Short Crank Arms

[ratz]

Seat Pad Matters too...

I forgot to mention; we also switched out the seat pads to Ventisit ones; those are thinner 2cm or 3cm thick; that picks up some room in the cockpit; and compliments the shorter cranks nicely. The are a lot firmer; after 2-3 rides you don't notice and they soften up. I have no problem going 80 miles on them without noticing. They might be a bit firm for Eric's 24 hour endeavors.

http://www.ventisit.com/en/products/recumbent-bicycles#!/~/product/id=28856169

 

[Ivan]

Larry, I think you can

Larry, I think you can lengthen your boom so that your BB goes more forward, thus extending your legs more and improving that uncomfortable angle you have now. The reason I think your BB can go forward is that you appear much taller than me, and your BB is closer to the front wheel axle than mine.

I looked at my old video of me learning Silvio last year and captured this screen shot. This is with 170mm cranks. My height is 5'8". You can see that my knee angle drops below 90 deg too but not as acute as yours. I have since stretched myself more out, extending the boom slightly and extending the headrest quite a bit.

 

[LarryOz]

Thanks to everyone for all

Thanks to everyone for all their comments - it is so very helpful!

Ivan,
Thanks for the feedback. I may appear much taller than you (bless you my son!), but I am only 5'7" (and that's in the morning after I spend 30 minutes on the stretcher! ).
Anyway - I did install the 100 chainstay extender last night (thanks for all the help BentAreo), and moved the boom out. My thighs hit my handlebars and my legs where still really bent. Maybe not 60 degrees, but probably still under 70. I moved the handlebars back a little so I could at least pedal. It was 10:30pm and raining at that point, so I did not get to try it out.
I think I am definitely going to need shorter cranks. Problem here in Asheville, NC is we have (mountains! - you can hardly ride 3 miles without having to climb at least 100 foot grade somewhere, and then there is the Blue Ridge Parkway, Mount MItchell, etc, etc. 6% grades that go forever) I do not have any practical experience with shorter cranks, but the math says the longer the crank the more leverage (i.e better hill climbing). What kind of terrain do you ride where you are at. Have you noticed any decrease in leverage going from 170mm down to 150mm cranks.
I am feverishly looking for some now, but I have SRAM Force 22 crankset which I think are at least partially CF. I wonder if it is possible for them to be modified. For sure not as easily as a pure metal crank.

Bob,
Thanks also for the live help last night with the seat ad BB dragging issue. I will experiment with sliding forward it the seat. I did it just sitting there, but even with it, my legs where still really bend when the pedal was the closest. It was late, dark and raining after our final adjustment, so could not really try it out. I think however to really make it work, I am going to have to cut down the top of the seat to allow the headrest to move closer to the handlebars because now it is butted up again the top of the seat.

Ashtabula - Those powercranks look really radical!
I read the web page and still can't figure out if they are just something you train with, but then go back to regular (once you figure your size and re-learn your pedaling techinique) if you are in an event or racing. It is really cool though that they are adjustable like that, which would allow someone like me to try different sizes almost effortlessly.
I am going to call them today and get the complete low-down

 

[John Tolhurst]

yes the math says the longer

yes the math says the longer the crank the more leverage, but only if you have a single speed set up. The real question is how many inches pedal travel compared to road travel, what is the ratio of the gain in speed that you get - the famous 'gain ratio'. That is the true leverage. You can get what ever leverage you like by changing gear, even with short cranks.

It might be that you have proportionally long shins, or so it appears to me. Short cranks open the leg angle, if so.

 

[Robert Holler]

I agree with Johns

I agree with Johns observation and I have a similar issue. This sort of fit challenge is not uncommon, but on some recumbents it is not an issue (like on a stick highracer) because your legs are on the other side of the handlebars eliminating the need to account for the "foot to top of leg" measurement altogether.

A lot of boom extension will indeed pivot that bar into your lap. I am 6' tall with a 42 x-seam and the 100 made the Silvio more like a Vendetta (with slightly lower handlebars) and the 150 made it impossible for me to fit in the bike without the possibility of a giant shoehorn to slip myself between the handlebars and the seat.

It does look like the handlebars can be moved back a bit and the boom moved forward just a small bit.

