Low VS High Tire Pressure To Build Heat in Tires - LotusTalk - The Lotus Cars Community
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post #1 of 19 (permalink) Old 11-09-2017, 11:37 AM Thread Starter
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Low VS High Tire Pressure To Build Heat in Tires

So I've heard both on this board and others
I'm going to my first HPDE with the Lotus this weekend and it's going to be 30-40 degrees all day (may even start out a bit colder)

So I'm a bit concerned about the R888Rs. I don't bring R-Comp tire'd cars out into weather below 60 much less below 40 for good reason.

So which is the best way to get heat in the tires?
Low Pressure? (supposed to create more deformation in the tire which creates friction/heat
High Pressure? (Higher slip angles create heat for obvious reasons)

What say you?
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post #2 of 19 (permalink) Old 11-09-2017, 11:58 AM
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Impressive, from where I'm sitting I think, you've answered your own question(s)...

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post #3 of 19 (permalink) Old 11-09-2017, 12:57 PM Thread Starter
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Impressive, from where I'm sitting I think, you've answered your own question(s)...

Kiyoshi
So the answer is C. All of the above?
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post #4 of 19 (permalink) Old 11-09-2017, 01:13 PM
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Originally Posted by Ls1Rx7 View Post

I don't bring R-Comp tire'd cars out into weather below 60 much less below 40 for good reason.
To me this answered the question.
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post #5 of 19 (permalink) Old 11-09-2017, 01:41 PM
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Which track are you going to and who is running it?
Which run group will you be in?

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post #6 of 19 (permalink) Old 11-09-2017, 02:20 PM
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Low pressure. You have higher strain losses and any frictional heat generation will be greater as well. But I agree with above, under 40F, you're much better off with a different tire.
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post #7 of 19 (permalink) Old 11-09-2017, 02:31 PM
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Originally Posted by Ls1Rx7 View Post
So the answer is C. All of the above?
To recap:
* R-tires & cold don't mix.
* Heat in entire tire = work the entire tire by compressing & decompressing (loading & unloading) the air in the tire.
* Heat in tread surface = scrub tires (slip angle)

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post #8 of 19 (permalink) Old 11-09-2017, 02:35 PM
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A lower PSI is best, but the reality is with track and air temps that cold you won't retain ideal tire heat for very long anyways.

The big question: Have you thought about oil temps? If you have the stock oil cooler(s), blank them off in cold weather.
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post #9 of 19 (permalink) Old 11-09-2017, 03:37 PM
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How old are those 888's?

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post #10 of 19 (permalink) Old 11-09-2017, 03:37 PM Thread Starter
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Which track are you going to and who is running it?
Which run group will you be in?
Masstuning trackfest at Canaan motor park, up in Canaan NH this weekend. There are a couple Elises going, and still some spots available I think.

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Originally Posted by me73 View Post
Low pressure. You have higher strain losses and any frictional heat generation will be greater as well. But I agree with above, under 40F, you're much better off with a different tire.
I don't own different tires for the car. This event has been moved to later in the season because the original date was rained out.

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Originally Posted by khamai View Post
To recap:
* R-tires & cold don't mix.
* Heat in entire tire = work the entire tire by compressing & decompressing (loading & unloading) the air in the tire.
* Heat in tread surface = scrub tires (slip angle)

Kiyoshi
That clinches it, I'm going with lower pressure, and I'm going to keep the traction control on for the first few sessions.
If upper 20s are supposed to be the hot pressure, what should we start the pressure at cold? low 20s?
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post #11 of 19 (permalink) Old 11-09-2017, 03:48 PM Thread Starter
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Quote:
Originally Posted by +TSRAGR View Post
A lower PSI is best, but the reality is with track and air temps that cold you won't retain ideal tire heat for very long anyways.

The big question: Have you thought about oil temps? If you have the stock oil cooler(s), blank them off in cold weather.
I put 5w-30 in it to account for the lower temps, but I'm uncomfortable with covering the oil coolers without an oil temp gauge.

Quote:
Originally Posted by LotusCC View Post
How old are those 888's?
They're about 2-3 months old, some street miles but no track time

Last edited by Ls1Rx7; 11-09-2017 at 04:52 PM.
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post #12 of 19 (permalink) Old 11-10-2017, 03:09 PM Thread Starter
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Well it looks like running in the low 20psi range I gained about 30 degrees at the surface just driving to work today.
Driving home it was around freezing, so I decided to continue testing the car. These tires are no worse in the cold than any of the high performance summer tires I've used.
I have a Rev400 kit and I tried to test the limit of adhesion slightly while turning a corner giving it more throttle than I thought would stick and it still stuck great . Front end grip is a bit more difficult. I turned into a couple corners overly agressivly and the front end didn't bite initially.

Overall when driving my favorite back roads I still wasn't able to find the limits of the tires even doing some very hard driving sections. A race track is a totally different level of intensity, but so far better than I expected, they don't become rock hard and useless like some claim. They're still better than street tires even at these temps.


