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Tech & Wearables

Technical FAQ: Tour de France tires, flattop chains in mud, and rim surface wear

Our technical expert answers questions about pro teams tracking flats and muddy, icey SRAM chains woes.

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

Dear Lennard,
While watching the Tour I began to wonder what the teams’ mechanics do with the punctured tires in terms of tracking any data. Do mechanics keep track of the types of punctures, frequency, surface, etc. and share with the manufacturers? Is tread wear measured, recorded, and shared? With more teams using clinchers and rumors of one team using a foam core I would guess that manufacturers use the Tour as a test lab so if that’s the case, how do they gather their info? I think it would be fascinating to hear from the mechanics just how deep into the weeds they go, or maybe they just toss ‘em?
— Peter

Dear Peter,
Some teams track that, and some teams do not. The two replies here cover that wide gamut.
The first is a reply from Nick Legan, who used to be a WorldTour mechanic for various WorldTour teams, notably including Radio Shack at the Tour de France during Lance Armstrong’s brief comeback.

“When I was a mechanic, we weren’t gathering data on tire lifespan. [We were] too busy managing each day. We certainly tried to replace tires before a puncture was inevitable, but roads happen.

This may have changed since then, but pro team wrenching is very pragmatic. Unless we saw a lot of punctures with a given tire in a set of circumstances, we would simply replace the tire and move on.”

— Nick Legan, road brand manager, Shimano North America bike

Challenge Tires has a different perspective. “We have not been able to buy our way on to a WorldTour team but our perennial French Tour team has given us insights.

Most teams, even at the top level, do as Nick says, watch for nicks and cuts and unusual wear, replace as needed and move on. Sometimes we can get them to keep a pile of used tires to study, but keeping the trucks clean takes priority. We pushed our teams to give us back more, but it was a tough balancing act because, of course, you get what you pay for.

However, we did find out through some extraordinary circumstances that a couple of teams (well-funded, well-managed) do invest in the details. The year the Tour started on the wet and slippery roads in the UK, and then went directly to the wet and slippery cobbles of northern France, our Bretagne/Fortuneo (now Arkéa – Samsic) team got in multiple breakaways and stayed until being caught. On the second rest day, both the Sky (Ineos Grenadiers) and Trek teams came by to ask them why their riders had so few flats and crashes on the wet surfaces vs. all the other teams.

This news was relayed back to us after the mechanics gave us credit. This led to a couple of interesting meetings with those teams (that unfortunately did not exactly lead to the hoped-for conclusion) we did learn that both teams had their mechanics who were riding in the cars tracking every crash and flat in the front group by a team.

They assumed that these results would highlight improved performance as riders were all pushing the edge and the tires would perform or not so they could learn something. I also think it was also a good way to keep the mechanics awake.

This led to a major European tire brand coming to us to make their cobbled classics tires that combined our special seamless latex inner tubes and more supple casings topped by their special tread rubber.

I have similar stories when we worked with Liberty Seguros team manager Manolo Saiz and chief mechanic Faustino Muñoz and Johan Bruyneel at US Postal. The top teams pay to really track the details.”

—Morgan Nicol, Challenge Handmade Tires

Dear Lennard,
Are you hearing about any unintended consequences of the narrow SRAM AXS Flattop 12-speed chain design, particularly with debris contamination?

My kids and I had all of our chains drop during last year’s muddy Colorado State Cyclocross Championships. The chain was visibly contaminated with mud/debris and you could easily see the lack of seating/engagement with the front chainring – as a result, the chain was sitting high on the chainring — not fully seated — and would drop at this site immediately and repeatedly after putting it back on. The only fix was power washing and cleaning the chain, which would then work fine until contaminated again, usually after 1 lap of the course. My spare bike was identical but with an 11-speed SRAM group had no problems and I was able to pre-ride and race multiple laps without a mechanical.

Since then we’ve continued to use the exact same 12-speed bikes and the issue has not recurred; we did not see similar conditions though. I’ve been a lifelong bike mechanic and have been racing cyclocross for 15 years and have not seen this occur in similar conditions with 10- and 11-speed setups and I don’t believe the conditions were unusual that day. I suppose I could pit every half-lap like the pros, but this really isn’t practical, and, again, there were no problems with my spare 11-speed bike. I also suppose I could use a “mullet” setup and use the wider Eagle 12-speed chain, but this introduces a host of incompatibility issues with cassettes — again due to the Flattop chain design. And, after all, the AXS group with the Flattop 12-speed chain is marketed for cyclocross, so looking for a solution in muddy conditions seems odd.