Be wary of too short of a crank setup. Too short and it starts to make spinning effectively difficult. In the ideal world everyone would have their own ideal crank length but the market has really set 170's as what people expect to see. Yes you can account for gearing but when the hills come you WILL notice the leverage loss. My daughter for a time ran crank shorteners on a 20" Q that had the long chainstay. The shorteners effectively gave her 110mm cranks and it was crazy to pedal and especially hard up the hills even with low gears. ;-)

She would stall on a particular hill in our neighborhood "Dad my legs are stopping my legs are stopping!!" haha. Later I swapped back to the short chainstay and she could reach with the stock 155's. She can motor up that same hill.

 

[Eric Winn]

My Vendetta Fit Larry, I'm

My Vendetta Fit

Larry, I'm 5 feet 6.5 inches tall or so. Used to be right at 5 foot 7 inches but have shrunk some - combination hair loss and compression I guess...

I use 170mm cranks. And it is a Vendetta, not a Silvio, but...

Note: Measurements are very approximate.

Bottom bracket front, center to where line thru headset bisects the boom following the top contour of the boom: 23 inches
Bottom bracket front, center to where line thru headset bisects the boom following a straight line: 20 inches

Continuing from above - headset line thru boom to center of handlebar clamp: 11 inches
Note my hands are forward and up from the clamp with my bullhorns.

Trailing edge of handlebars at the clamp to bottom curve of headrest frame: 22 inches

Center of pivot for bar end shifters to bottom curve of headrest frame: 31.5 inches

Seat crease up to bottom of handlebar clamp (no cushions): 15.5 inches

Leading edge of bottom seat pan to most extended (farthest) pedal position: 32.5 inches
Leading edge of bottom seat pan to least extended (closest) pedal position: 17.5 inches

I'll try and mark up some photos with the above and add them later.

Here is a video of when I was first assembling my Vendetta to check fit and clearance. In this case, no wheels, just the frame, seat, cushions, headrest, handlebars, BB, cranks and pedals with the wheel dropouts on my carpet. I was very carefully sitting in the seat and gently pedaling to check for clearances after making adjustments, check fit and clearance, repeat.

http://youtu.be/lhXIYVjZYtI?

-Eric

 

[Bruce B]

SRAM 150mmCranks

Larry,

My Silvio 1.0 has SRAM Apex cranks shortened by Mark Stonich to 150mm.

http://bikesmithdesign.com/Short_Cranks/index.html

The Apex cranks come with a BB but just install the short cranks on your present Force BB and be done.

 

[LarryOz]

I just ordered a set of 150mm's from Mark

Thanks again for all the feedback and comments - very helpful!
150mm cranks - SMAM Apex
Also having him put Q-rings on it.
He said it should be done by Wed - hoping to get it by the weekend and try it out.

I just rode 146 miles today with heavy mountains 15K altitude with the new 100 chainstay extension!
My body is screaming at me now!
The boom is really low to my body. No room for a water bottle, and I am pretty thin.
I am sitting way forward on the seat per suggestion by Ratz, but now I need a support for my back and will need to bring my headrest closer. It sure felt strange, and I developed cramps in both calves. Not sure if due to stretching out farther than normal for the pedals or not?
I am hoping the 150mm cranks will help solve some of the ergo issues.
Will give an update when I install and try out the new setup!

 

[Bruce B]

Q-Rings

Larry,

Here are two references for adjusting Q-rings that I found helpful.

http://cruzbike.com/adjusting-elliptical-or-ovoid-chainwheels

http://www.rotorbikeusa.com/pdf/Q-Ring%20Recumbent%20instructions.pdf

 

[LarryOz]

150mm cranks installed - waiting on Q-rings

Last night I installed the 150mm cranks on my S2.0 (Thanks for the help BentAero).
I did a short, easy 15 mile test ride to work this morning. I had not ridden in a week, since I rode my 150 mile (mt. mitchell torture ride) with "new" 100mm extension and my boom out too far. My calves have still not 100% forgiven me or healed up from that ordeal, but at least I can walk and ride now!
...
Anyway. The 150mm cranks both shortened my leg extension to where I was not over extended any more and also opened up my knee angle. So far I am pretty happy with it. ?Felt really good riding and ergonomically, and I did not notice any loss of power going up the hills. For the effort exerted it really seemed to me like I was a little faster than normal, although I did not ride as far as I have normally been going in the morning. Also don't have a power meter to truly confirm that "feeling". Planning on doing a century this weekend if the weather holds up and that might tell me more (they are forcasting 5 1/2 inches of rain between now and end of Sunday, so I might just be riding my indoor stationary recumbent in front of the TV watching the PGA championshion instead).

