CityCyclingEdinburgh Forum » Debate!

Rim versus Disc

(29 posts)
  • Started 9 years ago by I were right about that saddle
  • Latest reply from I were right about that saddle

  1. I were right about that saddle
    Member

    I was a disc brake sceptic for many years, considering that a 700c rim is just, in so many ways, just a 650mm diameter brake disc.

    The current iteration of my bicycle allows for investigation of this notion and that's just what I did on the way home from the pub last night. The front sports a Shimano SLX brake on a 160mm rotor. The rear has a Magura HS11 hydraulic rim brake. Both brakes are quite capable of locking up the wheels in the dry, but in last night's heavy drizzle I was startled to notice the drop in braking power on the rear.

    It's really, really obvious when you have one disc brake and one rim brake.

    Posted 9 years ago #
  2. unhurt
    Member

    I was also an unbeliever and then I got a bike with discs and - oh my! It really does STOP. Even with vast amounts of luggage strapped to it.

    Posted 9 years ago #
  3. chdot
    Admin

    Never really had a problem with rim brakes since the advent of dual pivots - esp 105s.

    Most of my bikes are 'pre disk' so not able to easily 'try'.

    What are people's impressions of need to replace pads v blocks - time/mileage?

    Posted 9 years ago #
  4. steveo
    Member

    I don't think I've ever worn through a set of disc pads but I run quite hard sintered pads and they're on my mtb which doesn't get much use.

    I'm not on my first set of pads but I managed to ruin two sets by contaminating them with mineral oil which would very difficult to do with rim pads.

    Posted 9 years ago #
  5. Baldcyclist
    Member

    "What are people's impressions of need to replace pads v blocks - time/mileage?"

    I do find my Avid BB7 pads require changing more than standard blocks did.

    Annoying in that there is still plenty pad, but the wee spring thing means that starts to rub on the disk before the pad is fully worn.

    They do stop really wet in the wet though.

    Posted 9 years ago #
  6. I were right about that saddle
    Member

    @chdot

    My brother-out-law's road bike I borrowed the other day has Decathlon brand dual pivots (I suspect Tektro in reality) and on a bumpy 20% descent they were just too weedy, even in the dry.

    Posted 9 years ago #
  7. wingpig
    Member

    I could have tried on the Kaffenback's rear as the frame came with canti bosses whilst the swappable dropout had disc-style protrusions and holes, but it would also have required a suitable rear hub and brake and either a different rack or doing without the rack for a bit.

    Posted 9 years ago #
  8. steveo
    Member

    When we done the Coast 2 Coast the other year there were a couple of steep descent ending in T junctions that really really taxed my brakes (105's). My buddy just had to drag his the whole way down after he nearly went straight into the wall at the end of the road on one decent such were his brakes (tektro dual pivot I think). On the same trip I managed some significant wear to a brand new set of pads coming off Winlatter into Keswick.

    By comparison coming off the Leicht a couple of years earlier I never felt my brakes had any trouble despite my far heavier load and a couple of unexpected, very sharp corners near the top.

    Posted 9 years ago #
  9. Roibeard
    Member

    I ran rim brakes on my commuter for long enough, and replaced quite a few wheels as a consequence of rim wear. Yes, I could have had them rebuilt, but that wasn't economical compared to simple replacements.

    Now I'm running more expensive hubs, have learnt how to wheel build, and have switched to disc brakes for the main.

    The braking surface stays dry, and the pads and surface can be optimised for braking rather than having to balance the structural requirements of a rim.

    I've found the hydraulic disc brakes to require less maintenance for optimal braking too - they seem to actually be self adjusting, rather than the constant tweaking demanded by v-brakes.

    I'd try and specify hydraulic disc brakes now, but wouldn't be put off by a bike that met my needs which only offered rim brakes.

    Robert

    Posted 9 years ago #
  10. I were right about that saddle
    Member

    @Roibeard

    I suspect the Maguras will grind my rear rim to death in no time. They're so powerful they flex the seat stays.

    I think it was you that warned me off cable operated disc brakes. Subsequent experience of other people's bikes has shown this to be sound advice - even the Avid ones are not well made.

