feethanddooth

friend has a bike thats chainrings are more oblong than circular. my opinion was it is bent but he insists it was made that way to help produce more torque on each pedal revolution. have any of you heard of this? the bike is about 13 years old, a Giant.

urbanknight

Sounds like you're talking about biopace chainrings or special time trial chainrings.

LanceFanBoy

Bobby Julich from Team CSC rides with one, google pics of his bike

shatdow

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

NoRacer

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

https://www.cyclingnews.com/tech.php?...uickspin/12-03

https://www.rotorusa.com/frequentquestions.shtml

mattm

interesting that biopace was like this, then went away.

and now some TT bike setups use the same idea! i just don't like the way it looks personally.

humboldt'sroads

I love hearing people's reactions when they see biopace for the first time..."How the f*** did your chainrings all get bent into such a perfect oval!?!?"

urbanknight

I believe the TT setups have the high points in a different location than the biopace did.

bdcheung

+1.

feethanddooth

well damn i thought it was bent. ill have to buy him coffee tomorrow then. thx evry1

RichinPeoria

there is allot of that junk on ebay cheap...see Sheldon's site for the low-down on it

jsharr

I loved the Biopace rings on my old Trek, buy me a coffee too.

Nickshu

I used to have Biopace chainrings back in 1989. Haven't seen them since. It was hard to get a smooth pedal stroke at higher cadence with them.

redirekib

+1

ThinLine

+1. I had them on an old nishiki with shimano 600. Climbing was terrible.

bdcheung

Try the Q-Rings. I regularly sprint at greater than 130rpm

redspoke

I had a 89 Panasonic DX4000 with full 105 and biopace cranks. That was a great bike. I never noticed any benefit or drawbacks with em'.

White with teal and magenta accents... If Crockett and Tubbs rode bikes, it would have been a perfect matchup.

AEO

really? I was doing 100~110 with biopace rings no problem.

The only problem I had with biopace was that the 600 FD was WAAAAAY the hell up because it didn't match the curve of the rings and kept rubbing at optimal height.

scvroadie

I have a friend that uses the Rotor rings, it eliminates the dead spot for him. When he was a child he had polio, so he is pedaling basically with one leg, his bum leg is along for a ride. When he was a kid, his dad ran a LBS, and he just started riding, now he has been riding for close to 50 years.

This guy is an animal he loves rides with at least 50+ miles and minimum of 6000 ft of climbing. Besides installing the Rotor chain rings last year, he also finally paid for a professional bike fit. Now he is twice the animal he was before.

grolby

I never had much of a problem with pedaling at a high cadence. The only thing that bothered me was accelerating out of a corner out of the saddle. The motion didn't feel as well balanced. When I went to round rings on that bike, I noticed an immediate increase in my comfort and confidence out of turns. Similarly, they're not too great if you climb out of the saddle. Again, since getting round rings for my Univega, I've been out of the saddle on hills a lot more. The trade-off is that Biopace rings are definitely better if you are climbing seated, IMO. I get out of the saddle more with the round rings in part because a gear that I could push while seated with Biopace will now cause me to start to bog down. The lower effective gear on the downstroke really is great for seated climbing! Given that Sheldon Brown wasn't a racing cyclist and by his own words never got out of the saddle if he could help it, it makes perfect sense to me that he liked them so much. I would strongly consider using my old Biopace rings if I were to build a fixed-gear bicycle for myself. The longer you can stay in the saddle on a hill, the better off you are, energy-wise.

LifeIsSuffering

Glad to hear about your friend.

Biopace, from what I understand, failed because it placed the most stress when your knees are at their most vulnerable angle. Rotor Q rings address this fault.

Last year, I had to deal with patellar tendinitis in my right knee.

Part of the recovery involved the use of Rotor Q rings. And, yes, they did provide some relief.

However, I prefer to address the original cause of the problem. I dislike the band-aid mentality. My solution involved: 1) vastus medialis strengthening to help the knee track properly; 2) strengthen the hip flexors, hamstrings, adductors, abductors; 3) working towards a perfect pedal stroke; 4) stretch regularly.

As my pedal stroke improved, I noticed an interesting result. The Rotor rings made it feel as if I was going over a small bump every time. I experimented with different settings but the awkwardness never went away.

And on a strictly pragmatic note, the Rotor rings never up/down shifted as crisply as my Dura Ace (yes, I know how to wrench).

Because I worked - and still do - so diligently on improving hip flexor and hamstring power, I'm no longer a masher (quad dominant style).

Of course, there are occasions in which I need to stomp - sprinting out of the saddle is a perfect example (if you try to apply circular pressure, your rear wheel can fish tail).

Now, I'm of the opinion that Rotor rings benefit: 1) those with specific physical needs; 2) mashers; 3) a small minority for whom it just feels natural.

An earlier post mentioned sprinting at 130 with his Rotor rings.

A cadence of 160+ with the regular rings is nothing unusual for me. Strengthen the non-glamorous muscles, do over speed drills, and work on a perfect pedal stroke every time you ride.

AEO

Incorrect. It's the other way around. They put the easiest part to the most powerful part and the dead spot is the taller part.

It failed because there was no need for it.

LifeIsSuffering

You misunderstood what I said.

From the Rotor website:

"...Biopace chainrings are designed so that the maximum equivalent tooth size is at the dead-spot. Q-Rings have the minimum equivalent tooth size at the dead-spot which enables you to pass through the dead-spot quicker and with less stress to your knees..."

https://www.rotorcranks.com/frequentquestions.shtml#q1

This is what I meant when I stated "...it placed the most stress when your knees are at their most vulnerable angle. Rotor Q rings address this fault..."

Of course the Biopace became obsolete; who wants a chain ring that makes the pedal stroke less efficient and has a greater risk of injuring the knees.

AEO

and from sheldon: biopace


"The theory is that during the power stroke, when the cranks are more or less horizontal, you are using the power of your legs to accelerate your feet, which get going quite fast in the lower gear provided for that part of the stroke. The momentum of your feet then carries the pedals through the "dead spot" when the cranks are near vertical. Since the rider doesn't push as hard during the power phase of the stroke, and motion is slower when the leg is changing direction, the Biopace design is gentler on the knees than even round chainwheels."

LifeIsSuffering

With all due respect to Sheldon, IF he was right and the Rotor Q people are wrong, it would be the Biopace that's in vogue and the Rotor Q rings that are only available on fleabay.