New disc brakes...

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CharlieJohnson
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Joined: 8 Nov 2011, 5:16pm

New disc brakes...

Postby CharlieJohnson » 3 Nov 2014, 9:59am

Hi all, I'm looking to replace the disc brakes on my Dawes Super Galaxy (2014). It came with Shimano BR-R517 mechanical disc brakes with 160mm rotors, which are pretty terrible. They require regular adjustment as the lever travel steadily increases over about two weeks until the levers are touching the bar tape. They also do not have barrel adjusters (!!) which means I have to adjust by tightening the cable and changing the position of the pads. Which is a bit of a hassle at such regular intervals.
I've never had disc brakes before so I'm not too sure what the best course of action is. Any suggestions as to why they may be behaving like this? I was under the impression that disc brakes required less adjustment and maintenance than regular callipers.
Would it be possible to replace the callipers without getting new levers? Any suggestions for good callipers? Should I go for hydraulic this time or is that not possible with the levers I have (Shimano ST-4603 STI)?

Thanks for any advice!

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: New disc brakes...

Postby Brucey » 3 Nov 2014, 11:53am

you shouldn't use barrel adjusters to adjust disc brakes anyway; in a single ride, maybe (and you can fit inline adjusters if you want to), but to compensate for pad wear in the long term, certainly not. For that you need to use the fixed pad adjuster that is built into the caliper. If you don't do it this way you will end up with no brakes before the pads are half-worn.

You can download the manual ('dealer only' ho ho) from the shimano website.

Some disc brakes are pretty good, but as a breed the way they are touted is somewhat overblown IMHO, and for some riders they actually create more problems than they solve.

cheers
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foxyrider
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Location: Sheffield, South Yorkshire

Re: New disc brakes...

Postby foxyrider » 3 Nov 2014, 1:10pm

ah the R517's!

the upgrade that will work on your bike is to a pair of TRP HY-RD hydraulic calipers - you can use them with your existing shifters. Cost is @ £100 per wheel http://www.jejamescycles.co.uk/trp-hybr ... 87434.html
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

mrjemm
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Joined: 20 Nov 2011, 4:33pm

Re: New disc brakes...

Postby mrjemm » 3 Nov 2014, 1:21pm

Nobody mentions BB7? Odd.

I recommend... Avid BB7. The standard in mechanical disc brakes to which others are compared, usually poorly.

The HyRid things Foxy suggests may well be good, but are not really necessary to improve braking. BB7 brakes are plenty powerful for anyone, I would suggest, as would many here, and out there. And are adjustable, so no need to move cable or use barrel adjusters.

Brucey, I know you are not sold 100% on disc brakes, but when somebody's bike already has them, and wants to make them better, is it suitable to bemoan them as a type, especially when it is so clear that a great many people love them? Sounds like you'd suggest changing bikes rather than just improve on brakes as the OP desires, which is a sensible, practical, easy, and not particularly expensive alteration.

:)

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: New disc brakes...

Postby Brucey » 3 Nov 2014, 1:38pm

actually I was if anything bemoaning the way they are touted more than the brakes themselves... :wink:

If I really thought they were so terrible I wouldn't use them myself, but IMHO it is a matter of horses for courses; they are certainly not a panacea for all braking ills....

I would also suggest BB7s or at least sintered pads in the shimano calipers (if the discs themselves are suitable; not all are). Sintered pads usually wear more slowly than most other types so you don't have to adjust the brakes so often.

I would - especially if you were to think of changing pads in them to a different type- be a little concerned about the Tektro calipers; I can't see any reason why they shouldn't boil up (just like any other hydro system) if you were to (say) fit sintered pads to them and then use them hard on a long descent.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Mr_average
Posts: 29
Joined: 6 Sep 2013, 7:15am

Re: New disc brakes...

