Steel fork aligns rim slightly off-center
#1
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Steel fork aligns rim slightly off-center
I've built up a 1981 Nishiki International as an allroad bike. (Traditional-diameter butted steel tubing, long wheelbase, 60.5mm top tube for my tallness, 36mm trail with 38mm tires. And looks fairly vintage apart from indexed barcons, aero brake levers, and charge saddle.
But what I'm here to ask about: the front rim is 2.2mm closer to the left (non-drive) fork blade, which means that the rim is 1.1mm off centerline. Newly-built, perfectly-dished rim, and I flipped it around to measure both ways to make sure dish wasn't causing the difference. Dropouts spaced at 100mm; which may or may not be original (not sure what Japanese nicer road bikes were running back then). See attached photos.
My questions are:
a) is this something that can affect the steering? (74mm head angle, about 36mm trail). I can ride no-hands fine without having to lean the bike
b) is there any easy fix here? I'm annoyed that the rim is off-center, which means I need to rotate the centerpull brakes slightly and the pad contact angles aren't the same on each side. I'd rather not get into bending-by-framebuilder territory.
But what I'm here to ask about: the front rim is 2.2mm closer to the left (non-drive) fork blade, which means that the rim is 1.1mm off centerline. Newly-built, perfectly-dished rim, and I flipped it around to measure both ways to make sure dish wasn't causing the difference. Dropouts spaced at 100mm; which may or may not be original (not sure what Japanese nicer road bikes were running back then). See attached photos.
My questions are:
a) is this something that can affect the steering? (74mm head angle, about 36mm trail). I can ride no-hands fine without having to lean the bike
b) is there any easy fix here? I'm annoyed that the rim is off-center, which means I need to rotate the centerpull brakes slightly and the pad contact angles aren't the same on each side. I'd rather not get into bending-by-framebuilder territory.
#2
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Two things could be wrong here:
1. One of the fork blades is longer than the other - or the dropout on one side isn't as set into the fork blade as the other.
2. One of the fork blades has less rake than the other.
3. The dropout won't allow the axle to bottom out against the dropout.
It's tough to fix issue 1 without a torch.
1 or 2 can be fixed with adding a bit of rake to one side - the side that the wheel is "leaning" towards.
Issue 3 can be fixed with some careful filing using a rat tail file of "close to" the same radius as the axle.
I've corrected several forks with this issue, but it may take specialized tools. A framebuilder should be able to do the same.
Since it's not affecting your steering appreciably, the biggest issue is getting the brake centered. For the small amount you're showing, maybe you just live with it. If you're a perfectionist, it's correctable.
1. One of the fork blades is longer than the other - or the dropout on one side isn't as set into the fork blade as the other.
2. One of the fork blades has less rake than the other.
3. The dropout won't allow the axle to bottom out against the dropout.
It's tough to fix issue 1 without a torch.
1 or 2 can be fixed with adding a bit of rake to one side - the side that the wheel is "leaning" towards.
Issue 3 can be fixed with some careful filing using a rat tail file of "close to" the same radius as the axle.
I've corrected several forks with this issue, but it may take specialized tools. A framebuilder should be able to do the same.
Since it's not affecting your steering appreciably, the biggest issue is getting the brake centered. For the small amount you're showing, maybe you just live with it. If you're a perfectionist, it's correctable.
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I have this issue with my Miyata. I just move the rim over a little with my thumb before tightening the quick release and presto, it's centered.
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Ain't broke, don't fix.
If you can say you can ride no handed, I assume you'd noticed any tendencies for the bike to stray off the intended line as well.
Seems like this is something you want to fix rather than something you'd actually need to fix.
The "real" way to sort this out would be to measure the fork first.
Easiest done pulling the fork and placing it on a flat-enough reference surface. Most likely the fork legs are either pushed off to one side a little, or at different lengths.
If the legs are off to one side, then the fork should be cold-set until centered.
Sounds scary, but is generally quite doable w/o anything bad happening from it.
If leg length is off you can take a rat tail file to the tall dropout and make it deeper.
