trying to put a 150 rear tire on my 2004 roadking classic has a stock 140 on it Wiil it fit!!
Dealership says have to change swingarm!!

 

Just measure all of your clearances. Measure from the widest part of the tire to your swingarm, belt and guard. You are only going ~5mm wider on each side. You need to also check the manufacturer specs of the tire you have and what you are going to use. Dunlop has 150 tires that range from 5.9-6.25". Check what your 140 measures as well. I'm not 100% familiar with the Roadking, but this is what I did for my Dyna. I'm going from a 5.9" wide 150 to a 6.6" wide 160. The tightest spot for me was between the fender bolts. I reversed them to use saddlebags and am using cap head bolts. My next tightest spot is to my belt. I have about 5/8" now and will have about 3/10" with the New tire. Don't always believe the dealer. They're in the market to sell you new parts. A lot of the newer Dyna guys run 180 and wider. According to the dealer you would need a wide tire kit.

 

Check th specs but IIRC, the OEM rear tire for the '04 FLHR is 150/85 x 16, so the right 150 shoud fit.

 

If you have the later narrow belt, it should fit with room to spare. If you have the older wide belt, you will find it is a squeeze and may not work. I couldn't with my bike and went to a narrow belt (with later swingarm and wheel!), but I have read of some on HDF who have managed it.

Unfortunately tyre makers only make their tyres to nominal sizes. As an example, the Avon Venom 150/80 is available in H and V speed ratings, but the V is actually a little wider! My H rated tyre measured 3mm wider than they say it should be, so there is variation on these things.

 

i have run a 150 meztler for years only had to trim clearance for belt guard. have 1/4 clearance on belt, no other issues, good luck