Mental Mamba Posted September 27, 2015 Posted September 27, 2015 Hi All Is this a common problem with the Mavic 50mm deep sections. Is it still safe to ride or should i just claim a new set from my insurance, just had my MTB rims replaced......
Spoke101 Posted September 27, 2015 Posted September 27, 2015 haven't seen that before. Would not recommend you continue riding with that wheel.
raptor-22 Posted September 27, 2015 Posted September 27, 2015 Seen plenty rims crack in similar positions due to excessive tension in the spokes.
Mental Mamba Posted September 27, 2015 Author Posted September 27, 2015 Seen plenty rims crack in similar positions due to excessive tension in the spokes.haven't touch the spokes since i got the rims.....
raptor-22 Posted September 27, 2015 Posted September 27, 2015 Didn't suggest you touched them although you must have or how else did they fit into the frame?
Reg Lizard Posted September 28, 2015 Posted September 28, 2015 See there's a clown on this thread Mental you ride to hard...you know it...you are an animal on the bike...get a new set of darhhorse wheels and move on... For those that do not know, I have been through 2 mavic SL and 2 Cosmic SL rear wheels the last 5 years...they just don't last with the "big" boys pushing the big gears
David Marshall Posted September 28, 2015 Posted September 28, 2015 Those cracks are common on the Mavic Alu/carbon rims. Not from excessive spoke tension (excessive tension will cause the rim to collapse - not crack). This is from the rim flexing. Not enough spokes or the rim too light or both. The alu section looks like the Mavic Open Pro but is nowhere near as strong. Price you pay for light wheels. My opinion - not safe to ride. The rim will flex even more due to the lessened tension in the damaged area and will eventually collapse.
raptor-22 Posted September 28, 2015 Posted September 28, 2015 David excessive spoke tension causes the nipple to want to pull out of the rim. When the nipple unloads when that part of the rim is at the bottom of the revolution it then sees rapidly rising stress as the tension is reintroduced. So yes flexing is a definitely a contributor but if left alone and unriden those wheels will crack in the same manner.I've had a spare CXP22 wheel crack in the same way when built with radial spoke lacing. It was never ridden. Rim basically cracked while hanging in its wheel bag
David Marshall Posted September 28, 2015 Posted September 28, 2015 Evenly increasing spoke tension will strengthen the wheel up to an optimum point. Tensioning beyond that point will increase the radial strength and decrease the lateral strength. If you continue to tension the spokes further the wheel will collapse, that is fold to look like a Pringle chip. This collapse will be sudden, much like when you fold a wire rimmed dash sunscreen from a car. If you crack a rim from spoke tension either the rim was faulty or you put such uneven tension on one of the spokes that the rim would have been so out of true that you would not have been able to ride it. You are right in that when the wheel turns the change in spoke tension causes movement which fatigues the components and it is this movement around the nipple area that causes the cracks. A stronger rim with more spokes would take longer to crack or the stress would be shifted to the spokes. This problem is well documented in these wheels. Following is the first review I picked up on Google http://www.roadbikereview.com/cat/wheels/wheelsets/mavic/cosmic-carbone-sl/prd_479087_2490crx.aspx#reviews
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