Can ST225/75R15 Trailer Tires be Replaced with ST235/85R16 Trailer Tires

Question:

Can ST225/75R15 load Range E tires be replaced with ST235/85R16 load Range F tires on a 2001 31ft Forest River Wildcat dual axle. We know we would have to get new rims if they can.

asked by: Denise

Expert Reply:

The tires that you have now, ST225/75R15, are 28.4 inches tall and 8 inches wide. The larger ST235/85R16 are 31.6 inches tall and 9.25 inches wide.

You would need enough space all around the existing tires to use the larger size. Only half of the difference is applied towards the trailer from the sidewall and above the tire tread to a fender or trailer body. That means that you would need more than 1.6 inches above the tread and more than 0.625 inches between the sidewalls and the trailer frame in order to use a larger size. You also have to account for suspension travel which can be around an inch vertically.

If you determine you have the space then you can switch to the larger size. For an ST235/85-16 load range F already mounted on a wheel we have # AM35099. The wheel has an 8 on 6-1/2 bolt pattern. If you need a 6 on 5-1/2 bolt pattern then you can use tire # AM10501 and a wheel such as # AM20741. A local tire shop can mount the tires to the wheels for a nominal fee. Please note that going to higher capacity tires does not increase the capacity of the trailer which will remain the same.

expert reply by: Michael H