I saw a third gen Z28 with a set of 295/50R15's on the rear, and he was able to get them so that they didn't stick out from under the wheel well (the bow of the sidewall just slightly protruded, but the tread was under). I was wondering how much backspace can you have on a 15" rim without having to make any modifications. By my calculations, this would have required about 5 1/4" BS, but Chevy High Performance says you can't have that much on a 15" rim. Anybody have this, and if so, what are the specs of your rims.

Thanks for any help.

 

click on the link in my sig. The erar tires are the 295/50/15's before i put the Hoosiers on. it was a on a 15X7 rim. Sorry i don't remember the backspacing. I believe it's about 4 1/2

 

My winter time rims have that size mounte on them. They are 15x7 rims also. I'm noy sure on the back spacing, but I can go to storage and check tomorow. I'd use at least an 8 inch rim though, cause they look like baloon tires on a 7 inch wide rim.

 

Aren't the standard rims 7" (at least on an 84 Z they are). The tire manufacturers recommend a 8-10" rim for the 295's. I was going to go with a 9.5" rim. Even with a 7"rim, the tread is still as wide and without enough backspacing would still stick out wouldn't it? I wish I could have asked this guy what he had, but he wasn't around. I guess what I'm asking is, what is the maximum backspacing you can use on a 15" rim, and not interfere with the stock disc brake hardware, etc.?

Thanks for the reply's

 

Hey CrazyRob75,
I see you are running the tires I would like to run, the 275/60/15 hoosiers. What rim width and backspacing are you using, and do the tires stay in the wheel well and not rub. I had a 82 and 84 cutlass with the 295/50/15 tires on a 10 in wide rim and it rubbed anytime I turned hard, it always pissed me off. I would be happy with the 275's if they don't rub. I'm fairly new to 3rd gens.

 

I'm putting the 295's on the rear only. This is a straight line car. I just don't want to special order 9 1/2" rims with 5 1/4" backspacing and find out they don't fit. Anybody?

 

Blown 83, I'm running them on 15X7 aluminum mod rims. I don't really remember the backspacing. It's been a while since i've had the wheels off. I believe it was around the 4 1/2 mark. I have almost an inch before the tries would rub on the inside. If you went with around 5" backspacing it would be almost perfect. Mine only rub very rarely around really sharp turns, but that might be due to the fact i have NO swaybars. If anything go a little larger on the backspacing as you could always use a 1/4 spacer to adjust them to your liking. 1/4 inch spacer would be perfectly save to provided your lugs still have enough bite on your wheel studs.

 

CrazyRob75: When you say yours rub, are you talking about the tire to the outside lip of the fender? My rear end is actually lifted a little bit, so I don't think that that would be a problem.

Thanks for the info.

 

yes the outside of the tire just barely rubs the fender lip. My car is a Berlinetta so it's not as low a z28 or IROC.

 

I have 295/50/15's on my stock Z28 wheels. I have a ford 9" in the rear, so its length has probably been altered. But they do fit, and dont rub. Only problem with them being on a 7" wheel, is that they buldge over, and the middle of the tyre will wear more then the outer edges.

 

Not sure how much backspace it would take on a F-body but I just got a set of 295/50/15's for the back of the Charger and I had to special order the Cragar S/S's with 5" backspace to make it work from Summit.

Any brand wheel can probably be ordered with special backspacing for a $$... For the Cragar's it was $25 each.

 

What is at issue is that you can only use so much backspacing before the rim starts hitting hardware on the inside. I got under the car and tried to figure how much I could go and it looks like 5 1/4" would be the max but I was just wondering if anyone could confirm that. These will have to be special ordered, but the problem with special orders are that you can't return them. CrazyRob75 has kind of confirmed it, as he says he has 4 1/2" BS with about an inch to spare. If I go 5 1/4", that should leave me 1/4" (I hope).

Thanks guys.

 

You can click on the link in the sig to see how mine fit. I'm runniing 15 x 8 with 4 1/2" BS. The tires are 275 60 15's. I do have approximately 1" of room left and have never had a problem with rubbing.

 

Does anyone know how wide I could go on my stock 16 by 8 wheels on my 85 T/A. Stock they are 245 50 R16.

Ben

 

Here some insight from my messing around:

I run 295/50-15 on my RS....all chassis mods the aftermarket make, except a "K"member or coil overs.

Reason: Had these tires for another project laying around and one of my sponsers (BASSETT) makes wheels and knew getting custom offsets are not a problem and have room for 13" discs.(non D.O.T. legal though)

My offest tool showed 5.25 to 5.75 would do fine static. Using a jack and inducing roll 5.25 to 5.5 was "more" correct.

I tried some 5bs wheels from my late model (for zero scrub front end) for a week, the tire extended beyond the body line..did like the increase in track for day to day driving...high speed stablity suffered...and rub on a hard jounce.

I use 10x15x5.5bs. For this size tire to work correctly my fenders are rolled, my panhard bar has different mounting points (Global West use to sell I think) on the chassis that only allow 1/8" lateral movement max(very tight for a street car!!!).

Without lateral control 295's will rub.

Some more insight...before this project I had 8x15x4bs all around w/ D800 Dunlops tires 245/50-15, my car was better as far as performance...295/50 I can't seem to find any really good tires for daily use..but If your like me (don't need no stinking D.O.T.!!) I keep a complete mounted set of Hoosier TD's(historic racing) 25.5 X 10.0-15 rear & 25.5 X 8.5-15 front that are "treaded" for the fun days!!!

I going to keep the 295's on till the wear bars show. Going to go to a larger diameter so I can use some good tires day to day.

Hope this helps good luck.

 

Thanks for the insight MorgRS. The Z28 is not a daily driver so I'm not terribly concerned with day to day performance. I have two cars in the garage for pleasure. The Z28 when I want straight line acceleration, and I have a 1979 Corvette when I want to go down a curvy road and take the turns fast. Also, I have not lowered the Z28, and in fact, the rear end is raised a little so I don't know that rubbing will be an issue (air shocks that were on it when I bought it). I have the hotchkis LCA's and Panhard rod, but have not made any modifications to the mounting points. So, correct me if I'm wrong, you are saying that the 5.25" back spacing on a 15 inch wheel WILL fit on my configuration. Again, other than the above mentioned mods, there have been no mods to the rear end itself.

Thanks again!!!!

 

i have the 16x8 inch rims on my 89 firebird formula and i was wonderin wut i would need to do to get a 295 tire on these rims. i just wunt them on the back and my stock on the front. thanks

 

8" wide rims use 5 1/8" back spacing.

 

So what kind of rear tires could I put on my stock 16 by 8 rims without ANY rubbing. I have new springs and shocks both just whatever autozone sells, but supposed to be a step up from stock firmness. I have an 85 T/A if it matters.

 

Hey Scrams84Z,

You should be fine (5 1/4" bs) for your setup...
Would have written a response sooner....I was in Alabama
for a race this weekend (2nd place!).

Take it easy...

 

THANKS MorgRS!!! Makes me feel a little better about custom ordering the wheels with 5 1/4" BS, but I won't come knocking on your door if they don't. It's the 9.5" wheels with 5.25" BS then.