Wet brakes/rims.. No stopping power!

requiem

hi there,

so, locked my bike up today in the fairly heavy rain, and once i got back on it I quickly noticed by brakes were almost entirely unresponsive!! there was just no grip or 'catch' on the rims. Quite unnerving!!

After 30 seconds or so of using and releasing of the brakes, the front one became effective while the rear displayed only a marginal improvement..

On the front I have Kool Stop Tektonics (3 compounds, salmon, grey and black) and on the rear I have Kool Stop dual compound (salmon and black), I should probably mention these are V-brakes. Im quite concerned as the brakes I am using are supposed to be particularly good for wet weather. Could it be my rims are contaminated?

Many thanks

car.crash

Why not wipe the rim with some degreaser to be sure?

Secteur

even with heavy rain they shouldnt be "completely unresponsive for 30 seconds" unless there was grease on there, but then that wouldn't just suddenly happen - you'd have had that problem since the grease got on there (e.g. whilst using bike spray etc)

having said that, road bikes dont stop very well in the wet I have found, and I have salmon kool stops.

suppose it depends how fast you were going when trying to brake, and how heavily you were applying them.

try "feathering" the brakes to disperse the water before using them, and go extra slow / carefully in the wet.

AndyOgy

car.crash wrote:

Why not wipe the rim with some degreaser to be sure?

+1

Wipe down the rims and pads with a good degreaser. If you don't have any, Johnson's Baby Wipes are strangely effective.

How are your cable tensions. You'd be amazed how many bikes I see where the rider thinks that everything is fine. But the levers can be pulled right back to the bars.

On a well set up rim brake system, I'd only expect to lose between 10% and 25% braking performance in the wet. Although, you should watch out for that sudden increase in braking performance when the wet wheels complete one revolution under braking and the brake pads wipe the rim almost dry.

desweller

How old is your bike? This sounds like the sort of response I'd expect from a steel rim.

requiem

Thanks for the replys all

my bike is a 2011 sirrus.. indeed if there was grease on the rims I would have noticed this before.. very strange.

Perhaps the grey aluminum powdery stuff that develops in wet conditions stayed on the rims while it was locked up and turned slightly sludgey? Have also noticed that the built-in 'heel in' of the rear pads has not been compensated for by myself in the fitting of these brakes.. Could a full initial contact or a toe in on the rear brakes help them bite in these conditions?

Thanks again

balthazar

requiem wrote:

Thanks for the replys all

my bike is a 2011 sirrus.. indeed if there was grease on the rims I would have noticed this before.. very strange.

Perhaps the grey aluminum powdery stuff that develops in wet conditions stayed on the rims while it was locked up and turned slightly sludgey? Have also noticed that the built-in 'heel in' of the rear pads has not been compensated for by myself in the fitting of these brakes.. Could a full initial contact or a toe in on the rear brakes help them bite in these conditions?

Thanks again

Brakes will wear into a "toed-in" pattern naturally, as the wheel rotation twists the caliper arms, wearing the trailing edge of the pads more. There's no reason to pre-empt this by setting "toe-in" as many still do. It only means the pads will wear out even faster, and makes adjustment trickier. Set your pads square to the rim.

With the rims and pads clean and degreased, water should only present a minimal cost to braking. In the first pass of the wheel, the pad squeegees water from the rim surface, which is thereafter mostly dry. That is only about 2-3 metres of travel, which is inconsequential, especially at speed. Loss of grip is a much greater problem.

If your brakes are still as bad as you describe after this, there is an undiagnosed problem. However, I usually find it's overspray from spray lube.

carl_p

I think it's all part of riding in the wet tbh. 2 inches of wet rubber on a wet rim isn't going to cause much friction is it? I use the Koolstop salmon brake pads which are supposed to be for wet weather and don't find them that much better than regular pads.

I know what you mean about the grey sludge and you do need to give the rims a good clean with a solvent to get it all off, otherwise it will reappear quickly the next time it rains.

Don't bother with toe-ing in, I think it's supposed to stop brakes juddering and personally I like as much rubber on the rim as possible, especially in the wet. As said you might want to check the gap between the pads and the rim.

TuckerUK

A couple of things:

I've found asymmetric pads (i.e those with a longer leading end) work perfectly for me with zero toe. I use cartridge pads incidentally.

There can be a lot of greasiness on the road, and therefore in any road spray, when it rains after a dry spell. Just think of all the tyre compound, fuel leaks, oil leaks, oily diesel fumes, oily 2-stroke fumes, etc. that get deposited on our roads.

geoff_ss

We have a hydraulic rim brake on the front of our Cannondale tandem and a mechanical disc at the back so it's easy to see the difference in wet conditions. The disc brake is almost unaffected but even the usually excellent rim brake on the front takes a while to bite effectively. Disc brakes are definitely better.

Incidentally. I've never ridden any bike which inspires so much confidence in braking as this one. The long wheelbase means the back wheel stays where it should - behind the front one and on the road.

