Viewing 17 posts - 1 through 17 (of 17 total)
  • Bigger rotors or new brakes?
  • Premier Icon RichT
    Full Member

    I’ve always been happy with 180mm rotor front and 160mm rear. However, I now have a P7 29er with Deore M615 brakes on which I use both 29 and 27.5+ wheels and sometimes I feel that braking power is a bit lacking with the plus wheels on. I guess they are so heavy that they take some stopping.
    So do I keep the brakes and go for 203mm front and 180mm rear (this would need new 203mm rotors for both sets of wheels and f+r adapters) or get some 4 pot brakes like the new deore or zee?
    Thanks

    Premier Icon martymac
    Full Member

    I use 180 front 160 rear on 29+ wheels.
    I never ever feel that power is lacking, my brakes are older slx m665.
    I weigh 19 stone and often use the bike loaded with camping gear.
    Are you sure the discs aren’t contaminated with something?
    Unless you’re several stone heavier than me, in which case you might need bigger rotors.

    Premier Icon spawnofyorkshire
    Full Member

    New rotors and adapters can be done for about £40 to £50, realistically your looking at least £100 to improve on M615’s

    If you don’t like the bigger rotors sell them on to make a bit of your money back

    Premier Icon vincienup
    Full Member

    Buy one 203 rotor and some grippier (faster wearing) pads and see what happens. Then either repeat the setup fir the other wheelset or sell the 203 and think again.

    There’s been a couple of big braking force lab tests in magazines over the last couple of years. They make sobering reading for many I’d imagine. The TL;DR version is that if you want actual power then it’s Diretissima, Magura MT7 or Saint in descending order. Zee places quite a bit lower although as I believe they were using recommended rotors with callipers that would have been with RT66’s. The tests were strictly dyno based, not taking user perception into account so looking solely at stopping power not lever feel, modulation etc.

    Premier Icon malv173
    Full Member

    Bigger rotors and new brakes! I upgraded from a 180mm XT M785 to a 203mm Zee up front, and 160mm XT to a 180mm Shimano four pot (keeping the XT lever) out back. Love it. The Zee is really very good.

    I suppose it’s another case of if your budget allows, go for as much as you can justify spending. Bigger rotors will give you more stopping power at a lower cost than new brakes, but you get a lot more power with the four pot brakes – the Zee especially.

    Premier Icon RichT
    Full Member

    Lots of useful tips, thanks guys.

    Premier Icon mark90
    Free Member

    I’d be tempted to give a couple of these a try

    https://www.bike-discount.de/en/buy/shimano-br-mt520-post-mount-d01s-brake-caliper-721662?

    I have just stuck an XT 4 pot on the front of one of my bikes in place of a SLX 2 pot caliper. Only one proper ride on it but so far I’m impressed, more power and more modulation.

    Premier Icon molgrips
    Full Member

    I guess they are so heavy that they take some stopping.

    No, it won’t make any difference. It’s the overall weight that the brakes have to stop, and an extra kg on wheels won’t be noticeable.

    Your brakes are probably either not set up properly or contaminated, or both.

    Premier Icon jjprestidge
    Free Member

    You can use the Deore 4 pot calipers with standard Deore levers – that what I’ve done and it works perfectly. £70 for a set front and rear from Germany.

    These were my upgrades, starting with M6000 Deore:

    203 rotor on the back (already had 203 on the front) – this cost about £20 for a Shimano rotor and a cheapish adaptor.

    Better pads – tried Shimano sintered, but found Ubderbike Kevlars pretty good (opinions vary on these, I know, but I found them very good).

    MT520 4 pot calipers – this made the biggest difference, but mainly in modulation and consistency.

    Replaced standard pads with Saint sintered ones – again, quite a big difference.

    When using Saint pads there’s not much difference, IMO, between these brakes and Saints. They don’t have the cooling fins, and the finned Saint pads don’t fit without modification, but the D type non-finned Saint pads work just as well unless you’re heading to the Alps.

    JP

    Premier Icon bigjim
    Full Member

    I have the 615 on my 29 hardtail, and although I prefer the feel of them compared to xt and slx I’ve had before they don’t have quite the same power. I have zees on my full suss and they are a world apart in power but with great lever feel, nearly kill myself when I ride that after a while on the hardtail.

    Premier Icon bigblackshed
    Full Member

    I recently put some 203mm rotors on my Stooge running 27.5+. Hope Tech X2 brakes with 183mm rotors before. At times, especially on low speed tech I felt I was under braked. With the 203mm rotors I have all the brakes I need.

    Try the rotors first, if you don’t find any difference then move to bigger brakes.

    Premier Icon ransos
    Free Member

    No, it won’t make any difference. It’s the overall weight that the brakes have to stop, and an extra kg on wheels won’t be noticeable.

    Larger diameter wheels require a larger diameter rotor to maintain the same braking force, do they not?

    Premier Icon Poopscoop
    Full Member

    ^^ But surely the braking force required to stop the bigger/heavier wheel is still only a fraction of the force needed to stop the rider and bike weight in total?

    If that’s the case then the larger wheels aren’t a big factor?

    Premier Icon ransos
    Free Member

    If that’s the case then the larger wheels aren’t a big factor?

    I don’t know. I suspect it’s a small difference, but it’s not nothing.

    Premier Icon luket
    Full Member

    At the end of the day your braking force is going to go up proportional to the increase in rotor radius so if you try changing that alone you should see an effect. Whether it’s enough for you is another matter. And clearly your brakes need to be working / not contaminated etc. Also different pads can make a difference.

    Also, it has of course just gone down proportional to the increase in wheel radius you just applied. Two sides of the same fraction.

    Premier Icon jjprestidge
    Free Member

    ^^ But surely the braking force required to stop the bigger/heavier wheel is still only a fraction of the force needed to stop the rider and bike weight in total?

    If that’s the case then the larger wheels aren’t a big factor?

    It’s nothing to do with weight – it’s the extra torque created by the larger diameter wheel that means you need bigger brakes.

    JP

    Premier Icon martymac
    Full Member

    A bigger diameter wheel that’s rotating more slowly . .

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