23 April 2010 - 8:18Something’s not Quite Round Here…
I had someone ask me the other day what was wrong with the chainring on Mr. Furley. See, I switched it from the sexy Boone Ti 32 tooth ring to something a little different. It was a gift from Mr Dejay Birtch. Another Fuzzy person told me that with this magical chainring I could go up a tooth in the front, and down one in the back, but it would still “feel” the same at the pedals. This means I can go from 32-20 to 33-19. What do these numbers mean? Well, 32-20 has a development of 145″, meaning for every revolution of the cranks (on level ground, perfect weather, no Stormtroopers etc), I travel a little over 12 feet. 33-19 has a development of 157″, which is over a foot more. See where this is going?
The new voodoo ring is none other than a Rotor. Notice how the chainring is not round. This is where the majick happens.
The shape of this ring is designed to keep your power on while you are in the transitional part of your pedal stroke, ie the “dead” spot, or, that split second before someone with good form goes from pulling to pushing on the pedals. The shape of the ring acts like a cam of sorts, with the teeth engaging the most amount of chain during the transition zone, thus keeping the power flowing to the rear wheel.
Poppycock you say? Hogwash? BS?
Well, I have become a believer. I’ve been riding this ring for a couple of weeks, and have been lucky enough to do some actual mountain bike riding to test this newfangled technology out. It works. I definitely feel the constant power at the pedals, almost like riding a fixie. It took me a while a while to get used to the feeling, as a single speed rider you sort of get accustomed to that dead spot and plan accordingly. I’m also feeling the extra gear, Fuzzy tricked me! But I have to say that in low speed super tech sections that require moves with pedal power, I was able to clean sections that would have otherwise stymied me, some of it was having a big assed gear, but a lot of it was having power no matter where my crank arms are.
Now wait, what’s this? Oval chainrings have been done before?
taken in my shop on a circa 198? Cannondale
True, but not like the Rotor ring. Some of you will remember Bio-Pace. This is not the same thing. The offset of the ring is almost the exact opposite of the Rotor, designed to pull the least amount of teeth so that the chain could shift from one chainring to the next. This was back in the days when dinosaurs ruled the earth, and there were no shift gates, or profiled chainrings, or other such technological marvels that increased shifting performance.
The Rotor thing is awesome, and I’ll be trying it out at Single-speed-apalooza in downstate NY this weekend. I’ll have a full report on the performance of this device next week. I’m also seriously considering running the new Michelin tires for the race, but I may switch out to the WTB Nanoraptor, still trying to figure that one out. Either way, there will be some good reading next week, when I will try to regain a normal posting schedule.
Have a great weekend and go RIDE!
6 Comments » | Tags: 29er Components, singlespeed
23 Apr 2010 - 9:09
do you have to run a little slack in the chain when singlespeeding to make up for the “long” end of the chainring?
or do you use a tensioner?
23 Apr 2010 - 9:14
If the chain ring is not perfectly round how does the chain stay in proper tension on a SS? It seems that the chain would get tight and loose depending on where you are in your pedal stroke, like having your chain ring adjusted incorrectly.
If not, it is a magical voodoo chain ring.
23 Apr 2010 - 9:29
Where could one get one of these Rotor chainrings. I’ve been reading the about this phenomenon for some time, but have been unable to locate the chainrings anywhere.
Thanks, keep on bloggin. and ridin
23 Apr 2010 - 9:53
To address the chain tension thin, yes, there is a little bit of slack when the cranks are level. You set the tension when the chainring is at ti’s tallest. The difference is actually pretty small.
25 Apr 2010 - 8:44
The fact that Rotor is now making 104bcd chainrings is news to me.
Thanks, I might have to try this silliness. $93 chainrings though, yikes!
Sheldon Brown on the chain-tension issue:
“People are often astonished to learn that I ride Biopace chainrings on fixed-gear bikes. They imagine that there will be tremendous changes in chain tension as the chainring rotates. In practice, this is not the case. A 42 tooth chainring will generally engage 21 teeth against 21 chain rollers, regardless of its shape.
There is a slight variation in tension resulting from the varying angle between the two straight runs of chain as the axis of the chainring rotates, but this has not generally been of a sufficient magnitude to cause any problem in practice for me.”
28 Apr 2010 - 20:14
very interesting indeed. I could use some “free” speed right about now.