Is disc size all that important

Mark Elvin
Mark Elvin Posts: 997
edited June 2010 in Commuting chat
I currently have 203mm front & 180mm rear discs.

In an effort the shave yet more weight from the commuter/MTB ride I'm considering dropping in disc size to 160mm F&R, I'm determined to get the weight under 20lb eventually, no reason other than I like the challenge.

Question is, would I REALLY notice the difference in disc size, brakes are 2010 Shimano XT discs.
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Comments

  • lost_in_thought
    lost_in_thought Posts: 10,563
    Ooooooh yes, definitely.

    Very much so.

    *I have no idea what I'm talking about

    **actually I have no idea what you're talking about either
    FCN 7/1
    Viner Maxima, Tifosi CK7, Giant Bowery, Old commuter.
  • jonginge
    jonginge Posts: 5,945
    I have no clue either. You should get a road bike. What was the question?

    Just in case you aren't aware of them: http://weightweenies.starbike.com/forum/
    They may just help in your quest
    FCN 2-4 "Shut up legs", Jens Voigt
    Planet-x Scott
    Rides
  • Mark Elvin
    Mark Elvin Posts: 997
    edited June 2010
    ..
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  • neil_sheehan2000
    neil_sheehan2000 Posts: 529
    If all you're using the bike for is commuting, then no, I would say that it won't make a significant difference. You may notice the difference of having smaller disks initially, but you'll get used to it and you'll definitely still be able to stop- may just have to tug a bit harder on the brakes.

    If you're using it for MTBing as well though, then that may be a different story...

    p.s. changing disk size isn't going to lose you all that much weight though, is it?
    Meta
  • supersonic
    supersonic Posts: 82,708
    Larger discs can reduce feel of the brakes. Ad the brake will lock up earlier into the lever travel, and with less lever force. Smaller rotors with some systems can have benefits.
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  • Mark Elvin
    Mark Elvin Posts: 997
    neil_sheehan2000 wrote:

    p.s. changing disk size isn't going to lose you all that much weight though, is it?

    If I have smaller discs I also have smaller adaptors so it's a small, but definate change.

    I'm really squeezing every ounce I can out just to see how low I can get the weight.
    2012 Cannondale Synapse
  • nicklouse
    nicklouse Posts: 50,675
    203 is really over kill for a commute. it is overkill for most XC bikes.160/160 should be fine.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • El Capitano
    El Capitano Posts: 6,401
    Mark Elvin wrote:
    I'm really squeezing every ounce I can out just to see how low I can get the weight.

    What's the bike?
    1 2 3 4 (Dead)5 6
  • Mark Elvin
    Mark Elvin Posts: 997
    2002 Cinder Cone Frame, currently standing at a smidge under 21lb.
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  • Rich158
    Rich158 Posts: 2,348
    You will notice a difference, especially if you go down to 160mm from 203. It should be fine for commuting though, most of us get away with the crappy brakes on our road bikes so any disc will be better than the brakes most of us run
    pain is temporary, the glory of beating your mates to the top of the hill lasts forever.....................

    Revised FCN - 2
  • El Capitano
    El Capitano Posts: 6,401
    Mark Elvin wrote:
    2002 Cinder Cone Frame, currently standing at a smidge under 21lb.

    Just seen the pics in the Commuter Bike thread, very nice bike indeed.
    Rich158 wrote:
    You will notice a difference, especially if you go down to 160mm from 203. It should be fine for commuting though, most of us get away with the crappy brakes on our road bikes so any disc will be better than the brakes most of us run

    That would depend on how often you clean the rotors/pads. I get quite a lot of "road grime" on my commuter bike(s). Especially when riding in the winter, where the bike also get's lubed/sprayed with WD40/GT85 etc. It was the main reason I got the CX bike with caliper brakes rather than disks. I know at the end of a wet ride, I can just spray the whole bike and put it away in the shed.

    That said, when the roads are wet, disk brakes are probably the most effective... :?
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  • itsbruce
    itsbruce Posts: 221
    El Capitano wrote:
    That would depend on how often you clean the rotors/pads. I get quite a lot of "road grime" on my commuter bike(s). Especially when riding in the winter, where the bike also get's lubed/sprayed with WD40/GT85 etc. It was the main reason I got the CX bike with caliper brakes rather than disks. I know at the end of a wet ride, I can just spray the whole bike and put it away in the shed.

