Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 

Thread: tire size makes RE ratio change how much?
          
   
   

Reply To Thread
Results 1 to 4 of 4
  1. 08-30-2010 12:35 PM #1
    Dgas56's Avatar
    Dgas56
    Dgas56 is offline CHR Member
    Visit my Photo Gallery
    Join Date
    Oct 2005
    Location
    Mnpls
    Car Year, Make, Model: between cars
    Posts
    348

    tire size makes RE ratio change how much?

     



    3:89 Re w 26" tall tires, but they are too narrow. So I want to put on 275 60 15's which are 28' tall. Clearence on the car is not an issue there is plenty. given the added dia. I am sure rpm will decrease some. Which will not break my heart. Those 3:89's make the engine howl pretty good at 70 MPH (459 dyno'd w drivetrain load HP). But how much will the added 2" change it?
    Last edited by Dgas56; 08-30-2010 at 12:38 PM.
    Attended my first drag race in 1961 and hooked on cars ever since.
    Reply With Quote Reply With Quote
  3. 08-30-2010 12:40 PM #2
    skids72's Avatar
    skids72
    skids72 is offline CHR Member
    Visit my Photo Gallery
    Join Date
    Dec 2005
    Location
    Lafayette
    Car Year, Make, Model: 68 Firebird 439 BBC
    Posts
    745

    the difference will be proportional to the change in tire diameter: 3.89:1 with 28" tire = 3.61:1 with 26" tire.... at the same MPH, the RPM will drop 13/14ths (26/28ths).

    -Chris
    Paint don't make it no faster
    Reply With Quote Reply With Quote
  4. 08-30-2010 12:50 PM #3
    rspears's Avatar
    rspears
    rspears is online now CHR Member/Contributor
    Visit my Photo Gallery
    Join Date
    Sep 2007
    Location
    Gardner, KS
    Car Year, Make, Model: '33 HiBoy Coupe, '32 HiBoy Roadster
    Posts
    11,174

    Skids typed quicker than me With your 3.89's and no OD (1:1 final tranny output) you'll turn 3519rpm at 70mph with 26" tires, and 3268rpm with 28" tires which is indeed exactly 13/14th's change.
    Roger
    Enjoy the little things in life, and you may look back one day and realize that they were really the BIG things.
    Reply With Quote Reply With Quote
  5. 08-30-2010 08:51 PM #4
    randyr's Avatar
    randyr
    randyr is offline CHR Member
    Visit my Photo Gallery
    Join Date
    Feb 2007
    Location
    Santa Monica
    Car Year, Make, Model: 37 Ford tudor humpback
    Posts
    1,988

    Here's a great little calculator to figure it out..http://www.ringpinion.com/Calc_RPM.aspx

    Plug in all the different combos you want and see how it changes your rpms....
    "It is not much good thinking of a thing unless you think it out." - H.G. Wells
    Reply With Quote Reply With Quote
Reply To Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts

Forum Rules

Links monetized by VigLink