Disc brake newbie has a problem…..

The story is this. I have a Klein Palomino that I have been riding with V brakes.

I then decided to switch to discs. Bought some Shimano centrelock XT hubs on 717 rims and Magura Julie brakes through the forum.

I have installed the wheels and brakes.

The front wheel set-up is excellent – once I realised that i needed a 180mm rotor.

The rear wheel is a disaster (apparently) as applying the brake causes huge vibrations. To recap, this is a Magura Julie caliper (with good but secondhand pads) on a Shimano 160 centrelock rotor.

So far, I have checked that the alignment of the caliper is good (it is), that the centerlock is tight (it is) and that the rotor is not bent (its isn’t). There is a tiny amount of movement in the centrelock if I put the brake on and just rock the bike back and forwards but no more than on the front.

I have also stripped and re-balled and re-lubed the rear hub – it is tight and spins freely even with the caliper fitted.

Can anyone advise what on earth could be wrong with the thing?

My only thought is that it may require bedding in.

A spot of grease on the disc? clean the disc.

Loose caliper mountings?

Pads hitting the spoked part of the disc?

i have never, ever, not even once in my entire life, ridden a ?isc-brake equipped mtb that wouldn’t have been improved immeasurably by the substitution of discs by v-brakes.

Not. Even. Once.

ok, so i know it’s not part of the topic. i just felt i had to say it.

I cleaned the rotor with some meths but there wasn’t much to come off.

The caliper mountings are tight – although there is a bolt on frame mount and an IS to post converter which I initially thought might have been the culprit.

ro, I am very tempted to go back to the way things were!

Ro – want to try an offroad tandem with Vs? I don’t

The main advantage with discs is they don’t wear your rims away.

Does meths not leave a residue? I ain’t sure but I thought it did.

an offroad tandem is an abomination in anyone’s eyes. it’s like the bastard child of satan crossed with one of frank gehry’s nightmare visions.

as such, i agree. it’s the perfect candidate for disc brakes.

Never liked Vs, their performance was too frame-dependant. Anyway, back on topic;

Check your pads dont overlap the rotor spokes too much. Remove your pads, LIGHTLY sand the surface of them (even just on a brick) until the whole surface is “matte” and not polished. Clean rotor again with meths (meths is residue free TJ) and re-assemble. The only place left to find serious play is your headset or fork bushes, I’d say the fork bushes were less likely to cause the vibrations – I have had headsets do this in a big way.

Coffeeking I appreciate the advice, will give it a go and report.

i have never, ever, not even once in my entire life, ridden a ?isc-brake equipped mtb that wouldn’t have been improved immeasurably by the substitution of discs by v-brakes.

So you’ve never ridden an MTB in the wet then?

Never liked Vs, their performance was too frame-dependant

true. good frame design = good braking. but then why buy a poorly designed frame?

the trouble with discs – even if you accept the ‘better braking under arduous conditions’ argument – is they introduce another layer of potential mechanical difficulty into what should be a simple product. setup and maintenance are far more complex that with v’s. or, worse, they add hydraulics where hydraulics should never be.

the op’s difficulties are an example of the former.

as mr chapman said with regard to design, ‘simplify and add lightness’. and he was talking about a product with mucho horsepower. we only have little legs.

So you’ve never ridden an MTB in the wet then?

don’t be a dumpling. i lived in scotland for 10 years. it did nothing but rain.

“as mr chapman said with regard to design, ‘simplify and add lightness'”

he also suggested that the ideal car would collapse at the end of every drive (race)

I’m also fairly sure he was an early advocate of disc braking

Sounds to me like the disk isn’t sitting perfectly flat on the hub.

In my experience, disk brakes are fit and forget, they certainly have been on both my bikes.

oh, and i’m with coffeking – shimano rotors always look to have a fairly narrow friction surface, so you may be overlapping with your pads (I’ve never used shimano of magura discs though)

My hummer used to vibrate on the back quite badly, needed to tie the hose down a bit more. other than that, are you sure the frame is sound?

