Brakes not sharp enough

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talksr
Posts: 2
Joined: Sun Jun 02, 2019 20:04 pm

Brakes not sharp enough

Postby talksr » Tue Jun 04, 2019 11:13 am

Hi there,
I recently purchased my new mountain bike from a well known retailer.
It is a lovely bike with suspension just on the forks. They set it all up for me and tested it, but I found the brakes not to be sharp at all.
I assumed it was because it was new, but it has not improved. I have tightened the bolts on the brake leavers on the handle bars, but it has not helped, it just makes it harder to pull the leavers, with no improvement on the sharpness.

If I pulled them both on really hard, the bike would continue moving and the brakes make a creaking noise.
There is zero chance of skidding the tires or getting your back wheel in the air by locking the front wheel... just to give you an idea of the lack of baking.

Can anyone tell me what needs doing? The place I got it from, offers a free tune-up 6 weeks after you bought it (I got it in November), but I don't live near the place and the bike won't fit in my small car.

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steve_sordy
Posts: 1247
Joined: Tue May 29, 2018 08:38 am

Re: Brakes not sharp enough

Postby steve_sordy » Tue Jun 04, 2019 11:31 am

That sounds like you have not bedded in the brakes!

This is an essential process that makes your brakes as sharp as they should be. It requires you to get up to speed and then brake really hard about a dozen times. You will feel the brakes getting better as you do it. Do the front first then the rear. Be very careful that you don't go over the bars as the brakes get better! Keep your weight back when doing the rear brakes as all you will do is to skid the tyre.

Unfortunately, you will have glazed the pads by now and they will not respond to bedding in. Remove the pads and de-glaze them. To do this get some sandpaper 80-120 grit should do, or "medium" and lay it on a flat surface. Put the pad face down onto the sandpaper and rub it across the sandpaper in a circular direction. Apply firm pressure but not light or too hard. Do this until the face is no longer shiny. Refit the pads and go do the bedding in. To get a better idea of how to bed in watch this: https://www.youtube.com/watch?v=BWQxGzHQZVU

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BillyCool
Posts: 653
Joined: Mon May 21, 2018 20:30 pm

Re: Brakes not sharp enough

Postby BillyCool » Tue Jun 04, 2019 12:07 pm

You also have cable disc brakes, which are not brilliant anyway. The cables can stretch and might need adjusting.

Are the levers quite `long` (pulling all the way to the handlebars) or are the pads just not biting enough?

What bolts did you tighten on the handlebars? (photo please)

Hydraulic brakes are more effective and not too expensive to buy if you did want to change them.

Do what Steve said and check the pads first.
"Ride, crash, replace"

mattyfez
Posts: 597
Joined: Wed Jul 23, 2014 10:00 am

Re: Brakes not sharp enough

Postby mattyfez » Wed Jun 05, 2019 08:28 am

Check the inside pad is wound in as close to the disk as possible without rubbing the disk, this is easiest with the bike upside down, wind it in (probably using an Allen key through the other side of the wheel) until you can hear it rubbing on the disk when you spin the wheel and then back it off a tiny tiny bit.

Other easy thing to check is the cable tension, try and see if you can see the outside pad moving when pulling the lever, if there's any delay between pulling the lever and seeing the pad move, you might want to pull the cable through a bit tighter, again ensuring it's not so tight the pad is touching the disk. touching the disk.

Name of the game with mechanical disks is to have the pads as close as humanly possible to the disks.
They also will require periodic adjustment as the pads wear down, the gap between the pads and disk will get bigger resulting in poorer braking over time.

They work by the cable pushing the 'outside' pad into the disk, in turn pressing the disk onto the 'fixed' inside pad so again it's important to have a smaller gap as possible between the pads and disk.

larkim
Posts: 2224
Joined: Mon Oct 24, 2011 08:19 am

Re: Brakes not sharp enough

Postby larkim » Wed Jun 05, 2019 10:49 am

I'd agree that poorly tensioned cable / adjustment of the caliper is likely to be the main culprit of this rather than glazed pads at this stage. Though glazed pads may be the issue, or part of the issue.

I'm so glad I moved onto hydraulic discs, fettling cable ones to get them right was never my strong point!!
2015 Canyon Nerve AL 6.0 (son #1's)
2011 Specialized Hardrock Sport Disc (son #3s)
2013 Decathlon Triban 3 (red) (mine)
2019 Hoy Bonaly 26" Disc (son #2s)
2018 Voodoo Bizango (mine)
2018 Voodoo Maji (wife's)

larkim
Posts: 2224
Joined: Mon Oct 24, 2011 08:19 am

Re: Brakes not sharp enough

Postby larkim » Wed Jun 05, 2019 11:09 am

There are barrel adjusters at the caliper which could help to easily adjust the tension a bit. I'd expect there is also a piston adjuster to allow the pistons to be moved in a little closer to the pads so the gap is as small as feasible.
2015 Canyon Nerve AL 6.0 (son #1's)
2011 Specialized Hardrock Sport Disc (son #3s)
2013 Decathlon Triban 3 (red) (mine)
2019 Hoy Bonaly 26" Disc (son #2s)
2018 Voodoo Bizango (mine)
2018 Voodoo Maji (wife's)

talksr
Posts: 2
Joined: Sun Jun 02, 2019 20:04 pm

Re: Brakes not sharp enough

Postby talksr » Thu Jun 06, 2019 11:01 am

Thank you everyone for your posts. I will try the adjusters by the caliper first. I did do the adjusters on the handlebars but there is hardly any play in them now. When you pull them, they don't want to pull toward the handlebar. I am worried I will snap the cable. Will try on the other end and see if it makes a difference.

larkim
Posts: 2224
Joined: Mon Oct 24, 2011 08:19 am

Re: Brakes not sharp enough

Postby larkim » Thu Jun 06, 2019 14:10 pm

That sounds as if you've got the tension as taught as it can be, so fiddling with the caliper ones will only make it tighter. Visually, are the pads pulled tight in against the disc? Often you can see the disc flex to one side or another when they are pulled like that, especially on cable discs (in my experience) - that would give some evidence of the force being applied. Equally, if you take the wheel out and pull the brake levers, do the pads pull right to the centre?
2015 Canyon Nerve AL 6.0 (son #1's)
2011 Specialized Hardrock Sport Disc (son #3s)
2013 Decathlon Triban 3 (red) (mine)
2019 Hoy Bonaly 26" Disc (son #2s)
2018 Voodoo Bizango (mine)
2018 Voodoo Maji (wife's)


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