Experiences with Biopace
 

I'm looking at buying an old bike with biopace chainrings. I've done a little bit of investigation and found some quite disparate opinions. My initial siding, as it is with most things that diverge from the basic simplicity of a straight road bike, was "pah! stupid! won't be having any of that!". But the bike is really nice (and I can always change them out later) and I read Sheldon's comments on them which is a pretty big selling point!, so I'm a bit undecided on them.

I'm sure they're wonderful for going up hill, as it seems like it alleviates that 1-2 grind once you're really stuck into the climb, but I'm mostly actually worried about losing that definitive 1-2 motion of pedaling, especially in standing up and throwing yourself into the pedals as that's when you want to harvest the utmost power from the downstroke and don't want to worry yourself with what's happening in between. And it seems as though with the biopace shape, you'll spend relatively longer in the 'inbetween' phase as the pedals spin slower.

Could I get some biopace feedback? Would be much appreciated! Particularly: climbing, standing & sprinting, and maybe acceleration (from stop /or general).

Many thanks!

I have a biopace crankset and compared to normal chainrings I have not noticed any disadvantage or advantage or difference, my crankset has one biopace chainring and one normal chainring and I can't notice the difference between them when cycling. I just like them for the novelty, I don't go looking for biopace specifically but I will buy it.

There must have been some sort of advantage to biopace because some pro racers are relooking at those especially time trial racers. Anyway you can read all about this here: http://sheldonbrown.com/biopace.html

I have a couple of bikes with biopace gearing...hmmm, not sure if I notice a whole lot! They do seem to climb better? maybe my imagination? maybe not? Anyway read that site I gave.

Yes, Shimano wanted to exaggerate the up-down pumping motion to make cycling feel more like walking. Their rings causes the feet to move faster thorough the down/up-stroke phase and slow down during the transitions across the top & bottom.

As you can imagine, this made for even more bouncing on the seat than normal for the low spinning gears you want to use. I tested by recording the sounds of my tyres on rollers. The regular whump-whump sounds became even more lob-sided and balancing on the rollers became more difficult with the BioPace rings.

I then tested different orientations and found that rotating them forward 144-degrees canceled out the natural uneven pedal-stroke (due to different strength muscle-groups at various crank-rotations). This is the opposite of the Shimano idea with slowing down the feet through the down/up-stroke and speeding them through the transition at the top & bottom. With the rotated BioPace rings, the roller sounds became a more steady whhhirrrrr. Seems this would be more efficient to place the larger-radius and bigger gear-ratio at the point when the legs generate the most force; on the downstroke. Decades later, many pros actually created their own ovoid chainrings with this anti-BioPace orientation.

Some variation of non round chainring pops up about every 20 or 30 years. They always go away. There's a reason. I think they probably initially feel good because they are different. Once the novelty wears off, they don't do anything to help a rider with an efficient pedal stroke.

edotomato, There is every opinion from great to grizzly. If all else on this bike is good for you, buy it. The chain rings can be swapped if you wish to. The build project I have at the moment has Biopace chain rings. I've rode Biopace in the past with no positive or negative impressions. This build will be a nice, long test.

Brad

I seem to feel the slowing down at the top of the stroke helps me with my bad knee.
Problem is, I can't find an inexpensive set with 165mm arms which helps my bad knee much more.
At this point, I've put identical inexpensive cranks & pedals on both my bikes (with cassettes to match the rings & bikes). Doubt I could even find Biopace with 22-32-3X rings.

Biopace came with the mountain bike I bought in 1989. I do not notice any advantage or disadvantage in climbing, standing, sprinting or acceleration. I think it is very well made componentry, so there is no justification for removing it. I can't think of any good reason for avoiding it either.

Wow, these were not the responses I expected! Other threads I was browsing got very opinionated, but it seems they could of been 'biopace fanboys'. I like this consensus of almost indifference. I think I'll get the bike and try it out. Thanks guys!

The small chainring is round and the big is biopace, so you can see that biopace isn't actually that non-round.
http://bikeforums.net/attachment.php...hmentid=320548

Chances are, if you didn't know you had it, you may not have even noticed.

You may be over analyzing the issue, just get it and ride. I ride both types and notice very little difference, never thought much about it until I joined BF.

I would echo everything Sheldon Brown said and if your pedalling stroke is uneven or you are bouncing that is due to the rider and bike set up and not the chain rings... I can spin these things like a gerbil on crack and if anything my pedal stroke (which can be a little uneven) smooths right out.

You still spin in circles with Biopace... they can be especially good on hard climbs and where the terrain is sketchy as you can maintain very even power delivery and not spin out

My beef with biiopace, and why I swapped my small ring is that there are no 39t rings. I can't really get along with 42 small rings around here.

Why not a 38.

:)

I've ridden BioPace chain rings since they first came out, and have always liked riding with them; even with a high cadence they worked really well, and my knees weren't as sore on longer rides.

Since I had surgery on both of my knees about five years ago, I feel BioPace allowed me to ease back into riding easier, without suffering any discomfort during and after riding.

My current bike came with them and I had similar trepidation, so I read up on them as well. The consensus I arrived at was to keep them and see how they worked for me. Being 51, and a modest rider of some ability with experience in the past, I understood that they may yield an advantage for me.

So far after 2 weeks of regular riding I do notice that my knees have little to squawk about and that my pedal stroke is subtly different than with my previous bike and standard C/R's. I've yet to hit some climbs to really show me how Biopace can help me, I'm still getting used to being back in the saddle.

I say keep them and give them a chance.

The smaller BioPace rings were more eccentric than the larger ones:

http://bicycleczar.com/images/parts/DSCF0117.jpg

Wow, I never knew the small ones were that non-round, I've been meaning to get a matching 42t biopace chainrings, I wonder if they are as eccentric.

I had, operative word here is had, them on my Giant Iguana; they were ok I thought, until I replaced them with traditional rings...what an improvement. That said I used the bike for paved road and dirt/gravel roads. The rings seemed to work on trails and such but for spinning on improved surfaces, not so much.

The first generation Biopace had a more pronounced shape which is described as an egg shaped curve and not an oval, the second generation Biopace is less egg shaped and less effective at what the system is designed to do.

Installed these yesterday... the 44 and 50 were new in the box while the 28 was a gently used spare.

http://www.ravingbikefiend.com/bikep...cadedrive1.JPG

Need a 46 to get a perfect half step gearing with the 6 speed block.

OP, I would never consider passing on a bike because it has Biopace. If you want the bike, buy it. There are so many options to change out if you don't like Biopace. I have it on my 88 Nishiki Ariel MTB that I use on MUPS. It works fine and I won't replace it. Both my 92 Nishikis do not have it, and I'm not going to add it to them. I could care less if it has Biopace or not.

When I got my Cascade it was a totally stock mountain bike and had a 28/38/48 Biopace on that same Deore crank and I took it out mountain biking with friends, they were stunned that despite not having as low a gear as them (I had a 14-28 freewheel) that I could out climb them on some exceptionally steep off road grades.

Mind you, I used to be a hill climbing machine and used to rock those same climbs on an SS mountain bike... now that I am older and more busted up am appreciating the Biopace more than ever.

I have suggested and fitted Biopace to many customers bicycles when they expressed that they had knee issues and the feedback was that they do reduce a lot of stress... my right leg works harder than my left so I appreciate this too as my right leg works harder than my left and is under more stress and this really helps me keep up a good spin.

I think the group in question must be second gen as the bike is an '88 and they don't look that elliptical.

And here we get to the real heart of the matter!