Rear wheel / geometry change - Chicagoland Sportbikes
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post #1 of 12 (permalink) Old 09-14-2011, 11:43 AM Thread Starter
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Rear wheel / geometry change

I have 2 rear rims for the Aprilia. One I think is 5.5" and the other is 6" width. The 6" takes a 190 rear tire, the 5.5" takes a 180.

So how much is this going to change the ride height, gearing and geometry of the bike swapping between the 2?

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post #2 of 12 (permalink) Old 09-14-2011, 01:53 PM
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Wouldnt that depend on the profile of the tire too? You could theoretically have a close to same ride height with the different widths if the profile changes. With the width change of the tire and the rim, theoretically you could still have a very close cross radius on the tire for minimal change in that too.(rounded profile vs. triangular profile on the radius of the tire)

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post #3 of 12 (permalink) Old 09-14-2011, 02:27 PM

 
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It depends on the difference in height of the tire. Gearing, you just change as need with sprockets, like you would when tuning any bike for any track.

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post #4 of 12 (permalink) Old 09-14-2011, 03:09 PM Thread Starter
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I'm confuesd right now...

Basically the 5.5" width rim is made for a 180. The 6" width rim is for the 190. The 180 is a shorter and narrower. The 190 is taller and wider. I could run the 190 rear on the 5.5" rim but the side wall and the way the tire beeds on the rim would be a little different than it mounting on the 6". I'll play around with it and see.

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post #5 of 12 (permalink) Old 09-14-2011, 03:17 PM
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I have run about 90% 190 tires on my 5.5" rear rim. I prefer it to the 180. Give it a try you might like it
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post #6 of 12 (permalink) Old 09-14-2011, 03:31 PM
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go to the ire mfg's web site, and get the revolution per mile (usually listed in specs) for each tire, divide 1 by the other, and that is your percentage change.

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post #7 of 12 (permalink) Old 09-14-2011, 06:16 PM

 
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The width has nothing to do with the geometry, just the over all height. But the change is probably negligible.

Typically you run the 190 when you need more grip. If you're not having traction issues, then there isn't much benefit. Especially since the bigger tire costs more.

The wider rim and bigger tire will add more unsprung mass. More weight and more rotational / gyroscopic effect. The extra mass and wider rim might make the bike handle a bit heavier at turn in. It may want to stand up more on exit.

Give it a try. I wouldn't worry to much about the geometry. If your concerned, just raise the front forks a few mm when you put the 190 on.

Make sure if you swap the wheel, that the front and rear sprockets are in line. Especially if the rim is from a different bike.

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post #8 of 12 (permalink) Old 09-14-2011, 10:00 PM

 
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post #9 of 12 (permalink) Old 09-14-2011, 10:05 PM
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Quote:
Originally Posted by gkotlin View Post
just raise the front forks a few mm when you put the 190 on.

.
se, I was totally gonna say just slide the forks up to compensate. but he beat me too it.




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post #10 of 12 (permalink) Old 09-14-2011, 11:21 PM
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I bet one of these would help
http://en.wikipedia.org/wiki/Ruler

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post #11 of 12 (permalink) Old 09-14-2011, 11:52 PM

 
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I thought the 190 would cause the handling (steer/lean speed) to be slower, but other than that it's about the same? Unless you use the 5.5 rim.

Yes/no?

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post #12 of 12 (permalink) Old 09-15-2011, 09:14 AM Thread Starter
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Quote:
Originally Posted by PCD_inc View Post
I say your overthinking, Just run it sissy LOL
LOL! That's what I'm doing

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