what difference will gears make?

[69camarokid]

Yeah, 24" is a little short. Are you running a 245/40 of 245/45? 245/40 are 24.7" tall and 245/45 are 25.7" tall. With a .50 6th, 4.11s are fine.

im running a 245/45R17. My measuring tape was missing last night and i hade to use a one foot ruler so my measurments may have been alittle off.

what's the first gear ratio in your trans? My guess is with 4.11 you will virtually make your car a 5 spd that being 2nd-6th because 1st will be useless

my first gear ratio is 2.66. haha yeah as it stands right now forst gear is basically useless because i dont have a posi yet and im on street tires. I really need a posi and some street radials or im just gonna spins my tires everywhere

[6'9"Witha69]

what's the first gear ratio in your trans? My guess is with 4.11 you will virtually make your car a 5 spd that being 2nd-6th because 1st will be useless

Net ratio in 1st with a 2.66 is 10.93. Between 10 and 11 is good. This is right on the upper end but still managable

By comparison, my 700R4/3.55 is 10.86. If I went 4.11s it would be 12.58!!! That is granny gear for sure!! He would have to run almost 4.88s to get that bad.

[6'9"Witha69]

FYI, with 3.08s your effective 1st is 8.2.

[BonzoHansen]

245/45/17 = 25.7" OD - which seems small for a Camaro

I have a spread sheet I made a while back just to screw around with 'what-ifs'. Attached are 4 different comparisons. One is my 77Z28 from when I went from the ST10 to the T56. The other 3 are T56 vs. 3.73, 3.90 and 4.10 for the 245/45/17 and 275/40/17 tire sizes.

I have a 3.73 now and it really could use a bit more gear. I have a 3.90 on the side for it. But the 3.73 is livable, and the gears really help as I don't have a ton of HP and she moves ok.

I really should web enable this some day. Time is never on my side, lol.

Regarding your rear, if you've never opened it, $25 in oil & a gasket and you don't have to guess, just change the oil and while you are there count the teeth.

[79-TA]

welcome to the world of modern tire sizes. I'd like to get a set of 17 inch wheels for the sake of accomodating modern stickier speed-rated rubber, but nothing will equal the current 26.7 inch diameter I currenty have with me 245/60/R15 radial TA's. I'll use a 245/45/17 when I make the switch, but it'll cost me an inch of diameter (a half inch more fender gap will result.)

You can get the bigger diamaters again once you venture into the nonsensical world of 19+ inch wheels.

[surlyjoe]

255 50 17 is around 27" stock size for imp ss so fair amount of tire choice in that size.

[79-TA]

255 50 17 is around 27" stock size for imp ss so fair amount of tire choice in that size.

I was under the impression those were 225's not 255's, so I never considered them.

[gmjj13]

hey Scott, thanks for the good info. i have 3.90 with a 275/40-18, which is 26.66 tall. by going up an inch in height compared to the 17's, will the rpm go up or down? i am thinking it should go down, but how much of a difference can an inch really make?

[79-TA]

hey Scott, thanks for the good info. i have 3.90 with a 275/40-18, which is 26.66 tall. by going up an inch in height compared to the 17's, will the rpm go up or down? i am thinking it should go down, but how much of a difference can an inch really make?

The rpms will decrease at a given speed. You can see how much just by comparing the different diameters as a ratio. So, if your old tire was 25.66 inches, that means your car will have 96.25% of the rpms that it used to at a given speed. It's just like putting a larger rear wheel on a bicycle.

[BonzoHansen]

Some 17"/18" tires 26.1-27.1

Tire Size	Approved Rim W	Outside Diameter 
255/45R17	8.0 - 9.5	26.1
285/40R17	9.5 - 11.0	26.1
295/35R18	10.0 - 12.0	26.1
335/35R17	11.0 - 13.0	26.1
235/50R17	6.5 - 8.5	26.3
235/45R18	7.5 - 9.0	26.3
245/45R18	7.5 - 9.0	26.7
245/50R17	7.0 - 8.5	26.8
275/40R18	9.0 - 11.0	26.8
255/50/17	7.0 - 9.0 	27.0
285/40R18	9.5 - 11.0	27.0
255/45R18	8.0 - 9.5	27.1

T56/3.90 275/40/17 vs 275/40/18: