Eccentric Chainrings

[Fladdem]

Hi,

I've got myself a 1989 Specialized Rockhopper Comp at home with Shimano Deore Biopace Chainrings, these are eccentric rings. The issue is the centre ring has ended up all hooked and gnarled as it appears to be the only one that was ever used.

Is it worthwhile replacing it with another Biopace, keeping it semi-original, or not? I'm not sure what I think about eccentric chainrings yet having spent no time riding it at all, depsite owning it for years. I want to get back into XC riding after dabbling with 4X and dirt jumps and realising it's not really my thing, I wanted to dig out the Specialized and start using that instead of my 1992 DiamondBack Topanga which has evolved into a bit of a hybrid/hack rat/survivalist bike now and less of the XC MTB it once was.

I like my retro bikes so I'm thinking that I might enjoy leaving it as close to original spec as possible, but it will be easier in the future if it's converted to normal, round chainrings, I would guess.

Thanks!
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Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

[Pjay]

I always replaced the fkin things, I never got on with them.
I might even have some in the shed if you need one badly.

[G]

Some people advertising them recently on facebook, so they may be making a mini comeback.

No personal experience.

[stinkwheel]

Fashion and fad.

One year they are the best thing since sliced bread. The next year they damage your knees.

If there is any gain to be had, I think it is highly marginal.

Please yourself.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Fladdem]

Went out on it tonight for the first time ever.

I couldn't tell they were spaz-shaped at all, apart from with a really fast cadence, when I started to develop a weird leg movement, hard to describe really.

It needs at least a new centre chain ring, but if I replaced that with a normal, I'd have to replace all three just because it would drive me nuts. Currently it would be cheaper to put another Biopace on it.

It needs a bit more tinkering, it sounds a bit cranky when applying pressure to the pedals, no noise when just spinning it round on the stand with no load. I need to set all the controls and that up as well.

Probably my favourite bike at the moment.
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Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

[Irezumi aka Reuben]

Biopace is/will be going in to collector territory now. Biopace wasnt particularly good.

Rotor Q-rings are the new version (for road bikes at least) most notably used by Brdley Wiggins, but not many others.

I'd say a novelty thing to have, chuck it on a collectors bike and put to one side or flog it for more than it's really worth.
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Pictorgraphicalfantastical

[TbirdX]

I've got a rockhopper with biopace too. Can't say i've ever taken any notice of it or noticed anything different in the way it rides.

Maybe if you're a top athlete chasing .0001 second it might make some difference. To the forest trail plodder, nahhhhhhhh.
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VFR800X - TTR250