Sunday, April 14, 2013

Garmin Edge 500: broken tabs

As I rapidly descended Panoramic Highway toward Highway 1 from Mount Tamalpais with my Roaring Mouse teammates, I passed by some sticks on the side of the road. Suddenly something hit my foot. That didn't feel like a stick... I felt my pockets and nothing seemed loose, so perhaps it had been a stick after all.

Seconds later one of the riders behind me shouted "computer!" And then I knew. My Garmin had fallen. A quick look at my stem confirmed it: the bracket was empty, a white sliver of a plastic tab the only remaining sign of my Edge 500.

Fortunately after a bit of searching we were able to find and retrieve the computer. Honestly I was as worried about losing the ride's data as I was about the computer itself. A quick inspection showed the problem: the plastic tabs on the back had sheared off. Indeed one of the tabs had already come off during a previous ride. But the one remaining tab seemed enough to hold it in place. I'd taken to using a piece of rubber cut from an inner tube to secure it, but when that didn't seem necessary, I started just putting the computer in the mount as usual. The other tab had decided to give up the ghost during the descent.

Here's the back of the Edge, tabs gone:

The curious thing is I've had this happen to me before, not just once, but on two separate units. So this is the third. Additionally, I've heard of others having the same issue. It's clearly a design flaw: a lot of stress is placed on these plastic tabs, which extend outward at a right angle, and that creates a stress peak at the corner.

I've heard this is a particular problem with the K-Edge forward mounts, which are metal and harsher on the Garmin's plastic. I'm not sure if this is true; the stock plastic mount seems harsh enough.

Is there some aspect of my use pattern that makes me particularly prone to this failure? I don't know. I am glad I got this one back and the data were spared: it was an excellent ride and I'd hate to have lost it.

6 comments:

djconnel said...

Follow-up: even though replacement units have only a 90-day warranty, and this unit was a replacement for another that similarly broke in November 2012 (5 months ago), as "an act of goodwill" Garmin agrees to replace it. Garmin has fantastic customer support but their warranty falls short in this instance, since the defect is a design one, and the fatigue life of the tabs is obviously less than what a typical user would expect, yet they have a good chance of outlasting the one-year warranty. That said, thanks to Garmin support for their help on this.

It's interesting how things like bike computers and lights can come out decades after the first units of their type and still have such obvious points of mechanical weakness. My other experience with this was my Niterider light clamp, which Niterider replaced for me with a superior design more like designs which have existed for many years.

Claude B said...

Never had issue with it after 3 years of use. Not even a sign of wear. I use the genuine Garmin plastic mount, so you may be right regarding yours wearing it faster.

djconnel said...

You're lucky! There's a thread on the topic on the Garmin forum.

Privateer29 said...

Here's a thought. When the mount is "Mounted" on the stem I have noticed that the plastic mount can actually deform around the stem over time. This wouldn't be a problem but for the fact that the tabs on the back of the edge units are at the 3oclock and 9oclock positions so when the unit is stem mounted these would take increased load from a deformed mount. the concern about the K-edge Mount is valid but I feel it's more related to the CNC machined internal edges of the interface being razor sharp and actually shaving plastic off the edge unit. I actually took to my K-Edge with a tiny file to remove any sharp edges prior to installing the Edge and now it is smooth and super gentle on the plastic. One thing that you can be sure of is that the K-edge does not deform like the plastic mounts.

djconnel said...

I like your thinking: it's good to focus on things which might be different about stem mounting, and this is a good one. I may try a forward mount. It would yield less glare on the poorly visible Edge 800 and more peripheral view of the road when looking at the screen for both Edge 500 and 800. It would also likely reduce tab stress (shaving issues aside in the case of the K-Edge) since the forward mounts are cantilevers.

djconnel said...

I like your thinking: it's good to focus on things which might be different about stem mounting, and this is a good one. I may try a forward mount. It would yield less glare on the poorly visible Edge 800 and more peripheral view of the road when looking at the screen for both Edge 500 and 800. It would also likely reduce tab stress (shaving issues aside in the case of the K-Edge) since the forward mounts are cantilevers.