Mechanical Disc fitting by shop

[Paulatic]

I’d like your comments on the following tale I’m going to tell.
A son bought a bike from an online retailer. He didn’t consult his dad at all I was there last week and viewed the bike. It has Tektro Lyra mechanical disc brakes fitted with the front brake applied I could push the bike forwards and backwards. The back wheel locked in either direction. I took a look at it and, after consulting The internet tried to improve it. If it was good it binded and if it didn’t bind it was poor.
It doesn’t have any barrel adjusters fitted and looking at the Tektro fitting guide it should have one.
So I contacted the shop and this is the conversation so far
to my original mail

Hi,

Thanks for your email and sorry yo are having problems,

There are no barrel adjusters for these brakes, there are adjustment screws at thew side, but if you wish to add cable tension it will be a case of undoing the cable and pulling it through a bit more.

I replied with Thanks for your reply and advice. I had already attempted your suggestions and found it very hit and miss and still an inadequate brake . On only one of my attempts was it not possible to push the bike forward with front brake applied.
I also find your reply puzzling as the way I read the Tektro fitting instructions http://www.tektro.com/dowfile.php?p=33 they mention barrel adjusters which I why I asked the reason none were fitted to this bike.

They reply

Thanks for your reply,

However the stock of these that we have recived have no barrel adjusters fitted to them munfortunately.

Now this is a shop I’ve bought stuff from quite happily and indeed I’ve thought their bikes looked good value but my initial instinct to that last comment is "Well if there was none in the box why not fit some?"

[Eyebrox]

I assume the adjuster has been removed for cost reasons. The brake can only be adjusted via the hex bolt behind the pad. Wiggle sell inline adjusters for £2 each.

[robgul]

I'm not familiar with that specific cable calliper but the following may be helpful:

First off check that the rotor is centred in the calliper - the most effective way I've found to do this is to loosen the two bolts holding the caliper on the fork, squeeze the brake lever so that the pads contact the rotor - and the calliper itself may/may not move slightly - still squeezing the brake lever tighten the two bolts holding the calliper.

Chances are that the cable will then need taking up a little as it pulls the actuating lever to get the pads at the correct distance (pretty close!) from the rotor (this is the same process as a normal rim brake cable adjustment) - a third hand/cable puller is a useful tool for this operation.

For all that it's a little odd that there are no barrel adjusters either on the brake calliper or inline in the cable. I build up lots of new bikes from the box and cable discs invariably need the treatment described.

Rob

[mattsccm]

Not to frighten you but keep on top of them. I had a pair, as did several other people I know, that would, once there was some wear in the pads, do what I would call "overcam". They are meant to go so far then the pad against the disc stops it going further. If a bit worn they went so far that everything went slack and the lever bottomed. Releasing and grabbing again, usually in a panic sorted this. Maybe they have changed, lets hope so. Mine had no adjuster as standard.

[531colin]

I'm not clear what sort of mounts these calipers are on.
ISO mounts (basically a couple of bolts through the dropouts) can be "faced" with the appropriate facing tool so the mounts are properly square to the wheel axle. If there is paint on the raised bit of dropout where the caliper bolts to the dropout, this definitely hasn't been done.
Facing the dropouts means the pads will strike the disc "flat on" so the whole braking surface is used, this is a good thing. Avid BB7 calipers have cup and cone washers similar to Vee brake block holders so facing the dropouts isn't essential.
As already said, the caliper has a restricted amount of movement. Its generally recommended to set the pads as close as possible (without dragging) using the pad adjuster(s) and centering the caliper. If you use some of the cable movement to set the pads then you risk running out of travel once the pads are worn down a bit.

[Brucey]

'thing that was bought from the internet wasn't quite what was expected'.

Not exactly a big shock, is it?

FWIW that sort of brake (which is similar to a BB5 or a Promax render etc etc etc) will usually have a barrel adjuster, because the fixed pad adjuster alone is not sufficient to keep the brake in adjustment. IMHO mechanical disc brake setups should either have a pad adjuster on both pads (eg BB7) or a barrel adjuster on the cable plus a fixed pad adjuster (e.g. BB5 etc). Note that the latter is often inherently less satisfactory (esp in a 'road' brake) because the brake arm can run out of travel.

Tektro make innumerable different versions of their brakes; I've not seen Lyras with no barrel adjuster, but that they exist doesn't surprise me; they may have been made (e.g. as OEM parts) for a manufacturer intending to use brake levers with a barrel adjuster built in (eg crosstops) on their bikes.


FWIW new disc brakes often don't seem terribly impressive until the brakes have bedded in.

Quite how much effort it is worth expending in a tedious argument with a retailer over this when inline adjusters will solve your problem and cost very little is open to question. Presumably the bike was priced accordingly....?

cheers