    Posted 9 years ago #
  11. wingpig
    Member

    How often do you need to wash a rear rotor?
    I would not expect a rotor to entirely escape becoming befilthed with greyish-brown road-matter just because it was not on the driveside and not almost touching the road. How well do they cope with wee particles of tenacious gunk on the braking surface or building-up on the leading edge of the pad?

    Posted 9 years ago #
  12. unhurt
    Member

    Just remembered my one issue with discs - when mine get wet (no matter how often I wipe them clean) the rear one squeals like a murder of rats. On the other hand, had the bike serviced post-transCanada trip and apparently I STILL don't need to replace the brake pads. This seems near-miraculous to me...

    Posted 9 years ago #
  13. I were right about that saddle
    Member

    @wingpig

    Pretty much self-cleaning are discs. You can roast them with a blow-lamp if they get to squealing.

    Posted 9 years ago #
  14. Murun Buchstansangur
    Member

    Good points here - on one of my 2 main bikes, I have cable operated disc brakes. Bit squealy, and require abnormal (IMO) amounts of adjustment to prevent having to grab handfuls of brake to get decent stopping. I may need to explore different pads. Not a fan, unless in a deluge.

    Posted 9 years ago #
  15. jdanielp
    Member

    I have Tektro mechanical disc brakes on my semi-retired hybridised EBC MTB. It has covered 15,000 miles, during which time the rear brake pad was replaced once... I got into the habit of cleaning the discs using Muc-Off disc brake cleaner which it now requires regularly to avoid squeakiness. Mechanical disc brakes do not self-adjust! My new Charge hybrid has Shimano hydraulic disc brakes which are far more effective, are quiet in all but the wettest weather (yet to use Muc-Off) and do self-adjust!

    Posted 9 years ago #
  16. acsimpson
    Member

    I replaced by BB5's with TRP Hy/rd's last year.

    The BB5's were a pain with constant adjustment of both the cable tension and calipers required to keep them functioning. The disc themselves also had a habit of becoming slightly warped due to only one pad moving and forcing the disc to bend into the other pad, this isn't a problem with all cable discs but something to be aware of.

    The Hy/rd's on the other hand are hybrid brakes with cables to the caliper but rather than moving the pads directly it triggers a hydralic mechanism. This allows the pads to be self adjusting and other than one pad replacement I have done approximately no maintenance on them since fitting. The braking performance is great but the one drawback over the Avid Juicy's on my MTB is that they do vibrate a bit under heavy braking.

    The other brake I tried briefly was the TRP paraboxes they go one step further than the hy/rds and put a hydraulic reservoir under the headset, minimising the length of cable. I preferred this to the hy/rd's but the first two sets I bought came with contaminated pads and they no longer make them so sadly I couldn't use them.

    Posted 9 years ago #
  17. I were right about that saddle
    Member

    @acsimpson

    What's the advantage of mixing cable and hydraulics? Do you not wind up adjusting the cables? Can't be the weight is it?

    Posted 9 years ago #
  18. amir
    Member

    My weekend bike doesn't really have anything like the rim wear that my winterbike/commuter gets. The brakes (dual pivot) also seem fine for road use. However I can definitely see a benefit for commuting.

    Is the issue of heat dissipation with hydraulic brakes on long descents an issue? (I remember something like this occurring in the lakes after Wrynose and Hardknott in my Metro - a bit alarming!)

    Disc brakes are heavier aren't they - does this matter? Rim brakes are easy to maintain in the middle of nowhere - are disc brakes?

    Posted 9 years ago #
  19. acsimpson
    Member

    Assuming you're aware of the advantages of hyraulic over cable then the advantage of the mixture is that you can run them on drop handle bars using standard road/cx brake pulls.

    With a couple of very expensive options there isn't a fully hydraulic drop brake solution out there yet.

    You may have to adjust the cables if you fit new cables to maintain optimal performance but as brake cables stretch less than gear cables and I fitted mine to existing cables I haven't had to do this. Another benefit of the parabox was a much shorter cable run minimising the effect of cable stretch/wear.

