Nice run!

 

We have another drag event on Monday.. will be running with 18 inch slicks

 

Good run, keep us posted with your next track day running slicks on F

 

Good run for street tires for sure guys.

Next month, I have a 150 shot Nitrous/Methanol kit being installed and have some 305 width NT05 DRs coming in. I'm hoping to hit the 10 second mark with this set up.

 

You going to have a really hard time with an NTO5.

 

What were you running? I might run slicks. I'm still figuring that part of the equation out.

 

Ill send you a PM when I get to a pc

 

Guys any idea of optimal tire psi for 17 inch MT street radials.?? weather today is 16-20 degree Celsius.

 

Sorry, but there is never a predetermined "optimal" tire pressure. Best bet is to adjust as the night goes on.

 

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

 

Sorry to hear that the results where not what you were looking for.

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.

 

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?

 

275/40/17 is a great size as long as your new setup is lighter than stock. The 275/40 setup is slightly shorter than the stock tire diameter so you shouldn't have any issues with gearing.

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?

 

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..

 

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