Kuhmo XS Tire Pressures - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 15 Old 03-30-2009, 10:40 PM Thread Starter
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Kuhmo XS Tire Pressures

First time running Kuhmo XS tires. Any idea for initial tire pressures for a high speed autocross on pavement? With the Azenis I was running last two years I was at 35F/30R.


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post #2 of 15 Old 03-31-2009, 12:17 PM
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What size tires/rims?

I haven't run those tires, but if it were me, I'd start higher than I felt I'd end up at, mark the sidewalls for rollover, take a couple of runs, check rollover and surface temps and see where I was at...then, start tweaking f/r to taste.

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post #3 of 15 Old 03-31-2009, 08:50 PM Thread Starter
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275/40/17 on a 9" rim. -3 camber with 400lb Front coil-overs, 300lb rear. TA and Panhard.

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post #4 of 15 Old 04-01-2009, 11:00 AM
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Jason, you should be fine starting there. I will be helping Roger play with his settings also, after we check tire rollover after the first run or 2 we can hit it with the pyrometer to see how close we are.

But all that is going to be null and void because its gonna rain Sat

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post #5 of 15 Old 04-01-2009, 06:52 PM
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Ran them last month.

255/40/17 on a 9" rim. I probably should have waited and got 275, but Tire Rack local warehouse only had 2 in stock on the day I needed them. I will probably try to get the bigger size later this summer.


I ran 35Front,35 Rear. Dropped the rear to 32, will probably drop it lower this month as I was not hitting the wear indicator arrow on the rears. I would say start at 35/30 and work from there.

I ran on small lot in March, so tires never got to optimum of 203 (that is according to website, emailed them to confirm, no reply so far), or at least I don't think they did, got tired and didn't check later in the day.

Local guy tells me they need 30 or so runs before they really broken in. He runs STX in awd car and is dam good driver.

Let me know what pressure you find works best for you. Thanks.
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post #6 of 15 Old 04-02-2009, 10:28 AM
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Quote:
Philip,

Thank you for your inquiry regarding the Ecsta XS, see below for baseline info. There isn't really a temp that the tire "fades", you will need to get the proper heat into the tire to get peak performance. The closer you can get the tread to the 205 temp the more grip you will have. Let me know if you have any additional questions. Have a great day.


β€’ ** Molded to 6/32
β€’
β€’ ** Shave to 3/32 - 4/32 for max grip and durability
β€’ ** Recommend initial heat cycle for prolonged use
β€’ ** -1.0 to –3.0 degrees of camber for stock and mild suspension
β€’ ** Slight toe out front, 0 to slight toe in rear
β€’ ** 35-45 HOT PSI for most vehicles
β€’ ** Cold PSI for autocross and hot PSI for circuit racing
β€’ ** 30-36 PSI for tuned suspension and lighter cars
β€’ ** Operating temperature range 190’-210’ (205’ optimum) across tread face
β€’ ** Wet inflation pressures 5-8 PSI below dry cold pressures

~Jason Myers
Motorsports Services

Kumho America Technical Center
email I got back from Kumho.
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post #7 of 15 Old 04-07-2009, 11:18 AM
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Jason,

What pressures did you end up with?

And are you coming out on Sat with SCMC?

92 Limited Edition Vert HodgePodge MM , Cobra Brakes, Roll Bar, Auborn Pro, 31 spline Mosers, 3.73's
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post #8 of 15 Old 04-07-2009, 09:21 PM Thread Starter
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I ended up with 35F, 30 rear. I wouldn't go lower in the front unless I dail in more negative camber. The rears could go ~2lbs lower based on the wear I was seeing in the chalk lines.

I'll be there Saturday.

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post #9 of 15 Old 04-25-2009, 07:26 PM
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i ran mine for the first time today. i was plannin to start higher, but after reading this thread a couple weeks back i went with 38f/35r to start.
the car is a 3199lbs 87 tbird with cobra IRS, and 51/49 weight distribution.
the fronts looked good, and i ended up lowering the rears 2psi after my third run. probly start out 38f/33r next time and see if the wear stays consistant with what i saw today.

front


rear

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post #10 of 15 Old 04-26-2009, 08:40 PM
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For you guys running the new Kumhos, how did the XS feel grip-wise compared to other tires you have tried?

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post #11 of 15 Old 04-27-2009, 06:34 PM
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Glenn, I talked to two more "long-timers" at our autocross yesterday about the new ST tires that are out. Both seemed to think that the Bridgestone was "the tire" but they could only say so due to no one running the XS abundantly at the moment.

There was a C6 Vette running the XS's at the event, but I can't remember which one he was, or his level of skill. I just remember seeing it in the paddock before the race.

When I switch to 17's, i'm gonna go with the XS's in the 315/35 size and just start out running 32's in my big pig of a car and just create my own baseline(s).
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post #12 of 15 Old 04-27-2009, 07:35 PM
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Yeah, the bridgestones were the tires to have for the last year or two. I was just wondering if the XS comes close to that level or performance' I'm leaning toward a set of the XS since they are available in musclecar sizes. I wanted to upgrade to a set of 18x10 Roush Trak-Pac wheels on my 05 with some 295 tires, but Roush isn't selling them right now. My other alternative is to get the 275 or 285 in 17" size for my 17x9 Cobra R wheels.
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post #13 of 15 Old 04-27-2009, 08:36 PM
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Glenn,

I can't give you a good comparison, since I have never used a true autocross street tire. But they are stickier than all street tires i have used before (this doesn't say much).

Are they better than the bridgestones? I think that is still up for debate, but they are cheaper (last time I checked).

I will tell you this, most of my regional Street tire guys (STX AWD cars) have switched to the XS from the RE-01R. They did great last weekend at the TLAC 1 (Trans Louisiana Autocross Challenge) on the XS's.

also, from miata net,

Quote:
For the June 2009 issue. Just got my Grassroot motorsports where they did some Extreme tire testing. Tires were tested in 15 inch sizes on a hond civic.

Here is a summary of times from worst to first.

6th - Falken RT 615 Mean time: 35.302 Sec Quick time 35.125 Sec.
5th - Dunlop Direzza Sport Z1 Star Spec Mean time: 35.209 sec. Quick time 35.061
4th -Toyo Proxes R1R Mean time: 34.522 sec Quick Time 34.452 sec
3rd- Bridgestone RE-01R Mean time: 34.478 sec Quick Time 34.430 sec.
2nd- Bridgestone Potenza RE-11 Mean time: 34.266 Quick time 34.238 sec.
1st - Kumho ECSTA XS Mean time :34.170 Quick Time 34.030 sec.

All tires were shaved to 3/32 nd and test performed on an Autocross set up.
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post #14 of 15 Old 04-27-2009, 09:13 PM
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Wow! Thanks for the info!
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post #15 of 15 Old 04-28-2009, 03:38 PM
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Wow, I was already excited to go pick up my 285 XS's tonight, after reading those times from Miata net I'm bouncing off the walls! This is going to be a good season

MM subs, springs, and cc plates, Koni SA's, Steeda x2's, front bar, and bumpsteer kit
DBA Rotors, Hawk HPS's, FRPP 3.73's, Eaton diff, and 17x9 Cobra R's with 285 Kuhmo XS's
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