    Posted 9 years ago #
  20. I were right about that saddle
    Member

    @acsimpson

    Of course! Presumably the revoking of the UCI ban on disc brakes will see a flood of drop-bar compatible hydraulic kit.

    @amir

    Brake discs can happily get to red heat - it's what they're for.

    Posted 9 years ago #
  21. crowriver
    Member

    I have three bikes with disc brakes:

    1 x tandem with front and rear discs (200mm rotors)
    1 x tandem with front and rear rim brakes, plus a rear disc brake*
    1 x cargo bike with front and rear discs (160mm rotors)

    All the discs are cable actuated. On the cargo bike I sometimes get annoying disc rub on the front brake, but squeezing the lever a few times gently while riding usually fixes this (Avid BB5s)

    That fully disc braked tandem brakes beautifully even with very heavy loads. Haven't put the rim braked tandem through that test yet...

    I also have a Pashley folding bike with hub brakes: those are really the most weatherproof brakes ever. A bit more 'spongy' in feel than discs or rim brakes but they do stop you: guaranteed.

    I have another folding bike with a rear coaster brake plus v-brake up front. Mixed results with that, as the rear is prone to locking and skidding...

    The rest of the current fleet (not including kids' bikes or Mrs crowriver's bikes) are rim brakes: one on v-brakes, one on cantilever brakes, the rest on double pivots except for the BSA 20 which is side pull calliper old style on chromed steel rims...

    Double pivots are good for road or audax style bikes, stopping power is fine and modulation to trim speed also good. Similarly cantilevers give an element of modulation which v-brakes don't really.

    Not yet managed to wear out a rim, but that may be due to bike rotation and lack of a regular commute via bike...

    * - Yes, a second tandem. It's t+1, similar to n+1 but with twice as many saddles and sets of cranks.

    Posted 9 years ago #
  22. steveo
    Member

    I did manage to warp a rotor one winter after some rapid cooling due to very fast deceleration and then the rapid cooling due to the cold weather. Rinse repeat over a long morning.

    Posted 9 years ago #
  23. Greenroofer
    Member

    I have Shimano hydraulic disc brakes on my commuter bike. Strava tells me that I get about 1,800 miles out of each set of pads. In between replacing the pads, I do no maintenance whatsoever (that's nothing, nada and zilch) to the brakes. They self-adjust, they 'just work' in rain and snow and generally are no trouble.

    I will get them on my next commuter bike too (along with a belt drive)

    Posted 9 years ago #
  24. gembo
    Member

    I find putting my left foot on to the Tarmac can often assist when my cantis are getting worn. I have worn through one set of rims since 2001, see threads passim when the infamous Mr Freewheelin told me the rim had at most a fortnight left.

    I suppose discs are inevitable? My dishwasher has a blockage at mo so it is not on pending inquiry, my kids really do not like washing or drying dishes. Once you buy a dishwasher there is no going back. Same for discs?

    Posted 9 years ago #
  25. algo
    Member

    I find the greater modulation of discs means it is much easier to apply as much pressure as you can without locking up. It is still possible to lock up of course but it's much more controllable. In the dry I don't think the braking ability is much different except for long braking durations where the discs don't suffer so much from brake fade (I think). I have ice-tech rotors which are designed to dissipate heat quicker - useful coming down a long hill with a trailer. I also have TRP spyre cable operated calipers which actuate both pistons (unlike BB7 etc) and I rate them.

    Posted 9 years ago #
  26. le_soigneur
    Member

    Though the anecdotal comparison between a front disk and a rear rim brake (that started this thread) is not valid,
    the conclusion from a valid comparison (GCN) is the same.

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    Posted 9 years ago #
  27. amir
    Member

  28. le_soigneur
    Member

    Definitely could be a weapon for/against wheelsuckers on a wet NEPN, if one has rotors and the other has rims :)

    Posted 9 years ago #
  29. I were right about that saddle
    Member

    "Though the anecdotal comparison between a front disk and a rear rim brake (that started this thread) is not valid"

    I'm sure you didn't mean to put me back in therapy.

    Posted 9 years ago #

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