Mondays are rarely as thrilling as yesterday's stage 10 of the Tour de France which provided fireworks, drama and intrigue as race favourite Alberto Contador was forced to abandon after suffering a broken leg in a crash on the 163km stage. But if you were on Twitter, that wasn't the really big story, all attention was focused on the cause of a photo of Contador's broken Specialized Tarmac frame. Did the frame snapping cause him to crash, seemed to be the general question that most wanted an immediate answer to.

New photo just dropped in from AFP of broken bike which is definitely Alberto Contador's - see mounted race No 31. pic.twitter.com/1xyy1ww0Ay — John MacLeary (@JohnMacLeary) July 14, 2014

Unfortunately there were no TV cameras near Contador, instead the first TV viewers knew of the incident was when the director cut to a bloodied Contador standing at the edge of a road, photographers swarming around him and the race medic applying a bandage to a badly cut right knee. There was a bike in the ditch, but it appeared to be Nicolas Roche's McLaren S-Works team bike, and Contador limped on for another 18km on another spare bike.

In the absence of of any evidence of what caused his crash, and the emergence of a photo of what appears to be his team bike snapped clean in two, speculation ran like wildfire through the social media network. We immediately contacted Specialized who have issued this response:

“Alberto crashed on a fast and straight part of the descent. He was reaching for his pocket and the bike was swept away under him probably because of a bump or hole in the road. Alberto was in the shape of his life and the entire team had our eyes fixed on the podium in Paris and the work we would have to do to get there”. -Bjarne Riis, Director Sportif, Tinkoff-Saxo "Teammates were first to communicate the crash to the team car via race radio. Reports from Tinkoff-Saxo are saying their team car was passing closely to a Team Belkin vehicle and bikes on the roof racks became entangled between the two cars causing Alberto’s spare bike to be broken into two pieces. When a racer has a heavy crash, a mechanic will immediately provide a spare bike as a safety and performance precaution. "As Alberto’s spare bike was destroyed, Nicolas Roche immediately offered his own race bike so that Alberto could continue the race. With the arrival of the second team car, Alberto was provided his own, secondary spare bike. Unfortunately after riding approximately 18km with what is now known to be a broken tibia, Alberto Contador was forced to abandon the 2014 edition of the Tour de France."

As we pointed out in our report last night though - the bike in the pictures clearly has Contador's race number on it - not Roche's and unless Roche was on a spare bike he is riding a McLaren Tarmac which has a completely different paint job.

But maybe Roche can is the best person to tell us what happened - at least in that initial crash. In his Independent blog posted early this morning he sheds some light on what actually happened.

"As I helped Alberto up, I noticed his bike was broken [we assume he means crash-damaged - ed] and there was a stream of blood coming from a gash just under his right knee. His wound looked pretty bad but as a rider, my natural instinct was to simply hand him my bike and encourage him to keep going. "Take my bike Alberto! Go, go, go!" "Nico, I don't know if I can," he said as he hobbled out onto the road. "Go and see. Try it, just jump on the bike!" "As Alberto took off gingerly on my bike, I waited at the side of the road watching what seemed like everybody in the race pass me by. There were cars and groups of dropped riders everywhere, so I held Alberto's broken bike in one hand and waved the other one frantically in the air, afraid the team car would drive past in the chaos."

It seems then that Roche was there when Alberto crashed, stopped and like the dutiful domestique he is, gave the Spaniard his own bike and then stood at the side of the road with Alberto's crash-damaged bike waiting for the Saxo-Tinkoff team car. The bike Roche was holding at that point was intact, as the live footage from the race shows quite clearly. It's a bit less clear in this still, but obvious from the feed.

When the team car stopped to give Roche a spare bike, Contador's crash-damaged bike was put on the top of the car and a short while later, maybe as one team car was trying to overtake the other, Contador's other spare bike on top of the car (Contador has a spare bike on each team car, three in total) got tangled up with the Bianchi atop the Belkin team car, causing the frame to snap.

This is the frame Contador crashed on and shoe courtesy of C Desimpelaere Tinkoff Head Mech #framegate pic.twitter.com/KfOHtoTNOH — Richard Gorman (@richardgorman) July 14, 2014

Above is what appears to be a photo of the bike Contador actually crashed on, the bar tape is covered in mud, and it's clearly not broken. The brake lever hoods are both bent around, as you'd expect in such a high speed crash. There's also no front wheel here, that presumably might have been damaged too. No, Contador came out of the crash worse, his jersey covered in mud and a broken leg. So what of the broken frame photo that did the rounds on Twitter?

