"Tallest" tire for 70 gs with no mods

I've been searching and cant seem to find a difinative answer to this. I have a 70 gs and I drive it on the freeway a few times a week. I have 235/60's on the rear right now, and at 70mph im at 3k rpm. Im looking to drop the rpms as much as possible, so I figured tires would be the cheapest way to go. I'm looking at BFG 255/70's right now and theyre listed at 29.1" tall and 10.2" wide. will these fit in the rear without rubbing anything? and what backspacing should i be looking at? I'll probably put them on a 7.5" or 8" cheap steelie for now. and how much of a drop would I see in rpms going to a 28" or 29" tire(at 70mph)? the car is a 70 gs 350 with the stock posi rearend(not sure on the gears)

 

try this site - http://www.rimsntires.com/specs.jsp - they have a comparer that you can put different sizes in to see what effect on rpm's etc. You can pick the 70 skylark as the model from the available pulldown choices.

Good luck..

Dan C.

 

Cool thanks for the link, looks like I'd drop about 400rpm with the switch, which would help. So the big question then is will a 255/70/15 fit without rubbing?

 

I run 275'- 60S OR 295 -50'S and have no rubbing issues on my 70 GS

 

I have 275/70/15 BFGs on the rear with no problems

 

You can run a 28" tall tire with no issues. After that, you're tempting fate to be rubbing up in the inner fender.

 

I used to run 255/70-15 tires on factory Buick rims on my 70 when I had 4.10s under it. The only times I would get it to rub was when the body/rear were torqued way out of kilter, such as driving over a ditch sideways when one wheel was dropping out of the wheel well and one was pushed up deeply into the wheel well. I alleviated it with a little cosmetic hammering on the inside areas that it rubbed. The biggest reason it rubs is because the tires have a lot of sidewall and it can wallow a bit.

 

with the 295/50 what width rim do you use and what offset.
thanks

 

I have 285/70/15 on 10" wide rims on my 70 Skylark. I am pretty sure the backspace is 5.5"

 

I use this size with a 16" wheel.

 

325-50-15 on 15x10 with anywhere from 5-5/8 to 6inch backspace

if you want springs that'll make those baby fit with no rubbing or assistance from air shocks pm me.
these springs should fit 29in tall tires pretty easy too

same spring rate as original springs just 2in taller free floating height!

 

What do you consider no mods? I run 29.9 x 11 on 8.5w Centerlines with 4-5/8 backspace. I did a slight roll on the fenders only.

 

Tallest 15 inch tire I can find is a Firestone 500 255/70/15 @ 29.1 inches tall.

 

Wow, thanks for all the replies. Anyone have pics of their cars with taller tires?

 

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Joe, nice ride..

What rim size are you running on the rear? 16" x width ? X backspace?

Any spring mods or body mods to make clear?

Thanks,, Dan C.