    That said, when the roads are wet, disk brakes are probably the most effective... :?

    Not if you spray Teflon all over them! Don't be doing that; white spirits is best for cleaning discs.
    Charge Mixer (2010)
    Schwinn Madison (2009)
  • mudcovered
    mudcovered Posts: 725
    Mark Elvin wrote:
    I currently have 203mm front & 180mm rear discs.

    In an effort the shave yet more weight from the commuter/MTB ride I'm considering dropping in disc size to 160mm F&R, I'm determined to get the weight under 20lb eventually, no reason other than I like the challenge.
    Wow. That seems seriously over braked. My MTB has a 185 rotor on the front and a 160 on the rear. Good enough for UK trail centre trails and my offroad trips to Spain and the Yorkshire Dales. 160/160 will be more than enough for road use although if you intend to keep using the bike offroad it would be worth going to 180 front/160 rear.

    Mike
  • Mark Elvin
    Mark Elvin Posts: 997
    mudcovered wrote:
    Wow. That seems seriously over braked. My MTB has a 185 rotor on the front and a 160 on the rear. Good enough for UK trail centre trails and my offroad trips to Spain and the Yorkshire Dales. 160/160 will be more than enough for road use although if you intend to keep using the bike offroad it would be worth going to 180 front/160 rear.

    Mike

    My thought when building was that you can never have enough brake, part of me still feels this way, the feel at the lever is superb.
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  • JonEdwards
    JonEdwards Posts: 452
    What tyres are you using?

    If you've got skinny slicks on, then you're WAY overbraked - you'll be able to lock your front wheel far too easily in the wet.

    If you're soley using the bike for commuting, then go 160/140. You'll still be able to stop plenty quick enough. Even off road, I only use 200s on the big bikes - 180/60 is more than enough for even alpine xc stuff. If you want light rotors, then the Hope floating ones are a bit lighter than normal ones and make a nice "plink" noise when they cool down after heavy use, or check out the Ashima air rotors.
  • nicklouse
    nicklouse Posts: 50,675
    itsbruce wrote:

    Not if you spray Teflon all over them! Don't be doing that; white spirits is best for cleaning discs.

    Sorry but NO. it is OIL based and leaves a lovely residue that results in pads that are nicely contaminated.

    use an Alcohol based cleaner (Meths/IPA) or proper cycle disc cleaner.

    go on clean your windows with either and see what leaves the crap behind.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Mark Elvin
    Mark Elvin Posts: 997
    JonEdwards wrote:
    ...... heavy use, or check out the Ashima air rotors.

    That's what I have at the moment, very happy with them.

    I'm on semi slick, it's a commuter/off road bike, but I'm not that hard on it to be fair.
    2012 Cannondale Synapse
  • El Capitano
    El Capitano Posts: 6,401
    nicklouse wrote:
    itsbruce wrote:

    Not if you spray Teflon all over them! Don't be doing that; white spirits is best for cleaning discs.

    Sorry but NO. it is OIL based and leaves a lovely residue that results in pads that are nicely contaminated.

    use an Alcohol based cleaner (Meths/IPA) or proper cycle disc cleaner.

    go on clean your windows with either and see what leaves the crap behind.

    Meh, everyone knows the best way to clean your rotors is to put them in the dishwasher.

    Obviously its a good idea to remove them from the wheels first.

    Its also a good idea not to let the wife/girlfriend/booyfriend/husband/civil partner/house mates etc see you do this.

    It is also a good idea to deny all knowledge of why the dishwasher is broke because there's all this black oily residue in the pump... :oops:
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  • itsbruce
    itsbruce Posts: 221
    nicklouse wrote:
    itsbruce wrote:

    Not if you spray Teflon all over them! Don't be doing that; white spirits is best for cleaning discs.

    Sorry but NO. it is OIL based and leaves a lovely residue that results in pads that are nicely contaminated.

    use an Alcohol based cleaner (Meths/IPA) or proper cycle disc cleaner.

    go on clean your windows with either and see what leaves the crap behind.

