Carbon wheel, brake pulsing?

roubaixtom

Hi,

I have a set of Planet X full carbon rims made by Reynolds. The rear wheel seems to be pulsing under braking, as in there is some kind of sticky section on the rear brake track?

What could cause this?

The wheels have only done 500km so should not be anything to do with wear.


Cheers,

Tom

ugo.santalucia

could it be deformed? Or maybe simply out of true...

roubaixtom

It seems pretty true, i can feel an extremely small defamation, however its so small i may be imaging it...

cycleclinic

I have this before on my wheels and then i found changing to campag pad solved this snother braking issues. This assumes there is nothing wrong with thd rims or play in the brake calipers.

mamba80

thecycleclinic wrote:

I have this before on my wheels and then i found changing to campag pad solved this snother braking issues. This assumes there is nothing wrong with thd rims or play in the brake calipers.

yep CycleClinic is correct, clean rim with acetone and use the campag red pad, nothing is better, and set some toe in on the pads

pilot_pete

Check the rim brake track closely all the way round. It sounds very like heat damage which causes the resin to soften and then re-harden as it cools in certain areas around the track. A very common problem with carbon clinchers which just about all manufacturers refuse to accept is down to the poor ability of carbon and associated resins to deal with the heat generated by hard/ continuous braking. They will claim 'incorrect braking technique' despite the fact that the same technique on alloy rims doesn't cause the same problem. I know this from personal experience and that of three mates all of whom have suffered similar damage...funnily enough only on carbon rims and have no problems on alloy rims...

PP

cycleclinic

well of course continous braking does not cause issues on alloy rims because it conducts heat better. Besides good carbon rims do not present with the same issues unless there is real braking abuse. Aluminum rims cannot warp in the same way it metal and melts at 600C although it will loose it strength well before that but it is not possible to get an alloy rim that hot anyway.

Pilot Pete has presented a worst case senario and then gone on to rubbish all carbon rims. Of course we do not know the nature of the failure for him or his mates, what wheels they where using (not all carbon rims are equal) how long ago this happened (modern rim are far better than rim of 5 years ago).

Bad experience is one thing but then to present it as a scare story is another.

mamba80

Pilot Pete wrote:

Check the rim brake track closely all the way round. It sounds very like heat damage which causes the resin to soften and then re-harden as it cools in certain areas around the track. A very common problem with carbon clinchers which just about all manufacturers refuse to accept is down to the poor ability of carbon and associated resins to deal with the heat generated by hard/ continuous braking. They will claim 'incorrect braking technique' despite the fact that the same technique on alloy rims doesn't cause the same problem. I know this from personal experience and that of three mates all of whom have suffered similar damage...funnily enough only on carbon rims and have no problems on alloy rims...

PP

Not saying this isnt the case but....we dont know any of this... supposition at best, has the op even been to the Alps?
braking in the UK isnt likely to fry his rims, esp the rear - Giant and Spesh put full carbon clinchers from mid model bikes upwards.
This guy might be running tubs, but you ve assumed clinchers?

clean the rims, get some 'reds and give the pads a 'mill of toe in.

pilot_pete

He asked what could cause a 'sticky section' on his rear rim, I made a suggestion of what could have caused it. Happened to my handbuilt rims (4 years ago now). This was due to correct braking technique descending big hills. Rims couldn't handle the heat build up.

Happened on two mates Reynolds rims last year and the year before on 'smaller' hills. One guy is 85kgs and the other about 65kgs. Again heat damage causing delamination of the brake track on their wheels.

So, it is not a scare story, it is recounting fact. The OP would do well to consider this possibility and do as I suggested and inspect his rims carefully for delamination, heat damage or anything else that could cause the pulsing.

Remember, he was looking for suggestions as to cause, so just because you don't like hearing that carbon rims can delaminate (and it does not only happen under 'real abuse' when braking) why is what I suggest supposition, but everyone else is talking fact? Sure it is a worst case scenario but who is to say that it is not the cause? None of you can.

