Slicks vs R DOT race tires

[homebrew]

After 2 yrs finally took my locost to the track. I'm currently running street performance tires and want to upgrade next year. Does anyone have experience directly comparing the difference in performance between slicks and DOT race tires? At one of my track days I had Dennis Palatov of dp cars ( http://www.dpcars.net/ ) as my instructor. He said if I wanted to upgrade I should go to slicks as the DOT tires took a lot of heat to make them work and the 7 wasn't heavy enough to heat them up properly.

 

Anyone have an answer or suggestion? Thanks

 

Jim

[Kitcat]

Try a search here of "tire".

[yellowss7]

I did my first track day at LOG29 this year and used Hoosier R25B compound slicks. I can't compare them to Dot compound tires but I know that Michael D. who posts on here, uses the Hooiser A6 compound DOTs for his NASA events. He did say that A6's (the autox compound) was better than the R6 (race compound) for the lightweight 7's.

 

I did 5 15-20 minute sessions on New Hoosiers, that were in the softest compound (R25B) and Other than picking up a ton of "other peoples rubber" after I scraped that off there was very little wear on them. Being a trackday novice I can't say that I was pushing the limit on them, but they felt good all day. I definately didn't overheat them.

 

Tom

[d15b7]

hi jim!

 

i'm an experienced road racer; i've been racing for 9 yrs, and doing track events for 16 yrs (yikes!). i typically race two different tin top cars (a Ford Probe GT in NASA PTE class (or SCCA ITS if you prefer) and a Honda Civic in ST2 class). both of those cars i run on DOT R compounds (the Probe on Toyo RA-1s and the Honda on Hoosiers). my Super Seven is typically my 'fun' and vintage racecar; it's got a race prepped crossflow motor in it, and has all suspension mods to support an E Production race seven. the engine should have been dry-sumped, but instead i run a wet sump, with a fully baffled race pan.

 

anyway, here's the point i wanted to bring up -- when i run slicks on the Seven (usually goodyear 430, 6.5" front and 9" rear on 13" wheels), it grips like nothing else i've ever driven! the braking and cornering is unbelievable; in fact it takes some getting used to in order to 'believe' that it can corner and brake at those levels..... but, here is the big 'but' -- i've had TONS of trouble keeping oil pressure up when running the slicks; huge drops in pressure, all the way to 0 psi for a second or more on hard corners (especially right turns, and especially worst when cornering and braking at the same time). i tried all manner of things, and now currently have an accusump plumbed into the oil system (big remote HP4 filter, big oil lines, and a decent size oil cooler, and a mechanical non-damped oil pressure gauge). the accusump keeps the oil pressure from dropping below 30 psi (you can see the gauge go down from about 65 psi in a corner to 35 or so; it slips down smoothly, and then will hover at 35 for a sec, then climbs back up to 65 again). this is not 'good', but is sort of kinda 'livable'.

 

when i run R compounds, i see much less dips in pressure; with the accusump, i might see the press drop to 50 psi for a half sec, and then shoot back to 65. this is much better! with street tires on it (i vintage race it on an old old set of little 185 street tires; this keeps me slowed down enough to have some fun with the other guys!) i never see the oil pressure budge.

 

the long and short of it is this: if you are a good driver, and are pushing the car really hard (as i do; i run it out at 100% -- that's what it was built to do!) and you run full slicks on it, and you are not dry-sumped, then i think you might run into a serious oil pressure problem.... a harder compound Rcomp tire might work out better for you in the long run...

 

oh, and i have a blast running on the rock hard yoko A509 185 street tires! the car drifts and slides around all over the place, and it really feels very 'vintage like'! at Summit Point Raceway, i can run a 1:22.xxx on the slicks, and i have to try very hard to run a high 1:28, low 1:29 on the old skinny street tires. if i ever ran it on a toyo RA-1 (which, if i were going to run on Rcomps, that's what i'd pick, due to price, longevity, and 'fun factor') i am sure i'd run a low low 1:25 or so (with only little to moderate oil press fluctuation).

 

hope that helps!

 

todd

[yellowss7]

Ditto what Todd says re: the Dry Sump. My Rover K series is dry sumped and the guys in the UK strongly advise not running slicks without one for the K. Guess it depends on your engine. I understand the Duratecs don't suffer the same issue.

 

Tom

[homebrew]

Thanks Todd,

 

This is exactly the info I was looking for and then some. Hadn't considered the possible issue with oil pressure. If I do upgrade the tires for next year I'll definetly keep an eye on the o/p.

 

Jim