Bicycle Mechanics - Dura Ace 7800 rear wheel mount problem
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02-12-12, 12:18 AM
This may be my imagination, but it seems to me it is more difficult to replace a rear wheel with the 7800 Dura Ace components than with most other components. I have not been riding and maintaining road bicycles very long, maybe 5 years. I have had mostly Shimano equipped bikes, which include 105. Ultegra, Tiagra and 9 speed Dura Ace.
I have not had a problem mounting the rear wheel until a month or so ago when I bought a used Cannondale with 7800 components. Thought it was just me. However, today my wife also bought a used Schwinn Peloton LTD with 7800 components. I replaced the tires for her with new rubber, but when I started to mount the rear wheel I again had a problem.
Is this my imagination, I am doing something wrong, or is the 7800 contrary?
02-12-12, 01:40 AM
I don't understand the question. What part of "mounting the wheel" are you having trouble with?
02-12-12, 08:09 AM
Do you put the chain on the smallest rear cog before removing the wheel? As the other poster said you didn't state what your problem is. Roger
I can't see that any one wheel would be significantly harder to mount than any other of the same width.
The key is to get into the habit of always mounting with the RD shifted to high gear, and the chain on the smallest sprocket. there are also sometimes small differences in hangers which can limit clearance and access to the axle slots.
Lastly, if you're willing to modify, here's a few tricks from the old days of setting up race bikes.
If the axle locknuts have very square outer corners, grind a small chamfer (bevel) onto them. Likewise with the areas at the bottom of the dropouts and front of the hanger. The chamfers in the areas where the axle and frame first meet can reduce the odds of the axle hanging on an edge and help guide it into the slot. This is SOP on front dropouts, but often not on rears and is one reason folks sometimes have more grief mounting rear wheels.
I'm aware that there are many here who would never touch a file to their pristine frames, so the advice is only for those who's sensibilities it doesn't offend.
02-12-12, 08:38 PM
As the op of this thread, I will try to explain. Yes, I always shift to the big ring and small cassette cog. I have done this many times with my other bikes with Shimano components and the wheels slips easily into place. With the 7800 Dura Ace on both my bike and my wife's bike it is always a struggle to get the wheel to slide into place. It just seems odd that I have not had difficulty with other Shimano components. I do eventually get it done, but it is never easy. My question is: Is the 7800 different in some way which would require something different in mounting the wheel, or is it just coincidence?
My question is: Is the 7800 different in some way which would require something different in mounting the wheel, or is it just coincidence?
Occasionally being harder might be a coincidence. Consistently, on either bike means something is different.
In my last post I described how to improve mounting ease by beveling the outside of the locknuts (or axle faces). You might compare the shape of the Dura axle faces and your other hub's. If the Dura has squarer corners, or even flared ends, this can catch on the dropout rather than guide it in.
It could also be that the Dura hub is slightly wider or narrower than your other hubs and therefore not as perfect a fit in the frame.
I've had some hubs that frequently snag, and my commuter always was a pain until I filed "funnels" in the non contact area on the underside of my rear dropout.
I think you will find it easier to have the chain in the small chainring instead. It's only cross-chaining during installation, but the lessened tension and extra chain slack will help you work the axle and cassette past the RD and onto the dropout.
I've not heard of any 7800 issues regarding wheel difficulties. I'm assuming both bikes are spaced for 130mm spacing.
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