I went up to Deals Gap today to do some fast driving. This is an extreme 11 mile streach of road with 318 turns that you rarely get to fourth on. Armed with my infrared pyrometer and tire pressure guage I decided to see how my new Kumhos fared up and to fine tune the air pressures. I set up my AGX's so that the car was near perfectly ballenced. I could predict or make the car understeer, oversteer, 4 wheel slide and use it predictably to my liking. After some heavy driving I noticed the front tires started to lose traction.

I pulled over to check the tire temps. I had the tire pressures set perfectly so that the temp across the tire was pretty even. The inner part of the tire was within the desirable 10 degrees F from the outer part. However the inner fronts were at about 145F at the surface whereas my rear tires were at about 125 at the hottest section.

My questions are: was the sudden loss of front traction due to my tires overheating? Did this damage them? How should I go about preventing this in the future without effecting the cars balence too much?

 

i wouold think you would get slightly better traction with the tires heated up.

 

I think you can get "harder" tires (read the UTQG for that) so they can hold up longer.
I run regularly my Lude on the "real" track (no drag strip, more like F1 tracks) and i found out there are about 3 stages for street tires:
* cold -> squeal and lose traction quickly
* nominal -> predictable, "smooth" sound
* too hot -> lose traction and make a LOUD squeal, very specific, with small "interruptions" - not a smooth sound
Most street tires cannot take the heat of continuous hard driving. The harder the compound is, the longer they last, usually. 300 AA A tires may last longer than 150 AA A, but they take longer to warm up to nominal temperature, that's a fair trade-off. At the track i usually run 1 - 1.5 lap to heat the tires before i take the car to the limits. Then after 8-10 laps they get too hot and make that "other" sound when pushed to the limits, that's the signal for me to slow down and make a pit stop...
I hope i could help

Question: how did you set up your AGX's ? '4' all around ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by racerx &raquo;</TD></TR><TR><TD CLASS="quote">I pulled over to check the tire temps. I had the tire pressures set perfectly so that the temp across the tire was pretty even. The inner part of the tire was within the desirable 10 degrees F from the outer part. However the inner fronts were at about 145F at the surface whereas my rear tires were at about 125 at the hottest section.

My questions are: was the sudden loss of front traction due to my tires overheating? Did this damage them? How should I go about preventing this in the future without effecting the cars balence too much?
</TD></TR></TABLE>

The front tires get much hotter because they are both turning the car, putting down the power, and most of the braking forces are also exterted through them (weight transfers to the front under braking.) The rears are cooler because they are pretty much just along for the ride.

Street tires normally get greasy when they overheat. When they get overheated you will see decreased traction, increased braking distances, less predictable handling, and accelerated tire wear. It does not necessarily damage the tires, but it certainly can shorten their effective lifespan. If you heat cycle the tires to this extreme enough times, the tires will often eventually begin to have lower grip limits - even when cooled off again. You can prevent this by not driving the car soo hard or taking long breaks to allow the tires to cool before they get overheated.

Andrew


Modified by aklucsarits at 2:58 PM 5/10/2004

 

are these with Kumho 712s? Kumho MX? VictorRacer?

 

They are Kumho Ecsta 711's in a 225 on stock wheels. I've got Sportline springs with the AGX's set to 4 for the front and 3 on the rear. The camber on the front is -.5deg with caster at -3.5deg (1deg more than stock). The rear is at -1deg camber with zero toe.

If I don't drive the car hard then I may as well sell all the go fast parts and build a show car. Thats not me though. The thing is that I only pushed the car really hard for the equivilant of 1 lap at a time. It was about 80deg out and it'll still get warmer as we get further into summer. So it'll only get worse.

Jesus_FR: Since it seems my tires shouldn't crap out so soon, do you think that it has to do with driving style? In many cases understeer is unavoidable so I just feather the throttle until I can accelerate hard without going into the ditch. Would setting the car up to oversteer, like when adding a rear anti-sway bar, help keep the front tires cooler due to their needing to countersteer instead of slide?

