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Has anyone come across this problem before?
I fitted a brand new set of Answer SL carbon bars to my bike yesterday, went for a ride for a couple of hours and afterwards found some indents on the bars where the brake levers have been....
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Now I've owned carbon bars before, so I know what I'm doing torque-wise, so I was pretty shocked to see what I was seeing as I'd only nipped down the shifters and brake levers, maximum 2nm torque. The bars are rated by the manufacturer to 6nm.
So I started doing a bit of investigating to work out what went wrong. I'm running Shimano Deore kit on this bike including M615 levers and calipers. I checked the old bar that was on this bike and low and behold, there was some very similar marks on there too although not as pronounced.
I checked the lever clamps themselves and found this.....
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The clamp itself looks like the alignment is funny. When attached to a bar...
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...all the clamping force is being transmitted to the bar at one point. The white bit of paper is so you can see the visible gap between the rest of the clamp and the bar, which should fit snugly.
I tried with three sets of bars, and it is the same situation, so it can't be the diameter of the bars themselves which are out.
I looked at how the shifter pods attach to the bars and the clamping force is spread evenly throughout.
Has anyone else come across this problem?
I always run a finger round (oo-er), to check but that looks pretty bad. I'm probably more wary of clamping loads on alloy than carbon. Is there no way it would fettle out with a file or emery ?
The edges of the clamps themselves aren't actually sharp, and I always rub a bit of fine sandpaper on the insides when I first get new brakes or shifters. With this set of levers, the problem is that the part of the clamp that the screw tightens down doesn't seem to be the correct diameter for standard bars.
A couple more pics to show the problem...
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Points one and two don't seem to match up when the clamp screw is done up. When compared to say an XT lever clamp...
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..it looks like the sides of the clamps on my brakes were designed for different diameters.
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Snug fit on the reservoir side...
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...while the other side doesn't appear to be the diameter, so excess pressure is being applied to the bar at one point when done up.
That definitely looks wrong. As you say, the swinging part of the clamp appears to have been made for a different diameter of tubing.
Isn't there a shim/spacer on the fixed side of the XT lever in that image posted? Reckon that has anything to do with it?
As above, missing spacer
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On the XT lever there's a shim on the reservoir side. Even with a shim on that side on my brakes, the non-reservoir side would still dig in to the bar at an awkward angle because its a different diameter to the bar.
Edit. No you're right.
It just baffles me. The non-reservoir side of the clamp on both brakes isn't even the correct shape for a 22.2mm bar.
I've been using them for over 3 years without realising, and it took the trashing of a brand new carbon bar to find out. 😥
Dont know whats going on with the XTs but the lack of spacer on the deores means the bars arent going to sit in the clamp the way they should do, ime you'll always get some marking on carbon bars no matter what.
I have a set of 615's so just tried them on the end of an alloy easton haven bar and they fit ok
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On a set of alloy bars where they have been previously fitted I can see slight horizontal marks that match your indentations, but they are only very slight and no worse than the circumference marks on the bars from the clamps.
Looks like there is an issue with your set.
Dont look trashed
Those XT's have a spacer for the new i-spec 2 shifter mount, the M615's are i-spec b and so don't use the i-spec 2 spacer.
@ dirtydog - I'm pretty sure its not a spacer issue because I'm not running Ispec shifters and even with an Ispec spacer the non-reservoir side still wouldn't fit round the bars like Mark's above.
Looking at your [url= ]last picture[/url], it seems plausible that the bolt was overtightened against some strong handlebars at some point and the clamp gave in; the current pressure point acted as a pivot.
The fact that the clamp ends are not parallel at the gap also (kind of) supports this assumption.
Ooooh! Sherlock in da house! Looks a good call.
@devash Looking at the photo Mark posted I think your right, those 615s I pictured look like they have a spacer in them so assumed yours would have them as well.
Looking at your last picture, it seems plausible that the bolt was overtightened against some strong handlebars at some point and the clamp gave in; the current pressure point acted as a pivot.
The fact that the clamp ends are not parallel at the gap also (kind of) supports this assumption.
I think this is the most likely scenario other than manufacturing issues. Big rep for pointing it out because I would have never thought of it myself. I've got no idea how it would have happened though, apart from using a dodgy torque wrench at some point.
The overtightening theory, proposed by @otsdr, is backed up by your second picture, which suggests there is a slight 'crease' near the bolt head.