Disc brakes on road bikes

[Binky]

When I travel normally I take my Scott CR SL rim brake bike, have done for 10+ years, mostly because it weighs 6.5kg but also because the ultegra brakes are amazing, paired with tubeless wheels. The wet makes zero difference to stopping performance.

My best bike a Cervelo R5 is rim brake with carbon wheels, just as good as hydro discs when it’s dry.

My Canyon Ultimate is disc and tbh it’s the worst of all my bikes but then I believe that down to a shoddy build by Canyon.

I’ve just bought/built a new yes new Canyon Endurace rim brake bike with Di2 Ultegra on carbon wheels.

You can still buy rim brake framesets and carbon rim wheelsets, Elite and Hunt to name but two.

View attachment 817308

CAAD12 hydro discs lurking in the background, was very avg braking performance until I swapped out the stock SRAM pads, now it’s mega, it would be my travelling bike if the seat post wasn’t stuck 🤣

Have to say that does look very nice.
What inner tubes you using with those wheels? Any issues on steep descents?
I've been tempted to get a lightweight carbon wheelset for my bike but was wondering about the braking to be honest plus how durable they are.

 

[Webbo2]

Ones that came with a set of prime 50mm carbon rims, made by brakco whoever they are.

I have those but I don’t find they stop that well. There is one descent out of Dalby Forrest heading to Troutdale that gives me the willes in the wet and it isn’t that clever in the dry when I’m on my carbon rim brakes.
On my discs I don’t even have to think about it.

 

[itboffin]

What ive noticed on these Ultegra 8150 brake calipers is they have a huge toe in angle, my mechanical Ultegra are flat to the wheel rim, i wonder why the change in design?

 

[Mike Ayling]

AI (Ayling Intelligence) summary.
Disc brakes are much better than rim brakes in the wet.
Hydraulic disc brakes are better than cable disc brakes.
Disc rotors are cheaper than rims and wheel building costs.
Hydraulic disc brakes have better modulation whatever that means.
Disc brakes are much noisier in the wet than rim brakes.
Disc brakes make your bike look extremely ugly compared to the clean lines of a rim braked bike.

 

[T4tomo]

I've been tempted to get a lightweight carbon wheelset for my bike but was wondering about the braking to be honest plus how durable they are.

How durable what is? The rims? Carbon fibre is pretty strong (!) so should be as durable as alu, probably more so. I also have a lifetime crash guarantee, so if I trash a rim, I can just send the wheel back for a rebuild.

I don't do huge miles, but I have noticed the carbon rim specific brake blocks wear quicker, as they are a softer compound. This is a good thing as it means the rim braking surface is barely wearing at all. With Alu rims, you get bits of alu that "peel off" the rim and can embed in the blocks, which unless you remove regularly, exacerbate rim wear.

I found Swiss stop blocks give better breaking performance that the basic wiggle /prime ones that my wheel builder ZED sent with the wheels.

 

[Dogtrousers]

@T4tomo I think the fact that carbon rims are not ideal for rim brakes (heat dissipation problems, need to design and manufacture the braking track) was possibly the key to getting discs accepted in pro racing. A disc brake is just a better engineering solution for a carbon rim.

Remember a few years ago there was quite a push back from the peloton against discs. That all fizzled out I think when I think it became clear that calliper brakes were going whether they liked it or not.

 

[T4tomo]

@T4tomo I think the fact that carbon rims are not ideal for rim brakes (heat dissipation problems, need to design and manufacture the braking track) was possibly the key to getting discs accepted in pro racing. A disc brake is just a better engineering solution for a carbon rim.

Remember a few years ago there was quite a push back from the peloton against discs. That all fizzled out I think when I think it became clear that calliper brakes were going whether they liked it or not.

I whole-heartedly agree, but my best bike was/still is rim braked, so it made financial sense to upgrade the wheels rather than replace the whole bike. Mrs T was also very pleased to get my hand-me-down Fulrum R5s, to replace her awfully heavy OEM stock wheels.

Rim braked carbon wheels are a pretty niche and shrinking market*.

*See also QR skewer disc braked wheels, the Thru axle is a much better engineering solution too, but an equally unachievable upgrade without changing the bike, but I think that's the way I will go with my Gravel cum cycling holiday bike, particularly as I have very little "invested" in it, having bought it used some time ago at about 1/10th of the cost of the best bike!

 

[Binky]

How durable what is? The rims? Carbon fibre is pretty strong (!) so should be as durable as alu, probably more so. I also have a lifetime crash guarantee, so if I trash a rim, I can just send the wheel back for a rebuild.

I don't do huge miles, but I have noticed the carbon rim specific brake blocks wear quicker, as they are a softer compound. This is a good thing as it means the rim braking surface is barely wearing at all. With Alu rims, you get bits of alu that "peel off" the rim and can embed in the blocks, which unless you remove regularly, exacerbate rim wear.

