Understanding Tire operating Temps?
 

I was perusing 15" tire options and looking at the specs on these:

Sizes | Maxxis Victra RC-1


And I noticed the "operating temperature" is 140 deg to 210 deg.

I was thinking that it would be a very bad idea to run these on the street. So I looked up this spec for my current tires (Toyo RA1) and it is similar.

The RA1s are fine on the street if I dont push it when its cold and I never drive the car in the rain intentionally since its a 3rd pleasure car.

What does the operating temperature mean? Is that just the optimum grip temp? Is that given so you can determine if your track set up is getting the tires in the right range? Or is there more to it.

TIA

"Optimal" is the way to look at it. They are giving you the temperature where the rubber really starts to work. You don't want to go over as the tires become greasy and then can blister and chunk.

Also most truly high performance (R compound) tires have a temperature you do not want to operate the tires under. For example: Nitto NT-01s are not recommended to be run under 32°F and at under 15°F they may spontaneously crack. Those temperature points are similar to competitors tires so I suspect Maxxis to be in the same range.

A major consideration for a track day tire is how many heat cycles before the compound "cycles out". The reviews for the Maxxis RC-1s seem to make them pretty bullet proof but you would want to run them for a few months on the street before declaring them as bullet proof as Toyo RA1s or Nitto NT-01s (supposedly the same compound).

Thanks

Yeah I need to get a IR Thermometer and start playing around. I wonder what the RA1s get up to on an 80 degree day just driving around on the street.

I also noticed that non R compound tires do not have an operating temp reported (at least on tire rack). They do mention that extreme performance summer tires should not be used below 32.

I have a tire pressure monitoring system in one of my cars that also gives the temperatures. They generally run only a few degrees above ambient in normal driving. Obviously they would run warmer at the contact patch than where the sensor is located and they would run warmer if they were being pushed hard. Still, I think you'd have to be really working at it to get above 140 on the street.

JR

Normal street driving will not typically get the tires > 140F on a 80F day. I want to say never, but I am sure that someone, somewhere will point out a situation where it could/did happen, but in my experience its certainly not typical.

How do I know this? My Spec Boxster is still street registered and I drive to/from every race/event on r-compound tires. As such, I was concerned about putting heat cycles into the tires on the commute to/from the track. So I checked the tire temps when I got to the track and/or when I got back home and found that there was nothing to worry about. I have checked NT-01's, shaved RA1's, and RR's.

Of course, your mileage (and tire temps) may vary.

Wow - that is an epiphany Mr. Stone, so you are saying that R comps on the street dont reach operating temp so they dont "heat cycle" in normal street driving? I never put the two together. It makes sense but I just always assumed they were still heat cycling and because of this would die before the tread was worn off. Fascinating.

So the next question for me is; How 'unsafe' is it to drive them on the street (warm dry days) vs a high performance street tire? I wonder if there is a significant difference in say emergency/thresh hold braking distances between the two? It would be interesting to see the skid pad numbers between R comps not up to temp and a good HP street tire.

R compound tires have higher grip then your high performance street tires even when "at room temperature". The big thing is they generally don't have treads to deal with water or gravel.
I've driven almost nothing but R compound tires on my 911 for the last 15 years. The big increase in grip costs you a shorter tire lifespan. A cheap tradeoff in my book when you buy a car for its handling ability. Tires are easily the number one thing you can do to improve the handling performance of a car.

Well said Wayne. I have been buying used R comps for about 10 years and I find they age out before I wear them out because I dont put lots of miles on the P car. I was thinking the grip was probably higher than the hP tires.

So to a different question.

New 911s are certainly designed and engineered to take advantage of R comp/modern tire construction and compounds. Has the aftermarket completely figured out how to update our 60s technology cars to work well with modern tire technology?

Judging from Jack Os recent performance against a modern GT car I think yes but his suspension is pretty radical.

Is a simple shock upgrade enough? Probably for most folks but I have read that the 89 and older cars dont have the right camber curves etc. to take full advantage. I think I also heard that you have to make our cars suspensions very stiff to make them work correctly (so the suspension does not move much) with the tires? Does this mean that if you cant or dont want to go to full coil overs and and run super high spring rates we are better off performance wise to use a tire that is closer to what was state of the art in the 70s? I keep getting a sinking feeling that unless you are doing a comprehensive suspension package that is designed from the top of the shocks to the asphalt plus chassis stiffening in some cases you will have better performance just staying stock and not going crazy with rim size/width and super sticky tires?

