New 15” Wheels. What gear ratio?

[gungfudan]

It has been a while since my last post hello everyone. My friend gave me some wheels and tires off of a 99 Mustang. The tires were an OK condition but one of them ended up developing a bubble probably because they’ve been sitting so long so I got new tires. I got 225/75R 15. I’m looking at changing the gear ratio in the rear end what gear ratio should I go with? I was thinking 3.73. I have a 94 Mazda B 3000. My current gear ratio is 3.43 I believe.

 

[19Walt93]

Thank you for calling them wheels instead of rims, the rim is only part of a wheel.
You can look up the diameter and revolutions per mile for the old tires and compare with the 15's. For example: if the old revs per mile was 800 and the 15's show 700, 800/700=1.1428 I expect your current gear is 3.45 if you have a 7.5 so 3.45x1.1428= 3.94. My revolution numbers are random to use as an example, a tire catalog would have more accurate numbers.

 

[SenorNoob]

These are probably way more complicated than you need...

Gearing Analyzer with Shift Tracer

Enter gear ratios, tire and diff ratio to analyze RPM vs velocity at shift points with tracer

www.blocklayer.com

Tire Size Comparison

Calculate tire diameter from code and compare tire size speedometer differences

www.blocklayer.com

,but super handy. There are other calculators on that site. Good fun to do some digging and find other useful things. I think it was originally built for construction. (Roof pitch, 2x6 vs 2x8 floors and walls, etc.)

 

[gungfudan]

Thank you. Looks like 4.10 ring and pinion.

 

[alwaysFlOoReD]

There are calculators on TRS as well. I've used them lots.