Full slick rain tires in non-Prepared classes

[blindsidefive0]

The rule:
"Tires shall be of radial construction and DOT approved, with no under-tread showing (for safety reasons), and either be
listed in the Tire Guide or be available in three or more rim diameters."

This exact text appears in the Showroom Stock, Street Touring, and Street Prepared sections of the rule book.

It appears fairly clear that a full non-DOT slick tire will boot you straight to Prepared. Without getting into the merits of whether this actually makes sense from a competitive perspective, my question is: is it permissible to run a non-DOT full wet or rain tire for practice? I believe there was some debate a while back about running slick scrubs for dry practice, and maybe the result will be the same, but I wanted to bring it up here in terms of wet tires.

Looking forward to hearing people weigh in...

[breakaway500]

I believe the whole issue with allowing race only tires (non DOT) on street class cars,is safety. The race only tires would allow elevated levels of performance for most cars,and therefore should require elevated levels of saftey protection,which is required for Prepared/Formula classes. (rollcages,harnesses,firesuits etc)I believe the rules are in place for any time a car is being used on track,so practice time would require the same compliance to class rules. (that's my two cents worth of weight..)

[962porsche]

if it's a rain tire that to is the same as a full slick when it's dry .
there are other reasons why a slick tire is not the best on your car . 1 is if the suspension is not set up for slicks then there is not a big gain from them .
let me try and explain it .
say your running 300 lbs springs on your car with a performance street tire or dot R tire . your car has good grip in the turns and they work good with the 300 lbs springs . then you slap on a set of full slicks that are twice are sticky as the R-tires or performance tires . you will find your car will not go that much fast per lap as it did with the dot tires . the reason is your suspension is not set to handle the extra grip from the slicks . tires and suspension work as a package .
my VW GTI suspension is set up for full slick tires last year i took it to the track with performance street tires and it was like driving on ice . i had the 500 lbs front springs and 350 rears in the car when i should have had a 300 to 350 front springs with the the shocks valved to match the spring rates .
would you be turning a faster lap with the full slick yes some what . but only about a second or two at the most . so because your running a non prepared class it does not let you run a full slick . they are not dot tires . to make the full slicks work you would have to change your suspension to handle the extra grip you will get from them . this will move you out of class . so there is no real reason to want to run full slicks . just get some good dot R's and have fun .

[brucesallen]

I certainly agree and give this explanation: Racing slicks are rigidly square and flat faced. So the suspension must be firm and tight enough that it can hold the tire flat on the pavement under high G load. No more that 1 degree of camber setting with bias ply slicks. Street-based suspension will allow lots of camber change in corners. This means that slicks will be riding on a narrow edge in the corner, not full contact or if you put in 3 degrees of camber you will be running on the inside edge when going straight and you can't brake. So DOT tires are rounded. This means that as the camber changes with load you still have more than half the tire in contact with the road.

[dradernh]

Hoosier makes a DOT-labeled rain tire. Can you use those?

[breakaway500]

"Hoosier makes a DOT-labeled rain tire. Can you use those?"

Like these?



Sure,why not? It says DOT on it... (Hoosier has this size and a few other sizes on sale for $115-135) https://www.hoosiertire.com/discontinuedtires.htm

[eastcoastbumps]

A lot of talk about why you should or should not, but no real answer on whether you can or cannot. I would see no reason why you couldn't. You'll need to swap to a different tire for time trails, or install a cage, harness and bring your race suit to run those tires on your stock M3 in PB.

[breakaway500]

"but no real answer on whether you can or cannot.."

My belief is any time your car is on track at a COM event,practice or time trials, the rules are the rules. You could not "practice" with your Prepared class car without your firesuit,and you could not "practice" with your street class car using non DOT tires..or use nitrous,or run an outdated helmet..etc. One standard for all track time. Is this not so?

[962porsche]

i have the same tires yes you can use them they are what is called a R compound tire taged as DOT there for if you can run a regular R-compound dry tire them yes you can run a R-compound wet tire .

[blindsidefive0]

Thanks for all the responses. Mark, I think you are right in that this wouldn't be allowed in practice or TT, unless I had all the proper Prepared-class safety gear, which I understand to include a roll bar, single layer fire suit, and arm restraints and/or window nets (which seems to be loosely enforced in non-convertibles).

I agree that it is legal to run a DOT-R wet tire like the Hoosier Wet in any class (I've done this before and will likely run it again). The real reason I threw this question out there is that it's much easier and cheaper to get slick scrubs from racing teams. For instance, JPJP from the bimmerforum will sell take off Conti full-wet slicks for $400 shipped. No one seems to sell used DOT-R wet tires in any sort of condition worth paying for. And while I understand concerns about running a full slick in a non-prepared car in the dry, the issues with the suspension/body roll/McPherson strut mid-corner camber changes/etc. really don't come into play with wet track g-forces of well under 1.0, even in the damp.

