Braking Downhill
a1dan
Posts: 17
OK, this sounds a bit dumb, but thought I'd see what people thought...
When descending on a very steep hill (around 20%), at a reasonable speed (no more than 20km/h), would you expect one brake to be able to stop you?
It's not something I've really experimented with before - I'll generally be primarily using the front to control my speed, and feathering the rear as well if I need to slow down significantly. But I tried out of interest today, and realised that I could squeeze either of them as hard as possible and I would just continue at pretty much the same speed, and if I wanted to genuinely slow down, or stop, both were definitely required.
Maybe that's totally normal, I guess I just assumed that you'd ultimately be able to stop with one or the other (tyre-to-road grip allowing) whatever the hill.
If it's of any relevance, the bike in question has mechanical disk brakes. It's still pretty new (just under 1,000km under its belt) and the pads don't look significantly worn.
When descending on a very steep hill (around 20%), at a reasonable speed (no more than 20km/h), would you expect one brake to be able to stop you?
It's not something I've really experimented with before - I'll generally be primarily using the front to control my speed, and feathering the rear as well if I need to slow down significantly. But I tried out of interest today, and realised that I could squeeze either of them as hard as possible and I would just continue at pretty much the same speed, and if I wanted to genuinely slow down, or stop, both were definitely required.
Maybe that's totally normal, I guess I just assumed that you'd ultimately be able to stop with one or the other (tyre-to-road grip allowing) whatever the hill.
If it's of any relevance, the bike in question has mechanical disk brakes. It's still pretty new (just under 1,000km under its belt) and the pads don't look significantly worn.
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Comments
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Your rear brake will do very little, grabbing it hard will only make you skid. So yes, I'd expect one brake to be able to stop me, and it is the front one.0
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...assuming your brakes work. From what you describe there is something wrong with both of them.0
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Yeah, to be clear the issue was entirely with braking power, there was no loss of traction on the road. And as you suggest, I would expect to be able to brake hard enough that the wheels lock / skid... especially with the rear. I feel like on my previous old bike, with rim brakes, that would have been the case. It was a pretty clean, grippy bit of tarmac, mind.
Is there anything straightforward I can do to check them? if I try and turn the wheel by hand while squeezing the brake fully, I almost can't, but it will just about move if I really put some force into it. Should it be absolutely impossible to turn it?0 -
I know nothing about disc brakes I'm afraid but I'm sure someone will pitch in. What make and model do you have?0
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Yeah, Tektro MD-C510.
I guess it could just be either / both of pad wear or cable stretch after the bike's first 1,000km or so - it's very hilly round here so they get used plenty! I'll have a look at adjusting before my next ride.0 -
Did you bed in the pads on their first use? Glazed pads could be a problem but you should be able to stop with just one brake and the front is normally more powerful than the rear.
If you didn't bed the pads in, then remove them sand them a little to take the top layer off and put them back, then ride up and down the road a few times with quick bursts and grab a handful of brake a few times.
Failing this google how to adjust your particular brakes and go from there.
If you are in anyway uncomfortable with working on your brakes then take a visit to your LBS and they should be able to diagnose and fix.0 -
No, didn't bed them in, so will give that a go. There was a bigger gap than expected between pad and rotor when I checked, so I gave that a couple of turns until they were nearly touching (seems to only adjust the fixed pad, not the moving one... guess that's normal?). Not had a chance to get out on the street and give it a go yet.
Tbh, I think the front brake would stop me anyway on any hills within a mile or so of my house... it was an extremely steep one I was going down when I did my test. I guess if it seems fine on my street I'll head back up to the same spot and try there!0 -
You have to consider the dynamics of that gradient/speed and braking.
The braking action throws your weight forward (even if you think you don't leave the seat). That lifts weight off the rear wheel meaning it will lock up very quickly making it largely redundant. It puts weight onto the front wheel (it has to go somewhere) making the front wheel much more efficient at stopping you as long as you have traction on the road surface and you are going (mostly) in a straight line.
I learned that almost the hard way on my motorbike where it was further complicated by suspension.
The dynamics are the same.1 -
Yep, would always very much rely on the front brake, especially on the downhill, for exactly the reasons you describe... cycling / biking 101!
Though as I mentioned, while testing them out even the rear didn't seem to be able to give enough braking power to lock up!0
