New steel Fork ,wheel sits off center ,what tolerance acceptable?

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jimneycricket
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New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby jimneycricket » 2 Jan 2021, 9:02am

Hi there,

I picked up a new surly Disc trucker frame from Spa cycles to build up.

It has threaded through axles on each end.

I put the front wheel on yesterday and by eyeballing from the mudguard mount in the center of the fork down to the tire that it seemed the tire was off center a bit. I measured with my calipers the distance from the rim to the fork on each side and one side is closer to the fork than the other by a hair under 2mm. Wheel seems perfectly true. The rear wheel is sitting dead center in the frame.

I can adjust this 2mm out a bit by playing with how the wheel sits in the dropouts since on this frame the non threaded dropout is actually open like a regular QR setup,

I believe one benefit of a through axle was that every time you install the wheel its in the exact correct position each time so that the disc brakes don't rub , but I would now have to fiddle about a bit if I wanted the wheel dead center.I have had to play with how front wheels sit in the dropouts of my other steel bike in order to center it, but that bike was second hand and is older than myself.

Is this just par for the course with steel forks?Is this kind of tolerance acceptable and normal or would you be looking for Surly to replace the fork? After paying £650 for a frame should I expect Nasa engineering precision? It's my first new bike/frame so I honestly don't know. Would this off centering of the wheel effect the ride of the bike?

Your thoughts and experience appreciated,

J

reohn2
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby reohn2 » 2 Jan 2021, 9:15am

Have you tried as an experiment reversing the wheel in the fork?
If it's the same then it's the fork if it's different then its the wheel.
TBH whilst the wheel should be centered If it's the fork I'd adjust the wheel dish or leave it <2mm won't affect the ride quality or any safety issues.
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531colin
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby 531colin » 2 Jan 2021, 3:05pm

Image002 by 531colin, on Flickr

Image001 by 531colin, on Flickr

Those pictures show what you are aiming for at the front end of a bike. (thread here in "too good to lose" https://forum.cyclinguk.org/viewtopic.php?f=5&t=59332
You can see some red string under tension; the string is tied to the wheel rim at the bottom, and it passes over the hub and through the valve hole at the top, to be clamped at the handlebar clamp.
What you need to achieve is to have the front tyre contact patch in a direct line through the centre of the headset bearing. (viewed from front)
If either the fork or the wheel is wonky, this won't happen, and the contact patch doesn't have to be too far off to one side before the bike won't go straight no hands unless you have the saddle under one cheek.
Wonky forks generally means that one leg is effectively a tiny bit longer than the other one (although other faults are available)
A wonky wheel generally means the rim isn't accurately over the middle of the hub.
I haven't done much with thru' axles, so I don't know if you can always put the wheel in the forks the other way round (so the brake disc is the wrong side). But (as R2 says) if you can flip the wheel, do flip the wheel; if the rim is in the same place relative to the fork leg, its a wonky fork; if the rim is off-centre the other way round, then its a wonky wheel. If you can't flip the wheel then a working dishing stick can be made from a bit of wood and 3 screws.
I'm afraid I'm going to query with R2 here....
reohn2 wrote:........ whilst the wheel should be centered If it's the fork I'd adjust the wheel dish....

....Because if the fork is wonky and you re-dish the wheel to centre the wheel in the top of the forks, then you will move the contact patch the wrong way and make it worse.

So, first job, find out if its a wonky wheel or a wonky fork.
If its a wonky wheel, get the rim centred properly over the middle of the hub and all will be well.
If its a wonky fork and it can be corrected by filing the wheel SLOT a bit deeper, then I would do that. (Quicker cheaper and more satisfactory than messing about returning forks.)
If its a wonky fork and filing the wheel slot deeper would be going the wrong way, then you have to decide whether its worth worrying about at all.
Can you make up a packing piece that fits in the dropout so the wheel goes straight in with no faffing?
OTOH, its a very small error. If the difference in the rim distance from the fork legs is 2mm, then the tyre contact patch is likely to be 1mm away from where it should be. I'm not sure I would notice that. It might be instructive to ask Surly what their tolerance is for this dimension; I confess its not a dimension where I have ever seen a tolerance listed. (and if Surly don't have a tolerance then another fork may be no better than this one) There tends to be tolerance limits set on things like fork leg length, which may be +/- 1.5mm. Now if one fork leg is +1.5mm and the other is -1.5mm (3mm discrepancy between fork leg length) then the rim is going to be way out between the fork legs, and the contact patch will be way off as well. Maybe thats not what it means!
I know Spa do some checks on their own brand frames, which result in the occasional frame being rejected, however I don't know if they have a tolerance for rim centre between fork legs.

reohn2
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby reohn2 » 2 Jan 2021, 3:19pm

Colin
Perfect is perfect,however in this case less than 2mm is nowt is it?
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531colin
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby 531colin » 2 Jan 2021, 3:29pm

reohn2 wrote:Colin
Perfect is perfect,however in this case less than 2mm is nowt is it?

