Mounting 70R and 80R on rear

[wmmaryyoung]

I am getting new to me a 2003 dutch star. It has new Michelin on the front 275 70R 22.5 but the original on the rear. I plan on getting 4 new tires and some threads recommend going to 80R vs 70R. I am not sure what is the difference. My plan was to put the now front 70R on the inside rear and the new tires on the outside rear and front. Should I go to the 80R tire on the rear matched with the 70R? Is it OK to go to a 80R vs a 70R? I guess one could ask why bother? One possibility is to match the 70R on the rear and put 80R on the front. But again is there anything to gain? Any thoughts would be appreciated.. Bill Young

[Theberrys]

Bill

Here is a link to a tire size calculator. You won't be able to do a 22.5 but you can do a 22 to see what the 70r and 80r sizes are. I wouldn't mix the sizes on the rear tires you'll loose weight capacity. Actually I'd just match the two you are gonna keep.
Tire size calculator

Dick

[Norm4015]

All tires on an axle MUST BE the same size. If you mix and match tires on the same axle you are asking for major problems - blowouts down the road. There is no problem running different size tires on the front and back. I did that on my 2000 DSDP and Spartan said it was OK and I had no problems.

[tmitchell]

The reason most owners, including myself, switch from the 70 to 80 series tires is for a better ride. Putting 80s on the front is where you will improve the ride comfort the most.
Since your front tires are new 70 series, I would buy 2 more 70 series and put them on one side in the rear and bring your already installed new 70 series from the front and put them on the other side in the rear. Then also buy a 2 new 275/80R22.5 tires for the front. This way you only need to buy 4 tires.
I went with Michelin XZA3 LRH 275/80R22.5 all around on my 2004 DSDP.
Tom