The photo above does actually show a Saxo-Tinkoff mechanic untangling a Specialized team bike from a Bianchi atop the Belkin team car, backing up the claim by Specialized that this was the cause of the broken frame. It had nothing to do with Contador's crash, it was a separate incident, but because events unfolded so quickly and dramatically in the race, many were led into making their own, inaccurate, conclusions.

That version of events makes sense, but there are still questions. For instance, Saxo-Tinkoff have publicly said that Contador's second bike was numbered up, which led to confusion when pictures of it in bits emerged. But as many people have pointed out, the broken bike has Contador's timing chip on it: Logic would dictate that it's the bike he started the race on as it's unusual for a spare bike to have a transponder on. That being said, it's not impossible and pictures of the Saxo-Tinkoff cars at the start show numbered bikes on the roof. Although we haven't seen a high-enough resolution image to check whether they have transponders too.

@wjohngalloway Crappy iPhone shot from Epernay stage start. Looks like AC's bike has number on it on top of car. pic.twitter.com/sOOSUHyjDl — Dave IH (@daveih) July 15, 2014

On top of all that our friendly materials scientist Trevor Allen has been in touch. He's currently doing a PhD on impacting carbon structures, so he feels well qualified to have a look at the aftermath...

Ignoring all comments and speculation, quite a bit can be read into the picture of the broken bike. Failure analysis like this is a widely used, and experts are regularly involved in court cases. Two tubes of the bike have failed (obviously): At top end near the seat tube - this appears to be a tensile failure. The failure surface is quite complex due to the joins with the ST and stays. I suspect there is a mix of join failure and fibre failure in this location all rolled into one, but the key is tensile. At the down tube - two points of interest: firstly the tube has failed at approximately 45 degrees to its axis. Unlikely a tensile failure, and torsion would be more of a rip - I suspect that is a compressive failure. Secondly the hawkeyed will also notice that the failure interacts with the bottle cage mount. This is will act as a stress concentration, and is possibly the initiation site of the DT failure. So - tension at the top tube and compression at the down tube. If you load a bike with a frontal impact – i.e. a horizontal load at the front axle – then you'd get just that: the fork is a long lever arm which will compress the down tube, and because of the rotation about the head tube junction you'll get tension in the top tube with failure occurring at the areas of highest stress. I can't see how you could drive over a bike and cause that kind of failure of the tubes (why are the wheels and bottle cages intact and the tubes not crushed?). Dropping it from above your head when getting it off the car on to the front wheel would be the right load case, but I suspect the energy wouldn't be sufficient to cause that failure; having the rider on the bike increases the impact energy significantly because of the added momentum in the collision. If I was asked to look at that bike in my job and guess how it failed, I'd definitely say a big load in from the front. Here are three ways that could happen: 1) A massive pothole with a fistful of last minute front braking (possibly, but not so convinced) or the crash which occurred after the pothole impact or indeed a combination of the two (some damage caused through pothole impact - then said damaged carbon with some delamination hurtles into a tree/verge etc causing a snap) 2) One car drives in to/closely past in same direction another car and two bikes on the racks collide. Contador's bike is likely to be on the outside, as it's just been racked. 3) The mechanic has bike ready for Contador and Belkin drive through (i.e kind of what is in the picture), the bike gets tangled in the rack and there is a convenient tree/verge to support the rear wheel. If this was the case the man holding the bike was pretty lucky he didn't get wedged too!

I don't think the snapped bike caused the fall. Nor do I think the bike snapping in a big crash is necessarily a bad thing.

Latest update

Foto desde el coche @lampre_merida q la bici de @albertocontador se rompió enganchanda, con el coche de Belkin. pic.twitter.com/vX36iUMV3G — Joxean Fdez. Matxin (@Matxin_) July 15, 2014

This newly emerged photo provides a much better view of how the Specialized frame snapped as a result of becoming tangled with the Belkin team car rack. You can also see the bike clearly has a race number attached, and though it's not 100% possible to confirm, it does look like there is a transponder fixed to the chainstay. This is the most conclusive photo we have yet seen that shows how the frame suffered the damage, putting to rest the speculation that the frame snapped when he hit a pothole. At least for now...

This is one of the most bizarre incidents that we can recall in the Tour de France. Given the narrowness of the roads through the Vosges though and the team car racks bristling with spare bikes, it's a wonder it doesn't actually happen more often.

So, Contador's bike didn't snap underneath him, as many thought has happened, or snap when he crashed either. Saxo-Tinkoff's official version of events raises a few further questions but there's nothing in there that can't really be explained. The damage to the bike is inconclusive: given that driving it into another car on the rack, and riding into a pothole, are both a large frontal load, you'd expect either to result in the failure we see.

We wonder what Contador will make of all the fuss, but we're sure he's got more important things on his mind. We wish him a speed recovery.

Photo credit www.tinkoffsaxo.com