# Rear wheel centered at seatstays but offset at chanstays

Built up a new bike. All components are new and unused. As title suggests, rear wheel sits right in the middle of two seatstays (checked with ruler and vernier caliper) but is off by ~3mm at chainstays. To eliminate the obvious:

• This is a thru axle frame, so incorrectly seated QR axle is not an issue
• Wheel is true. In fact very true.

3mm may not sound like much, but given overall 45mm clearence of the frame at the stays it is actually a lot and is noticeable when high volume tires are on.

If it was off at both chainstays and seatstays I would assume that wheel is not correctly dished. However one is off and onother one is OK... If I try to correct wheel offset in one place by changing the dish I will inevitably get the wheel off center in another area...

Any ideas?

UPDATE 2021-09-22:

First of all thanks everyone for contributing.

After reading comments by @Criggie I was tempted to try and measure the frame with the taut string from the headtube (or seattube) to both rear dropouts. However having done calcs on paper (my math skills are poor...), I realized that for deviation of ~3mm at the wheel rim, I am looking for deviation of around .3mm at the dropout. I don't think this is something I can reliably measure with a string.

Feel free to correct me if my math is wrong:

• Rim diameter is 622mm (standard 700c rim)
• Axle total length is 142mm (half length 71mm)
• Perceived deviation of the rim at chainstsays: lets assume 3mm based on my manual measurements. Could be a bit less or more.
• Calculated deviation angle: 0.276 degree
• Calulated offset of dropout to achieve that angle is 0.34mm

At that point I dropped the idea of measuring it.

Now I am looking at two options:

Option1. Ignore it and just ride.

• If I stick to manufacturer's recommended max tired width I still get clearence of ~4mm between left chainstay and the tire. Plenty?
• I don't know of any potential issue with the wheel being not perfectly centered between chainstays. Please let me know if you do

Option2. Contact the manufacturer.

• Frame is still under warranty.
• They will likely want me to send the frame-only for inpection. That means opening and removing all hydraulic lines (routing is internal). Removing gear shift cable. On re-assembly I will need new olives + barbs for hydraulic lines and potentially complete replacement of the front hydraulic line, because it is currently trimmed at the minimum length...
• I'm confused. On most bikes the rear wheel is offset to account for gearing. Sep 21, 2021 at 22:12
• @DanielRHicks but the rear wheel should be dished to centre the rim in a (symmetrical) frame, shouldn't it? Sep 22, 2021 at 7:49
• If you feel like it and the asymmetry gives you noticeable trouble you can potentially "adjust the dish" (is that a term?), i.e. change the position of the rim relative to the axle, so that its position is a compromise between the two stay pairs. Then both of them will only have a 1-2mm asymmetry. Sep 22, 2021 at 11:09
• @ChrisH - And that seems to be what Opie is describing. Sep 22, 2021 at 11:43
• @DanielRHicks so the rim should be centred between the (planes of the) dropouts. If the frame is symmetrical, it should be centred between seatstays (it is, and probably would be even on a non-symmetric frame) and chainstays (it isn't). If the wheel is good, it's either sitting wrong in the frame, or the frame isn't symmetric - and in the wrong direction. Sep 22, 2021 at 11:55

I have read through the comments on the other answer and want to clarify that flipping the wheel eliminates the possibility that the wheel is incorrectly dished.

Therefore, the only posibility is that the problem is with the frame. Either the tubing has been cut in slightly different places meaning that one chainstay has a different profile to the other or the drive side dropout is closer to the bottom bracket than the non-drive dropout (the driveside chainstay has been cut marginally too short or the dropout misaligned). The second scenario can be tested by checking the alignment of the wheel with the seat tube.

Either way, you will most likely find that this is within acceptable tolerances for many mass production frames. The regulations are surprisingly sloppy and not every frame is built by a master craftsman.

• The frame is from one of the UK smaller frame building companies and is not cheap for an aluminium. If this is a problem with the frame what do you think the impact will be in practical terms (if any)? Something to worry about or safe to ignore? Sep 21, 2021 at 18:33
• @ArtGertner It would be good to check dropout alignment and rear triangle alignment before coming to a conclusion on whether to live with it or pursue warranty. Sep 21, 2021 at 19:30
• @ArtGertner on a soft material like aluminium, even the "hairs" of the tyres will eat into the frame in a surprisingly small mileage if they are close enough to touch. Look at my poor old Cannondale Slate (very tight clearances), where that exact thing happened. Otherwise the bike should behave fairly normally; you probably (almost certainly) won't feel it when riding but these things can play on your mind. You could ask the advice of the low volume frame builder and hopefully they will set your mind at rest or at least offer some possibilities. Sep 21, 2021 at 19:43
• This explanation crossed my mind, but it's hard for me to picture. Frames are almost always built in jigs that hold the dropouts in a fixed position relative to the bottom bracket—in order for this to happen, the jig would need to be bent. Not sure how else to explain it though. Sep 21, 2021 at 19:54
• @ChrisH, it's Mason Bokeh Alu Sep 22, 2021 at 13:15

On many bikes the right chainstay is shaped to allow bigger cogs on a proper chainline. I'd hazard a guess it's closer to the right chainstay than the left. Here's an old but extreme example (Merlin XLM), and here's a picture showing an expensive workaround - a carbon chainstay that's thinner on the right (images aren't suitably licensed to embed).

• Yep. Valid guess. However this frame is symmetrical. And the wheel is closer to the left (NDS) chainstay.... by ~3mm Sep 21, 2021 at 15:41
• I have heard of a wrongly built frame causing this (a friend's cargo bike had to be returned for it, something daft like using the wrong jig for assembly). Sep 21, 2021 at 15:43
• Can you flip the wheel with that axle? Just to eliminate any bias in the build (e.g. bent truing stand) and eliminate the possibility that it's the seatstays that are out, (if you trued the wheel in the frame) You might need to take the cassette off, and I haven't tried that for the rear wheel on any of my modern bikes only an old BSO. Sep 21, 2021 at 15:48
• I really don't see the point in flipping the wheel (unless I have some fundamental misunderstanding of basic geometry...). But as you are not the first person to suggest that, I have just gone to the garage and flipped it. Surprisingly it fits easily wrong way around (as long as derailleur is fully collapsed and out of the way). Even brake disk does not catch anything. I re-installed amd tightened the thru-axle. The allignment issue is exactly as it was. Wheel is still closer to NDS chainstay by about 3mm. And is still dead center between the seatstays... Sep 21, 2021 at 15:55
• I will try to take some pictures later tonight. It is hard to capture on camera though with the wheel getting in the way. Sep 21, 2021 at 15:56