is a 255/70-15 too tall of tire fore a 2.56 rear?

[knightowl73]

im running a 350 trans, non-lockup and was wondering was it too much tire. i dig the look, but want a fatter tire, not necessarily too small that it looks funny tho. i dont plan on dropping the truck any more at all, but i think a 295/50 would be too small. plus it would actually be a bit smaller than my 225/70-15 fronts. a 275/60 looks like my only choice, but would it be too tall still in your opinion? its only a tad bit smaller. id like something around the same height as my fronts that still looks wide. could i get in the 3.23 range or so with a decent looking tire size change? just wondering, tires are all pretty new now, but looking for a different look for the rear.

[SCOTI]

225-70's are approx 27.5"
275-60's are approx 28"
255-70's are approx 29"

295-50's are approx 26.75" & as you suggested, too short. I would do 275's to get things as close as possible. It's definitely not going to be a bullet off the line w/those gears but might be decent on the hwy @ 70.

28" tall tires w/1.00 trans ratio & 2.56's = 65mph @ 2,000rpm; 81mph @ 2500rpm. If the motor is stock you will prob be ok as sbc's like 22-2500rpm range.

[knightowl73]

oh its nice on the highway now, can hardly hear the exhaust and it just floats. still only get about 8.5-9 mpg tho, but i know i cant change that much without a motor swap, which mine is close to that soon too if i dont do some upgrading to mine.

[benoit454]

it's just gonna be a dog off the line, we got almost the same setup, 84 c10 255/60's 2.73's and th350 non lockup and it sucks. Highway is good but not around here too many hills and such and mostly around town stop and go.

[knightowl73]

yes i am fine with the dog off the line thing unless i can get better milage on the highway somehow. with the mileage i get now scared to jump up and get another rear-end, this is lovely compared to the 4.11 rear i swapped this one for. and i think a small stall converter would help, but not much. or am i wrong?

[SCOTI]

Keep in mind that less gearing multilplication does not always = better milage. More than 1 4x4 has lost mpg's when installing large diameter off road tires but gained it back by swapping in a lower (higher numerical) gear.

It's all about the package, not 1 specific component.

[68longhorn]

my 78 caprice has 2.41s in the rear and 255/70 tires. With a 330hp 350 and th350 i get 20+mpgs but my best 60' was a 2.39 with no tire spin.

[knightowl73]

yeah my motor needs an upgrade and just that might pick me up some mileage. wish i knew what its hp output was at now. its not completely worn out, still dependable as hell, just seems to lack the horsies, even when i had the 4.11s it was fun but not near what i was expecting, it was definately lacking. i think my mileage is so bad cus i waste alot of gas trying to "keep up", it drives as if the wind is always blowing against me.

[benoit454]

a stall aint gonna help anything with those highway gears.

I can't beleive you took a 4.11 out for that. if I had known that and we was close we could have traded straight up, my old man wants a 4.11 in his 84 but he has 2.73 in it now. he ended up buying some 3.90 gears to put in it.

[knightowl73]

well i didint want it with such a bad gear, but it was free and i just couldnt afford to go anywhere if it required me to get on the highway. i had to do something. im still looking, but skeptical as to what is perfect for me. id rather get the best possible highway mileage i can with whats available to me in my budget and hopefully not a whole lot of work. i do drive the highway alot but at this point, a overdrive tranny is out of the question, i just rebuilt my 350 trans a few days ago. so im looking into other alternatives

[knightowl73]

i shoulda swapped in my 283 while i still had the 4.11s out back, woulda been real fun and prolly not too bad on gas i suppose as now. i really wanted to, but the 283 wasnt even in my possesion yet and i needed a quick fix so i could cruise the highway. now i have the motor, but the rear-end is long gone. still thinking about it, but not with the 2.56s out back, no way.

[benoit454]

if you need highway that much better look into narrow tires, more mass on thw wide ones but the taller tires should bring the ratio down lower numerically. IMo if you need it that bad and that much you need an od and should have got it instead of rebuilding the th350. What about the motor? done anything to it? Might want to do plugs, wires, cap, rotor, check timing, check the advance unit, tune the carb, maybe rebuild the carb, compression test, all that to make sure it's working good. if everythings in decent shape and all with that kinda mileage seems like the plugs would be dead or a crankcase filled with gas. 8-9 mpg sucks, our 84 robably gets that or something, I'd think better, but it's got a comp 268 cam, and does alot of stop and go around town with 2.73's, weiand intake, dual plane, and edelbrock 600cfm carb, mostly everything else is new.

[knightowl73]

yeah i think my motor has some issues, which i have not yet diagnosed. but i cannot make it run well at anything other than 8*, dont know much about it, besides the apparent bolt-ons and a supposed elgin cam inside. i will do some diagnosing soon though. i do have the 283 almost ready to swap if need be, that is if the motor is totally shot and i decide to go with it. dont really want a 305 in it, and thats in another project i dont want to yank the motor from but it might be more practical. down low i dont think the 283 would do as good as whats in it now, and id never see the benefits of the 283 with the gear i have now.