So what is the definitive answer about noisy Dura Ace rotors?

[tommyboyo]

I have read so much about why some disc brake rotors make such a racket for a short time after heavy braking, but never got a truly definitive answer.

For me, it's my front DA 9100 rotor and the only thing that really annoys me about disc brakes.

Here are the theories that I have read that I can remember...

1) Poor setup of calipers (either alignment, or bleed etc).
2) Warped rotor out of the box.
3) Expanison of fluid in system, meaning pads are slow to retract after heavy use.
4) Warping of material in rotor after heavy use (160mm seems much much worse than the 140mm on the back)
5) Damaged/faulty caliper, maybe at the seal.

Always worse in hot weather as well, which seems weird when you think of the few degrees difference in ambient temps compared to the massive heat being generated in the system when braking.

Anyway, mine is so noisy for 5-15 secs after braking and then back to silent.

For everyone who complains though, you seem to get someone else who says that their setup is silent, so just wondering if anyone can categorically explain why it seems to be a big issue for a number of people running the Dura Ace rotors and by extension, what the cause is?

[BianchiDave]

Assuming everything is set up correctly, and the disc isn't warped at all, I've found it's normally just the pistons being slow to retract. Ironically on rougher roads the bouncing of the front wheel seems to help them on their journey back into the caliper.
It's a good idea to 'exercise' the pistons every few months (ymmv). Plenty tutorials online, Park Tool do a very good one - it's shown on an mtb but the procedure is exactly the same. It helps to have an assistant pump the brake whilst you hold in one piston and exercise the other -
https://youtu.be/vQXFFgRButo

[OnTheRivet]

As an aside, rumor is, most teams are moving to 140mm front rotors because they are less prone to warping and making noise. There are 8-10 WT or Conti teams running 140mm rotors front and back. I have always run that setup becuase that was what I ran on my cyclocross race bikes.

[Lewn777]

Partially retracted pistons, meaning the pads are lightly rubbing on the disks would be my bet as where the noise is from.

-One reason is dirty pistons. Some dirt or grime can get on the pistons so they then are slow to retract back into their bores, often one side is retracting properly but the other side is retarded.. Cleaning with warm water and a q tip or lubing the pistons with silicon grease or mineral oil could help. Avoid any substance that could damage the seals.

- Another reason could be poor setup such as poorly faced fork surfaces, or try to setup the brakes properly with a feeler gauge to make sure that is not the suspect.

-Another less likely reason that could also make sense that the heat in the brake system causes some expansion of fluids. Air and water will expand far more than mineral oil so a really careful re-bleed might help. Even a hot ambient air temperature could maybe effect where the pistons are sitting in their bores, maybe a long shot but re-bleeds on Shimano are pretty straightforward, so worth a shot.

-If still no dice then I would switch out the rotor for a nicer, more finely machined floating type two part rotor. I always preferred SRAM rotors on Shimano systems over the stock Shimano rotors.

All my knowledge on disk brake systems is from 15 years working on MTBs, and in my view the current crop of disk brakes are not fit for purpose on road bikes (my opinion is similar to that expressed by Chris Froome a few months ago). In an ideal world switch the bike to a direct mount brake or well set-up rim brake.

[tommyboyo]

So no definitive answer at all then unfortunately.

I do buy into the rotor warp more than anything else though.

System fluid and pad retraction issues seems less likely to me.

I have certainly noticed more 140mm front rotors in the 'lower level' pros recently which is v.interesting. I only ever have the issue with the 160mm at the front.

If it was fluid expansion related, then why not both ends?

[tommyboyo]

As an aside, rumor is, most teams are moving to 140mm front rotors because they are less prone to warping and making noise. There are 8-10 WT or Conti teams running 140mm rotors front and back. I have always run that setup becuase that was what I ran on my cyclocross race bikes.

Do you believe a 140mm front is fine for a 75-80kg rider who does sharp up and downs on the road, but no long desents with repeated braking (South Downs in England)?

[Lewn777]

So no definitive answer at all then unfortunately.

I do buy into the rotor warp more than anything else though.

System fluid and pad retraction issues seems less likely to me.

I have certainly noticed more 140mm front rotors in the 'lower level' pros recently which is v.interesting. I only ever have the issue with the 160mm at the front.

If it was fluid expansion related, then why not both ends?

