How Big a Tire Can I Get Under the Rear of a '68 Riv??

[2 68 Rivs]

Hey all,

I've checked previous posts on this site, and it looks like some folks may have gotten 275 60 15s under the rear of their 2nd gen Rivs. I've got 15X8 wheels with 3.5" backspace (measured), and it looks to me like I've only got a little over 1" of clearance between the outside of the rim and the inside lip of the rear wheel well/molding. I believe a 276 60 has a 10.8" section width, which would theoretically put the tire into the rear wheel well lip if there's 1.4" sticking out beyond the edge of the rim. Maybe it's possible to put a 275 under there because the max tire section width is far enough down that the suspension bottoms before the tire hits the outside lip of the wheel well??

Anyway, I'd appreciate knowing what tire sizes you've run on a '66 - 70'Riv, what wheel you're using (and backspace), and any problems you may have had. I know space is going to be at a premium on the inside too, since the tail pipe has to make its way through. Maybe my best bet is to go with 255s, which would have a 10" section width?

Thanks for any info/advice.

[2 68 Rivs]

Well, I did some further checking this weekend, and it looks to me like the only way a 275 with the wheels I've got (3.5 backspace, 8 inch width) would fit is if the sidewall bulge is far enough down that the lip on the wheel well can't get into it. Has anybody put 275s on their Riv successfully? Thanks.....

[Howrad]

according to THIS THREAD (http://www.v8buick.com/showthread.php?t=165542&highlight=275+riviera), SoCal Adrian has 275s on (i believe) factory rallye rims.
he says his car is slightly lowered, which you would think would give him LESS room for all that tire. how does he do it? :Do No:

[2 68 Rivs]

Howard,

Part of it may be that Adrian's tail pipes come out in front of the rear tires, so there's more room to the inside, but that still wouldn't help the lip on the wheel opening on the outside. From the pic in the string you noted, it looks like there's plenty of room to the outside, which I can't figure. I guess the 6 inch rim would have some impact, and some of the later ones have around 4 inches backspace, so if he's running those wheels that would help. I wish I had a worn out 275 to just mount up and try...maybe some used tire shop would have one.

[Howrad]

:Dou: forgot adrian has side-pipes. kinda funny, since i have them too.
anyway, what you said about section width & lip height sounds right.
the tire SHOULD be far enough below the wheelwell lip to not cause a problem... in theory, that is. :Do No:
wish i could be of more help, but i still have skinny tires on my car.

[2 68 Rivs]

Well, I finally broke down and had one of my old 245/60/15 tires mounted on one of my new wheels (15", 3.5" backspace, 8 inch width) and stuck it on the left rear of my '68 Riv. Plenty of clearance (almost an inch) between the widest part of the tire and the lip on the fenderwell/molding). Based on that, it should accept a 255 width and still have right at a half inch of clearance, so I think I'm going with the 255s. A 275, which would be almost an inch wider than the the 255, would definitely get into the wheelwell lip unless the rear of the car is jacked up with air bags or air shocks, which ain't happening. Hey, anybody know why they don't make 265/60/15 tires? Or at least I haven't been able to find any, and that's with a fairly close search of the internet.

[Woodsters]

Is there any way for you to roll the inner lip of the fender? On my '68 Lesabre, I gained almost 3/4 of an inch by rolling the fender. Doing this gave me extra tire room but then prevents the use of the chrome molding.
I need the traction more than the chrome!
Keep us posted.