    Ack, that's the right name. What I purchased just says "Isopropyl alcohol" on the can.
    Charge Mixer (2010)
    Schwinn Madison (2009)
  • ride_whenever
    ride_whenever Posts: 13,279
    El Capitano wrote:
    nicklouse wrote:
    itsbruce wrote:

    Not if you spray Teflon all over them! Don't be doing that; white spirits is best for cleaning discs.

    Sorry but NO. it is OIL based and leaves a lovely residue that results in pads that are nicely contaminated.

    use an Alcohol based cleaner (Meths/IPA) or proper cycle disc cleaner.

    go on clean your windows with either and see what leaves the crap behind.

    Meh, everyone knows the best way to clean your rotors is to put them in the dishwasher.

    Obviously its a good idea to remove them from the wheels first.

    Its also a good idea not to let the wife/girlfriend/booyfriend/husband/civil partner/house mates etc see you do this.

    It is also a good idea to deny all knowledge of why the dishwasher is broke because there's all this black oily residue in the pump... :oops:

    Luddite, try giving them a soak in an ultrasonic bath full of ipa...
    Neeermad
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    456 lefty
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  • Kiblams
    Kiblams Posts: 2,423
    I would personally say that 160 is a little OTT for road riding, I find that when I take the mountainbike (160/160) to work on the roads I can lock the front wheel very easily especially in the wet, which is never a good thing!
    HandsomeDog - OrangeCommuter
  • Mark Elvin
    Mark Elvin Posts: 997
    Kiblams wrote:
    I would personally say that 160 is a little OTT for road riding, I find that when I take the mountainbike (160/160) to work on the roads I can lock the front wheel very easily especially in the wet, which is never a good thing!

    I've never had a problem with locking brakes on any terrian on any bike, I guess I must just have "the feel"!!!!!!!!
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  • ride_whenever
    ride_whenever Posts: 13,279
    Kiblams wrote:
    I would personally say that 160 is a little OTT for road riding, I find that when I take the mountainbike (160/160) to work on the roads I can lock the front wheel very easily especially in the wet, which is never a good thing!

    Sounds like rubbish brakes tbh, with small rotors you get better modulation so you should have no trouble controlling it. I've never had any issues with discs on the road even at high speeds.
    Neeermad
    Carbon 456
    456 lefty
    Pompino
    White Inbred
  • Kiblams
    Kiblams Posts: 2,423
    ride_whenever wrote:
    Sounds like rubbish brakes tbh, with small rotors you get better modulation so you should have no trouble controlling it. I've never had any issues with discs on the road even at high speeds.

    Should probably mention that's with slicks, have only ever locked the front with MTB tyres on when messing about on ice.

    But the point is that 160 is more than enough power, if they can stop my 16.7st bulk easily, you lanky lot should have no issues :wink:
    HandsomeDog - OrangeCommuter
  • ride_whenever
    ride_whenever Posts: 13,279
    Fair enough, with skinny slicks you have buggerall contact with the road. I tend to run 2.3" slicks on my mtb when doing exclusive road work, really really fun and still silly fast.
    Neeermad
    Carbon 456
    456 lefty
    Pompino
    White Inbred
  • Kiblams
    Kiblams Posts: 2,423
    edited June 2010
    ride_whenever wrote:
    Fair enough, with skinny slicks you have buggerall contact with the road. I tend to run 2.3" slicks on my mtb when doing exclusive road work, really really fun and still silly fast.

    Having very rigid forks (Certified for use on offroad tandems) didn't help on that front either :?

    Yeah I have had my eyes on ringworms and big apples for a while now, do you find alot of drag?
    HandsomeDog - OrangeCommuter
  • ride_whenever
    ride_whenever Posts: 13,279
    Very very little with tioga FS100 (now the krad IIRC), marginally more than 1" fatboys but then the smooth ride of the big tyres makes up for that as you're battered less. Balloon tyres are awesome (says the guy with 20mm pro3 on his roadie :roll: )

    Obviously the harder the compound the faster they go, but basically there is f-all difference between wide and narrow slicks. The hookworms are massively heavy, i'm about to get some KHE street tyres, only a 2.1" but really really really really light and warrantied to ridiculous pressures. Check out this video to see how much a khe tyre can take!!!!!!
    Neeermad
    Carbon 456
    456 lefty
    Pompino
    White Inbred

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