Problem with Swapping Rear Racing and Training Wheels
I have a set of racing and training wheels for my road bike. Now that the road season has ended I put the rear training wheel back on. Both wheels have the same cassette and ratio. A problem I'm having is that the chain isn't working well in the easiest gear in the back but it's working well in all the other gears. When I first put the racing wheel on, I had the opposite problem; the chain didn't work well in the hardest gear. I did adjust the tension, and that helped somewhat. However, I think I need to adjust one of the derailleur screws. Which screw do I need to adjust, and in which direction?
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It sounds like you need to adjust the "limit" screws which set the inner and outer derailleur travel limits. When you said the easiest (largest) cog isn't shifting well what is the symptom? Is the chain not going all the way onto the cog or is it overshifting the cog? If the former, loosen the low limit screw a 1/2 turn and see if that is enough.
BTW, your problem is very common. Even "identical" wheels with the same cassette, etc. often require minor limit screw adjustments when swapped. |
Originally Posted by HillRider
(Post 22657119)
It sounds like you need to adjust the "limit" screws which set the inner and outer derailleur travel limits. When you said the easiest (largest) cog isn't shifting well what is the symptom? Is the chain not going all the way onto the cog or is it overshifting the cog? If the former, loosen the low limit screw a 1/2 turn and see if that is enough.
BTW, your problem is very common. Even "identical" wheels with the same cassette, etc. often require minor limit screw adjustments when swapped. |
The key to using multiple wheels on the same bike is matching the "freewheel position offeset" on all the wheels. That's the distance from the inside dropout face to the high gear sprocket. These usually vary slightly between brands, and can throw off indexing if not matched.
Matching is achieved using a shim behind the cassette to bring it out to the needed offset from the axle face. I've done this with most of my personal rear wheels, and BITD when working with race teams, matched 100% of the wheels used, both on bikes and spares. This ensured that any wheel swapped out in a race would be compatible with the bike. To do this, you'll need an assortment of shims and a depth gauge to measure the step from axle face to sprocket. |
On limit screws - on lesser derailleurs, the high gear (small cog) limit screw is usually labeled "H" and the low gear limit "L". On better derailleurs, I think it is assumed the mechanic knows and frequently they are not labeled. To find out which is which, screw one screw in two turns. Now pedal and shift. Note which cog you cannot get into.
As said above, cassettes/FWs on different wheels often do not exactly line up with the previous. Making the switch might be as simple as screwing in the "L" 1/4 turn and the "H" out that same 1/4. Once you find what your wheels need, doing the switch without issues can become simple. (Now, bikes have enough vagaries that I could be totally out to lunch. :)) Edit: I hadn't heard of FB's shimming to make wheels consistent but it makes sense and I like! I raced with close to Japan's finest; identical hubs and freewheels BITD and did the swaps, training to racing and back doing nothing. And funny because it is a little related and I just did it. How to make thin spacers. (The shop I went to had only 1mm ones.) I took aluminum sheet, nailed it to a piece of plank, secured the plank under my drill press, hole saw drilled the ID then did the same with the OD. So easy I made four. These to use on a fix gear where I am running the cog flipped so the cog surface butts up to the spokes. With a low flange hub and 19 tooth or larger cog, just fine but smaller cogs require spacers to keep the chain off the spokes. I want it dialed in to the bare minimum to allow as many lockring threads as possible. |
Originally Posted by 79pmooney
(Post 22657316)
.....
As said above, cassettes/FWs on different wheels often do not exactly line up with the previous. Making the switch might be as simple as screwing in the "L" 1/4 turn and the "H" out that same 1/4. Once you find what your wheels need, doing the switch without issues can become simple. (Now, bikes have enough vagaries that I could be totally out to lunch. :)) Also note that while makers of index cassettes are very diligent about sprocket spacing on all the inner sprockets, and likewise the lever's index cam, they allow themselves greater margin of error for the high gear sprocket. The index system may allow an overshift, or slack cable condition with the assumption that the RD position will depend of the limit rather than the lever. |
Before turning screws, I'd try turning the barrel adjuster 2-4 clicks and see IF that works. Just keep track of how many to restore it to the original position.
