275/50/15 killing 1/4 mph

[UNGN]

What psi did u run in the 275 60-15

16 to 18 psi works fine at the track.

24 on the street.

 

[Amelio]

I have been deciding between the two sizes also....I just went to the track a few weeks ago for the time trying to work on my tune. I am running a 275/50/15 BFG DR and I was trapping 115 @18 psi I want to start going more boost but at the top of third I was hitting my rev limiter right at 5600rpm.

I think from what everyone is saying I need to go to the 275/60/15 and gain 2" taller to get the revs down.

 

[blacksix]

11.50@118 with 275/50 Mickeys, 1.65 short time. All I have is the OEM tach with a few missing lights, so I have no idea what she was revving. TC was locked, though.

 

[bison]

Even with those tires? And how do u go about locking the converter? And when do u do it? Half way threw 3rd I'm guessing.

FYI I plan on leaving on 7-9# on the trans brake Maybe 10# bc at 10 my vig stalls at 3000rpms exactly

Id try to keep the engine rpm between 4500 and 5100. Use the online calculators to calculate your zero slip rpm in 3rd and just try to get it to drop to 4500 when its locked. You will probably be best locking at 103-105mph with those tires. Trapping higher than 117mph will be easy if the tune is good and the boost is up. Plan on high 20's for 119-120mph. Cam and heads would net a lot at this point. Your vig seems tight down low if its only 3000 at 10psi. Not the usual from what ive seen.

 

[bison]

On a perfectly prepped track, a 50 series tires should 60 ft quicker than a 60 series tire

Not if the car has the power to pull through the taller tire. Its a hell of a lot harder to get a better and consistent 60' on a 26" vs a 28". When building a car that has any appreciable power you would pick the tallest widest tire you can ge tin there and then gear the car for the quarter mile.

 

[Amelio]

11.50@118 with 275/50 Mickeys, 1.65 short time. All I have is the OEM tach with a few missing lights, so I have no idea what she was revving. TC was locked, though.

Well that is somewhat of an issue for me because I do not have a lock up converter. I was not able to watch the tach (on scan master) to well going down the track but every formula I plug gives me 5600rpm @115mph with a 26" tall tire. The only thing that makes sense to me is go to a 28" tire basicall the 275/60/15

 

[northerngn]

What psi did u run in the 275 60-15

i ran 18psi at the track
30 on the street
-dan

 

[Onalky87]

Your vig seems tight down low if its only 3000 at 10psi. Not the usual from what ive seen.

Is that a bad thing bison? I was told it's a 3200 stall

 

[bison]

Is that a bad thing bison? I was told it's a 3200 stall

Its not a typical stator/ pump configuration found on TR's. A vig at 10 psi is usually over 4000. The converter isnt very efficient anyway so you will need to lock it to get any good mph.

 

[Onalky87]

So should I change it? Or run it a few times the way it is first? Also, what could be the negitives about that happening