PP

Oh and p.s. He mentioned he thinks he can feel a deformation - changing the pads alone ain't gonna deal with that. Question is what caused the deformation? It could be manufacturing issue, which presumably would have showed up from new, some sort of impact damage like a stone chip or scratch or heaven forbid heat damage of some sort.

mamba80

Pilot Pete wrote:

He asked what could cause a 'sticky section' on his rear rim, I made a suggestion of what could have caused it. Happened to my handbuilt rims (4 years ago now). This was due to correct braking technique descending big hills. Rims couldn't handle the heat build up.

Happened on two mates Reynolds rims last year and the year before on 'smaller' hills. One guy is 85kgs and the other about 65kgs. Again heat damage causing delamination of the brake track on their wheels.

So, it is not a scare story, it is recounting fact. The OP would do well to consider this possibility and do as I suggested and inspect his rims carefully for delamination, heat damage or anything else that could cause the pulsing.

Remember, he was looking for suggestions as to cause, so just because you don't like hearing that carbon rims can delaminate (and it does not only happen under 'real abuse' when braking) why is what I suggest supposition, but everyone else is talking fact? Sure it is a worst case scenario but who is to say that it is not the cause? None of you can.

PP

i had a mission with a set shimano c35 carbon tubs that failed (delaminated) on the left hand brake track only, on the front rim, its not nice and can lock the wheel as the brake grabs, this isnt what the OP is experiencing, this is why myself and Cycleclinic think your over reacting.

the slight pulsing he is getting is what i get when the toe in reduces due to wear and build up of residue.

dont take it personally.

pilot_pete

And the deformation he thinks he can feel? Which is how delamination starts....

cycleclinic

And unless I run my own fingers over his rim I cannot comment. my word that sounds rude. I'm going to have a lie down.

cycleclinic

Also there have been sizeable improvements in resins used in carbon rims over the last 4 years.

Smaller hills - mean little. It depends on the braking load. With my own rims there are big descents that would be no problem but there would be shorter descents that might be simply because you have to brake all the time to control speed. There was one in Italy which lasted several km with -10%--20% gradients and given the broken road surface, and the trees causing alot of broken shade I had to brake consistantly from top to bottom. My alloy rims and pads got so hot that the brake pads no longer worked properly. That would have been a decent to kill any carbon clincher. The other decent I did the day before was a 600m drop but it was a main road with sweeping bend and some sharp one. Lovely scenery and the rims did not get warm. That decent would have been fine with carbon clinchers. My own rule of thumb is if the braking load would get alloy rims too hot to handle then a carbon rim would be scorching and you may not want to use them on that decent.

pilot_pete

Exactly, hence why carbon rim braked rims are simply not up to the job. They cannot handle tough descents where brake load is significant or prolongued. Shame NONE of the companies put that front and centre in their advertisements isn't it? At least we agree that 'any carbon clincher' can be killed on a tough descent.

So, back to the OP and his problem. He needs to inspect the rims closely, check for surface damage, deformations, rough spots, glazed spots, pad deposits and structural integrity. Once he has done all that and thinks there is nothing physically wrong with the rim he could try different pads. He should be aware that some pads provide much more bite and will think initially how 'great' they are in that they have improved his braking markedly. The downside is that they are more effective in building up more heat due to having greater friction capabilities, which can in turn lead to rim damage. Be warned. Oh, and don't use your wheels if you ride hills...

PP

pilot_pete

Oh and the obvious long term solution is carbon rims with hydraulic disc brakes, which is the route I have gone, which of course will usually mean a bike change. Absolutely superb and no chance of the rims being damaged due to overheating, no matter what the resin mix...

PP

rolf_f

Pilot Pete wrote:

Oh and the obvious long term solution is carbon rims with hydraulic disc brakes,

Depends what you see the original problem as. If it is "I don't like the appearance of alloy braking tracks' then yours is indeed the obvious solution. If the problem is 'I want to reduce the weight of the bike' then you've bought a new bike and new wheels and achieved nothing! Except better wet weather braking which may or may not be an issue but either way is a completely separate problem.

I think that, through the brakes, a bit of contamination on a rim feels much the same as a physical deformation.

pilot_pete

Rolf F wrote:

Depends what you see the original problem as.

err, brake track problem on a carbon rim no?

