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Chainstay flex - creaking?
I've been chasing down an annoying creak that is only present at the top of the power stroke (around 12 o'clock to 2 o'clock) and only under heavy power. Present on both sides.
I've ruled out (through part swaps or replacement) the following:
Pedals
BB
Saddle
Seatpost
Cleats (SPDs)
Shoes
Wheelset
Also present whether I'm in or out of the saddle and in all hand positions on the bars.
If I hold the rear brake on and push down on the pedal I can see visible flex (twisting) in the chainstays and this corresponds with the creak - once again it is present on both sides. I'm a heavy rider (120kg-ish), should I expect the frame to deflect that much?
Bike is a Merida Cyclocross 500. Thru-axle front, QR rear, mudguard fitted to chainstay bridge (I've lubed and tightened the fixing points for those)
If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.
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12 comments
Have you got lightweight skewers? those titanium ones?
If so throw them away and get some decent internal cam skewers. Like Campag Zonda and above or Shimano Ultegra and above. Do them up tight. Worked to get rid of a hideous squeak in my bike!
Also, did you grease the BB cups / bearings before they went in. HOWEVER!! If your chain stays are actually visibly flexing (rather than the BB area moving side to side) I don't think this is normal. I've owned a number of alu bikes. I'm only 85 kg but put out 1400W in a sprint. I've never seen much flexing in the chain stays (though it's not hard to achieve lateral movement through the BB)
If your frame is lugged alu, I'd suspect a lug intersection, if it's welded (like Cannodnale etc) then you will be able to see cracking in the paint where ever there is movement. Ultimately a trip to your LBS is probably a good idea, or a frame builder, or an engineering fire with an ultrasound scanner.
Personally, as it always happens at the same point on the pedal stroke I'd second Spindi's choice of the CR bolts.
Try giving the barrel adjuster for the front derailleur a little twist.
Cables around the head tube is a classic one for this. Seen it sound exactly like a creaking BB because of course you move the bars every pedal stroke.
Another overlooked possible is the chainring bolts. Copper grease them.
http://www.halfords.com/motoring/engine-oils-fluids/grease/halfords-copper-grease-20g
You say you have eliminated the wheelset, but did that include the rear QR?
This was such a common cause of random creaking under power for so many of my customers. They also rarely believed me when I told them; I had to actually demonstrate it, which was odd, as I usually didn't charge them for the repair. If it were me, I would have said "thanks very much" and toddled off, whether I believed the diagnosis or not, as long as I got a free repair!
If you haven't, it's worth trying a different QR, greasing the pivots on it and doing it up a bit tighter.
Thanks. Punctured on the way home last night and QR was bone dry so it may be that. Will test once the replacement tyre has arrived (long walk of shame back due to not having a tyre boot (or a fiver)
Ta - frame is aluminium and is disc braked. Will have a check for cracks - hope not as its only 9 months old
Frames flex alot if they didn't they'd be horrible to ride the place you really notice it is on a trainer.
As stated check for cracks though just to be safe!
Steerer/stem? Doesn't sound like it but if you stand, gripping the front wheel between your knees and put weight on the 'bars in different ways. Unlikely to be the source but a 30 second elimination job.
You don't say what the frame material is, but I'd check carefully for cracks in both seatstays and chainstays.
Grease the brake mounts and pivots to eliminate cause. Re assess