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Another strange one - Stronglight 
PostPosted: Wed Sep 15, 2010 11:41 am Reply with quote
scozim
Joined: 26 Sep 2008
Posts: 629
Location: Ellensburg, WA
I was in the LBS today looking for some smaller rings for the bike I'm setting up as a touring rig and in the used box of parts pulled out a Stronglight 390 crankset. The cranks themselves are nothing that spectacular and they're 170 mm which is what I use.

http://tinyurl.com/2bhlrhv

But attached to the arms were some oblong (aka biopace style) rings that had a 48-48t count. The inner one said Stronglight on it. I wasn't aware that Stronglight made these oblong chainrings. Does anyone have some info on them? Velobase is lacking for this style.

"Unfortunately" I'm going to have to go back and buy the crankset from the shop owner - just too intriguing.

Scott

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PostPosted: Wed Sep 15, 2010 5:48 pm Reply with quote
scozim
Joined: 26 Sep 2008
Posts: 629
Location: Ellensburg, WA
Went back and bought the crankset tonight while waiting for an emergency wheel true (after jumping the pannier off the rack and into the rear wheel on a parking lot entrance).

The crank arms are well worn and will need some polish and light sanding to get a lot of the scratches/scuffs out.



Here are the rings - called Bio Strong. The cranks can be run as a triple or double with a 110/74 bcd. There was no middle ring but the 48 and 28 Bio Strong rings. Gotta be from the 80's.



[/img]

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1984 Gitane Sprint
1984 Gitane Tour de France
mid-1970's Gitane Olympic
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http://eburgcycling.blogspot.com
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BioPace 
PostPosted: Wed Sep 15, 2010 8:35 pm Reply with quote
verktyg
Joined: 14 Jan 2007
Posts: 2814
Location: SF Bay Area
Scott,

Shimano introduced their highly controversial Biopace elliptical type chainrings around 1983. They put a lot of effort into marketing Biopace especially on bikes with all Shimano components. Biopace faded away in 1992.

Many other crank manufacturers offered some elliptical type chainrings in the late 80s to try to get a piece of the Biopace action. Campagnolo and maybe T.A. where a few of the exceptions that didn't buy into it.

I'd heard that Stronglight made some elliptical type chainrings but I'd never seen them before. Those chainrings have a very aggressive elliptical design.

Shimano had 3+ versions of their Biopace design chainrings: original with a highly elliptical design, Biopace II, Biopace III and Biopace HP. The later versions had a very small amount of ellipse in the chainring design.

Sheldon Brown wrote a good article on elliptical chainrings.

http://www.sheldonbrown.com/biopace.html

I have Shimano Deore XT Biopace III triples on both my MTBs plus a set of them on one of my road bikes that I built for climbing.

It's hard to notice much difference offroad on the MTBs but for me the Biopace III triple chainrings make a noticeable difference when climbing on a road bike.

I've read that it's not a good idea to mix elliptical and round chainrings.

Shimano Biopace chainrings should fit on those Stronglight 309 cranks. You can also get round 110mm and 74mm BCD chainrings from a lot of manufacturers.

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SF Bay Area, CA USA
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PostPosted: Wed Sep 15, 2010 11:36 pm Reply with quote
Gtane
Joined: 14 Sep 2007
Posts: 681
Location: UK
Scott,

Elliptical chainrings have been making appearances again in the Pro ranks such as O.symetric and Rotor.

Here are a few shots plus further info:

http://tinyurl.com/39h93j2

http://tinyurl.com/3x2yzmg

http://tinyurl.com/3xft582

http://tinyurl.com/24hnhbk

http://tinyurl.com/2urgwmt

http://tinyurl.com/33k7bqo


I remember Biopace rings very well indeed but have not tried them out.

Enjoy using the new find.

Tim

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PostPosted: Thu Sep 16, 2010 3:31 am Reply with quote
trailrunner
Joined: 21 Jul 2010
Posts: 20
Location: Fort Worth, TX
The sheldonbrown write up is very interesting - how there have been changes as to what point of the pedal stroke aligns with the higher or lower ratio. And it's effect on the knees.

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Dave B
Ft Worth, TX
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Another strange one - Stronglight 
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