Rear tire size

[AlfromNH]

I'm about to order a set of Bridgestone BT45's. 90/90-18 for the front and 110/90-18 for the rear. Sound right? Will that rear tire fit in the swingarm without a hassle?

[Bob_Roller]

The OEM rear tire size is 4.00x18 .

Different width tires will work, but it depends on the make and model of tire .

I know a Metzeler Lazertec 120 tire will work, but it is a pain to get on and off of the bike .

[nhmaf]

I run a 110x90 BT45 rear tire on my 82 R65LS and it fits nicely - adequate swingarm clearance and I can get the rear wheel off without deflating the tire first (though you'll still need to have the centerstand up on some boards or something to get a bit more clearance under/around the fender.... and loosening up the left side saddlebag mount if you have them.

I love the BT45s on this bike - it handles nicely and sticks well in rain and dry and doesn't try to follow every little crack or groove in the road on  scarified pavement.   The bike is light enough that even with the fairly sticky-ish rubber I still get ~7K miles out of a rear tire.

[Barry]

I collected some data on tire widths and the actual mounted width of 110 BT45's seem to be very close to 110 mm so no problem. Clearance is an issue when mounted width gets to 120mm or above. According to the manufacturers data the 4.00 BT45 is at least 7mm wider than the 110 so oddly clearance would be less with the correct size tire.

Only one other consideration. A BT45 110/90 is 20mm smaller in diameter (approx. 2.9%) than a BT45 4.00 tire so there will be a modest effect on gearing, speedo/tripmeter accuracy, ride height, centre stand function etc.  Of course any noticeable change will depend on what you have fitted now.

[AlfromNH]

Thanks for the input, guys. NHMAF: I decided on this tire largely on your review after searching this forum. Seems like a good tire for the price.

The tire that was on there was a 4.50-18. I don't know how the PO got it on there, I wound up taking the final drive off to get the wheel off. I'm sure there was another way, but the fd was coming off anyway.

[Barry]

The tire that was on there was a 4.50-18. I don't know how the PO got it on there, I wound up taking the final drive off to get the wheel off. I'm sure there was another way, but the fd was coming off anyway.  

Seems likely that to fit a 4.50 tire the 10.7mm top hat spacer will have been fitted which in moving the wheel over to the left also reduces spline engagement by 1.5mm.  You might want to measure yours and consider going back to the stock 9.2mm item.

[AlfromNH]

I hadn't considered any such thing, Barry. Thanks for the heads up. Cleaning and repacking the bearings is on my to do list, so I'll make note to check the spacers at that time.