Its a 2mm discrepancy between rim to fork leg measurement left vs. right....which to me means the wheel is actually 1mm off centre.
So I don't think I would worry too much about that, apart from correcting it by filing the dropout slot, if thats possible in this case with thru' axles.

I'm not certain that I understand you right; but if the fork is wonky and you alter the wheel dish to get the rim central between the fork legs, then to move the rim to the right at the top you will also be moving it to the right at the bottom, when it actually needs to go the other way?

(Snowing like fun here, I can't remember what its like to actually go out on my bike!)

reohn2
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby reohn2 » 2 Jan 2021, 3:57pm

531colin wrote:
reohn2 wrote:Colin
Perfect is perfect,however in this case less than 2mm is nowt is it?

Its a 2mm discrepancy between rim to fork leg measurement left vs. right....which to me means the wheel is actually 1mm off centre.
So I don't think I would worry too much about that, apart from correcting it by filing the dropout slot, if thats possible in this case with thru' axles.

I'm not certain that I understand you right; but if the fork is wonky and you alter the wheel dish to get the rim central between the fork legs, then to move the rim to the right at the top you will also be moving it to the right at the bottom, when it actually needs to go the other way?

(Snowing like fun here, I can't remember what its like to actually go out on my bike!)

If one fork leg is shorter than the other it means the wheel sits at an angle in respect to the rear wheel.
However if one fork leg is splayed out further than the other,the wheel will be straight and perpendicular but offset to one side.

As you say in the first instance filing a dropout would bring a leaning wheel to be centred and perpendicular in relation to the rear wheel,but that doesn't apply with a through axle as one d/out is threaded with the other almost the exact through axle diameter and the d/outs have half round sockets on the inner face for the axle to sit into.

In the second instance with one fork leg being splayed out or in,further than the other,redishing the wheel by the amount of offset brings both wheels into line and perpendicular.
In the OP's case it's less than 2mm which I'm guessing half a turn of the spoke key slackening one side tighteng the other will take out less than 2mm fork leg discrepancy.

That is of course if it isn't a case of the wheel dish being almost 2mm off centre

Freezing cold and snowy here too,waayyy too cold for any kind of two wheeled fun :?
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jimneycricket
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby jimneycricket » 2 Jan 2021, 4:40pm

So I ran the wheel flipping experiment.

Unfortunately yes the gap is the same on the same side as before flipping wheel so it all points to the fork.

Filing is not an option here as one dropout is threaded and the other side needs the axle to sit less far into it if I were to try and manually align the wheel.

So...

As 531 Colin said would a new surly fork just be much more of the same if that is the kind of tolerance they work with , or is this fork genuinely a bit wonky coming out of the factory and worth going to the trouble of trying to get replaced.Maybe I should just ride it as is ,I'm unsure.

slowster
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby slowster » 2 Jan 2021, 4:59pm

jimneycricket wrote:As 531 Colin said would a new surly fork just be much more of the same if that is the kind of tolerance they work with , or is this fork genuinely a bit wonky coming out of the factory and worth going to the trouble of trying to get replaced.Maybe I should just ride it as is ,I'm unsure.

Why not just ask them?

https://surlybikes.com/contact

PH
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby PH » 2 Jan 2021, 5:18pm

jimneycricket wrote:As 531 Colin said would a new surly fork just be much more of the same if that is the kind of tolerance they work with , or is this fork genuinely a bit wonky coming out of the factory and worth going to the trouble of trying to get replaced.Maybe I should just ride it as is ,I'm unsure.

As you obviously have concerns, IMO the first step is to talk to the supplier. I certainly wouldn't ride it to then find out it is noticeable, the time to deal with it is sooner rather than later.
I returned an expensive item earlier this year for what the supplier considered an acceptable blemish, I won't go into detail because it was all resolved amicably, but I felt it was entirely my choice to reject it.

