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Old 11-29-06, 11:51 PM   #1
sogood
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Change wheel = RD readjustment?

Just wondering, is it normal to need to readjust the RD after a rear wheel change?

I switch b/n my Fulcrum Racing 1 (Veloce 12-25) and Mavic Ksyrium ES (Chorus 12-25), and each time I had to readjust the RD to get it running smoothly again. It seemed that the outer limit position is different b/n the two.

Any suggestions?
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Old 11-30-06, 05:09 AM   #2
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Yeah. In a perfect world you wouldn't have to readjust your derailleur but, in real life, it's common. Sometimes you have to fiddle with your brakes too.
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Old 11-30-06, 05:17 AM   #3
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Quote:
Originally Posted by Retro Grouch
Yeah. In a perfect world you wouldn't have to readjust your derailleur but, in real life, it's common. Sometimes you have to fiddle with your brakes too.
Thanks. I have already noted that the pad to pad distance has to be increased b/n the two wheel. That's easy to adjust. But the RD adjustment seemed to be more than a few turns in the cable adjuster. A bit of a pain as a matter of fact.
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Old 11-30-06, 06:54 AM   #4
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That seems odd to me. My cross bike has 2 sets of wheels (11-23 & 12-25), and I don't have any issues swapping the wheels. Any differences in the cassettes?
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Old 11-30-06, 07:17 AM   #5
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Originally Posted by idcruiserman
That seems odd to me. My cross bike has 2 sets of wheels (11-23 & 12-25), and I don't have any issues swapping the wheels. Any differences in the cassettes?
It's a hub thing. Some of them snuggle the freehub up to the right dropout better than others.
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Old 11-30-06, 07:45 AM   #6
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Originally Posted by waterrockets
It's a hub thing. Some of them snuggle the freehub up to the right dropout better than others.
And it's a dish thing. If the two wheels aren't dished exactly the same (not a millimeter or two off), then you have to tweak the derailleur.

Bob
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Old 11-30-06, 08:02 AM   #7
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Really? After my old wheel blew up, trek sent me another one as a replacement. Same wheel, but the brakes were off and its not shifting as smoothly.
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Old 11-30-06, 08:34 AM   #8
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Sometimes you can play around with spacers behind one of the cassettes to make them match once the wheel is in the frame. Every once in a while this also can be done by respacing the hub axles, but is harder to do on modern wheels/hubs. You should be able to do this so the only monkeying is some brake pad width adjustment.
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Old 11-30-06, 08:49 AM   #9
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Quote:
Originally Posted by Bobby Lex
And it's a dish thing. If the two wheels aren't dished exactly the same (not a millimeter or two off), then you have to tweak the derailleur.

Bob
I'm not sure where you're going with that... "Dish" typically refers to centering the rim between the locknuts, or since some sealed bearing hubs have no locknuts, between the axle ends. While a dishing problem might require the brakes to be recentered, the cassette and derailleur don't "know" this is going on! The derailleur is going about its business, but it doesn't know that the cassette, due a small design difference in the hub, has moved a millimeter or two left or right of where it was on the previous wheelset. This condition requires a adjusting barrel tweak and a quick limit screw check before riding.

When we have customers who are buying a new bike or wheelset, we offer to tune the cassette positions on the hubs so that no adjustments are ever necessary when changing wheels. It's nice to know you can just throw it in there and have it work!
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Old 11-30-06, 08:52 AM   #10
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Quote:
Originally Posted by Adiankur
Really? After my old wheel blew up, trek sent me another one as a replacement. Same wheel, but the brakes were off and its not shifting as smoothly.
Are you running 10 speed? There's an easy-to-forget thin silver spacer that *must* go behind the cassette on all but Shimano's 10 speed specific hubs in order for the thing to work properly. It your cassette a little loose on the hub? That's where I would start.
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Old 11-30-06, 10:11 AM   #11
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Bikewise is correct, dishing is refering to the location of the rim, which does not affect the hub. But if Bobby Lex meant that some hubs can be offset more or less than others, that would be correct (like waterrockets said). That being said, I had only minor adjustment needed when I was swapping between an Ultegra 8 speed rear and a Dura Ace 7 speed hub modified with a longer axle and an 8 speed custom Mavic freehweel. So you shouldn't need more than a few twists. Try to find a happy medium between the two wheels and then the twists should balance it out.
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Old 11-30-06, 03:31 PM   #12
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Originally Posted by BikeWise1
I'm not sure where you're going with that...
Well, for example, the derailleur limits might have to be adjusted if the dish isn't the same between the two wheels.

