Cycling UK Forum

you have to do this properly IMO. Their emails are real nonsense and it is worrying that that’s their to response to what they seem to assume is an uneducated customer. get a solicitor.

And I didn’t realise the twist was unique to these! Interesting. I think I’m going back to a mafac on the rear and I’ll use a second hand Paul I’ve picked up for the business end. Old and new !

Brucey wrote:IIRC the 737 arms were (unlike all other weinmann CPs) formed at that point with a 90 degree twist near the point of failure. I have often wondered if this might weaken the arms; now I have my answer!

Is this a 100% clean break or is there any sign of a pre-existing crack on the fracture face?

cheers

If there is a sign it’s too small for an I expert eye to see.

Brucey wrote:

mboro1876 wrote:….HOWEVER.. it’s somewhat moot now, I did a few heavy, front-loading stops to test the current cable setup and during such, one arm of the brake snapped clean in half and flew off sideways! Old aluminium I suppose, glad it happened in testing!....

goodness me! Any pics of the failure?

cheers

I’ll try and remember to get one tomorrow. It wasn’t near where I’d been filing at the slots (though with stress risers and stuff I don’t understand I guess that could act at a distance). At the ‘twist’ in the arm... just a clear snap through.

PT1029 wrote:The M6 bolt (10mm spanner nuts) is designed for normal (and none Weinmann) canti yokes which are flat plate where the bolt head sits - thus the head can clamp down onto the cable.
The correct M5 bolt (8mm spanner nuts) head I think slots in the groove, allowing the bolt to clamp move further in and clamp the cable.
The head on the M6 bolt is too big to fit in the groove, so the head bottoms out on the yoke before it has clamped the cable.
Correct Weinmann bolts would do the trick. You could file 2 flats on the M6 bolt head to allow it to slot into the groove in the middle, then I would expect it to clamp securely (but do check before you ride down hill!). File your flats so the cable hole aligns vertically.

From what I can see in 1 photo, the caliper seems to have "V" brake pads fitted, not quite original/matching, but as Brucey has said many times before, they set the brake up with much better mechanical advantage (so they work better).

Thanks for this: the nuts are already 8mm so I’m not sure I don’t already have the bolt you spoke about.

HOWEVER.. it’s somewhat moot now, I did a few heavy, front-loading stops to test the current cable setup and during such, one arm of the brake snapped clean in half and flew off sideways! Old aluminium I suppose, glad it happened in testing!

So it’s going to be back to a spare MAFAC on the front, or something else newer. The weinmann may stay on the rear, and thanks all for the input which may yet come in useful there...

Brucey wrote:the groove does look quite deep. A test; if the pinch bolt won't grip gear inner cable at all, that tells you that you have less than ~0.5mm to play with in terms of gripping standard brake cable.

cheers

good idea for a test! and yes I agree it looks deeper than it need be. Assuming that ends up to be the case, I'm trying to think of a solution because this would happen with any pinch bolt, the groove being part of the housing:
1) a washer between the pinch bolt's head and the groove, so that the cable is gripped between the washer and pinch bolt head? This would take the groove out of play. The washer may deform a little due to the groove but that would be alright.
2) the solution I currently have, gripping the cable between the pinch bolt head and the metal outside of the groove, therefore not using the hole in the bolt at all. I feel antsy about this but it is the method that the shimano single-pivots on my other bike uses.

do you see anything prima facie awful about this two ideas?

Brucey wrote:is the bolt bottoming out inside the domed nut, or running out of thread where the nut goes? If it looks like it might be, try adding a couple of washers?

Edit; or is the flange on the back of the bolt fouling the housing?

cheers

Thanks. I'm using a couple of washers instead of one under the NUT [edit] and it doesn't seem to bottom out and there is enough thread. I may have some spare appropriately sized 'open-backed' nuts to try to eliminate the bottoming-out possibility.

