Zipp 404 Carbon Clincher Brake Pad Considerations

After writing my Zipp 404 Carbon Clincher review I got quite a few e-mails and phone calls about a statement made in favor of the Yellow Swiss Stop over the new Zipp cork brake pads.

I had written that the Swiss stops felt better than the Zipp's. After some additional testing I am going to stand by what I said about feel but add something new about safety. If you are riding any brand of carbon clinchers safety should be more of a concern than feel. One of the test engineers at Zipp "Jason Fowler" took the time to educate me on carbon rim braking and how Zipp had tested and developed the carbon pad they are recommending for the 404.

Bottom line - The Zipp cork brake pads might not feel as good as the Yellow Swiss Stops but they generate less heat and are a safer product.

Here is what Jason said "As with many questions of this nature, there’s really no absolutes in evaluating pads. As you know a lot of it comes down to personal preference in terms of modulation vs. grab, rider style and ability, terrain, etc. That said, I’ll try to answer these questions as best as possible; please let me know if anything requires clarification or some additional data.

I believe we were actually the first company to come out with pads specifically engineered for use with carbon fiber rims. Our recommendations for our carbon fiber wheels are either our Tangente pad or the carbon/carbon pad. Both were developed specifically around maximizing dissipation of heat in the brake pad/rim systems but with slightly different performance characteristics in mind otherwise. The older carbon/carbon pad is actually very slightly better than the Tangente at dissipating heat, due to the fact that it is constructed using a matrix of rubber and pitch fibers having extremely high thermal conductivity. Those fibers are actually remnants from the process of manufacturing the brake rotors used in F1 cars and are a by-product of our years working in and with the racing industries. The carbon/carbon pad wears more rapidly relative to some other pads on the market (including our Tangente pad) but this is also by design; the intent of this pad is to shed pad material when it reaches elevated temperatures rather than melting to the surface of the rim. While this results in the need for pad replacement more often, it greatly reduces the wear on the rim associated with initial heat dissipation and avoids exacerbating the problem, which is what occurs when pad material melts onto the surface of the rim. Not only can it lead to uneven braking performance due to variation in the effective width of the brake track brought on by the rubber deposits, but the deposited rubber further insulates the rim and contributes to increased build-up of heat. The Tangente pad offers a significant improvement in wear relative to the carbon/carbon pad with nearly identical thermal performance characteristics. It offers a bit more modulation although it does suffer a bit in wet performance. Obviously, the Tangente pad is not suitable for use with aluminum wheels as it is a cork composite. For riders in hilly to mountainous regions, the carbon/carbon pad can be an excellent choice for an aluminum clincher, as it can mitigate heat build-up with a rider that is a bit unsure of their descending ability and thus rides the brake pads. While aluminum conducts heat quite well relative to a carbon fiber rim, it is still possible to induce tube failure due to heat.

The SwissStop yellow is obviously a very popular pad and for good reason. I feel it warrants a special mention due to some of the issues we have seen with its use with both carbon clinchers and tubulars. The pad offers excellent braking power but is prone to melting to the surface of the rim under prolonged application. We have seen that it is possible in this situation to damage the rim as a result of the elevated temperatures achieved due to the presence of the deposited insulating layer of rubber. That said, this is extremely dependent on the user. The power afforded by this pad is sufficient that such prolonged application of the brakes would be highly unlikely to be necessary in the field, but in the case of a large rider applying the brakes continuously on a significant grade, it is conceivable that such damage could occur. This is not unique to the SwissStop pad but I wanted to mention it in particular due to its popularity.

In terms of concrete numbers, we’ve developed a series of internal tests as we felt the existing EN norm was not sufficiently rigorous because certain rims known to have field failures were not failing in a lab setting. Some tests were developed specifically to replicate a larger rider descending a 20% grade while others were designed simply to impart a significant amount of braking energy to the wheel until a failure results. This testing has consistently shown that each of our pads generate at least one-third less heat at the braking surface of the rim relative to some of the more popular pads on the market. A small reduction in rim temperature can be very significant when you are operating at elevated rim temperatures as even a small reduction in temperature can mean the difference between operating below or above the glass transition temperature of the resin system employed in the rim; however, in this case we are seeing deltas of up to 200°F. There are pads on the market that will provide more stopping power at a given lever force but this comes at the expense of feel and added heat build-up. We feel that between the two pads we offer we have struck a good balance of pad durability, stopping power, feel, resistance to fade, and most importantly, thermal management for the rim itself. Just as a reference, I’ve attached an image from our infrared camera that we use for tracking temperatures throughout the rim in our testing. The wheel and rim are somewhat obstructed by the infrared thermocouples attached to the machine that are used to evaluate a specific area of the rim and the contact thermocouples used to record brake pad temperatures. Unfortunately, the resolution of our $20k camera is not so good as you have to get to around $50k before you get decent image resolution."

This is the image Jason provided. I am not saying it's concrete evidence the Zipp pads generate less heat because I do not have 50K to buy the camera and do a comparative test but I can say I always feel confident with Zipp R&D. Zipp have done their homework on the subject and I will be cribbing from them just to be safe.

All the available Zipp pads listed below: Since this article was written Zipp have released the new Platinum pad. Not yet tested but they promise to be another step in the right direction from the guys at Zipp who take cabron braking and pads very seriously.

Zipp Tangente Platinum Pro Brake Pads $39.90		Zipp Tangente Cork Brake Pads $69.90		Zipp Carbon Brake Pads $24.90