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My road bike came with the cheap stamped rotors. They started squealing like mad, to an insane degree. I tried to burn them into submission on a really long fast descent and it just made it worse. Last weekend I had to do a steep descent through a peaceful mountain village in an all but dead-end valley and the noise was embarassing, I felt sorry for the poor inhabitants as I destroyed their peace and calm.
Anyway, having had a good look the rotors had worn through the glossy finish and they looked really quite unevenly worn and generally crappy and scored. The pads were slightly concave in the middle. So with that and the persistent noise (I tried every cleaning/bedding in/de-glazing trick that's ever been mentioned on here) I have now binned them and replaced with ice-tech with the aluminium heat vanes on the inside. To be honest I have wanted them for ages cos they look awesome anyway and my experience of the better rotors is much better feel on MTB.
Has anyone noticed better performance either from the fins or the better disc finish/material? I have to use the same pads as whilst I bought new ones the shop seem to have given me the wrong fitting. So I've sanded the old ones flat and I'm going to re-use, as there was over half still left. I'll ride them tonight and let you know how they go. A quick up and down the hill even without bedding in suggests the braking is better but there's still some flutter.
Yes. I took a pair of cheap Shimano brakes down the Snowdon Ranger. The discs were blue by the end, then corroded extremely rapidly from that point on. It was like they had some sort of top layer that couldn't cope. They were just rubbish TBH.
I don't think you need mega-bling rotors either, just not ones that are utter crap.
Also, does anyone else notice that brake pads bedded in during the summer are the worst for braking howl when they get wet?
I've stopped using Ice Tech rotors as they wear out so fast.
This one lasted less than six months.
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Once the braking surface wears, the performance will suffer. It's surprising the difference a new rotor makes. Low-end Shimano rotors are supposed to be only for resin pads. I assume that's because they use a cheaper, softer steel alloy which will wear faster than a better grade of steel. It's not the glossy finish that matters, as soon as the braking surface is noticeably worn, performance will start to degrade.
Is that a visible step on those rotors above - between the spoke and the braking surface? If so, blimey.
I use some cheap Shimano (Tourney, I think) on my road/gravel bike. Centre-lock for £13 each from Amazon, 6-bolt Shimano seem more expensive
Is that a visible step
Yep. It was the alloy core being exposed that's more worrying though.
I've worn the steel version much more than that and they've still worked fine.
I use any discs - never noticed a difference. Avid, shamano, hope, clarks, nameless ones.
Its just a laser cut bit of steel
Of course if discs are badly worn then performance will suffer
Its just a laser cut bit of steel
Some are pressed rather than laser cut.
I've been using some Formula rotors that are made by Galfer on one of my bikes and they're holding up much better.
I would never use old pads with new rotors, especially if you've had noise issues.
I would never use old pads with new rotors, especially if you’ve had noise issues.
Decades ago I read in a magazine that in motor racing, you never bed in new rotors and pads together. I don't know if that's true or not, but there's no reason to fit new pads when you fit new rotors. As long the old rotors aren't utterly trashed, the worn pads will bed into new rotors as well or better than new pads.
the issue with using old pads is that they might take longer to bed in as the surface has conformed to the worn disc
the issue with using old pads is that they might take longer to bed in as the surface has conformed to the worn disc
Sure, if the old rotor is totally knackered. Otherwise, it's not really any different from just bedding in new rotors and pads together. The two surfaces have to wear together.
Yup but if both start off flat then its quicker.
Is that a visible step on those rotors above – between the spoke and the braking surface? If so, blimey.
You can start to see the step about 1/2 the way through the life of a rotor, if it's clean and not badly scored.
Its just a laser cut bit of steel
Some are pressed rather than laser cut.
TBH, i think some of them are just pressed straight off the roll and popped in a bag the way some of them are warped.
Better ones will be cut, blanked out/flattened, laser cut then finished and (probably) heat treated. I think they mostly use martensitic steels, so heat treatment will improve abrasion resistance.
I have never had any noticeable wear on discs and never replaced one
I think this is back to the abrasive friction which creates rapid wear and adherent friction which does not.
I use small discs and hope sintered pads and use them a lot being old and cowardly - result is that my brakes get very hot, remain in the adherent friction zone and thus wear slowly. I get thousands of miles out of pads
Yup but if both start off flat then its quicker.