Now for the dry, I would question whether running a full slick is that much more of a performance mod (i.e. requiring the club to mandate the prepared-class safety gear) compared to the plethora of mods allowed in Street Prepared (where none of the above-mentioned safety gear is required), especially considering how much grip you can get anyway from a DOT-R tire like the Hankook z214 c91 (some national-level time trialers have actually run this INSTEAD of a slick because of how fast the tire is). I'm not saying that these safety features are a bad idea (I seriously contemplated putting in a roll bar this year, despite the M3 being my primary street car in the winter), and it may make sense from a competitive standpoint and from the spirit of the Street Touring/Prepared classes to not allow slicks. However, for example, from a safety perspective I would think something like a built e46 M3 engine swap into an e30 318 (legal modification in Street Prepared) is significantly more dangerous than that same e30 running a full-slick. It should also be pointed out that not all slicks are created equal - it is my understanding that some slicks like the Conti Challenge slicks are really just non-DOT versions of DOT legal tires (e.g. the Conti slick is really just an R6 without the 2 tread lines).

For reference, 2 other national-level clubs address this in different ways. NASA TT does not require any additional safety equipment when running a full non-DOT slick. Instead, from a competitive perspective, it assesses all non-DOT tires as over twice the points of the stickiest DOT-R tires (except for the strict power/weight classes, which are likely, but not required, to come with said safety equipment). This effectively keeps almost all competitors from using non-DOT tires, although I know for a fact that last year's TTB national champion has practiced on full-slicks in his c5 base model vette street car (data shows identical grip/lap times to an A6, just lasting for the entire session). The other club is CASC, which requires similar safety equipment as COMSCC prepared classes if either the vehicle has acquired 25 performance points worth of mods (for reference, shocks and springs would be ~5 points), or the driver is running a non-DOT tire that is not, for all intents and purposes, a non-DOT version of a DOT-R tire (like the Conti/R6 example above).

I'm not really suggesting anything at this point (but may consider throwing out some proposals at the end of the season)...just curious on the discussion...

[962porsche]

the big reason you don't see DOT wets for sale used is that they go from full wets to intermediate wets as they get used and all last as a intermediates right down to nothing .
do the dot wets work hell yes i turned the 3rd ftd at tremblant in the pouring rain with a very slow 8V 944 . when your flashing your lights to have the AWD cars get the hell out of your way it tells you that your getting great traction . the same at LRP 2nd fastest , VIR 3rd fastest and beaverun 4th fastest in the pouring rain .

as for redoing the classing . good luck ! i like the way nasa classes there cars it works and works good but you will never see comscc doing that . i have never like the way cars are clased with comscc . they look at what your car could do if you spent a crap load of time and money insted of classing the car to how it's built at the time .
in some classes if you add a roll cage to be safe you in fact just add weight to the car and make it less competitive .
i'm building a 944 with the drive line from a 968 3.0L 6 speed . i will not put a roll cage in the car just because of the weight it will add . my fealing is if you add a full cage you should be able to gut the interior .
right up a rule change and give it to the BOD .

[dradernh]

I agree that it is legal to run a DOT-R wet tire like the Hoosier Wet in any class (I've done this before and will likely run it again). The real reason I threw this question out there is that it's much easier and cheaper to get slick scrubs from racing teams. For instance, JPJP from the bimmerforum will sell take off Conti full-wet slicks for $400 shipped. No one seems to sell used DOT-R wet tires in any sort of condition worth paying for.

Boths sets of my Continental wets are rebranded Hoosiers from Jean-Paul Jean-Paul. The last set of intermediates was $325 delivered, with the usual great service. He really is a terrific resource. For those who haven't used him, he can be reached via this thread: http://forums.bimmerforums.com/forum/sh ... 34&page=35, and at jphanna6@yahoo.com.

Earlier this year, I sold a set of hardly-used Hoosier DOT-R Wets in a size I no longer wanted to Dan Croteau. IIRC, I got $400 for them, so it is possible to occasionally find a set for not too much.

[brucesallen]

More issues to the fire:
Non-DOT tires (slicks) can be half the weight since they don't have to have the impact protection of street tires. So even if the compound and shape don't help you, the weight reduction is significant.

[naschmitz]

I ran non-DOT Pirelli Grand Am scrubs in SPA. During the time trials, I put on my Hoosier R6s.

The Grand Am scrubs were much lighter than the Hoosiers, but a second a lap slower at NHMS overall. Over a 25min session they were much more consistent than the Hoosiers and only grew 5-6 psi instead of 10-12 psi that I often see with the Hoosiers.

They weren't bias plys, so similar car setups worked for both.

Wonder if NEW Pirelli slicks would have been faster than Hoosier A6s?

[brucesallen]

Over a 25min session they were much more consistent than the Hoosiers and only grew 5-6 psi instead of 10-12 psi that I often see with the Hoosiers.

use nitrogen to minimize pressure rise.