tire discussion width vs heat vs traction

[somedude]

This is for my A8 track car. Now that its winter my mind gets thinking about. Last year I was running 225/40/17. The car is still relatively heavy and for the sake of simplyfing discussion assume that is a constant at 3500lbs. When I start pushing the 225’s I had last year really hard I would start to overheat the tires after a few laps of 10/10 driving. This is not really a surprise as this is a heavy car but I love driving hard enough that the car is loose so I get to dance with it around the corners. The dynamics of the car encourage very late braking and trail braking to get the rear loose. The car is way too short on power to rotate under power to any major extent.

I want to see if my thinking is correct.

I am currently over heating my tires, and since there is no real way to add cooling to tires I am thinking that larger tires would reduce the heat generated by reducing the ground pressure. Lower ground pressure = less friction = less heat?

Can i go too big?

currently I have tiny tires because I got a smoking deal on them as race take offs. I have fitted 265/45/20 on it just to see if they would fit from my W12 and they fit perfectly with room to spare. I am confident I would move all the way to a 285 with no rub. If I roll the fenders I think I could get into 315’s in the front and I would have to cut the rear fenders to go that larger in the rear, but this is a track car so i’m not opposed to it.

Tire cost VS grip?

I went with the 225’s last year because they were $100 race take offs. I don’t race for money so this was a great deal for me. As I go up in size I know the pricing is going to go up quickly as well. With my 1990 SHO track car I ran 245’s for years because they were so cheap. What are your thoughts on price VS grip VS longevity.

On a side note my winter setup on this car is a massive 235/60/18 from a SUV and it fits with no rubbing at all.

[fairgentleman_Z]

The only correct answer is: http://www.amazon.com/s/ref=nb_sb_ss_c_0_7?url=search-alias%3Dautomotive&field-keywords=tire+pyrometer&sprefix=tire+pyrometer%2Caps%2C163

Record three spots for each corner, ~1" off inside shoulder, middle, ~1" off outside shoulder.

http://www.motoiq.com/MagazineArticles/ID/916/PageID/1054/Project-Racer--Part-5-Basics-of-Tire-Pressure.aspx

Pressure is a function of, well, pressure. 30 psi is a 225 is still 30 psi in a 315. Changing tire size changes footprint shape, but not the area (in the most basic terms). A wider tire would have shorter road contact length.

http://www.motoiq.com/MagazineArticles/ID/3974/How-to-PROPERLY-select-and-size-TIRES-for-PERFORMANCE.aspx

[travisn]

If you really want data get one of these (or a few individual sensors) http://www.texense.com/en/produits/world-pro_1/irn4c-tire-tyre-temperature-sensor-multi-channel-can-motorsport-tire-temp_72.html

Could read it with an arduino or something like it

[fairgentleman_Z]

Surface temp is not a preferred method. I also disagree with motoiq’s suggestion of 1/16" depth. Should go down to the belt package/cords.

http://www.longacreracing.com/technical-articles.aspx?item=8159&article=Probe%20versus%20Infrared

949 Racing

http://www.longacreracing.com/technical-articles.aspx?item=8165&article=Pyrometer%20Tips
http://www.longacreracing.com/technical-articles.aspx?item=46317&article=Tire%20Temps%20Tell%20a%20Story

(some of the language in the last one is oval/circle track)

[travisn]

yea but you can get live data vs old.

[fairgentleman_Z]

Are you making live adjustments to pressure and camber? Then it might make an ok reference point.

The “old” data is more accurate as it is insulated from outside conditions. Are you cooking this year’s turkey based on surface temperature alone?

[travisn]

No, but the turkey isn’t spinning around a track for a few minutes before I want to know the temperature. I’m sure there is data correlating surface temp to internal temp #areaunderthecurve .

[fairgentleman_Z]

Sure, but you would also have to know ambient temp and track temp as part of the correlation.

So somedude, do this;

Buy a $100 probe pyrometer, it reads internal temp., you’ll have to write down probe temp = internal temp.

