Disc Vs Rim Braking System

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Duck!
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Re: Disc Vs Rim Braking System

Postby Duck! » Sun Jun 18, 2017 10:32 am

The vast majority of brake noise is caused by pad glazing, not contamination. Although technique and adjutment are major contributors, insufficiently bedded-in rotors will exacerbate glazing, with resulting noise and poor performance.

Continual, excessive cleaning of the rotors basically ensures they're never properly bedded in, so they never operate quietly.

By all means clean them if you are absolutely sure they are contaminated, but otherwise just give the pads a scuff on sandpaper.
I had a thought, but it got run over as it crossed my mind.

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Re: Disc Vs Rim Braking System

Postby trailgumby » Sun Jun 18, 2017 10:39 am

Shelby35 wrote:Which are better resin or metal pads?
Depends on what rotors you have. If you have entry level Shimano brakes the rotors are not rated for metallic pad use and you'll likely chew them up with metallic pads.

However, if you are using Shimano SLX or better (road equivalent is 105?), the metallic pads last longer and ultimately give better braking.

I haven't used resin pads for quite some time. Occasionally I ride on wet and muddy trails in Sydney and resin pads disappear within 20km, leaving me trying to brake with the pad backing material. :x

if you occasionally ride in wet conditions on the road and your system can use metallic pads, I'd recommend you do. As a bonus, the high-finned Ice-Tech pads seem less prone to accumulating pad dust and road grime stuck on the piston sides, making them more reliable.

When I replace pads in the man-cave I usually pull out the brake cleaner spray and some cotton butds and give the caliper and piston sides a clean. Having stuck pistons that won't retract is a drag (pun intended).

Does that help?

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Re: Disc Vs Rim Braking System

Postby trailgumby » Sun Jun 18, 2017 10:59 am

Duck! wrote:Continual, excessive cleaning of the rotors basically ensures they're never properly bedded in, so they never operate quietly.
I've never, ever (ever) had that problem.

Cleaning is basically spraying the rotor with Super Cheap Auto or equivalent hydrocarbon disc rotor cleaning spray and wiping off with a soft *clean* rag.

Bedding in is wearing in the surface of the rotor to match the surface of the pad (and vice-versa). The transfer of pad material embedded into the rotor surface is minimal, and in any case minimally removed (if at all) by the above process. When I swap wheels I swap pads as well, keeping front and rear separate in very clearly labelled boxes. I do not then need to bed the pads in again each time I swap wheels. Learned that trick the hard way.

Scuffing the pad surface with an abrasive material usually requires repeating the bedding-in process to a greater or lesser degree in my experience, as the pads are no longer matched to the rotor. This is OK, preferable to glazed pads, but an unavoidable consequence.

In my experience, contamination is a more frequent cause of noise than glazed pads.

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Re: Disc Vs Rim Braking System

Postby Duck! » Sun Jun 18, 2017 11:24 am

trailgumby wrote:
Shelby35 wrote:Which are better resin or metal pads?
Depends on what rotors you have. If you have entry level Shimano brakes the rotors are not rated for metallic pad use and you'll likely chew them up with metallic pads.

However, if you are using Shimano SLX or better (road equivalent is 105?), the metallic pads last longer and ultimately give better braking.
Deore is the entry point for metal pad options.

Depends on what factors are used to determine "better". Resin pads are a softer compound, which gives better initial bite, at the expense of some modulation, and can be quieter, unless glazed or wet. The extra bite is good in cold weather or when the brakes are relatively infrequently used, where the brake remains cool. On the downside, the soft compound is prone to rapid wear in bad weather, and also less tolerant of heat, resulting in glazed pads, which are then noisy and ineffective - often mistaken for contamination.

Metal pads, being harder, offer less initial bite, but more overall stopping power, with better modulation. They're more resistant to wear in foul conditions and more heat tolerant; in fact they actually need some heat to work properly, and can feel very vague and ineffective when very cold.
I had a thought, but it got run over as it crossed my mind.

