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Weird rubbing noise

Rhod81Rhod81 Posts: 116
edited November 2015 in Workshop
Hi all, could anyone please shed some light into this, 'cause I'm completely stumped!

Just been out on a hilly 70-miler and the bike seemed to be performing perfectly normal. However, halfway round, I started going down a big hill. As soon as I hit 30mph there was a sudden abrasive, rubbing noise. I thought at first somehow my brake blocks had slipped and were rubbing the tyre, but that wasn't it...

Upon closer inspection, there didn't seem to be anything dodgy. Everything looked completely normal.

I continued on thinking nothing of it, but yet again, I hit 30 and it happened...

In the last 30-odd miles I must have stopped 12 times, each time thinking there must be some evidence of rubbing, but there is nothing. Almost 100% of the time, it only occurs going downhill at speeds of 28mph-plus. On the flat, no problems, even cranking it up to 27mph there was nothing.

There was one occasion is happened when I swerved round a pot hole at 23mph, and there were two brief occurrences at about 15mph as I was approaching a junction.

It happens whether I'm pedalling or freewheeling.
It happens in both small and big chainrings
The rubbing/vibration seems to originate from the rear
Glancing down when it happens the chain seems to have flopped over the chain stay
I tried slackening off the brakes thinking they may be rubbing - no difference
I undid the QR skewer, checking for tightness - seems fine.
Only happened after 30+ miles. Before that I hit over 30 several times and 44 on one occasion.

The bike is a Ribble Gran Fondo with Mavic cosmic S and campag athena. It's 6 months old and has done roughly 2,500 miles. Nothing's changed other than some 25mm conti gator skins which have been on for a couple of months. Gearing probably needs a bit of a tweak, but works fine.

Any help greatly appreciated.

Posts

  • AnonymousAnonymous Posts: 79,678
    If its speed related I would suggest its most likely to be a hub bearing. Regardless of whatever else is moving or not i.e pedals or chain this is the one thing that is constant in all circumstances

    Have you any other wheels you can try to eliminate the possibility?
  • pirniepirnie Posts: 242
    Glancing down when it happens the chain seems to have flopped over the chain stay


    I know you said it happens when both peddling and freewheeling, but this sounds like the freehub dragging at speed to me and making the chain go slack (the mavic campag ones are a bit prone to it).

    When was the last time you gave the freehub internals a clean?
  • Rhod81Rhod81 Posts: 116
    Cheers guys, thanks for your ideas.

    Got the bike booked in at the LBS tomorrow so we shall see.

    As bad as it may be, I have not had the thing serviced, so I guess it's my own fault. Not very mechanically minded and I only have the basic tools (and knowledge) for maintenance! Guess because the bike has worked so faultlessly and there's nothing visual I carry on regardless :? :roll: :(
  • keef66keef66 Posts: 13,123
    Cheers guys, thanks for your ideas.

    Got the bike booked in at the LBS tomorrow so we shall see.

    As bad as it may be, I have not had the thing serviced, so I guess it's my own fault. Not very mechanically minded and I only have the basic tools (and knowledge) for maintenance! Guess because the bike has worked so faultlessly and there's nothing visual I carry on regardless :? :roll: :(

    If it's any consolation you are not alone; Google Mavic Death Squeal. The freehub employs a plastic bushing that either needs lubrication or possibly replacement. Mavic annoyingly don't sell the bushing, you have to buy an entire freehub. I understand somebody else is making / selling the requisite part though, so question the bike shop if they are wanting to replace the whole thing.

    Daft design really. Shimano freehubs seem to be less needy; they can go years without any attention (though I take mine off annually for a precautionary pre-winter lube).
  • Rhod81Rhod81 Posts: 116
    Well guys, sorry, I meant to reply sooner but haven't got round to it...

    Got it sorted.

    It was the spokes!

    LBS got two full turns out of each nipple. Bizarre (and pretty unsettling!), 'cause as I said, earlier in that particular ride I hit some fairly quick speeds. They fitted new bearings, gave everything a greasing and I took it out following day, 45 miles, usual perfect bike again :-D

    Thanks for everyone's input 8)
  • It wasn't the spokes.....
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