Frame misalignment and wheel dish
knuckleberryfinn
Posts: 33
Apologies for the length of this query: you might want to stop reading now.
I am building up a Ron Cooper steel frame and was surprised to find, when transfering my (handbuilt) wheels from another bike, that the rear rim was substantially off-centre, both between the seatstays and the chainstays. I did not measure this off-centredness, but am guessing it was around 5mm to left of centre (though this of course looks like (is) more than it sounds).
My diagnosis was that either:
(1) The dish on the wheel (following my earlier replacement of all damaged drive-side spokes with outside-facing elbows - another story) was not pronounced enough, and that I hadn't noticed this with my other bike because it has traditional slotted drop-outs (without adjusters) whereas the Cooper has vertical drops.
Or (2) The frame is misaligned through poor building (unlikely: it's a Ron Cooper) or because it's taken a knock.
I measured the alignment of the rear end of the frame this morning by placing a true front wheel in the rear dropouts, lining the rim up with the brake mount, and then measuring the distance between the inside edge of the dropouts and the outside edge of the spacers (is that what they are called?) around the axle at either side of the hub. From this measurement it would appear that the problem is a combination of (1) and (2), though not seriously so: the rear end seems to be misaligned towards the non-drive side by between 1 and 2mm. (Centre to non-drive dropout=66-67mm; centre to drive-side dropout=63-64mm).
So, finally, here are some questions:
a) Can I improve on this method of measuring frame alignment without an armoury of specialist tools and devices?
b) Assuming the alignment measurement is accurate, is around 1.5mm a problem?
c) Specifically, is this going to cause problems with my wheels? I.e. will the non-drive spokes be under insufficient tension to keep them securely tensioned, and equally, will the drive-side be too tight? Before measuring the frame alignment I tried to re-dish the wheel: nearly made it, but I need to replace the drive-side spokes as, with this dish, they are too long. However, the drive-side was at an incredibly high tension, though the non-drive side was not overly slack.
I would be very grateful for any advice or comments - I am dying to get this bike on the road.
I am building up a Ron Cooper steel frame and was surprised to find, when transfering my (handbuilt) wheels from another bike, that the rear rim was substantially off-centre, both between the seatstays and the chainstays. I did not measure this off-centredness, but am guessing it was around 5mm to left of centre (though this of course looks like (is) more than it sounds).
My diagnosis was that either:
(1) The dish on the wheel (following my earlier replacement of all damaged drive-side spokes with outside-facing elbows - another story) was not pronounced enough, and that I hadn't noticed this with my other bike because it has traditional slotted drop-outs (without adjusters) whereas the Cooper has vertical drops.
Or (2) The frame is misaligned through poor building (unlikely: it's a Ron Cooper) or because it's taken a knock.
I measured the alignment of the rear end of the frame this morning by placing a true front wheel in the rear dropouts, lining the rim up with the brake mount, and then measuring the distance between the inside edge of the dropouts and the outside edge of the spacers (is that what they are called?) around the axle at either side of the hub. From this measurement it would appear that the problem is a combination of (1) and (2), though not seriously so: the rear end seems to be misaligned towards the non-drive side by between 1 and 2mm. (Centre to non-drive dropout=66-67mm; centre to drive-side dropout=63-64mm).
So, finally, here are some questions:
a) Can I improve on this method of measuring frame alignment without an armoury of specialist tools and devices?
b) Assuming the alignment measurement is accurate, is around 1.5mm a problem?
c) Specifically, is this going to cause problems with my wheels? I.e. will the non-drive spokes be under insufficient tension to keep them securely tensioned, and equally, will the drive-side be too tight? Before measuring the frame alignment I tried to re-dish the wheel: nearly made it, but I need to replace the drive-side spokes as, with this dish, they are too long. However, the drive-side was at an incredibly high tension, though the non-drive side was not overly slack.
I would be very grateful for any advice or comments - I am dying to get this bike on the road.
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Comments
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Borrow a friend's rear wheel.
Cyclist, public transport passenger, pedestrian, driver, motorcyclist.
I get on OK with myself, so why can't we all get on with each other?0 -
Try fitting the problem wheel the wrong way round - if it's now wonky in the other direction, it's to do with the wheel or if the rim is still offset to the same side, it's frame alignment i.e. wheel is correctly dished.0
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Cheers Alan and Monty Dog - I will give these a go this afternoon.
Assuming the frame is misaligned up to 2mm, what would people recommend? The idea of cold setting the frame doesn't excite me very much, I must say...0 -
2mm is within manufacturers tolerance - you could take it to an experienced framebuilder to 'tweak' it into position or just learn to live with it0
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You can also check frame alignment using string thtough the dropouts and around the headtube. Then measure distance between string and seat tube on both sides. Check sheldon brown for a more thorough explanation.0
