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Author Topic:   gear ratio mix up....
M1
Dirt Freak

Total posts: 257
posted October 30, 2004 10:17 AM  
here is the deal. I race at two race tracks (friday night and saturday night), and I need to change the rear end from one to the other. Friday night I get home really late, so Im always out in the garage by myself changing the thing alone every saturday. Im trying to get a gear ratio that allows me to just change tire size and shift up to a different gear to go from one to the other.

its a metric car with a 7.5 rear, and I CANNOT change to anything else...so no 9inch ford or whatever.

My track I run 2.56's with 80-82 inch roll out and I am spot on for RPM's

the other track I run 2.41's and 88-90 inch roll out and am spot on for RPM's

I always use low gear, but if I could find something that works and shift into second or even high gear, so be it.

jay116
Dirt Freak

Total posts: 428
posted October 30, 2004 12:10 PM  
th-350

racer17j
Dirt Forum Champ
Total posts: 5390
posted October 30, 2004 04:29 PM  
they are both 3/8th mile tracks. The bigger one of the two is more like a 1/2 mile, because its HUGE and fast. I was getting right to 6,200 at both tracks with the set-ups I had.

I just needed to find a way to mathamatically figure out the gear ratio equivalent concidering roll out.

I think we got it figured out now, just going to have to wait until next year to test it....

racer17j
Dirt Forum Champ
Total posts: 5390
posted October 31, 2004 09:09 PM  
I ran the 2.41's at the smaller track with the 80-83 inch tires and never ran it over 5,800. When I switched to the 2.56's I was finally getting it up to 6,200, plus I had the extra RPM's comming out of the corner, and that helped alot. When I got stuck runng the bottom of the track, the 2.56's had a lot more response and speed coming out.

The BIG track is called a 3/8'th, but the smaller track I race at which is also called a 3/8th would fit inside the bigger one....EASILY! I might be a little under geared for the big track because if I run the bottom, the motor lugsdown some, so I just hang it wide open up by the wall and hold on. I could run the 2.56's there, but would run out of RPM's running high, and thats where I wanna run, thats where the fun is!!!!!!!!

racer17j
Dirt Forum Champ
Total posts: 5390
posted November 01, 2004 05:43 PM  
i guess i would try a 410 and taller tires on the big track and shorter on the small

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