So, this leads back to my question, is the Flattop 12-speed chain too narrow and is the above an unintended consequence of the design? It also makes me wonder why the Flattop design was created in the first place, especially if the Eagle 12-speed group works so well? Am I missing something?
— Steve

Photo: Rob Arnold

Dear Steve,
I wasn’t there this past year for Colorado state championships November 23-24. If your kids were in the junior categories, I’m guessing you all were racing on Saturday the 23rd, you in the early morning, and them in the late afternoon. At that time of year and time of day, perhaps it was below freezing, and if it was muddy, then perhaps what you were experiencing was ice (muddy ice with accompanying plant matter frozen in) in the chains.

A few years ago, my daughter had the same experience of constant chain derailment in Colorado state cyclocross championships. Thing is, she was racing on SRAM Force 1X11 with a SRAM 11-speed chain, not 1X12 with a 12-speed Flattop chain. It, too, was new to me, and I pulled the bad dad move of suggesting that each time it derailed, she kept putting the chain back on with the narrow chain gaps onto the fat teeth of the fat-thin-fat-tooth X-Sync chainring. She insisted that she knows better than that and had taken great care to align the outer links over the fat teeth and the inner links over the thin teeth.

Other riders on 1X setups with standard chainrings with chain guards, rather than X-Sync or equivalent drop-stop wide/narrow chainrings, were not having this problem. Then it became clear that the problem was the tall, square profile of her X-Sync teeth that were designed to completely fill the space in the link, whether it was a fat tooth in an outer link or a thin tooth in an inner link. When ice filled the space between chain link plates, the chain would ride up on the top of the tooth. On the other hand, the shorter, thinner, chisel-top teeth of standard chainrings would push enough ice out of the way that the chain would stay in place.

My solution at the time was to install an MRP chain guide so close over the top of her chainring that the chain could not ride up. I also suspect that the sharper tooth shape of the newer SRAM X-Sync 2 chainrings, which are designed to reduce “the accumulation of mud, grit and grime” would have created fewer problems under those conditions.

I have answered similar questions about this in the past, long before the advent of SRAM 12-speed, so I’m wondering if it is the Flattop chain or the chainring tooth shape that was causing your problems.

(I sent this answer directly to Steve and got the below response.)
― Lennard

Dear Lennard,
Thank you for the response; this makes sense to me after looking at the chainring tooth profiles you sent – I hadn’t scrutinized them closely before. One thing I didn’t mention is we were using an all-SRAM-road-AXS 12-speed group with the exception of the chainring, which was a Flattop-chain-compatible ring by Wolf Tooth, since I could not get a SRAM crankset in the shorter crankarm lengths needed for my kids in order to use their proprietary chainring. Thus, the only chainring option was Wolf Tooth, which I’ve used for years without a problem, so I didn’t think twice. But, after looking at the tooth profiles you sent, I bet the relatively square tooth profile of the Wolf Tooth chainring is the problem when combined with the narrower Flattop chain (in other words, the Wolf Tooth design doesn’t seem to be a problem with the slightly wider 11-speed chain, and this has been my experience). Interestingly, I contacted Wolf Tooth after the Colorado State Championships last year and asked them if it could be their tooth design, and they essentially said it was probably the chain: a narrower chain — like the Flattop chain — is more likely to collect mud and will have a greater chance of packing with mud.

So… the prompt for my email to you was in preparation for the upcoming CX season; I was trying to see if I needed to switch to a mullet setup with an Eagle RD and Eagle chain for my kids, but after your response, I may just try to get them on SRAM cranks to use their X-Sync 2 ring with the sharper teeth rather than rebuild everything.

PS – regarding the conditions, it was snowy and icy for me in the morning, but I ended up racing my 11-speed setup, and I had no problems. My kids rode in the afternoon, when it was warm, and everything melted, resulting in a very muddy course with lots of mud accumulation on the bikes. They dropped chains in the pre-ride, and my son had a DNF due to his chain dropping in his race. Thankfully, the chains held for my girls a little later in the day (maybe the course dried just a bit compared to my son), and they ended up placing 1-2 in the 9-10 junior race, so it wasn’t all bad.
— Steve

Photo: Dan Cavallari |

Dear Lennard,
Thanks for the follow-up! I just tried your suggestion to measure rim braking surface wear, and it works really well. Using a steel 6” ruler as a straight edge, I’m able to see the concavity of the rim, but it is nowhere near 1 mm deep. I used a normal-sized paper clip and it would not go through, and I checked the width of the paperclip on the ruler. It is indeed not greater than 1mm.

I found that the front is slightly more worn than the rear. And on the rear, one side is slightly more worn than the other. This is a great method to measure wear, as it does not require any special tools and is quite accurate. I think Park Tool could even develop a measurement tool based on this principle, just as they have a chain measurement tool with calibrations to measure a gap.

Dear Marc,
Great idea! I hope Park Tool or another toolmaker reads your note.
― Lennard

Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder ( and purveyor of non-custom huge bikes (, 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.