Dec 15, 2003 6:56 PM
|I just picked up this 89-90 Trek and it has these egg-shaped crank rings marked Biopace. It is part of a 105 group. Anybody have any experience with these? I think that the best thing would be to scrap them and just install a regular 105 crank and rings.|
|Yeah, I still ride 'em||Mel Erickson|
Dec 15, 2003 7:08 PM
|On my commuter. They were Shimanos answer to an unasked question. Supposed to try and take advantage of the power part of the stroke but all they did was ruin your ability to spin. To be fair I don't really notice them on the commuter. They work, are pretty harmless and depending on what you intend to do with the Trek (winter beater, commuter, etc.) I'd just leave them on.|
Dec 15, 2003 8:30 PM
|I had a set on a bike for while and honestly could not tell them apart from round rings. Give them a try and see if you like them or not. If you don't you can buy round replacement rings.|
|What's your average cadence?||russw19|
Dec 16, 2003 1:52 AM
|If you ride at a very low cadence, like 60 to 80 rpms they actually work.
Shimano had a computer design these chainrings to try to make your drivetrain more efficient. They were designing the chainring shape to match the ergonomics of the human body, and they were very close to being successful. The one factor that they got wrong was that the computer that designed these chainrings did so based on a number of human models, but it only ever factored in the riders riding at 60 rpms. At that low of a cadence, the body tends to push down on the pedals but not pull up so much. The problem came when riders who pedal higher cadences got hold of these chainrings. If you are taught to spin circles on the bike, these feel really odd. What eventually killed them was that they couldn't get anyone who bought a high end bike to ride them becuase even if they didn't pedal faster than 100 rpms, no pro riders would touch them.
But if you ride with a lower cadence, these chainrings are fine. Pedal above 100 rpms and they aren't as smooth.
|russw19 - is there anything about bikes he doesn't know!||innergel|
Dec 16, 2003 12:14 PM
|I've been reading this board for months and everytime there is a question having anything to do with component, no matter how old or obscure, russ seems to know the answer.
Either that, or he's BS-ing us REALLY well :-)
Thanks for you consistently well thought out replies. Keep 'em coming.
|I don't answer every question...sometimes I don't know answers..||russw19|
Dec 16, 2003 3:28 PM
|Thanks, but there are some people here who know a heck of a lot more than me. C40, Rusty Cogs, Kerry Irons, TJeanloz... those guys know as much if not more than me. I just have one of those brains that picks up and stores otherwise useless trivia. And the whole Bio-Pace-60rpm thing was Shimano's Corporate excuse as to why it failed. That was the explaination they tried telling to all the shops at that time so that people still bought into what they were putting out. Remember at that time, they weren't the king yet, they were still second to Campy and some of their innovations weren't looked upon too kindly. They had to spit out some line about Bio-Pace in order to sell the public on thier next big idea. Hyperglide, STI, Rapidfire...etc.
|What's your average cadence?||MShaw|
Dec 16, 2003 1:42 PM
|60rpm: THAT explains why I never noticed the biopace feel in my granny ring on my first mtn bike. The other two rings felt strange, but that granny didn't.
...and now I know why.
|average cadence?||HENRY K|
Dec 16, 2003 3:55 PM
|A comfortable cadence for me is about 90. I don't know if that's considered high or low.|
Dec 16, 2003 4:13 PM
|It's normal. It's perfect for an average rider... slightly slow for someone racing, but for JRA, it's perfect.
|Shimano acutally had data showing a 3% improvement||Kerry Irons|
Dec 16, 2003 6:06 PM
|IIRC it was a 3% improvement in efficiency or delivered power, but as Russ19 notes, it was at low cadence, and it was on flat ground. People quickly figured out that there was a disadvantage for experienced cyclists who could spin and for climbing. Remember that non-round chainrings were patented in the late 1800s, so there had been MANY attempts at this concept before and they never stuck. Shimano claimed to have invented a better mousetrap, but it was a dead giveaway when BioPace HP (high performance) came out and it was ROUNDER than the original BioPace. You didn't have to be Kreshkin to figure out where this was headed. Plus you had guys selling "RoundTech" chainrings to replace your BioPace - partly as a joke but partly to solve the BioPace bob. BP was a triumph of marketing over common sense.|
|Yes, not only that....||NEIL|
Dec 19, 2003 7:43 AM
|they were just plain silly looking. I had them on one bike back in the day, and remember feeling like a goof on the training rides.|| |