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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[url= https://live.staticflickr.com/65535/52290964357_4063c713fa_c.jp g" target="_blank">https://live.staticflickr.com/65535/52290964357_4063c713fa_c.jp g"/> [/img][/url][url= https://flic.kr/p/2nELRUZ ]Alloy core showing.[/url] by [url= https://www.flickr.com/photos/stu-b/ ]StuartBrettle[/url], on Flickr
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.
Adherent and abrasive frictions merely describe two process of friction. There are multivariate other factors at work in the wear of a disc which is a separate thing. You may eliminate the lions share of abrasive friction and still suffer physical disc wear.
TJ, by your own admission you're old and slow. You may be using your brakes alot, but you're braking from a low baseline. Even if they get hot, they're not dealing with very high torque whilst hot, because speeds and thus forces are comparatively low.
Also, slow speeds in pants conditions means theres far less debris thrown up and less grinding paste in the brake system - we all slow down for deep puddles to avoid a massive splash right?
You see this with faster riders all the time in poor conditions - proportionately they're far more caked in clart that us joe ordinarys.
I've spoken before on adherent and abrasive friction being in a constant state of flux throughout a ride at any instantaneous moment.
What is the readiness of the pads to deposit fresh material on the disc- Have the pads cooled since their last use?
How much pad material was laid on the disc during the last braking event (or was it worn off)?
how hard are the pads?
How hard is the disc? Not all steels are the same.
How much braking force is required?
Is the brake contaminated with trail debris?
How much debris is there?
How hard is the debris?
Will the next braking event be long enough to built adequate heat to deposit a layer of material on the disc, or will it wear away the layer on the disc because it doesn't get hot enough?
Ad infinitum.
Its clear to me from my own experience that hard aggressive use wears discs and pads quicker irrespective of conditions. This shouldn't be a surprise.
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.
Them were the days! Used to regularly do the same in the peak district.
Oh what fun to blow the entire side of your rim off, ruining both wheel and tyre, due to worn concave rim giving way under tyre pressure, way up high on Jacobs ladder in the snow, when it was getting dark and you still had to ride back to Macclesfield.
Its clear to me from my own experience that hard aggressive use wears discs and pads quicker irrespective of conditions. This shouldn’t be a surprise.
of course - but the materials science is clear - its when you get into just abrasive friction zone you get this wear out in a few miles issue which is not the same as greater wear due to hard useage
From previous discussions on her there are some fast riders who do not get the ultra rapid pad wear, there are slow riders who do
Grit on the disc surface is only there for one turn of the wheel. Its cleared by the drilling in the disc
As above - its not just about speed and conditions - there are many other factors. I have linked to some of the materials science in an earlier post. Its when all the factors line up to mean you are in the abrasive friction zone only then the pads wear out in a few miles
Ive tried to explain it. I have linked to articles that explain it, I have read widely around the topic because I was puzzled and that the conclusion I came to based on a lot of good materials science
Its complex and multifactorial. its not just fast rider in poor conditions = rapid wear.
Disc brakes and how they work is one of the most poorly understood things on bikes.
he 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.
From the link on the previous page
I am merely trying to explain why some folk get the rapid pad wear and some do not
Some fast riders get it, some do not. some slow riders get it, some do not. two folk on the same trail at the same speeds one might get the ultra rapid wear from being in the abrasive friction zone and one might not
too many folk just want to shout me down rather than listen to the argument.
I'm out
there are other factors than simply speed ad conditions. when allthese factors line up you get this ultra ra[pid wear
Its clear to me from my own experience that hard aggressive use wears discs and pads quicker irrespective of conditions. This shouldn’t be a surprise.
You mean like they are being asked to do much more work than people going for a bumble.
Of course - its obvious that would be so. You will get more wear
However that does not explain this ultra rapid wear. that is explained buy the abrasive friction issue as above
As above - some fast rider do not get the rapid wear some slow riders do
I'm sure we've discussed this before and it's down to you running relatively small rotors as I do the same on winter bikes? It was down to running ostensibly rubbish brakes that ran hot that keeps the system bedded in rather than wearing out. Running 160/160 brakes in crappy conditions resulted in less pad wear than bigger brakes.
It's a massive compromise though, I'm happy to accept slightly crap braking on familiar trails on a mid week nightride where I'm just enjoying being out and about, or on the gravel bike where I want to be able to ride hundreds of miles in filth.
I'm not happy with that compromise on a bike I want to ride flat out downhill because it's not really very fun as there's not enough power.
Grit on the disc surface is only there for one turn of the wheel. Its cleared by the drilling in the disc
Is it? There's usually grit on the surface of the pads too, a bit more moisture and that grit deposited in the drillings can wash back on to the surface/pad face, once it's in there it take more than one revolution only the rotor to clear.
