Front axle snap, design flaw?

bergerhag

bergerhag

Silver Level Site Supporter
A fellow swedish rider had his '09 front axle snap.
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I went out to shed and measured up my '10 axle. My bike is not rolling one more meter with that axle.

The bigger inner diameter where the fork yoke mounts passes by a tiny amount the larger outer diameter of same area. This makes the material thickness at the edge of spacer less than 0.6 mm [edit measured 1.3 mm] (0.0236 inches). :eek:



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Fortunately my '05 450 has got anoter style of axle. Swap imminent.
 

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More than likely, his wheel bearings froze and the spacer was rotating on the axle. Which made a weak spot.
 
gasgasman said:
More than likely, his wheel bearings froze and the spacer was rotating on the axle. Which made a weak spot.
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Hello...
It was my axle that snapped. I don?t think that there is a problem with the bearing, i have 2 sets of wheels (front and back) which i switch between, and i just switched all bearings front and back (about 20h ago) on both.

After i read your post i went out and checked the bearings and it rolled just fine, but still i could maybe be broke. I also took a video with my iphone that i could put up.

Here is two close up, but what i can see it?s a little rust there so maybe there has been a crack or something earlier.



 
OK.
Doesn't look like the bushing could have caused that.

Thanks for the warning to check ours along with the other safety checks.
 
Fredde N said:
Hello...
It was my axle that snapped. I don?t think that there is a problem with the bearing, i have 2 sets of wheels (front and back) which i switch between, and i just switched all bearings front and back (about 20h ago) on both.

After i read your post i went out and checked the bearings and it rolled just fine, but still i could maybe be broke. I also took a video with my iphone that i could put up.

Here is two close up, but what i can see it?s a little rust there so maybe there has been a crack or something earlier.



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I looks like it's been cracked for a while but still should have never cracked. If you had the wheel off 20 hrs ago you should have been able to see the crack.
 
It would be interesting if you who own 2007 and newer bikes could measure the depth of the first part of the axle, the one dimension that is 47.9 mm in my little drawing. Please post year too. Is this a bad batch of axles, or are they all like this? If all are like this, then it might not be as alarming as I first thought. We havent had that many reports of broken front axle. At least not yet.
 
I have an '07. I'll do that next time I have the front wheel off. I pull the wheels often to clean and grease the seals, and have never seen anything odd. This has got to be a first, so logically if it is a major design flaw I would think you would not be the first. Perhaps a machining issue with that particular part, stress riser set up on that step? Good point though. How was the bike ridden, both before and during the failure?
 
I saw this happen in real time earlier this year. It was however on a 2010 Yamaha WR450F. Everyone was in awe and luckily didn't happen at speed. Cracked and snapped in the exact same place too!
 
Ok, after more careful inspection, i have found it not so alarming. The inner diameter changes the last 3 mm, and the critical point thickness appears to be at least 1.3 mm. Still thin, but better than 0.6 mm.

The 2004 -2006 axles are much thicker at that point.
 
lankydoug said:
I looks like it's been cracked for a while but still should have never cracked. If you had the wheel off 20 hrs ago you should have been able to see the crack.
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Well, i guess i have had to wheels off 5-6 times during this time, because i switch between racing and practice wheels/tires, but i haven?t notice this. I ordered a new axle yesterday and i think i will put a small innertube/pipe that goes beyond this point on the new axle.

I don?t want to crash like this again because of this. When we picked up the bike the day after, i have had 4th gear in...
 
This is something you certainly don't see everyday and I'm not sure you'd ever notice it unless you were looking very closely. It does look like it had a crack previously (possible very small) and finally broke. Whether that crack was from fatigue, a flaw in design or machining, or something else I guess remains to be determined. Regardless I will certainly inspect mine as well and do some measurements when I have it off. If that section is as thin as your measurements indicate then I'd be a bit concerned as well. I'd think a piece of stock the exact thickness tacked across that area as you mention would be one good way to beef it up. I had a local welder do the same for the kickstand on my husky after a section was added in the middle to lengthen it.
 
Fredde N said:
Well, i guess i have had to wheels off 5-6 times during this time, because i switch between racing and practice wheels/tires, but i haven?t notice this. I ordered a new axle yesterday and i think i will put a small innertube/pipe that goes beyond this point on the new axle.

I don?t want to crash like this again because of this. When we picked up the bike the day after, i have had 4th gear in...
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4th gear! Yeow! Hope you didn't get hurt....

Even having the wheel off as many times as you have, I'm not surprised you didn't notice it, I mean, how many times do you hear of an axle failing.:confused:
 
Looking at Fredde's pictures and using an image editor to do a few measurements, it still looks like material thickness is in the 1 mm range. I am not going to take the risk on using this axle. The 450 is gonna be an axle donor, and I am gonna cut my axle in half. I'll get back with pictures.
 
In the quest for light weight, we sometimes bump the limit of durability, and the weight/cost/MTBF ratio has to be fine tuned. A 250F is a perfect example. This is not neccessarily from a design standpoint alone, but from mfg and material tolerances being much less forgiving. Anyway, I'm not going to worry about it unless Nambo and Ivan start having issues. 4th gear? Wasn't a hard landing over a double was it?
 
bukwheat said:
4th gear! Yeow! Hope you didn't get hurt....

Even having the wheel off as many times as you have, I'm not surprised you didn't notice it, I mean, how many times do you hear of an axle failing.:confused:
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I did get hurt. Dislocated left shoulder and landed with the right upper leg (muscles) on a rock, the shoulder is ok, i got it back by myself the first thing i did after crash (its not the first time it happens), but my leg still hurts in the muscles. I?m planning on riding this weekend if i only get the new axle.

Bergerhag:I saw you were going to Hammarstrand, i can send the axle with some guys from Ume?, so can you inspect it more closely when u get back home, if u want.
 
Thank you Fredde, but it wont be necessary. I have cut mine in two.
If it was a mounting bracket for the exhaust or some other non essential part, sure, that wont matter if it breaks. But the front axle? That should NEVER happen.

Anyway, each to his own I guess. I wont be using an axle like that


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GMP said:
In the quest for light weight, we sometimes bump the limit of durability, and the weight/cost/MTBF ratio has to be fine tuned. A 250F is a perfect example. This is not neccessarily from a design standpoint alone, but from mfg and material tolerances being much less forgiving. Anyway, I'm not going to worry about it unless Nambo and Ivan start having issues. 4th gear? Wasn't a hard landing over a double was it?
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No hard landing. But i use 13-52 for the moment, so it?s more strong than fast.
 
Yeah, I don't see the point of pushing that cut so far, a few mm more overlap won't hurt weight. Nice radius both inside and out though. See if the broken part is just like this one. Perhaps its not by design? What was the hardness like when you cut it?

These are Euro Sachs fork bikes right? Is the Sachs axel the same as the Zoke axel? Foot "looks" identical. Time to hit the parts .PDF.

It just occured to me that the dimmension from the edge of the larger clamping dia (ID) to the smaller dia can be measured on the bike in seconds. I'll do it tonight.

Lets not start a panic, there are thousands of these in service for years with no documented failures that we have heard of.
 
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