What's the Widest rear tire that will fit on a stock 1995 Road King, without getting into serious mods? I've got a Dunlop MT90B16 on there now. That 90 seems kind of narrow, although I know it's the recommended size. Would be nice to have a little more rubber on the road.

 

are the best I've found after running Dunlops, Avons, etc. That "90" should refer to the tire height ( ratio of tire height to width or 90% of width). Stock size for rear tire on my '91 FLHS is 130/90/16 ( 130 mm wide/90% of width high/16" wheel). I have size M/U 85 Metzler Marathons on the rear now which is close to a 140/90/16 and my final drive belt just grazes the sidewall by a couple of thousands of an inch; nothing to sweat. Some might say that's a big deal but I've got about 10k miles on it like that with no problems.

Stock size on the front of our bikes is also 130mm/90/16 btw in the Metzler Marathon also. They are sweet tires and you feel the difference as soon as you turn onto the road with new ones.

 

I ran an Avon 140/90, which is a similar width to your stock tyre. Frankly there is not much room in there! I had to remove the rubber curtain on my belt guard to get it in on my 1990 FLHS.

I now have a 2007 swingarm and later wheel, with narrow belt. A 150/80 Avon fits in with ease, but I couldn't get it in with my stock wide belt. It is very snug in my rear fender, although belt clearance is better than with the 140/90 (because of the narrower belt).

The critical thing, as Tactical111 mentioned, is clearance of your tyre to your belt. Measure that, take off a little for running clearance, then double it and add it to your current tyre width. That is as big as you can go!

If you fit a narrow belt you can probably get in a 160. I believe your later bike has a wider fender than my bike, which will accept it.

 

Good point on the 90,Tactical. I looked at the Dunlop website and my tire is 5.2 inches wide or 132 mm. There's an MU85B16 Dunlop rear tire that is 5.5 inches wide or 140 mm wide. Wonder if that will fit like your Metzler M/U 85 does....? I've got a new Dunlop on the front, so I've got to go with a Dunlop on the rear, otherwise I'd take a look at the Metzler.

 

That's a good thought about the narrower belt, GRbrown. I hadn't considered that possibility. What's the tradeoff on going with a narrower belt? Seems like it might be more likely to break...? Have you had any issues running the narrower belt?

 

I don't believe there is any trade-off. I used a stock Harley belt fitted on the later stock touring bikes. Harley used to make a reinforced wide belt for sidecar use, but they don't make a reinforced narrow one for their trikes or sidecars, so I assume they are much stronger now. We have toured from our home in the UK to Poland and back with it, fully loaded at around 1200 pounds ready to roll! My gps tells us we cleared 95 mph on a German autobahn! I also have an S&S 107 up front with over 100 HP/TQ.

With my later wheel the narrow pulley is set a little further away from the tyre, which gives a bit of extra clearance. The front pulley is much wider than the rear and doesn't need any change, although obviously the primary has to come off to fit the new belt.

Hope that helps!

 

Stock is a 130/90 Dunlop .I used to run a Metzeler ME880 Marathon 140-90 rear tire, and there were no clearance issues at all back there. I recently switched to wire wheels, and installed a H-D Dunlop 140/90, and it rubbed so much I couldn't even turn the rear wheel. So I removed the belt guard, and now it rubs just a tiny little bit on the belt - maybe 1/64". It's rubbed a bit from the left side of the tire, but it's not enough to bother to do anything about...

SO, a "140" isn't always the same width across tire manufacturers. The Dunlop 140 is about 1/2" WIDER than the Metzeler 140! Kind of like clothing sizes from different manufacturers, I guess. Make me wonder how a Metzeler 150 would fit...

 

Avon makes a "140" that fits and also has a "142" that fits but is close. You can put a 150 Avon on it if you put a .060" spacer under the drive pulley. Hope this helps!!

 

150 Avon on mine after centering the wheel (1/4"), 1/4" sprocket spacer and the caliper bracket needed cut down a little to space the wheel to the right. Still have the big belt, used a Harley side car belt.
That MU85 is pain free and a easier task then that what I went through.

 

All good data and advise. The ME 880 Marathon Metzler M/U 85 went on my '91 FLHS rearend with no modifications/spacers and works fine. As far as the oversized Dunlops, etc. I guess you'd just have to have exact measurements to make sure they fit. Good luck with it!