Wheel Dishing Dilemma

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Manc33
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Wheel Dishing Dilemma

Post by Manc33 »

I got a wheel with a hub motor that has drive side spokes a little under tensioned (maybe 1 full turn) and non-drive side spokes considerably under tensioned (maybe 2 or 3 full turns). Typical factory built wheel!

I put my dishing tool on it and the dilemma is, the rim would be centered if I tightened the drive side spokes only - which might (almost) tighten them to spec, but that leaves the non-drive side spokes untouched and still too loose.

Perhaps one solution could be to get all spokes at the right tension, ignoring dish entirely, then just center the rim by using spacers?

This will of course be prizing my dropouts apart even more than they already are, which I don't want to do (aluminium), plus I'm not sure if this is even solving the dishing problem anyway, although the rim would in theory be central on the bike, it would still be offset to itself, if that makes sense.

I think some of the problem is, I am having to use two thick spacers on the drive side, because of the cassette lockring having to clear the dropout. I noticed on my usual bike the gap there is about 5mm so I want to keep that the same on the new setup.

I don't know what to do, risk making the drive side spokes arguably too tight (just so the non-drive side spokes are tight enough) and have it dished properly - or just add spacers.
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mattsccm
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Re: Wheel Dishing Dilemma

Post by mattsccm »

Whilst a correct wheel build would be great I wouldn't ignore the odd washer if that helps. In the past I have done that to use a good wheel in a bike it wasn't made for.
What is the frame made of? Steel will spring a bit with no damage.
Qr or nut axle? You don't need a lot of axle in the dropouts if the former. If a problem shove another, longer, axle in.
Gap by the right drop out only needs to be enough for the lock nut and chain to miss the frame. Back when we squeezed a 6 speed block into a frame built for 5 the chain would often touch. If the intial ride that told you this didn't wear enough away a few strokes with a file did.
hemo
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Re: Wheel Dishing Dilemma

Post by hemo »

Initially I will get the motor wheel trued to a good standard in my diy truing stand, then do all the final trueing/tensioning once in the drop out's.
I have never used a dishing tool and have simply trued and dished several rear hubs in the bikes drop outs, tension the wheel then dish it accordingly to get it centralised. One will find the non drive side will be slightly under tensioned but not to the extend of 2 or 3 nipple rotations unless of course the China supplier has supply incorrect spoke lengths, to which point the nipple will no longer tighten.


I have only had one issue with a motor wheel and this was a kit wheel supplied, after two or three issues I deconstructed the wheel bought a new rim and used a spoke calc to order new better Sapim's, relaced and trued the wheel has give no issues again.

I can't say in several bike frame builds that I have ever needed to use more then one extra washer over or above the Anti rotation washers/spacers supplied with motor kits.
Last edited by hemo on 18 Aug 2021, 10:55am, edited 1 time in total.
Mike Sales
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Re: Wheel Dishing Dilemma

Post by Mike Sales »

Manc33 wrote: 17 Aug 2021, 6:15pm

I put my dishing tool on it and the dilemma is, the rim would be centered if I tightened the drive side spokes only - which might (almost) tighten them to spec, but that leaves the non-drive side spokes untouched and still too loose.
I would try tightening the drive side spokes first.
Pulling the rim into its centred position will tighten the non-drive side spokes too.
This might be enough, but if not I would then tighten both sides, drive side most, to get them to ension, checking dish as I did so.
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NATURAL ANKLING
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Re: Wheel Dishing Dilemma

Post by NATURAL ANKLING »

Hi,
Some rear rims have no angle on the DS spokes?

Unless you have other information then the rim should be central about the axle locknuts?

Dishing will give very low sometimes too low spoke tension NDS to keep the wheel together without threadlock.
As others have said tightening the DS also tensions the NDS spokes unless you have very shallow DS spoke angle?

Recently did some work on a hub motor wheel..............all the spokes were loose, and by the very low miles say 50 miles out of the box, I can only assume they used out of work Halfords mechanics to build the things!

