I recently purchased a “new” used bike. The bike has Reynolds Forty Six with DT240 hubs. I took her out for her maiden voyage and I noticed that when coasting down hill the bike has a bit of a pulsing sensation to it. I am new to carbon wheels and was wondering if this is normal or should I be concerned? Could something other than the wheels be causing the sensation? Thanks for any and all input.
I recently purchased a “new” used bike. The bike has Reynolds Forty Six with DT240 hubs. I took her out for her maiden voyage and I noticed that when coasting down hill the bike has a bit of a pulsing sensation to it. I am new to carbon wheels and was wondering if this is normal or should I be concerned? Could something other than the wheels be causing the sensation? Thanks for any and all input.
Do you mean vibration?
When I first started to use deep carbon wheels a lot of strange feelings manifested. Mostly good/fast feelings. I did notice going downhill, when speeds exceeded 25-30mph or so with a light to moderate cross-wind I felt like the bike would speed up and slow down, or ‘pulse,’ as you said. After a while this became nearly normal and almost fun. My LBS told me it was how the air was passing over the leading edge of the carbon depending on yaw angle. Something to do with pressure build up and release. Then I got schooled on all things toroidal and why I should buy some Zipps.
No vibrations, just a sensation what was previously described as speeding and slowing in a pulsing manner. Never had felt that on my previous bikes so I was uncertain if it was to be expected.
Valve extenders? If so, you could be feeling their weight once/revolution.
ADD: Tubular tire valves + extenders can also contribute to a mild ‘pulse’ sensation. (Uneven tubie gluing also…)
I recently purchased a “new” used bike. The bike has Reynolds Forty Six with DT240 hubs. I took her out for her maiden voyage and I noticed that when coasting down hill the bike has a bit of a pulsing sensation to it. I am new to carbon wheels and was wondering if this is normal or should I be concerned? Could something other than the wheels be causing the sensation? Thanks for any and all input.
If you have a wheel magnet on your front wheel check that it is not on the same side or near the valve extender.
Maurice
Thanks for the input. I’ll be doing some more evaluating to make sure it isn’t a set up issue (valve, glue, magnet). Hopefully it is just the experience of having some carbon wheels.
Thanks for the input. I’ll be doing some more evaluating to make sure it isn’t a set up issue (valve, glue, magnet). Hopefully it is just the experience of having some carbon wheels.
Spin wheels with bike on work stand, etc. You’ll probably see some pulsing. As wheels slow, observe and note what part of the wheel comes to a rest at the bottom (6 o’clock position). This is the the ‘heaviest’ part of the wheel (usually the valve area) and most likely the source of pulsation.
Adjust if possible (valve, extenders, magnet, etc).
(Note: Some folks attach a small counter-weight on spoke opposite the valve stem for balance and a smoother roll.)
Tires themselves can have some imperfections, or even damage creating a minor buldge.
But otherwise +1 on the valve. Kepp in mind the tube is thicker there too, and I think enough that hte tire can even seat slightly different. These wheels may jsut be quieter and roll smoother or be stiffer so you’re feeling more now. The vibration from the wheel rotation (I think around 100-150hz, may also match the frequency of a carbon wheel better than an aluminum one, which might have a much higher 1st or 2nd order resonance frequency. Something else to consider.
I’m with Brushman on this one. Longer valve stems, and extra material at the rim around the valve hole, add to this sensation. I have Vuelta carbon clinchers and it’s far more noticeable than on my standard Mavic Aksium training wheelset. My friend also has it on his older Zipp 404 tubulars.
I put my computer magnet directly opposite, but that doesn’t really do much to “fix” it. And adding extra weight is probably unnecessary, IMO. You’ll get used to it.
If the wheels are way out of round, you might get that sensation also.