oval chainring
- Thread starter reinhold
- Start date
castlerobber
Zen MBB Master
There's at least one old thread where we beat the subject of Q-ring orientation all to pieces. There should be a link in there somewhere to Rotor's recumbent-setup instructions.
https://forum.cruzbike.com/threads/q-ring-upgrade-ahhhhhhhhhhhhh.7784/
I have a couple of DFs with Rotor Qrings and they look to have the same orientation as in the picture, which is very different from typical recumbent position oval chainring orientation. It's possible the bike was not raced as shown when the picture was taken.
chicorider
Zen MBB Master
Here's my story:
I had been running Doval chainrings (out of South Korea, no longer available) for years according to the positioning suggestions for recumbents. Then, as an experiment, I mounted a set of Osymetric rings ("If a little bit of ovality--Doval--is good, would a lot of ovality--Osymetric--be better? There's only one way to find out. I also wanted to bump my 50t Doval up to something with 52 teeth). I mounted the Osymetrics the same way that I had been running the Dovals, as suggested for recumbents, and it didn't take me long to decide that this was amiss. Everything, from pedaling to steering, was wobbly and out of whack. My legs were also working harder than they usually did to maintain the speeds I was used to. After a bit of studying and thinking, I shifted the Osymetrics to the standard upright position, and all of those issues went away immediately. My pedal stroke smoothed back out, as did the steering. My legs went back to their usual work load for my typical speeds. Ultimately, I decided that the Osymetrics were not for me (I never could quite get used to them), so I went back to my 50t Doval. This time, however, I mounted it in the standard upright position and quickly discovered that my pedal stroke smoothed out even more, and my speeds increased, both on climbs and flats, with perhaps slightly reduced fatigue. In short, it seemed that I had been running my oval rings incorrectly all those years, which I found to be pretty irritating as I thought about what might have been. All of this was on my V20. I ran the same Dovals on my S30, repositioned them too, and had the same experience--smoother stroke, higher speed, reduced fatigue. Dang it! Well, at least now I know.
Now, this is just one person's experience. Your mileage may vary. But when you consider the positioning of an upright rider, what riding a Cruzbike does is rotate that rider 90 degrees clockwise. But with a CB, everything rotates as a unit around the fulcrum of the hips--the rider, handlebars, cranks, chainstay, drivewheel. What was upright is now laid back, but all of those pieces move together (the rear triangle is now the front triangle), suggesting that the pedal stroke moves with it too, meaning that the positioning of an oval chainring should be the same for both diamond frame and CB designs. Sure, there are subtle difference in muscle use and pedaling dynamics between the two, but not enough to warrant positioning an oval chainring in any way other than what was intended.
Rotor makes some oval rings with a high degree of adjustability, with chainring bolt holes all the way around. If I were using these, I would start by mounting them in the recommended position for upright riders, get used to that feel, make note of speeds and watts (or at least perceived effort), and then rotate the rings by one hole in one direction. That change will be either a little bit better or a little bit worse. If worse, go the other way. If better, ride it for a while, make note of speeds and watts, and then rotate one more hole in the same direction. Keep doing that until you rotate to a hole where things turn that little bit worse. That's the one hole too far, leaving you with the previous two, maybe three holes to choose from for your best position. But again, the process starts at the recommended spot for upright riders.
I am a believer in oval rings for these bikes, and am currently using Absolute Black rings (52/36), mounted in the standard upright position. While shifting up onto the 52t is sometimes a little chunky with my Dura Ace 9000 front derailleur, I like everything else about these rings, from climbing to the flats. My cruising speed is a little higher, I'm finding my way onto new-to-me Strava leaderboards after a pretty long break from that arena, and my fatigue level is no worse for the added speed.
I hope that my trial-and-mostly-error experience helps others.
I had been running Doval chainrings (out of South Korea, no longer available) for years according to the positioning suggestions for recumbents. Then, as an experiment, I mounted a set of Osymetric rings ("If a little bit of ovality--Doval--is good, would a lot of ovality--Osymetric--be better? There's only one way to find out. I also wanted to bump my 50t Doval up to something with 52 teeth). I mounted the Osymetrics the same way that I had been running the Dovals, as suggested for recumbents, and it didn't take me long to decide that this was amiss. Everything, from pedaling to steering, was wobbly and out of whack. My legs were also working harder than they usually did to maintain the speeds I was used to. After a bit of studying and thinking, I shifted the Osymetrics to the standard upright position, and all of those issues went away immediately. My pedal stroke smoothed back out, as did the steering. My legs went back to their usual work load for my typical speeds. Ultimately, I decided that the Osymetrics were not for me (I never could quite get used to them), so I went back to my 50t Doval. This time, however, I mounted it in the standard upright position and quickly discovered that my pedal stroke smoothed out even more, and my speeds increased, both on climbs and flats, with perhaps slightly reduced fatigue. In short, it seemed that I had been running my oval rings incorrectly all those years, which I found to be pretty irritating as I thought about what might have been. All of this was on my V20. I ran the same Dovals on my S30, repositioned them too, and had the same experience--smoother stroke, higher speed, reduced fatigue. Dang it! Well, at least now I know.
