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Question on rear wheel “disengaging”

JacksyeeJacksyee Posts: 48
edited August 2019 in Road general
Hi, I will be taking the bike to the LBS but I’d like to describe something that happened to me last week and see if I can educate myself on what is happening.

I was 160km into a 180km bike ride. I was going up a hill and was in the the second to easiest cog. I shifted to lowest (28t) cog and all of a sudden as I pedaled there was no resistance, the pedals moved in a normal pattern but “freely”. The chain was on the cog and on the chainring (chain did not slip)

I shifted the front ring and it “reengaged”. I then shifted the front ring back down to the small ring and it worked ok.

I found later as I shifted I would sometimes duplicate this effect, I could always recover by shifting into a harder gear (maybe easier but for sure the harder)

A friend later said it had to do with the wheel hub and I was lucky it didn’t completely break.

The wheel was a Zipp 454, Cannondale SiSIl2 cranks.

I can provide more bike details if relevant. Just curious if anyone has seen this and what they think it might be. I fly back today and am killing time at the airport

Posts

  • shortfallshortfall Posts: 3,287
    Something similar happened to a rear wheel of mine a few years ago although it was accompanied by an awful noise and felt very much like a slipping chain. It turned out to be a weak pawl spring that wasn't allowing the pawls to engage properly which subsequently damaged the teeth of the ratchet ring. The slipping was intermittent and unsurprisingly was limited to very hard efforts, usually on steep climbs.
  • JacksyeeJacksyee Posts: 48
    Sounds really similar without the noise!

    It was scary and of course the first instance was accompanied by mean standing on the pedals to pass someone, a lurch, a girly screamy noise, and a wtf. Not stylish at all.
  • whyamiherewhyamihere Posts: 7,519
    Definitely the freehub mechanism. A quick Google suggests the 454s use a weird magnetic clutch arrangement to disengage the drive when you stop pedalling. I think it needs taking to a mechanic with some experience with that type of hub.
  • Probably needs replacing with a more reliable hub design!
  • JacksyeeJacksyee Posts: 48
    Thanks everyone
  • First.AspectFirst.Aspect Posts: 7,642
    Get some pipe insulation from b&q and put it on your top tube. Then when it happens again, no harm done.
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