with 600 hp coming out of a corner anything will spin. Your pedal control will be the best help until the car is straight. You don't want more than 1.5* in the rear. What tire pressures are you running?

How many heat cycles do you have on the tires? Can't be that many if your spinning them? New to cords is ever so small amount of rubber!

mdk

tire pressure around 28 psi. I don't pit in off a hot lap and measure temps


heat cycles around 60 rear
I understand throttle control coming out of the corners, it's the tires breaking loose down the straight as the rpm climbs, the car has F.I. thanks for your input.

JimbeauZ06

You can probably drop two to four pounds starting pressure on the rears depending on outdoor temps. 60 heat cycles sounds kind of high too.

John Shiels

60 heat cycles is a ton of time out of a set of slicks Your tires are lasting a long time. Try to measure them hot.

longdaddy

tires have likely heat cycled out, even if there is rubber left

rbeckham

It sounds like you have more than enough laps on these rears (fronts too probably?) to judge by the tread wear whether your pressures and camber are working for you. You are probably running too high pressures rear, which would certainly be a problem with the torque you are applying to them, and too high in front would make it really squirrelly. Remember pressures go up a LOT from cold after a few laps. How have they both worn?

BTW - you need R's, not A's for what you are doing with this car.

mdk

front tires are new but I corded them in one weekend, I will get the camber adjusted. I will try the R-6's out next season and stay on top of tire wear, temps and pressure.

brkntrxn

I will be another vote for you to try a different tire compound. With that many heat cycles, those tires are toast.

If that doesn't help, I'd suggest you go to a taller final drive gear. I used to track a 99 Cobra with over 550rwhp and a 4.10 gear. It was a handful to say the least. I eventually went to a 3.55 gear to help "calm" down the car and it definitely helped.

L98Terror

Mike,

I think I may need to get behind the wheel for a few laps to do a full evaluation before I can make any suggestions

Ken