Postby Mr_average » 3 Nov 2014, 1:43pm

+1 for the Avids - just make sure you get the 'Road' version to work with your levers. The TRPs are probably great too (I have no experience of them), but you should be able to get a pair of BB7s for less than £100. Maybe a fair bit less if you can go without the rotors.

All that said, while the Shimanos aren't likely to be as good as BB7s or TRPs, I don't see why they should be going out of adjustment so badly. Is there a cable slipping issue or cable housing splitting problem somewhere? As Brucey explained you should only need to tighten the cable to take the slack out, and any subsequent cable stretch; pad wear must be taken out by adjusting the pads. They're quite different things and not following the guidance on this is potentially hazadous. Maybe search for some on-line brake setup guide for your brakes and try following that before considering a replacement?

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al_yrpal
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Re: New disc brakes...

Postby al_yrpal » 3 Nov 2014, 2:02pm

Its simple. The pads are wearing in and the cables are stretching which they will do initially. You may be coming up against the stops, so make sure the moving pad isn't doing that. Get the instruction leaflet and readjust them step by step. There is nothing wrong with Shimano disc brakes.

Al
Touring on a bicycle is a great way to explore and appreciate the countryside and towns you pass through. Make a difference...

CharlieJohnson
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Joined: 8 Nov 2011, 5:16pm

Re: New disc brakes...

Postby CharlieJohnson » 3 Nov 2014, 2:26pm

Hi Al, the bike is almost a year old and ridden most days, strange that it should still be wearing in/stretching cables. Not coming up against the stops either. And I have tightened the the non-static pad all the way in and there's still too much travel in the lever for my liking. I agree that there shouldn't be a a problem with the calliper unit though. I'll try replacing the cable and pads and see what happens... If it's still not doing the job, I'll upgrade to the BB7s or TRPs.
Thanks for the advice all!

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RickH
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Re: New disc brakes...

Postby RickH » 3 Nov 2014, 2:58pm

Make sure the static pad is adjusted right too - otherwise you are putting a lot of your effort into bending the disc with the moving pad until it also contacts the static one.

There are measurements in the intructions (Dealer's Manual PDF), but I find a good rule of thumb is to have both pads as close to the rotor as they will go without any rubbing and little/no cable slack (but the calliper mechanism still reaching its rest stop & not being held away by the cable). If the bite point is too sudden back the pads off a smidge (to use a technical term :wink: ) rather than slacken the cable.

With disks, as Brucey says, cable adjustment should only be to remove cable slack or for a temporary adjustment while on a ride (or carry a suitable allen key in your pocket/ toolkit/ wallet to adjust the pads). I find a standard L shaped tool works best as it is generally easier with the brakes on my tandem to use the long end & turn with the short end (limited access/ little force needed) as the BR M495s have a 3mm hex hole for both adjusters. It looks like it is the same for the BR-R517s.

Rick.

southerly
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Joined: 31 Oct 2014, 12:27pm

Re: New disc brakes...

Postby southerly » 3 Nov 2014, 4:32pm

Interesting thread for me.
My Cannondale 500 came with the original Magura hydrolic brakeset. Great until you lose fluid and impossible with the kit provided to obtain the original pressure.

My bike is a hybrid, so should I go for the mtb or road set? The nuvinci hub comes ready to use disc brakes.

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al_yrpal
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Re: New disc brakes...

Postby al_yrpal » 3 Nov 2014, 4:39pm

CharlieJohnson wrote:Hi Al, the bike is almost a year old and ridden most days, strange that it should still be wearing in/stretching cables. Not coming up against the stops either. And I have tightened the the non-static pad all the way in and there's still too much travel in the lever for my liking. I agree that there shouldn't be a a problem with the calliper unit though. I'll try replacing the cable and pads and see what happens... If it's still not doing the job, I'll upgrade to the BB7s or TRPs.
Thanks for the advice all!