Ro, why shouldn’t bikes employ hydraulics? I quite like the mechanical advantage it gives me. Disc brakes IMO add a level of control and finesse with a single finger that simply can’t be achieved using v-brakes. I can brake harder when I actually need to, and for far shorter periods with my discs than I ever could with v-brakes. In fact I remember all to well the feeling of “brakes on-still not stopping” that came in the winter on DH corner sections with v-brakes.

i felt my front juddering when i was at penmachno and the pads needed changing anyway so changed them, but when i got them out the actual pad compound wasn’t attached very well to the metal backing plate, in fact it fell off. I put it down to crap pads, won’t be buying off ebay in future. something you could check?

Dekerfer:
I’ve only recently gone over to a disc specific bike, so I understand your in-between feelings. Most of my rides, about 95%, end in me coming home with either ~ 1 1/4 mile, or more commonly 1 3/4 mile descent. I have to say, it is wonderful to get home in control no matter what conditions are under the tyre, not hear my rim being ground away by the grit and sand and actually being able to take my hands off the bars without having to release the ‘deathgrip’ that was necessary with v’s.

I’d advise you to persevere with setting them up, I recon you will appreciate it once they’re sorted.
Saying that, I take my hat off to you for attempting to set them up on your own. When it came to me, I realised I really had no idea so got my lbs to set everything up so at least i had a good point to start from!
best of luck
Q

I’ve had a similar thing happen on my Inbred using Deore discs and it’s because the caliper isn’t quite lined up parallel to the disc surface… causes a rather interesting vibration up to ones posterior!

I quick fiddle with the allen keys and it’s usually all sorted, although it can be quite tricky to get it right.

Had a similar thing with the disc brake on my Giant. I think it was down to the wheel itself, spoke tension or not having spokes in 3x or something. I only had those vibration when locking the rear wheel.

When I got a new set of wheels the problem stopped. The wheels on my old Giant were pretty basic Rigida rims on Formula hubs. Than got some proper Mavic jobbies.

You probably could check if its the wheel by putting it to another bike and trying to brake. If it does the same thing than its down to the wheel.

Thanks for all the helpful comments. I have given the pads a clean up and they are a bit better. The relationship between Magura pads and Shimano rotors may still be an issue but as the front works well, I am assuming that the rear will follow suit.

Thanks again.

or, worse, they add hydraulics where hydraulics should never be.

And of course no other form of transport uses hydraulic discs, does it?
Oh no no no no…….

Personally, I have never, ever found vees anything other than noisy, gritty, inconsistant, fickle and worryingly underpowered on MTBs. And yes, I can set them up just as well as anyone else. They are now just obsolete, except for ultra-light race purposes IMO
🙂

caliper tight to the frame.. disk mounts faced??

I had this problem with some old hopes, and it was because i had the rotor on backwards. I don’t know if thats possible with centrelock, but check that the arms are swaying forward, which is the usual way.

I only changed to discs because i was wearing rims down too quick for my liking. I didn’t even use good Vs, just basic tektros with good levers, full length cables and expensive pads.

he also suggested that the ideal car would collapse at the end of every drive (race) I’m also fairly sure he was an early advocate of disc braking

he did and he was. but i’m in favour or selective quoting 🙂

Ro, why shouldn’t bikes employ hydraulics? I quite like the mechanical advantage it gives me.

well, if i’m being sensible for a moment, then i think for dh only bikes they’re fine, perhaps almost essential, for all the reasons you already know. but most of us don’t hurtle downhill at 50 kph+ and therefore need neither the moderation nor stopping power of well set up hydraulics.

if i have to lug something on a seven hour trek through the mountains i want it to be a) light and b) fixable with minimum tools/skills. in this instance, disk brakes are a solution in search of a problem. people buy them because of the marketing hype/perceived image thing.

