Can you go down a size on motorcycle tyres?

will 110/80-18 fit on my xt125r which is 120/80-18?

I went up a size on the rear on my very first bike the cbr125 mmmmmmmmm............

[TSM]

depends if the tyre you want is specified for the rim width
more likley going from 120/80 to 110/85 to keep the total wheel height roughly same

[the_lone_wolf]

Probably

I'm running a 140 Dunlop Rally Raid on the back of mine as it's the only size they make, think the recommended fit is a 160

Just make sure the rim isn't too wide and you'll be OK, see if someone else has one it first...

My Sv had a 110 fitted to the front instead of a 120 when i bought it, only realised when another orger pointed it out on a rideout. Changed back to a 120 when i got a new set and haven't really noticed a difference

[MrMessy]

I ran a 150 section on the rear of the SV for awhile with no problems. Also checked with Bridgestone and a 140 section will fit an SV rear rim. Depends how far you lean over.

[Biker Biggles]

Are there any issues with insurance if you run non standard size tyres?I could just see them using that to wriggle out of paying if they noticed.

Originally Posted by ian505050

will 110/80-18 fit on my xt125r which is 120/80-18?

I went up a size on the rear on my very first bike the cbr125 mmmmmmmmm............

Yep, no worries on dirt bikes. A 2.15" width rear rim which is pretty much standard for the industry will carry tyres from 100 through to some 140s. 80 and 90 series tyres in this range are not overly sensitive to rim width. If they are road tyres (not knobs) on a bike like this up or down one size is safe.
I'd have thought a 100 or 110 would have been more appropriate for something like an XT125 anyway and have a hard time seeing a 120 as a standard fit.

It is when you get into low profile road rubber that you need to be cautious.