My guess is that a properly bedded in used rotor that isn't badly worn will be conditioned, so it will have a layer of friction material on it and will bed in new pads faster than a new rotor. Similarly, bedded in pads will have been heat conditioned and provide a better friction surface for bedding in new rotors. I've never had a problem fitting a new rotor with old pads, they bed in just fine.
Aye - maybe more theoretical than making an actual differnce. Seeing as I have never replaced a rotor 🙂
I have never had any noticeable wear on discs and never replaced one
I have a spare parts box with a bunch of old rotors that are worn enough that you can feel it if you run your finger over them. They're still fine for commuting duty, but fresh rotors do make a difference for big descents.
I tend to bend them before they're worn out but it does happen. Especially with crap discs, like those terrible Formula lightweight drilled ones that wore all wavey.
IME, any decent rotor works fine- and if you need a fancy rotor like icetech or whatever it's really curing a problem elsewhere, either your brakes aren't very good or you're dragging and overheating them or something. Bog standard, well made, flat bit of steel, sorted.
I use any discs – never noticed a difference. Avid, shamano, hope, clarks, nameless ones.
They are all decent apart from the crappy cheap Shimano ones that say 'resin only' on them. They are visibly different out of the box, being stamped rather than laser cut, and the finish is different. I had them on my MTB and the brakes always juddered a lot. Then when I replaced them with more expensive ones from Shimano which appear the same as Hope/Hayes etc, the judder went away. So there is clearly a difference.
i've never actually worn one out either. I changed the cheap organic only ones on my MTB because I was going to a bigger size, and then I noticed how much better the proper ones were. In this case I am changing them to try and cure the terrible screeching.
IME, any decent rotor works fine
Yes, I think any decent one will work. I don't think ice-tech is necessarily worth it, especially the ones without the fins - it says that the alu core is there to conduct heat away - but where to? The alu is sandwiched between two layers of steel anyway. It only makes sense with the extra fin. I don't have any long Alpine descents on my local rides but I do have some steep hills with hard stops. I'll let you know if it makes a difference.
I get thousands of miles out of pads
We've done this before. The reason pads wear quickly is due to a specific set of conditions with a certain type of mud. If you don't ride with that type of mud, you don't trash pads in 3 wet rides. I have had pads last thousands of miles AND trashed pads in 3 rides depending on where those rides are.
Its also about the mix of adherent and abrasive friction and getting the pads up to high temps frequently as well as using quality pads
I have ridden in conditions where others trash pads without trashing them. Its much more than your simplistic analysis
Happy to be told what Adherent Friction is
Happy to be told what Adherent Friction is
It's how you tell spaghetti is cooked.
Adhesive friction is two materials sliding past each other and the instantaneous bonds between them being made and broken generates the heat (aka friction).
Abrasive friction is when one of those mateirals is being broken down, and that process of phycially being broken up generated the heat.
In principal 'bedding in' is mostly abrasive, then once the pad and rotor conform to each other and there's pad material on the disc it becomes more adhesive.
If gritty the layer on the disc can get worn away quicker than it can be deposited especilly if the disc doesn't get hot. Then you get the rapid wear
I think that some types of pads and brakes are more reliant on abrasive frictuon. All brakes use a mix.
So brake and pad type and riding style also contibute to the rapid wear as well as environmental factors.
Some designs use much higher pad pressure which will aso akter this
Its much more than your simplistic analysis
Ok but my braking technique doesn't change from when I experience normal pad wear and extreme pad wear. But the conditions do. I know when my pads will be trashed before it happens because I can recognise the conditions. And it hasn't happened for ages since I know how to avoid those kinds of rides.
Sometimes when plodding along a soggy mountain trail in cold rain you don't have the opportunity to get your pads hot, but you still need to brake.
Anyway. The new rotors are a bit better than the old ones, they don't screech, but I would have been better off with new pads as there was some graunchy noises as they wore in.
Yes - so thats only one variable - the conditions. there are other variables - thats my point. Lots of other variables.
someone else with different brakes, different riding styles or even different pads may not experience the same because of the other factors
I've also never had to change a worn out rotor and I was running lightweight Formula ones for years with plenty of riding in steep nasty conditions. I have gone through a pair of pads in one ride when it's been really wet and gritty.
And I also agree that the cheap Shimano rotors are rubbish.
Is this where you tell the people who regularly finish at the pointy end of enduro races that they're braking wrong again. 😂
I've done a set of pads in a day in the pissing rain at Afan masts. It's F all to do with different types of friction, it's riding big fast steep hills in very wet gritty conditions.