And of course no other form of transport uses hydraulic discs, does it?
Oh no no no no…….

yes they do. but they aren’t highly limited in the power required to carry the weighty hydraulics around. perhaps we need power-assisted braking too? yunno, we could fit a compressed air reservior where the bottle cage sits…

i’m sure someone is working on carbon bike-specific disks as we write, despite the fact they only come into their own at very high temperatures. but some suckers out there will buy them and claim they offer ‘amazing stopping power’.

Personally, I have never, ever found vees anything other than noisy, gritty, inconsistant, fickle and worryingly underpowered on MTBs.

maybe it’s a weight thing? i’m about 130 lbs, and find v’s plenty powerful. i’m happy to change my wheels every six months; as a result mr mavic and i have always been good friends and i’ve never suffered spoke or any form of wheel failure.

i guess if you’re a 210 lbs lard-arse you need disks. but then if i met you in the flesh your opinion wouldn’t interest me anyway. tubby people are always dumb (but redeem themselves by making me giggle when i see them on a bike…)

One thing to try – just to see if it’s an alignment problem. Undo the caliper from the adapter slightly, make sure the adapter is firmly done up to the frame then hile pressing the brake lever and tighten the caliper back up to the adapter. This should line the brake caliper, pads and rotor up nicely.

true. good frame design = good braking. but then why buy a poorly designed frame?

I agree, to some extent, unfortunately my wallet doesn’t, so Ive often found rim brakes gave sub-optimal performance on a frame I could afford!

#My favourite brakes, for feel and control and simplicity, are HS33’s. Bit of a bitch to set up but truly fire and forget. They are a little affected by bad weather but the sheer power (and my vice-like grip) means they stop me in anything! I have had to do some serious brake “boosting” though, front 2mm plate:

and ther rear on my trials bike, 10mm thick, 20mm width all around:

😀

i guess if you’re a 210 lbs lard-arse you need disks. but then if i met you in the flesh your opinion wouldn’t interest me anyway. tubby people are always dumb (but redeem themselves by making me giggle when i see them on a bike..

I’m 210 lbs, not a lard arse and definitely not dumb, but I’ll still make you giggle when you see me on a bike!

omg, you’re so young! i’ve been conversing with a child. i feel like a paedo…

*rushes off to have shower*

Dekerfer, the brake is fine, check the rotor/wheel interface and the rotor itself. Also, is the caliper properly aligned?

Ro – hydro discs are simpler with less parts than Vs. Self adjusting is nice as well.

But the main advantage still is not wearing your rims away. I have had a wheel collapse on me from a worn out rim.

but most of us don’t hurtle downhill at 50 kph+ and therefore need neither the moderation nor stopping power of well set up hydraulics.

I do 🙂

Ah, I see where you’re coming from now, you don’t think you need them, and therefore in your world that means no-one else should need them either…

real people with different requirements, shocker…

Ro you are growing to be a fine little troll arent you. Your comments are neither useful or welcome. ❗

If you have nothing useful to add then please **** orf and try mlehworld instead, i think you’ll fit in nicely there. 🙄

The OP asked for help with a disc brake issue. he didnt ask why you think they are no use for general riding and why fat people are dumb. Im 17st and 6’5″, perhaps you’d like to meet up sometime to discuss the scientific links between waist size and IQ?

Back on topic, sounds like some sort of alignment issue. Either the caliper or perhaps the rotor?

omg, you’re so young! i’ve been conversing with a child. i feel like a paedo…

*rushes off to have shower*

Oh dear.

Dekerfer – Spin the wheel in the frame – hold or secure against the frame a pencil or something similar perpendicular to the disc and about 1-2mm away.

Spin the wheel and see if the distance between the pencil and disc remains constant all the way round – If it does and the disc is solidly mounted must be the caliper – probably the mounting – could be like MartynS (Hi Martyn – Hope alls good) says that it needs facing or maybe just the position needs adjusting.

Once set up they should be OK – in 4 years of using Discs I’ve never had any trouble with any of the brands I’ve used and found for the sort of riding I do they are so much more reliable than V’s when you need it – also don’t collect the Cotswold mud like V’s either!!! 🙂

Ro you are growing to be a fine little troll arent you. Your comments are neither useful or welcome.

strange. ‘cos i think they’re useful, relevant and sometimes insightful. but then i would, wouldn’t i?