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Re: Disc Vs Rim Braking System

Postby trailgumby » Sun Jun 18, 2017 12:13 pm

Duck! wrote:Deore is the entry point for metal pad options.
Thanks for the clarification.
Duck! wrote:On the downside, the soft compound is prone to rapid wear in bad weather, and also less tolerant of heat, resulting in glazed pads, which are then noisy and ineffective - often mistaken for contamination.
OK, that goes some way to explaining our differing points of view. Cheers.

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Re: Disc Vs Rim Braking System

Postby Patt0 » Sun Jun 18, 2017 1:52 pm

I no longer clean the disc, because I no longer blow globs of greasy wax on there with compressed air. I do an initial chain clean, blow down the bike with air and brush, finish cleaning the chain and then wipe down bike with mineral turps.

I have found resin more than adequate on road with 160mm discs.

Anyone try the resin pads that are 4 pairs for $8 on alibaba? I only go through 2 sets of pads (2x13.50) a year so not sure I need to experiment :)
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Re: Disc Vs Rim Braking System

Postby MichaelB » Sun Jun 18, 2017 2:55 pm

Good pads are not that expensive.

Stick to the good ones. I do. I think my life is worth a bit more, and brakes are not really the place to be saving money...

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Re: Disc Vs Rim Braking System

Postby Bunged Knee » Sun Jun 18, 2017 4:16 pm

Patt0 wrote: Anyone try the resin pads that are 4 pairs for $8 on alibaba? I only go through 2 sets of pads (2x13.50) a year so not sure I need to experiment :)
I bought it from alibaba for that price months ago. But it's only good for a few kms and after that, then it squeals. Not good for cheap price. I put the proper Shimano brand and it gets back to normal braking.

Stay away from cheap alibaba disc brake pads. Not worth it, unless you want it as warning bell replacement.
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Re: Disc Vs Rim Braking System

Postby TheWall » Sun Jun 18, 2017 4:16 pm

MichaelB wrote:
Stick to the good ones. I do. I think my life is worth a bit more, and brakes are not really the place to be saving money...
Sounds like a pretty good argument for discs...

Rode my older bike (ultra rim brakes) down some steep descents today....

Really hoping my disc brake bike is back for next weekends adventure!

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Re: Disc Vs Rim Braking System

Postby trailgumby » Sun Jun 18, 2017 5:26 pm

I don't bother with non-Shimano disc pads. The savings aren't worth it.

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Re: Disc Vs Rim Braking System

Postby Shelby35 » Sun Jun 18, 2017 9:07 pm

Thanks Guys
Currently using shimano rt99 disc and have the original resin pads that came with the bike and was looking at changing them soon might give the metal one as try.
trailgumby wrote:
Shelby35 wrote:Which are better resin or metal pads?
Depends on what rotors you have. If you have entry level Shimano brakes the rotors are not rated for metallic pad use and you'll likely chew them up with metallic pads.

However, if you are using Shimano SLX or better (road equivalent is 105?), the metallic pads last longer and ultimately give better braking.

I haven't used resin pads for quite some time. Occasionally I ride on wet and muddy trails in Sydney and resin pads disappear within 20km, leaving me trying to brake with the pad backing material. :x

if you occasionally ride in wet conditions on the road and your system can use metallic pads, I'd recommend you do. As a bonus, the high-finned Ice-Tech pads seem less prone to accumulating pad dust and road grime stuck on the piston sides, making them more reliable.

When I replace pads in the man-cave I usually pull out the brake cleaner spray and some cotton butds and give the caliper and piston sides a clean. Having stuck pistons that won't retract is a drag (pun intended).

Does that help?

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Re: Disc Vs Rim Braking System

Postby MichaelB » Mon Jun 19, 2017 10:08 am

trailgumby wrote: .... When I swap wheels I swap pads as well, keeping front and rear separate in very clearly labelled boxes. I do not then need to bed the pads in again each time I swap wheels. Learned that trick the hard way.

...
In my experience, contamination is a more frequent cause of noise than glazed pads.
Never done the 1st point, and not suffered any issues. Even changed pads and not done anything else (no cleaning etc) and not noticed any difference compared to when I did do it in the past. Maybe slightly quicker bedding in ?

re the 2nd point, I'd agree there.


