Just installed a tach in my car. It is a GS350. At 60MPH I am taching only about 2600rpm with 205/70-14 tires. This is a pretty low ratio gear isn't it? Would 3.23 sound right? Thanks, DB
Not to me. I'd say you are in the 2.xx range. Jack up the rear (support it on jackstands!) then put a chalk mark on the tire and the driveshaft. Now spin the driveshaft until the tire has gone exactly 1 complete revolution. Count how many times the driveshaft spun. If it is not quite 3 full revolutions, you are at 2.xx, and if it goes 3 and 1/4 revolutions you are at 3.23. If it is just about 3 and 1/2 revs you are at a 3.42 ratio. With a 25" tall tire my Riv revs 2000 around town (my speedo is waaay off, but I'm guessing it to be around 50 mph).
3.23's it is. DB, I would say you have the 3.23"s My 70 GS has the 3.42's with a 27" tire and it turns 2600 at 60 MPH. I know my speedo is right on because I have the right gear in the trans for mr rear and tire height.
Check out this link. Fun to play with. Although it will come up File Not Found, the tabs still work. http://www.smokemup.com/utilities/calc.cfm
Those tires work out to 25.3" tall (in theory). (((205*.70)*2)/25.4)+14=25.3 If I scale from my car (60 MPH = 2050 RPM with 225/70/14 tires and 2.56 rearend) I get 3.37 : 1 And since there was no such ratio, you're guess is as good as mine... -Bob Cunningham bobc@gnttype.org
i have a cool spreadsheet i made on this subject ... anyone who wants it email me at itsyuk@aol.com and i will attach it to an email ... you need microsoft excel to use it. you can compare rpms at various speed in various gears with different tires and rearends etc.. its pretty cool.:bglasses: :Smarty:
I used the web site to Randy's Ring and pinion. They have an RPM calculator where you input tire height(25.3), gear ratio(3.23), and speed(60MPH), and they give you RPM. When I did this I got 2643 RPM for a 3 speed automatic. I say DB has got 3.23's