I Went for a moderately mucky ride yesterday, hosed the bike off after but still hadn't washed all the grit out of the rear brake, that could still be heard grinding away betwixt pads and rotor. In Berkshire as mentioned before, so there's a nice mixture of chalky mud holding various types of grit and puddles don't drain away in April, I've had pads go within a handful of wet rides round here without a particularly urgent pace on my part.
It's inevitable that you'll add some sort of extra abrasive materials to the braking surfaces, it just depends where and when you ride as to what the characteristics of that material is and how it affects pads/rotors...
As above – some fast rider do not get the rapid wear some slow riders do
This is the bit I don't really agree with.
I think theres a commonality of factors that produces broad bands of comparably similar wear for a given case use. Its then modified by particular equipment choice and braking style.
It is a bit weird that you acknowledge multivariate factors as inputs, agree that it's complicated and poorly understood but then bang the adhesive/abrasive friction drum quite loudly as the only factor.
Ta Tinas - thats the theory - brakes that run hotter are less likely to get into the abrasive friction area due to depositing the boundary layer more quickly. Being slower means dragging the brakes more meaning they get hotter. smaller discs run hotter
disc brakes need the heat to work properly Hundreds of degrees C
thats one of the factors
It is a bit weird that you acknowledge multivariate factors as inputs, agree that it’s complicated and poorly understood but then bang the adhesive/abrasive friction drum quite loudly as the only factor.
Its when you get into the abrasive friction zone you get the ultra rapid wear. Multiple factors govern at what point you tip into the ultra rapid wear. Fast riders are more prone to this as they use the brakes less meaning the brakes run cooler, bigger discs mean they run cooler
there is a difference between more wear because of more energy in the braking system and the ultra rapid wear from going into abrasive friction
Abrasive friction wears out brakes much more quickly than adherent.
As above – some fast rider do not get the rapid wear some slow riders do
This is the bit I don’t really agree with.
thats just what I have gathered frommany discussions of this on here. Nowt hard to back it up other than what folk have said on here
Edit: and also from what I saw at the puffer. Some fast riders got the ultra rapid wear, some did not. Some slow riders did, some did not
I have never had any noticeable wear on discs and never replaced one
Same. I've wondered if they're thinning and becoming weaker, though I've never measured them so can't tell. Certainly not noticed any real wear on the braking surface. Live in a hilly area so they get used hard and do thousands of miles on and off road. Always use sintered pads.
tjagain
I’m out
yeah I know. Stoopid me 🙂
Grit on the disc surface is only there for one turn of the wheel. Its cleared by the drilling in the disc
Thats a massive a hugely inaccurate statement for starters (or stoppers?)
Grit stays on mine for long periods of time, you can hear it as you brake.
Clean away but unless you have changed both components you have not eliminated the contamination merely reduced it.
Quite, but these aren't my first set of discs and not only have MTB brakes not squealed anywhere near as much but they've always responded to the cleaning I've done. Something is different here, probably the amount of heat in the short term and the number of miles on a set of cheap discs.
Grit on the disc surface is only there for one turn of the wheel. Its cleared by the drilling in the disc
Yeah no. It hides somewhere, presumably in the holes, and it stays for a while as anyone with ears will testify.
I am merely trying to explain why some folk get the rapid pad wear and some do not
I appreciate that but we don't think you're right.
the materials science is clear – its when you get into just abrasive friction zone you get this wear out in a few miles issue
It's not the abrasive friction between pad and disc. It's the abrasion caused by the grit which is being held there by all the water in the caliper and in the holes.
I have never had any noticeable wear on discs and never replaced one
How do you know? The tolerance on a new disc vs what the manufacturer say is worn one is c. 0.25mm.
You wouldn't even know unless you were measuring.
Paid ~£40 per 160mm rotor for https://www.merlincycles.com/shimano-xt-mt800-ice-tec-centrelock-rotor-180696.html recently for these to fit to my yet to be setup VEL 50 RL wheelset, because they were a bit cheaper than the https://www.chainreactioncycles.com/shimano-ultegra-rt800-ice-tech-freeza-rotor/rp-prod161380 I've had on another wheelset for four years, plus appparently the MTB version has stronger arms to the rotor and is often used by roadie pros (even though the extended road fins look cool IMO)...
Just looked as result of this thread and they are now ~£28 each, bargaintastic.
The new ones I just bought say Ultegra/GRX/Deore XT on the box...
This thread has inspired me to get round to sorting my brakes out.
Got 2x180mm SLX - RT66 rotors from Wiggle for a tenner each (last ones apparently - though CR may have some at that price) Less than half the price elsewhere