I have a 1992 Softtail Springer that I am modding and I need help determining wheel size and tire size.

I am removing the rear fender and am putting a chain conversion kit on it and open primary. I am also removing the front fender. I am shortening the springer 1.5"
This bike will be a tracker style bike.

I am wanting to put an 18 on the rear. Stock is 130/90-16
I am wanting to put either and 18 or 21 on the front. Stock is 80/90-21.

The wheels I am purchasing are either 21x2.15 or 21x3.5, and 18x3.5. I just can't figure out what I can get away with. Please help

 

Well the widest tire for the 21x2.15 would be 90/90-21. You could use a 120/70-21 or 130/60-21 on the 3.5. For the rear 18x3.5, you could use a 150/70-18 depending if you have clearance for the fender and that old 1.5" wide belt

 

I am contemplating if I can do a 21 that is 3.5" in diameter up front. And I'm doing a chain conversion and doing away with the stock fender. Thoughts?

 

Having No fenders and a chain drive should help with clearances

I would check with the Tire manufacturers for their particular tire width, but using Nominal sizing... can you fit a 120mm (4.72") or 130mm (5.12"), and 150mm (5.91") is their respective areas?