The flange does not obviously foul something viz. being too wide in diameter and touching bits it shouldn't. But the fact that the groove and hole combination do not tightly-enough grip the cable suggests that something is not right, somewhere. Is it really possible for the groove to have widened enough to cause this, over time? I would have thought that would require repeated slippage.

cycleruk wrote:Like this :-
https://www.sjscycles.co.uk/brakes/d2o- ... bolt-5-mm/

I couldn't think of the correct name for it. Brucey to the rescue.

Yes I see. I'm sorry if I wasn't clear initially, but this is the bolt I have, as far as I can tell visually. The cable slips when run through the hole and the channel.

Brucey wrote:you need to get the correct (drilled) pinch bolt. IIRC the right one is fitted to nearly every weinmann brake, be it side pull or centre pull. unfortunately it looks as if the new bolts are M6 threaded which means the brakes probably won't accept the original (M5 I think) threaded bolts in the best way any more.

cheers

Hi Brucey,
Cheers! The pinch bolt is indeed drilled with a hole, but when I put the cable through the hole and lying in the groove, that's when it slips. I'm not sure what you meant about the M6 vs M5 threaded bolts. The current bolts give the appearance of being useable in the designed way, i.e., they are squared off so they don't rotate, the cable goes through the hole, and lies in the groove, and is clamped. It's just that the clamping isn't tight enough apparently.

cycleruk wrote:There appears to be a central slot as well. This makes me wonder if it should have a bolt with a hole through to clamp the cable ?

Thanks for the reply. You're right there is a central slot, and the bolt (aftermarket) has a hole in it like the original would have -- though perhaps in some other important respect the aftermarket bolt is wrong. The issue is that, when clamped in the way it seems designed to be (the slot, the hole), the cable slips. That's why I've got it like this at the moment, because putting it between flat surfaces at least seems to deform the cable and give enough grip... for now. Any ideas?

Weird one here.

I have these Weinmann 737's with the solid metal straddle. At some point, the cable pinch bolts have been replaced as they're quite new looking compared to the rest. So I'm not totally sure that they are functionally identical to the originals. That might be important.

The problem is the cable is slipping even when the bolt is tightened down. As you can see in the pictures, there is a clear 'channel' in the straddle body where the cable, when inserted into the hole in the pinch bolt, sits. It seems to be that this channel does not close sufficiently even when the nut is totally tightened down, so the cable slips through when the brake is applied. Whether this is due to cumulative wear of the channel, or the aftermarket pinch bolts not being quite right in geometry, I don't know.

For now I've made a functioning front brake for the short ride home, by instead of putting the cable through the pinch bolt hole, running it along the side of the pinch bolt where it can be squeezed against flat metal rather than squeezed in the channel. Is this a terrible solution/bound to fail?

More importantly, any ideas here? The brakes are in good shape and work well so I want to keep them. Perhaps somebody else with this model can send a picture of the pinch bolt, to see if mine are mis-shapen in some way?

Thanks!

Ah. Bit of grease appears to solve that twisting issue. Thanks ahain

The koolstop thinlines are working well so far , very powerful. I’m struggling with one thing: is there a knack to getting them mounted tight enough that they don’t rotate when applied hard? Would a fanged washer help? I’m wary of going crazy and stripping the thread

Brucey wrote:clarks gold work OK (the inserts are thicker than many others in this pattern BTW)



you can use any XTR pattern insert in these holders and if needs be you can change the stud for a longer one (requires some filing/grinding)

However these brake blocks are quite long and may interfere with the fork blades.

NB the studs in these brake blocks are threaded M6 but it is a rolled thread; the centre part of the shank is a smaller diameter and this means you get a little extra brake reach for free.

cheers

Just to tie this up: I ended up with koolstop thinlines for the weinmanns. They seem to fit very nicely and allow toe-in etc... the Mafacs are great but these weinmanns are in better nick and wander around the rim less when applied. So, before going to work on the Mafacs I will give the weinmanns a go with proper pads. Let’s see!