I am looking at putting duals on my 4450 jd FWA. The tractor has 20.8x38 tires. I found a set of duals with 18.4x38 tires. Both the tractor tires and the duals have Michelin tires. I know the 20.8's are wider than the 18.4's but are they taller as well or would they both be the same height? There will be alot of weight on the duals so they would have to be the same height, the width would not be a problem. Any advise would be appreciated!! TIA!