gear ratio to tire size question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

MITCH1914 · 07-09-2002, 03:18 PM

i have 373 gears in my 12 bolt. i am also using hoosier 275/60/15 radial tires(27 OD). when i put my rpm/tire size and speed into the gear ratio formula i get a ratio close to 410.

1st question. what tire size or OD do i need to have so that i can have a 373 ratio?

2nd i am going to buy some bfg drag radials 275/50/15. these tires have a OD of 26. what gear ratio will this cause my truck to have?

currently i am running 2950 rpm @ 55 mph on 27inch tires.

what i am trying to do is get a tall enough tire that will drop rpm on the highway. i also want to get a drag tire that i can change to at the track that will get me a good low gear so that i can leave hard and have a stout trap rpm (i will switch to the short tires only when i am at the track)

anyone have any feed back 0n this?

07-09-2002, 03:18 PM	#1
MITCH1914 Registered User Join Date: Mar 2001 Location: indianapolis,indiana,usa Posts: 506	gear ratio to tire size question i have 373 gears in my 12 bolt. i am also using hoosier 275/60/15 radial tires(27 OD). when i put my rpm/tire size and speed into the gear ratio formula i get a ratio close to 410. 1st question. what tire size or OD do i need to have so that i can have a 373 ratio? 2nd i am going to buy some bfg drag radials 275/50/15. these tires have a OD of 26. what gear ratio will this cause my truck to have? currently i am running 2950 rpm @ 55 mph on 27inch tires. what i am trying to do is get a tall enough tire that will drop rpm on the highway. i also want to get a drag tire that i can change to at the track that will get me a good low gear so that i can leave hard and have a stout trap rpm (i will switch to the short tires only when i am at the track) anyone have any feed back 0n this?



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