Hi, im running 6,500 or more thru the trap, will a taller tire solve this problem? I just install a 350 trans, but other than that stock gear, and has 26' tire. I have never been able to leave with any boost, so i need to get my 60ft out of the 2.0 area. Any info will be a help. I was thinking of trying a 28x9 slick. Alot of upgrades on the car including a 4.1 engine, and a 6776,FMIC, also has made alot more power.The car seem to pickup knock over 5,500rpm, will running high octain gas help this? Im now running 91-93oct,and alky.
Will a 28'' inch tire help??
- Thread starter 1chance
- Start date
. Dont want it over rev, i cant leave without spinning, so i will try them. Does the 350trans have that big of a 1st gear?A 28" tire should help you leave harder and will lower you rpm at the end of the 1/4. Clearances with the wheel well will probably be closer with a 28" tire though. And FYI, the 28x9 MT slicks are only 27" tall, not sure about other brands. Might be better trying a 275/60/15 MT drag radial. I've been 1.4s on that tire. I plan on moving up to a 28x10.5 stiff sidewall slick.
In my regal clone, I'm going to try MT 28x9 slicks. The 27" tire matches up to the combo and rpm better. A 28" tall tire would hook better off the line, but it takes more power to turn a 28" tire vs a 27" tire so you try not to run taller tires than you need to.
In my regal clone, I'm going to try MT 28x9 slicks. The 27" tire matches up to the combo and rpm better. A 28" tall tire would hook better off the line, but it takes more power to turn a 28" tire vs a 27" tire so you try not to run taller tires than you need to.
- Joined
- Aug 1, 2003
well we have an rpm and we have a tire height but need more info on whats causing the high rpm
what rear gears and at what speed are you trapping
going to a 28 will drop rpms by about 7% for you thats abot 450 rpm less at the traps
but the 28 will be harder to get out off the line if you cant build and hold more boost than you have now because it will drop your effective gear ratio , if you have 3.42gears now it will be like you put 323s in the rear axle so the time you'll lose on the bottom end of track vs the pickup up top will probably net a slower et
tires cost money , a more effective expenditure of $$ would be toward a improvinging the brakes holding power (fix em) and a more efficient converter like a PTC which will help out on the spool even if you cant build boost and at the big end with the ptc efficency it will probably drop your rpms over 600
what rear gears and at what speed are you trapping
going to a 28 will drop rpms by about 7% for you thats abot 450 rpm less at the traps
but the 28 will be harder to get out off the line if you cant build and hold more boost than you have now because it will drop your effective gear ratio , if you have 3.42gears now it will be like you put 323s in the rear axle so the time you'll lose on the bottom end of track vs the pickup up top will probably net a slower et
tires cost money , a more effective expenditure of $$ would be toward a improvinging the brakes holding power (fix em) and a more efficient converter like a PTC which will help out on the spool even if you cant build boost and at the big end with the ptc efficency it will probably drop your rpms over 600
You probably already kmow I don't agree with your 3rd paragraph at all.
To use your numbers what do 3.42 or 3.23 represent and exactly how does changing tire size change EFFECTIVE ratio
Overall ratio yes so a taller tire will change trap rpm. I allways say 1inch of tire height will lower rpm 300 at the traps
- Joined
- Aug 1, 2003
you dont have to get it , but its fact and its correct , think about it
if you bolt 28" tires onto a car that was factory with a 26 inch tire and that car has 3.42 gears you have changed thew effective rear axle gear to the same as if you had kept the 26" tire and installed 3.23 gears (actually 3.21) .... simple math
the gear ratio change youve made by a taller tire increases load as seen by the engine , if load increases rpm rate of climb will decrease... simple physics ,
your car as it was on 3.42s with 26 " tires no longer has the same effective gear ratio because the gearing change has been affected by a 28" tire , a 28 has 7.5 % more rollout per revolution than the 26 , changeing gears lower whether by tire or gears will effectiely increase the weight of the car and with a 28" that increase is 7.5% so its as if your 3500lb car now weighs 3762lbs again simple physics .
simple physics dictates that if you add weight whether it be actual or effictive through gears you will need more hp to move it
how many more ways do i need to show you before you get it
if you bolt 28" tires onto a car that was factory with a 26 inch tire and that car has 3.42 gears you have changed thew effective rear axle gear to the same as if you had kept the 26" tire and installed 3.23 gears (actually 3.21) .... simple math
the gear ratio change youve made by a taller tire increases load as seen by the engine , if load increases rpm rate of climb will decrease... simple physics ,
your car as it was on 3.42s with 26 " tires no longer has the same effective gear ratio because the gearing change has been affected by a 28" tire , a 28 has 7.5 % more rollout per revolution than the 26 , changeing gears lower whether by tire or gears will effectiely increase the weight of the car and with a 28" that increase is 7.5% so its as if your 3500lb car now weighs 3762lbs again simple physics .
simple physics dictates that if you add weight whether it be actual or effictive through gears you will need more hp to move it
how many more ways do i need to show you before you get it
- Joined
- May 28, 2001
The first thing I would do is run the motor on race gas. That will allow you to run much more timing safely without killing the motor.
If you cant launch better than a 2.0 60 foot you are not building and or keeping boost when you launch.
Remember the cardinal rule. Leave under full power finish under full power.
That could be because of a few things. You are not revving up the motor enough before you launch. I would start with a 3500 rpm launch see if that helps. Try 4000 see if that helps.
Timing increases will help too if you can change it. Dont do it without using race gas.
How about suspension? Sway bar? Air bags? Whats the pressure in the slicks ?
If you are running stock rear gears the 28 inch slick wont help.
A 3.73 or better will do exactly whats been posted, the taller tire lowers engine speed so you are not over revving the motor at the top end.
And yes the right torque converter makes all the difference in the world.
If you cant launch better than a 2.0 60 foot you are not building and or keeping boost when you launch.
Remember the cardinal rule. Leave under full power finish under full power.
That could be because of a few things. You are not revving up the motor enough before you launch. I would start with a 3500 rpm launch see if that helps. Try 4000 see if that helps.
Timing increases will help too if you can change it. Dont do it without using race gas.
How about suspension? Sway bar? Air bags? Whats the pressure in the slicks ?
If you are running stock rear gears the 28 inch slick wont help.
A 3.73 or better will do exactly whats been posted, the taller tire lowers engine speed so you are not over revving the motor at the top end.
And yes the right torque converter makes all the difference in the world.
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