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Old 07-29-11, 04:26 AM   #1
dsb137
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Brake Performance...

The 200K that runs thru my back yard goes up and down Brasstown Bald, so I figured I'd go recce the climb since I haven't been up it in over a year. Even though this is a 'local' climb for me I haven't done it but a few times, it's silly steep, and as much as it pains me going up, my biggest problem is coming down.

'The Complete Guide To Climbing In The Southeast' puts this climb at 11.1% average grade with a length of 3.1 miles and a maximum grade of 21%...

I'm a fair descender, I like descending, I used to Road Race motorcycles so I'm fairly comfortable picking up speed and keeping the speed thru the corner...

Having said that, on this descent I feel like I'm having to gorilla grip the break levers in order to scrub speed which makes the whole affair rather uncomfortable...

I'm using Chorus 10spd calipers and levers, the plain calipers not the skeletons. The rims are '90's vintage Campy Los Angeles tubulars shod with vit pave's in 24mm width. I'm currently running Swiss Stop green pads after trying the stock Campy's and the SS black.

The rims are the old box section type, they were NOS when I built the wheels a couple of years ago. They are anodized, but I don't know that they are 'hard' anodized. They don't have a machined brake track and the anodizing is almost completely scored off where the brake pads run. I frequently clean the rims with either alcohol or auto brake clean, and have used scotch brite pads but that doesn't seem to have any effect. I pull the brake pads and sand them whenever they appear to have contamination imbedded.

So, what if anything can I do to improve my brake performance? I have some Kool Stop Salmon pads on order, so I'll try those. Are the machined brake track rims significantly better? Do I have a miss match between the pad material and the rims I'm using? Would using the newer skeleton calipers gain me anything? What am I missing?

Thanks,
Dave
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Old 07-29-11, 08:36 AM   #2
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I think the Kool Stop pads will be worse. They don't pick up aluminum shards, but their grip on rims isn't that great.
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Old 07-29-11, 08:38 AM   #3
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Originally Posted by dsb137 View Post
...on this descent I feel like I'm having to gorilla grip the break levers in order to scrub speed which makes the whole affair rather uncomfortable...

I'm using Chorus 10spd calipers and levers, the plain calipers not the skeletons...So, what if anything can I do to improve my brake performance?... Would using the newer skeleton calipers gain me anything?...
Rim brake pads get hot then performance fades, trying a different pad compound is a good experiment.

The solid arm, dual pivot, front Chorus 10spd caliper has less flex than the skeleton caliper, the bending skeleton arm can be seen with the eye. The skeleton is good, but the older version is better.

A brake pad deposits pad material to the rim's friction surface, which aids grip, aggressive degreasers should be reserved for lube contamination, or following resurfacing.

Try brushing the swept area of the rim with 600 grit wet/dry paper, then clean with denatured alcohol. This will improve short duration braking, but it won't improve heat tolerance.

Last edited by Werkin; 07-29-11 at 08:41 AM.
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Old 07-29-11, 09:11 AM   #4
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Your brakes will work better as the anodizing is scrubbed off so I'd say that is not a issue. A change to a machined surface doesn't matter except that it isn't anodized and your rims have already been scrubbed of anodizing.

If you are bombing a 11 to 21% grade you could be going 60mph at times. Slowing from that speed will require a steady hand on the brake lever. In my performance driving instructor days I used to tell students "going fast is never comfortable." Same thing on a bike...

What Werkin said about pad material transfer to rims is correct. You want to let that pad deposit material on the rim as it does aid braking. Stop scrubbing your rims and pads and I bet your braking will improve. Rims and pads are wear items anyway.

Good luck
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Old 07-29-11, 10:26 AM   #5
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I used to road race motorcycles as well and bicycles are much more squirrely descending in the corners than motorcycles are. It's probably a combination of geometry/wheel size and tire contact patch and they do not stop as well (as you've noticed). On my rando bike I usually use my Mavic OP Ceramic rims. They provide a grippier braking surface than standard rims. They work especially well in the rain.

The other option is to just not use your brakes. It makes the descents that much more fun!

Btw. three miles with an average grade of 11% should be good enough to get you up into the 70mph range...assuming no corners.
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Old 07-29-11, 11:38 AM   #6
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Thanks guys... I'll leave the rims alone for a bit and see how that goes... Would you say the same for sanding the pads? Like I said, I tend to sand them clean whenever I see stuff imbedded... Do bike brake pads glaze?

Homeyba... yeah the 'no brakes drill' (did Code really invent that ?) works a treat... Actually on most of the descents around here I tend to use very little if any brake... It's not hard to get into the 60's going down Hogpen Gap...
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Old 07-29-11, 12:32 PM   #7
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I don't think Kieth invented the "no brakes drill.' Back in my younger years (late 70's-early 80's) we used to have coasting races on our motorcycles down Palomar Mtn in SoCal. I'm sure it was done long before we were doing it. What Keith did put in his first book that I really like was the $1's worth of attention you have. If you are worried about getting stopped you are probably spending too much of your $1 on your brakes. That's going to take away from other areas that need your attention on a descent like that. If you want to descend comfortably and fast you need to have confidence in your stoppers.
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