Dura Ace C24 wheels - sticky brakes issue

by Zermattjohn   June 24, 2014  

Hi all - I've been experiencing shuddering/throbbing brake issues with this wheelset. I've got Dura Ace brakes too, and the pads are new but I get a real "pulsing" feel when braking. Its pretty disconcerting and sometimes means that the rear locks up it it grabs the rim. It almost feels like the wheel is out of true, or has oil on half the rim, neither of which is the case. I've used Ultegra wheels and the issue doesn't occur, so its got to be something to do with either the rim being faulty, or the brake pads being incompatible. However the rim on both Ultegra and Dura Ace C24 is alu...? Anyone else experienced this issue? I've had a few pairs replaced as the supplier agreed there was a problem, but it keeps happening with each replacement. Pulling my hair out - the wheels are great when you don't want to slow down!

20 user comments

Oldest firstNewest firstBest rated

Few threads on WeightWeenies mention the same thing, but no one seems to be able to solve it.

glynr36's picture

posted by glynr36 [428 posts]
24th June 2014 - 10:44

3 Likes

I did read on there, or somewhere, that using carbon-specific brake pads helps as, even though the rim is alu, due to the carbon laminate there's an amount of carbon on the rim. But, also that these brake pads are very wearing for the rim - these wheels are £600 so am loathe to risk destroying the rim.

Zermattjohn's picture

posted by Zermattjohn [69 posts]
24th June 2014 - 10:55

1 Like

I have the same problem with Shimano RS80's.Local bike shop trued the wheel and i moved my pads a bit further out.Its better but but still not smooth.
I put a short straight edge along the rim and found one area with a small dish.
Looks like a machining fault on mine that can't be trued out.
Did a wet ride a couple of weeks ago with some steep descents and i was on my nerve ends with the grabbing.

joeegg

posted by joeegg [37 posts]
25th June 2014 - 9:05

0 Likes

Isn't it amazing how poor new wheels can be? Obviously they churn them off a production line, but to me, more than £400 is enough to spend on something for them to have been at least quality-checked before going out the door.

I don't think its a minor dish/out-of-true issue, as I've been through 4 pairs and each pair has the same issue, sometimes one wheel sometimes both. I'm thinking it must be the brake pads, though you'd think Dura-Ace alu specific pads would work very nicely thank you very much with Dura-Ace alu rims...

Zermattjohn's picture

posted by Zermattjohn [69 posts]
25th June 2014 - 11:31

0 Likes

Interesting thread...I too have C24's on my bike and am currently experiencing the same thing. At first I thought it might be the brake pads so I had them changed...but the pulsing sensation persists. Not terribly annoying, but on down hills I definitely feel it more. Interested in hearing what others think...

regman

rnarito's picture

posted by rnarito [30 posts]
25th June 2014 - 12:22

0 Likes

That's weird, I've got RS80s (same rim) and have never had this. I think I briefly used shimano pads but have been using Swisstop greens for the last few years.

Assuming the wheels are true, have you checked the calipers are pulling evenly on both sides? Are your pads toed in slightly? Are the rims clean? Is your headset tight?

posted by bashthebox [645 posts]
25th June 2014 - 12:26

1 Like

Have you taken a close look at the braking surface?

I thought that my Dura-Ace front wheel had gone out of true because it was grabbing under braking. However, when I put the wheel in the stand, it was perfectly true.

Drove me nuts until I checked out the braking surface. The bit that was grabbing was a tiny raised blob a couple of millimetres across in the middle of the brake track: a little irregularity in the surface.

I've never seen this before on a braking surface. It seems like the metal around it has gradually worn as a result of braking, but this little blob hasn't. Presumably that means it's harder than the surrounding metal??

Anyway, I wore down this blob - tiny screwdriver, careful use of glasspaper (don't blame me if it goes wrong) and braking is back to normal.

I only did this a couple of weeks ago. I imagine I'll have to repeat the process in time.

I'd be interested to know if it's the same issue with your wheels.

posted by Mat Brett [1887 posts]
25th June 2014 - 12:36

1 Like

I have to say I haven't seen anything obvious on the braking surface. However, as I've been through 4 pairs its pretty odd that the same issue arises on all of them - must be some manufacturing issue? I can't check them at the moment as they've gone back to the supplier (again!)>

Zermattjohn's picture

posted by Zermattjohn [69 posts]
25th June 2014 - 13:18

0 Likes

Braking surface on mine is perfect. Pads are centred.Its the rear wheel only and the slight inward dish is at the joint.The dish is only about 3 cm long so its not a trueing problem.

joeegg

posted by joeegg [37 posts]
25th June 2014 - 17:10

0 Likes

Highly likely its on the weld/join line - the metal will be more brittle and wear resistant from the heat imparted during the process - as a result the metal wears down faster around it

posted by macrophotofly [36 posts]
26th June 2014 - 10:41

1 Like

But its there from the 1st day, so no wearing at all until the 1st brake squeeze. Plus, never felt this on other wheels that must be built in a similar way...

Zermattjohn's picture

posted by Zermattjohn [69 posts]
26th June 2014 - 11:13

0 Likes

Having major problems with my c24 wheels, already had them back to my LBS for a really loud ticking noise under braking, that got sorted, now the rear wheel is screeching under braking, loads of buzzing vibration through the saddle, it's like you say grabbing the rim and feels sticky. I've cleaned the rim and its just getting worse and worse, disgraceful from shimano on wheels that are so expensive.

posted by tonyhogg [62 posts]
26th June 2014 - 17:32

0 Likes

I have the same problem with RS10's, what is strange though is when I put a different wheel on that does not pulse, there is a significant reduction in breaking. Apart from the actual wheel, everything else is the same, so this leads me to think its something to do with the breaking surface. Heat dissertation could be a cause as the rotating energy is transferred to heat energy, especially as it seems this is a rear wheel problem, but Im struggling to accept that it would be some much that its so noticeable.

