THSCC Forums

Quick question,
If it rains on race day, can/should I use my street tires (Azinis) instead of the Hooziers? Can I switch mid day if it starts raining or clears up?

_________________
Colin O'Connell

'94 BMW NASA SPEC 3
'02 F350 tow vehicle (not bad for a tow vehicle)
'97 Miata STO (autoX and sunny day spoils vehicle)
'97 BMW 328i (loaner to the kids when their cars don't work vehicle)
'05 Toyota Highlander

I assume you mean autocross, right? If so, yeah, you can switch during the day.

As for whether to switch, well, that's situationally dependent. If you are pretty sure the schedule and weather are going to yield you dry runs later, it's probably not worth changing to rain tires since you're gonna be faster later anyway (and changing tires in the rain sucks).
If you already have dry runs in, then it's just a matter of if you want some rain practice with your rain setup.

Now, how much water makes the switch a requirement? In most cases, you need to have some standing water at least somewhere to make the switch worthwhile. Some racers will tell you you need to have a *lot* of standing water before the switch is worth it. If the water isn't just standing but is moving, you definitely want rain tires on. Yes, your Azenis qualify as "rain" tires in this case.

You'll also want to run a reasonable amount less air pressure in your Azenis in rain conditions than you would in dry. That will help them build heat as well as stretch and thus grip more under the lower grip conditions.

I'm sure others will chime in with some good suggestions. I wlil say that you'd be very surprised how much you wet you *can* effectively drive on R-compounds. Most people tend to think just because the grip level is greatly reduced on them that their street tires will be better, but in reality unless there's standing water, you're probably really not that much better off.


--Donnie

Track or Autocross the decision process is more or less the same:
assumption: the softer tire will always give more grip and be quicker
up to its ability to drain water so try and stay on the Hoosiers for
as long as possible.

to switch or not to switch: if you can see grain in the aslphalt/ or
concrete on the driving line, then the line in not saturated
this is damp but not wet -go for slick or track tire. You wil still have a considerable amount of grip. licks can run on grainey surface just avoid the shiney spots.

If there is no grain showing (shiney surface) but can't see standing water, then the track surface is saturated and considered wet or intermediate
tire contitions. f there are groves left would still try and run the Hoosiers
if the standing water is not on the racing line or in critical areasGiven
the choice you have. The softer tire will better grip what edges it can get too.

If there is standing water pick a tire with full rain groves, the softer
the better. Azena's not have full rain groves so how much water
they can drain will need to be tested. They will lift my corvette off
the grould in anyting over a quarter inch (when new) so they
are less than a intermediate tire but more than a groved DOT tire.
Drive on the Azena on the street in the rain and get a feel of how
much water they can drain. When you exceed that limit
An RA1 at full tread would be needed or a proper DOT rain tire like
the dirt tracker or Rain version of the Hoosier RS...($200 a pop for
my Scirocco)

These conditions change someimes minuite by minuite so be preparied to switch the very last minuite. walk to the track stick your
finger in the puddles do what you need to do to measure track
conditions and make the best choice of what you got avaiable.

_________________
Mark Vitacco
THSCC TT Chairman
mvitacco@bellsouth.net