I'll be running Hoosier A3SO4's for the third time tomorrow on my bone stock ITR and was hoping to got some input from seasoned auto-xers. I've been racing on Azenis for 2.5 yrs. and the whole R compound phenomenon is still new to me.

The surface tomorrow will be slick blacktop and a fairly slow, technical course. Plus, it's going to be closer to 100 tomorrow. I've been told by a few folks that Hoosiers grip better with heat and that spraying them is counterproductive. Is this true?

Anyhow, any input would be appreciated. BTW, I'll probably start with 36f & 34r, cold.

-Matt

 

The A3S04s I've found to go faster when I keep spraying them with water trying to get them to stay cool.

When I ran Honda Day last weekend (100+ degrees, surface pretty slippery) with a co-driver in my 1991 Civic Si (2100lbs) and 205/50x15" A3S03s I got consistently faster when I kept them cool. Although you can get them TOO cold too. We started putting wet towels on the tires on our 3rd runs (we had 5 runs total). And the tires locked up on my 1st braking zone.

But the A3S03s are like the Azenis they like to be cool.

 

Pressures should be 45F/R to start and adjust up or down based upon the need for rotation. Spraying them down really helps the S04's and S05's stick longer.

Dave

 

For the people who spray the Hoosiers, at what tire temperature do you begin cooling them down?

 

Just keep them cold. I usally spray them down (fronts) twice. By the time you do the 2nd tire the 1st tire's water has already evaporated. Just spray again.

On cooler days say around 80 degrees or so you might only have to spray them once. Dave would know better since he runs on them more than I do.

 

Sorry, I gave you the wrong pressures. We ran from 52 to 49f and 44 to 46r and adjusted somewhat for the course. The rears you can go up more for rotation.

Dave

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by innocenti &raquo;</TD></TR><TR><TD CLASS="quote">Sorry, I gave you the wrong pressures. We ran from 52 to 49f and 44 to 46r and adjusted somewhat for the course. The rears you can go up more for rotation.

Dave</TD></TR></TABLE>

I'm assuming those are hot pressures.

I ran this weekend and won DS but there were only two entries. My other ITR buddies couldn't make it. I ran lower pressures to see what effect it would have on the already slick blacktop surface. I ran 36-37 all the way around getting decent rotation, but overall grip was compromised. Big mistake.

I think I'll keep it a little higher from here on out.

Lastly, after about 15-20 runs on Hoosiers, does the grip noticably suffer? (I just want to know so I can't blame the tires )

-Matt

 

They'll start to go off at about 25 runs. Around 35 to 40 they fall off sharply.

Dave

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Utilitarian &raquo;</TD></TR><TR><TD CLASS="quote">

Lastly, after about 15-20 runs on Hoosiers, does the grip noticably suffer? (I just want to know so I can't blame the tires )

</TD></TR></TABLE>

40 runs is when they literally puke and die. I had this happen at a ProSolo and it sucked. No amount of spraying the tires or being smooth with the inputs helped, the tires were seriously dead.

I'd be watching the sidewall if I were you. When I was running DS we ran 50-57psi in the fronts just so we weren't laying rim. We ran so much air in the rears that we maxed out our tire gauge, but after to talking to bfitz at Topeka running significantly less air in the rear seems to yield a better result (&lt;30psi in the rear).

 

This whole hot pressure/cold pressure thing is road race terminology. With only 3 runs at big events the first run is as important as any other. So I just start at a pressure and reset to that pressure after each run. In other words, the tire pressures are always the same hot or cold.

Last year for A3S04s we were running 48-51 front and whatever rear pressure made the rear rotate enough (try 48 to start and lower for more stability or raise for more rotation).

A3S05s we are running 44 all-around for asphalt and maybe 46 all around for concrete.

Cooling tires: it seems that everyone has their own ideas here. What works for me is to cool them when the tread becomes uncomfortable to rest my hand on. When I water them I coat the tread area with most attention paid to the outside 1/3 of the tread (the ITR really works the outside 1/3). I also spray the sidewall and gently hit the rim (avoiding the brake rotor and caliper). I spray a few times between runs until the water stops evaporating. Remember that most of the cooling takes place as the water evaporates.

I do not believe that using cold water instead of room temperature makes much of a difference. Here's why:

It takes 1 calorie of energy to raise 1 gram of water 1 degree C
It takes 600 calories of energy to turn 1 gram of water at 100C into water vapor at 100C. So if you lower the termperature of the water from 25C to 5C ( 77F to 41F) you will only improve the cooling provided by that gram by 20 calories the same as just putting on an extra 1/30 of 1 gram and letting it evaporate.

I have seen people soak towels in cold water and then leave them on their tires. They are actually keeping the tires hotter than if they just wet the tire down. By leaving the towel on the tire they prevent evaporation and reduce cooling. It's like leaving the tire in a steam bath!

regards,
alan

 

Thanks Alan. So it is a good idea to spray Hoosiers on our cars. That's good to know because I've got a multitude of opinions and yours seems to contain any legitimacy.

I'm running 205's front and rear if it makes any difference, but would you venture to say that running anything less than, say, 45 up front isn't a great idea. Also, I see your point about running consistent pressures, 1st run or last run.

thanks,
Matt

 

Alan, that's great info to know, thanks for posting. I'll be trying out S05s next year and I was wondering about pressures as well. That's a good point about there not really being hot or cold temps in autox. Just start perhaps 1 to 2 psi below your target pressure before your first run and then just bleed it down to keep it where you want it afterwards. Also, to those who ran both V710s and autox compound Hoosiers, which are more tolerant to heat? (In other words, which overheat and fall off faster?)

 

In an interesting role-reversal, the s05 h00siers seem to handle the heat better than the V710s.

