Tire height help

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dartfreak75

dartfreak75

Restore it, Dont part it!
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I am shopping for tires and trying to decide what height to go with. I am currently looking at 225/70/15 for the rear and 225/70/14 for the front. I am looking at the taller tire because I have 373 gears and I'm thinking a taller tire will be more rpm friendly on the interstate at 70mph. What are you guys thoughts and suggestions. I see Lot of you guys run 60 series tires is there an advantage over the shorter tires? From my research i found a that a 225/60 is 2 inches shorter than a 225/70 what would the difference be rpm wise on the engine?
 
You raise some good points. I’ve used this website for the past decade or two for tire diameter, rpm and speed data (all calculated).

Tire size calculator

I’m running 235/60/14 BFG’s with a 3.23 (or 3.21 and I don’t recall which one it is for a 8 1/4) and it’s not screaming on the highway.
 
I always try to run the same height front to back in case I ever have to put the spare on the rear with a limited slip differential. That way, you don't burn the clutches up going down the road and you can run just one spare.
 
RustyRatRod said:
I always try to run the same height front to back in case I ever have to put the spare on the rear with a limited slip differential. That way, you don't burn the clutches up going down the road and you can run just one spare.
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That's an excellent point. I never thought of that! I guess I could just make my spare a 15 and run the same size tire on the spare as the rear. If I have a flat in the front I can limp it home with a 15 on the front. I'd like to find two more 15 inch rims and run all four on 15s I wish I would have thought to do that when I bought my wheels I would have bought all four.
 
H22A4 said:
You raise some good points. I’ve used this website for the past decade or two for tire diameter, rpm and speed data (all calculated).

Tire size calculator

I’m running 235/60/14 BFG’s with a 3.23 (or 3.21 and I don’t recall which one it is for a 8 1/4) and it’s not screaming on the highway.
Click to expand...
That is is same calculator I'm using lol. I just wonder how the rpm on the tire correlates to rpm on the engine. I know a taller tire will essentially raise your rear gear. And a shorter will do the opposite I'm just curious what two inches would do. I'm sure there is a calculator somewhere to calculate it. I just dont want to be turning 4 grand on the interstate all the time lol.
 
H22A4 said:
You raise some good points. I’ve used this website for the past decade or two for tire diameter, rpm and speed data (all calculated).

Tire size calculator

I’m running 235/60/14 BFG’s with a 3.23 (or 3.21 and I don’t recall which one it is for a 8 1/4) and it’s not screaming on the highway.
Click to expand...
How much tire clearance do you have in the rear with those 235s? I was wanting to go with 235 but was concerned about the leafs rubbing. You have a 75 too so ours should be similar.
 
dartfreak75 said:
That is is same calculator I'm using lol. I just wonder how the rpm on the tire correlates to rpm on the engine. I know a taller tire will essentially raise your rear gear. And a shorter will do the opposite I'm just curious what two inches would do. I'm sure there is a calculator somewhere to calculate it. I just dont want to be turning 4 grand on the interstate all the time lol.
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The gear ratio stays a constant. The only to change that is to change to another ratio. What you are doing with tire diameter is changing the effective ratio.
 
RustyRatRod said:
The gear ratio stays a constant. The only to change that is to change to another ratio. What you are doing with tire diameter is changing the effective ratio.
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Yes changing the amount of distance it takes for the tires to turn one rotation. Kinda like a long legged man taking a step vs a short legged man taking four steps to his one.
 
dartfreak75 said:
Yes I want to! That is in the eventually list!
What are options for overdrive transmissions for la engines. Like within my budget lol
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I don't know what your budget is. But what I would do if it was mine is NOT to put tires on it NOW that will try to act like an OD transmission......IF you plan on upgrading to an OD later on. If you put really tall tires on and then an OD later, you'll probably be out of your engine's RPM range (too low) in high gear at cruise. You'll be jumping back and forth between third and high gear.
 
RustyRatRod said:
I don't know what your budget is. But what I would do if it was mine is NOT to put tires on it NOW that will try to act like an OD transmission......IF you plan on upgrading to an OD later on. If you put really tall tires on and then an OD later, you'll probably be out of your engine's RPM range (too low) in high gear at cruise. You'll be jumping back and forth between third and high gear.
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Thanks I'm not gonna put a really tall tire on it. Its not like I'm putting 30 inch tall tires or anything haha. But I see what you are saying. I found that 235 /60s are only an inch shorter than the 225/70s at 26 inches they are an inch taller than the 225/60s and wider too. I just want to get the right tire size the first time hence why I'm asking lol the overdrive is something I want to do eventually but that's a long ways away I'm not even gonna consider that right now. I will wear this set out before that's ever a concern.
 
dartfreak75 said:
Thanks I'm not gonna put a really tall tire on it. Its not like I'm putting 30 inch tall tires or anything haha. But I see what you are saying. I found that 235 /60s are only an inch shorter than the 225/70s at 26 inches they are an inch taller than the 225/60s and wider too. I just want to get the right tire size the first time hence why I'm asking lol the overdrive is something I want to do eventually but that's a long ways away I'm not even gonna consider that right now. I will wear this set out before that's ever a concern.
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I'm going to run 225 60 15 and 195 70 14 on mine. They are both "around" 24.7" "give or take". But I'm not going to run OD and I plan on a 3.89 gear.
 
RustyRatRod said:
I'm going to run 225 60 15 and 195 70 14 on mine. They are both "around" 24.7" "give or take". But I'm not going to run OD and I plan on a 3.89 gear.
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I really like those tires you posted in the other thread but I cant seem to find them in a 14. I want to run the same size on all fours just the fronts will be 14s give it a little rake.
 
dartfreak75 said:
Those are 13s:p I need 14s. Haha I searched and couldn't find any in 14s in the size I'm looking for they have like 75 series but that's all I see
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I see right now I DO have to do everything. Scroll, moron. lol
 
dartfreak75 said:
How much tire clearance do you have in the rear with those 235s? I was wanting to go with 235 but was concerned about the leafs rubbing. You have a 75 too so ours should be similar.
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It’s close on the rear on one side. If I’m out in the garage today l’ll take a few pictures.
 
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