26 or 28 inch tires?

[86BLACKT]

When is it time to switch from 26 inch tall tires to 28?

 

[jgme]

As your quarter mile trap speed is getting over roughly 115 mph might be a good time to switch over to 28"D tires. The assumptions are

around 5400 rpm redline
a little slip in the torque convertor
third gear (not overdrive)
stock final drive of 3.42:1

 

[UNGN]

Even locking the converter, my car never ran over 114 with 26" tall tires. Ever. I should have switched to 28" tires at 112 mph.

28" tire will work fine even with a stock turbo. On a slick track, you can leave with more boost than with 26" tires, making up for any mechanical advantage the shorter tires would have out of the hole. On the big end of the track, 28" tires will allow the car to pull harder through the traps. Peak HP with a stock motor is only about 4400 RPM and it falls off a cliff above 5200.

With ported heads on a sticky track, 26" tires will work probably work better until 116 or so, but above this, I'd go with 28" tires. On a slick track, 28" tires all the way, no matter what your car runs.

 

[tim87tr]

Definitely with your combo use some 28s. As stated you can run 28s on a stock turbo car. See my website on the Dark Red 87 T.

 

[Robes87GN]

I hate to hijack your thread, but my question is exactly what you are asking.

I have:
ported heads
comp cam 980 valve springs
stock turbo
built up trans
stock IC
3" dp
2 1/2" ATR Y exhaust
Competition Engineer 3-way adjustable shocks
--- lots more but no reason to list ---

I ran 12.8@104 before valve springs, trans, and port work
I ran 13.0@108 spinning and running out of gear (I think spinning made me shift too early which caused me to run out of gear) with valve springs, trans, and port work

This has all been on 26" nitto 555r dr's

Should I go to a 28"?

 

[UNGN]

Originally posted by Robes87GN
I hate to hijack your thread, but my question is exactly what you are asking.

I have:
ported heads
comp cam 980 valve springs
stock turbo
built up trans
stock IC
3" dp
2 1/2" ATR Y exhaust
Competition Engineer 3-way adjustable shocks
--- lots more but no reason to list ---

I ran 12.8@104 before valve springs, trans, and port work
I ran 13.0@108 spinning and running out of gear (I think spinning made me shift too early which caused me to run out of gear) with valve springs, trans, and port work

This has all been on 26" nitto 555r dr's

Should I go to a 28"?

I would. If you are spinning 26" tires, 28" tires will help.

Nitto 275/50's are actually short. They are 25.7" instead of 26.1" like the BFG's and only get smaller from there (they have more tread than the BFG's so will go down to 25.5 when worn).

 

[Robes87GN]

Thanks.