Bio pace in 1990?

[LesterOfPuppets]

I always replaced little rings on BP triples with round ones. Mid and Big ring BioPace are AOK with me, though.

 

[ishaw]

Why does rotating the rings make any difference - its oval at the same amount of points through a revolution isn't it?

If anyone wants a lovely set of silver XT biopace outer and middle rings, I've got a set going spare.

 

[thecannibal]

Why does rotating the rings make any difference - its oval at the same amount of points through a revolution isn't it?

If anyone wants a lovely set of silver XT biopace outer and middle rings, I've got a set going spare.

Huh? If you rotate the ring the gear will be taller/lower at different points.

 

[Neil]

Having missed out on the original Biopace craze I rode my first ovalised chainringed bike last year. I find it very similar to regular round rings. The only noticable difference is when using the smallest chainring, things get a bit choppy. I like it.

(raises hand in tentative manner)

"Hi, my name's Cornelius and I like biopace..."

 

[Acei]

I've done about 15k miles on my bike with Biopace over the years and never had knee problems. Fibromyalgia means I have problems almost everywhere else, but my knees are fine

I find the oval effect most noticable when using the smallest ring. Other than that, I don't notice it, but that could be because I'm used to it.

It is possible that the Biopace on my Applachian is the later model and isn't as oval as previous versions. Perhaps someone could confirm. It's the Deore II groupset.

 

[thecannibal]

As I understand it, the problem with biopace is that load is increased as you knees are at their weakest position (top/bottom dead centre, so extremes of bent/straight). I've heard quite a few negative reports and also experienced knee pain with it myself, though I only tried it briefly. Of course results may vary...

 

[ishaw]

Huh? If you rotate the ring the gear will be taller/lower at different points.

Different points to what? I understand that relative to the crank arms the points it is oval will be different. My question is, why does this make any difference?

 

[thecannibal]

Huh? If you rotate the ring the gear will be taller/lower at different points.

Different points to what? I understand that relative to the crank arms the points it is oval will be different. My question is, why does this make any difference?

Different points during the pedal stroke...Different points to those points at which things were previously occurring......errr...The gear becomes taller/lower at different points during the pedal stroke.

Any of those grab you?

Edit: http://en.wikipedia.org/wiki/Gear_inches

 

[ishaw]

Thanks but it doesn't mean an awful lot to me I'm afraid.

 

[thecannibal]

Right, so bigger chainring = higher gear

biopace ring = effectively goes big-small-big-small as it rotates

rotating ring so 'bigger' bits are at different places in relation to crank arms = higher/lower gear at different phases of crank rotation to the original, shimano-ordained ring position