Rolf F wrote:

If it is "I don't like the appearance of alloy braking tracks' then yours is indeed the obvious solution.

it is yes, if that was 'another' problem that I'd missed... :?:

Rolf F wrote:

If the problem is 'I want to reduce the weight of the bike'

maybe I missed that one too... :?:

Rolf F wrote:

then you've bought a new bike and new wheels and achieved nothing!

really? What apart from...

Rolf F wrote:

Except better wet weather braking which may or may not be an issue but either way is a completely separate problem.

you appear to be assuming many improvements is nothing... :roll:

Quality hydraulic disc brakes with a carbon (or alloy) rim will give MUCH better dry braking as well as wet braking compared to rim braked carbon rims. Fact.

They will have better modulation, much better feel, you won't have to pull them anywhere near as hard to scrub enough speed off to make that next hairpin during a descent. You can also apply maximum brake force from the hoods, which you can't with a rim brake and a carbon rim.

The rims will never overheat. They will never get hard spots, delaminate (due to overheating) or any braking associated problem that a carbon rim braked wheel can suffer. Much cheaper to occasionally change a disc and (more frequently) disc pads over a delaminated rim with associated wheel rebuild cost.

You can cook your disc brakes and get fade, but correct size disc and pad compound choice can avoid this coupled to correct braking technique. Do this and you will be able to ride your wheels in the hills with confidence. I can't believe that some people are trying to defend carbon rim wheel manufacturers by saying that riding down steep or technical hills etc would 'cook any carbon rim' and therefore it's your own fault for using them! If a rim/ brake combination cannot be used safely (including a margin for ham fisted operator error) then it is simply not fit for purpose. Riding down hill, on a road, no matter how steep is entirely predictable in terms of design modelling etc. Can you imagine a car with brakes that couldn't stop you on a steep hill (assuming enough grip etc).

You can't blow a clincher off the rim due to excessive heat either.

I also don't understand why a non racing amateur should get worried about the 'extra' weight of disc brakes. The benefits far outweigh any slight weight gain over rim brakes. Unless you are at less than 5% body fat, following a strict diet regime and seeking out marginal gains the improved braking, extended carbon rim life and therefore cost saving would appear to favour disc brakes with carbon rims. Save the (added) weight by ditching a few pies a week...

So if the OP doesn't have any damage or deformation of his rim then all is good. He can clean it off, try different pads and carry on riding. My advice would be to be completely aware of the limitations of the product he currently has and be very wary of using them on hilly rides.

If he has got a problem with the rim then of course the cheapest solution is to just fit alloy rimmed wheels and appropriate brake pads. That will get over most issues. If he wants carbon rims then the disc brake route is the way forward in my opinion. My point is that disc brakes coupled to carbon rims makes carbon rims fit for purpose during 'normal' use, which would include riding down steep hills in my book.

PP

mamba80

its not facts, its just your opinions, others have different ones...i ve used my carbon wheels everywhere, TT's RR, Midi Pyrenees even a french RR, no issues at all and one TT was a very hilly sporting TT in the pouring rain last March....

on the other hand a hydraulic shimano braked hire bike i had in Mallorca was was down right dangerous, completely over braked and i swapped it out after a few days.

i would give up cycling rather than be forced to have a disc braked road bike, they are an abomination

pilot_pete

Not facts? :roll:

You believe what you want, I'll stick with what is known to be true. You experienced a badly set up hire bike and therefore claim road discs are dangerous :roll:

Do yourself a favour and take a poll. Ask all the TTers out there how good their carbon rimmed bikes are under braking.... :roll: oh and ask all the guys on the mountain bike forum if they think they are all using inferior brakes... :roll:

You couldn't make it up...

PP

Beauty is in the eye of the beholder and if you think road discs are ugly, I get that. Each to their own. I could throw it back at you that just because you think something is so doesn't make it fact...

mamba80

Pilot Pete wrote:

Not facts? :roll:

You believe what you want, I'll stick with what is known to be true. You experienced a badly set up hire bike and therefore claim road discs are dangerous :roll:

Do yourself a favour and take a poll. Ask all the TTers out there how good their carbon rimmed bikes are under braking.... :roll: oh and ask all the guys on the mountain bike forum if they think they are all using inferior brakes... :roll:

You couldn't make it up...

PP

Beauty is in the eye of the beholder and if you think road discs are ugly, I get that. Each to their own. I could throw it back at you that just because you think something is so doesn't make it fact...

