Rpms tire size and different rear axle ratios graph
 

Guys I seem to recall years ago seeing a graph on here that someone posted that showed the effects of different rear axle ratios , tire sizes and rpm at a certain speed. I can’t find it.
Has anyone got access to that? Thanks Dan

Re: Rpms tire size and different rear axle ratios graph
 

I found this over on the hamb

Re: Rpms tire size and different rear axle ratios graph
 

I’ve used this website. Plug in values for tire size, differential ratio, RPM, speed. Plug in any 3 values to get the fourth.
http://www.advanced-ev.com/Calculators/TireSize/

Re: Rpms tire size and different rear axle ratios graph
 

If you have the 1950 revision (green bible) of the Ford chassis parts catalog from 1928 to 1948, you will find a basic chart in there for the speedometer drive gearing.

Re: Rpms tire size and different rear axle ratios graph
 

There have been several threads about axle ratios, engine speed, and road speed over the years. One thread that had lots of discussion is this one: https://fordbarn.com/forum/showthrea...5747&showall=1


For quick reference in this thread see the table below. Since this table is probably not easy to read in this forum I have also attached this as a pdf, which you can download for easier viewing. All these ratios are for 28 inch tall tires.
https://fordbarn.com/forum/attachmen...7&d=1733832057

Re: Rpms tire size and different rear axle ratios graph
 

38 Coupe, thanks for that comprehensive chart. I have a 26% Mitchell in my 40 DeLuxe with a 4.11 rear end it's interesting to see the rpm drop in overdrive.

Re: Rpms tire size and different rear axle ratios graph
 

Yes thanks for the pdf, great chart!
My buddy is building a blown flathead, 3 speed with an 8” rear axle, he’s trying to figure out the best ratio to suit his setup. Dan.