When I first started cycling seriously in 1970s my bike had steel rims and the brakes were next to useless even with blocks with leather inserts which were supposed to help. Building a new pair of wheels with alloy rims helped a lot but rim brakes always take a while to work in the wet. Not 30 seconds, certainly, but even a second can seem an eternity in an emergency. A way round it is to apply the brakes regularly and gently to keep the rim dry.

fossyant

Just keep the rims clean. It will prolong their life. The grey sludge is a mix of brake compound and your alloy rims. Needs to be washed off after rides. Clean rims/blocks prolong rim life. Ride with gritty rims, you'll eat your rims.

deadlegs

I spent 50 miles crapp1ng myself in the rain yesterday. Absolutely no braking with Swiss stop greens.

After reading this I'm going to give the rims & pads a good clean. I can get a bit overexcited with the bike spray.

Pure fear on every descent mixed with a hangover was no fun  :shock:

Fenred

Geoff_SS wrote:

We have a hydraulic rim brake on the front of our Cannondale tandem and a mechanical disc at the back so it's easy to see the difference in wet conditions. The disc brake is almost unaffected but even the usually excellent rim brake on the front takes a while to bite effectively. Disc brakes are definitely better.

Incidentally. I've never ridden any bike which inspires so much confidence in braking as this one. The long wheelbase means the back wheel stays where it should - behind the front one and on the road.

When I first started cycling seriously in 1970s my bike had steel rims and the brakes were next to useless even with blocks with leather inserts which were supposed to help. Building a new pair of wheels with alloy rims helped a lot but rim brakes always take a while to work in the wet. Not 30 seconds, certainly, but even a second can seem an eternity in an emergency. A way round it is to apply the brakes regularly and gently to keep the rim dry.

The voice of experience....V useful post!! In essence discs are very efficient due to obvious reasons...Keep rim brakes feathered and dry.

balthazar

Geoff_SS wrote:

W
Incidentally. I've never ridden any bike which inspires so much confidence in braking as this one. The long wheelbase means the back wheel stays where it should - behind the front one and on the road.

Geoff- forgive me for asking you to be a guinea pig- but what happens when you brake maximally on a tandem? On a solo bike, with slick tyres on smooth dry road, I know the rider goes over the handlebars (no matter what precautions he may take) before the front tyre slips. But I cannot picture a loaded tandem endo-ing. Have you any experience? I'd bet on fork or frame failure before a slide, but that's very much a guess.

geoff_ss

No problem, Balthazar.

You're never likely to over the handlebars on a tandem simply because of the length and the extra weight of the stoker on the back. However all the other tandems we've owned have had brakes which left a little to be desired. There was never much chance of going over the top because the brakes weren't powerful enough.

The Cannondale replaced a handbuilt 531 made for us by a local builder. It had Shimano cantilever brakes front and rear which were usually OK but couldn't bring the bike to a complete halt on a steep descent like (say) Park Rash or Long Mynd. It also had a Maxicar drum brake which was useless because the drum resembled a cocoa tin - rather like the brakes on vintage motorcycles I've ridden.

The Magura hydraulic rim brake on the front and the Avid BB7 disc at the back will stop us on the Cannondale quicker than a solo. That may be partly to do with the fatter tyres. It's very stiff and handles well on fast descents, too, although I'm afraid the weight of 141 years on the two saddles makes it a bit slow on the climbs The back brake is a bit noisy (squeal) when the disc is damp but it still works OK

balthazar

Geoff_SS wrote:

No problem, Balthazar.

You're never likely to over the handlebars on a tandem simply because of the length and the extra weight of the stoker on the back. However all the other tandems we've owned have had brakes which left a little to be desired. There was never much chance of going over the top because the brakes weren't powerful enough.

The Cannondale replaced a handbuilt 531 made for us by a local builder. It had Shimano cantilever brakes front and rear which were usually OK but couldn't bring the bike to a complete halt on a steep descent like (say) Park Rash or Long Mynd. It also had a Maxicar drum brake which was useless because the drum resembled a cocoa tin - rather like the brakes on vintage motorcycles I've ridden.

The Magura hydraulic rim brake on the front and the Avid BB7 disc at the back will stop us on the Cannondale quicker than a solo. That may be partly to do with the fatter tyres. It's very stiff and handles well on fast descents, too, although I'm afraid the weight of 141 years on the two saddles makes it a bit slow on the climbs The back brake is a bit noisy (squeal) when the disc is damp but it still works OK

Thanks for that considered reply, Geoff. I'm not at all surprised to hear you can stop faster than a solo: I'll guess that that's more to do with the weight of the stoker, than the contact patch of the tyre, however. Solo bikes are enormously top heavy, with a short wheelbase. Riders go over bars with little provocation.

I'm still interested to know what defines the limit (but I don't want to encourage you to go out and test it..!). With your cantilevers, they were the limit. But with your hydraulic rim brakes, could you potentially slide the front tyre? (on smooth dry tarmac). Or would the forks or frame collapse first? As I wrote, that's my best guess, of course depending on the parts.

It's an academic query, I suppose (hope), but it's interesting because these things are often not as they seem.