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MadMax
08-19-2004, 12:49 PM
My questions are these, 1. Whats the fatest tire size possible on a stock grand national?
2. Largest rim size on stock grand national?
3.Who makes rims compatable with the grand national?
4. Does anyone have a photograph showing how to put these massive shoes on our buicks?

Vacuum 6
08-19-2004, 01:26 PM
My questions are these, 1. Whats the fatest tire size possible on a stock grand national?
2. Largest rim size on stock grand national?
3.Who makes rims compatable with the grand national?
4. Does anyone have a photograph showing how to put these massive shoes on our buicks?

1. 275x50x15
2. I am assuming "largest" means width...I have 15x10

Look at http://www.t6p.com/forums/showthread.php?t=3307

Keller
08-21-2004, 01:39 AM
My questions are these, 1. Whats the fatest tire size possible on a stock grand national?
2. Largest rim size on stock grand national?
3.Who makes rims compatable with the grand national?
4. Does anyone have a photograph showing how to put these massive shoes on our buicks?

1. On the stock 15x7" rim I don't think going past 235/60-15 is wise to retain the stock circumference. People have gone to 275/50-15 on the stock rims, but they barely can be mounted on a 7" rim and it just makes the tires wear badly in the middle. I have 15x8.5" rears, and a 275/50-15 fits nicely. If you don't care about your speedometer/odometer readings, and don't care about frame notching or inner-lip rolling, anything might be possible.

2. A 15x8.5 is sane. A 15x10 is possible if you pay attention to offsets and clearances. I've heard of 16x8 and 17x8.5 without any real mods. Some 18 or 19 HREs, but with clearance work. When a car has been backhalved, you might see 16x30s out back. :eek: I'm sure more has been ventured.

3. Anything that is a 5x4.75 RWD bolt circle should and something in the vicinity of 4-4.25 backspace should fit.

4. Hmmm...looks like our wheel guide didn't get moved. I'll work on that...

You know those "Dub City" miniatures are just models, right? ;)

Vacuum 6
08-23-2004, 01:46 PM
I had 275x50x15 DRs on 15x7 for 3 years…no odd wearing problems.

Fast One
10-02-2004, 11:28 PM
I have an 87 GN and I'm running BFG Radial T/As front & rear on factory rims. 235/60/15 up front, 275/50/15 in back. I have only about 1/4" clearance from the inside of the sidewall to the frame rails on either side. No rubbing, as I also have a PST graphite bushing kit. I have been using the 275s out back for a number of years now, and am getting approx. 30k miles out of them (mainly street use -- a few burnouts here & there, a few stoplight races here & there, lots of quick trips to the grocery store, a few vacation trips here & there). My first set of 275s did wear out the middle quite early, but I dropped the pressure to 28 lbs on the second set, and they wore much more evenly -- although the middle did still wear a bit quicker than the outer tread. I just put on a new set 2 weeks ago! :) I'm thinking of runing them @ 26 lbs.....

I have read about guys using 4 front 16" TTA-style rims, and going with 245/50/16 rubber in front, with 255/50/16 rubber in back. (Just like the GNX had). It's supposed to be direct bolt-on -- the 245s won't rub on full-lock turns, and the 255s out back are very close to the stock rolling diameter.

Hope this helps!

Keller
10-03-2004, 12:32 AM
My first set of 275s did wear out the middle quite early, but I dropped the pressure to 28 lbs on the second set, and they wore much more evenly...

What width rims were these on?

Turbo2nr
10-03-2004, 07:49 AM
I would never put 275s on a 7" rim. That is not right. I have 275s on a 8" rim, and that is still a little tight. Rear offset should be half of rim width. Right in the middle. 28"-26" 11.5 dot drags/ or 28"-26" 10.0 real slicks will fit.

Fast One
10-03-2004, 10:37 AM
What width rims were these on?

Stock '87 GN rims. Been doing this for years now with acceptable results. Like I said, I do put up with a bit of early wear in the center of the tread, but not much. For instance, the set I just removed were at the wear bars in the center, and approx. 1/8" from the wear bars in the outer tread area. I ran that set @ 28 lbs cold. I'm going to run the new set @ 26 or 27 lbs. and see if that helps to even the wear a bit.

Turbo2nr
10-03-2004, 12:00 PM
I think that would look a little silly,but what ever. Go to G-body parts.com and get a wider stock appearing rim. For a small fee, they will cut your rim and add a steel spacer to what ever width you want, even go smaller for skinnies in the front.

Scott

Keller
10-03-2004, 02:43 PM
Pretty sure the GN wheels are widened by welding a completely new hoop on the GN center section. Truedesign in Colorado has been doing that for years. The T wheels have to be cut and a section welded in, increasing backspace.

I would not reccomend running a 275 on a 7" rim for safety concerns. Get your rims made into 8" or 8.5" and run a decent pressure.

Fast One
10-03-2004, 07:41 PM
Scott...

The people that have voted for my car in various car shows must not have thought that my tires looked silly, otherwise I doubt that I would have won any awards (which I have). Also, the guys that lose to me at the track don't think it's silly when I can lay 403 RWHP and 485 lbs./ft. of torque (dyno numbers in overdrive) down on the track and hardly spin my full-tread street tires.

Keller...

I know that a 7" rim is on the narrow side for 275s -- can't afford a second set of rims right now -- lost my butt in the stock market. I don't spend much time at triple-digit speeds (except on the back half of the 1/4-mile) and I don't drive in 90-plus degree weather very often, so I don't think I'm pushing it, safety-wise. Also, I am not new to the hot-rodding scene -- I have been racing Buicks since 1972.

Best regards,

tta299
10-09-2004, 10:59 PM
(My tires dont look silly ) they look wide ass hell sleeper style on stock rims 275/50/15 BFG DR's 50 passes and about 5,000 miles still 1.6 60ft.
no wear problems Slick all over. ( If it works why change )




26/10/15 ET STREET they do wear in the middle bad unless you run low pressure.