New Best 1/4 mile!
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#23
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Guys any idea of optimal tire psi for 17 inch MT street radials.?? weather today is 16-20 degree Celsius.
Last edited by Rider; 01-16-12 at 03:20 AM.
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The outcome was not fruitful at all... best time was 12.4 with a 1.99 60ft.. as a matter of fact I struggled to hit 1.9s!! constant 2.0s which was not the case with my PSS's... Also I noticed that the car does not hit the rev limiter at the end of the 1/4 mile on 4th gear as it did previously on PSS... this time it hit its later on after I cross the line... any explanation for this?? Oh I ran 17 inch MT street radial 275/40 slicks... tried 16psi, 20, and 30 with with no luck
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The outcome was not fruitful at all... best time was 12.4 with a 1.99 60ft.. as a matter of fact I struggled to hit 1.9s!! constant 2.0s which was not the case with my PSS's... Also I noticed that the car does not hit the rev limiter at the end of the 1/4 mile on 4th gear as it did previously on PSS... this time it hit its later on after I cross the line... any explanation for this?? Oh I ran 17 inch MT street radial 275/40 slicks... tried 16psi, 20, and 30 with with no luck
From the information you've given, I would say that the tire pressure was definitely too high. With my NTO5Rs, I see the best grip in the 12-14psi range. Next time you hit the track, try starting at 14-15psi when the tires are cold and working your way down from there after you've done a run or two.
The reason your not bouncing off the rev limiter as early as before is probably due to the Micky Thompson being a taller tire. If you compare the height of the tires and find the MT to be taller, you'll definitively have your answer.
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Grip is fine on all tire pressures... its just that the setup does not work for some reason.... 19s front and 17 rears... maybe the overall tire diameter is affecting the transmission?
Last edited by Rider; 01-17-12 at 02:34 AM.
#28
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Honestly with regards to tire pressures you should always start high and work your way down. You want to have the highest pressure with a limited amount of slip for optimum times.
How were the temps for the day? Your 12.2 was done at 18C right? Any headwind/tailwind differences from your 12.2 run?
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the thing is i have problems with gearing as mentioned... maybe coz front tires size is 225/40/19?? weather was better this time.. 15C.. and most people improved their time on their runs..
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Your front tire size isn't going to affect your gearing. Rear tire size is what matters. It looks like (from reading your other posts) you had a 26.0 inch diameter rim/tire factory, and your slick comes in under 26 inches at 25.7 inches.
http://www.miata.net/garage/tirecalc.html
Meaning, your slick is smaller overall in terms of gearing. I think you being slower probably has to do with prep/tire temp/ way to high of tire pressures. Like others have said you should've started at 15psi and went DOWN from there. Also remember cold tire pressures are going to be lower than a measurement taken from a heated up tire.
I'm definitely no expert though. lol
http://www.miata.net/garage/tirecalc.html
Meaning, your slick is smaller overall in terms of gearing. I think you being slower probably has to do with prep/tire temp/ way to high of tire pressures. Like others have said you should've started at 15psi and went DOWN from there. Also remember cold tire pressures are going to be lower than a measurement taken from a heated up tire.
I'm definitely no expert though. lol