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Fatter rear tire for '99 1100RT?


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Did the search but no joy. Can I put a fatter tire on the 18" rear wheel? What size max?


Why are others considering a 17" rear wheel swap, not that I'm likely to do it.





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The 17" rear tire sizes are more common than 18". If you have a rear tire problem while traveling, you can get a new tire at most any brand cycle dealership. You almost need a BMW dealer to get an 18" rear and hope they have one in stock. I've run a dozen 170/60/18's on my RT's without any problems. Mainly because they were more readily available when I needed them.

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Going to 170 but maintaining the same aspect ratio, according to my algebra (questionable), indicates a 6cm taller wheel/tire combo. I think the rear's too tall already. True?

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No, I think that would be a bad idea. Separate from the rear height issue, a wider rear tire might contact the swingarm unless you added another (perhas plural?) rear wheel shim(s) which would create even worse PTTR. Stick with stock and remove the wheel shim to reduce PTTR.

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Yes, the 170 will give an "inseam challenged" rider more of a problem. NEVER had a 170/60/18 touch the swingarm, loaded up or empty. I used both Pirelli and Dunlops 170's.




170/60/18 Dunlop GP pic.


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There is much more to this than just the height difference. There is also wheel width to consider. As I recall, the 18" rim was only 4.5" width. A 170 tire on a 4.5" rim is going to assume a very bad profile. Too much sidewall angle and too flat a curve in the tread area. The handling of your motorcycle will be adversely effected by such a combination.


Best to leave the 170 section tire to the guys with 5" or 5.5" rims. You could always send your wheel to Sandy Kosman (Kosman Specialties) and have him widen it for a couple of hundred dead presidents. In all, the 5 x 17 rim from a K1200RS would probably be a better deal and will easily accommodate the 170 section tire.

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There is no tire profile problem. Handling is no problem. I have easily average over 10,000 miles per tire. Attached pic of Metzler tire fitment book page showing 4.5 rim acceptable for a 170/60/18 tire.


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No Problem. Have had a 17" x 5" rear rim on my R1100RT for 30K plus miles. NO PROBLEM. Rim came off a K1200LT. Bolts right up to rear end. No additional spacers. Now I can run all the 17" tires out there. I like the Metzler ME-880 best. Never got over 5K on rear with 18" rim. Now getting almost 10K on rear tire. I will never go back. Enough Said! clap.gifthumbsup.gif

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