18" rear rims on a plunger?

[900triple]

Hello,

I am getting the hubs laced up on my plunger A7 and the wheel builder states that 4.00 x 18 is popular instead of the original 3.50 x 19. Anybody got any experience of this or comments to make before I commit the dosh????

[Brian]

Unless you want to go racing and want a better choice of rubber I would stay with the original 19". A 18" would alter your gearing plus upset the speedo reading. There are plenty of 19" tyres available.
If you want your bike to be original then definitely 19", on the other hand if you are building a special then I guess it doesnt really matter.

[RichardL]

As for originality, no arguement. As for speedo reading, 1/2" off the rim radius is made up with the 1/2" taller tire. The bigger issue, I think, is the width of the rim and tire. If you go to a W3 rim with a wider tire you should get more rear traction and a somewhat safer ride. That's the way I went, at least, but total originality was not an issue.

Richard L.

[900triple]

As for originality, no arguement. As for speedo reading, 1/2" off the rim radius is made up with the 1/2" taller tire. The bigger issur, I think, is the width of the rim and tire. If you go to a W3 rim with a wider tire you should get more rear traction and a somewhat safer ride. That' the way I went,atleast, but totl originality was not an issue.

Richard L.

Thanks Richard - what tyres did you fit?

[RichardL]

900triple,

My tires on W3-18 rims are Dunlop Roadmaster TT100 K81 4.25/85-18. This would calculate to 3.61" tall. The 3.50x19 as origianlly spec'd to your bike (I think) would calculate to 2.98" tall if the same width-to-height ratio is used. For my puroposes, this is close enough for speedometer readings, but others may feel differently. After all, speedo accuracy will change depending on the weight of the rider changing the effective radius.

Richard L.