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Discussion Starter · #1 ·
Last week has been rainy around here and I got caught out a few times in real downpours. I expect the first bit of wet braking to be slow (squeezing that water layer off the rims), but recently my rear brake has been REALLY bad in the wet while front worked as expected for the conditions. After the rains passed & things dried out, rear brake worked fine again. Pads are DA, not worn out, and seem clean. Never had this happen before, and don't want it happening again. Only thing that I changed recently is that I switched chain lubes. Could the new lube have been splashing off onto the rear rim causing that poor rear braking issue? Other causes to check on?
 

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Could be the lube, what kind of lube are you using now?

Could be glazed pads. Remove the pads and sand off the top layer that looks all glossy. Use 120 grit or so sandpaper. This should be done often on hard compounds like with DA or with carbon specific brake pads.

Could be incorrect toe as well, without correct toe in you can pull as hard as you want and you'll get no additional grip over what you have to start with.

Also clean your rim itself, the braking surface, really well. Get all of the black residue off of it. Some say to use a light sandpaper if needed but you should never need to do that if you stay on top of it. Rubbing alcohol and elbow grease should do it.
 

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How you'd determine it was so bad? Are you just squeezing the rear brake to slow down at times?

Reason being the front is doing the majority of your stopping for you, so with the rain necessitating more braking time and you paying attention to it that much more, I'm wondering if it's performing fairly normally.
 

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Rim brakes + rain = sketchy braking
Mine work pretty well actually? You need a little extra thought/time to "wipe" the rim or such, but they grip better than I would have ever expected. Been out in some rough conditions, including sleet and freezing rain, downpours... Tire performance, road paint, steel bits... That's a *****. Brakes, even my rim type, have been good.
 

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Disc brakes don't have that issue :) Good excuse for another bike - N+1!
 

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Shimano are mediocre pads, worse than mediocre in rain.

get some nice Kool Stops. I live in rain forest, the KS really help, and slide right into the Shimano pad holders. Other companies make similar - usually 'salmon colored' pads, with iron oxide in them which def transform the braking power in rain.

https://www.amazon.com/Kool-Stop-Bi...8_1?ie=UTF8&psc=1&refRID=TXMGF9Y30GM3BY1GNJ2Z

Sheldon Brown's opinion:
Kool Stop Salmon Brake Pads for Bicycles from Harris Cyclery

I just put on a new Ultegra groupset. Rode for a while with the stock pads. sucky ****. slipped in some new Kool Stops. much much better.
 

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During braking, weight transfers to the front wheel. I can't explain the physics, but that's why the front brake is more effective than the rear brake.

In the rain, braking will cause the rim to heat up, causing the water on the rim to evaporate more rapidly. After the water evaporates, braking improves. Since there's less weight over the rear wheel, during the rain rear braking is even less effective because of this weight transfer.

I have not found any brake pad more effective in the rain than others. Probably only disc brakes could solve this problem.
 

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Discussion Starter · #11 ·
Not my only roadie, and this bike setup performance is very different from my other rides in wet braking. As in almost NO slowing down when first applying rear brake only HARD. After what seems like 5 or so revolutions of the wheel I start to get some braking power. Like I said, strange thing is that when things dry out, that same brake works fine. Calipers are 105. Pads are DA, clean, well- positioned/adjusted, and only about a third worn. BTW- I also like salmon Kool-stops better than DA's for wet braking & have them on one of my other bikes.
I'm now more convinced that it is the new chain lube. It is a wet lube that seems to attract much more junk than ProLink or White Lightning I use on my other bikes. I'm going to clean the chain & relube with ProLink....then wait for the next rain to conduct the experiment ;)
 

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Discussion Starter · #13 ·
Stop applying the rear brake only first.

You're braking incorrectly.
Agree "applying rear brake only first" is not good braking technique. I was TESTING the rear brake after I noticed something amiss. As I said, this is not my only bike. And not my first season (or decade) riding. Just the first time I had noticed a marked change in wet braking after switching chain lubes.
I have not yet had time to clean the chain and switch back to ProLink lube to see if that is indeed the issue, but will try to post an update.
 

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More like:

Riders with no skill + no experience = sketchy.

But it's easier to blame the equipment.
Assuming he's been riding at least as long as he's been a forum member, he's got 11 years of experience. Biking isn't that hard. He's probably picked up some skill in that time. I tip my hat at his ability to ignore your trolling post.
 

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Assuming he's been riding at least as long as he's been a forum member, he's got 11 years of experience. Biking isn't that hard. He's probably picked up some skill in that time. I tip my hat at his ability to ignore your trolling post.
This wasn't in response to the OP. It was in response to Aadub's post.

I won't tip my hat at your inability to read, though I hope this response will fulfill your apparent need for my attention.
 

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Agree "applying rear brake only first" is not good braking technique. I was TESTING the rear brake after I noticed something amiss. As I said, this is not my only bike. And not my first season (or decade) riding. Just the first time I had noticed a marked change in wet braking after switching chain lubes.
But this isn't a test that's going to really tell you anything as your rear brake isn't going to be slowing you substantially anyway.
 

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Discussion Starter · #17 ·
But this isn't a test that's going to really tell you anything as your rear brake isn't going to be slowing you substantially anyway.
No doubt the front brake supplies most of the stopping power, but applying the rear brake ONLY (open stretch of road of course) would seem to be the best way to isolate rear vs front braking function. In my experience, a well-functioning rear rim brake should supply some useful added stopping power over the front brake alone.
 

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You say it works fine in the dry, but not in the wet.

To me this is a nonissue. You want to stop in the wet, plan ahead, brake earlier, use both brakes.

Testing whether or not you can stop in the wet just by using your rear brake seems to me to be the manifestation of silly-stupid.
 
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