I found Swiss stop blocks give better breaking performance that the basic wiggle /prime ones that my wheel builder ZED sent with the wheels.

Yes the carbon rims. I have no personal experience of them so good to get feedback, some reviews I've read say they are vunerable to wear. I agree carbon fibre is strong but for a friction use ie brake is it really as good as say aluminium?
As for aluminium peel off, yeah I got that a lot from the Hunt rims I had. I was constantly having to remove pads and pick out flecks of alu.

Again I have no experience so question on inner tubes, do you use butyl or TPU etc with the carbon wheels or is it not relevant?

 

[Dadam]

AI (Ayling Intelligence) summary.
Disc brakes are much better than rim brakes in the wet. ✅
Hydraulic disc brakes are better than cable disc brakes. ✅
Disc rotors are cheaper than rims and wheel building costs. ✅
Hydraulic disc brakes have better modulation whatever that means. ✅
Disc brakes are much noisier in the wet than rim brakes. ❌
Disc brakes make your bike look extremely ugly compared to the clean lines of a rim braked bike. ❌

4/6, B: room for improvement

I've got six bikes with hydraulic discs from Shimano and Tektro. Only one of the Tektro* bikes squeals in the wet and then only for a few seconds until it's warmed up. The Shimano have been near silent in all conditions.
* edited to correct: that bike has a SRAM gears not brakes

 

[Alex321]

Where did I say that?

All I am saying is that the stoppers on my one and only rim brakes bike are already more powerful than the chassis can handle, and can stand it on its front wheel (and could flip it if I gave it a vulcan death grip.)

That being the case, how do you believe a more powerful disc brake would stop me in a shorter distance when the rim brake is already providing retardation in excess of the bikes abilities?

In the dry it isn't a huge difference, but even in the dry, it does exist. Mainly about the time & force it takes to reach that maximum stopping power.

You tend to need to apply more force to the levers to get the same stopping power with rim brakes, and while most of us can still apply that much force, it does make modulation that little bit harder, meaning you are more likely to overdo it, and also it will take a small time longer.

For most normal riders, in the dry, the difference is marginal. It i a bigger difference in the wet, because of the time it takes to sweep water from the rim. But even in the wet, most people with reasonable anticipation skills should find it too difficult to brake sufficiently with either system.

 

[Alex321]

I bought a new bike last year, my first with discs, and my biggest gripe is nothing to do with riding it but just moving it out of the garage or lifting it back on the wall rack how the weight of the discs makes the wheel turn just at the wrong moment.

You would find it very hard to wheel your bike out of the garage by the seat which is something I have done for years.

Why would the weight of the discs make any difference to the wheel turning?

Or to wheeling the bike by the seat (not that I have ever really done that)?

 

[T4tomo]

Yes the carbon rims. I have no personal experience of them so good to get feedback, some reviews I've read say they are vunerable to wear. I agree carbon fibre is strong but for a friction use ie brake is it really as good as say aluminium?
As for aluminium peel off, yeah I got that a lot from the Hunt rims I had. I was constantly having to remove pads and pick out flecks of alu.

Again I have no experience so question on inner tubes, do you use butyl or TPU etc with the carbon wheels or is it not relevant?

I use standard / normal inner tubes - I think that's butyl.

I wasn't sure about rim wear pre purchase, but as above, softer blocks and lack of "peel off", I think they probably wear slower than alu.

I'd say the only downsides are, as mentioned wet braking performance is acceptable with the swiss stops, but not brilliant, and the heat dissipation, might be be an issue if I was to do a super long alpine descent - I dunno, not tested that. My tubes didn't explode in the Breckon Beacons, which is the most similar-ish test they've had.

 

[joeegg]

I have a pair of carbon rim brake wheels and the dry braking is not quite up to alloy rims but close enough.Probably better quality pads would equal it up.
A few weeks ago i got a very small stone stuck between the rim and pad when i was braking.From the noise i thought the rim would be gouged.Cleaned off the dust and the rim was perfect.The carbon/resin make up must be really hard.

 

[HLaB]

I've found the biggest advantage of discs is a much better feel and modulation.

I've heard lots of folk say that but I feel rim brakes better, but that's probably because of my chemo damaged fingers, which can be quite numb at times if there's a cold wind. I prefer the more gradual feel of the rim brakes which I then feel in hands which are less numb. The only front wheel I've ever lost was on a disc braked bike on a particularly cold and wet day when I suspect I couldn't feel any modulation because it was in the finger realm rather than the hand. It left me freaked out descents for a long time and uncomfortable on them still.

 

[Webbo2]

Why would the weight of the discs make any difference to the wheel turning?

Or to wheeling the bike by the seat (not that I have ever really done that)?

Because you have a big lump of metal ( the disc) on one side.