We talk to Michael Hall from Zipp USA

Recently Zipp Australia had Michael Hall, their Advanced Development Engineer from the US out here to talk about their products. We managed to score an invite and a few minutes to talk to Michael.

Catching up with Michael is again another one of the wonderful examples of the enthusisatic, engaging people we have in and around our sport. With his wealth of knowledge and drive for innovation Michael is the type of guy you could listen to for hours, and if allowed to indulge his fondnesss for Aussie coffee I dare say he could continue well into the night.  


We started by talking about the development of the Firestrike and the width of tyres.

Michael: The Firestrike rim is a little wider at the brake track, it helps smooth the air transition from the tyre. Since the time of the original firecrest release till now it seems like tyre sizes just keep getting bigger. When we launched the Firecrest 21’s were still very common and with 23’s it was probably 50/50. Now it’s 23’s, 25’s and some people are even experimenting with 28’s its going insane.

Transitions: Yeah I don’t know what the tipping point was, whether it was the pro peloton taking wider tyres on board. But a typical argument between triathletes was over the merits of 19 v’s 21 mm tyres now that has all changed.


Michael: Honestly when I started at Zipp 10 years ago 19’s were common, now I don’t think anyone would dare. So in ten years the market has totally changed. And now people want to do lot more with their wheels. In the US we have a big gravel scene brewing and Fondo’s so people want to buy a set of wheels that they can put 23’s on for road riding then put some 30’s on and do a gravel race, it’s really interesting to see where things are going.

Transitions: With triathletes it used to be that you had your “good race wheels” that were usually tubbys that meant they weren’t practical for everyday riding, so your race wheels were hung up after race day till their next outing whereas now with the advent of race clinchers folks can buy their race wheels and get plenty of miles out of them and really get their money’s worth.

Michael: Yeah they are super robust, as light as they are they are built like tanks. Even we are surprised how well they have done in the field. We always expect some failures, I mean people hit potholes and that sort of thing but that rim has been really robust for us, with very few failures.

Transitions: Is the brake track new on the Firestrike?

Michael: With the Firestrike we developed a new process. We also went back to our suppliers and said “Here is what we want to do” we have also been working with Swisstop and developed some new brake pads. We also developed these little brake sipes that helps to get the water away but the problem with that is that we don’t want it to wear away. So we went back to our suppliers and said “How can we improve the durability of the brake track?” They came up with adding silicon carbide into the resin system. So we developed a process with them to get the silicon carbide into the resin system and then we had to develop a process to mould with it because it is very finicky. So there is quite a bit of difference in the brake track, although from a distance it looks like an older Zipp with the sandblasted brake surface there is quite a lot of technology baked into that brake surface.


Transitions: The dimples of the new Firestrike have been refined, what does that entail and what are the gains?

Michael: When you are looking at dimples its just 1 or 2 watts here or there, the rim shape is the real driving factor the dimples are just about keeping the air attached a little longer. With this dimple pattern versus the original dimple pattern, starting with the Firecrest and the toroidal shape when dimples started it was all about keeping the air attached and then we started learning more about wheel aerodynamics and what was really going on with the increase of CFD we started looking at what are the big key factors and we started looking at shedding frequency. So now we are tailoring the dimple pattern to induce a shedding frequency that is higher than what would be is natural frequency. So it’s just a few watts here and there.

Transitions: So does testing also evolve as the technology improves?

Michael: Yeah, every year we continue to get smarter, computers are getting better, wind tunnels are getting better and track testing is getting better. We look at testing as needing all three facets. You need to be able to simulate because you can see things in CFD that you can’t see in the wind tunnel. The wind tunnel is very good for covering a lot of ground quickly. I really like the wind tunnel. One of the tenants is, for CFD companies they tell you that you should do more CFD because you can optimise…Blah, Blah, Blah,,,, what they don’t tell you is the fact that when you do a simulation and you are trying to solve a problem with super-fast computers it may take 8 hours to solve one data point. Whereas in the tunnel, I actually did the math on our last tunnel test, we can leave the tunnel after 3 days with roughly 900 data points. So comparing 8 hours in CFD per data point to 3 days for 900 data points in terms of getting a massive amount of data in a hurry wind tunnels are still King.

