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Fri Apr 27, 2012 8:57 am

I'm building a rail with a basically stock other than dual carbs and electronic ign 1600 dual port and 002 bus trans with 31x10.50x15 tires. The 002 has 5:38 gears. What can I expect for top end speed for this setup? I primarily will be driving this on the street and am wondering if the 5:38 ratio may be a little too much gear for cruising at 55-65 mph.

Fri Apr 27, 2012 10:40 am

I had a rail with a 1641, 002 trans, and 31" desert track tires. With two people in, it barely did 70mph.

YMMV

Fri Apr 27, 2012 12:37 pm

Use one of the many rpm /speed calculators on the internet. You will need to know your actual tire diam, and 4ththe gear ratio as well as top rpm for your engine, in addition to you r&p ratio.

Fri Apr 27, 2012 3:23 pm

MPH / RPM calculators which use tire diameter are bogus. what matters is LRTR: Loaded Rear Tire RADIUS. distance from axle center to ground

Speed = RPM X LRTR / GR X 168

where GR = 4th gear ratio * R&P ratio

68 - 72: .82 X 5.38 = 4.41
73 - 75: .82 X 4.86 = 3.98
76 - 79: .89 X 4.56 = 4.06

AH sedan trans: .89 X 4.125 = 3.67

Fri Apr 27, 2012 5:15 pm

at 3k rpm Im goin 60-65 mph (31" tires) It sucks lol

Fri Apr 27, 2012 6:56 pm

Quote: at 3k rpm Im goin 60-65 mph (31" tires) It sucks lol

with a 19XX ( 3 rib 002, 5 rib 002, 091 )

Fri Apr 27, 2012 6:56 pm

here is a spreadsheet I did to compare ratios when I was selecting. Most 31/10.5s are 30.5" so that's the number I used in the bottom table. The middle one is a stock 72 and the top one is where I ended up.

Fri Apr 27, 2012 7:42 pm

Funny. I don't think its going to matter what the ratio's say, I don't think the engine will have the umpff, so your going to be stuck with what the engine can pull.

Fri Apr 27, 2012 7:58 pm

Loaded radius is acceptable, but as tire rpm increases, so will the diameter. Using measured diam, loaded radius, or any measurement will be diferent from 1mph to 80 mph. But we are not trying to split atoms here, just get an idea of rpm at a given speed/or speed at a given rpm. Centrifical force will also vary tire diam differently from one psi setting to another and one tire carcass to another, also on age of tires.

Fri Apr 27, 2012 10:04 pm

Mal evolent wrote: Quote: at 3k rpm Im goin 60-65 mph (31" tires) It sucks lol

with a 19XX ( 3 rib 002, 5 rib 002, 091 )
002 3 rib 5.38 with 31" tires
19xx? what do you mean?

Sat Apr 28, 2012 5:52 am

Quote: 19xx? what do you mean?

the year of the trans, if you don't know how many ribs it has

Sat Apr 28, 2012 12:20 pm

Mal evolent wrote: Quote: 19xx? what do you mean?

the year of the trans, if you don't know how many ribs it has
Off the top of my head I cant remember year but its a 3 rib.

Sun Apr 29, 2012 10:32 am

Gear ratio calculator...

http://www.johnmaherracing.co.uk/gearcalc.htm

Mon Apr 30, 2012 6:24 pm

Stingray250 wrote: Gear ratio calculator...

http://www.johnmaherracing.co.uk/gearcalc.htm
Thanks for posting that Stingray! Been looking for one of those! :lol: