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Tires and wheels 15 vs 16" sidewall flex

 
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davebig



Joined: 30 Jun 2015
Posts: 16
Location: Rochester MN

PostPosted: Wed Jul 29, 2015 1:17 pm    Post subject: Tires and wheels 15 vs 16" sidewall flex Reply with quote

Anyone want to offer an opinion on 15 vs 16" wheel and a little more sidewall flex on CHS rig ? I think this big old slug is more luxury sedan than road burning roadster , now that I'm getting the hang of driving it.


The 16" 50 series tires work better than I would have thought but 15" wheels are plentiful fairly reasonably (Mini-Cooper) and 175/65/15 would be about the same diameter with more sidewall. More comfortable but too flexy ?

Got 22 pounds cold in the current tires they come up about 10% when warm and ride better than I would have thought. Thanks.DB


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zentime



Joined: 22 Jan 2005
Posts: 823
Location: Massachusetts USA

PostPosted: Fri Jul 31, 2015 10:48 am    Post subject: Re: Tires and wheels 15 vs 16" sidewall flex Reply with quote

davebig wrote:
Anyone want to offer an opinion on 15 vs 16" wheel and a little more sidewall flex on CHS rig ? I think this big old slug is more luxury sedan than road burning roadster , now that I'm getting the hang of driving it.


The 16" 50 series tires work better than I would have thought but 15" wheels are plentiful fairly reasonably (Mini-Cooper) and 175/65/15 would be about the same diameter with more sidewall. More comfortable but too flexy ?

Got 22 pounds cold in the current tires they come up about 10% when warm and ride better than I would have thought. Thanks.DB



Hi Dave, When we designed the K1200 conversion, it was a deliberate decision to use the 16" wheels. If you look at the rear wheel clearance between the rim and swingarm, you'll see that the clearance is minimal. Had we used 15" wheels, we would have had to offset the wheel to the left significantly. We had seen pictures of other conversions done to that bike that did use 15" wheels and found it unacceptable, aesthetically or mechanically to have the rear wheel not in the middle of the rear fender. My recollection is that the rear wheel would be around 1" to 1 1/2" offset to the left. In addition to not looking right, you then run into issues of the tire hitting the stock muffler. Using 15" wheels would have given us many more choices in tires and wheels but in the end, we made the decision that we fell made the most sense aesthetically and mechanically. Obviously, the rear wheel drove the decision to use the same wheel on the front and sidecar.

Getting back to your original questions. I don't think 15" or 16" wheels in of themselves matter, it's the tires that matter. For me personally, 55 series tires are the "sweet spot" though I have no issue with 50 series tires. Again, speaking for myself, I'd find 65 series tires inhibiting to my style of driving. The lower air pressure we use that makes these type of sidecars work well, would not be to my liking in a 65 series tire. There would be more sidewall flex that I would like. Putting more pressure in a 65 series tire to reduce sidewall flex would in my mind be counterproductive. The ride would become harsher with more pressure and the grip would decrease.
Hope that helps asnswer your questions.
Bill B
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davebig



Joined: 30 Jun 2015
Posts: 16
Location: Rochester MN

PostPosted: Fri Jul 31, 2015 11:21 am    Post subject: Reply with quote

Thanks Bill, that was a concise answer , the adv guys chide me for running 65 series tires there (to short to harsh) .
When I picked it up the previous owner could not tell me much about it, I thought the 22 pound in tires was natural leakage, ran them up to 32 (ouch) I asked the other BIll some questions he filled in the tire pres for me everything became much better.
Now that I'm learning to not drive or maybe not oversteer it things are going much better and it's still a sidecar steers with throttle.
You guys do or did pretty nice work ! Thanks for the help.DB
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davebig



Joined: 30 Jun 2015
Posts: 16
Location: Rochester MN

PostPosted: Sat Aug 01, 2015 12:46 am    Post subject: Reply with quote


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