The other hidden secret about CFD is that a lot of times you have to dumb it down to get it to solve. People start doing things like removing cables and all the stuff that is really hard to model, and that makes the model a little more unstable, but that is “real life”. So in the tunnel we show up, you put your rider on the bike, you have all the cables and everything. The tunnel doesn’t care, it blows air and you get a measurement.

Where you need the CFD is to bounce this information back and forth you take the CFD and you model it to match what you see in the tunnel and then you take the two and it tells you what is going on, the tunnel gives you a good measurement and then we go to the track. We need to find if that is real life, we go to the track or on the road with a rider on it and once we get all three to match we know we are really onto something.

I look at testing like a three legged stool, you have to do all three. So the guys who just do CFD or just do wind tunnel I think they will be missing a lot of things.

Transitions:  Do you find the buying public take to the research well or ca they be sceptical, and do you need to go the extra yard to convince them?

Michael: Yes it can be hard to convince people, because you can’t see air. It’s hard to convince the public that one is faster than the other, so what we have to do is keep trying to educate people and tell them “this is why we do these things and this is what we see”. It’s a lot harder to do than weight or stiffness, those things are really super easy to measure, you can weigh a bike or weigh a rim or put it on a jig and test the stiffness. Aero performance is a little more difficult but what we have shown over the years is that it really is real life and is something that you need to pay attention to. The faster you go, the more adverse the conditions the greater the crosswinds the more attention you need to pay to the data because you can have unexpected characteristics from different products.
Do you think there should be as industry standard for testing as the public becomes little jaded by testing reports where, especially with things like bike frames, there appears to be a handful of “fastest bikes in the world”?
Yeah, I can take a set of tyres with the right tyre pressure and with a bit of work you can make anything look good. But Zipp has a history of making product that are fast, when the Firecrest launched you saw basically the whole industry almost overnight change from doing sharp v section rims to converting over to what Zipp was doing. To me that is an indication that while it may be easy to fake wind tunnel numbers, what Zipp are doing is really changing the way that people look at rim aerodynamics and bike aerodynamics. We have some cool stuff in the works that we think is going to flip the world upside down soon.

Transitions: So what rim width are Zipp running now.

Michael: This one is just under 28mm at the brake track and that’s about at the limit we can go to with rim brake technology. There is only so far that you can open up callipers and get around frame design tolerances. Disc brakes are going to change a lot of things, Im not sure how its going to work yet in the pro peloton with neutral support and the like. I think the industry is heading that way whether the pro peloton goes that way or not. What e are haring from a lot of the frame manufacturers is that sis where they are putting all their efforts.

Transitions: Do disc brake wheels pose any new issues for you?

Michael: There are always going to be “issues”. It kind of starts the race all over again. We are now starting to design rims, especially carbon clinchers for different reasons. Now we don’t have to worry about braking we can as ourselves, “What would our resin system look like if we didn’t have to worry about braking?” and that’s where we are looking next. We can start to look at tougher resins and then once we go to a tougher resin system we can start looking at how much weight can we take out of the product and that’s where it will start to get super interesting. If you get a tougher resin system then you can make a very similar rim that performs the same just at a lighter weight and I think that s going to start a new race that is going to be really cool.

Transitions: What about disc wheels, is there anything new coming out on that front?

Michael: We have got several projects in the works actually. Discs are not going away, that is where Zipp started and we are certainly not going to abandon them that’s for sure.

Transitions: They do get a bit impractical now with really well performing deep rims, but many still want a disc for their A race.

Michael: When it comes down to pure aerodynamic speed you can’t beat a disc wheel and you can’t beat the sound of them. And that’s what we like about the Firestrike rim too, there are rea advantages to the Firestrike braking both in the wet and the dry but when you brake on it, it just sounds awesome, it’s just got a unique sound that is super awesome.

Thanks to Michael for his time and Zipp Australia (Echelon Sports) for the invitation.  


Michael Hall: Transitions
Zipp tech images: Source Zipp.com with permission. 

©Transitions 2015