Loosen the frame screw to just nip the brake mechanism. Using a business card between the static pad and the rotor is a good way to position and align the brake mechanism. Then tighten up the socket screws that hold the brake to the frame, then position the card between the moving pad and the rotor and adjust the moving pad to get the lever at your chosen bite point. I have BB5s which a lot of people slate, and thats the way I do it. Hope this helps.

Al
Touring on a bicycle is a great way to explore and appreciate the countryside and towns you pass through. Make a difference...

reohn2
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Re: New disc brakes...

Postby reohn2 » 4 Nov 2014, 9:07am

Not much to add really,MrJemm seems to echo my thoughts on disc calipers.
BB7's do it and do it well with minimum need for attention,a squirt with brake cleaner and the odd click on the adjuster once in a while.Good modulation awesome stopping power,I've four bikes on them and am very pleased.

Forget hydros who needs 'em when cable discs are as good as BB7's?

I've no experience of Shimano Disc calipers only that a friend has one on his tandem and it's no end of trouble :?

Brucey
Discs are everything they're cracked up to be if those discs are BB7's :wink:
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mrjemm
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Joined: 20 Nov 2011, 4:33pm

Re: New disc brakes...

Postby mrjemm » 4 Nov 2014, 9:30am

reohn2 wrote:Forget hydros who needs 'em when cable discs are as good as BB7's?


I am tempted to upgrade Mme's pink one to BB7s from hydraulics! No flexibility in lever choice and the hoses/reservoirs are real-estate greedy on her bars- can't fit a noodle to them!

Was just thinking about those hybrid jobs, and thought to myself that for average joe, i.e. me and many others, or for anyone who wants to tour, they're just plain daft, surely. Carrying/sourcing spares and maintenance for one type of brake is bad enough, but cables and bleed kits... (another reason to swap out Mme's hydros for mechs, when I ain't swapping my BB7 for hydros any time soon!).

Wesh-Laurence
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Re: New disc brakes...

Postby Wesh-Laurence » 4 Nov 2014, 9:34am

I have Avid BB7s on my drop bar touring bike which when set up correctly are excellent, almost as good as some of the hydraulic discs I have on my mountain bikes. I have found that compared to rim brakes good disc brakes are far better than rim brakes. I now have brakes on 5 bikes, the 6th bike is a folding bike and I can't fit discs on it.

Beware when buying BB7s there are 2 types one for Road Levers and the other for Flat Bar Levers.

Brucey
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Re: New disc brakes...

Postby Brucey » 4 Nov 2014, 9:36am

reohn2 wrote: Brucey
Discs are everything they're cracked up to be if those discs are BB7's :wink:


BB7s are pick of the bunch for many uses, for sure. But with organic pads fitted they wear just as quickly/behave unpredictably as lots of other systems in wet conditions, and with sintered ones they are usually somewhat noisy. The fixed pad adjusters can seize in both BB5 and BB7 calipers, (which will strip the plastic adjuster knob and/or scrap the caliper) and in exceptional conditions the FPA adjuster knob can even melt. The brakes add weight to most bikes (vs rim brakes) and almost invariably require that the frame (and especially the fork) is stiffer and heavier too. For some types of riding all this is fine, a good compromise. But I've owned dozens of bikes with rim brakes that I would describe as 'comfy' with lightweight wheels and relatively skinny tyres, but none with discs as yet.

The presence of rim brakes does not guarantee a compliant frame and fork but the presence of disc brakes is a very good indicator of a frame/fork that is rather stiff. [BTW people tell me that there are some CF disc forks which have a detectable amount of compliance out there too, but I have not seen or used one myself as yet.... :roll: ].

So if you want disc brakes and comfort I think (suspension aside) you need to run quite wide tyres; if you are going to do that anyway and/or fat tyres suit you then fine, a stiff fork may not make that much difference. But when I see disc brakes touted as a panacea for all ills I have to take issue with it. Realistically it just gives you a different set of compromises to work with; it can be a very good set of compromises for some uses but it certainly isn't for all.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~