Go slow and test fit often, it doesn't take much.
Or you can build up the short leg a little.
I prefer to cut short, thin strips of sheet metal, bend them into shallow U shapes and stick them at the bottom of the dropout.
Once happy with alignment, use the metal-compatible glue of you choice to keep them in place when the wheel is out.
I wouldn't undo an inserted dropout from the fork leg unless it's so way off that it's visually obvious compared to the taper of the leg etc.
If you can say you can ride no handed, I assume you'd noticed any tendencies for the bike to stray off the intended line as well.
Seems like this is something you want to fix rather than something you'd actually need to fix.
The "real" way to sort this out would be to measure the fork first.
Easiest done pulling the fork and placing it on a flat-enough reference surface. Most likely the fork legs are either pushed off to one side a little, or at different lengths.
If the legs are off to one side, then the fork should be cold-set until centered.
Sounds scary, but is generally quite doable w/o anything bad happening from it.
If leg length is off you can take a rat tail file to the tall dropout and make it deeper.
Go slow and test fit often, it doesn't take much.
Or you can build up the short leg a little.
I prefer to cut short, thin strips of sheet metal, bend them into shallow U shapes and stick them at the bottom of the dropout.
Once happy with alignment, use the metal-compatible glue of you choice to keep them in place when the wheel is out.
I wouldn't undo an inserted dropout from the fork leg unless it's so way off that it's visually obvious compared to the taper of the leg etc.
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If the centering of the wheel is really your primary concern and you don't want to go the frame builder route, how about adding a washer between the wheel and the fork on the right side (view of your picture) to make it center better.
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#6
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I'd go this route, it's the simplest fix for you. You're only dealing with 1.1mm at the rim face, which is miniscule, so what you'll take off at the dropout is about 50/311 of that, or around .1768 mm, fairly close to nothing. Shouldn't take more than a couple minutes.
#7
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Can’t even imagine why taking this to a builder is a fate worse than death. Have you tried taking it to a mechanic? Forks bend all the time. Mechanics straighten forks every day. Yes, your frame rides better when straight. Alignment is normal maintenance.
Don’t go removing metal before you even have a diagnosis.
Don’t go removing metal before you even have a diagnosis.
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Thanks for all the feedback. This is helpful for me to think through causes, solutions, and whether a solution is needed.
The bike doesn't feel great no-hands, but I'm not leaning it to one side to maintain a straight line as I am with another bike I picked up used.
The seller included the original wheelset, and I will check the spacing on the front wheel to see if it was 100mm (which would give me an idea of whether the fork spacing was manually spread).
Most mechanics nowadays don't have experience cold-setting a steel fork. 20 years ago I'd have had more luck on that issue.
I'll likely do a slight bit of filing on the underside of the longer fork dropout. It's even possible that paint chipped off on one side and not the other, which could account for the slight difference.
The bike doesn't feel great no-hands, but I'm not leaning it to one side to maintain a straight line as I am with another bike I picked up used.
The seller included the original wheelset, and I will check the spacing on the front wheel to see if it was 100mm (which would give me an idea of whether the fork spacing was manually spread).
Most mechanics nowadays don't have experience cold-setting a steel fork. 20 years ago I'd have had more luck on that issue.
I'll likely do a slight bit of filing on the underside of the longer fork dropout. It's even possible that paint chipped off on one side and not the other, which could account for the slight difference.
#9
What??? Only 2 wheels?
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Take it to a good frame builder, let him straighten it and if necessary make the DO have identical vertical surface heights. Pay the man or woman the $20 or $40 or whatever he or she asks, go ride away.
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I'd love to do this. But I don't know that there's "a good [neighborhood] frame builder" in my area. How does one go about finding one?
#11
What??? Only 2 wheels?
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A google search shows some decent shops. Call them. Consider shipping the fork somewhere. Or ask one o the custom motorcycle shops. Google shows several.