Gary still thinks a 60mm extension would be better for me than than 100. Steve has set me his 40mm and 60mm to try out. So will do that next week and see if we can "fine tune" the ride even further!

I am also supposed to be getting my Q-rings in today. Not sure if I will put them on before the weekend or not.
Those of you who are riding Q-rings. What is the "riding" adjustment time with them? Is it foolish to put them on just before a long ride (100+ miles)? Is there already a thread all about Q-ring setup and issues? I have JT's blog on Adjusting Elliptical Chainweels, but am still not really clear on the whole process. For instance do you take all the original "measurements" (BDC to Chain Angle) with the original round chain rings first? As it doesn't make sense to just stick the oval rings on "anywhere" and then try and find these values, but the instructions dont really seem to say?

Thanks again to everyone for there help and suggestions. This is such a great and giving group of riders!
I will try and get someone to video me spining and post it later. Right now the rain has begun!

 

[Ivan]

Real happy to hear that your

Real happy to hear that your fit is coming along nicely and those short cranks are helping!

 

[Jeremy S]

If Cruzbike offered an ~50mm

If Cruzbike offered an ~50mm extension I'd order it now, but maybe I'm just being too picky (those 100mm extensions look huge).

 

[Lief]

Q Ring Adjustment

Check this post for adjustment discussion Larry.

http://cruzbike.com/rotor-q-ring-not-suitable-recumbents


(perhaps a poorly titled one?)

 

[LarryOz]

Instructions off Rotor website good

Thanks Bruce for the link (?http://www.rotorbikeusa.com/pdf/Q-Ring%20Recumbent%20instructions.pdf)
to the instructions off the rotor website. They where pretty clear and easy to use.
It did not take me very long to set up and install the Q-rings.
I have only riden on them 25 miles or so (and in a heavy downpour with 15+ mph headwind most of the way), so kind of hard to quantify any advantage over the round rings I had previously.
They do not "feel" strange to ride on however.
They strangest thing is being able to see the chainring going "up and down" since it is sitting right in front of you!

 

[LarryOz]

leg rotation with 150mm cranks and 100mm extension

I am very pleased so far with my change over to the 150mm cranks.
No more flailing. Climbing is also no problem so far
Here are some pics of my leg extensions as I rotate through.
My knee bend is just about 90 degrees now, so that is great too.
Someone said earlier to me that my shoulders, hands and feet should be in line for best power. I think they are pretty in line now.
I just wish I could have room for the water bottle under the boom. To get that I might have to change out the 100mm extension with a 60, but that would have the effect of moving my feet down and my hands up. Then they would not be in line.
Comments? suggestions?

 

[LarryOz]

Now with 60mm extension

I also switched out the seat pad for the new Ventist seat pad, so I think that had the affect of extending my max leg extension out maybe another 10mm.
I think I have room for my water bottle now below the boom now, but maybe not as Aero as I was with the 100mm extension.
I have only ridden 10 miles on it so hard to really tell anything.

 

[Rick Youngblood]

Hey Larry, in the bottom

Hey Larry, in the bottom photo, your left leg looks really extended, pretty much straight, which could cause some pain behind your knee and the back of the legs by over stretching everything back there - that is if I'm looking at the photo properly. You want a slight bend in your leg when the pedal is at it's farthest.

 

[Rick Youngblood]

However - in the top photo,

However - in the top photo, your right leg looks pretty good. What am I missing?

 

[LarryOz]

hard to tell

Rick,
Do you mean the "top" photo just above that last bottom photo?
Not really sure - there are 2 sets of 3 photos. 1st set was with 100mm ext, 2nd set with 60 mm ext. plus new Ventist seat pad. (which I think moved me farther away from BB)
Truthfully it is a little hard to be really consistent I think when backpedaling (i.e. keeping the same ankle angle, etc)
I have since moved the boom about an inch closer and set up my heal (as suggested by Steve) on my pedal with my leg locked straight. That seems to work pretty well when I am clicked in in allowing my leg have a nice small bend when clipped in at max extension . No pictures yet to share however I did a short 10 mile ride today to test. May post one later today if I can get someone to take on of me.

 

[Rick Youngblood]

Hi Larry - I was referring to

Hi Larry - I was referring to the last set of photos. But it sounds like you've made adjustments. I know backpeddling is awkward trying to look at extending leg.