Millions of Shimano cranks worldwide have to be inspected and possibly to be exchanged. Graduate engineer Dirk Zedler has been the most important expert on the subject of bicycle safety for years. TOUR asked him for his opinion on the crank problem.
TOUR: Have you already inspected affected cranks?
Zedler: Yes, we just asked our employees to bring along their bicycles and then carried out the Shimano inspection process. The important thing is to inspect the manufacturing code on both crank arms, as they could be of two different lots of production. And then we carried out the follow-up inspection process, i.e. dismounting the crank, unscrewing the chainwheels and cleaning them thoroughly - Shimano published very detailed inspection instructions. On the document it looks cryptic, but in practise it wasn't hard. Our cranks were all sound.
67 euros for a specialist dealer
TOUR: The retailers get 67 euros for the inspection and Shimano estimates 45 minutes of work time. Is that realistic?
Zedler: It depends on how the bike looks like. If the crank is clean you can handle it rather quickly. I think, for a dealer who has a lot of road bikes that’s no problem. The difficulties come along with the mail-order bikes that don’t have a proper structure of dealers behind them. From 2012 to 2019 Canyon most probably sold several hundreds of thousands of road bikes and the probability that Canyon has Dura Ace or Ultegra is relatively high. Here I actually do see difficulties on how to wind up these cases.
TOUR: Can you really identify a damage?
Zedler: You see very clearly that a sound crank looks different from what can be seen on the Shimano pictures. We talk about small cracks, about small gaps in the bonded area etc. and the comparison was not an issue for my team. With bright light and a magnifier an experienced bicycle dealer is able to perform that. The pictures from Shimano in the user manual also show a real crack pattern on the outside, which means that when the two halves are loose or start to come loose, movement starts and this movement then leads to cracks that can be seen on the outside over time. Shimano says: Also have a look at the inside where you normally don’t look at.
TOUR: But what if the cracks that are so small that you can’t see them yet?
Zedler: That is exactly the difficulty with this matter: from now on you actually have to check the crank again at regular intervals. Any fatigue fracture, any failure is typically also a function of use over time. When you have checked it today it basically doesn’t mean anything - I have to repeat it again and again. That’s a little bit the deficiency of this recall. The crack growth can occur at any time. You perform the inspection and the bike has made 1000 kilometres, but then it changes hands and it is used by a someone who rides a lot, i.e. 10,000 kilometres the following year - the crank can then look quite differently. That means you have to check this crank regularly - one single inspection is definitely not enough. In my opinion, it has not yet been clearly communicated that these cranks have to be checked at least once a year when I am a normal rider. But if I'm a cycling amateur, I actually have to inspect the cranks every three months now in order to be able to ride in good conscience or safely.
Read the entire German article online.
The interview was held by Kristian Bauer