The OP asked for help with a disc brake issue.

he did. i think he could reasonably infer from my post(s)that i considered him a ninny for removing v’s in the first place. all he’d done was started to encounter many of the issues related to setting up disc brakes, issues which – to my simple mind – far outweigh their benefits.

i suspect he would have been a happier bunny had he never gone there to begin with.

Im 17st and 6’5″, perhaps you’d like to meet up sometime to discuss the scientific links between waist size and IQ?

i think you’ve already established a clear link between chubbiness, lack of sense of humour and tendency towards aggression. i need to review my chubby-person-failings model…

real people with different requirements, shocker…

did i imply otherwise? all i was suggesting was that instead of following the herd and swallowing every bit of marketing hype thrown in your general direction, you look at the evidence.

yes, ride through gloop for a week and you’ll wear your rims with v’s. but who does that, like constantly? most bikes i saw in the uk were waaaaay over-braked and over-specified for what the users were actually doing with the things. so, fine, you want your mountain bike to resemble a honda mx bike, go ahead. i think it’s silly and, on a forum, i’ll call you on it.

ro – where exactly was i being agressive? i was merely offering the oppertunity for you to discuss your theories further.
Clearly you feel the need to pigeonhole everyone on here rather than keep an open mind……

For your info disc’s DO have a place in normal riding, i’d much rather be over breaked (esp since im a “chubby-person”) than underbraked any time. Discs are generally much more consistant performance wise than V’s (esp when its wet). Dont get me wrong V’s were a HUGE improvement over old style cantis. Surely disc’s are just part of progress? In much the same sense as 27spd drivetrains and 5″ of oil damped suspension travel is.

Ride through gloop for a week?

ro, are you in the UK? Do you ride a bike during the winter at all? And with weather like last summer, the summer too! If you do then please tell us how you manage to not ride in gloop, as I certainly can’t when riding the bridleways near me…

Anyway, back to the main point. As will most disc brake problems, it’s the inital set up which can be tricky, but once set up they can pretty much be forgotten.

Surely disc’s are just part of progress? In much the same sense as 27spd drivetrains and 5″ of oil damped suspension travel is.

i shan’t comment upon your mauling of the english language (whoops! i just did…) but i do take exception to your version of progress.

27 speed drivetrains are beyond silly. you generally have numerous duplicate gearings (jeeze, and i was criticizing your english?) and the mechanisms are far from idiot proof, both in setup and maintenance. give me a six speed rear with a clunky campag derailleur, a two chainwheel front, and i’ll be a simple, happy and reliable little mountain biker, thank you. and i’ll have less worries over my drivetrain than you, and i’ll get up hills faster 🙂

and 5″ travel shocks? get a life. i suspect i’m a failure ‘cos i need 75 mm of front suspension travel. if i needed 5″ – front or rear – i’d give up mountain biking and take up golf. (ok, that reads rather naughtily. i don’t need 5″ of ANYTHING, front or rear).

so what’s progress? well, good carbon frames for one. any *simple*, user serviceable component for another, tyre developments, wheel developments, anything which makes mtb’ing more fun, less hassle, and makes the damn bike lighter.

bigyinn, we live on different planets. long may it remain that way.

ro, are you in the UK?

you don’t know me, do you? i live in viet nam. we’re either under 1m of water or in clouds of dust. gloop lasts for one day in-between these two norms.

I’ve just been out on my V-braked commuter and learnt why I personally really don’t like V’s – especially going down a hill towards a T junction in the wet!!! V. Scary not having the ability to stop as quickly as discs!!!

Dekerfer – keep with it – once set up you’ll be fine!

I suspect ro rides his bike on smooth open fire roads and farm tracks.

You stick with your 12 speed 75mm travel and v brakes, you’ll be just fine old chap.