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-   -   Disk Brakes (http://www.bikeforums.net/general-cycling-discussion/585904-disk-brakes.html)

Riverside_Guy 09-17-09 02:22 PM

Disk Brakes
 
I was right in the middle of the transition of drum to disk brakes on motorcycles so, of course, I'm wondering when Trek fx bikes may get disk brakes!

Anyone have any reason why they should NOT be deployed on this series?

RonH 09-17-09 02:28 PM

Why do you want disc brakes?

PaulRivers 09-17-09 03:06 PM

Disc brakes cost more, weigh more, and are more finicky and noisy (read a review of any disc brake system - avid 7's, shimano xtr, it doesn't matter - there's always a noticeably bunch of people complaining that their disc brakes rub and/or squeal when they stop). And with a skinny tire bike, disc brakes provide little extra stopping power because the contact area of the tire on the road is mostly already covered by the stopping power of rim brakes.

The advantages of disc brakes including superior braking performance in the wet, better braking performance in the cold (I've heard of rim brake pads icing over, never of disc brake pads doing the same), and if you ride your bike a *lot* of miles or ride in the winter, the wheel may last longer because there's no friction against the rim.

However, if you don't ride in the rain or when it's at or below freezing like most people don't, disc brakes don't offer a large advantage over rim brakes, but they do offer several disadvantages.

Riverside_Guy 09-17-09 03:11 PM

Mostly water... my most scary moment on a bike was getting caught in a rain shower with a downhill getting back home that I came close to losing it, even though I knew enough to pump the brakes. For a good city block, I had almost zero grip, a right turn at the bottom was needed even though I did bleed off SOME momentum. No issue with the pads, once dried, they were fine (not to mention there could be some grease mixed in that could have gotten on my rims).

I'm not sure if the kinds I see on bicycles have the same stronger and far more progressive feel as the ones on my motorcycles did compared to friction systems... I suppose it's possible. We are talking about substantially more friction surface in a drum... I know mass and momentum play a role.

Paul, I was writing when you posted... my rims do seem to have their share of squeals, the pads look OK, but just in terms of wear. Forget riding when freezing, but even trying to avoid rain, one CAN get caught. I'd like to NOT think about that when going out...

PaulRivers 09-17-09 03:22 PM

Quote:

Originally Posted by Riverside_Guy (Post 9694097)
Mostly water... my most scary moment on a bike was getting caught in a rain shower with a downhill getting back home that I came close to losing it, even though I knew enough to pump the brakes. For a good city block, I had almost zero grip, a right turn at the bottom was needed even though I did bleed off SOME momentum. No issue with the pads, once dried, they were fine (not to mention there could be some grease mixed in that could have gotten on my rims).

I'm not sure if the kinds I see on bicycles have the same stronger and far more progressive feel as the ones on my motorcycles did compared to friction systems... I suppose it's possible. We are talking about substantially more friction surface in a drum... I know mass and momentum play a role.

Paul, I was writing when you posted... my rims do seem to have their share of squeals, the pads look OK, but just in terms of wear. Forget riding when freezing, but even trying to avoid rain, one CAN get caught. I'd like to NOT think about that when going out...

Well fyi, you might try replacing your rim brake pads with one of two options -
1. The Koolstop Salmon pads, I've been told several times on bikeforums.net here, are supposedly very nearly as good in the rain as discs. Supposedly. I haven't tried them, but it certainly sounds like they are a lot better than the description of the pads on your bike right now!
2. The Dura-Ace 7900 brake pads claim to increase wet weather performance by 50% over the old ones (which weren't great).

I've heard this makes a huge difference for a relatively small amount of money. If you had almost zero grip in the rain, I definitely think better pads would at least be an improvement.

dynaryder 09-18-09 09:07 AM

Trek used to have FX disc models. They were replaced by the Soho series,and these in turn replaced by the single Valencia model. Discs are slowly starting to creep back into some manufacturers' lines,like Giant's Seek series.

Without lighting off another flame war,I'll just say that I highly recommend discs for folks who ride in all weather for a long list of reasons. Also,the only noise issues I've ever encountered were from me being too lazy to clean the bike after riding in bad weather.

Velo Dog 09-18-09 09:12 AM

Quote:

Originally Posted by PaulRivers (Post 9694058)
Disc brakes cost more, weigh more, and are more finicky and noisy ... disc brakes don't offer a large advantage over rim brakes, but they do offer several disadvantages.

This has been my experience, too. Except in a few specific circumstances, they're not worth the trouble and expense.
If it makes you feel better, technically ALL bike brakes are disc brakes: You've got a set of pads grabbing the rim, which is a narrow, flat disc.

seawind161 09-18-09 09:45 AM

Quote:

Originally Posted by PaulRivers (Post 9694058)
Disc brakes cost more, weigh more, and are more finicky and noisy (read a review of any disc brake system - avid 7's, shimano xtr, it doesn't matter - there's always a noticeably bunch of people complaining that their disc brakes rub and/or squeal when they stop).

I have Juicy 3's and 5's on mountain bikes, and I have to agree, they're finicky, and there's often a little pad rubbing.

But I have BB-7's on two other bikes, and have had ZERO problems in a little over 4k miles. The BB-7's have independently adjustable pads, and if the caliper is properly installed, there's just no problem.

stapfam 09-18-09 11:16 AM

3 Attachment(s)
I ride MTB's and road. The only reason I can see for using disc brakes is the excessive rim wear I get on the MTB's.

I only have one bike set up with disc brakes and that is the Offroad Tandem- but I went top dollar with them and the wheels aswell. For the MTB's I use "V" brakes and cannot fault them for stopping power in any condition. But it is XT Brakes and LX levers to get the best for me.

On the road bikes- I do have respertable wheels- None of them are OM so can't comment on the stock wheels. One set of wheels must have 10,000 miles on them and no sign of wear on the rims- but the bearings are getting a bit graunchy so time to grease and adjust them

But on the MTB's- I find that 2,000 miles is about the limit I can get out of the rims. They wear down and as soon as I start seeing a curve come into the braking area- I start looking for new wheels. I say new wheels as by that time the hubs are getting a bit of wear on the cups and the spindles and there is not much difference in cost to a new XT hub and Mavic rim to rerimming from my builder.

And braking effect on the "V"'s- Perfect. Braking effect on the Tandem with Disc's- Better than perfect.

coldfeet 09-18-09 12:44 PM

I am looking forward to my first Winter with disc brakes, it will be so nice not having to adjust the brakes so often, not having to strip them down every 4-6 weeks, not having that horrible "scrunch" as you apply them. That, and having a good idea they will actually stop me. Calgary Winters are a perfect example of the advantages, you end up riding in this half melted grit and sand laden slop. It's foul.

wunderkind 09-18-09 05:52 PM

Quote:

Originally Posted by seawind161 (Post 9698448)
I have Juicy 3's and 5's on mountain bikes, and I have to agree, they're finicky, and there's often a little pad rubbing.

But I have BB-7's on two other bikes, and have had ZERO problems in a little over 4k miles. The BB-7's have independently adjustable pads, and if the caliper is properly installed, there's just no problem.

On the contrary, my front disc Hayes unit has been dead reliable and maintenance free. I never had to adjust it once ever. Unlike my rear linear pulls which every so often requires some adjustments. It does sometimes emit some kinda spinning blade sound like someone is sharpening knives. :)


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