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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 01-13-05, 09:09 AM   #1
ofofhy
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Chainline and Re-dishing: How much is too much?

I searched the forums, and I didn't find anything that really answered my question. I have been working on a '74 - '75 Fuji "Special Road Racer" (S-10-S type) for a SS conversion. It came with Sugino Maxy cotterless cranks that have a cool '70's look to them. I wanted to keep them, but they had a press fit large chain ring (50T). There is really insignificant wear on the teeth, so it should work. I took off the 39T ring, and I flipped the spindle over to bring the large chainring closer to the chainstay. I am still about 1/4" to 1/2" off in chainline (the hub would need to move towards the drive side) with the BMX freewheel threaded all the way onto the hub. Is this an achievable distance to make-up with freewheel spacers and re-dishing the wheel? What is the maximum for re-dishing a wheel?
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Old 01-13-05, 09:21 AM   #2
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when i've redished old road wheels for single speed use i just try to get the rim centered over the hub. once the hub is centered try respacing the axle evenly and then check your chainline.
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Old 01-13-05, 09:25 AM   #3
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Have you already dished the wheel? If the hub chainline needs to move outward on the drive-side, you need to remove spacers on the drive-side and added them to the non-drive-side. You really need better measurements, 1/4" to 1/2" is a huge range in terms of chainline.
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Old 01-13-05, 09:29 AM   #4
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Quote:
Originally Posted by ofofhy
I am still about 1/4" to 1/2" off in chainline (the hub would need to move towards the drive side) with the BMX freewheel threaded all the way onto the hub. Is this an achievable distance to make-up with freewheel spacers and re-dishing the wheel? What is the maximum for re-dishing a wheel?
The rim needs to be centered over the locknuts, not the hub. If you center it over the hub, it could be off center in the frame.

Assuming you are using the original hub that came with the bike, you should be able to respace the hub by removing spacers from the freewheel side and putting them on the non-freewheel side to adjust the position of the hub in the frame and achieve optimum chainline. Then you can re-dish the wheel and center it over the new locknut spacing.
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Old 01-13-05, 10:39 AM   #5
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Quote:
Originally Posted by don d.
The rim needs to be centered over the locknuts, not the hub. If you center it over the hub, it could be off center in the frame.

Assuming you are using the original hub that came with the bike, you should be able to respace the hub by removing spacers from the freewheel side and putting them on the non-freewheel side to adjust the position of the hub in the frame and achieve optimum chainline. Then you can re-dish the wheel and center it over the new locknut spacing.
This is a new wheelset, the old one was all steel and rusted. I haven't taken really accurate measurements, but it is within that 1/4" to 1/2" range. I am confident that with hub spacers, and a spacer on the threaded freewheel, I can get a good chainline. Right now, the rim is centered on the hub and the frame. I guess my question is, what is a reasonable maximum for moving the centerline on the rim with respect to the center of the hub?
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Old 01-13-05, 11:30 AM   #6
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Quote:
Originally Posted by ofofhy
This is a new wheelset, the old one was all steel and rusted. I haven't taken really accurate measurements, but it is within that 1/4" to 1/2" range. I am confident that with hub spacers, and a spacer on the threaded freewheel, I can get a good chainline. Right now, the rim is centered on the hub and the frame. I guess my question is, what is a reasonable maximum for moving the centerline on the rim with respect to the center of the hub?
I am confused. If anything, I think you'll only be moving CLOSER toward center (aligning the center of the hub with the center of the rim). I know that is not precisely the goal, but I mean it's not like you'll be dishing it AWAY from center/alignment. So the "maximum" of which you speak is only toward ideal...that is, toward center alignment. Sweet- I think I just confused myself and everyone else even more.
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Old 01-13-05, 01:22 PM   #7
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Ideally you would be moving closer to the center of the hub, except if the crank chainline is way far out and you can't/won't move the crank in. In that case, you need to move the hub chainline out to line up with the crank.
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Old 01-13-05, 01:40 PM   #8
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Quote:
Originally Posted by ofofhy
This is a new wheelset, the old one was all steel and rusted. I haven't taken really accurate measurements, but it is within that 1/4" to 1/2" range. I am confident that with hub spacers, and a spacer on the threaded freewheel, I can get a good chainline. Right now, the rim is centered on the hub and the frame. I guess my question is, what is a reasonable maximum for moving the centerline on the rim with respect to the center of the hub?
What kind of hub is it, a fixed gear hub, a cassette hub, a bmx hub, or a hub threaded for a freewheel? This makes a difference.

