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This is a 135mm OLD wheel mounted in a 130 mm frame. I removed spacers from the axle to make it 130mm. I then put the wheel in the frame and proceeded to dish. I made sure the distance between the rim and the chainstays (where the chainstays are the narrowest) was equal (approximately 25mm in my case). All is nice and square but....

I put the rim flat on 3 mugs and stacked coins from the floor to the nut one side (axle is not centred so I used the nuts), then I flipped the wheel and took the same measure and it appears that there is a difference of 8mm! I could re-dish based on the wheel rather than the frame and get spokes tensioned evenly but then it will not be in the middle of the chain stays again.

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What am I missing? Could it be the frame that is bent?

Edit: Additional pieces to the puzzle .. First, I attached a string around the frame and measured the distance between the seatpost tube and the string, it seems very close on each side but indeed the NDS seems closer to the seatpost tube by 2 to 2.5 mm. If you think I measured wrongly let me know and I will do it again. It's not easy so I tried with 2 methods (toothpick at 90 degrees resting on a square box and wooden square). I wonder if a 2 to 2.5mm difference here could explain the 8mm of dish. Not sure this all adds up.

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(On this photo the mudguard is off I know but the fork is straight)

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Secondly, the original axle from 25y ago was dug out. It's the 146mm version which would indicate (according to the shimano exploded view of the hub) that it was a 135mm, and that the frame was bent. That said, the dropout are so thick (8.4mm) that even a 146mm fits on the frame as a "130mm" version and the axle does not protrude from the dropouts.

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Edit 2: As required, photos of the seatstays. The wheel is centred in the chainstays (spokes on the drive side much more tightened) but not in the seatstays (4mm closer to the drive side):

Drive side: enter image description here

Non drive side: enter image description here

Overall seems fairly aligned with the seat post: enter image description here

tweedi
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    Have you got the time to test the frame for alignment ? Need some string and a ruler. It kinda sounds like the right dropout is squashed in and the wheel was dished to match. – Criggie May 02 '22 at 23:33
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    Immediate thought is it was originally a 135mm frame. – mattnz May 02 '22 at 23:47
  • Oh dear. What are we going to find out with this bike again. It's 25 years old and was my dad's, now I commute to work each day with it. I restored it 2 years ago and put that 135 mm wheel which needed adjustment (less spacers), rode a lot like this and the frame has not changed since. It's exactly 130mm between dropouts but.. I think I still have the original axle of the FH-MC30 7 speed which was on the bike when sold new, the length could help with the investigation. I do have a ruler and string. Should I put the string between the dropouts and tie it up at the fork to check symmetry? – tweedi May 03 '22 at 00:04
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    Another thought, test the dropouts for alignment using two nuts/bolts. They should point straight at each other across the centerline. BTW I really like your test setup for the wheel - very creative ! – Criggie May 03 '22 at 01:17
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    Test the alignment & dish by turNing the wheel around in the dropouts. Is it still central when installed the wrong way around? – Noise May 03 '22 at 07:51
  • I added more information and photos. I'm still very much confused and don't know if this is a 130 or 135mm frame and more importantly how to adjust the situation to have a wheel correctly dished and also centred in the frame. Thanks a ton for your help. – tweedi May 03 '22 at 09:50
  • I have an additional question: have you checked the dish at the seat stay as well as the chainstay? 2-2.5mm alignment is minimal, don't worry about that. There is no adjustment you can make to this frame to account for that anyway. – Noise May 03 '22 at 16:32
  • @tweedi i think from a reliability point of view, having the OLD at 130mm and the wheel centred between the stays will give you the best use and lifespan out of the bike. You don't use the rear wheel back to front anyway, do you? – Noise May 03 '22 at 16:33
  • Thanks Joek, how do you verify the dish at the seat stay? – tweedi May 03 '22 at 19:09
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    @tweedi You'd just stick the wheel in the dropouts properly. Check it's central in the chainstays. Then without altering the wheel attachment, check it's central between the seat stays. It should be central to both at the same time. If it's not, there's a clue to what is going on. – Noise May 03 '22 at 19:11
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    @tweedi Avoid modifying the frame even a couple of mm with aluminium. The material is not suitable for this and it will weaken. – Noise May 03 '22 at 19:13
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    @Joek thank you. Added photos of the measurement at the seat stays with the wheel centred in the chain stays. The wheel is 4mm closer to the drive side chain stay. – tweedi May 03 '22 at 22:28

2 Answers2

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Let's talk about the wheel alone first. If you measured the distance to the stack of coins to be 8mm, then the wheel is out of dish by 4mm, i.e 4mm away from the center line. In other words, you would need to tighten the non drive side spokes just enough for the rim to move 4mm towards the NDS, relative to the hub. Then the dish will be even on both sides.

But 4mm is a small amount, you would not notice it when riding the bike. If the wheel is otherwise true and well tensioned, I wouldn't even bother to correct that small dish offset. Especially if it's an old wheel, the risk of nipples breaking if you fiddle with them too much is increased, and you may end up doing more harm than good.

Now, when you mount the wheel. You notice the offset is different than the one you measured on the wheel alone, and more so, different when measured at the chain stays compared to seat stays. There are several possible causes for this:

  • The wheel is crazy out of true, and the measurements you do are inconsistent, depending on which part of the untrue wheel you do the measurements on;
  • The dropouts are bent. This video demonstrates how to check for dropout alignment. I would be very cautios with trying to bend them back. You may try only with steel. But again, you may end up doing more harm than good.
  • The entire frame is bent, which you already tested for with the string, and found a little misalignment. Again, it is very small, and I wouldn't even try to correct it, given the risk that comes with doing that, i.e material fatigue and cracks.
Robert
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the reason is you put 130mm axle length to origninal 135 length rear chainstay,which cause the 8mm off center when you balance it on this bike,something like AI offset frame.

Christine Gull
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  • But when mounted it doesn't actually appear to be 8mm off, and it's only off with respect to the seat stays? – DavidW Jun 13 '22 at 10:58
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    If centered between seat stays, it is offset between chain stays. And vice versa. If centered between chain stays, they I will get the wheel offset between the seat stays .. I think that frame has been bent somehow. I never figured how to address this. So I keep riding it like this, as a 130 mm, makes no difference when hands are on the handlebar. – tweedi Jun 13 '22 at 22:35