Can someone tell me the size of the widest 19 inch tire that will fit on a 1973 stock 850 commando? Thanks in advance!

I've got a 90/100 on mine. That works really nicely. If you put a wider tire on, you'll just screw up the tip in. It pinches the profile.

I would not go bigger on the rear than 4.10 x 19. (and there ain't much room between the insides of the swing arm and chainguard) I still prefer the Dunlop K81 TT100. I use a K81 GP 3.90 x 19 on the front as its a stickier compound. The stock 4.10 front I found a bit heavy on the steering. Basic rule is stay with the same combination front and rear such as the Avon AM26 products. If you mix different types you can risk upsetting the handling.

Mick

Welcome to the forum!

pbmw has it right, the stock WM-2 rims on the Norton won't take advantage of wide tires.

Remember that it's not how much you can fit in there, it's about how much you can keep in contact with the road. Those skinny 1.85" rims will turn too much of a wide tire tread into sidewall, that you can't use at any remotely sane lean angles. If you absolutely, positively, have to have a fatter tire, get a wider rim first.

Do a search for tyre / tire sizes, and another for 'rim sizes' , lots of good information that could keep you here most of the night.

I've been running 130/90-18's (roughly 5.10 inch) on WM3 rims for about twenty years. There's enough room for the chain and swingarm (you might have to notch the chainguard)--and you need to keep things straight. The tires are about 7-8% taller than TT100's and last forever--one Cheng Shin with minimal grooves went over twenty thousand miles. The big tire absorbs all the Isolastic vibrato with aplomb--rated for 700 lbs or so--and gently stops the bike: I rarely use the front disc around town.

My rear TT100 would have visible wear after every summer afternoon outing when I was going through a tank of gas a day--and a tire every other month. I keep a 19-inch TT100 back tire for quick changes when I get a flat on the road (the big tires need inflating after you squeeze them past the paddles). No doubt the handling is diminished somewhat--the back end feels a little nervous with the smaller tire--but I find myself swapping the bigger tire back within a day or two.


Tim Kraakevik
kraakevik@voyager.net

I tried an avon 120 on my 18" rim, this made it impossible to get a proper wheel alignment, I now use an avon 110, it is only a few mm of the chain guard but does allow a good wheel aligment.

I had (by previous owner) a 120/18 on the rear and a 100/18 on the front. As noted above, I couldn't really get the rear to align properly without rubbing so it was never properly aligned though a lot of miles was put on it with no obvious problems as far as handling was concerned. Recently , as part of my conversion from Roadster to Fastback, I removed the 18" wheels and put new oem 19" wheels/Avon 4.10x19 tires back on the bike. I much prefer them though I'm sure the rear will wear out relatively rapidly compared to that 120x18.

One thing I've noticed about tires is that one mfg 160 tire may well be narrower than another. I use a lot of 160/17's on my motard. Pirrelli's are narrower than just about everything else. I have a suspicion this is true in the smaller sizes also.
But I still wouldn't go any larger than a 100/90 on the rear. I like the faster handleing of the smaler tire.

MexicoMike wrote:I had (by previous owner) a 120/18 on the rear and a 100/18 on the front. As noted above, I couldn't really get the rear to align properly without rubbing so it was never properly aligned though a lot of miles was put on it with no obvious problems as far as handling was concerned. Recently , as part of my conversion from Roadster to Fastback, I removed the 18" wheels and put new oem 19" wheels/Avon 4.10x19 tires back on the bike. I much prefer them though I'm sure the rear will wear out relatively rapidly compared to that 120x18.

mike
If you like the switch to 19s' and K81s' next time try the Avon AM26's in 100/90 rear and 90/90 front. much better handling tyre does not track grooves like the K81s' and out lasts them by a little plus the smaller front quickens up the steering even more