New Bike: Should I Accept Rubbing Disk Brake?

[bikeman66]

After disk binding (and other) problems with a new Specialized and after much consideration i decided to opt for A Boardman Hybrid Team instead. Went to pick it up today and guess what - the front brake is binding. Guy reckoned disks were like that sometimes and it would 'bed-in'. Or he could give it a full bleed but then it would need a full bleed again after 6 weeks which would be chargeable, or......

In the end i said i'd call back for it tomorrow but i really don't think i should accept anything less than perfect. Anyone care to comment, please?

Strictly speaking, I shouldn't be helping you here, as I am a Charlton Athletic supporter, but for sure the line about bleeding the system is a bizarre thing for someone who is supposed to know about bikes to come out with. If there was a spongy feeling at the lever, then yes, bleed the system. As previously suggested,a tweak of the actual disc to make sure it is running true would be the first place I'd look. If it is a closed system, like I have, then it is possible for higher air temperatures to "pump" the system up, and especially when combined with the heat developed during actual braking. This could be a factor. I sometimes have to back the pad adjusters off on my Scott during warmer weather. However if it is an open system this shouldn't be an issue.

 

[Citius]

Strictly speaking, I shouldn't be helping you here, as I am a Charlton Athletic supporter

I'm a Reading supporter - so you can both sod off....

 

[autolycus]

Oh dear - i knew the avatar was a mistake :-(
Anyway, i think the bottom line is that this is fixable, and should be fixed before i accept the bike?

 

[Klassikbike]

Adjusting the correct calliper position on disc brakes is really easy.
You just need an allen Key, loosen it slightly. Eyeball it to the correct position so that there is a gap on both sides (Gap can be tiny). Tighten it again while holding it in position with your hands. Spin your wheel and check that there is no rubbing sound. If there is repeat the process.
For me thats a 1 min job.

If however it just istn't possible to get a small gap on each side, one of the pistons might be pushed out a little. Take out the brake pads, use a scredriver or something hard but with a flat surface and gently push in the pistons. Place the pads back in and do the eyeball calliper adjustment. 3min job done.

 

[Banjo]

Threatening to make you pay extra or lose part of your free first service is completely outrageous.

Take it back ask for manager say its not set up correctly and your now getting fed up .

 

[autolycus]

Well, i decided to accept the bike. I rang before going and was told it was 'all fixed', but when i got there it was a question of 'there's almost no rubbing'.

Ordinarily i would have walked away, but with all the hassle and a similar sort of experience with another large bike retailer i have concluded that disk brakes always rub a little or clack or graunch. One or two comments here seem to support this idea. I have just been rather ground down by it all and what i was looking forward to as a pleasurable treat for myself has become a matter of some stress. I can't really get a bike in the car, so trips to pick up or drop off the bike require imposing on friends or awkward routes by bus. I genuinely wish i'd held on to my Ridgeback Comet and I shall certainly not buy another bike with disks. Or from Halfords. Oh, and i've noticed now that the rear brake rubs more than the front one.

I may have a go at them myself and appreciate the tips from Klassicbike. However, if the rub is only on certain parts of the disk when you spin the wheel, it seems to me more likely that the disk itself is 'out of true'(?) I'm wary of making things worse if i try to bend it right.

One consensus here seems to be that the idea of brakes needing a full bleed is total BS?

 

[bikeman66]

Well, i decided to accept the bike. I rang before going and was told it was 'all fixed', but when i got there it was a question of 'there's almost no rubbing'.

Ordinarily i would have walked away, but with all the hassle and a similar sort of experience with another large bike retailer i have concluded that disk brakes always rub a little or clack or graunch. One or two comments here seem to support this idea. I have just been rather ground down by it all and what i was looking forward to as a pleasurable treat for myself has become a matter of some stress. I can't really get a bike in the car, so trips to pick up or drop off the bike require imposing on friends or awkward routes by bus. I genuinely wish i'd held on to my Ridgeback Comet and I shall certainly not buy another bike with disks. Or from Halfords. Oh, and i've noticed now that the rear brake rubs more than the front one.

I may have a go at them myself and appreciate the tips from Klassicbike. However, if the rub is only on certain parts of the disk when you spin the wheel, it seems to me more likely that the disk itself is 'out of true'(?) I'm wary of making things worse if i try to bend it right.

One consensus here seems to be that the idea of brakes needing a full bleed is total BS?

Sorry to hear about the grief your bike purchase has caused, but now you've got it just try to enjoy the riding. I think a lot of disc systems probably drag very slightly, and most of the time it won't be audible so shouldn't cause too much of an issue.

It is possible to buy disc truing fork tools pretty cheaply from cycle shops. These make truing a slightly warped disc easy. Basically, spin the wheel and observe whether the disc runs closer to pads at specific points in the revolution. I have, previously, drawn a felt tip line around the outside edge of the disc, spun the wheel and wherever the felt pen had been rubbed away, made tiny adjustments to the disc at that point.

Although all this hassle has dented your enjoyment at this stage, I'd be pretty confident (and hopeful, for your sake) that you'll soon forget any slight drag and really start to appreciate the real advantages of a disc brake system.

If it really is causing you stress, perhaps the opinion of a local bike shop may be worth seeking. They will tell you (without the added dimension of the fact they're trying to sell you a bike) whether discs do just drag or if there is a way to improve your problem.

As I mentioned earlier in this thread, my Scott MTB has a "closed" hydraulic disc system and I'll quite often have to back off the pad adjusters in spells of warmer weather, as the brake fluid warms up, expands and causes the pads to contact the disc, which then leads to a highly annoying squeal at a certain speed. If there is any way of backing the pads off on your system, perhaps try that, but I think I'm right in saying that most hydraulic brakes are self adjusting these days.

You shouldn't have to put up with all this on a new bike, but once it's sorted I'm sure you'll look back on this episode as a minor inconvenience and just enjoyed getting out for great bike rides.

 

[autolycus]

Thanks bikeman, i'll give it a go. Feeling a bit more positive after a couple of rides, though gutted i missed the 10%off flash sale today :-(

 

[bykeshed]

If both pads rub constantly, the pistons may need resetting (pushing right back in, system re-bled etc). If one pad rubs constantly, the caliper needs centering. If either pad rubs only at a certain spot on the disc, as others have mentioned, the disc could be warped (but shouldn't be if new and bought from a good bike shop...).

In my experience, mechanical disc brakes do rub sometimes, especially on cheaper machines with restricted caliper adjustment. Hydraulic brakes usually means a better quality machine with better adjustment for calipers, so can be set up better to eliminate rubbing.

A good local bike mechanic should be able to have a look (for free) and probably set your whole brake system up properly, for cheap.