PP your a dork of the first order...... you seem unable to accept any other "opinion" aside from your own, this wasnt a badly set road bike and i have also raced MTB and disc's are a god send but totally not needed for road, apart from the rim wear argument..... even many hi level CX riders dont use disc's..... TT ers arent interested in braking... and in the wet? almost all TT s will be abandoned on a DC course if its pi$$ing down.

my exp of carbon, even my failed C35's are not yours and i d happily buy another set and use them anywhere in any conditions.

just get over your wrong and move on

pilot_pete

No need to get so personal, that is a sure sign you can't just focus on facts...

You brought up the 'no issues' with TTs etc etc etc. Doesn't make rim braked carbon rimmed brakes better. Fact is brakes on the vast majority of TT bikes are crap with carbon rims. As you say, you don't tend to need them, so not sure I get why you would use your TT bike as an example of why they are better? Oh, you didn't say better, merely you hadn't had any issues... :roll:

So your hire bike was set up correctly? Vastly over braked....? better get on to Shimano then as they have obviously have a design fault in the set up you rode. :roll: Or were you just too ham fisted in pulling too hard? You cannot take your one experience and claim it is representative of all disc brakes.

You will throw the argument back that I am doing that regarding my experience of carbon rims. Incorrect. I have personal experience and that of my mates. Add to that the number of grand fundos that banned carbon clinchers due to them being dangerous in the organisers opinions and this represents a known industry problem.

So, in your opinion disc brakes aren't required for road bikes? I actually agree. Alloy rims with decent calipers work fine, especially in the dry.

My point was not that it should be discs or nothing, merely that if you want carbon rims on your road bike they are better suited to a disc brake which will provide SUPERIOR braking in the dry and the wet to a carbon rimmed rim brake. They will also handle descents without issue.

Maybe someone else should do a bit of 'getting over it' and accept that they are arguing the wrong argument... :roll:

PP

mamba80

the very first time i used carbon rimed wheels, i thought jeez these are giving me power & modulation similar to a mtb disc.
and that was in a Gran Fondo in the Dolomites, descending in amongst 100's of riders on some steep declines.

in the wet i ve found them to be fantastic once the initial surface water is removed, as CC said, more modern carbon wheels work well..... to be fair to you, your exp seem to be with older clinchers, i never had carbon clinchers only tubs, though surely th wet weather braking must be the same? pad choice seems to be very important and one pad that is great with one wheel, may not be good on another make.

We possible agree more than you think, so lets leave it at that eh? let the OP try the cheaper option and if in 500km he has fried his rim, well, i ll then move to america,

pilot_pete

:roll:

Lookyhere

My daughter raced all last season on carbon wheels, never had any issues despite several wet races, she also took them to a training camp in the mountains of Southern spain, surprisingly she came home in one piece c/w her un marked wheels.

Many of her friends race on Giant and spesh high end bikes that come as standard with Carbon clinchers, they are all still alive too.

just clean the rims with something with a hi flash point like Acetone and use a decent pad like Reynolds Blue or the campag one.

cycleclinic

I also have been riding and racing my carbon BORG50's for the last nearly three year in the dry and wet and the rims are fine 14000km later. All the people I have sold them too also have the same experience.

So carbon rim brake rim are fine. Brake on them too much and problems can arise but it take real braking abuse. if you have a deep carbon rimmed wheels then you have a set of alloy clinchers. When going somewhere where you will be dragging your brakes down a mountain maybe swap them in. No hardship is it Pilot pete. Why you have started the same old disc brake arguement again I dont know. This thread was not about the virtues of disc brakes (I happen to like them alot) or which rims are best suited for them. As nomral the OP has vanished from the thread as it decends into a trump vs hillary tyoe affair.

pilot_pete

thecycleclinic wrote:

I also have been riding and racing my carbon BORG50's for the last nearly three year in the dry and wet and the rims are fine 14000km later. All the people I have sold them too also have the same experience.

