Cups on R6's
12-20-2013, 12:05 PM
#16
Rennlist Member
Thread Starter
I've seen the 285/30/18 R6's blow up there several times on the banking. Hoosier issued a statement warning about the potential for failure on banked tracks and suggest using a cold starting pressure of 40 or something ridiculous like that. Cup cars come with a 680 series rear tire to eliminate that issue. The taller tire holds more air which equates to a higher loading capability. Cups with their large wings place a heavy load on the outside rear tire when on banking especially at 150+ mph. We take camber out of the right side (CCW) so the tires don't sit on the inner edge, and run a little more pressure on the right rear to help carry the load...
12-20-2013, 12:33 PM
#17
Leigh,
On the camber, I'm running quite a bit less than slicks, something like -3 to -3.5 front and -2.5 to -3 rear. Tire wear has been pretty good and even.
As for some other posts about tire failures, I have not run an "rovals" so no experience on the high banks. However, the logic about the 30 profile tires having issues compared to a 680 slick makes sense from an engineering sense. The overall diameter is about 1/2 inch smaller, so that's quite a bit less volume (don't feel like running that calculation, but probably 30-40% less volume).
I'm going to try the 40 profile A6 this season to see how that works. I'm hoping the cold-hot pressure ride will be a bit lower with the extra volume. Going to keep the 35 profile on the front as front grip, wear and pressure control has been great (then again, it's not like the front are working very hard.....)
BTW, no one can use any of my setting or ideas if you are racing against me!
On the camber, I'm running quite a bit less than slicks, something like -3 to -3.5 front and -2.5 to -3 rear. Tire wear has been pretty good and even.
As for some other posts about tire failures, I have not run an "rovals" so no experience on the high banks. However, the logic about the 30 profile tires having issues compared to a 680 slick makes sense from an engineering sense. The overall diameter is about 1/2 inch smaller, so that's quite a bit less volume (don't feel like running that calculation, but probably 30-40% less volume).
I'm going to try the 40 profile A6 this season to see how that works. I'm hoping the cold-hot pressure ride will be a bit lower with the extra volume. Going to keep the 35 profile on the front as front grip, wear and pressure control has been great (then again, it's not like the front are working very hard.....)
BTW, no one can use any of my setting or ideas if you are racing against me!
12-21-2013, 07:56 AM
#18
Burning Brakes
Cook,
Did you have to swap wheel halves to go to those DOT's? My understanding is the tire shapes are different and some are having to change all their halves to the tire does not rub on the inside.
Did you have to swap wheel halves to go to those DOT's? My understanding is the tire shapes are different and some are having to change all their halves to the tire does not rub on the inside.
12-21-2013, 08:25 AM
#19
Rennlist Member
Why not put in a restrictor to reduce output
I had 150lbs of ballast plus a LOT of extra fuel. With the new sequential rule I'd have to carry 225lbs and if I ran minimum fuel as I should I'd be well over the 250 lb. maximum ballast rule. I'm quite uncomfortable bolting on that much weight in the car... If I run ST1 I don't need to add any weight as my ratio works out to 5.87 with 5.5 as the minimum. Not sure how I'm going to catch the Corvettes down the straight... I already run a flat wing. I might be able to lose some weight and get closer to 5.5 it would help....
12-21-2013, 08:27 AM
#20
Rennlist Member
It is not the tire shape that is the issue. It is the lack of camber. To pull the camber out you need to stand the tire up more. I ran the 315's as well and changed from 9.5's and 1.5's to 10's and 1's.
12-21-2013, 11:25 AM
#21
John,
I'm running the stock, late 6Cup BBS rim. However, I do have the full adjustable suspension links and we can play with track width (along with wheel base) and camber independently. When I say the 315 is tight, I mean it is tight. Their might be 1mm of clearance when sitting static, but under load the way the suspension move and the tire flexes, no rub.
For the 40 profile, I think I will have to go to the 290 since Hoosier's 315/40 is over an inch wider than the 315/30 (nice job making the "sizes" not align to the actually tire size.....).
Car will be over at Eric's in about a week for a nut and bolt if you want to check it out. You'll see a very rough warrior, no high-brow show car like Brant's!
I'm running the stock, late 6Cup BBS rim. However, I do have the full adjustable suspension links and we can play with track width (along with wheel base) and camber independently. When I say the 315 is tight, I mean it is tight. Their might be 1mm of clearance when sitting static, but under load the way the suspension move and the tire flexes, no rub.
For the 40 profile, I think I will have to go to the 290 since Hoosier's 315/40 is over an inch wider than the 315/30 (nice job making the "sizes" not align to the actually tire size.....).
Car will be over at Eric's in about a week for a nut and bolt if you want to check it out. You'll see a very rough warrior, no high-brow show car like Brant's!
12-21-2013, 02:16 PM
#22
Rennlist Member
Thread Starter
Well, you're right, I hate it but yes that would work. I'm not sure I'm that desperate to stay in GTS as the ST1 ratio works pretty well. At Miller we're all racing together anyway so the run group won't change. There are a pile of newer cups at Miller now so the gang will either move into ST1 or into GTSU.
