back to smaller dia rears

[elevensies]

well after trying out 30x9x15 stiff wall hoosiers, iv decided to go back to 28x10x15 2ply

seems my 60' @1.61 on 30" tall tyres work ok,
its elsewhere i feel im really loosing out, mid to top end speed, i think (dont quote me on this as im never concentrating on my tach) im trapping at 4500/4600 rpm, and i need to be 1000 more, and my mph is around 5mph down @112??? from 117mph

hopefully next weekend will show up my results, im going to install a camera to capture the rev range

any thoughts?
oh and my gearing is 3.91,

 

[Jerry Hall]

You have effectively lowered your rear end ratio with the taller tires. A 4:10 ratio would probably put you back where you started. Ofcourse a lot more figures into it. Max HP, torque #'s at what rpm for starters. It's human nature we are always looking for more and quicker.

 

[Cranky]

The % difference in tire size vs % difference in gear ratio you need to go to. If the car is stable with the taller tires, then that's what I would try. But crossing at 55-5600 still sounds low to me. Watch your tach on the top end and drive it out the back door. Is it still climbing at a good rate?

 

[elevensies]

i need to start looking at my shifting rmp, as 2nd is possibly too early, i know in my heart my motor is still climbing when i shut off,

food for thought thanks

 

[383man]

I run 4.30's in my 63 with the Hoosier radial 30 x 9 x 15 slicks. They work good for me with my combo and gearing. I cross the stripe at about 6400 rpm with my 440/493 combo. I don't know your combo but it sounds like to much tire or not enough gear for that size tire. Ron

 

[Frank Mopar]

I don’t think anyone can predict you trap speed rpm without knowing what you have for a motor, trans, converter etc.