Wet braking distance

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straas

Matt
Location
Manchester
Bit wet this morning, and I've noticed the last few times that my braking distance is significantly worse when wet - to the extent that I ended up not being able to stop in time for a zebra crossing!

I've got kool stop salmon pads, 105 calipers and shimano rs11 wheels. Should my braking really be this bad?
 

T.M.H.N.E.T

Rainbows aren't just for world champions
Location
Northern Ireland
Brake earlier
 

KneesUp

Guru
Define 'this bad' - braking is always worse in the wet because water reduces friction between the braking surface and the pad, and between the tyre and the road.

Is the problem that the wheel isn't slowing, or that the wheel is locking and the bike is skidding?
 
OP
OP
straas

straas

Matt
Location
Manchester
The wheel isn't really slowing, it feels like the brake pad 'grabs' at certain parts of the rim. I've tried feathering the brake first to get rid of excess water but it doesn't seem to help massively.

I was probably 20-30m away from the zebra crossing doing less than 20mph when I started to brake, I was still doing over 5mph when I crossed it.
 

heist

Active Member
Location
Norwich
Bit wet this morning, and I've noticed the last few times that my braking distance is significantly worse when wet - to the extent that I ended up not being able to stop in time for a zebra crossing!

I've got kool stop salmon pads, 105 calipers and shimano rs11 wheels. Should my braking really be this bad?

Breaking is noticably different in the wet. I allow much more time to brake. Not only to allow more space to come to a stop, but also to avoid skidding with one or both of the wheels.

GCN recently did a comparison between rim breaks and disc brakes. They found that there was no difference in performance in the dry, but a major difference in rim braking performance in the the wet. Its worth a watch.
 

mjr

Comfy armchair to one person & a plank to the next
Can you lock your wheels with wet rims when the bike is stopped, before you ride off? That is, either leave the bike in the rain for a bit, or spray the rims with clean water, then pull the front brake lever on firmly and push the handlebars forward and the back wheel lifts up, then pull the back brake lever and push the handlebars forward and the back wheel skids?

If not, I suspect your brakes either aren't adjusted correctly (fiddle with the adjusters to compensate for brake pad wear, or adjust the cable if it's worse than that) or possibly the brake arms have failed somehow. Old stamped steel sidepulls used to crack eventually but I'd be surprised if you've broken recent 105s.

If you can, then it's something else. Have you cleaned your rims and pads recently?
 

mjr

Comfy armchair to one person & a plank to the next
[QUOTE 4887017, member: 9609"]wet roads are one of the biggest contributory factors to accidents, it is amazing how many people just don't slow down, presumably for most 'slippery when wet' is no more than a bon jovi album.[/QUOTE]
Yeah, but it sounds like the brakes aren't effective, rather than a loss of grip on wet surfaces.
 

mjr

Comfy armchair to one person & a plank to the next
From the 'grabbing' it sounds like the rims need a bit of a wash.
It's possible and I guess it's an easy fix to try with very little downside (as long as you don't do something silly like spray lubricant on them to disperse the water) but it could be that the just-too-far-apart pads are catching on some imperfection such as where the joint is in the rim.
 

KnackeredBike

I do my own stunts
I would just second slowing down near obvious hazards, like zebra crossings, in the wet. Even if your brakes were better, there is still more likelihood of gravel and oil washed onto the road along with the water and your front wheel losing grip.
 

biggs682

Touch it up and ride it
Location
Northamptonshire
[QUOTE 4887017, member: 9609"] presumably for most 'slippery when wet' is no more than a bon jovi album.[/QUOTE]

Or a comment about there partner
 

si_c

Guru
Location
Wirral
Give the rims and brake pads a really good clean, and then setup the brakes again so the pads are quite close to the rim.

Depending on how wet it is, I usually allow around 50% more braking distance when using rim braked bikes.
 

T4tomo

Guru
GCN recently did a comparison between rim breaks and disc brakes. They found that there was no difference in performance in the dry, but a major difference in rim braking performance in the the wet. Its worth a watch.
a broken rim is likely to slow you down ;)

there are disc brakes and disc brakes though. No comparison to a set of decent hydrolics and the crap they put on supermarket BSOs. I was adjusting those for a friends kid and they have less stopping power than the 1980's side pull calipers on my old Pug. Purely an ornamental.gimic for the "disc brakes must be good" brigade.
 
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