And forget about centering the rim on the hub. Rims are centered on the axle locknuts. You must center the rim on the locknuts for it to be centered in the frame.
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Old 01-13-05, 01:46 PM   #9
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how about starting with a shorter BB spindle?
1/2 inch chainline difference is TONS.
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Old 01-13-05, 01:47 PM   #10
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just an aside.... would you guys consider sheldon's dishing/truing guide to be pretty reliable? any better ones out there?
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Old 01-13-05, 02:12 PM   #11
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Quote:
Originally Posted by ofofhy
...I am still about 1/4" to 1/2" off in chainline (the hub would need to move towards the drive side) with the BMX freewheel threaded all the way onto the hub.
First things first....Are you certain that your 30 year old frame is straight? If you haven't checked it (or had it checked) you might want to. I was able to convert a 70's Univega with a road hub and bmx freewheel by simply flipping the BB spindle .... once the frame was straightened.

Jim
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Old 01-13-05, 02:23 PM   #12
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I've seen on road wheels the wheel dished enough that the rim is maybe an inch off being centered on the drive side flange. I guess the danger is that you could end up with all significant tension on one flange, which could be bad for a number of reasons. maybe. anyway. Also, too much dish can be bad for non- drive side spokes. read this:
http://www.sheldonbrown.com/wheelbuild.html
particularly (scroll down) the section titled 'half radial spoking'.

but this is not going to be an issue for you. there's no way you're going to end up with this much dish.

First, you need to get your chainline right. use all the afore mention methods. then move your rim over. Unless you have an unusually narrow hub you'd end up hitting the seat stay long before you dangerously overdished the wheel to the left.

good luck
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Old 01-13-05, 02:24 PM   #13
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You should be fine using spacers and redishing. A 1/2 inch is not a large movement for redishing. Your chain line should be under 1/4 inch off to avoid issue. The largest draw back to respacing and redishing is the loss of the flip/flopability of the hub. But if that is not a concern then go for it. You said that you used a BMX hub, if memory serves the spacing is 110. Your bike is probably 126-130 spaced. If this is the case then you should need to respace and redish (again the is largely dependant on the frame). I did this with my suzue basic (110 spaced) on a 130 spaced bike without issue. I can't flip or flop, but I wouldn't anyway.
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Old 01-13-05, 02:52 PM   #14
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Quote:
Originally Posted by Cynikal
The largest draw back to respacing and redishing is the loss of the flip/flopability of the hub. But if that is not a concern then go for it. You said that you used a BMX hub, if memory serves the spacing is 110.
No, it is a road hub that matches the rear spacng, with a threaded freewheel. The BMX sprocket is threaded onto the hub. Flip/flop is not a concern since I only run SS.

The frame is straight (I checked that first), and the large chainring is within 5 mm of the chainstay w/the flipped BB spindle. That is the closest that I feel comfortable going.

So, it sounds like re-dishing is a doable option. Doable by me? Not without some help from the local co-op.
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Old 01-13-05, 03:43 PM   #15
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Sounds like you are on the right track. Sorry for the mis-read. i tend to scan quickly at work
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Old 01-13-05, 06:40 PM   #16
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Originally Posted by ofofhy
No, it is a road hub that matches the rear spacng, with a threaded freewheel....So, it sounds like re-dishing is a doable option.
If it's a road hub, respacing the axle and re-dishing will work and will actually make the wheel stronger.
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Old 01-13-05, 08:21 PM   #17
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you should go ahead and move the rim yourself. you can do it on a frame without too much trouble so long as you can work on it comfortable and have a reasonable attention to detail. So long as the wheel is true already it's mostly a matter of (evenly) loostening the drive side spokes and tigtening the non drive side. hints;

hit the nipples with some sort of penetrating oil the day before.

relax, put on some music and don't answer the phone while you're doing this

remove chain and derailer hanger (if it's an old bike). mount the wheel all the way to the back of the dropouts. check if they're even by reversing the wheel and seeing if the wheel ends up in the same place with relation to the seatstays (or brake mount).

adjust all the spokes on one side, then all the spokes on the other side, repeat. do this in small increments that are easy to quantify (full turn, half turn, etc.) check spoke tensions to make sure your not tightening or loostening too much.

always start and finish each incremental adjustment at the valve hole for continuity.

make sure your adjusting the nipple the right direction - if you're using a spoke wrench you'll be turning the nip right to loosten and left to tension. reverse this if your adjusting from the rim side (much easier) with a screwdriver.

measure off the seat stays to check your progress center wheel on the frame.

spin the wheel (fast) and use a pencil steadied against the seat stay to mark wobbles in the rim.

if you end up with a big wow and can't figure out how to address it then you might have been right about taking it to the lbs and you can do so at this time. but remember, no one likes a quitter.

this isn't rocket science and you're not building a rocket. you're not even building a bike for the track. this is a beater! you can get it close enough.
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