P.S. Does any one check wheel alignment after putting wheels back in after rebuild?
Like a straight edge down both sides of rear wheel to see it lines up with front wheel.
If it does not then the bike will handle like a whale.
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Manc33
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Re: Wheel Dishing Dilemma

Post by Manc33 »

Cheers guys. What I noticed is I had a washer or two going spare in the kit and if I use them equally on each side, it ends up with 1 thick (3.7mm) and 1 thin (1.5mm) washer at each side - that puts about a 4mm gap on the dishing tool on the DS, with no gap on the NDS.

The mistake I was making was leaving a thick washer off the NDS, but when I saw how much the thin one was bending, I knew it wasn't right! The reason I was trying to leave washers out was because I initially tried the wheel in a frame that's meant to be 135mm but was more like 131mm, so I was paranoid about having to stretch the dropouts on the frame I was going to use, when it wasn't the case trying it in the 2nd frame.

Now with the full set of washers on it, I have the reverse "problem", which actually isn't a problem because where the dishing gap is corresponds to the NDS needing to be tightened to correct it. :)

If the NDS spokes are tightened to correct the dish, then it's just a case of getting the DS spokes up to the right pitch/tension. I'll find the highest pitched DS spoke and see how far out it is and base it all on that.

It wasn't a dilemma in the end, just me assuming I don't need every washer when I do. :oops:
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Manc33
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Re: Wheel Dishing Dilemma

Post by Manc33 »

It's round, true... and the dish is within 1mm now. :mrgreen:

The NDS spokes still need to be tighter though.

The DS spokes are around 535 Hz when they should be 570 Hz, but I know this is a cheap rim so I'm not risking it just for another 1/8th of a turn. It's not these spokes I'm concerned about, they are tight enough, I can tell by feel.

The NDS spokes are still looser than they should be - they are pitched at around 465 Hz when they are meant to be at 560 Hz. This is a big difference (-20.4% Hz) compared to the DS spokes (-6.5% Hz).

Can't I "cheat" and just put a 2mm washer on the inside of the NDS dropout, then tighten the NDS spokes to get the rim 2mm over to the left - thus dishing it back to central and tightening the NDS spokes at the same time? Honestly they feel loose enough that even that won't fix it but it might at least add some longevity to the wheel

My dropouts would be getting prized open 2mm more, but if that let's me get the NDS spokes tighter, it's worth it, right?

The dropout isn't being stressed much at the moment. Let's just call this "ghetto dishing" :lol:
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NATURAL ANKLING
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Re: Wheel Dishing Dilemma

Post by NATURAL ANKLING »

Hi,
There's lots of things I would do and a few that I wouldn't.

As it's an electric bike front and rear wheels are set in stone once you've done the nuts up.
Have you applied a straight edge to the wheels/tires even, to see that the wheels are actually in line?
If you only have one straight edge, then fix the handlebars straight on, apply straight edge to one side of tires, then the other side, remember that whatever face you use of the straight edge should go against the tires on either side.
So flip the straight edge 180° as you go from one side to the other.
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Manc33
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Re: Wheel Dishing Dilemma

Post by Manc33 »

I've not got to the stage of having both wheels on the bike yet. Everything up to now was done with the Park Tool WAG-5 and a "Zeda" truing stand made in Japan like this one that's probably at least 30 years old.
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NATURAL ANKLING
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Re: Wheel Dishing Dilemma

Post by NATURAL ANKLING »

Hi,
Manc33 wrote: 18 Aug 2021, 8:20pm I've not got to the stage of having both wheels on the bike yet. Everything up to now was done with the Park Tool WAG-5 and a "Zeda" truing stand made in Japan like this one that's probably at least 30 years old.
There is no point getting the wheel millimetre perfect only to find that the wheels re 1/2 an inch out of line :)
Something worth checking on any bike.
If you find its out you could move the rim via spokes assuming its disc?
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Manc33
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Re: Wheel Dishing Dilemma

Post by Manc33 »

Yeah it's disc brake... but it's the disc causing a problem when I add spacers, because then the rotor isn't lined up with the pads anymore. I'm just going to get these, it's lucky I saw a post about them last night somewhere because it's too ingenious of a solution for me to ever think of it lol... https://www.wiggle.co.uk/hope-rotor-spacer

The only reason is to get the NDS spokes tighter, without messing up the dishing.

Imagine you're facing the bike from the back, I'm adding 5mm of axle spacers to the inside of the left dropout to push the rim (the entire wheel really) 5mm more to the right, just so I can then tighten up the NDS spokes - that, at the same time, will bring the rim 5mm to the left, back to the center again.