Shimano ce thecj are kinda fragile, they look cool, but I don't see any performance gain over standard discs, the steel/alu sandwich probably doesnt help.
My road bike came with the cheap stamped rotors. They started squealing like mad, to an insane degree.
My road bike came with expensive Ultegra ice-tech rotors. They squeal like mad, to an insane degree until super hot, and then squeal again when they cool down. (That's with both Shimano OEM organic and sintered pads, btw. It's bloody annoying....)
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Is this where you tell the people who regularly finish at the pointy end of enduro races that they’re braking wrong again. 😂
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If thats aimed at me I have never done that.
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I’ve done a set of pads in a day in the pissing rain at Afan masts. It’s F all to do with different types of friction, it’s riding big fast steep hills in very wet gritty conditions.
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So why does this not happen with everyone? the year I rode the strathpuffer some folk were wearing a set of brake pads out in a lap or two. I had no appreciable wear after 9. clearly being old and slow I would be using my brakes more. My guess is because of using the brakes more and having small discs I put more heat into them thus stayed in the adherent friction zone and thus did not get that rapid wear which only occurs when you are in the abrasive friction zone. using the brakes less will mean less chance to deposit the material on the disc and less heat meaning you go into abrsive friction.
Disc brakes and how they work and what happens at the pad / disc interface is a highly complex multifactorial thing.
So why does this not happen with everyone?
Pad compound will have a bearing on life. You can buy stupidly soft brake pad compounds which give amazing performance but short life (which is probably what a lot of pro downhillers use...)
A bit like different tyre compounds in F1, for instance
Also, being "slow" puts less heat into brakes compared to a faster rider (assuming the slower rider is not constantly dragging their brakes)
I’ve done a set of pads in a day in the pissing rain at Afan masts. It’s F all to do with different types of friction, it’s riding big fast steep hills in very wet gritty conditions
Ha, I was going to say Afan. I killed a set of pads in a very wet and cold day up there in January. Only time I've ever gone through a set in a day.
Normally my pads last 1000+ kilometers (I don't keep track, but I know I did at least 2000km on some Hope X2s from new) and I've only just retired a set of Hope floating rotors that were new in 2007!
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Now if you want to see fast pad wear then try riding with rim brakes on the Berkshire downs/Ridgeway in winter.
Back in the 90s we'd often wear out a set of pads in one ride - chalk mud + water = abrasiontastic.
Rims would last a winter. I had a pile of rims with scarily concave sidewalls.
So why does this not happen with everyone? the year I rode the strathpuffer some folk were wearing a set of brake pads out in a lap or two. I had no appreciable wear after 9. clearly being old and slow I would be using my brakes more.
I'm aware nothing will change your mind and your single outlier experience but I'll have a go.
I used to do trackdays. Same car, same brakes, same tires. I could get thousands of miles out of tires and brake pads on the road. This is your strathpuffer situation. I could wear through the same tyres and pads in 200 miles at Brands Hatch. Clearly in one scenario it's because I was slamming the brakes on hard and late, heating up the pads and wearing the pad surface away. It was nothing to with whether they were bedded in properly or not.
All pads do is convert momentum into heat (and noise in OP's case) via friction. If you're not going very fast, you won't wear out your pads. I think the pads on my bimbling bike will last my lifetime. In terms of actually usage hours, they'll last hundreds, maybe thousands of 'brake applications' longer than the pads on my full sus.
TJ.
How much descending are you doing?
That has more bearing on brake wear than distance.
I don't do much distance wise but an average week sees over 4000 meters of descent.
My tyre* and brake useage has gone through the roof since I move to the tweed valley.
Milage has dropped but descent figure have multiplied in line with the extra wear.
* Both front and rear.