 

Thanx for the settings
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by racerx &raquo;</TD></TR><TR><TD CLASS="quote">
Jesus_FR: Since it seems my tires shouldn't crap out so soon, do you think that it has to do with driving style? In many cases understeer is unavoidable so I just feather the throttle until I can accelerate hard without going into the ditch. Would setting the car up to oversteer, like when adding a rear anti-sway bar, help keep the front tires cooler due to their needing to countersteer instead of slide?</TD></TR></TABLE>
I think setting '4' in rear AGX's could promote a bit more oversteer. Make sure you have some real downforce (a good wing) back there because you really don't want the rear to go away: when it does, you've got 75% chances of spinning / going off road (and hitting whatever is in the path), because it's a FWD. I currently miss a wing and the rear of my car tends to "float".
Also at various track days i had the opportunity to compare quite a few tires on various Honda's (ITR, CTR) and other japanese sport cars. I found out that softer tires like Toyo T1's or Bridgestones often die after 1 day of hot lapping - new in the morning, *very* dead in the evening.. the softer rubber overheats and *melts* ! Of course it depends on temperature. On a sunny day in February, my tires were too hot after about 6 laps on a 2.4km track, that's about 14km (8-9 miles). And they are quite hard. For a comparison, on a RWD car (Silvia S13) new tires die in about 4 laps of drifting...
As for driving style, drifting (by promoting oversteer) will only kill your tires faster. If you really want to drive hard for a long time, get yourself a set of slicks they're really worth it. Pick hard compounds.
I have great expectations for my current tires (Yokohama Parada's) they seem to be very hard, they may last a bit longer. But remember that usually street tires are not meant for continuous hard driving ! I think Yokohama makes streetable "slicks" under the name AVS 032 or something.
Ah and try to get a "clean" path around corners, getting to the limit of your tires, especially the fronts, without exceeding it... It helps a lot ! If you feel them overheat, just slow down for about 1-2 miles, they'll cool down a bit. Cleaning your driving style can make you go faster for a longer time...
Hope i could help

(edit) FYI i have a '94 Lude "SI" 4WS, the 4WS helps a lot by limiting understeer.

 

Have you ever gotten your tires cured? I think thats what its called. Its supposed to help the tires last longer for driving like this. How well does it work? Do you think a jump from a 300 treadware to a 400 would help me or does it differ too much between manufacturers? Thanks, you've been a great help

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by racerx &raquo;</TD></TR><TR><TD CLASS="quote">Have you ever gotten your tires cured? I think thats what its called. Its supposed to help the tires last longer for driving like this. How well does it work? </TD></TR></TABLE>
Ah i learn something there. I think you mean a kind of forced heat cycle, right ? That's a good idea, i'm not sure about street compounds though.. i'll try and ask around.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by racerx &raquo;</TD></TR><TR><TD CLASS="quote">Do you think a jump from a 300 treadware to a 400 would help me or does it differ too much between manufacturers?</TD></TR></TABLE>
Good question. I'm in the process of determining those differences between manufacturers, but since i only bring my car to the track not quite so often you see my problem here... i'll know more about that at the end of this month, after my next track day. I took the bump from 220 treadwear to 300, i'll see if it's really better. But i suspect the answer is: every manufacturer has his own compound, and the '220' from Sumitomo was *really* hard.. (actually i heat cycled them at the track ) i dont think the 300 from yokohama will be harder, who knows.
Also on the UTQG you have a heat resistance letter, IIRC it's treadwear/traction/heat, so 300 AA A is very good traction but 'just good' heat resistance. I wonder if there are any street tires that bear a 'AA' heat mark.
I'd really like to try out 400 rated tires, but they are kind of difficult to find around here I'll be very interested in knowing about any experience you have about that though.