Tire Fitment

I have a completely stock Rebel 250 of 1987 vintage that specifies a
130/90/15 rear tire. I have the opportunity to buy a new 140/90/15 tire at a
very good price. Since I don't understand the numbering system for tires, I
have no idea if this tire would hit the frame/fender or cause other problems
I may not be aware of. Advice in this matter would be greatly appreciated.
Thanks in advance for any help in this matter.

Tom

 

The first number is the tread width in mm. The second number is the ratio of the
sidewall height to tread width. The last number is of course the rim diameter
in inches.

Your new tire will be roughly 5mm wider on each side than your present tire.
Different manufacturers tires will vary slightly in width even though both will
have identical numbers. Measure the clearance you have now. If it's greater
than 5mm on each side, go for it with caution. See below.

Remember that the sidewall height is also a little greater on the new tire, so
check the radial clearance also. I once went from a 130 width to 150 width and
it didn't rub on the sides, but the clearance between the center of the tread
and the pivot point of the swingarm was pretty close. At highway speed the
diameter of the tire grew and the swingarm tore large chunks from the center of
the tread, ruining the tire.

 

Jack,

Thanks for the education on tire sizing and the benefit of your experience.
Hope I can return the favor someday!!

Tom

 

Lots of riders ask about changing sprockets to get more fuel economy
by running the engine at lower RPM, but they rarely ask about changing
the rear tire diameter to get the same effect.

1 millimeter = 0.0394 inches.

The larger diameter 140mm tire will stand 24.93 inches tall, the
smaller diameter 130mm tire stands 24.22 inches tall.

The extra height of 0.355 inches would be noticeable in the steering,
since raising the rear of the bike as the same effect as lowering the
front.

And, the larger tire has a rolling circumference of about 3% larger
and that would reduce engine RPM by 3%.

Just for the sake of illustration, that's like installing a rear
sprocket with about 1.5 teeth less.

Don't fret, a sprocket with 1.5 teeth less has never been made...