 

I saw most people at national tours this year spraying their a3s05's to cool them mostly dual driver cars.
We ran a3s04's most of the season on a dual driven DS ITR and we didn't seem to need to cool the tires and they performed quite consistantly.

We start out most events at 38f/34r and then proceed to bleed the fronts down to 40 throughout the day. We get 30+ usueful runs out of the tires before we remove them.

Dunno if this helps but I suspect when we show up in Topeka in September with the S05's and if it is hot, we may need to spray!

 

Alan is right on regarding the whole hot/cold tire pressue and spraying theory. He knows his isht about R's. Alan and I compete together at many events in WDC, PA, NJ etc... We both spray our tires on the 2nd run of the tires, but we both have co-drivers too so the tires get super hot. I have not done pyro readings on the S05's yet so I don't know if Alan is right running 44 up front on the S05's or if I am right running mine at 49 to 52psi.

I did not notice that the Hoosiers were any better with the heat than the Kumho's. For the R we run 205's f/r and Hoosiers we're running 225's front and 205's rear. I have never really felt that the Kumho's go "off that bad as long as you are spraying them in between runs.

Dave

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by innocenti &raquo;</TD></TR><TR><TD CLASS="quote">I have not done pyro readings on the S05's yet so I don't know if Alan is right running 44 up front on the S05's or if I am right running mine at 49 to 52psi.</TD></TR></TABLE>
I've done pyro readings on the ITR before (not on S05s) but I'm still trying to figure out how to reach the optimum pressure by increasing/decreasing it based on the temps. Do you guys raise the pressure if the outside is getting hotter compared to the middle until they are both as similar as possible? (On the same token, do you lower pressure when you notice your center is hotter compared to the outside?) Or do you just raise/lower pressure depending on the amount of roll you are seeing, regardless of the tire temps? I've always been curious to the best strategy in figuring out tire pressures when autocrossing a stock fwd car – mainly concerned with the front tires since the goal there is to get the most possible grip out of them.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by innocenti &raquo;</TD></TR><TR><TD CLASS="quote">For the R we run 205's f/r and Hoosiers we're running 225's front and 205's rear.</TD></TR></TABLE>
I take it this mostly because of the bad gearing the 225/50 series Kumhos give. Is there a noticeable difference in grip between running a 205 v710 vs the 225 hoosier, or you can't really tell just from behind the wheel?

Thanks for the info.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hracer &raquo;</TD></TR><TR><TD CLASS="quote">
I've done pyro readings on the ITR before (not on S05s) but I'm still trying to figure out how to reach the optimum pressure by increasing/decreasing it based on the temps. Do you guys raise the pressure if the outside is getting hotter compared to the middle until they are both as similar as possible? </TD></TR></TABLE>

To me pyro readings on a car where you cannot change camber are not going to be that useful. I would wager that on a stock ITR, no matter what you do with pressures the outside is always going to be hotter (both front and rear). The only thing the pyrometer might tell you is if you are way way too high on pressures. But I suspect that's not gonna happen until you get to 65psi+.

If, on the other hand you have a reasonable amount of negative camber then the pyrometer becomes a useful tool. If the middle is too hot then go down in pressure. If the sides are too hot then go up in pressure.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hracer &raquo;</TD></TR><TR><TD CLASS="quote">
I take it this mostly because of the bad gearing the 225/50 series Kumhos give. Is there a noticeable difference in grip between running a 205 v710 vs the 225 hoosier, or you can't really tell just from behind the wheel?
</TD></TR></TABLE>

Yep, the 225/50/15 v710 is just too damn tall. The Type-R gearing is really bad with it. Also, I was told, that the 225/50/15 v710 weighs a staggering 5lbs more that the 205/50/15 v710. I am not sure how accurate that is but it certainly would explain why the car accelerates so poorly with the 225 Kumho.

The turn in with the S05 is far superior to the v710. Not sure if the overall grip is any better but the Hoosier works for me and the Kumho does not.

I will be running S05s at all important events but the 205 Kumho all around for fun since it lasts longer and is cheaper.

regards,
alan

 

Actually, I just looked at the TireRack website:

205/50/15 Kumho v710 18lbs
225/50/15 Kumho v710 24lbs !!!!!!!!!!!!!!!!!

205/50/15 Hoosier A3S05 19lbs
225/45/15 Hoosier A3S05 19lbs

The 225 Kumho is also 0.9" taller than the others.

So the Kumho 225 really is unsuitable for the front of a TypeR

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 00R101 &raquo;</TD></TR><TR><TD CLASS="quote">The turn in with the S05 is far superior to the v710. </TD></TR></TABLE>
This is also the main thing I noticed when comparing v710s to RS04s on the track. Looks like it's the same in autox.

I also saw the tire rack specs on the tires before. There is a difference in weight between the 225 and 205 v710s, but I only measured it to be about 3.5 lbs on a scale. Still, there's a difference (and there should be, since the 225 is bigger in both width and diameter.) As far as the 205 vs 225 on the front of an ITR, not long ago I did about 20 runs on a test&tune course at an evo school and found that running 205s up front pretty much yielded identical times to the 225s. The car (power) is noticeably more lively on the 205s and it's clear that whatever extra grip the 225s might provide is given up in the gearing. In comparison, the car is just lazy in 2nd gear on the bigger tires. On an ITR, the 45 series 225 hoosier is the way to go for max speed simply because of the gearing, if nothing else. It has virtually the same diameter that the 205/50 tire has, but is two sizes wider. And Hoosiers are very wide to begin with.

Thanks for the reply Alan. Good stuff.

 

I agree with Alan regarding the S05's vs the V710's turn-in response. The S05's are the superior tire. The v710's will be on our car for regular events due to cost/wear.

Dave