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General Category >> Technical >> Disc brakes vs rim brakes
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Message started by Tiger_Mike on Apr 14^th, 2015, 8:18pm

Title: Disc brakes vs rim brakes
Post by Tiger_Mike on Apr 14^th, 2015, 8:18pm

I'm thinking about a P38 build, and I'm mulling over brake choices. Is there any compelling reason to choose disc brakes over rim brakes?

Title: Re: Disc brakes vs rim brakes
Post by LightningPilot on Apr 14^th, 2015, 8:53pm

Tiger_Mike wrote:

I'm thinking about a P38 build, and I'm mulling over brake choices. Is there any compelling reason to choose disc brakes over rim brakes?

The rim brakes are hard to adjust and can still screech like banchees. If I was doing a new build, I'd go for disc, says the girl with two p38s.

Title: Re: Disc brakes vs rim brakes
Post by MrWizard on Apr 14^th, 2015, 9:55pm

LightningPilot wrote:

[quote author=Tiger_Mike link=1429060706/0#0 date=1429060706]I'm thinking about a P38 build, and I'm mulling over brake choices. Is there any compelling reason to choose disc brakes over rim brakes?

The rim brakes are hard to adjust and can still screech like banchees. If I was doing a new build, I'd go for disc, says the girl with two p38s.[/quote]

The guy with two P38s and one R84 agrees completely .. the rim brakes Tim uses by default are old-MTB V brakes. They are a PIA. Go with Disc. I converted my voyager to disc and I am so happy about it, I kick myself for not doing it years back. The only P38 that hasn't been converted is the one set up for indoor riding which has the brakes removed and replaced with "reverse track" "forward track" levers for controlling the audio. (yes I'm a nerd, stop laughing)

Title: Re: Disc brakes vs rim brakes
Post by Monkeywrangler22 on Apr 15^th, 2015, 6:23am

If you go disc, invest in the TRP HY-RD ones. Better than BB7's by far. I will eventually, when budget permits, upgrade my Encore to the TRP discs.

Title: Re: Disc brakes vs rim brakes
Post by FlyingLaZBoy on Apr 15^th, 2015, 11:32am

Discs work SO much better in wet conditions...

Title: Re: Disc brakes vs rim brakes
Post by Bud_Bent on Apr 15^th, 2015, 9:30pm

FlyingLaZBoy wrote:

Discs work SO much better in wet conditions...

That's not been my experience at all. Yes, disc brakes can lock up the wheel much better when things are wet, but it becomes the tire that slides on the pavement rather than the brake pads that slide on the rim. I found that I actually had better stopping control in wet conditions with the rim brakes than the disc brakes, and ended up wishing I had never converted to disc brakes on my commuting setup. When I sold the Stratus XP and started commuting with the Xstream instead, I went back to rim brakes.

Vee brakes that have an arch, like the Avid Arch Rival brakes, can really lock up wheels, even on a tandem. I have them on my Screamer, and Greg can testify to how they can lock up the wheels, as he witnessed Rose and I skidding with the rear wheel locked up. I had to learn to modulate them like I did disc brakes, to keep from locking up a wheel too easy. But, on wet pavement, they don't lock up nearly as easy as disc brakes do, so I like them better than the disc brakes I had on the EZ Tandem. YMMV.

Title: Re: Disc brakes vs rim brakes
Post by MrWizard on Apr 16^th, 2015, 10:48am

Bud_Bent wrote:

[quote author=FlyingLaZBoy link=1429060706/0#4 date=1429115528]Discs work SO much better in wet conditions...

That's not been my experience at all. Yes, disc brakes can lock up the wheel much better when things are wet, but it becomes the tire that slides on the pavement rather than the brake pads that slide on the rim.
[/quote]

Isn't this a function of how hard you pull the lever back ? If you don't want it to lock up, modulate. (oh $h*t moments not withstanding) This is why I always liked hydraulic vs cables .. you can 'feel' how much breaking was applied. At least I could, or perhaps i was just convinced that I could because I overpaid for the fluidics when a cable would have worked. ;)

Of course, we can talk about drum brakes now .. for true rubber wrenching off the rim lockup power. http://www.sturmey-archer.com/en/products/detail/xl-sd .

