TS125 - Rear Wheel Binding

[Throwley]

Been checking out my new-to-me TS125 before taking it out on the road and have already found an issue which I can't solve. It feels like the bearings have a sideload when the spindle's tightened up.

When fully assembled, the rear wheel does not rotate freely but drags/binds as if the brake is ever so slightly on. I've checked both the drive side and the wheel and both run free on their own and do not appear to be missing anything. The internal spacers appear to be correct and the correct length.

I've been looking for a diagram of the fully assembled system (I have the parts list diagram but it's not so helpful) to check I have everything assembled in the correct sequence, but can't find one online - any ideas anyone?

I also have an old BMW, the bearing sideload is adjusted by using 'wedding band' shims; on the MZ parts lists, I can't see any shims or spacers. Are there any?

Does anyone have any pointers as to what the cause may be?

Thanks!

[Puffs]

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[Blurredman]

I concur with the above!

[Throwley]

That's exactly what I thought, but it's both present and correct!

The distance piece in the drive side is also there, I was wondering if there's another one somewhere that I'm missing.

[DAVID THOMPSON]

my 95 Saxon Tour has this setup it is strange to any other bike rear end i have
ever worked on// may need to do a compare with a known good setup
or help from someone local that has one like it
the right side goes in and chain adjusted then left is installed
2 part axle make sure right side does not move when tightening the left

honda dream 305 had covered chain 1966 but never worked on one
my dad made sprockets for them because in later years they were always on back order
at the parts shops used a blank with ready cut teeth and did a proper hole in the middle
they were the daily drivers for the poor part of town

[Puffs]

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[Jay Bee]

Throwley -
I believe my ETZ shares a similar rear wheel setup, and I also experienced a similar problem of brake binding, even with the brake rod disconnected.
Turned out, the brake plate was slighly misaligned due to PO having bent the torque bar away from brake plate when removing rear wheel rather than slackening it off at both ends.
Verify that torque bar is not influencing position of brake plate and apply brake fully to centralise shoes in drum while tightening wheel spindle.

[Throwley]

Verify that torque bar is not influencing position of brake plate and apply brake fully to centralise shoes in drum while tightening wheel spindle.

Bingo! Don't understand how it is at all possible, but the binding only happens with the brake plate in the position at which the torque arm can be attached. Even with the spindle being tightened with torque arm disconnected and foot hard on the brake, once the torque arm is bolted up, the binding starts. I've put a slight S-bend into the arm and have ensured it's parallel to the mating face on the brake plate, and that's got it about 90% free. Will run the bike for a while and monitor the binding.

Thanks, all!

[Puffs]

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[Jay Bee]

Throwley -
Great ! Good to hear that what fixed my problem has also fixed yours.
All I need to do now is figure out what to do with a second preoblem.......my brake drum is oval.
Anyone out there skimmed an MZ hub ?

[Puffs]

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[Jay Bee]

Puffs -
Thank you for your input. However, we are dealing with an original 36 year old wheel here ; I think it's a bit late for correcting drum ovality with spoke tension.
All spokes are rusty and I think it's extremely unlikely that any of the nipples would move anyway.
I'd actually intended to rebuild the wheel and bought a set of stainless spokes some time ago but I would definitely want to start off with a drum that runs true.
I am reluctant to remove and strip the wheel for rebuild if it turns out that the ovality can't be corrected.

[Puffs]

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[Throwley]

Verify that torque bar is not influencing position of brake plate and apply brake fully to centralise shoes in drum while tightening wheel spindle.

Bingo! Don't understand how it is at all possible...

I looked deeper into this binding issue and have found that one of the brake shoes' pivot post drillings is not parallel. When the spindle is tightened, and everything seats into place, this causes the outer edge of the brake shoe to just contact the drum. Any slight misalignment has enough influence over the backplate position to increase this contact and bind the wheel. Unfortunately, I guess due to the flexing of the shoe, or the lower force from the small contact patch, any harsh application of the brake is enough to move the backplate into a position where the shoe skims the drum again. I'll have to try my luck with another set of shoes, I think.

[Puffs]

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