Adding those 5mm of axle spacers pushes the disc rotor 5mm to the right as well, which is where the aforementioned and linked to Hope rotor spacers come in. I'm putting 5mm worth of those spacers under the disc rotor to push it 5mm to the left and back in line with the brake pads, to exactly where it was.

What I should end up with is a wheel dished properly with the NDS spokes a lot closer to the tension they should be.

Something I was thinking wasn't possible until I saw those disc spacers and realised how they can fix it.

With the Hope disc spacers on, it needs 14mm rotor bolts (increased from 8mm) with 1mm washers under the heads to give an effective bolt length of 13mm and that should be it done.

I measured about 97 kgf on the DS spokes and 67 kgf on the NDS spokes. I know the drive side is just about right at 97 kgf, but with the NDS only being at about 67 kgf that's worrisome, it's just not enough, especially for a wheel getting tugged on by a motor.

As for stressing the rear dropouts with an effectively 5mm wider hub - it will slightly but luckily the dropouts are about 137mm when relaxed, so there's not much bending needed to fit the (presumably around 140mm) hub.

Just how are you meant to measure the width of a hub motor? You'd need some sort of insane looking vernier caliper with 2ft long prongs :lol:

I got some tooth floss and put a bit on each side of the axle with a weight attached but it was so crude, I think maybe a plum bob with cotton (or the tooth floss again) might do the trick.
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NATURAL ANKLING
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Re: Wheel Dishing Dilemma

Post by NATURAL ANKLING »

Hi,
I'm assuming you are using plain gauge spokes?
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Jdsk
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Re: Wheel Dishing Dilemma

Post by Jdsk »

Manc33 wrote: 21 Aug 2021, 3:52amJust how are you meant to measure the width of a hub motor? You'd need some sort of insane looking vernier caliper with 2ft long prongs

I got some tooth floss and put a bit on each side of the axle with a weight attached but it was so crude, I think maybe a plum bob with cotton (or the tooth floss again) might do the trick.
How about something like:
Make a plain calliper... long wooden arms, protruding screws for the point of contact. Set it snug and fix the hinge tight. Then remove it and use a ruler or tape measure.

Jonathan
Manc33
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Re: Wheel Dishing Dilemma

Post by Manc33 »

NATURAL ANKLING wrote: 21 Aug 2021, 8:06pm Hi,
I'm assuming you are using plain gauge spokes?
Yeah they measure 2.5mm thick.
Jdsk wrote: 21 Aug 2021, 8:13pmHow about something like:
Make a plain calliper... long wooden arms, protruding screws for the point of contact. Set it snug and fix the hinge tight. Then remove it and use a ruler or tape measure.

Jonathan
Cheers I'll try to fabricate something.
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Manc33
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Re: Wheel Dishing Dilemma

Post by Manc33 »

In the end there was no dilemma and not much prizing apart of the dropout to make it fit.

In the end the average tension on the NDS is about 76 kgf and the DS is about 91 kgf.

That's probably under what it should be but I have probably tightened the DS spokes about half a turn and the NDS spokes about 2 turns compared to how it was (factory built). That thing is so true now, I had friction on 1 sheet of paper between the rim and the thing on the truing stand, with no scraping when the paper is taken out - in other words it's true to within 0.1mm :mrgreen: Same on the roundness.

The dish is deliberately 1mm off, with the rim towards the NDS (of course :roll: ) just so I can get those pesky NDS spokes that little bit tighter. I also have something like 8.7mm worth of spacers now on the inside of the NDS dropout, again to get the NDS spokes tensioned a bit more. They were at 65 kgf to start with, which is a bit silly when they are supposedly meant to be at least 100 kgf on the NDS (maybe more) and 100-120 kgf on the DS. It's some Chinese rim so I don't want to risk it, I know from turning the spoke key on the DS spokes, it's going to get risky with another half turn.

If I start getting issues I'll buy a better rim, maybe that one Spa sells (that's only about £30) with directional drilling, along with spokes I've actually heard of opposed to whatever must be on this China wheel. I already know something with angled drill holes would be far better from looking at how some of my spokes are bending at the nipple going to the hub with its flange of about 145mm.
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