Disc Brake Problem

stever1957

Pedelecer
Jun 9, 2018
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32
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Lake, Isle of Wight
Ah, I posted this in the Technical forum, before I noticed that this forum existed:


I've never had a bike with a disc brake before, so I know nothing about them or what to expect from them.

I do know that the mechanical (non-hydraulic) disc brake on the front wheel of my new Woosh Big Bear is far, far less efficient than the regular V brake type on the rear wheel. Indeed, when it comes to stopping the bike, the disc brake will only slow it somewhat, whereas the rear V brake does all the stopping.

From a stationary position, it will not lock the front wheel and I can easily push the bike forward.

I have tightened the cable, but am at a loss as to how to further adjust it.

Is this a common sort of thing with disc brakes?
 

Woosh

Trade Member
May 19, 2012
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Southend on Sea
wooshbikes.co.uk

stever1957

Pedelecer
Jun 9, 2018
51
32
61
Lake, Isle of Wight
I'll try to take photos in the morning. There appear to be some scratch marks on the disc itself, which probably explain the occasional grating sound I was hearing today, when applying the brake.

Even on day one, the rear brake was more efficient than the disc.

I'll give the alcohol a try (just on the bike!).
 

Woosh

Trade Member
May 19, 2012
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Southend on Sea
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The lines you see on the rotor are normal. The pads need them to provide stopping power.

you may find this video useful:

 

Woosh

Trade Member
May 19, 2012
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Southend on Sea
wooshbikes.co.uk
I'll try to take photos in the morning. There appear to be some scratch marks on the disc itself, which probably explain the occasional grating sound I was hearing today, when applying the brake.

Even on day one, the rear brake was more efficient than the disc.

I'll give the alcohol a try (just on the bike!).
the 'squeak' you hear is typical when the pads are not pressed flat against the rotor or the rotor is contaminated.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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You will most likely need to clean pad surface as well as disc/rotor surface.
Isopropanol for the disc, for pads I use neat washing up liquid. Remove pads and rub them together between thumb and index fingers rinse and refit.
 

stever1957

Pedelecer
Jun 9, 2018
51
32
61
Lake, Isle of Wight
Being unfamiliar with disc brakes (approaching 100% unfamiliar), I'd feel more confident removing someone's spleen than removing the pads. From what I've read, it is necessary to remove the wheel, which, on this bike, is a major operation in itself.

I'll try getting some of those substances on the parts mentioned though.
 

Woosh

Trade Member
May 19, 2012
11,097
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Southend on Sea
wooshbikes.co.uk
Steve, you don't have to remove the wheel for this.
The most you have to do is to remove the two M5 bolts to remove the caliper.
Try cleaning the rotor with alcohol first. If it does not work, email support@wooshbikes.co.uk

 

Nealh

Esteemed Pedelecer
Aug 7, 2014
7,677
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West Sx RH
IMHO any contamination of disc will also affect pad surface so I would clean both at the same time.
Calliper is simply held by the two m5 bolts and pads usually retained by a split pin or small allen thru bolt.
Refitting is simply the reverse to center the calliper hold front brake lever on before nipping up m5 bolts then release lever, spin wheel to check no rubbing, if so simply repeat the last procedure once more.
 
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stever1957

Pedelecer
Jun 9, 2018
51
32
61
Lake, Isle of Wight
Okay, now that I've got the bike upside-down, I've been able to take those photos (such as they are). I've also been able to get a torch and have a preliminary look inside the 'doings'. On first inspection (and bearing in mind that my actual disc brake mechanism varies somewhat from the one shown in the 'quick manual'), it appears that only one pad is present.
 

Woosh

Trade Member
May 19, 2012
11,097
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Southend on Sea
wooshbikes.co.uk
Yet the link you posted above, to the 'quick manual', says:
  1. Mount bike in repair stand and remove the wheel.
I'll have to do a new manual then!



Just in case you want to remove the motor wheel:

1. undo motor cable
2. undo the two torque arm bolts
3. undo wheel nuts
4. drop the wheel
5. If you suffer from short term memory loss like me, put rubber bands around the washers to keep them on the motor axle, you don't want to put them back in the wrong order or take some pictures as a memory aid.

when you re-install the wheel, it's easier to turn the bike upside down first.
You will need a 10mm spanner.

1. wheel nuts off, torque arm bolts off.
2. while keeping the motor cable exiting downwards, line up the brake rotor with the gap between the brake pads.
3. use the 10mm spanner to rotate the motor axle, then line up the flanks of the motor axle to the opening of the fork's jaws. The wheel will drop back in nicely.
4. re-install the torque arm bolts and the wheel nut but don't tighten them quite until you check all the washers and everything looks snug, then tighten the wheel nuts, then torque arm bolts.
5. Re-connect the motor cable. There are arrows imprinted on the side of the motor cables, line up the arrowheads before pushing them in together until the circle line.

On normal bikes, it's easier to remove the wheel than the caliper, but on the Big Bear, it is the other way round.

You can clean the pads by passing a piece of cloth between the pads and the rotor.

To remove the caliper:

1. take some pictures of the spacers and washers on the M5 allen bolts as a memory aid.
2. remove the two M5 bolts.
The caliper will come off.

To remove the pads:

You need a 5mm gap between the pads to slide them out.
1. With the caliper off, turn the red dial (on the inside of the fork) anticlockwise to retract the inner pad. squeeze the brake lever, unhook the brake cable. You should now have enough gap to push the pads out.
2. Squeeze the springs - push the pads out.

If the pads are contaminated with oil, they should be replaced. Google Clarks Avid BB5 pads for local sources, all local bike shops should have them or email support@wooshbikes.co.uk

https://www.halfords.com/cycling/bike-parts/bike-brakes/clarks-avid-bb5-ball-bearing-five-brake-pads


 

Woosh

Trade Member
May 19, 2012
11,097
8,275
Southend on Sea
wooshbikes.co.uk
it appears that only one pad is present.
you can see the red handles of the pads on one of the pictures you took:



wiggle each handle with a finger.
Can you see the gap between the pad and the rotor?
if you can, check that the gap between the inner pad and the rotor is about 1mm, the gap between the outer pad and the rotor about 1.5mm.
 

stever1957

Pedelecer
Jun 9, 2018
51
32
61
Lake, Isle of Wight
Well, while the forum was down, I read the 'quick manual' again and took another look at my bike. I could see that the disc was not particularly centred in the aperture meant for it in the brake mechanism.

With some trepidation, I removed the caliper apparatus altogether. I found that there were indeed two pads present. Upon removal, I saw that they were somewhat worn, in a manner that I find hard to describe, but that will, perhaps, be apparent in the profile diagram that I have attempted to make (attached).

Anyway, I replaced everything and set the brake up as per the available knowledge and can confirm that the front brake now feels as though it would stop a motorcycle.
 

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Woosh

Trade Member
May 19, 2012
11,097
8,275
Southend on Sea
wooshbikes.co.uk
fantastic! you can now enrol as Woosh local helper!
 
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