Et drag diameter question
Et drag diameter question I just bought some et drag 26" stiff sidewall tires. I measured the diameter and it is only 25". I havent mounted them yet, so they werent filled with air. Is that normal? They are supposed to be 26.5" diameter. Are they really going to grow 1.5" with only 15lbs of air in them? Or is something wrong with them? I hate to mount them and not be able to use them. I really need all 26.5" of the tire to make it through the traps. Thanks
Ryan
Ryan
What gear and trans you running to worry about running out of gear? Just curious as I am thinking a 1:1 final gear, 4.30's and making decent power rev to 7k.....
Anyways, those tires will grow at speed, and I would at least measure once air is in the tire.
Anyways, those tires will grow at speed, and I would at least measure once air is in the tire.
4.30 gear and a 6 speed. Car makes 430rwhp and rev to 6600. I'm think high 1teens, maybe 118 in the 1/4. I know they will grow alittle at speed. Problem is that if I mount them, I wont be able to return them. So measuring after they are mounted with air in them doesnt do much good. Thanks
http://www.f-body.org/gears/
I just ran a few calculations.
Assuming 7k redline...
26.5" running 118 mph will rev the motor to 6450 RPMS
25.0" running 118 mph will rev the motor to 6800 RPMS
Basically if you make any more power your going to need more RPM OR a larger diameter tire which in your case may help as a taller tire will have more give on the launch and give you a larger window.
I just ran a few calculations.
Assuming 7k redline...
26.5" running 118 mph will rev the motor to 6450 RPMS
25.0" running 118 mph will rev the motor to 6800 RPMS
Basically if you make any more power your going to need more RPM OR a larger diameter tire which in your case may help as a taller tire will have more give on the launch and give you a larger window.
lol. Those calculations are exactly my problem. I don't plan on more power unless the motor goes south. But I would also need a roll bar then, which I have no intention of doing. So at that point a larger tire would be the least of my concerns. At 26" I would be pushing my 6600 limiter. I was really hoping the 26.5" diameter that they are supposed to be would grow to 27" or more and give me a little room.
I guess worst case scenario, I could raise the limiter. I need to go back up to eastside to retune for the gears anyway. Do you think 6800 is pushing it on a stock bottom end? I kinda thought 6600 was, lol.
If your talking Eastside Perf. in Wallingford CT, they are not doing cars anymore. Sold the Dyno.
I have not researched in a while the rpm limits of the motor, so I would say if someone wants to chime in or go into the GEN III section and double chk. IMO I think your fine since you set the parameters of no more power and no cage. You may not even be fast enough to need one. All will depend on how the car 60 foots.
I have not researched in a while the rpm limits of the motor, so I would say if someone wants to chime in or go into the GEN III section and double chk. IMO I think your fine since you set the parameters of no more power and no cage. You may not even be fast enough to need one. All will depend on how the car 60 foots.
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Yeah I was talking about eastside perf. I don't need to tune it, just reset for the gears, so hopefully Ken can still do that. I was truning 12.1's with the stock rear and 2.0 60fts @115 or so. So hoping for 11.50's @max of 118.
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I have been told 6700 is about as much as you should spin the stock bottom end on a normal basis. With that said, you can keep your same shift points you have now and just run it past 6600 in only 4th gear.
What year is your car? I believe there are some differences in the bottom end depending on year. Someone correct me if I'm wrong?
What year is your car? I believe there are some differences in the bottom end depending on year. Someone correct me if I'm wrong?
car is a 98. Yes I wouldnt change shift points only rev limit to get through traps.
I mounted the tires. They grew quite a bit from just mounting and air being in them. They are slightly bigger than 26.5" with 15# of air in them. I should be good now, even with no growth factored in.
I planned on the qtp 27" but figured these would be better at 26.5" with the stiff sidewall. I didn't want to run tubes and screw the tires to the rims. If this doesnt get it done then that will be my next option.
I actually think if I run out of gear the car will be faster than 11.50, so I will prolly just alter my launch and/or shift points to make it work well for both the et and mph. Thanks for the input
Ryan
I mounted the tires. They grew quite a bit from just mounting and air being in them. They are slightly bigger than 26.5" with 15# of air in them. I should be good now, even with no growth factored in.
I planned on the qtp 27" but figured these would be better at 26.5" with the stiff sidewall. I didn't want to run tubes and screw the tires to the rims. If this doesnt get it done then that will be my next option.
I actually think if I run out of gear the car will be faster than 11.50, so I will prolly just alter my launch and/or shift points to make it work well for both the et and mph. Thanks for the input
Ryan
