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-   -   tire psi (http://www.focusfanatics.com/forum/showthread.php?t=198916)

djo90 05-12-2009 10:40 PM

tire psi
 
I'm racing Friday night. I'm gonna prep my car before, I've heard you can launch better with less tire psi, if this is true, what should I drop it to? I't on a SVT focus with 215/45/17 BFG Gforce sports temp will prolly be in the low 50's

daveyboy 05-12-2009 11:00 PM

Quote:

Originally Posted by djo90 (Post 2742942)
I'm racing Friday night. I'm gonna prep my car before, I've heard you can launch better with less tire psi, if this is true, what should I drop it to? I't on a SVT focus with 215/45/17 BFG Gforce sports temp will prolly be in the low 50's

I had mine set at 32 psi in the front and 45 in the rear. The optimum pressure is diffrent from car to car. So you will have to play a bit. A good way to figure out what pressure is best is take a grease pencil and make a line across the tread in a few spots and do a burn out or a couple of runs. then check your marks. If it is scrubbed of from the outer edges but not in the middle, you dont have enough pressure... And if it is scrubbed from the middle and not on the outer edges there is to much pressure. Idealy the line should be scrubbed off evenly accross the tire.Thats the easiest way I know how. then just exsperiment from there to find the quickest time. You can also increase or decrease your roll out (Distance the tire has to travel before it esposes the beam) by changing tire pressure. and increase in pressure will decrease it slightly and a decrease in pressure will increase your roll out slightly. I always set my rear pressure to the maximum recomended pressure(its on the side wall of the tire)for reduced rolling resistance. Hope this helps

any one have any other ideas (or corrections)

djo90 05-12-2009 11:10 PM

Well I'm only making one run but I've nevr heard of that, I just have no experience lol

daveyboy 05-12-2009 11:19 PM

If you are just making one run just leave them at the stock pressure. sorry i guess i was over thinking that a bit

focusmaniaczx3 05-12-2009 11:32 PM

lowering the psi in rim tires isnt going to get a better launch you just are giving yourself better chances for a blowout on the way home. dont worry about tire pressure unless you are running drag tires.

djo90 05-13-2009 01:25 AM

alright. Thanks for the advice! I'm a complete newb at this and you know a lot more than me!

focusmaniaczx3 05-13-2009 02:48 AM

no worries m8! we all started somewhere and its kinda hard to learn without asking some questions! glad to help

szabyk 05-13-2009 04:28 AM

Quote:

Originally Posted by djo90 (Post 2742942)
I'm racing Friday night. I'm gonna prep my car before, I've heard you can launch better with less tire psi, if this is true, what should I drop it to? I't on a SVT focus with 215/45/17 BFG Gforce sports temp will prolly be in the low 50's

10psi [race]

focusmaniaczx3 05-13-2009 04:45 AM

eh er uh no. rim tires + low PSI does not = hook up and go. that equals wear the outside edges of the tire and possibly some rim and lots of spinning.
10psi slicks yes! rims no!

djblackout 05-13-2009 05:38 AM

what psi should the SVT's be at? the dude has them @ 50


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