What I'd also add is that if pads 'glaze' with one setup, it may not be the pads, it can be the disc. Had this happen to me with Shimano finned resin pads & Avid HSX front rotor. Been down this particular descent many times with no issues on other discs (same pads) and in same conditions.
Changed the disc to an Ice Tech RT68 (same size) and chalk & cheese.

Unless you are a MTB'er, I've never had an issue with pads glazing (apart from above) and that includes descents down the Umbrail Pass, La Plagne, Cormet de Roseland, Col du Pre etc. Resin pads work really well, and Ice Tech discs are my one and only type now.
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Re: Disc Vs Rim Braking System

Postby hamishm » Mon Jun 19, 2017 10:38 am

Duck! wrote:Deore is the entry point for metal pad options.
What's that in RT-xx numbers? Thanks.

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Re: Disc Vs Rim Braking System

Postby Duck! » Mon Jun 19, 2017 12:34 pm

The entry-level rotors compatible with metal pads are SM-RT64 Centrelock & SM-RT66 6-bolt.
I had a thought, but it got run over as it crossed my mind.

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Re: Disc Vs Rim Braking System

Postby kb » Mon Jun 19, 2017 2:36 pm

trailgumby wrote:I don't bother with non-Shimano disc pads. The savings aren't worth it.
Currently trying out SwissStop EXOTherm 34. Feel slightly better than the previous Shimano but not a saving :-)
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Re: Disc Vs Rim Braking System

Postby trailgumby » Tue Jun 20, 2017 8:21 pm

kb wrote:
trailgumby wrote:I don't bother with non-Shimano disc pads. The savings aren't worth it.
Currently trying out SwissStop EXOTherm 34. Feel slightly better than the previous Shimano but not a saving :-)
I'm curious... Finned?

I have the SwissStop blue pads on my roadie and they're quite good. They weren't a saving either.

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Re: Disc Vs Rim Braking System

Postby outnabike » Tue Jun 20, 2017 10:00 pm

This thread got me going. I have done 5000 klm on the one set and thought I would get a new set prior to stripping the old ones. Might save me doing the work twice.
So off to the bike shop, Ivanhoe cycles in Hallam. It is a big store with an active repair section.

The front brake is a mech disc.....no pads in stock. Rear brakes are Deore XL calipers with rim pads. No pads in stock in Shimano. Shimano go for around $20-25-00 for rim pads but the after market ones in stock are $15-00 a set.

I rode 20 klm round trip and went away empty handed. I cant believe a shop this large has no stock of these basic components.They have heaps of Giants, Cannondales etc and they must just cut up bits of old Dunlop tyres or something. :)
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Re: Disc Vs Rim Braking System

Postby Duck! » Tue Jun 20, 2017 10:56 pm

That's more the problem of Shimano Australia's rotten stock control than anything else. Shops can't stock stuff they can't get.....
I had a thought, but it got run over as it crossed my mind.

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Re: Disc Vs Rim Braking System

Postby MichaelB » Wed Jun 21, 2017 8:42 am

trailgumby wrote:
kb wrote:
trailgumby wrote:I don't bother with non-Shimano disc pads. The savings aren't worth it.
Currently trying out SwissStop EXOTherm 34. Feel slightly better than the previous Shimano but not a saving :-)
I'm curious... Finned?

I have the SwissStop blue pads on my roadie and they're quite good. They weren't a saving either.
Yep, the EXOtherm are the finned version.

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Re: Disc Vs Rim Braking System

Postby Mububban » Wed Jun 21, 2017 9:49 am

I've only done about 1500km on my disc brake bike so far. You can see the brake pads on a rim brake bike to judge remaining lifespan. What's the obvious sign that new pads are required?

For those with carbon wheels and rim brakes - exactly how fast does one need to go downhill before heat becomes an issue? Would a chump like me be fine on them? Or should I look for wheels with an alloy brake track?

