Swiss Riders Disc Brakes fail on Descent
Discussion
I don’t like disc brakes on road bikes ( even though my latest bike has them ) they are prone to serious fade if you’re not careful, on a long descent. It’s all about the modulation, and hoping you started with enough brake material left on the pads. People in general seem to prefer them, so resale values are going to be higher on disc braked rigs. I still really don’t like them on road bikes though.
BrundanBianchi said:
I don’t like disc brakes on road bikes ( even though my latest bike has them ) they are prone to serious fade if you’re not careful, on a long descent. It’s all about the modulation, and hoping you started with enough brake material left on the pads. People in general seem to prefer them, so resale values are going to be higher on disc braked rigs. I still really don’t like them on road bikes though.
I agree, and its not like you can jam it into a lower gear like you can in a car, if they go you better hope for some run off for you to pull over and pour water or wee on them. Mine are full hydraulic and not top end, its a £700 Giant. 40mph plus downhill scares me but it stops OK.
Article lists two accidents but one was due to hitting a stone so nothing to do with brakes, lets clear all the stones off the roads!
There used to be tales about glue overheating and tubulars coming off so long downhills have always been risky.
As with everything it has to be specced to take the expected loads and the riders need to know the limits so are we going to see discs on flat stages and rim in the mountains in the same way that we see disc wheels on the flat time trials but not the hilly ones.
Article lists two accidents but one was due to hitting a stone so nothing to do with brakes, lets clear all the stones off the roads!
There used to be tales about glue overheating and tubulars coming off so long downhills have always been risky.
As with everything it has to be specced to take the expected loads and the riders need to know the limits so are we going to see discs on flat stages and rim in the mountains in the same way that we see disc wheels on the flat time trials but not the hilly ones.
I turned a rear road bike Ultegra brake disk blue with the heat build up braking on the Honister Pass descent into Buttermere. New bike so new pads, 140mm disc and fluid. 93kg bike and rider. No brake pad fade but I can imagine a sustained descent being a problem.
Edited by ian in lancs on Thursday 20th August 18:41
frisbee said:
What a pointless article. Absolutely no attempt to explain why they failed just, disk brake!
Agreed - it gives no detail. As pro you'd expect him not to be dragging the brakes down a descent, so unlikely (but still possible) to be boiled brake fluid or horribly glazed pads.If a rider does drag the brakes, I wonder how rim vs disc differs (ie are discs more dangerous)? I did find this article via Google:
https://www.cyclingweekly.com/news/product-news/is...
CW said:
Michael Adomeit, Head engineer, Canyon Bikes
Heat dissipation is certainly an important issue in the development of disc brakes. It is actually the reason why we see technologies like Icetech or Freeza or ceramic pistons.
In the summertime we carried out some brake heat testing in the Black Forest, simulating an anxious, heavy rider.
With 120kg system weight and just using the front brake, we were going downhill for 8.6km on a nine per cent average slope.
Repeating this test several times we could not provoke any fading.
I am convinced that a rim brake would have troubles to pass this scenario, especially with carbon rims.
A shame they didn't include rim braking in the test to prove (or disprove) the last statement.Heat dissipation is certainly an important issue in the development of disc brakes. It is actually the reason why we see technologies like Icetech or Freeza or ceramic pistons.
In the summertime we carried out some brake heat testing in the Black Forest, simulating an anxious, heavy rider.
With 120kg system weight and just using the front brake, we were going downhill for 8.6km on a nine per cent average slope.
Repeating this test several times we could not provoke any fading.
I am convinced that a rim brake would have troubles to pass this scenario, especially with carbon rims.
I’ve got 160mm discs on a Campag hydraulic system, and on a 60 Kph descent, they really did fade badly after about 5 seconds full on braking. However, switching / blending between full front and full rear, and modulating kept them in the ‘keen zone’. I could imagine smaller rotors and a nervous rider causing issues, if they got spooked by the difference in full initial bite and faded.
From riding MTB discs for over 20 years now , there is reasons behind discs 'failing'. But as a whole, discs are far better than rim brakes.
Most modern discs on road bikes have a semi sintered brake material in them . This can create massive friction, which in turn can overheat the discs . The brakes are not always the problem with hydraulics , but more from pad materials and disc materials.
Semi sintered are a half way house between resin and fully sintered.
From riding in Spain with my MTB's off the sides of some long drawn dusty, rough descents. Using the wrong pads can make the difference between stopping or grinding , with smoke, no stopping ! and destruction.
Most new OEM pads have metallic compounds in them and they are there to cover most situations of riding. I have destroyed discs from new to dead in one days riding for using OEM semi sintered supplied pads. The guys in Spain who live there, use resin pads. They offer a great amount of grip, they have a sensible lifespan ( a week in Spain on a set with me being a pansy is good) and disc wear is virtually none. But if you use them in the wet, they wont be as good and longevity disappears. I learnt my lesson and only take resin now and a pair of sintered incase of rain. Takes 5 mins to swop out.
