Boxerworks.com

1985 R80, now has a Dunlop 491 Elite 2 100/90 56H on the front and an Avon Roadrunner AM21 120/90 H18 on the rear. Both have good tread but the Dunlop has been plugged and must be replaced. What to the wise ones on this site recommend. Thanks

I think those are stock sizes.
That is what my R100 (1987) had.
I like stock sizes. Mine worked well.

Check this page...down near the bottom...it specifies the tire dimensions you should be using.

http://www.bmbikes.co.uk/specpages/R80mono.htm

The 100/90 is probably too big for the front...it might fit, but it doesn't help with handling. 18" tires front and rear.

Kurt in S.A.

If you have trouble finding 90/90's in the tires you want, I can understand going to a 100/90 for tire selection. Otherwise, as above: stick with the stock size.

Oops! My mistake.
90/90 is stock.
I used Bridgestone BT45's and liked them.

"Proper" is a relative term.
One might define that "as recd by the factory"
and be done with it
or understand that "better handling"
is one of those generic buzz words
bandied about without the understanding
that the term has absolutely NO meaning
without (a specific) context.
A 100/90 could very well be a better choice for an 85 R80.

vanzen wrote: A 100/90 could very well be a better choice for an 85 R80.

Per tickly with a 120 rear.

Major Softie wrote:If you have trouble finding 90/90's in the tires you want, I can understand going to a 100/90 for tire selection. Otherwise, as above: stick with the stock size.

When I purchased my bike (1988 R100 RT), it had 100/90 front tire. I've replaced it with the same size since that's the way I'm used to the bike handling. It's a bit tough getting the tire past some of the bolts/nuts that hold on the fender, but not too difficult. I have no idea how a 90/90 would be on the bike. Perhaps I should give the stock size a try next time I replace the front tire. FYI, the rear tire is stock size.

Yeah, the 90/90 will probably make fitment a lot easier, but actual mounted and inflated width varies at least as much between manufacturer and model as it does between sizes.