Wheel and Tire Tech 101 - Cuttin’ Corners

Tire Diameter

Determining how big your tire will be.

To calculate the overall tire diameter you only need the size of the tire. The following formula will help you determine the tire diameter and give you a good idea as to whether or not that new rim and tire combo you want will fit. Just compare the overall diameter (of the desired tire) in inches to your stock tire and this will allow you to measure up your vehicle to see if it will fit with or without modifications. You must also take into consideration the width of the tire you are proposing to put on, just because the OD matches doesn’t mean the width won’t put a damper on your newfound fitment. Please note that all oversized fitments should be left to a professional they can tell you what – if any – modifications need to be performed.

For example, if the tire size is 225/50R 16 the equation will be implemented as follows:
When upsizing rims on a vehicle it is also important to consider the following:
Be sure that there is no contact with the tire and the inner fender liner

FIX: You can always heat up the fender liner and remold it or in some instances you may have to remove the fender liner. Please note that removing the fender liner may cause excessive road noise from debris bouncing off bare metal and that valuable electronics may now be exposed. Inspect carefully!

Be sure there is not contact on any control arms, spring perch, or any other obstructions that may be there.

FIX: Many shops will trim metal brackets to avoid any minor scraping. This should be left to an expert and be advised that damage to the body or paint may occur if not done properly.

Be sure that the case nut under the spring perch does not touch the top or inner sidewall of the tire. As the tires heat up they will expand so keep that in mind.

FIX: Run a slightly smaller tire. In some cases the nut is shaved down slightly to add extra clearance. Please note that we do not recommend this but are just educating you on what is sometimes done. If you choose to do this make sure that it is left to a professional as shaving too much of this bolt may have detrimental consequences.

Be sure that the inner lips on your fender don’t contact any part of the tire while driving straight, during compression or hard cornering.

FIX: You can have the fenders either rolled or cut. If you do roll fenders be sure to have an expert do it to prevent paint chipping of unevenly (and ragged) fenders. When cutting fenders be sure to sand down the cut edges to ensure that they are smooth. When done you should apply a coat of rust-proofing or paint to seal the open area.

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