hey guys I got my excel rear rim in awhile back it's a 2.50x18. I'm going to try to have the tire mounted tomorrow. I got a Duro 140/70/18 and this thing looks a lot wider than the rim like it should be on a 3.50" rim not a 2.50" rim. I know Dave got a 130/70/18 on his excel rim. I figured 10mm more would work but that tire is a lot wider than the new rim. I couldn't get it all the way on just on one side. what is the stock ls650 rear rim width? First time mounting a rear tire maybe it will work I'll find out at the shop tomorrow.

Yep, it seems the RYCA conversions and all those who follow their examples are installing "too wide' tires on the rims.  I did get a 130/70-18 tire on my 2.50x18 rim just like all the other lemmings.....and after 2 years of riding on the bike I realize that is not the best way to go.

Here are links to several tires charts, and all of them confirm that a 110 tire should me mounted on a 2.50 rim, a 130 tire should be mounted on a 3.50 rim, and a 140 tire should be mounted on a 4.00 rim.  (There is some variation that goes with the aspect ratio and the 140 tire can be mounted on a 3.50 - 4.50 wide rim).  The tire carcass is molded to fit on the rims that match the tire width, and if you measure the distance between the tire beads on the unmounted tire....it is a good indication of what width rim it should fit.

http://www.mtsac.edu/~cliff/storage/gs/Motorcycle_Rim_Width_Tire_Size_Chart.pdf

http://www.bridgestone.com/products/motorcycle_tires/products/battlax/bt45.html

If you managed to squeeze the 140 tire onto the 2.50 rim - you have pulled the sidewalls in and it will do 2 things.  1)  Modern tires are built with a profile that has a small amount of tread touching the road in the center of the tread - and the tread pattern is formed in an oval pattern that places a lot of rubber in contact with the road when the bike is leaned over.  Squeezing the tire distorts this profile and makes the tread too round in cross section and the tire has less rubber touching the road.  2)  Squeezing the tire together results in tread being rolled over on the sidewall where is never can be used, and it makes the tire too narrow.  My 130 tire on a 2.50 rim was only 116mm wide.

I wore the center of my Pirelli Sport Demon tire out in 4,000 miles, and the edges look fine.  The center of the tread was too arched and I was running on a tire that was not allowed to flex and move as it as designed - the narrow rim restrained the tire too much and did not allow it to work properly.

I now have a 110/80 tire mounted on my 2.50 rim.  It looks a bit narrow if you are used to seeing sport bikes - but is fine if you are used to looking at Cafe'bikes and vintage motorcycles. The 110 tire mounted o the 2.50 rim is only 6mm narrower than the 130 tire was mounted on the same 2.50 rim - because the 110 tire is made to fit that rim while the 130 tires was made to fit a 3.50 rim (so that pulls the beads in a full 25.4 mm farther than they are supposed to be).  Last night I saw a 1960's Moto Guzzi 750.....and the rear tires was a 110/90-18.  A 110 tire is plenty wide to handle the weight and horsepower of our bike.

My new approach to this is:

The front 100/90 tire is fine on a 2.15 rim - even though it was really made to fit a 2.50 rim.  It works OK.

The rear tire should either be a 110/80-18 on a 2.50x18 rim - or you should install a 3.50x18 rim if you want to run a 130 or 140 tire.

If you squeeze a wide tire on a too narrow rim - you are not going to benefit from all the high tech rubber and profile built into the tire.  The folks design these tires really do know what they are talking about, and we should follow their recommendations.  We are also not the only folks having this discussion.  I was looking for tire recommendations for my Ninja 250 that I just bought - and all the young fellows want to throw a wide tire on the back of their little bikes....and the recommendations are that the best performance will come from the tires made to fit correctly on the rim.

Dave

Some reading I have been doing about this common issue:

http://faq.ninja250.org/wiki/Do_taller/wider_tires_work_better_than_the_stock...

http://blog.jpcycles.com/2010/10/what-is-the-skinny-on-fat-tires/


   

Yeah thanks Dave I got it mounted and is exactly as you described the tire is stretched and rolled in too far on the narrow rim. But I did get it mounted and the center is raised more so I'm figuring the tread will wear in the center faster. But when I got the tire (a Duro 140/70/18) It didn't look like most unmounted  tires I've seen that were already round in the center. Mine looked like a low profile car tire. Flat as can be across the center. IDK as long as it's safe it will work for one riding season I guess. Now I see how the 140 needs at least a 3.00" rim but don't understand with the savage having a 2.75" stock rim width. It calls for a 140/80 tire and it seems to fit fine. Is it the sidewall being a 80 that you can roll it into the rim further thereby squeezing it onto the small 2.75" rim? Pretty much doing the same thing there staying stock 140/80/15 on a 2.75" wide rim as I'm doing with the 140/70/18 on a 2.50" excel rim. Squeezing the nuts out the tire.

I think the reason the 140/80-15 tire fits a 2.75 rim, is that it is a "cruiser" size tire and is made differently than a "sport" or "touring" tire.  The tire folks make 15" tire wide and fat......for cruisers.  They are wider and flexier than a sport bike tire.

Here is a chart that shows the size rims for a big range of rim diameters, and it shows a 140/90-15 tire on a 2.75 rim is at the bottom of the recommended fitment...it would be better on a 3.00 or 3.50 rim.
http://www.dropbears.com/u/utilities/tyrerim.htm

Yep, no problem running your 140 tire for a season....I ran the 130 for 4,000 miles and it did wear the center flat.  The sad thing is that my 110 tire is only 6mm narrower on the 2.50 rim than the 130 tire.  Since the 110 tire is made to fit a 2.5 rim the full 110mm measurement is there....the 130 tire beads are squeezed in a full inch, and the result is the 130 tire width was only 116mm when mounted.

I got another hub and I am going to mount my 130/70-18 Battlax on a 3.50 rim....and then I can compare the handling of the 110 vs. 130 tires when mounted on the correct rims.

Dave