Bob
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Old 11-30-06, 03:59 PM   #13
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I would have thought the only thing affected by dish would be the brakes spacing from the rim
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Old 11-30-06, 04:21 PM   #14
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Quote:
Originally Posted by lennyk
I would have thought the only thing affected by dish would be the brakes spacing from the rim
This is correct. Dish and rear der adjustment are completely unrelated. Even if you have no rim or spokes at all, the same der adjustment applies.
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Old 11-30-06, 04:49 PM   #15
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Originally Posted by waterrockets
This is correct. Dish and rear der adjustment are completely unrelated. Even if you have no rim or spokes at all, the same der adjustment applies.
Nope.

Dish pulls the hub right or left. That will affect how far the derailleur has to travel, because the derailleur is independent of the hub. Therefore the derailleur travel limit screws may have to be adjusted if you switch wheels.

Bob
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Old 11-30-06, 05:02 PM   #16
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Quote:
Originally Posted by Bobby Lex
Nope.
Dish pulls the hub right or left.
Bob
Ummm, have you ever built a wheel? Because when I put it in my truing stand, dish pulls the RIM right or left, but the HUB is held quite firmly in place by the stand. Similarly, the hub is held firmly in place by the dropouts in the frame. I dare you to put a wheel on your bike, then tighten all of the right spokes 1/2 turn, then see how far the hub has moved. NADA! Now look at the rim... it should be almost touching the right brake pad. Please stop arguing with him, as you don't seem to know what dish really means. Thank you.

edit: There IS one way to adjust the position of the hub, but that would require spacers, and that still would not alter the dish, but rather make it necessary to adjust the dish on the spokes.
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Old 11-30-06, 05:05 PM   #17
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Quote:
Originally Posted by Bobby Lex
Nope.

Dish pulls the hub right or left. That will affect how far the derailleur has to travel, because the derailleur is independent of the hub. Therefore the derailleur travel limit screws may have to be adjusted if you switch wheels.

Bob
Nope, dish effects only the rim relative to the frame. You're thinking about hub flange offset which may vary from hub to hub.

Al
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Old 11-30-06, 05:10 PM   #18
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Quote:
Originally Posted by Bobby Lex
Nope.

Dish pulls the hub right or left. That will affect how far the derailleur has to travel, because the derailleur is independent of the hub. Therefore the derailleur travel limit screws may have to be adjusted if you switch wheels.

Bob
You're wrong. Take it like man and admit it and move on. Posing now only makes you look worse.
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Old 11-30-06, 05:19 PM   #19
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Haha, I beat Al and Operator to it
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Old 11-30-06, 05:43 PM   #20
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Yes, I understand that dishing has nothing to do with this problem. But the mention hub flange offset makes me wonder if that's the setting that needs/should be adjusted on one or the other wheel? Or should one just stay with the spec and not touch it and live with the RD adjustments each time one change wheel.
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Old 11-30-06, 06:01 PM   #21
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If it was my bike and I changed wheels very often, I'd make it work.

You probably need to stick about a 1mm washer under drive side locknut on one of the wheels. The trick is figuring out which wheel needs to be modified.
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Old 11-30-06, 06:19 PM   #22
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Thanks guys!

My second free service (part of bike purchase) is due soon, I'll get the LBS to figure this spacing thing out. Given that I bought both the bike and the extra Mavic wheels from them, they won't have a lot of room for excuses.
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Old 11-30-06, 06:37 PM   #23
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Haha, I beat Al and Operator to it
The one time I stop refreshing the mechanics forum every 30seconds I get beat by urbankinght.

Goddamnit!

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Old 11-30-06, 08:03 PM   #24
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The one time I stop refreshing the mechanics forum every 30seconds I get beat by urbankinght.

Goddamnit!

Yeah, he's sneaky alright.
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Old 11-30-06, 08:21 PM   #25
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Quote:
Originally Posted by Bobby Lex
Nope.

Dish pulls the hub right or left. That will affect how far the derailleur has to travel, because the derailleur is independent of the hub. Therefore the derailleur travel limit screws may have to be adjusted if you switch wheels.

Bob
lmao Think really hard about it. The frame dropouts are the reference point. The bike doesn't hold the wheel at the rim.
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