gear ratio

ron b · 10-11-2011, 07:15 AM

i am running a 1968 mustang set up like a stock eliminator car. the car has a 428cj, pro shifted toploader and 4.56 rearend. the car ran a 10.85 at 127mph. do you guys think it would et better with say a 4.88 gear? thanks ron

Mike Taylor 3601 · 10-11-2011, 09:57 AM

Use formula to gear for rpm you want @ finish line MPH X Gear ratio X 336 divided by tire height=RPM
Mike Taylor 3601

69Cobra · 10-11-2011, 10:15 AM

Quote:

Originally Posted by Mike Taylor 3601

Use formula to gear for rpm you want @ finish line MPH X Gear ratio X 336 divided by tire height=RPM
Mike Taylor 3601

^^^What he said^^^

But Yes you need a 4.88

1299 · 10-11-2011, 08:37 PM

if you where to use radial tire or bis ply tire is it the same formula????

Mike Taylor 3601 · 10-12-2011, 02:48 PM

you would change tire height in formula,if you were trying to get that precise,but I don't know how tell how much tire growth would happen, rim/tire width,mph, sidewall etc. would all have to be factored.
I always have just used height on sidewall or mearsured and is close enough,any growth that happens is just a little cushion that keeps you from going over.
I have always geared by this formula IE if want to go through @ 8K gear so I get as close to that # as can.
Mike Taylor 3601

10-11-2011, 07:15 AM	#1
ron b Member Join Date: Mar 2008 Posts: 123 Likes: 0 Liked 2 Times in 2 Posts	gear ratio i am running a 1968 mustang set up like a stock eliminator car. the car has a 428cj, pro shifted toploader and 4.56 rearend. the car ran a 10.85 at 127mph. do you guys think it would et better with say a 4.88 gear? thanks ron

10-11-2011, 09:57 AM	#2
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,303 Likes: 198 Liked 116 Times in 48 Posts	Re: gear ratio Use formula to gear for rpm you want @ finish line MPH X Gear ratio X 336 divided by tire height=RPM Mike Taylor 3601

10-11-2011, 08:37 PM	#4
1299 Member Join Date: Aug 2009 Location: howell,nj Posts: 116 Likes: 243 Liked 16 Times in 9 Posts	Re: gear ratio if you where to use radial tire or bis ply tire is it the same formula????

10-12-2011, 02:48 PM	#5
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,303 Likes: 198 Liked 116 Times in 48 Posts	Re: gear ratio you would change tire height in formula,if you were trying to get that precise,but I don't know how tell how much tire growth would happen, rim/tire width,mph, sidewall etc. would all have to be factored. I always have just used height on sidewall or mearsured and is close enough,any growth that happens is just a little cushion that keeps you from going over. I have always geared by this formula IE if want to go through @ 8K gear so I get as close to that # as can. Mike Taylor 3601