Buy four of these https://www.autosportlabs.com/product/texense-4-channel-tire-temperature-sensor/ for $3800, because if you are live recording data you’ll want to capture each corner instantaneously. This surface temp will be cooler than your internal temp so you’ll also have to record ambient temp and track temp for each session to understand how it cools the tire. Make sure you repeat these steps for hot overcast days, cool sunny days, breezy days, humid days, newly paved tracks, days when you can fry an egg on the road, days when there was frost in the morning and dusting snow in the afternoon. The more data points for varying ambient and track temps the better. Next repeat for each tire size that you want to evaluate. Now you need to compare the surface temp, ambient temp, track temp and tire width to the probe temp. By now you should have few hundred data points, and then can come up with a theoretical equation (Surface temp)(cooling factor ambient)(cooling factor track)(cooling factor width) = probe temp. And now you can start to correlate surface temp to internal temp.

Or you could just take a probe and get the internal temp.

[travisn]

I guess either way you need two data points to get the thermal gradient.

[LZ1]

All this talk of science and shit when the actual solution is throw bigger fucking tires on the car lol

Go look at what size tires auto manufactures throw on cars with similar weight and size for all out performance.

[travisn]

It’s fun to argue. I didn’t even read the whole first post.

[somedude]

@LZ

All this talk of science and shit when the actual solution is throw bigger fucking tires on the car lol

Go look at what size tires auto manufactures throw on cars with similar weight and size for all out performance.

is there a point of diminishing returns? By that I mean if I go to wide will I not be able to get them up to temp? It sounds odd to say but I am about the same weight as a C7 corvette an it runs a shit load of rubber. If I can find a suitable set of wheels I might go with a 275 or 285. I have a difficult time picturing a tire not getting up to temp in a few laps of hard driving or some sliding around.

The Temp monitoring is good stuff guys. I already know I am putting too much heat into them. I can tell that from behind the wheel. When I have adjustable arms I will be more concerned with inside vs outside temps. I have to run a lot of pressure in my 225’s to get a decent wear pattern on them because of the weight and boatyness

I will pick up some paper and a pyrometer to see how out of wack things are next time out.

Front

Rear

Lean baby Lean!

[fairgentleman_Z]

@travisn

I guess either way you need two data points to get the thermal gradient.

But one gradient is not enough, environment factors will change the slope, different tire constructions, compounds, and tread thickness are going to create different slopes. I won’t disagree that IR can complement probes, can be a quick reference, but it shouldn’t replace probes.

For example, I doubt there is the same 84* swing across the width in internal temp, especially if the target is 15-20*: It is a pretty reference though, just like FEA models make a pretty reference, I am more interested in true numerical data.

@LZ

All this talk of science and shit when the actual solution is throw bigger fucking tires on the car lol

But we need the science, our set-ups have to last hundreds to thousands of race miles. It’s not like we can show up to the track, lay a nasty burn out, drive a whole 60 feet and then scapegoat track prep.

@somedude

is there a point of diminishing returns? By that I mean if I go to wide will I not be able to get them up to temp? It sounds odd to say but I am about the same weight as a C7 corvette an it runs a shit load of rubber. If I can find a suitable set of wheels I might go with a 275 or 285. I have a difficult time picturing a tire not getting up to temp in a few laps of hard driving or some sliding around.

Here is a bunch of hear say nonsense:

I can’t find anything current, but I wouldn’t be surprised if the T1 setup is 335 rear / 315 front, at least that was in 2003 for C5s:
http://cdn.growassets.net/user_files/scca/downloads/000/009/914/T1_Runoffs2015_Race_Official.pdf?1443359126
How to get into SCCA T1? - CorvetteForum - Chevrolet Corvette Forum Discussion
~3400 lb race weight for mustang and vette

225s are too wide for ITB car to heat up, ~1900-2100 lb cars, 90-110 whp.

225s are the tire for ITA, ~2200-2500 lb cars, 130-150 whp.

weights with driver and fuel

Used race tires are the way to go. Find some cheap wheels in a width that compliment the popular size.

When is the last time you tried the 200 tread wear contenders, Direzza ZII, RT-615K, etc, etc… You’ll lose ultimate grip (and that might complement body roll?) but may gain longevity.
http://www.hotrod.com/how-to/wheels-tires/1401-the-best-200-treadwear-tires-test/

[02NismoSpecV]

i assume your question is in regards to the front tires mostly? based on the pictures i would suggest stiffening up the front if its rolling over that much in the corners- or play with different sway bars if that is an option. how adjustable is your camber, or what is it set at currently?

and a 225 is way to small for a car or that size. thats good for something like a SPEC E30 or honda. but you would be a lot better off going with a 265+ on lets say a 9" wheel.