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I just dished the wheel to match the fork on my old bike. But, I now have the Park alignment tool, so I'll pull everything apart, maybe this winter, and touch up the fork alignment, and fix the wheel, and also work on the headset.
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If there were a bicycle framebuilder nearby that I could bring it to, I'd definitely go there. And I'd love a quick $20-40 fix. But my experience looking for service on older steel frames leads me to think this is pretty rare (around here, at least) nowadays.
Tell me more about how you think a motorcycle shop could be helpful here.
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I just noticed the same on one of my best bikes. Rode it just now and it is riding perfectly (with or without hands) so it is hardly an issue, but still ... My thought is that I will take the fork off and lay the steerer on 3 hardwood 1 inch planks, fork on its side, and measure down from the dropout to the table under, rotate the fork 180 degrees and repeat. If these differ, I will coldset the blades a touch. If they are the same I will dress the dropout on the side the rim is on a touch. That fork is due to be repainted, so I will address this at that point.
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Thanks for all the feedback. This is helpful for me to think through causes, solutions, and whether a solution is needed.
The bike doesn't feel great no-hands, but I'm not leaning it to one side to maintain a straight line as I am with another bike I picked up used.
The seller included the original wheelset, and I will check the spacing on the front wheel to see if it was 100mm (which would give me an idea of whether the fork spacing was manually spread).
Most mechanics nowadays don't have experience cold-setting a steel fork. 20 years ago I'd have had more luck on that issue.
I'll likely do a slight bit of filing on the underside of the longer fork dropout. It's even possible that paint chipped off on one side and not the other, which could account for the slight difference.
The bike doesn't feel great no-hands, but I'm not leaning it to one side to maintain a straight line as I am with another bike I picked up used.
The seller included the original wheelset, and I will check the spacing on the front wheel to see if it was 100mm (which would give me an idea of whether the fork spacing was manually spread).
Most mechanics nowadays don't have experience cold-setting a steel fork. 20 years ago I'd have had more luck on that issue.
I'll likely do a slight bit of filing on the underside of the longer fork dropout. It's even possible that paint chipped off on one side and not the other, which could account for the slight difference.
#17
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we used to use the park fork alignment gauge and the big park bending lever all the time when I was a mechanic. There is something satisfying about getting a fork back the way it should be. I wouldn't start filing on dropouts until it's clear what's wrong, and the park gauge is the way to start.
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From the first post:
Newly-built, perfectly-dished rim, and I flipped it around to measure both ways to make sure dish wasn't causing the difference.
#19
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If the fork is bent and the dropout is filed to make the wheel approximately center, the fork is still bent. The bike might ride better, it won’t ride like a straight bike. Getting a final fix on the fork will be harder.
The best guy to do this repair is someone who does it all the time. An LBS mechanic who services bikes for commuters every day. You could buy a complete set of your own shop tools and fixtures but if you are not using them daily you won’t get results as good as a shop mechanic gets. Granted it may be hard to find the mechanic being described. If you can find him it will be worth the trouble.
The best guy to do this repair is someone who does it all the time. An LBS mechanic who services bikes for commuters every day. You could buy a complete set of your own shop tools and fixtures but if you are not using them daily you won’t get results as good as a shop mechanic gets. Granted it may be hard to find the mechanic being described. If you can find him it will be worth the trouble.
#20
What??? Only 2 wheels?
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Of course one shouldn't just file a DO. The real question is, in what way it is malformed, and how badly? I guess that's two questions, isn't in? Oops, now it's three.
If you attach a bolt to the inside of each DO you may find that the fork arm ends aren't aligned to each other, or that they just aren't even parallel to each other, or that they are nicely parallel and aligned but just skewed to one side or the other, or just one is skewed and the spacing between them ins't the standard 100mm. Inotherwords, they can be malformed lots of different way. But once they are aligned properly a good frame builder may still conclude that the inside surfaces on which the axle rests may not be the exact same distance from the ground or fork crown. That's when she/he may decide to do some filing.
