Sprockets damaging freehub body

jrab
jrab Posts: 99
edited February 2009 in Workshop
Hi,

I'm hoping someone can give me some confidence on an issue with my new wheels.

I got a set of Planet-X Model B wheels a few weeks ago, they ride really well and I'm generally chuffed. However, I had reason to take the cassette off last week and found that the middle (individual) sprockets are already chewing the splines on the freehub body - this is after 3-4 rides and less than 150 miles total (winter bike & MTB better for recent weather!). I had to tap the cassette and then wiggle the sprockets over where the freehub splines have distorted to remove it.

My old set of Shimano R500s have done about 5000 miles with no issues and show every sign of going on forever. I appreciate lightweight wheels with aly freehubs won't be as durable as steel ones, but I expected the Planet-Xs to be reasonably durable and able to hack at least a couple of thousand miles. However at this rate I'm wondering if I'll need to throw freehub bodies at them every couple of months.......

Does anyone else have experience of this issue with freehubs generally? Once the initial notch has started does it stabilise, or does it carry on tearing through the splines at the same rate? Roughly how long do they last normally?

I did track down and order some American Classic pins (see
http://www.amclassic.com/pdfs/web10_Speed105.pdf) - however they don't seem to fit. Although my cassette is Shimano 11-25, the cog labeled "A" on the instructions has no holes in, so the pins don't fit flush with top of cog D as they should.

Thoughts would be appreciated!!

Regards,
Richard.

Comments

  • nicklouse
    nicklouse Posts: 50,675
    http://www.bikeradar.com/forums/viewtop ... netx+model

    it is a known issue on alloy bodies with cogs that are not on a carrier.

    generally it is just cosmetic.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • andylav
    andylav Posts: 308
    There's an easy DIY fix to prevent this from happening on any alloy body, similar to the American Classic pins.

    Get three pop rivets (various diameter shafts available so just select one closest in size to holes in the sprockets) - place the open end of the rivet through the small holes in the individual sprockets and spacers - cut the rivet shaft to length (slightly shorter than flush with the last sprocket to allow for compression under lock ring tightening - just over 10mm in my case) - repeat with the other 2 rivets - fit final sprockets and lockring.

    Cheap and easy fix that prevents any of the individual sprockets from moving independently when under load and chewing through the splines (one of my sprockets had cut through every spline before I discovered the problem so I do this as a precaution on every new alloy body now).

    Hope this helps
  • jrab
    jrab Posts: 99
    Thanks guys.

    Andylav, good tip about the pop-rivets, was trying to think where I could get something to replicate the American Classic pins but make them fit my cassette. Hardware store for me tomorrow.....

    Seems from the other post linked that this is a potential issue with many lightweight alloy freehubs?

    I have to say, I think this is more an issue of poor engineering on the cassette rather than the freehub. The middle sprockets are the ones that get most use, so what does Shimano do? Make them individual sprockets so all the load goes through just the tabs on that one sprocket, rather than sharing it along a whole carrier like the largest and smallest sprockets. Then just to compound the problem, give those individual sprockets just six splines not the full nine available on the freehub. So the pedalling forces of the sprockets you use most are carried by a relatively tiny area of the freehub.

    Would this happen if those sprockets used all nine splines? Woould that add more than a couple of grams or a couple of pence to the cassette?

    Richard.
  • andy_wrx
    andy_wrx Posts: 3,396
    There was another post on a while ago from someone saying they couldn't get a SRAM 10sp cassette to fit on their Shimano 10sp-only alloy hubs

    - there are some 10sp Shimano wheels with an alloy freehub body (DA and Ultegra from a couple of years ago, not current ones as these have a titanium freehub body).

    Shimano obviously realised that alu alloy was softer than steel, so whilst the spline pattern is the same on these wheels as all other Shimano-fit wheels, they made the splines taller and hence the corresponding grooves in the cassettes deeper.

    Shimano 8sp & 9sp cassettes with shallower grooves won't fit on these freehub bodies, hence these wheels are 10sp only.

    Other cheaper Shimano wheels like your R500's have steel freehub bodies, with shallower splines, so will take 8sp or 9sp, or 10sp with a width spacer washer - the shallower splines fit in the deeper grooves OK and the steel is tough enough for the slight shuffling-about movement not to be a problem.
    Same with the latest DA & Ultegra wheels with the titanium freehub bodies, shallower splaines, 8/9/10sp compatible.

    This guy on the other post obviously had some of these alu freehub wheels and couldn't fit a SRAM 10sp cassette - it obviously has the shallower grooves, because presumably a SRAM 10sp freehub has shallow splines.
    - like your Planet-X hubs ?

    So perhaps you should fit a SRAM 10sp cassette rather than a Shimano one.
  • andrew_s
    andrew_s Posts: 2,511
    JRAB wrote:
    I have to say, I think this is more an issue of poor engineering on the cassette rather than the freehub. The middle sprockets are the ones that get most use, so what does Shimano do? Make them individual sprockets so all the load goes through just the tabs on that one sprocket, rather than sharing it along a whole carrier like the largest and smallest sprockets.

    Shimano's cassettes work fine on Shimano freehubs - no engineering problem at all.
    They even offer cassettes that are on carriers rather than loose sprockets - they just cost more.

    If Planet-X want to make their freehubs out of cheese, it's their problem. They can't expect Shimano to make better (=more expensive) cassettes especially for them.
    Maybe you should complain to Planet-X that they should have specified that you could only use Dura-ace cassettes?