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I've had some new wheels built for a steel frame with a 126mm rear dropout spacing. The rear hub takes a 7 speed screw-on freewheel. At the moment the rim sits perfectly central to the chainstays when the axle is pushed to the back of the horizontal dropouts on both sides. However, I've discovered that there isn't enough room for the chain on the highest (14 tooth) gear because it is too close to the chainstays.

What would be the consequence of adjusting the wheel away from the frame on the drive side (about 3mm should do it) by adding washers on the drive side and removing them on the opposite side of the axle?

Could offsetting the wheel in this way affect braking? Is it likely to be detrimental to the chainline? Would it be advisable to use adjustment screws in the dropouts to make sure the front edge of the rear rim continues to be centred between the chainstays?

Any advice would be much appreciated!

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    Are the new wheels 126 mm? (Not sure why you'd do that on a steel frame; most people would have just spread the frame and put some 130mm wheels)
    – Batman
    Mar 18, 2018 at 21:25
  • Personally I'd just add a spacer washer to the Right hand side, one at a time until the rub goes away. You might consider adding a thin aluminium scratchguard at that point on the stay too, to catch any witmess marks and protect the frame from scoring.
    – Criggie ♦
    Mar 19, 2018 at 0:37
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    Your other fixes are to drop to a 13 or 12 tooth high gear, but they're probably vanishingly hard to find. Or to replace the hub with a 7 speed freehub and casssette. I ran a 12-28 7 speed cassette on a previous bike, and they were available in 11-25 as well. Functions exactly the same for shifting, but has a better axle and smaller high-gear options. Freewheels are very old tech and the replacement freehub + cassette is superior in almost all ways.
    – Criggie ♦
    Mar 19, 2018 at 0:39
  • The new wheels are 126mm, yes. I haven't had the frame cold set because although I knew that was an option, it wasn't recommended to me at any point - either by my local mechanic or by the shop that built the wheels. Perhaps I didn't ask enough questions.
    – eddie_c
    Mar 19, 2018 at 9:38

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Random interference with the chainstays/seatstays/dropouts like this just happens sometimes. It's not really anyone's fault.

If you added 3mm of spacer to the drive side and took 3mm away from the non-drive side, the wheel will be out of dish. That's fixable, at the expense of increasing the left-to-right spoke tension disparity, creating less total tension and a weaker wheel. (A nice new handbuilt wheel with a modern rim will already have the drive-side spokes at the highest tension the rim can take without risking cracking at the spoke holes, so the only place you can go here is reducing tension on the left side, so less total tension). The chainline will be affected but it's not likely to matter. You'll also have increased the unsupported span of drive-side axle, which is already borderline too much for some riders on 7-speed freewheel hubs, although that depends on you and your style.

Adding an equal amount of spacer on both sides, putting in a longer axle, and spreading the frame is likely a better approach then re-dishing the wheel. It negates all of the above downsides other than the unsupported axle part. It's always technically possible for bad things to happen as a result of spreading the frame, but for the most part this fear is an invention of people who aren't aware of the level of cold-setting punishment steel bikes receive when they're built. In actual practice, steel frames can be spread and aligned with almost total impunity.

A lot of nice 7-speed freewheels were made with 12-tooth small cogs. If that bought you the clearance you need and you could also get the gearing you need, that route sounds like the best one to me. It does mean being reliant on vintage drivetrain parts, which isn't ideal, but old freewheel cogs kind of last forever anyway so I wouldn't sweat it here.

Crimping/indenting the stay can also be a totally reasonable solution depending on what part of it is interfering and how much you'd need to do it by. Many, many bikes are made with partially flattened stays to help with clearance.

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If you’re replacing a 126mm with a 126mm then it sounds like whoever built the wheel didn’t know what your hub offset was.

You further clarified that you replaced a 6-speed freewheel with seven speed, which would of course change the chain line on the smallest cog. This isn’t the wheelbuilders fault. You can follow the advice here or go back to 6 speeds.

You can change it by switching spacers from one side to the other but then your wheel dish might be a few mm off. It won’t matter for most things and most brakes should be able to adjust slightly to compensate. But your wheel tracking will be slightly off and brakes slightly off. You might not ever notice it.

Ideally, you’d have the builder or the bike shop re-dish. If it’s just a few mm they should be able to do it with the existing spokes unless they didn’t give themselves enough breathing space when they originally built it.

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    Having spoken to the wheel builders, they told me they wouldn't recommend spreading / cold setting the frame as that could interfere with the gear shifting. They said that especially on short frames, the chain stays would have to be spread through a greater angle in order to achieve the correct space. I asked about re-dishing too but they said that may also affect the chain line if the bike was not originally designed for 6 speed. At this point I'm inclined to get hold of a 6 speed freewheel and use that instead.
    – eddie_c
    Mar 19, 2018 at 13:55

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