For me, the better performance outweighs the pulsing, and its kinda like having ABS on a bike.

Has anyone asked Shimano

posted by jason.timothy.jones [303 posts]
27th June 2014 - 8:40

0 Likes

ABS on a bike - that's a good way of looking at it. I agree, perhaps the braking surface is almost "too" good, and Dura-Ace brakes/pads themselves are pretty grabby on my Ultegra wheels (which admittedly have a year's more wear on the rim). In terms of heat dispersion, I discount that as it happens the instant I apply the brake, rather than builds through the braking period.

Interesting, though I'd rather it didn't happen.

Zermattjohn's picture

posted by Zermattjohn [69 posts]
27th June 2014 - 9:12

0 Likes

The old 7850 CL C24 wheels used to actually have a caveat in the user instructions that said they didn't recommend the use of their own Dura Ace pads. They are notoriously abrasive, and the thin and fairly delicate rim surface of the CL wheels gets eaten pretty quickly.

I see a fair few wheels with grabby rims, and usually a good going over with a rim rubber and then clean with water sorts them out, especially if they are new.

Swissstop Rim Rubber

I would recommend going to Swissstop Greens on theses rims, they are so much gentler on the surface, and braking performance is generally better.

Complicating matters since 1965

DaSy's picture

posted by DaSy [649 posts]
27th June 2014 - 11:36

3 Likes

DaSy is right. Use SwissStop pads and clean your rims regularly with the rim rubber.

I have 7850s and RS80s and do not suffer from this braking problem either on the steel bike (105 brakes) or the carbon bike (6700 brakes).

However I do suffer from this problem on the front wheel of the fixed bike, which has a 28H IRD Cadence magnesium-alloy rim (Shimano 600 brakes, Kool Stop Salmon pads). This has been extensively investigated and my conclusion is that it's a wind-up effect: the wheel seems to hit a resonant frequency with the steel fork, setting up a shimmy in the longitudinal plane.

The 16/20 spokes in the Shimano wheels under discussion are highly tensioned and if even slightly out of tolerance on the +ve side, this must impart a lateral run-out to one side, then the other.

harman_mogul's picture

posted by harman_mogul [137 posts]
27th June 2014 - 11:59

1 Like

Exactly the same problem here with my Dura Ace C50 9000 wheels. I'm on my second set and Shimano Australia said they were aware of a problem but not everyone experiences it. I've tried:
- Kool Stop Salmon pads and that helped the most but not great still
- Very fine sanding of the brake track which helps slightly
- Truing the wheel - I have a set of dials on my truing stand and you can see a very slight blip in a couple of places on each wheel but no more than other wheels. It's more of a surface problem than a truing issue I think.
- Tightened everything as per everyone's instructions (head stem, skewers etc.)
- Less tyre pressure
- More tyre pressure
The front is worse than the back and much worse at slower speeds. After recent rain fall it has become very pronounced again, even with the Kool Stops on.

Frustrating for a $1,500 set of wheels!

posted by Rebem [1 posts]
8th August 2014 - 12:38

1 Like

Yep, I'm now on my 5th pair of these wheels! I got some SwissStop green pads, definite improvement on the Dura-Ace pads but still the same issue, particularly on the front. I was recommended to try sanding the pads this week, so have done so, not tried out yet. I also got a rim-rubber which is possibly the daftest item in my bike-toobox, doesn't seem to do very much more than soap and water does...! If this still goes on after these latest attempts I think its time for a full refund and to buy something else.

Zermattjohn's picture

posted by Zermattjohn [69 posts]
8th August 2014 - 12:50

3 Likes

the Concept of a Rim Rubber is sound, what you get for your money is rubbish.

I use a normal pencil eraser from the supermarket, it does take all the very fine grist and crap away quite nicely, I cant say it make braking much better, but the rims look sexy

I use the same thing on my Diamond Steel (the type used for honing knives) this makes a remarkable difference

posted by jason.timothy.jones [303 posts]
8th August 2014 - 13:15

0 Likes

I had exactly this problem on the front wheel of a pair of RS80 C24s. Braking while descending was particularly unpleasant

I had the wheel checked over by wheelbuilding guru Paolo Coppo (http://paolocoppo.drupalgardens.com/). He found that the spokes were evenly tensioned and the wheel was true, but he when checked with a micrometer, there was a lot of side-to-side movement of the rim between each spoke. He concluded that the rim isn't rigid enough to be supported by such a small number of spokes.

In a nutshell the wheel either needs more spokes or a stiffer rim. This seems to make sense, as I have a pair of Ultegra 6700 wheels, which are effectively the same wheel but with a heavier rim, and there isn't the slightest trace of pulsing when braking.

As a footnote I've since had a pair of 24 hole HED Ardennes rims built up on Dura Ace hubs by Paolo, and they knock spots off both the RS80s and Ultegras. They roll better, brake better, are more comfortable and they can be repaired whenever needed. All for the same sort of money and just a teeny bit more weight!

posted by philshems [1 posts]
8th August 2014 - 17:44

1 Like