I’m not certain if this has been shared before, and I’m also sure I’m not the first person to think of this but it came to mind so I thought I would share.

I found an easy way to almost completely accurately figure out what size of wheel and tire combo will fit in the rear. This is very helpful if you are trying to go as big as possible too.

What you will need:
A straightedge. Preferably one with measurements on it. If not, one that you can mark on.
Another ruler or tape measure.
Jack and jack stands.
Wheel chocks.

Note* For this example, I am going to use my vehicles measurements as well as the wheel and tire size I am going with. My vehicles measurements are not going to be the same as yours. I have a wider, 4th gen rear end and have done some cutting and hammering to the rear wells to allow for more room. Also, if your car is lowered and you do not have an adjustable panhard bar installed, your measurements will not be the same because the rear differential will be kicked out slightly more to the driver side. The differential must be centered to the vehicle at ride height.

Step 1: Chock the front wheels.

Step 2: Loosen the rear lug nuts.

Step 3: Jack up the rear by the pumpkin just until the wheels are about an inch or two off the ground.

Step 4: Place the jackstands under the axles near the ends, close to under the springs, and lower the jack. The tires should just be off the ground. This ensures that the suspension is loaded and the vehicle is pretty much at ride height.

Step 5: Remove the tires.

Step6. Place the ruler or markable straightedge flush against the mounting surface of the rear hub. Here, you need to know the measurement of the outside diameter of the tire you are going with. Mine is 27.2”. Half of that is 13.6” so put you marks with one mark at the center of the hub and the other 13.6” out. That is the absolute outside of the tire. The widest part of the tire will be the center of the sidewall so it is best to know that measurement as well. Mine is at approximately 26&1/2” so the ideal place to mark would be 13.25”.

Step 7: Use the other ruler and place it at the outside mark you wish to use and slide the ruler back until it hits the wheel well. Ensure it is at a 90 degree angle. This is how much room you have until something hits. Don’t just do this measurement in one spot. Turn the hub and take the measurements on every spot in the wheel well. Some spots are deeper than others. Your max clearance is your shortest measurement.

Now you don’t want anything hitting so deduct an inch or so to give room for suspension travel or hard cornering. Mine is a 305 or 12” wide tire with a wheel that is 11” wide and has 7.6” of backspace. So the tire will go out an additional half inch or so. My lowest point is 8” so this is cutting it very close. I will have to do a little work to get that spot wider but everywhere else clears with about ¾” to 1” to spare.

Do the same thing on the other side and get those measurements. They should be close to the same but both wells are slightly different. You can also use this to see where you can remove a little bit of excess without a tub or mini tub.

Also, use this website… www.rimsntires.com/specspro.jsp It has been such a huge help to figure all of this out!

And there is a much less accurate measurement to see how much clearance you have from the hub to the quarter panel wheel well lip. Place a tape measure against the hub and stand directly over it. Pretty basic but also not exact. Or you can do the same process as above but do it in the other direction. I did not try that so I can’t give my 2 cents.

Again, I just thought this up and put it out there. I’m sure this is something that has been done before but I thought I’d share.

And that’s it! If there’s anything I left out, please feel free to chime in. Comments are always welcome but let’s keep it friendly. We are all here to help each other.

P.S. I just posted this and saw that the pics are upside down. Sorry, I don't know what happened and I'm not sure how to fix it...

 

lets see if this does it

Guess not. Sorry.

 

Been touting this idea for years and its amazing how many people can't figure out how to use a tape measure....