The internet is a strange, shouty place that lends itself to simplistic polarised arguments positions on many subjects and, even before we start on hydraulic vs mechanical, there’s a pair of diametrically opposed and entrenched positions on disc vs rim brakes. I would say that there’s 49% that swear that disc brakes cure cancer and 49% that think that Beelzebub himself invented them.

This post is for the 2%. The 2% that are open-minded enough to welcome new information regardless of whether it supports their position or not.

So, before I start, let me declare my bias as someone that chose hydraulic disc brakes for my long-distance tourer. The reasons for this are documented in the build details of the bikes, but my very specific set of circumstances and risk determination are different to yours and I wouldn’t be as presumptuous as to suggest that it’s the right answer for you.

But let’s get to the point of this post, three days ago I returned from a very enjoyable 500km ride down the Danube from Regensburg to Vienna.  It’s far from being the most challenging ride, apart from the 35-38C heat, and the surfaces are pretty good; no, they’re excellent!  But by the time we’d got 300km down to Linz, I had snapped two spokes on my rear wheel.  I had also snapped another two within the previous 6 months.

Let me add a little more context now, the 700c wheels are handbuilt by one of the leading touring bike wheel builders with Sapim race spokes and Ryde Sputnik rims on Shimano XT disc hubs.  Nothing too exotic there, quite a proven combo, in fact it’s a rim/spoke combo that has almost certainly done many millions of miles around the world, so I was a little perplexed.

I’m a big chap (110kg+) and I load the bike so that it rolls with an all-up weight of 60-75kg.  That’s a HEAVY rolling rig of 170-190kg!!!  So I figured that I was just putting too much weight on the wheels and catching the occasional bump that would snap spokes.  But this still didn’t really add up as a good theory for wheels that were reputedly “bullet-proof”

So I dropped the wheel-builder a note from Austria telling him the story and giving him some of the background on loading and terrain.

He was concerned, baffled and felt overly-responsible.  I explained that because we had built two identical bikes and it was only my rear wheel, the one that took the most weight, that was having these issues that I was sure that the problem was withe the rider not with the quality of the components or the wheel build.

He asked me a few more pertinent questions:

  • Do the spokes always snap at the same point?
  • Is it always on the same side?
  • Am I balanced in my braking?

Yes, they all snap right at the nipple.

Yes, all failures have been on the non-drive side where the disc is.

Ahhhhhh, maybe not so much on the braking.  As an ex-motorbike rider, I have a tendency to favour the rear brake and as a speed freak, I also have a tendency to come in a bit “hot” and be a bit enthusiastic with the very capable Magura MT5 hydraulic disk brakes.

The Eureka moment happened with a 25W lightbulb coming on in my head as the wheel-builder went on to explain that with disc brakes, all the braking force is transferred to the rims from the discs via the spokes.  A gorilla grabbing the rear brake on a 180kg rig shifting at 20km/h is going to be too much for ANY spoke.  That would explain the most recent failure at Linz on an excellent surface as the superb grip of the Mondials fought against the hydraulic action of the Maguras and another spoke let go.

As I said, problem was with the rider not the quality of the wheel!

I replaced 2 broken spokes at Linz, the wheel was a bit out of true but it still rode well, and then consciously balanced my braking a bit better, still with a bit of rear bias but no longer the bake brake only.  I was also a little more circumspect on my approach to stop.

It’s only 200km from Linz to Vienna but all 36 spokes have remained intact and I have a degree of confidence that they will do now for a while yet.

It would be a good point from someone that would say that this would be less likely to happen on 26″ wheels with rim brakes.  Yup.  But it’s all a trade-off I’m sticking with this combo for the benefits of how 700c wheels roll and the confidence in the stopping power of this brake/tyre combo, even allowing for the fact that I may (very) occasionally have to swap out a spoke.

Moral of the story:

You can buy all the quality kit you can afford but riding with Mechanical Sympathy is still your best defence against failure

 

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