My next bike will be a lightweight bike so I can punish myself in the hills. Although I love my discs, the lightest options are currently rim brake bikes. And hills means descents (the Perth hills eg coming down Gt Eastern Hwy). I'm no daredevil so will likely descend cautiously rather than tuck down low for ultimate speed, and I wouldn't ride it in the wet.
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Re: Disc Vs Rim Braking System

Postby Duck! » Wed Jun 21, 2017 1:36 pm

Mububban wrote:I've only done about 1500km on my disc brake bike so far. You can see the brake pads on a rim brake bike to judge remaining lifespan. What's the obvious sign that new pads are required?
You'll tend get long lever travel, especially the first time after the bike has been parked, as the pads will retract into the caliper. They'll also get noisy as the spacer spring or worse, the backing plate 'cos you've worn the pad material off! - contacts the rotor. A quick glance into the caliper will indicate how worn they are. Recommended minimum thickness is generally around 1mm.
For those with carbon wheels and rim brakes - exactly how fast does one need to go downhill before heat becomes an issue? Would a chump like me be fine on them? Or should I look for wheels with an alloy brake track?
It's not about how fast you go, it's about how fast you don't go! The enemy of carbon rims is brake dragging. You're better off staying off them, and jumping hard on them when you need to slow down. The composite layup is an insulator to an extent, so heat takes a little while to build up, but on the flip side once the rim is heated it doesn't release the heat very well. So a short hard grab will result in a high surface temperature, but the heat won't penetrate into the core. Dragging the brake will keep driving heat into the core of the layup, and it will stay there, build up and melt the rim.
I had a thought, but it got run over as it crossed my mind.

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Re: Disc Vs Rim Braking System

Postby singlespeedscott » Wed Jun 21, 2017 7:52 pm

Duck! wrote: It's not about how fast you go, it's about how fast you don't go! The enemy of carbon rims is brake dragging. You're better off staying off them, and jumping hard on them when you need to slow down. The composite layup is an insulator to an extent, so heat takes a little while to build up, but on the flip side once the rim is heated it doesn't release the heat very well. So a short hard grab will result in a high surface temperature, but the heat won't penetrate into the core. Dragging the brake will keep driving heat into the core of the layup, and it will stay there, build up and melt the rim.
This should really apply to the use of any rim brake. Dragging the brakes is bad in any situation regardless of the rim construction.

There really shouldn't be any concern for keeping the speed in check on a straight descent. Falling off at 50 kmhr is going to be just as painful as falling off at 80 kmhr.
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Re: Disc Vs Rim Braking System

Postby kb » Thu Jun 22, 2017 9:45 am

trailgumby wrote:
kb wrote:
trailgumby wrote:I don't bother with non-Shimano disc pads. The savings aren't worth it.
Currently trying out SwissStop EXOTherm 34. Feel slightly better than the previous Shimano but not a saving :-)
I'm curious... Finned?

I have the SwissStop blue pads on my roadie and they're quite good. They weren't a saving either.
Yep, also finned. Similar differences to the SwissStop BXP vs Shimano - a touch less grabby but more modulated. Maybe stop just a touch better on full squeeze. I'd recommend them but just got a notice of a recall
stop-ride/stop-sale advisory for SwissStop EXOTherm type disc brake pads, due to potential separation of the friction compound from the backplate.
!

Still waiting on the L02A pads - been 5 weeks. Sigh.
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Re: Disc Vs Rim Braking System

Postby Trevtassie » Thu Jun 22, 2017 11:31 am

I did my first long tour with discs this and last month. Avid BB7s with standard pads. Yep, the front disc gets hot coming down steep windy mountain passes, where you have to brake. Hot enough to make the disc go blue, with a nice sizzle when touched with some spit on a finger. I did have them fade once, coming down a ridiculously steep rough road, no choice but to constantly brake or get off and walk. I reckon it would have been worse without the Rohloff, since that was the equivalent of slightly dragging the brakes. No real change in braking performance from V-brakes for touring purposes, except they made a horrible squeal when applied in the rain, it'd stop after the disc dried out.

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