Title: Re: Disc brakes vs rim brakes
Post by rcko on Apr 17^th, 2015, 6:41pm

Riding both, trp cable actuated hydro reservoir on caliper discs on my GT Grade and rim brakes on Synapse

Hydro offers superior modulation and for a given lever pressure more braking power than the rim brakes.

However, tire contact patch is an issue, and that applies to both styles of brake. I can lock up either with enough lever pressure. So from a power perspective both are powerful. Actually the rim brake has more leverage...

If u got disc brake mnts and can afford the hydros I highly recomend the TRP hydro units. Remeber to bed the pads on ur first few rides to obtain full authority.

Ur other tuning option is disc rotor diameter. I am running 160mm.

Disc take a bit more care to align properly when doing wheel skewers. Just takes a bit more careful alignment than rim brakes.

Title: Re: Disc brakes vs rim brakes
Post by Bud_Bent on Apr 17^th, 2015, 11:19pm

Yes, what it takes to lock up wheels is very different on wet pavement as opposed to dry pavement, and you have to learn how hard you can brake without locking them up on wet pavement, not so easily done, even with brakes that modulate well. With many rim brakes, you can't lock them up at all when the pads are wet, though.

Title: Re: Disc brakes vs rim brakes
Post by aikigreg on Apr 18^th, 2015, 12:53am

That was a scary moment, Bud.

I'm tempted to go to disc on the m5 to eliminate my leg hitting the brake. I've got a bad abrasion from Bessie's Creek on the back of my thigh from it. Tried a simkins egg brake which was narrow and perfect, except it was finicky and started rubbing the tire.

I need a narrow brake with decent stopping power, but I don't want to change every bike I own to disc. Also, since the uci approved the use of discs in three pro peloton, we're going to see some radical changes over the next year. Best to wait I think.

Title: Re: Disc brakes vs rim brakes
Post by jayg on Apr 18^th, 2015, 10:48am

Bud_Bent wrote:

With many rim brakes, you can't lock them up at all when the pads are wet, though.

My Musashi came equipped from the factory with Tektro caliper brakes and pads and Avid disc brake handles. Got caught in a downpour on a hilly pay ride. Brakes were almost totally ineffective, after the pads got wet (175 lb. bike/rider combo).

Title: Re: Disc brakes vs rim brakes
Post by Bud_Bent on Apr 18^th, 2015, 4:39pm

jayg wrote:

Title: Re: Disc brakes vs rim brakes
Post by jayg on Apr 18^th, 2015, 11:15pm

Bud_Bent wrote:

[quote author=jayg link=1429060706/0#10 date=1429372092]My Musashi came equipped from the factory with Tektro caliper brakes and pads and Avid disc brake handles. Got caught in a downpour on a hilly pay ride. Brakes were almost totally ineffective, after the pads got wet (175 lb. bike/rider combo).

Yes, many rim brakes are like that. But, if you replace the original pads with better ones for wet riding (I like the Kool Stop in Salmon), they will stop the bike. Many still won't lock up the wheel when they're wet, but locking up the wheel doesn't help anyway.
[/quote]

The first thing I did after the no-brakes incident was to install Salmon pads. Never got to test them in a downpour. To be honest, the bike's stopping power was less than satisfactory, before the no-brakes incident. I eventually replaced the long-pull Avid brake handles that came with the bike with short-pull Shimano caliper brake handles. The Shimano levers can apply up to a 60% greater force to the brake cables than the Avid levers. The brakes are now satisfactory. I've ridden the bike in the rain several times, since I replaced the levers, but not in a downpour. Haven't noticed any great loss of effectiveness (Still using Salmon pads).

Title: Re: Disc brakes vs rim brakes
Post by FlyingLaZBoy on Apr 20^th, 2015, 1:15pm

Good point about wheel lockup / skidding, Bud.... I locked up the wheels on my SXP in the rain, once (even with rim brakes), and the tires started skidding and took me down...

Title: Re: Disc brakes vs rim brakes
Post by Bud_Bent on Apr 20^th, 2015, 5:25pm

jayg wrote:

The first thing I did after the no-brakes incident was to install Salmon pads. Never got to test them in a downpour. To be honest, the bike's stopping power was less than satisfactory, before the no-brakes incident. I eventually replaced the long-pull Avid brake handles that came with the bike with short-pull Shimano caliper brake handles. The Shimano levers can apply up to a 60% greater force to the brake cables than the Avid levers. The brakes are now satisfactory. I've ridden the bike in the rain several times, since I replaced the levers, but not in a downpour. Haven't noticed any great loss of effectiveness (Still using Salmon pads).

