Rick Posted March 28, 2011 Posted March 28, 2011 I've read that a power trainer can put undue stress on your frame over time and that it's advisable to use a cheap spare bike for that purpose. Is this valid? The book was written in the 90s so I'm hoping frames have improved since then. Also, possibly this affects aluminium more than carbon?
Christie Posted March 28, 2011 Posted March 28, 2011 No, if it was a danger to the frame, high end bikes would have a "don't use on trainer" line in their warranty. Also, the forces experienced by the frame would be the same regardless of material. Because carbon is stronger and has better fatigue life than aluminium, said forces would be handled better by a carbon frame. My guess would be that the rear axle is the part where some difference applies - it carries more load in an A-frame trainer than when out on the road. I would recommend buying a dedicated rear axle for trainer use.
Wyatt Earp Posted March 28, 2011 Posted March 28, 2011 Yes, my poor bike gets stressed every time I take it near that trainer in winter, the poor thing knows what's coming it's way.
rudi-h Posted March 28, 2011 Posted March 28, 2011 Surely it stresses the frame. A free wheel can react to force by tilting over, but in a trainer this motion is prevented by a hard connection to the drop-outs? true, but with a free wheel also hits potholes @40km/hr and is exposed to seriaaaaas vibration and impacts on shite roads that a bike on a trainer is not exposed to. I'd be surprised if anybody on the hub can give you an accurate force comparison, but as the other guy said, the manufacturer would state clearly if the bike is not suitable for trainer use.
Andrew_ew Posted March 28, 2011 Posted March 28, 2011 On the trainer the other day I looked at my bottom bracket area and was really shocked at how much movement there was there. It appeared that with the rear axle being held rigid there was a lot of torsion on the rear stays which was side to side - I am not an expert but I am not sure that frames are designed with that in mind - again I am not an expert but have a look at how much movement there is next time you are on the trainer.
rudi-h Posted March 28, 2011 Posted March 28, 2011 (edited) On the trainer the other day I looked at my bottom bracket area and was really shocked at how much movement there was there. It appeared that with the rear axle being held rigid there was a lot of torsion on the rear stays which was side to side - I am not an expert but I am not sure that frames are designed with that in mind - again I am not an expert but have a look at how much movement there is next time you are on the trainer. I think the only reason why you only see it on a trainer is because its impossible to look at the "movement" while you're riding normally. Take the example of doing a tailslide and then you hit a rock / root / curb with your rear wheel to the extent that your rear wheel stops dead and you fly over the bike. It's a huge impact, plus the force is applied to the outer diameter of the wheel, which amplifies that force on the rear stays with a factor of up to 2.3X, depending on the angle that you lean into the slide. It may not happen all the time, but I think your bike takes a lot more hammering every now and then while riding. As I've said, I don't think that anybody that doesn't design bikes for a living will be able to provide solid evidende, but i don't think its an issue worth worrying about Edited March 28, 2011 by rudi-h
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