Answers to questions regarding KUMHO MX tires

[AMoore]

I was discussing Kumho tire pressures with a few of you at the track.  I sent the following e-mail to a tech at Kumho and received the following response:

 
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I have Kumho MX tires on my tracks set up 1993 Porsche 911. The tires are larger than stock but fit well because of suspension upgrades. I realize that the tires permit over 50 lbs of pressure; however, can you advise as to a good pressure for these tires (hot and cold). I believe the car manufacturer recommendations may be too low as I am experiencing sidewall flex on the track. Thank You,

 



Aaron,

Thank you for contacting Kumho Tire, track situations require an adjustment to both the car and tire. The MX was designed as a ultra high performance street tire. There will be certain limitations as to the max performance on the track, especially with a unique car design such as the rear engine Porsche. That being said I'll give you some basic information as to the pressures, keep in mind that there are many factors such as camber, toe, etc that will have a direct effect on the wear and performance. You will want to increase cold pressures to aprox 40-42 PSI as a starting point, generally the tire will rise 10 PSI under severe conditions. The higher pressures will keep the sidewall from flexing as bad.  Because of the design of the car and tire you won't be able to get rid of the sidewall flex completely but the higher pressures will help.  Another suggestion would be to increase camber (you didn't indicate the settings) and that will help with the tire and feel of the cornering and turn in. I hope this helps, let me know if you have any other questions.

[size=2]~Jason Myers

Motorsports Services

 

Kumho America Technical Center

711 South Cleveland-Massillon Road

Akron, Ohio 44333

KumhoTireUSA.com

 

 
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[ninjabones]

Aaron:

I played around with different temps at Shennandoah and again this weekend at Pocono, taking pyrometer readings several times.  My sweet spot appears to be 40 lbs (hot) with cold temps on saturday morning starting at 32 fr / 33 rr (it was pretty cold)  Although my readings were not consistent across the tire (outside temps much hotter due to less than aggressive camber settings), the average temps on each tire were pretty close to the middle tire readings.  Unless I've been misinformed, this is the best way to determine appropriate tire pressures.  Sometimes, I think the manufacturers recommended pressures are determined entirely for maximum safety and not performance (CYA).  You lawyers should know about that pretty well.

I'm running 235/40/18 , 275/35/18 so my sidewall is going to be a bit shorter than your 17s. That may explain some of the difference in feel.

Anyway, maybe the 10 lb difference in tire pressures explains why I passed you on that last run on Saturday afternoon (it certainly couldn't have anything to do with driving skills).

 

G

[AMoore]

ninjabones wrote:

I'm running 235/40/18 , 275/35/18 so my sidewall is going to be a bit shorter than your 17s. That may explain some of the difference in feel.

Anyway, maybe the 10 lb difference in tire pressures explains why I passed you on that last run on Saturday afternoon (it certainly couldn't have anything to do with driving skills).



G

I agree that your thinner sidewall decreases flex.

As to your other comment, you certainly noticed that we were both caught up behing three other cars when I gave you the pass.

I have no problem giving a pass at any time. Getting it back is what makes this fun.

[ninjabones]

I knew that would piss you off.... I was just goading.  I also hope it doesn't dissuade you from giving the point by again... I promise I'll give it back (if you're keeping up).  It's kinda like golf... you only remember your good holes and forget about all the double bogies (like the ump-teen times you've probably passed me on other occasions).

G

[pmajka]

Arron, what size tires are you running..

how is the Squeal factor??

how did you like the handling of the tires since your last set???

[AMoore]

I'm running 275/40/17 and 245/45/17.  They don't squeal much but I would not buy again.  I think I would try the Nitto NT01.  I believe they are softer.