In one sentence , people moan when pads wear out in a week, moan when they squeal , moan when they have no feel , so why do cars of a race spec have so many options ?
I had the destroyed rear disc analysed by a friends customer and said that the heat cycles had softened the disc and that was causing an even faster rate of disintegration.
Problem is that road disc brakes , are very small. Not all of us are elite and loose half our mass having a poo. The pro's ride at speeds we would be scared witless at. As to the teams using what is supplied from the bike manufacturer. It maybe something they need to look further into, as it is is pretty rare that the modern hydraulic systems fail, more the pad material and disc size.
If I could, I would still rather have a road bike with discs. Rim brakes for me, give me no confidence at all on steep descents and actually make me slow down early on than hope they work.
Most modern discs on road bikes have a semi sintered brake material in them . This can create massive friction, which in turn can overheat the discs . The brakes are not always the problem with hydraulics , but more from pad materials and disc materials.
Semi sintered are a half way house between resin and fully sintered.
From riding in Spain with my MTB's off the sides of some long drawn dusty, rough descents. Using the wrong pads can make the difference between stopping or grinding , with smoke, no stopping ! and destruction.
Most new OEM pads have metallic compounds in them and they are there to cover most situations of riding. I have destroyed discs from new to dead in one days riding for using OEM semi sintered supplied pads. The guys in Spain who live there, use resin pads. They offer a great amount of grip, they have a sensible lifespan ( a week in Spain on a set with me being a pansy is good) and disc wear is virtually none. But if you use them in the wet, they wont be as good and longevity disappears. I learnt my lesson and only take resin now and a pair of sintered incase of rain. Takes 5 mins to swop out.
In one sentence , people moan when pads wear out in a week, moan when they squeal , moan when they have no feel , so why do cars of a race spec have so many options ?
I had the destroyed rear disc analysed by a friends customer and said that the heat cycles had softened the disc and that was causing an even faster rate of disintegration.
Problem is that road disc brakes , are very small. Not all of us are elite and loose half our mass having a poo. The pro's ride at speeds we would be scared witless at. As to the teams using what is supplied from the bike manufacturer. It maybe something they need to look further into, as it is is pretty rare that the modern hydraulic systems fail, more the pad material and disc size.
If I could, I would still rather have a road bike with discs. Rim brakes for me, give me no confidence at all on steep descents and actually make me slow down early on than hope they work.
t. I'm outRecon it's an excuse tbh, I could understand if his team were sponsored by SRAM but it's Shimano who put in a lot of R&D to their products and will have tested the brakes extensively on a dyno to simulate every eventuality and add in some margin ontop.
SRAM hydro brakes had a habit of the piston sticking and not retracting a few years back due to the plastic material absorbing the brake fluid, I was caught out by this and will never use them again for this reason.
SRAM hydro brakes had a habit of the piston sticking and not retracting a few years back due to the plastic material absorbing the brake fluid, I was caught out by this and will never use them again for this reason.
ChocolateFrog said:
I've done 20km+ descents at average speeds over 60kph (I'm over 100kg) and although the tyre bead had melted onto rim by the bottom the brakes were still surprisingly good and they're only standard 105 fair.
Not sold on upgrading to discs.
I'd be very worried about a blow out in that situation! Way too much heat going through the rim.Not sold on upgrading to discs.
I weigh something similar and regularly do full summers in the alps. I'll go with disks everytime. Much easier to modulate and much more responsive.
NorthDave said:
ChocolateFrog said:
I've done 20km+ descents at average speeds over 60kph (I'm over 100kg) and although the tyre bead had melted onto rim by the bottom the brakes were still surprisingly good and they're only standard 105 fair.
Not sold on upgrading to discs.
I'd be very worried about a blow out in that situation! Way too much heat going through the rim.Not sold on upgrading to discs.
I weigh something similar and regularly do full summers in the alps. I'll go with disks everytime. Much easier to modulate and much more responsive.
stuarthat said:
Not the first time disc brakes have caused accidents on tour ,seems long descents at high speed some at over 60mph ,seen Alex on YouTube talking about the issues with discs .
You could say the same for rim brakes.You could say that most of the bicycles that have been crashed on the TDF have had rim brakes, so everyone would be safer riding disc braked bicycles.
rastapasta said:
BrundanBianchi said:
I don’t like disc brakes on road bikes ( even though my latest bike has them ) they are prone to serious fade if you’re not careful, on a long descent. It’s all about the modulation, and hoping you started with enough brake material left on the pads. People in general seem to prefer them, so resale values are going to be higher on disc braked rigs. I still really don’t like them on road bikes though.
I agree, and its not like you can jam it into a lower gear like you can in a car, if they go you better hope for some run off for you to pull over and pour water or wee on them. Gassing Station | Pedal Powered | Top of Page | What's New | My Stuff