In the garage this morning:



At work 25 mins later, ambient temp was the same:
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post #13 of 19 (permalink) Old 11-10-2017, 03:36 PM
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47 F is ridiculously low.

Really, you are only getting maybe 15 F over ambient. You need around 180-220 F (real time measurement).

If you are set on the track day, you can still do it, but think rain conditions. Then your braking points may be in the right area.

Your turn-in points will be slightly early, because of the understeer.

Good Luck,

Stephen.

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post #14 of 19 (permalink) Old 11-10-2017, 03:47 PM
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If it's in the 30s F I don't think you will have any problems from blocking off the oil cooler ducts. Arguably you invite more problems if you don't block them off with temps that low and typical rpms seen at the track.

Also your Dunlops may never grip as well as they were supposed to after driving them in freezing temps. Another possibility is that they can crack or chunk if they are used in freezing conditions.
https://www.tirerack.com/tires/tiret...jsp?techid=30&
https://www.tirerack.com/tires/tiret...jsp?techid=273

I drove a set of ZII tires in freezing temps and while the grip seemed safe, the tires never seemed to have the same ultimate dry grip after it warmed back up.

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post #15 of 19 (permalink) Old 11-11-2017, 07:01 AM Thread Starter
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Quote:
Originally Posted by lighterthanair View Post
47 F is ridiculously low.

Really, you are only getting maybe 15 F over ambient. You need around 180-220 F (real time measurement).

If you are set on the track day, you can still do it, but think rain conditions. Then your braking points may be in the right area.

Your turn-in points will be slightly early, because of the understeer.

Good Luck,

Stephen.
There seems to be just as much debate about what is the temp cutoff, as there is with regards to how to increase tire pressure, with seemingly everyone from warmer states stating the above, and I have seen some crazies enjoying r-compound cars on a snowy day at the nurburgring on the other end.

I am going to block off one of the oil coolers (front and back) with cardboard, and I might block the other off, and I agree with people here that chances are good that the oil would be fine. Just running it through the loop, the length of the car works as an oil cooler. but I'm trying to think of a way to still get a general idea of oil temps so I can monitor them.


Figure I use the IR thermometer to take the temp of the oil coolers and add 30-50 degrees to estimate the oil temps in the engine. Anywhere else closer to the engine that I can access with the IR thermometer that would be a little closer to oil temps in the engine?
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post #16 of 19 (permalink) Old 11-29-2017, 02:49 PM
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In temperatures below 60 degrees neither oil cooler is necessary.
The oil doesn't even reach 180 in normal conditions even in hot
summer weather. Search for the discussion about engine oil temps
and how coolers of various sorts and locations affect temperatures.

I block off both coolers even in weather above 75-80. The dual cooler
system was designed specifically for track/race use, not auto-x or hard street
driving.

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post #17 of 19 (permalink) Old 11-29-2017, 03:30 PM
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I wouldn't trust an IR thermometer for taking tire temps at all, pyrometer with a probe is the way to go. The outer surface you're measuring with IR is going to cool very quickly esp in those temps while you're parking, getting out and checking.
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post #18 of 19 (permalink) Old 11-29-2017, 03:49 PM Thread Starter
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I wouldn't trust an IR thermometer for taking tire temps at all, pyrometer with a probe is the way to go. The outer surface you're measuring with IR is going to cool very quickly esp in those temps while you're parking, getting out and checking.
Understood, I never updated this thread, but I checked the temps after getting back to the pits several times and I'm pretty sure we never eclipsed 100 degrees. Most of the day I took readings in the high 80s-90 degree range (surface temps with the IR)

Despite that the car still pulled 1.1G regularly on almost every lap, and peaked at 1.2Gs briefly, early in the day, and this track only has one high speed banked corner, the rest are pretty flat or off camber.

So I guess the point is, I wanted to give the feedback that R-Comps aren't useless in colder weather. They do have less traction, and that was apparent, but they were still better than the cars on street tires there, which were also being impacted by the weather.
I also was surprised by the number of times the car sustained those lateral grip figures, I didn't get the sense that we were pulling those numbers especially in some of the slower corners (one in particular that is perpetually in the shade) And all of the rubber picked up that day was on the outer edge of the tires (And I have more than -2 degrees camber on all corners), so the softness of the springs wasn't helping my tires wear even but it was probably helping total grip. I put a front sway bar on the car and did an AutoX the next weekend and it was terrible, car pushed absolutely everywhere.

Some videos from a couple of the faster laps towards the end of the day, when it was actually cooling down (high 30s/low 40s):

Last edited by Ls1Rx7; 11-29-2017 at 03:56 PM.
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post #19 of 19 (permalink) Old 11-29-2017, 05:37 PM
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I am curious how a performance winter tire (something like a Michelin Pilot Alpin) compares to rcomps @ 40 F, on the same car. It's hard to compare to other cars on street tires, even though you shared the track conditions... They could have been summer tires also out of their element, they could have had inferior suspension, etc. Just too many variables. I would be interested to see the comparison on the same car, though I couldn't personally see myself buying something like the Alpin while I live in the south (it's nearly December, today's high was 72 F).
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