Gear swap or tire swap?

[themechanic]

Ordered MTs today. Seems odd none of the 3 major tire stores carry them.

I started another thread about the tires I ordered here: https://www.forbbodiesonly.com/moparforum/threads/check-the-date-of-manufacture.182029/

Long story short, I received four old tires and returned them.

 

[BSB67]

Never understood chasing rpm with tire diameter. Two separate things. Put on the tire you like, gear as needed. All this for 5.3% change and 150 rpm?

 

[themechanic]

Never understood chasing rpm with tire diameter. Two separate things. Put on the tire you like, gear as needed. All this for 5.3% change and 150 rpm?

I took advantage of the lower RPMs since I needed new tires. If that isn't enough, I'll change the gears.

 

[BSB67]

I took advantage of the lower RPMs since I needed new tires. If that isn't enough, I'll change the gears.

Sure. If your buying tires anyways.

 

[themechanic]

I would like to hear from the guys using 17" and up wheels to see their RPMs vs. MPH or KPH if you gauge it that way.

 

[BSB67]

I would like to hear from the guys using 17" and up wheels to see their RPMs vs. MPH or KPH if you gauge it that way.

Of course wheels have nothing to do with it, other than maybe give a larger universe of tire size availability.

The cars are designed for a 27" tall tire. You can go probably 1" either way and still have it look relatively "correct". 29" and you run out of wheel well without moving stuff, and at <26" it looks a bit odd unless your going for the lowered look.

 

[themechanic]

Of course wheels have nothing to do with it, other than maybe give a larger universe of tire size availability.

The cars are designed for a 27" tall tire. You can go probably 1" either way and still have it look relatively "correct". 29" and you run out of wheel well without moving stuff, and at <26" it looks a bit odd unless your going for the lowered look.

I figure the guys running wheels that big and bigger have made mods to the spring location and/or body. So, that makes it relevant in my view.

 

[BSB67]

I figure the guys running wheels that big and bigger have made mods to the spring location and/or body. So, that makes it relevant in my view.

Well, yes and no. The wheel size still has nothing to do with rpm. You can get a 33" dia tire for a 15" rim. Just back half the car.

 

[1967coronet]

From 25.5 tire to 28" tire is 10% increase same as from 3.55s to 3.23s .
But I don't think anybody would ever put a 25.5 on a Coronet.
The point is that from min to max on the tires is about the same as 1 gear swap. From 27s tho, you'd have to go to a 29.7, to affect the same gearchange. So IMO not really doable.

With an automatic, you're likely better off with a loc-up convertor , 5% slip at 3000 rpm is 150 rpm or half a gear swap.

Not sure why you think a 25.5 tire dia will not work on a coronet ?
My old 67 has 245-60-14s on the rear they are 25.6 dia. and fit fine
You could even change a flat tire on the side of the road if needed. lol

 

[themechanic]

Lots of folks have the 295/50 15s and they are 26.6. I think that he meant 26.6.