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Does anyone know if the standard 16" rim for the rear can be replaced with a 17" rim. I would like to increase the size of the rear tire in order to get a better road speed at a lower RPM.
Thank you for your input.
Yes but you will need the wheel spacers and the caliper stop bracket that goes with the 17" rear wheel. The 16" wheel has the disk further out to keep the caliper off the rim and one of the spacers is part of the steel caliper stop bracket.
yes you can.i have 1978 E and its got a 17" rear wheel.they came with that size.the newer models went to a 16". i got 140/80 17 tire on there no prob. mosts owners have a 130 on the back. you can"t go too wide cos it rubs on the drive shaft housing. take easy
1978e. special forks.she's a frankinstien.a bit of this a bit of that.its a monster
Russ79 did this as well. I think he got almost the same results as the final drive swap. It also gave him a little more clearance. It wasn't really an option for me as I still want to be able to touch the ground with both feet (lol, short legs), so I went with the final drive swap.
Harry
The voices in my head are giving me the silent treatment.
Once again...it is not the diameter of the wheel, it is the circumference of the tire that matters. Changing to a 17 inch rear rim will not get you much difference in RPM vs speed.
For example, take a Dunlop Elite 3 in a 16 inch size. Diameter is 25.7 inches. Compare that to a Dunlopp GT501 in a 17 inch size. Diameter is 25.6 inches. Yep, the 17 incher is smaller than the 16 incher. You would actually run a few RPMs more at a given speed with the 501 17-inch tire than you would with the Elite 3 16-incher.
It is true that you have more choices in a 17 inch tire, but even there you are limited by the XS swing arm to a fairly narrow tire by today's standards. Also, most - not all - of the 17 inch rims were tube-type and not tubeless. (There have been threads about using tubless tires on tube-type rims, I am not in favor of it due to differences in rim design.)
Moral: the 17 inch conversion may not get you what you want, depending on the tire you put on it, and may be more of a hasle than it is worth. Even if you put on a 'taller' tire, the differences between the 16 and 17 inchers will not be great due to the limited selection of tires that will fit within the swing arm.
Jerry Fields
'82 XJ 'Sojourn'
'06 Concours My Galleries Page. My Blog Page.
"... life is just a honky-tonk show." Cherry Poppin' Daddy Strut
As I mentioned, it depends a lot on the tire you put on the bike. I did not check some other tires, probably a few that are bigger than the ones I noted.
My point is that lower RPM is not automatic when going to the 17 inch rim, you need to pay attention to tire selection as well.
In theory, a 130-90x16 tire has a circumference of about 2012 mm. A 140-80x17 has a circumference of about 2060 mm. That means for every tire rotation, the 17 inch tire travels 48mm more than the 16 incher. Doing the math, this comes out to about a 2.4 percent difference. 5,000 RPM with the 16 incher would be reduced to 4,880 RPM with the 17 incher. Again, in real life these numbers may be different.
On the other hand, the 750 final drive changes your gear ratio from 3.3 to 1 to 2.9 to 1, a difference of roughly 9 percent. This will give a greater reduction in RPM than the 17 inch tire swap. Of course, you could combine the 2 and get an even greater reduction in RPM.
In short, the 17 inch tire swap is not a magic bullet in terms of RPM reduction.
Jerry Fields
'82 XJ 'Sojourn'
'06 Concours My Galleries Page. My Blog Page.
"... life is just a honky-tonk show." Cherry Poppin' Daddy Strut
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