There are also brake levers which can adjust to be either long or short pull. Those are nice to help get the pressure just where you want it.

FlyingLaZBoy wrote:

Good point about wheel lockup / skidding, Bud.... I locked up the wheels on my SXP in the rain, once (even with rim brakes), and the tires started skidding and took me down...

Yes, to me, it's the hardest part of riding in the rain: figuring out how to do the best job of stopping, without laying the bike down. Every set of brakes is different, and how slick the roads are changes, and has a lot to do with how easy the wheels lock up. I've never liked riding on wet roads, and I still don't.

Title: Re: Disc brakes vs rim brakes
Post by Tiger_Mike on Apr 20^th, 2015, 8:23pm

Lots of interesting points made. What I've gleaned from this is there isn't a super compelling performance reason to choose one over the other. Wet performance isn't all that important to me....I don't plan on riding in downpours, and when I did get caught in one I found that rain striking my face at anything above 10 mph was really unpleasant, and the wet braking performance with my rim brakes was adequate.

The reason I posed the question originally is that I'm undecided if the P38 is going to replace my commuter bike or my "go fast" bike. Micah at Easy Street suggested it could do both roles if I was willing to swap out wheels. Disc brakes would definitely simplify changing between the wide rim, heavy duty fat tire commuter wheel set and the skinny speed set. That convenience comes at a pretty high cost though...going to discs means I can't use any of my existing wheels, and the disc brakes are more expensive, especially if I go with the high end ones Vicki likes. It becomes a bit of a triple whammy if I start out with a frame set and build exactly what I want. Next to buying a used one, an "off the rack" bike is certainly the next affordable.

I dunno what I'm going to do yet, but it sure is nice to have first world problems like this!

Title: Re: Disc brakes vs rim brakes
Post by jayg on Apr 20^th, 2015, 8:44pm

Bud_Bent wrote:

There are also brake levers which can adjust to be either long or short pull. Those are nice to help get the pressure just where you want it.

Yes, they are nice. The Shimano R550 is an example of a two-setting lever. A pair of them came on my new Performer low racer. Set them for short pull so the bike's caliper brakes would be as effective as possible.

Title: Re: Disc brakes vs rim brakes
Post by rmillay on Apr 21^st, 2015, 10:08pm

Aluminum rims made rim braking far more reliable, but flooding reduces that reliability. The solution is to learn how to use your brakes in compromising situations. It may take practice, in the rain or going through puddles. Riding the brakes in the rain may sound counter productive, but before a steep descent it could provide some control you wouldn't have otherwise.

Title: Re: Disc brakes vs rim brakes
Post by MrWizard on Apr 23^rd, 2015, 9:43am

I'm just going to leave this here

https://www.youtube.com/watch?v=Xe-U2E6Cw8w (amusingly translated video)
http://www.bikerumor.com/2012/11/27/hands-on-sabs-antilock-bicycle-brake-pads/

Title: Re: Disc brakes vs rim brakes
Post by AustinSkater on Apr 23^rd, 2015, 10:21am

You don't see things like this happening with rim brakes:

http://www.nydailynews.com/news/national/trek-recalls-1-million-bikes-rider-paralyzed-article-1.2194234

For those with disc brakes, check your skewers.

Title: Re: Disc brakes vs rim brakes
Post by rcko on Apr 24^th, 2015, 1:11pm

Even without disc... U should ck skewers before every ride...

Title: Re: Disc brakes vs rim brakes
Post by jrob_bent on Apr 24^th, 2015, 9:36pm

Kool Stop duals is what I use on my bikes. They work great in the rain, mud, or dry. I use the mtb ones for my 26" and 20" wheels. They are Salmon on the front and black on the other end. The Salmon for wet and the black for dry. The Salmon end has a tapered sort of tip for removing mud and rain. $11 and free shipping with no tax from Amazon per pair. They stop both my Rans V2 and Phantom very well in all conditions. Good luck on your choice.