[fairgentleman_Z]

@02NismoSpecV

and a 225 is way to small for a car or that size. thats good for something like a SPEC E30

Sure they are, if you feel like cheating:

spec30_rules.pdf

@02NismoSpecV

but you would be a lot better off going with a 265+ on lets say a 9" wheel.

Which 265 and above are you talking about? 9" Seems skinny.

[02NismoSpecV]

@fairgentleman Z

Sure they are, if you feel like cheating:
https://nasa-assets.s3.amazonaws.com/document/document/195/spec30_rules.pdf

Which 265 and above are you talking about? 9" Seems skinny.

i was more or less making a reference to the weight of those cars. not to nit pick what tires they are allowed to run.

and in regards to the 265. a certain tire would fit a 9" wheel(sqaurely- without being to wide. i run 265’s on the front of the Roush on an 18x9), probably shouldve left of the +. and maybe a little narrower of a tire would be IDEAL for a 9" wheel but until you know what he can actually fit, there’s no point of digging into it.

[Harvey]

I would go with the largest common (read cheap) size tire you can find. Your car is heavy by track standards. In my old ~2900 lb STi, I had no problem heating up 275 tires, and even overheating certain brands/compounds after 20 minutes. Do you know how long you will be staying out on track for each session, or what compound you plan to use?

I think that the best thing is to use temperature as fairgentlemen said to get your setup right. Using a wider tire won’t help if you’re over heating the outside 2". Measure the inside of the tire ~ 1.5" from the shoulder, the center and the outside. Also remember that driving style has allot to do with tire wear, temperature and even your setup. If you’re throwing the car into turns and pushing through, you’ll need more front camber and probably toe out than if you come in soft and smooth.

[fairgentleman_Z]

Which 265?

Just because a tire fits on a wheel does not mean that it is optimizing the tire’s footprint. Taken from my first post:

@Billy

*Billy’s rule of thumb:
“For ideal handling: when sizing a tire for a given wheel, I usually target a tire’s TREAD width to be as wide as the WHEEL width, or 0.5” narrower than the wheel width.”
From my personal experience working on and driving countless track days, time attacks, street cars and race cars, this typically optimizes the tire’s carcass for response and outright grip. It also gives the sidewall a very slight ‘stretch’ or preload, which will improve the tire’s response and break-away characteristics.

[02NismoSpecV]

@fairgentleman Z

Which 265?

Just because a tire fits on a wheel does not mean that it is optimizing the tire’s footprint. Taken from my first post:

im not getting in a pissing match with you man. yeah obviously you would want the “tread width” of the tire to be narrower than the wheel width. and yeah just because you can put a 265 on a 9" wheel doesn’t mean its optimal.

and here, since you are so strung out on a 265 is too wide. here is a 265 on an 18x9 wheel that i ran on my mustang years back. which you can see is slighty stretched.

but all bullshit aside. if he happened to get 265’s because it was a good deal and mounted the on a 9" wheel it would be better than running the 225’s he has now.

I’m out of this thread. peace

[fairgentleman_Z]

@fairgentleman Z

Which 265

@fairgentleman Z

Which 265?

@02NismoSpecV

and here, since you are so strung out on a 265 is too wide. here is a 265 on an 18x9 wheel that i ran on my mustang years back. which you can see is slighty stretched.

but all bullshit aside. if he happened to get 265’s because it was a good deal and mounted the on a 9" wheel it would be better than running the 225’s he has now.

For a third time, which 265s are those? They look like Z101s but I can’t tell for sure, if they are 265/35R18 then they are probably fine, the tread width is 9.0"(Z102), where as the ZII 265/35R18 has a tread width of 10.0".

http://www.tirerack.com/tires/tires.jsp?tireMake=Dunlop&tireModel=Direzza+DZ102
http://www.tirerack.com/tires/tires.jsp?tireMake=Dunlop&tireModel=Direzza+ZII+Star+Spec

• • • Updated - - -

Now if the 225/40R17 are anything like the Hoosier (Continental owns Hoosier), well, they are 9.0" wide tread width.

http://www.tirerack.com/tires/tires.jsp?tireMake=Hoosier&tireModel=R7&sidewall=Blackwall&partnum=24ZR7R7&tab=Sizes

So, 225 = 9.0" bad, but 265 = 9.0" good? Oh bro, your 9.0" wide tires are overheating, have you thought about trying a 9.0" wide tire?