View Full Version : z214s in the marbles


robertm
05-06-2008, 10:36 AM
Since the last race something has been bothering me and I can't put it to rest. I had two offs in one race at my home track. The first was in a place I've only once ever gone off (that was on a corded tire). The other was in a place I haven't lost it in years.

First off was going into or up rattlesnake. I was off the brakes, on the gas and turning up the hill. I hit the marbles and literally shot off the track.

Second off was in Big Bend. I was one car length off apex (just passed somebody I think) hit the marbles and hugely flew off track. So fast the car actually tank slapped a couple times before I caught it.

The problem is, both places I went off in the marbles, I've literally been probably 50 times before without incident.

The only difference between this race and prior experience is the new Hankooks. I'm wondering if it’s possible the stiffer sidewalls (compared to the R6 tires I usually run) are the culprit.

I'm not saying with the R6 tires I wouldn't fight he marbles, but it’s always been manageable. Both instances with the Hankooks there was nothing to manage. I was on the track then in a split second OFF the track.

So short story long, anybody notice much difference in the marbles between the Z214s compared to R6 tires?

Only other thing I can attribute this too if others haven’t seen similar results, is tire pressure. I was fighting it all day. It was very cool when the day started and every session got warmer. The three sessions before the race I had to drop 2-3 psi each time trying to get down to 38psi. It’s quite possible the tires still had too much pressure for the race as it was warmer still for the race. I wouldn’t be surprised if the tires were up to 42-43psi during the race as I just haven’t had enough test/tune time on them. Actually, I’m really hoping this is what the problem is and the tires don’t just suck in the marbles compared to R6s. A lot of my best work is done in the marbles :redspot

dmwhite
05-06-2008, 10:45 AM
So short story long, anybody notice much difference in the marbles between the Z214s compared to R6 tires?
i haven't noticed any difference

Only other thing I can attribute this too if others haven’t seen similar results, is tire pressure. I was fighting it all day. It was very cool when the day started and every session got warmer. The three sessions before the race I had to drop 2-3 psi each time trying to get down to 38psi. It’s quite possible the tires still had too much pressure for the race as it was warmer still for the race. I wouldn’t be surprised if the tires were up to 42-43psi during the race as I just haven’t had enough test/tune time on them.
how much does your car weigh?

38-40 psi is a good hot pressure range for a ~3000 lb car...i'd bet 38 psi hot is at the high end of the range for your car's weight and 42-43 psi is way to high...

robertm
05-06-2008, 11:21 AM
i haven't noticed any difference


how much does your car weigh?

38-40 psi is a good hot pressure range for a ~3000 lb car...i'd bet 38 psi hot is at the high end of the range for your car's weight and 42-43 psi is way to high...

Car is 2625lbs with me in it at the end of a race. The Hankook specs say 40 hot. I emailed Jeff over at Hankook and he said 38. He was kind of vague though with his reply and I sort of got the impression he wasn't sure. Surprisingly, he left the company that week so I couldn't pump for anymore info.

What psi do you think I should be running hot? Or what hot temps do you like to see? I don't have my pyrometer temps handy so I can't say what the highest temps were. Really though, I just need more test/tune time on them. Only got about 75 minutes total before the motor went.

Very glad you haven't had the same experiance in the marbles. It was not fun at all.

vinnymac
05-06-2008, 11:29 AM
I run Z214s in a 245/40/17 fitment on my 3,000lb IP/GTS3 car and I've found hot pressures in the 38.5-40.0PSI range work the best.

I tested up to 43PSI and the handling was horrible.

dmwhite
05-06-2008, 11:34 AM
i think 40 psi hot is definitely too high considering that's that top of the hot pressure range that i use (38-40 psi)...

with your car, i would probably start somewhere in the 36-38 psi hot range and fine tune from there with a pyrometer...

what kind of hot pressures did you shoot for with R6's? maybe start there...i found, for my car, that the hot pressure range of the hankooks was basically the same as R6's

good luck!

Z3SpdDmn
05-06-2008, 12:08 PM
Robert,

I was initially running 38-ish in my E30. Per Dave's suggestion at VIR, I lowered it down. Its seeming like 35-ish is my target range. They fall away real quick after that!

My car is just over 2700 lbs with me in it after the race.

BobWright
05-06-2008, 12:13 PM
Man....see my thread below....I am really MISSING my oh so forgiving BFG GForce R1's.....:(

They just stick

Goodrich, if you are out there....WTF ? not one tire to buy in the whole US of A...245/40/17..

dmwhite
05-06-2008, 12:32 PM
Man....see my thread below....I am really MISSING my oh so forgiving BFG GForce R1's.....:(

They just stick

give the hankooks a fair shot...i tested them against BFG R1's and hoosier R6's...i found the C51 compound Z214 to be the better tire and have seen pretty good results with them since i switched...


Goodrich, if you are out there....WTF ? not one tire to buy in the whole US of A...245/40/17..
i know the feeling and it sucks...to be fair plenty of people have had supply issues with hankook also...hoosier is the only one that i've never had supply issues with...

robertm
05-06-2008, 12:37 PM
Thanks for all the input guys. I used to run the R6s at about 36 hot. I think I'll start the z214s at the same cold temps and shoot for closer to 36 rather than 40 psi with good temps across the tire.