I'll try once more to explain this: I have read hugely around this because its a puzzle so I wanted some understanding
A disc brake working properly you have this layer of pad material deposited on the disc surface. In the wet and gritty conditions you describe the rapid pad wear what has happened is that this layer is being worn away quicker than it is replaced and thus yo go into abrasive friction not adherent friction and get the rapid wear. When you are slower you use the brakes more ( think about the strathpuffer situation - the energy you are losing thru the brakes is the same - its simply converting the potential energy at the top of the hill into heat in the pads very little pedally for anyone on the descents). A fast rider will do this in short bursts, the slow rider far more time is spent on the brakes but the total energy put into them is the same in both meaning the fast riders brakes have more time to cool off
Its not the same as the car example because the total energy being put into the brakes is the same - the difference is the time over which this energy is put in. .In your track car example yo are putting far more energy into the system
Folk riding similar speeds to me were wearing brakes out really quickly. I was not the only one to not get the rapid wear
different types of brakes with different pad pressures for the same braking effect will alter the point at which this happens
On the tandem this effect is more noticeable because there is far more energy being put in the brakes for the same ride due to the increased weight
Its far more complex and multifactorial than just fast in wet = rapid wear. some slow riders get it, some fast riders do not. Two folk in the same conditions will not always get the same amount of wear
Its about what is happening at the boundary layer and the amount of heat put into the brakes. Its a bit like the swizz cheese theory - multiple factors have to line up for this rapid wear to occur. Heat is a very important part of this.
Disc brakes are one of the most misunderstood things on bikes.
So friction is friction right? Wrong. There are two types of friction when it comes to brakes.
Abrasive friction is the breaking of bonds of both the pad material and the cast iron of the disc when the caliper pushes them together. Adherent (or adhesive) pad material forms a very thin transfer layer of pad material on the surface of the rotor. The two surfaces are the same materials and generate friction by breaking or shearing the bonds in the pad.
Abrasive friction is the wearing of the pad and rotor to change forward motion into heat. Both components wear. Semi-met pads and some non-asbestos organics (NAO) use this type of friction.
https://www.brakeandfrontend.com/brakefriction/
The benefits of adherent friction
Once the brake pad material is sufficiently transferred to the surface of the rotor, it creates what we call sticky brakes. The material transferred acts as a sort of adhesive that literally sticks to the brake pad as it’s being compressed against the rotor. What this does is create a barrier between the pads and the rotors so that the rotor is not being ground down to a powder by the brake pads. What this benefit really means is that your brakes will last significantly longer. Since the rotor is not being ground down the rotors almost don’t wear, which means they will last a very long time without being damaged. There is no brake dust. Again, because there is no wear, there is no brake dust. Your pads will last 10-20 times longer. Adherent friction is not nearly as a destructive of a force so the brake pads are not being worn down as fast. Increased stopping distance. Because there are two forces at work here, adherent friction and pressure, the brakes stop the vehicle up to 20 percent shorter. This is a really important point. We all want brakes that will last a long time, but at the end of the day we want brakes that will save our lives. Having the confidence that your vehicle can stop on a dime every single time is something worth investing in.
https://www.pureforge.com/blog/abrasive-vs-adherent-part-2
So the point is that you get this rapid wear when you are in abrasive friction not adherent friction
different brakes, different riding styles, different pad formulations are factors that alter the point at which yo go from abrasive friction into adherent friction
Its far more complex than just fast rider in wet and gritty conditions = rapid wear
I just uses super cheap unbranded rotors. I can’t tell the difference. The last pair were 8.99 from Amazon for 200mm. Pads seems to last fine in all but horrendous conditions. When they’ve squealed it’s often been due to contamination with oil from somewhere.
In my experience the problem is caused when it's wet enough to hold a film of water between pad and disc, which holds grit. This means there's alway grit between rotor and pad which obviously means loads of wear. One memorably wet Polaris Challenge I managed to preserve the remainder of my pad material by stopping to blow the water out of my calipers after a big puddle.
Some people may avoid the puddles and hence not get that film of water, some people's bikes may be less susceptible, maybe going faster or slower through the puddles makes a difference to how much of a soaking they get. It may be that different rotor patterns hold or clear water better in these conditions.
I don't think the microscopic layer of pad material on the rotors makes any difference when the whole thing is dunked in grinding paste being squeezed together. Cars don't have this problem because they're not sprayed on in the same way being inside a wheel. You never get a grinding sensation through the pedal like you do on a gritty MTB ride when driving. Although rough discs due to rust can certainly be felt.
When they’ve squealed it’s often been due to contamination with oil from somewhere.
It can be the case, on road especially since there's all sorts of crud in roads from cars, diesel, oil spills etc. But in my case I'd cleaned them carefully many times.
Re heat, this problem got way worse after getting them really hot one time.
But in my case I’d cleaned them carefully many times.
Clean away but unless you have changed both components you have not eliminated the contamination merely reduced it.