GilesM
Legendary Member
- Location
- East Lothian
Out for a ride on the local lanes on my hardtail last night, bit of a shock when this bit broke, I was out of the saddle going over an old railway bridge, some how I stay I stayed on the bike:
An interesting break
- Thread starter GilesM
- Start date
Page may contain affiliate links. Please see terms for details.
I bet that came as a bit of surprise! Glad you're okay. Have you dropped it hard or had any off's on that side (pedal hitting the ground and weakening the crank arm perhaps)?
Spiderweb
Not So Special One
- Location
- North Yorkshire
Email the photos to Race Face ( with some close ups) they will be interested to see them. I bet they send out a replacement.
greekonabike
President of the 'Democratic Republic' of GOAB
- Location
- Kent
Bloody hell I bet that was a shock when it happened. Fair play for staying on.
GOAB
GOAB
OP
OP
GilesM
Legendary Member
- Location
- East Lothian
The Chainset is about 10 years old, it's the second bike its been on, and it has had some rough moments (especially off road) over the years, I think Tim H is right and it was probably cracked for a while, difficult to tell as I would have just seen a scratch in the black anodising, and there are quite a few of those. Will send a pic to Race Face, see what they say, but I really would not expect a replacement, and would feel a wee bit guilty if they sent me one, it's not been quite as new for a while now.
I'm sure I wobbled quite badly when it happened, it was very dark, and I thought I'd just pulled my foot out, then was a bit surprised to find there was no pedal to clip back into, just glad there was nothing behind me. It was lucky I was close to home, however, four miles back home with just a left pedal is not too much fun.
The good point is, a good reason to buy shiny new stuff.
I'm sure I wobbled quite badly when it happened, it was very dark, and I thought I'd just pulled my foot out, then was a bit surprised to find there was no pedal to clip back into, just glad there was nothing behind me. It was lucky I was close to home, however, four miles back home with just a left pedal is not too much fun.
The good point is, a good reason to buy shiny new stuff.
Yellow Saddle
Guru
- Location
- Loch side.
Thanks for posting the photo's but can you perhaps get a close-up of the eye, particularly from the outside of the crank, perhaps remove the pedal and stick the broken off bit on or hold it in place whilst snapping.
If you do an age analysis on the crack you'll notice, as Tim said, there are two colours - grey and silver. The grey part is where the crack travelled slowly trhough the metal and the silver part is one instantaneous crack. You'll notice that the crack started where the pedal "eats" into the crank and causes a stress riser. The pedal/crank interface is poorly designed since there is a lot of movement between pedal and crank. A thread and collar relies only on the collar's width to keep the pedal axle stable and a small collar like that can't do the job. Using up the same space, a conicall collar such as that found on wheel nuts, prevents this type of crack, but the industry doesn't want to resort to sensible design.
This type of crack is quick common with very powerful and heavy riders. Do you fall in that category?
ColinJ
Puzzle game procrastinator!
- Location
- Todmorden - Yorks/Lancs border
Yikes - that was a lucky escape; a broken crank at the wrong time could have devastating consequences!
I have broken 2 square taper cranks at the bottom bracket end.
One crank snapped when I stood to climb a steep hill so I wasn't going quickly and managed to stop with no damage done to me other than the pain of the inevitable meeting of goolies and top tube!
I spotted the other problem when cleaning the bike ...
It goes to show that it pays to make regular checks of your bike for problems!
The owner of this bike clearly had not done so ...
I met him on an audax ride, just after a 20% descent. He had stopped when the front of his bike suddenly 'felt wobbly'. The fork breaking off a bike on a fast descent could easily kill its rider! You can tell from the rust that this problem had been developing for some time. A quick once-over at any time in the previous few months would almost certainly have revealed the problem.
I have broken 2 square taper cranks at the bottom bracket end.
One crank snapped when I stood to climb a steep hill so I wasn't going quickly and managed to stop with no damage done to me other than the pain of the inevitable meeting of goolies and top tube!
I spotted the other problem when cleaning the bike ...
It goes to show that it pays to make regular checks of your bike for problems!
The owner of this bike clearly had not done so ...
I met him on an audax ride, just after a 20% descent. He had stopped when the front of his bike suddenly 'felt wobbly'. The fork breaking off a bike on a fast descent could easily kill its rider! You can tell from the rust that this problem had been developing for some time. A quick once-over at any time in the previous few months would almost certainly have revealed the problem.
D
Deleted member 1258
Guest
One thing I've noticed with that bike is the slots cut into the nut holding the brake on, theres also a second nut underneath it, looks well bodged.
Wobblers
Euthermic
- Location
- Minkowski Space
Good to read that your interesting break resulted in only some inconvenience rather than anything worse.
I think that @Tim Hall and @Yellow Saddle have it: the crack's been there for some time. If, as you say, that crank's ten years old, assumingg you've done an average of 1000 miles a year on it, that represents 10 million revolutions. Considering that it gets loaded and unloaded once per revolution, that's also10 million loading cycles. That's a lot for an aluminium part (usually the fatigue life for aluminium is assumed to be 10 million cycles, though actual life will depend on what sort of loads it actually sees)! So it looks like a fatigue failure to me. If you look carefully at the fracture surface, on the grey part, you might be able to spot a serious of cconcentric rings propagating out from a single spot - that's the classic sign of a fatigue crack growing over time.
The upshot is the crank probably reached end of life. The other crank should be considered suspect. As should any handlebars or stems that are as old and have seen similar use! I'd replace those as well if they're that age - failure of those is likely to lead to worse consequences.
I think that @Tim Hall and @Yellow Saddle have it: the crack's been there for some time. If, as you say, that crank's ten years old, assumingg you've done an average of 1000 miles a year on it, that represents 10 million revolutions. Considering that it gets loaded and unloaded once per revolution, that's also10 million loading cycles. That's a lot for an aluminium part (usually the fatigue life for aluminium is assumed to be 10 million cycles, though actual life will depend on what sort of loads it actually sees)! So it looks like a fatigue failure to me. If you look carefully at the fracture surface, on the grey part, you might be able to spot a serious of cconcentric rings propagating out from a single spot - that's the classic sign of a fatigue crack growing over time.
The upshot is the crank probably reached end of life. The other crank should be considered suspect. As should any handlebars or stems that are as old and have seen similar use! I'd replace those as well if they're that age - failure of those is likely to lead to worse consequences.
Richard A Thackeray
Legendary Member
Stephen Roche had similar problems in the 1987 Giro, when he felt an oddness in the handling, whilst descending to increase his lead over Visenti, & found at the stage-finish that a blade had cracked/was loose in the crown