Valbrona
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby Valbrona » 2 Jan 2021, 10:40pm

When questioned about such issues manufacturers tend to use the term 'within acceptable standards'.

You could try your luck with a new fork.
I should coco.

Brucey
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby Brucey » 2 Jan 2021, 10:50pm

jimneycricket wrote: So I ran the wheel flipping experiment...... the gap is the same on the same side as before flipping wheel so it all points to the fork.

Filing is not an option here as one dropout is threaded and the other side needs the axle to sit less far into it if I were to try and manually align the wheel...



send it back.

Bad design, if you are going to make it like that. It is only about 0.3mm out at the dropouts, but it is 0.3mm the wrong way.

BTW it ought to be easy to fix this with a blob of weld metal and some dressing, but you shouldn't be having to do that with a new fork.

cheers
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531colin
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby 531colin » 2 Jan 2021, 11:26pm

I wonder if thru' axles are a solution looking for a problem.
I only have one bike running disc brakes, but the wheels go back in with no brake rubbing on normal Q/Rs. (I might have filed the odd dropout when setting the bike up, I really can't remember....its not an unusual thing for me to do.)
If 0.3mm discrepancy in fork length gives 1mm lateral displacement of the rim then to get the rim perfectly central the manufacturers are setting themselves quite a target.

Brucey
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby Brucey » 3 Jan 2021, 8:58am

the idea of through-axles is that both ends of the axle are accurately located, so that the wheel doesn't move around in the fork when the brake is applied. There are three problems with this in the case of the Surly design;

1) the TA premise is arguably fundamentally flawed; even when the design is implemented properly there is usually enough radial clearance on the LH bore to allow the axle to 'orbit' slightly (between braking and riding normally). This may cause the TA to loosen; it certainly causes the hub inner parts to precess and folk with hub generators have discovered that the wires tend to get torn off TA hub generators because of this.

2) As conceived TA fittings are designed to either be jig-built with minimal distortion or to be finish-machined in situ. Obviously when made to a price you will get parts that have not been finish machined and are not made with sufficiently low distortion either. Possibly the distortion seen in the OPs forks is endemic; there is less mass in the LH dropout vs the RH one and this has implications for distortion; the jig could be perfect but one leg may always tend to shrink more than the other unless the differing temperature distributions of each leg (during welding) are allowed for.

3) cutting a slot in the LH dropout as Surly have done arguably compromises the whole TA concept anyway. When the brake is applied hard, the axle is busy trying to tear itself out of the bottom of the LH dropout, and that is exactly where they have cut the slot. Duh.

FWIW folk that put TAs through British winters can find another problem, which is that the TA tends to seize up. Considering this design has only been used for a few years on mass-produced bikes the number that have had to be cut out is not very encouraging.

cheers
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iandusud
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby iandusud » 3 Jan 2021, 9:12am

PH wrote:
jimneycricket wrote:As 531 Colin said would a new surly fork just be much more of the same if that is the kind of tolerance they work with , or is this fork genuinely a bit wonky coming out of the factory and worth going to the trouble of trying to get replaced.Maybe I should just ride it as is ,I'm unsure.

As you obviously have concerns, IMO the first step is to talk to the supplier. I certainly wouldn't ride it to then find out it is noticeable, the time to deal with it is sooner rather than later.
I returned an expensive item earlier this year for what the supplier considered an acceptable blemish, I won't go into detail because it was all resolved amicably, but I felt it was entirely my choice to reject it.

^This. Spa Cycles is a reputable dealer and I'm sure that they would want you to contact them first and foremost with anything that you are not happy about with regards to your purchase. Apart from anything else, legally it is with them that you should be dealing and not Surley.

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531colin
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Re: New steel Fork ,wheel sits off center ,what tolerance acceptable?

Postby 531colin » 3 Jan 2021, 10:01am

Finish machining in situ....yeah, I hadn't thought about that, that could work? Needs a bigger jig than the facing cutters for ISO caliper mounts, though. I suppose if somebody wanted to do it properly, you could at the same time cut a conical seat for the non-threaded end of the through bolt (or the axle end) to prevent that end moving about. But that would require frame manufacturers to talk to cycle parts manufacturers, I'll not hold my breath.
Just looking at the pictures on Surly website; the threaded end of the thru' axle is the end where the brake isn't.....why would you do that?
Isn't it the brake end which you need to stop moving around?