Gear and tire math
08-11-2009, 11:44 AM
#3
Tough Mudder
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Thanks for
the response. How does the math work? (26/28)x4.1 ?
That comes out to 3.8071427
of course we're not coming from a true 26" tire either.
25.6/28 = 0.9142857 x 4.10 = 3.7485713
of course this could be completely wrong.
the response. How does the math work? (26/28)x4.1 ?
That comes out to 3.8071427
of course we're not coming from a true 26" tire either.
25.6/28 = 0.9142857 x 4.10 = 3.7485713
of course this could be completely wrong.
08-11-2009, 08:21 PM
#5
Tough Mudder
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Not really. I'm really just looking for someone to say, "yeah that looks right" or "no, it's wrong because..."
Last edited by Hilton; 08-11-2009 at 08:27 PM.
08-12-2009, 07:05 AM
#7
All you do is pick a RPM at a given MPH with the 4.10's, change to 28" tall tire, see the diff, and then play with the rear end ratio # to get that mph/rpm in line and that would give you the equivelent. When the 28" tall tire is factored in the gear ratio is about 3.90.
FYI, working with the gear calculator.
There is a 500rpm diff between 26" to 28" tall tires on 4.10's using 2.66 1st gear ratio. I picked 40mph @ 5700 rpms and then on a taller tire it became 40 mph @ 5200
Then I turned back to the 26" tall tire then played w/ the rear gear and it got it back to the same RPM range/mph which was 3.90's
FYI, working with the gear calculator.
There is a 500rpm diff between 26" to 28" tall tires on 4.10's using 2.66 1st gear ratio. I picked 40mph @ 5700 rpms and then on a taller tire it became 40 mph @ 5200
Then I turned back to the 26" tall tire then played w/ the rear gear and it got it back to the same RPM range/mph which was 3.90's
Last edited by BlackScreaminMachine; 08-12-2009 at 07:13 AM.
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08-12-2009, 07:17 AM
#9
If you 
it, you will find the mathematical equation to figure this out, I used this site as it makes it easier for me.....
https://ls1tech.com/forums/gears-axl...ere-first.html
http://www.f-body.org/gears/ (for the calculator)
now MIND you, if you run a bias ply, there is something that most people DO NOT account for is tire growth and a 28" tall M/T ET Drag will grow about 1 addtional inch at speed so in the end the calculator will give you a ball park and does not take into consideration any other variables except tire height, rpm, trans ratio.
This other calculator uses the formula to the decmile point is more like your math.
http://www.fbody.com/calc.htm
I was getting a 400 rpm or so swing and to get to approx the same rpm, the gear was like 3.8x
it, you will find the mathematical equation to figure this out, I used this site as it makes it easier for me.....https://ls1tech.com/forums/gears-axl...ere-first.html
http://www.f-body.org/gears/ (for the calculator)
now MIND you, if you run a bias ply, there is something that most people DO NOT account for is tire growth and a 28" tall M/T ET Drag will grow about 1 addtional inch at speed so in the end the calculator will give you a ball park and does not take into consideration any other variables except tire height, rpm, trans ratio.
This other calculator uses the formula to the decmile point is more like your math.
http://www.fbody.com/calc.htm
I was getting a 400 rpm or so swing and to get to approx the same rpm, the gear was like 3.8x
