Bacchetta Giro 26/20 chain idler

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Juan Tumani
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2021/03/07 17:47:45 (permalink)

Bacchetta Giro 26/20 chain idler

I have an early 2000s Bacchetta Giro 26/20 and have been hearing (and feeling through my feet) a nasty metal on metal screech when climbing steep hills. I'm not seeing any interference/contact with the front sprocket or front derailleur. I put it on the mag trainer and cranked up the resistance as far as I could and still turn the crank with my legs in the lowest gear, but have not been able to duplicate the problem. I think it's very likely the chain idler wheel, though, because it doesn't turn very freely by hand and the chain has worn deep grooves in the rubber part of the wheel. I know I have replaced this part before, but I think that was because it just fell apart. I don't remember any screeching the last time, but then my memory's kind of a sieve.

Anyway.... I think I should just go ahead and replace the dang idler wheel again, but when I looked for the part on the Bacchetta web site, the only one I found is a much larger diameter than the one that's on there now. I tried contacting Bacchetta via their website contact form a few weeks ago, but haven't heard back from them. So, I'm hoping someone who's in the know on this will tell me whether or not the newer, wider idler (wow, try saying that real fast a few times!) is the correct replacement part for my older, narrower one. Any thoughts, stories, etc. about diagnosing nasty squealy, screechy sounds in recumbent drive trains that anybody feels like sharing would be welcome as well.
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    JimM
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    Re: Bacchetta Giro 26/20 chain idler 2021/04/27 22:04:41 (permalink)
    One issue with many idlers is that they are designed to allow horizontal movement so as to follow the chain(s) as you shift. This means that it can be just as easy for the idler to spin on its post as it is to turn its bearing. That is, the inner race that slips over the post will spin on the post instead of remaining static. The bearing seals make this worse, because although they have inconsequential dynamic friction, they have enough stiction to cause the inner race to spin on the post instead of holding stable. The obvious fix would be for the post to be octagonal, but that would require an additional part to be added to the inner race, as I know of no bearings with an octagonal mounting hole. I haven't found a good solution to this. I lube the post so that if the bearing spins on it, it will have very low friction. I would very much prefer a design that did not use a center idler.
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