You may still have to adjust a screw (try 1/8 turn at a time until it "just" reliably works. Keep it as minimal as you can and it might work OK in both scenarios. IF you end up having to turn screws a bit every time you swap wheels, you may want to invest in a JIS Phillips screw driver. It fits the screws properly. |
Originally Posted by AMoney
(Post 22657104)
I have a set of racing and training wheels for my road bike. Now that the road season has ended I put the rear training wheel back on. Both wheels have the same cassette and ratio. A problem I'm having is that the chain isn't working well in the easiest gear in the back but it's working well in all the other gears. When I first put the racing wheel on, I had the opposite problem; the chain didn't work well in the hardest gear. I did adjust the tension, and that helped somewhat. However, I think I need to adjust one of the derailleur screws. Which screw do I need to adjust, and in which direction?
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Originally Posted by Bill Kapaun
(Post 22657447)
...
IF you end up having to turn screws a bit every time you swap wheels, you may want to invest in a JIS Phillips screw driver. It fits the screws properly. |
Originally Posted by FBinNY
(Post 22657309)
l
To do this, you'll need an assortment of shims and a depth gauge to measure the step from axle face to sprocket. |
Originally Posted by tFUnK
(Post 22657724)
Where does one source these very thin shims? At the hardware store? I've tried to do this once and only managed to find 1mm being the thinnest, which was still a bit too thick.
https://wheelsmfg.com/products/hub-p...e-spacers.html Else, a pop can, heavy scissors and a 7/16" (for a 10mm axle) one of these. https://www.harborfreight.com/9-piec...EaAtllEALw_wcB |
If the amount it’s off by is as small as I suspect you could probably shim under the drive side locknut as well.
Shim stock, tin snips, a nibbler, and for thinner things a throwaway pair of scissors works fine. For those wanting to buy, the links above cover it. I’ve gotten many a provision shim washer from both McMaster Carr and Misumi, though that may be overkill. |
Originally Posted by cxwrench
(Post 22657453)
So you trained all year on your race wheel? What's the point of having training wheels?
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Originally Posted by HillRider
(Post 22657119)
It sounds like you need to adjust the "limit" screws which set the inner and outer derailleur travel limits. When you said the easiest (largest) cog isn't shifting well what is the symptom? Is the chain not going all the way onto the cog or is it overshifting the cog? If the former, loosen the low limit screw a 1/2 turn and see if that is enough.
BTW, your problem is very common. Even "identical" wheels with the same cassette, etc. often require minor limit screw adjustments when swapped. |
Originally Posted by FBinNY
(Post 22657324)
Note, if the cassette position varies enough to require adjustment of the limits, it's very likely that it will also require adjusting the RD trim to index properly.
Also note that while makers of index cassettes are very diligent about sprocket spacing on all the inner sprockets, and likewise the lever's index cam, they allow themselves greater margin of error for the high gear sprocket. The index system may allow an overshift, or slack cable condition with the assumption that the RD position will depend of the limit rather than the lever. |
Originally Posted by AMoney
(Post 22657852)
I'm a bit confused. I thought that only front derailleurs had trim.
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Originally Posted by AMoney
(Post 22657852)
I'm a bit confused. I thought that only front derailleurs had trim.
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Originally Posted by AMoney
(Post 22657848)
I kept the racing wheels on since April because I didn't know to adjust the derailleur when swapping wheels. My thought process was to at least have the training wheel on from now until next March or April. Next year, I might swap the rear wheels during the racing season more frequently.
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Originally Posted by 79pmooney
(Post 22657455)
I have a Phillips that I ground down the tip of. Works beautifully in those JIS screwheads.
It works nicely with phillips screws (no worse than any Phillips screwdriver), and it works wonderfully with JIS (Shimano and Yamaha stuff mostly). |
Originally Posted by Bike Gremlin
(Post 22657911)
Used that, but getting a proper JIS screwdriver was a very nice change - even compared to a ground-tipped phillips screwdriver.
It works nicely with phillips screws (no worse than any Phillips screwdriver), and it works wonderfully with JIS (Shimano and Yamaha stuff mostly). |
Originally Posted by Bike Gremlin
(Post 22657911)
Used that, but getting a proper JIS screwdriver was a very nice change...
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