From what I understand, though I dont know the numbers, the weight savings isn't supposed to be much. The front wheel is a bit shorter to improve the handling a bit and not worrying about rust is a biggie!
Well, the thread got no response in twins talk, so I thought I would see if it got more attention here. Sometimes a thread will get more response in one forum than another, that was really why I moved it, to give it more chance of getting a good answer - or an answer at any rate. :thumbsup:
The lower mass of an alloy rim is not the main advantage per se, it is the reduced polar moment of inertia that is a result of the lower rim mass that provides a significant handling and acceleration advantage. This is true on both autos and bikes, but the combined lower polar moment and reduced gyroscopic forces when rapidly changing direction (the "twisties") is particularly advantageous on bikes. Polar moment is a combination of the radius of the rim as well as mass; that 's why sport bikes have small diameter wheels.
That all said, I put polished Sun alloys on one of my T100s because they look cool - and actually increased the rear diameter to 18" :>)
I'm rolling with Thruxton wheels on my 790.
The weight saving is not very much. That lump they call a hub is where the weight is.
The bike does turn in quicker and requires less effort to do so. You will notice the difference directly. I like 'em.
Is it worth it? Mehh, it probabaly depends on what you can get them for and how cash rich you are.
I got the complete wheels, cush drive, sprocket + a front tire for $200. I didn't really have anything to loose because I could always turn around and sell them if I wanted.
If you only get the rims and them have to pay to have them built then I would say forget it. By the time you add it all up you can probably get an R1/3 front end and rear wheel for not that much more. Then you'd really have something for the money.
I'd look at all the options carefully and then deside which way to go.
"Motorcyclist" magazine reports a 7 pound weight savings by using the alloy rims from RK Excel America. In their January '09 test of a modified Scrambler Eurosports of Philadelphia, PA mounted a 3.0" x 19" front (suggested retail: $280) and 4.5" x 17" rear alloy ($300) rim, eventually paring off a total of 45 pounds from the bike. Seven pounds of unsprung weight is substantial and would make a big difference in the handling of a Bonnie. Even more of a benefit could be realized if an 18" hoop was used, as a greater selection of high performance tires would be available and steering would quicken up over the 19 incher. Yes, with spokes, nipples and installation this would be an expensive (say $1200-1500), but a noticeable difference would be forthcoming.
If you really want a noticeable change in looks or performance, IMO, you aren't going to get there just switching from the stock steel wheels to a set of aluminums that are smaller diameter. You'll get a little increase, but to get enough to make it worthwhile, I'd spend the cash and get a set of Carrozzeria's. They are forged aluminum and have a substantial weight savings, plus they allow you to go tubeless. Otherwise, I'd stay with the stockers.
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