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Stroke Adjustment on Shimano M486 brakes?

AlanWAlanW Posts: 291
edited December 2010 in MTB workshop & tech
I have just bought my daughter a Scott Scale 70 MTB and very nice it is to.

I can see that there is adjustment for the reach of the levers, which is ideal as she only has tiny hands, (like most 12 years old do!) But can you adjust the stroke on these levers?

There is no air in the system as the brakes do not "pump" up, but the lever does move quite a lot before anything starts to bite on the disc.

My lad has a Scott Aspect 20 with the exact same braking system and they feel completely different to ride, his levers start to "bite" within a slight movement of the levers?

Any ideas?
"You only need two tools: WD40 and duct tape. If it doesn't move and it should, use WD40. If it moves and it shouldn't, use duct tape"

Posts

  • nicklousenicklouse Posts: 81,520 Lives Here
    no and let the pads bed in and the pistons will settle. you could try making the pistons settle faster by pumping the lever without the disc present. (usual issues are present. pistons pop out etc....) or leave the brakes on over night with the lever held back.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • stubsstubs Posts: 5,001
    I had a similar problem on a set of 486 that were on a mates bike. They need bedding in go out and do 10 to 20 hard brakes from speed you should find they work better after a few hard applications. If they are still not right you could do what I did in the end I burped the brakes.

    On Shimano brakes tiny bubbles can get trapped that a normal bleed wont shift. Get the master cylinder top dead level, get someone to hold bars steady then unscrew the master cylinder top and carefully remove the rubber membrane. The oil might drip so catch it with a rag. What you need to do then is pull the brake lever back till it bites then let go and let it flick forward dont return it let the spring do the work. Do this half a dozen times and you might see tiny bubbles rise in the oil, if you do keep on burping the brake till no more tiny bubbles appear. Then for the perfect job you should top up the brake oil but if you were careful not much will have spilt and you will get away with it. Roll the membrane back on so no air gets trapped screw back the cover and hopefully that free stroke should be a lot less.

    I was shown this trick by a guy who works at a Shimano service centre but you can find the technique described in a Shimano tech document if you go looking on the web.

    Its not a guaranteed fix but it has worked for me. Best of luck and if you get yourself and the bike covered in oil dont worry just wash it off with some degreaser its not corrosive like DOT fluid.
    Fig rolls: proof that god loves cyclists and that she wants us to do another lap
  • AlanWAlanW Posts: 291
    Thanks for the info guys, appreciated. The bike hasn't left my garage yet, so I'll get her to do a few rides first then check it again and maybe go down the bleed route?
    "You only need two tools: WD40 and duct tape. If it doesn't move and it should, use WD40. If it moves and it shouldn't, use duct tape"
  • nicklousenicklouse Posts: 81,520 Lives Here
    if the lever feels solid (no pump up) there is NO need to bleed.

    It is just as it is new and not been used yet.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
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