DXchulo

I bought a crank off of eBay a while back and the chainring is in the shape of an oval, not a circle. It's a 105 crank with Biopace 52 and 42 chainrings. What would one have to do to bend a crank like that?

So I was thinking about just getting new rings and then one of the chainring bolts was stuck and now, since I'm an idiot, is stripped. How can I get this damn thing off? All of the others were fine.

I'm assuming the bent rings are just trash. Is that right? I'm just trying to salvage the arms and the BB at this point.

mtbikerinpa

I fail to see what the question is. Shimano's BioPace and SunTour's Ovaltech are designed to be eliptical to smooth out the pedaling forces. They usually feel good once you adapt to them. As long as the ring is eliptical in diameter and is still true laterally then it is in it's design parameters. If you don't want them I do.

dbg

You can likely drill out the stripped bolt. Regular round chainrings will fit fine on those crank arms. And you need to google "biopace" to understand why they were purposely not round in the first place. Some people love them. I plan to try them out someday myself.

DXchulo

So these are supposed to look like ovals? I thought something was wrong with them. Boy do I feel stupid.

Sounds kind of interesting...maybe I'll try them out.

Berodesign

www.sheldonbrown.com look at Biopace in his glossary

Avalanche325

Ovals. That is what Biopace is. It is one of those things that worked great on paper, but not in the real world.

mtbikerinpa

It worked well within its design parameters. It is a non-SPD and 70-90 rpm system. Too high rpm not good, pedaling circles is awkward as well.

sydney

And what does that mean.

mtbikerinpa

Here we go again...
THe reference means it was designed for compression based pedaling as opposed to the modern clipless generation push-pull pedaling styles. I have used them clipped, strapped and flat and they are distinctly suited for flats and straps but not so well for clipped.

bostontrevor

Sydney aside, I'm curious how power development differs between clips and clipless systems. Flat out block pedals seem to be obviously different, but foot retension systems seem like they would deliver power in pretty similar ways. Biopace would have been designed with clips in mind.

sydney

I ain't buyin it. And what's the diff between clipped and strapped when it comes to your so called push pull pedaling stye ?

sydney

Try reading what Sheldon Brown has to say about it.

dbg

a quote from Sheldon's page: "The problem is that Biopace rings are more comfortable at low RPM's, and round rings at high RPM's."

But then he runs biopace on a fixed gear -- so what does he know..

mtbikerinpa

I have and I agree with him to an extent. The systems I have used personally were better off with round for high cadence and very comfortable in load and climb with the ovals. The article has been around for a long time(I have watched his site for several years), and I have put several hundred miles on a few ring sizes and variations, (Biopace and Ovaltech). Agreed, a good strap set is on par almost with clipless, but the average person's set is rarely that well tensioned.

dbg

THat's my perception as well. I consider straps that are tightened to be as rigid as clipless ..to be almost dangerous. I use straps on my commuter and tourers not to be like clipless. I keep them loose on purpose. I just mash on those bikes and expect the straps keep my feet from slipping off the pedals as I go quickly from sitting to standing...

sydney

And fixed can't be high cadence? The quote is from mixing biopace and regluar rings. Methinks it pays to read and think thru the whole article.Then decide if any of it work or doesn't work for you , in actual practice , rather than theory .

Phatman

did you not get your coffee this morning sydney, or is it just that time of month again? a fixed gear can be a high-cadence application, and I beleive the poster that you quote was suggesting that it was slightly reduculus to put a biopace on the fixed gear due to the range of cadences, from very low to very high. I think thats why he wrote "so what does he know"

sydney

Maybe you should read the whole article too........?

Dutchy

I wouldn’t say you were stupid, as someone has clearly misled you by not mentioning they were Biopace. The seller would have known, and has obviously tried to offload them through e-bay. If possible, I would send them back.

CHEERS.

Mark

sydney

Maybe the seller was an ingoramus too.There are alot of them on ebay..... EDIT ...There was no intent to dispararage the initial poster. This would have read better if there had just been a period after ingoramus(ignoramus ).

gruppo

sydney, did you mean 'ignoramus'? If so, some would argue there are also many on "Forums', though maybe it's kinder to just say there's a multitude of beginners trying to achieve amateur status. Now I don't know who Sheldon Brown is, and I don't really care. The fact is, oval rings - whether Shimano, Suntour, or what ever - are, thank goodness, ancient history. In my experience, no one, including me, had their cycling experience improved by oval chainrings (And I'm talking road, 'cross, fixed gear/track, mountain, touring, going-to-the-coffee-shop, etc., bikes). In this case the best response would've been no response, and DXchulo would have just trash-canned his "eBay bargain".

Berodesign

Some people thought it was a fact that afro-americans were lesser beeings then white americans, for quite a long time also... was that true? No. Dont state a "fact" unless it is a fact and not just an opinion.

Look up who Sheldon Brown is before you just dismiss his opinions. But of course, you seem to know everything already so why bother about other people. Your entire post stinks ignorance.

Rowan

Oooooh... the pack of dogs are closing in again sydney...

You know, there are idiots who post on these forums. Some admit they are. Like DXchulo. That truly, truly is a compliment. Good on you for that, DX. You have moved yourself from ignorance to education about an area of cycling that interests you.

There are others who think they are educated, but in fact deal with witchcraft, rumour and innuendo. And when they are wrong, they require a degree of prodding and public exposure to admit it.

Often, the least of their concerns is practical application of knowledge. They dive for the theories, the numbers and the reasons why things CAN'T be. I usually find these people are young (let's say, younger than 45 as a starting point). The trouble is, they know so much, they should write it down, because the older they get, the more they are going to forget.

Then there are others who have been there, done that. They cut through the rubbish. They give it to you straight. You either like 'em... or you can go somewhere else where the information is guilded and makes you feel good, and you can get easily misled.

Which brings us back to DX... maybe he was misled on his purchase. It could be argued he was misled further here.

Do I know anything?

Of course not! But Mr Brown doesn't diss Biopace rings. He has a logical explanation for why they work well, and failed in the marketplace. It's proof that Shimano does listen to its market -- or at least the witch doctors.

I know I have a 38T Biopace ring on my FIXED gear (shock horror, it can't be done they tell me!!!!). And you know, I think, but I haven't checked yet, that the long radius is not aligned on the crank properly. My bad. And it's probably why I can't quite get 130rpm on the pedals with my Time Atac clipless pedals doing 53km downhill just yet. And I've had experience with Biopace rings on previous bikes -- not that I would know if they were effective because I was just starting out.

Now, anyone want to lay bets on the whether the pit-bull is going to win the fight?

Juha

I agree with this to a point. I have yet to see a Forum member that has omnipotent knowledge on all aspects of cycling. Some admit it, some do not. I think the true idiots are those who do not.

--J

sydney

Maybe you ought to get acquainted with Sheldon Brown. AFWIW, regardless of your negative experience with biopace,there are many that like them,and I could easily sell the whole box full I have for good mone Only an ingoramus below beginner level would trash can something valuable and and then go merrily in his/her way with a warm fuzzie about it....... My comment about ignoramus was not directed in any way at the initial poster.