Maybe this has all been asked and answered have to do some searching.

The temps you are seeing from the TPMS are the internal air temp. This is different than the carcass temp the manufacturer is talking about when they say 140-210F.

That is not correct information. If you talk to the tire engineers at either Toyo or Nitto, they will tell you they are different compounds.

Someone on the internet said they were the same as a guess long ago and it won't go away.

I can't speak to the points of modern cars, as I've never owned one. But, as for older ones, yes the suspension, as well as all the systems should be looked at as just that - a system. Changing one component, for example the torsion bars, will require re-balancing of all the others (sway bars, etc).
Also of major importance is that driving conditions on the street are vastly different than on a track, where you won't find potholes, lane divider reflectors, railroad tracks, gravel and other bumps and hazards. The stiffly sprung suspension that's optimal on a smooth racetrack will buck and bounce on the street, actually making the car perform worse than a softer sprung counterpart.
As for tire temps, my racing buddies go a step further with that and immediately after they pull off track check temps at 3 points along the tread. Inside edge, center and outside edge. This gives them info on inflation and alignment. One must, of course compensate for the dominant turn of any given track. Ours is a clockwise lap, so the left side tires get more abuse than the rights, hence higher temps.
-C

Actually I talked to an ex engineer from Nitto. Taken in context his "they are the same" statement may mean they are identical or they he saw them as functionally identical. Not sure. Toyo owns Nitto and they may use the same compound with a different part number. Also tire compounds are a moving target as they are constantly being developed so they may have merged and diverged over their life. Who knows.
I haven't seen much of a difference in the compound with RA1s and NT01s but Nittos have huge stable tread blocks and are cheaper, and the RA1s have a better tread pattern for water.
Most of the conversation with that engineer was about the treadwear numbers used by different manufacturers. Turns out that there is no standard as to what those numbers mean. That explains why the 60 treadwear Yokos seem about the same as the 100 treadwear Nittos. They just pick numbers based on the relation between their different tires and how they want them perceived by customers.:confused:

Didn't really get into it as I was just interested in the fact that they seemed bomb proof the way they just don't cycle out. I've run Yoko A008s, A032s, A048s, and Kuhmo V710s and they all harden very noticeably. (Victoracers cycled out rather quickly. The Yokohamas cycled out quite a bit slower. Friends with Hoosiers report they cycle out VERY quickly)

"Cycling out" is where the rubber vulcanizes till its properties change and noticeably reduces it's grip. A full heat cycle is quite an intensive event for rubber but even the slight warm up of daily driving will have some effect. Also time will do the same thing. It is a "mushy" science...

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As far as the dangers of using R compound tires over the last 130K miles...
They are softer so they can pick up screws and nails. Because they are soft a nail in the tread doesn't seem to leak very fast. I keep a plug kit in all my cars so I don't consider it an issue.
I have had a defective "one way" tire spike setup make a number of cuts into some A032s. Had to complain to the HOA to get it serviced.
I once has a whole snap off utility knife blade go straight through the center of a tire tread! A one inch slice through even the steel belts and the whole unbroken blade found inside the tire! Just freaky!
I've had a tire degenerate because of damage from being driven a couple miles with low pressure half a year before. At the end of a 2500 mile roadtrip in really hot weather I ended up with bubbles under the sidewall and tread.

So there were only 2 real "failures" and one was a freak accident and the other, while odd, had its basis from obvious misuse.
I am completely sold on the NT01s and I abuse the tar out of them and in the rain I look for ANY standing water as they WILL aquaplane.

I know that... which is why I said the same thing in my reply, if you care to re-read it. Another "sniff test" is just holding your hand on the tire after driving it, which will tell you that the outer surface of the tire isn't all that hot and nowhere near the 140 degrees at which point the tires in question start to get happy.

The internal tire air temp is probably closer to the tire carcass temp than you think, though. I'm still betting that normal street driving doesn't put enough heat into the tires to make good use of them, which is why a different type of tire might be a better choice.

JR

Do the rear tires on our cars typically run warmer then the front tires due to the rear weight bias of the car?

Yes, quite a lot.

I drive most of the time on r-compound tires, at the moment Toyo R888, before that Yoko a032 and Pirerlli P Zero C.

Maybe they heat cycle out of competative use, but they are still more grippy than street rubber after a lot of cycles and they can still take the heat from track use, unlike street compound tires.
So for trackdays etc heat cycle is a non issue...