So carbon rim brake rim are fine. Brake on them too much and problems can arise but it take real braking abuse. if you have a deep carbon rimmed wheels then you have a set of alloy clinchers. When going somewhere where you will be dragging your brakes down a mountain maybe swap them in. No hardship is it Pilot pete. Why you have started the same old disc brake arguement again I dont know. This thread was not about the virtues of disc brakes (I happen to like them alot) or which rims are best suited for them. As nomral the OP has vanished from the thread as it decends into a trump vs hillary tyoe affair.

Thank you Hilary. You have now twice in this thread said how technical hills can 'kill any carbon clincher' and now how you should swap to an alloy rim for riding such hills to prevent damage to your carbon rims. :roll:

But of course they are all fit for purpose in your world. :roll:

I will now rest on my laurels in Trump Tower.

PP

rolf_f

Pilot Pete wrote:

Rolf F wrote:

Depends what you see the original problem as.

err, brake track problem on a carbon rim no?

Rolf F wrote:

If it is "I don't like the appearance of alloy braking tracks' then yours is indeed the obvious solution.

it is yes, if that was 'another' problem that I'd missed... :?:

Rolf F wrote:

If the problem is 'I want to reduce the weight of the bike'

maybe I missed that one too... :?:

Rolf F wrote:

then you've bought a new bike and new wheels and achieved nothing!

really? What apart from...

Rolf F wrote:

Except better wet weather braking which may or may not be an issue but either way is a completely separate problem.

you appear to be assuming many improvements is nothing... :roll:

Quality hydraulic disc brakes with a carbon (or alloy) rim will give MUCH better dry braking as well as wet braking compared to rim braked carbon rims. Fact.

Finishing a sentence with the word 'fact' doesn't make the preceding words a fact. Fact. (Actually, in this case it does!).

So, if I find that I can brake with my rim brakes so hard that the back end of the bike lifts, how can disc brakes be MUCH (actually, 'much' on it's own is adequate emphasis - you don't need to capitalise it. It just makes you seem a little deranged) better? Of course, I'm not assuming carbon rims in this case.

As to my 'assumption that many improvements is nothing' - how is it an improvement to have better wet weather braking if, for example, you live in a very dry country or don't ride your posh bike in the rain?

CBA to deal with the other points as you really haven't got what I was getting at at all - maybe I wasn't clear enough or you didn't read it properly. No matter.....

pilot_pete

Of course, I'm not assuming carbon rims in this case.

that's a real shame isn't it as carbon rims is what we were talking about... :roll:

If, for example you live in a very dry country...

yea, let's assume they live in the dry, where all the roads are pan flat, the sun always shines, there is never any need to brake at all and then I grant you carbon rims with rim brakes are just as good. You can't just make assumptions to fit your argument. Look at worst case scenarios such as steep hills with tight bends and the possibility of rain. That is a true test of braking ability and that is where in my opinion disc brakes are superior to carbon rims and rim brakes. You think what you want, I know from personal experience this to be the case.

Now take a chill pill and stop getting personal. Why is it that those who disagree who are losing the argument have to get personal? :roll:

PP

Lookyhere

Pilot Pete wrote:

Of course, I'm not assuming carbon rims in this case.

that's a real shame isn't it as carbon rims is what we were talking about... :roll:

If, for example you live in a very dry country...

yea, let's assume they live in the dry, where all the roads are pan flat, the sun always shines, there is never any need to brake at all and then I grant you carbon rims with rim brakes are just as good. You can't just make assumptions to fit your argument. Look at worst case scenarios such as steep hills with tight bends and the possibility of rain. That is a true test of braking ability and that is where in my opinion disc brakes are superior to carbon rims and rim brakes. You think what you want, I know from personal experience this to be the case.

Now take a chill pill and stop getting personal. Why is it that those who disagree who are losing the argument have to get personal? :roll:

PP

Your the one who makes it personal, with your condescending remarks, you do it with most of your posts eg the ones on cornering, its like you think its your way or the hi-way,

so folk said the OP just needs to toe in his brakes and/or replace with a better pad and then you dive in with that his almost new rims are fcuked and he ll die if he dares uses them on any more than a turbo trainer as they are inherently dangerous!
But 2 US bike manufacturers sell carbon rimmed bikes in the most litigious country in the world, with a huge climate range to boot.

cycleclinic

Pilot pete please dont quote my contributions in support of your argument. You fail to see the nuance in my post. The OP had left this thread anyway.