Dodge tire size and cruising speeds

dangerous toy · Jul 17, 2009

i just bought a 97 12v 4wd 5spd and it has the stock size tires, when im running 65mph im at about 2k rpm, i'd like to be able to go 75 at around 1800-2000 RPM (in 5th) im thinking of running(with a leveling kit) a 285/75-16 or a 315/75-16, what are most of you guys running? im not sure the 285 will be enough of a size increase (and the 315 would look better) i flat tow a samurai and would like to haul a camper, so were not talking about a huge amount of weight. thanks for the input. -DT

Cascade_Crawler · Jul 17, 2009

what gear ratio do you have in the diffs? I have 4.10s and with stock size tires I couldnt really go much over 60 without turning some high RPMs. The gear ratio will dictate how big of tires you can get away with and still manage to keep some towing power.

NotMatt · Jul 17, 2009

I had 285's on my 24v with 3.55's and was pretty happy. I think 315's would've been too much. If you have 4.10's though, 315's are where it's at.

Check your gear ratio and go from there.

Freeride · Jul 17, 2009

37x12.50R17s on a 4th gen with 3.73 gears and is nice on the highway and still has tons of pulling power.

dangerous toy · Jul 17, 2009

thanks guys

thanks for the replys, i'll check my gear ratio, i thought only the 3500's had 4.10's so i just assumed i had 3.55's

Boomer · Jul 17, 2009

Shoud be a label under the hood with the OEM gear ratio and other information.

Seems my 1997 Ram CTD with 4.10s and 315s is turning about 2200rpms at 75mph.

Looks like 3.55s and 315s will get you into your target range of 1800-2000rpms at 75mph, but I think you are going to sacrifice a substantial amount of lower end power.

CHOP SHOP · Jul 17, 2009

dangerous toy said:
thanks for the replys, i'll check my gear ratio, i thought only the 3500's had 4.10's so i just assumed i had 3.55's

My 2500 has 4.10 gears.

Lucky Jeff · Jul 17, 2009

285's or 295's would be the ticket for you. It's definitely enough of a difference since stock was 245. Had 285's and they worked great with the 3.54's.. I started running 315's and they did ok. Great for freeway cruising, but starting was definitely sacrificed and towing even more so.. Didn't realize how bad it was for towing till I had some 4.10's swapped in. EGT's went way down and it pulled way better on the freeway. RPM's aren't very good down the freeway though. I'm pretty much needing 37's to make these 4.10's perfect.