Now, this is just one person's experience. Your mileage may vary. But when you consider the positioning of an upright rider, what riding a Cruzbike does is rotate that rider 90 degrees clockwise. But with a CB, everything rotates as a unit around the fulcrum of the hips--the rider, handlebars, cranks, chainstay, drivewheel. What was upright is now laid back, but all of those pieces move together (the rear triangle is now the front triangle), suggesting that the pedal stroke moves with it too, meaning that the positioning of an oval chainring should be the same for both diamond frame and CB designs. Sure, there are subtle difference in muscle use and pedaling dynamics between the two, but not enough to warrant positioning an oval chainring in any way other than what was intended.
Rotor makes some oval rings with a high degree of adjustability, with chainring bolt holes all the way around. If I were using these, I would start by mounting them in the recommended position for upright riders, get used to that feel, make note of speeds and watts (or at least perceived effort), and then rotate the rings by one hole in one direction. That change will be either a little bit better or a little bit worse. If worse, go the other way. If better, ride it for a while, make note of speeds and watts, and then rotate one more hole in the same direction. Keep doing that until you rotate to a hole where things turn that little bit worse. That's the one hole too far, leaving you with the previous two, maybe three holes to choose from for your best position. But again, the process starts at the recommended spot for upright riders.
I am a believer in oval rings for these bikes, and am currently using Absolute Black rings (52/36), mounted in the standard upright position. While shifting up onto the 52t is sometimes a little chunky with my Dura Ace 9000 front derailleur, I like everything else about these rings, from climbing to the flats. My cruising speed is a little higher, I'm finding my way onto new-to-me Strava leaderboards after a pretty long break from that arena, and my fatigue level is no worse for the added speed.
I hope that my trial-and-mostly-error experience helps others.
billyk
Guru
See the discussion at the thread below from 2008, especially John Tolhurst's comment on the first page. (For those who don't know, Tolhurst designed the early Cruzbikes, and was like god around here. The Parkers bought him out around 2015).
https://forum.cruzbike.com/threads/qrings.1781
The gist is that the strongest push is at mid-extension of the leg, calculated to be about 40° past the point where the chain begins to engage the teeth. Looking at the bike from the chain side, this is at about 1 o'clock (where 12 is true vertical, so it depends on the chainstay angle). This is how I set up my qrings, and it feels right to me (but I don't have any powermeters or anything).
@chicorider , does that agree with your experience?
Somewhere in these pages is a detailed set up procedure Tolhurst worked out, but I can't find it now.
billyk
Guru
Also see page 3 of
https://forum.cruzbike.com/threads/q-ring-upgrade-ahhhhhhhhhhhhh.7784/page-3
And maybe elsewhere in that thread, and google
site:https://forum.cruzbike.com/ qrings tolhurst
https://forum.cruzbike.com/threads/q-ring-upgrade-ahhhhhhhhhhhhh.7784/page-3
And maybe elsewhere in that thread, and google
site:https://forum.cruzbike.com/ qrings tolhurst
Andrew Wilson
Guru
I would love to see some updated pics of how people have their Rotor rings set up
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chicorider
Zen MBB Master
trplay
Zen MBB Master
My five hole sram spider will only fit as per photo. I have fit it to different spiders such as a 4 hole Shamino crank. But it goes one way on the SRAM. I do not believe the SRAM spider holes are equal distance. The good news is the alignment looks very close to how Jims are. Now I can adjust the screw on the spacer to different numbers but this doesn't change the ring orientations.
Mathew Fy
GRU
That looks retarded.
In a timing sense, not pejorative. Usually you want the chainring to be at the minimum diameter when the pedals are at Bottom Dead Center. But there may be advantages to have your chainrings delayed . This article suggests doing so if:
“Too Much Resistance at the Top, No Resistance at the Bottom
- When you get towards the bottom of the pedal stroke, it feels like you have fallen through a rotten floor board in a house.
- Steady speeds are easy, but accelerations and sprinting are difficult
- It is comfortable to pedal seated but uncomfortable to pedal when standing
- You might experience pain at the front of the knee that you haven’t had before“
Mathew Fy
GRU
Cruzbike reported their wind tunnel results: “The Ninja V18 adapters, which make the V20 effectively a V18 (still in prototype testing) saved a solid 8 Watts at 0 yaw and had no effect at the oblique angle.”
Also reported: “Another success was a prototype of a customer-designed frame pack called the “Moosepack” that fits under the seat. This saved 3.8 Watts at 0 yaw and was neutral at 7 degree yaw.” Nice work, I bought one for my own V20.
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bladderhead
Zen MBB Master
The long axis is 72 degrees clockwise of the crank arm. This is the most comfortable orientation for me. I think it is almost the same as Biopace, where the highest gear is at the dead spot. I think I would like to make a finer adjustment to the orientation and I think I want a longer thinner ellipse, but how can I find exactly what shape a chainwheel is, and how can I find one that fits my cranks?
Andrew Wilson
Guru
Heres how mine is set, also an older pic when Jim and Maria were testing in the wind tunnel with Q ring set like a DF. I would love to hear if they are still running it this way. I might have to try just for the heck of it.
Attachments
the set up of TRPLAY is the opposite of Bladderheads set up.can someone explain the different phillosofies of the oval setups.the biopace chainwheels were made to take force from the knee.the osymetric and rotor once to have max powersupport during the pedal stroke.the dead point is in this case in every setup the position where your leg is stretched .taking this in mind the setup of trplay is almost near to this thoughts.i am wondering why most of the other CB riders with oval chainrings have choosen an the other setup.the only idea i have is ,that pedaling an MBB, in your max power position the stearing direction is influenced.so the setup of most takes power from the powerfullsed orientation and may be gives a mor stable and straight ride.
chicorider
Zen MBB Master
