Ok i have switched my rearend gears to 3.27 and it threw off the speedo a lil use to be 3.08. My question if i could find out in the equation section what tire radious i would have to be goin the mph i am. Could i just get custom wheels and tires with the radius it says and that fix my speedo cause ide like to have bigger wheels anyway. Think that would work?

 

I would prob also just get the back wheels bigger like a vette. Also what is stock tire radius

 

Anyone? Here r some mph's and rpm reading i took
2nd gear- 29mph 3000 rpm
3rd gear- 44 mph 3000 rpm
4th gear- 58mph 3000 rpm
5th gear- 60mph 2000 rpm
5th gear- 91mph 3000 rpm

 

You should be able to just change the speedo gears. larger tires won't really have an effect on your speedo that much. On my RS when I went from the stock ones to my 17's the speedo went off about 2 mph.

 

yeh but even tho u went to 17's the tire radius was still close right. I was talkin about gettin a bigger tire radius. Like a 19 with a side wall u usually have on a 17. Or somethin i dunno if u could get it close that way but just an idea i had. I cant change the gears either cause its electronic ide need to get somethin to calibrate it.

 

Well I do know that my tires now are right under 26" tall. That is considerably taller than the stock junk that was on the factory 15's. I can't remember what size came off of those. The gear swap will throw you off more than anything.

 

Tire size plays just as big a role as your gears do. Stock sizes ranged from about 25.7 inches to about 26.1 inches I believe. Going smaller would be like putting in more gear and vice versa.

 

Would u be able to get some big enough to fill in the gap goin from a 3.08 to a 3.27. I think it would look good also with bigger wheels in the back.

 

I'm not totally sure, but you prolly could. Although it would negate any gain from the gears making what you just did pointless. Do the calculations and find out what works, but tire size can change a lot of things.

 

Yeh but i really just changed the rear for the posi and the disc. I did try putting in that info in the equations and it doesnt seem to come out right i dunno maybe im not doin it right.

I have info sheets on 90 camaros this is what it says my transmission ratio's are
1st gear - 2.95
2nd gear - 1.94
3rd gear - 1.34
4th gear - 1.00
5th gear - 0.63

 

You have the gear ratios right but 5th is .62. Anyways what is your current tire size now?

Lets say you have a 245 50 16. With your 3.08 gear and that tire in fourth you could go 121 at 5000 rpm. Now switch it to a 3.23 gear and you can go 115.

Now say you still are at 5000rpm in 4th but go to a 275/45/17 tire you can go 121 with the 3.23's and 126 with 3.08's.

So there is about a 5 to 6 mph difference in speed now between the two tire sizes and gear sets. So they are actually pretty close and a bit farther off than I previously stated.

So to break down my example in 4th gear at 5000rpm
With 245/50/16 tire
3.08 = 121
3.23 =115
With 275/45/17 tire
3.08 = 126
3.23 = 121

 

Do a search on my userID and the phrase "SMUC". You'll learn more than you probably really want to know.... like ask a guy the time, he tells you how a clock is designed.

 

Wait so ur tellin me if you have a electronic speed you can still change the speedo gear. I never knew that every made it out like you could only do that on the cable driven ones. I would need to figure which 1 i need tho. Altho bigger rear wheels would look nice.

 

There is still speedo gears with electric speedo. I have a 90 with the electric speedo but it still requires speedo gears so that it reads the correct imput.

 

Yeh i just wasnt sure how it worked.