The Stovebolt Site Forums The Shop Area The HiPo Shop Wheel offset...what have you used?

I've mounted a '81 Camaro 10 bolt rear to my '50 3100. As I recall, it is an inch wider than the original. I plan on using 15" wheels. I've seen the charts for measuring wheel offset. I plan to use Torque Thrust wheels. I want to get as much tire and wheel as I can INSIDE the stock fenders...3/4" to an inch gap of the tires on the inner and outer sides of the fender would be acceptable to me. What combo's, (tire and wheel size), have any of you used?

What size tire are you considering using? What width wheel?

Out of curiosity, what is the ratio of that differential?

You'll need to know what width wheel your thinking of running and width of the tire. Figure out how much you can realistically, shove between the inner fender and outer lip. From there, you can use a ruler to measure your inner fender to hub rim mount, subtract for gap, then figure out your back space from there. After that, adjust your rim and/or tire width accordingly.

TUTS 59...I'm looking at an 8" wheel with the possibility of 255/70/15 tires. 255 would be the max, I believe they would mount about 10" wide...might have to drop that down to the 245 range. I saw the 255/70/15's on a late 40's stovebolt at a car show in Gulf Shores, Alabama last winter. I liked the look...they took the whole fender. The truck had a ten bolt under it.

Rocket man, that is the size I have for my '59 3100. Actually I have 60's on 8" Ralley wheels. I have a 10 Bolt from a '72 El Camino, the track on it is 1 inch narrower than the stock axle. Sorry no pictures of the wheel/tire mounted, of course mine is a Task Force as well.

I don't have an AD truck... mines a 40 with a 71 Chevelle/Lemans width 10 bolt. I'm running a 255/70R15 on a 7inch wheel with a 3.76 backspace. I tried an 8 inch with 4.5 backspace on a 275/60R15 and it rubbed ever so slightly when the suspension cycled.

I'm using a '78 Camaro rear end which should be the same width as your '81 rear end. Wheels are 15 x 7 wheels with a 4.25 backset. Tires are 205/75R15. The tires have rubbed just slightly on the box side - made marks but didn't rub the paint off - this would have happened under hard cornering. Therefore, to use wider tires than I have, you would have to decrease the backset to widen the track.

The drivetrain on my AD is stock and I'm running 255/70/15 tires on 15 X 8 wheels with 3 3/4" backspace. No rubbing ever.

Curt B. My drivetrain is modified. I've put Posie 3" dropped leaf springs on the rear and a Speedway IFS with a 350 small block. The truck I saw with the 255/70/15's looked exactly like 32vsnakes '40. I can't recall if the guy used lowering blocks or modified springs...it did appear to sit approximately 3" lower than stock.

You've got a lot of variables going on there...the place I bought wheels and tires from mounted a gizmo to the hubs and swept the fender wells. They then told me that if what I bought from them rubbed they would give me my money back. Someone with a similar device should be able to tell you exactly what will fit. Good luck.

You can calculate the backspace you'll need with this handy-dandy tool from Wheelsmiths-

https://thewheelsmith.net/wp-content/uploads/2021/05/Wheel-Fitment-Article.pdf

The tool Curt talks about works well too, but this is just a few minutes of your time and no $

Just a reminder not to confuse backspace with wheel offset. They're two distinctly different things.

Also, just because a wheel "fits" on your hub, doesn't mean it's ok to use it. Incorrect offset can ruin your wheel bearings and hub and be dangerous to drive.

What do you mean Otto? Backspacing and offset are the same thing, just presented relative to the centerline of the rim vs the back edge of the rim.

You have to consider both the offset/backspacing and the width of the wheel to determine where the tire will sit relative to the frame/fender.

The advantage of using the tool Curt mentioned to identify where the tire will be vs the wheelsmith calculator is that you can turn the steering with the tool and check clearances at full lock where they are the lowest.

Clarification question: Are you looking to do matched rims front/back or staggered? If you are only asking about rear rims for a staggered setup, then my comments about checking the steering are irrelevant.

The two measurements are absolutely NOT the same thing.

Backspace is the distance from the wheel mounting surface to inside edge of the rim and is in no way related to the wheel's centerline.

Offset is the distance from the centerline of the wheel to the mounting surface of that wheel.

The diagram you posted above clearly demonstrates the difference. Notice the change in position of the wheel centerline relative to the mounting surface of the rim. It's crucial that the offset be within manufacturer's specs in order for the weight of the car to be carried on the spindle/wheel bearings properly.

Let me put it another way.

Wheel offset is the more important of the two measurements. It is sometimes possible to install a wheel on a vehicle that has enough backspace such that it doesn't interfere with the steering or suspension components yet has dangerously incorrect offset.

In such a case, the weight of the vehicle will not be acting on the wheel bearings at a vector specified by the car maker. Think of the wheel (which is supporting the car's weight) as a lever acting on the bearings and spindle. Too far in or out from the car maker's specs and the bearings may fail, spindles may break, etc.