Gear

Technical FAQ: Ceramic Speed with DUB, disc brake pad delamination

VeloNews tech expert Lennard Zinn offers insight into SRAM chainrings with a CeramicSpeed bottom bracket, and disc brake pad surface issues.

Have a question for Lennard? Please email him at veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
I too had similar problem as Steve with my SRAM AXS Red on cyclocross bike in muddy conditions. I experienced the problem at last year’s nationals in Tacoma, WA, where there was no snow or freezing temps. The chain initially started skipping on the rear cassette, but ultimately wouldn’t hold the front chainring, and I lost over three minutes on one lap trying to get back to the pits. I changed bikes to my 11-speed SRAM Red and rode the remaining laps problem-free. Also, I, too, am using a Wolf Tooth chainring with Easton crank since my new Crux still uses PF30 Ceramic Speed BB.

Any ideas on how to keep Ceramic Speed PF30 bearings but use SRAM Red DUB crank?
— Matt

Hi Matt,
Here is the answer from Ceramic Speed:

“Unfortunately, due to the bearing spacing requirements for DUB, there is not a straightforward solution to running a DUB crank with Matt’s existing bearing setup. While we have the dust covers to accommodate the DUB spindle interface, it is a width/spacing issue that is more difficult to solve. Matt needs a set of cups designed for his frame (either PF30 if a 2013 model, or BB30 for newer Crux models) that places the pair of 61806 CeramicSpeed bearings (what is supplied to Specialized on numerous S-Works models) in the correct width.


We measure all BB cup bores and pair them with appropriately built bearings (considering radial clearance and cup interference), and so do not ship only cups. A third party set of cups would be the next best solution, however fitment (possible binding) and/or noise (possible movement) may present issues over time.
—Paul Sollenberger, Ceramic Speed Senior Technical & Sales Education Specialist.”

― Lennard

Dear Lennard,
I’m writing about a disturbing mechanical incident that happened to me yesterday. I was riding in Marin County, descending Muir Woods Road. It is a fairly steep descent, but not very long. I was using the front brake periodically during the descent to control my speed. Just before reaching the entrance to Muir Woods National Monument, I heard a loud noise from my front brake caliper. Shortly thereafter, I realized that my front brake had no stopping power. Based on a quick look, I concluded that a field-fix was unlikely. So, I road home carefully, controlling my descents, as I was reliant on my rear brake.

A few details about the bike I was riding. It’s a Lemond Poprad Disc with TRP HY/RD calipers. The brake pads are Shimano BO1S resin pads. I’ve been using this type for several years, changing them regularly. The pair in question were installed about five months ago and had ~900 miles on them. Included are two photos, the first showing both pads, one of which is missing the friction material; the second photo shows the remaining pad thickness of the intact pad.

It never occurred to me that a brake pad might delaminate. How common an occurrence is this? Is this due to a manufacturing defect or operator error?
—Keith

Photo: Keith Grundy

Dear Keith,
Given that I have never heard of this before, I believe it is very rare. (If this has happened to anybody else out there, please let me know). I have never even considered this as a potential risk before reading your letter. I still think it is “inconceivable, as Vizzini said so eloquently in The Princess Bride, that it would happen to me, you, or anybody else on any given day. I suggest you chalk this up to your version of getting hit by lightning on a clear day. I don’t know how the friction material is bonded to the backing plate. It has been done for so long on cars, motorcycles, and bicycles that I think they generally have it down quite well.

One thing suggested in the Shimano response below does have me wondering about how user error could have come in. As many people riding with disc brakes know, when installing the wheel, sometimes the rotor does not go right up into the slot between pads. If the rotor does not slide right in, it might be because it hits the outside of the caliper or the mounting adaptor. However, it might instead hit the edge of the pad friction material, and if the rider tries to force it in, it could create an unanticipated sideways stress on the pad material relative to the backing plate, something that lab tests may not be designed to simulate. And, when the friction material is minimally worn, as your good pad seems to be, it will be easier to hit the edge of that friction material when installing the wheel.

As for using Shimano pads (those appear to be standard Deore resin pads) with TRP brakes, while unorthodox, it should not have been a contributing factor in the friction material peeling off of the backing plate.

I checked with both Shimano and TRP and received the following answers.
― Lennard

Photo: Keith Grundy

From Shimano:
Those are definitely our resin pads. My guess would be that his mechanic installed it (them) when the bike was serviced. I have no idea on compatibility w/TRP.Pad delamination like this is incredibly rare, though. I’m not sure if hitting the pad with the rotor during wheel mount could have compromised it.
—Koichi Tanaka, QC manager Shimano North America Bicycle, Inc.


From TRP:
Wow, I’m glad to know Keith made it home without injury.
I don’t believe I’ve ever seen pad material completely separated from the backing plate in this way. I’d like to check with members of my customer service staff tomorrow to see if they’ve ever seen anything like this with our pads.
It might be nice to see a few more photos, especially of the backside of the good pad. From the photo it appears the “good” intact pad is hardly used while the “bad” pad shows signs of high heat on the backside where the piston has burned or rubbed off the paint in a circular pattern through contact with the caliper piston. Although, this could have been from the heat generated by the metal on metal braking while getting home.
With regard to your second question, TRP road brake pads are interchangeable size-wise with certain Shimano pads and there are many options in the market which will fit in the caliper.

We always recommend in the interest of safety, staying within the manufacturer’s designed, tested and approved combinations, in this case TRP pads with TRP rotors. We do know however that there is some discussion among riders out there about personal preference with various combinations, but this is a use at your own risk situation.
If I’m not mistaken, I believe Shimano also has a list of recommended guidelines for their resin pads with specific rotors.
—Lance Larrabee, managing director, TRP USA


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn on Twitter.