ETZ disc brake front end transplant onto a '77 TS125

[Richard-C]

Hi all,

Well my '77 TS125 forks are shot (the 32mm ones), and I can get an entire ETZ disc brake front end. Can the ETZ yokes go straight onto the frame or are spacers /machining/different bearings needed?

TIA
Richard

[Richard-C]

Having bought most of the front end of a disc-braked ETZ (forks, yokes, wheel, mudguard and braking system) - thanks akirasan - I thought I'd document the change here in case someone else wants to do the same transplant.

First issue: the steering stem fitted to the TS125's bottom yoke is roughly 37mm longer than the ETZ one. Good news is that it fits nicely into the existing bearings but doesn't poke out enough to fit the top yoke to it. I'll look for a local engineering shop to swap the stem over. From the design it looks like the stem was pressed in from the top, then a circlip fitted into a groove in the stem under the yoke, and then pressed up so as to trap the circlip in a recess in the yoke. Can anyone confirm this?

Second issue: I was worried that the wider fork tubes (35mm v 32mm) wouldn't fit through the headlamp ears. They do but I think I'll have to modify the top & bottom rubber sleeves. I won't know for sure until I fit the yokes. The other issue here is that the new forktubes will be spaced a bit further apart - but I guess a couple of washers either side will fix it.

More worries to come: is the rake so different the mudguard will hit the frame under braking?; how will I get around the possible loss of the right-hand handlebar switch gear? (I hate electrics); will I be lynched by rivet counters? Answers sometime in the future.
Richard

[Guesi]

The TS125/150 was built also with 35 mm forks.
So it would be the best that you get a 35mm steering stem from this later TS125.

[Richard-C]

Hi Guesi,

I'm guessing that I can't use the entire bottom yoke from the 35mm-equipped TS as it was for use with a drum brake and the disc brake fork tubes are wider apart - which would mean swapping over the longer steering stem anyhow.

[Richard-C]

Well it turns out you CAN move the steering stem from a TS bottom yoke to an ETZ one.

Inspecting the stems it appeared that they were pushed in from the top until the circlip groove on the stem was visible under the yoke, then a circlip was fitted and the stem pushed back through the yoke until the circlip was squashed between the circlip groove in the stem and a machined recess under the yoke. At least that's how I fitted the loose stem to the yoke.

Freeing the circlip was the first stage of removing both stems and I did this by holding the assembly upside down on a wooden block and using a big hollow drift (actually an old car brake piston -"it'll come in handy one day!"), a copper mallet and a few whacks.

Pushing the stems in and out was done on a mate's Sealey 300 ton hydraulic press. One yoke needed a touch of a blowtorch at one point, but it all went pretty smoothly.

Now for the brake hydraulics...

[Guesi]

Hello..

There were no different yokes for disc or drum brake version (at least at the ETZ models).

The TS 150 models were never meant to carry a disc brake.

So maybe it is different on these models.

MZ NEVER gave the o.k. for fitting the TS 150 models with a disc brake,

Maybe due to the not very stable frame of the TS 150models ?

They allowed the change for TS 250 models...

So it is kinda risky to do the change to dic brake.

The guys from MZ knew what they were doing

[Richard-C]

The ETZ forks and yokes (fitted with the TS stem) are now mounted on the TS. Looks OK although I'm sorry to have lost the early mudguard as I like its style.

The steering lock bracket on the headstock had to be removed as it fouled the back of the headlight but that's the only non-reversible change I made.
Just the brake hydraulics and the wiring to do now!

Taking Guesi's point about MZ never ratifying disc brakes on a TS125, a visual check of the bike shows that the front wheel is on the center line and the rake looks ok. Does anyone know the wheelbase of a standard 1977 TS125 for comparison? (I know - it's something I should have measured when my bike was standard!).

Richard

[Puffs]

Removed

[Guesi]

Hello.

But they allowed the TS 250 to be fitted with a disc brake, so most of your arguments don´t work

The tS 150 frame is not comparable to the tube frame of the TS, so it is good enough for the 150 ccm bike.And it is cheap in production.

I really think they thought that the frame will not stand the force of the disc brake.

They surely had their reasons not allowing the disc brake conversion...

[Puffs]

Well Richard, better watch out then, or you'll be chased by the MZ police!

Luckily they'll be no match for you, with their drum brake.

[Richard-C]

I'll have to use a 15-to-1 mixture Puffs- they'll never see me!

More seriously, Guesi, did the MZ factory ever forbid the use of a disc brake on the TS125, or did they make no announcement at all? I'm not well versed in MZ history so I don't know. I suppose the real-world test will be to slam the brake on at top speed and see if the frame bends......

Richard

[DAVID THOMPSON]

with good brakes you have a better chance of not leaving any bloody marks on the WALL
when you hit it

[Guesi]

There is a list from the MZ factory of allowed changes on several MZ types. And there you don´t find the TS or ES 150 conversion to a disc brake. But you find the TS 250/1.

[Puffs]

Removed

[Guesi]

Hello

Even if I don´t tell a non-swimmer not to jump into deep water, it is not recommended !

As I said, MZ made a list with all allowed changes on several models. 'This means for me that what they don´t mention they don´t allow.

The TS 150 frame is a pressed steel frame. This is cheap in production, but not so stable as a tube frame.
I think that is why they did not allow the disc brake conversion.

And as the list includes all bikes up to the ETZ 250, the avaiablility of disc brake sets should be the problem.