Odd, in my view pad retraction seems most likely, but a re-bleed and a proper set-up with a feeler gauge are must tries.
Rotor warp means that the rotor would be out of true, therefore you do not get a consistent noise, more like a burr-burr.
For the average rider 160mm front is an ideal size rotor to run, I wouldn't recommend 140mm to anyone over 75kg. If there is an issue with 160mm rotors it is a manufacturing/design flaw so simply swapping out the rotor for another brand would be the likely fix. Nothing wrong with 160mm in essence.

Fluid expansion only effects the piston end in a sealed system. Making sure there is no trapped air or moisture in the system is a must try, no mechanic would dismiss it as a possibility.

[Lewn777]

As an aside, rumor is, most teams are moving to 140mm front rotors because they are less prone to warping and making noise. There are 8-10 WT or Conti teams running 140mm rotors front and back. I have always run that setup becuase that was what I ran on my cyclocross race bikes.

Do you believe a 140mm front is fine for a 75-80kg rider who does sharp up and downs on the road, but no long desents with repeated braking (South Downs in England)?

South Downs I know quite well, I would say for that size person 160mm to 180mm would be an ideal rotor size. 140mm in my view is too small. 140mm would be for lighter riders where every gram is being counted.

[kode54]

Assuming everything is set up correctly, and the disc isn't warped at all, I've found it's normally just the pistons being slow to retract. Ironically on rougher roads the bouncing of the front wheel seems to help them on their journey back into the caliper.
It's a good idea to 'exercise' the pistons every few months (ymmv). Plenty tutorials online, Park Tool do a very good one - it's shown on an mtb but the procedure is exactly the same. It helps to have an assistant pump the brake whilst you hold in one piston and exercise the other -
https://youtu.be/vQXFFgRButo

Once in awhile, after cleaning out the calipers, I use a Q-tip and wipe mineral oil around the piston before retracting (exercising) it.

[kode54]

-If still no dice then I would switch out the rotor for a nicer, more finely machined floating type two part rotor. I always preferred SRAM rotors on Shimano systems over the stock Shimano rotors.

I use SRAM Centerline X rotors and have not had any issues. Only after a misty, wet ride where I pick up contaniments/oil off the road. I then scrub/sand down the pads, clean the rotors with isopropyl alcohol and i'm good to go.

[Lewn777]

Assuming everything is set up correctly, and the disc isn't warped at all, I've found it's normally just the pistons being slow to retract. Ironically on rougher roads the bouncing of the front wheel seems to help them on their journey back into the caliper.
It's a good idea to 'exercise' the pistons every few months (ymmv). Plenty tutorials online, Park Tool do a very good one - it's shown on an mtb but the procedure is exactly the same. It helps to have an assistant pump the brake whilst you hold in one piston and exercise the other -
https://youtu.be/vQXFFgRButo

Once in awhile, after cleaning out the calipers, I use a Q-tip and wipe mineral oil around the piston before retracting (exercising) it.

Yep, I do the same and push the pistons into their bores with a plastic tire lever.

[tommyboyo]

Maybe I have a faulty caliper up front.

I have a new build in progress with Ultegra rotors and calipers, with the same specs in terms of size, so will be interesting to see if they make the same ticking for a short time after heavy braking.

Also have some mt900 rotors that I got last year to replace the DA ones with in due course.

So I can see if one thing in particular makes a big difference.

Apart from that annoying sound, the setup has been pretty flawless in terms of performance. I do sometimes long for my SL5 rim though, as in dry weather, there was not that much loss in braking performance and it was a beauty!!

[QuackMD]

Would like to add that sometimes one pistons sticks for no reason at all, even if completly cleaned and lubed. Most likely has something to do with the manufacturing tolerances of the seal and/or caliper body.

[rollinslow]

Honestly, you just have to try various things to dial in what works for your bike. My setup is as good as it will get. 160mm DA rotors front and back, bedded perfectly, never seen a drop of grease or water. Perfectly quiet on normal roads and decents that don't even require disc brakes. On a recent 20% grade descent I could not enjoy it because of the screaming brakes when they got hot and heat related warping for a period after (pistons exercised, mineral oiled, ive done it all consistently).

It sure is embarrassing to have a 17k USD making more noise than your hand me down commuter bike. No way in hell am I ever getting disc on future road bikes. My gravel bike has them for necessity and Mosaic is a top of the line builder but if anything, this confirmed that I am beyond anti disc for a road only bike. Extra weight, extra cost, extra noise, extra maintenance, extra time commitment, zero benefit.

[alcatraz]

Lightweight + heat is my guess. It's going to warp a bit more.

5-15 seconds sounds heat related.