If you attach a bolt to the inside of each DO you may find that the fork arm ends aren't aligned to each other, or that they just aren't even parallel to each other, or that they are nicely parallel and aligned but just skewed to one side or the other, or just one is skewed and the spacing between them ins't the standard 100mm. Inotherwords, they can be malformed lots of different way. But once they are aligned properly a good frame builder may still conclude that the inside surfaces on which the axle rests may not be the exact same distance from the ground or fork crown. That's when she/he may decide to do some filing.
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#21
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What I actually do in such cases is what davester did, simply tilt the wheel before clamping the quick-release lever, so the wheel is centered under the crown.
Then an evaluation ride will inform as to whether the bike rides straight no-handed or not.
The tendency to pull to one side is from the front tire's contact patch being off-center toward the opposite side.
So be aware that moving the contact patch toward the left will tend to assist the steering toward the right, and vice-versa.
So this becomes an iterative process of moving the contact patch by means of tilting the wheel (as by the previous test or as by filing a dropout slot deeper) and of moving the contact patch by means of bending both fork legs toward one side or the other.
I actually go through this whole process often with used bikes, but I save any dropout filing for last, since metal removed cannot easily be put back.
And did I mention (no, I didn't) that the above two corrective methods for moving the contact patch this way and that have opposite effects from one another on the centering of the tire under the fork crown, so a bit of testing and planning (as well as making the headset perfectly free-moving) should definitely precede any bending of the fork legs or filing of a dropout slot!
There are also cases where a bent steer tube or main frame can cause the steering to pull, in which case loading might best be applied through the fork with the front wheel installed to prevent the bending stress from being localized in either fork blade. I've straightened bikes this way in the field, literally jumping on the bike with one foot on the front axle, one foot on the seatpost and one hand holding the handlebar perpendicular to the ground (and it worked).
But no such field remedies will assure the bike's owner of absolute alignment the way that a stripped frameset can be evaluated and aligned in a frame shop, where firstly the bottom bracket will be secured in plane with the table or fixture and where a fork can be perfectly centered up. The bikes I work on and ride don't need that level of accuracy however, and may never have had it in the first place.
Then an evaluation ride will inform as to whether the bike rides straight no-handed or not.
The tendency to pull to one side is from the front tire's contact patch being off-center toward the opposite side.
So be aware that moving the contact patch toward the left will tend to assist the steering toward the right, and vice-versa.
So this becomes an iterative process of moving the contact patch by means of tilting the wheel (as by the previous test or as by filing a dropout slot deeper) and of moving the contact patch by means of bending both fork legs toward one side or the other.
I actually go through this whole process often with used bikes, but I save any dropout filing for last, since metal removed cannot easily be put back.
And did I mention (no, I didn't) that the above two corrective methods for moving the contact patch this way and that have opposite effects from one another on the centering of the tire under the fork crown, so a bit of testing and planning (as well as making the headset perfectly free-moving) should definitely precede any bending of the fork legs or filing of a dropout slot!
There are also cases where a bent steer tube or main frame can cause the steering to pull, in which case loading might best be applied through the fork with the front wheel installed to prevent the bending stress from being localized in either fork blade. I've straightened bikes this way in the field, literally jumping on the bike with one foot on the front axle, one foot on the seatpost and one hand holding the handlebar perpendicular to the ground (and it worked).
But no such field remedies will assure the bike's owner of absolute alignment the way that a stripped frameset can be evaluated and aligned in a frame shop, where firstly the bottom bracket will be secured in plane with the table or fixture and where a fork can be perfectly centered up. The bikes I work on and ride don't need that level of accuracy however, and may never have had it in the first place.
Last edited by dddd; 11-17-18 at 12:06 AM.
#22
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Finding a shop
I had a similar problem and visited shops w/o the fork and asked questions. Shop 3 had a cast iron table used to assess condition and fixtures to build/adjust forks; also had a Marchetti frame table so had the frame straightened as well. The frame/fork are Reynolds 753R which the internet will tell you can't be cold set, less than $100 (6 years ago) and the bike now has thousands of miles and can be ridden around the block w/o hands.