Short Crank Arms
I chanced upon an eBay listing for short-crank arms and managed to pick up these! A bonus, since they were SRAM Force crank arms shortened to 150mm, so matched the rest of my groupset. I have been very curious about how short cranks would suit me as I figure (a) I would like less "flailing" of legs up on my high BB and (b) I would like the extra cockpit room they would afford, as I could move my handlebar forward.
These crankarms are a whole 20mm shorter than my previous ones. I adjusted my front-end resulting in a slightly more sloping boom. This gave me noticeably more thigh clearance to the handlebar, so I have moved the bars forward as the more I ride Silvio, the more I like straight arms. I've only done testing for fit downstairs. They feel good so far, but no proper ride yet...there was a CB thread some years ago on short crank arms. I wonder who else has them now?
With all these Silvio 2 owners waxing lyrical about their recent Vendetta experiences, my poor Silvio is getting nervous. Don't worry dear - you still look lovely...
That is a nice looking set of cranks! Do you feel like you have lose some leverage at all?
Lol Cruz moose has been entertained by the Vendetta over exuberance also. A few of their calculations have this fat , aero bellied, cat 6 rider faster than world record holders if I just rode a Vendetta. It would be interesting to see some strava data eh?
Looks nice Ivan. I too wish I had gone with shorter cranks than my 172.5's. Is it any easier for you to sit up on the bike?
I say we hold out for the Vendetta 3.0 before "upgrading", I'm sure it will leave the 2.0 in the dust.
I have been using short cranks on my Vendetta for about two years. The crankset is an FSA Gossamer compact double cut down to 153.5mm. I feel like they are easier on my knees, with little effect on speed. On my next Silvio I would like to get a crankset with arms @ or around 160mm.
Are you planning on getting another Silvio or another Vendetta? (per your last post)
Do you have one of each now?
I started with a Sofrider, then went to the Silvio v.1, then got a Vendetta (first production run). Within the last year the Sofrider and Silvio have been sold leaving me with only the Vendetta. I am in line to get one of the new Silvio's. I think it's wise to have an extra horse in the stable at all times.
Yes, I am hooked on Cruzbike after only having and riding my Silvio 2.0 for less than 2 months.
I really want to get a Vendetta now, but the cost is making to step back and evaluate it closer. WIsh I had unlimited funds!!
I would be nice to have a Silvio to train with and a Vendetta to race with, plus you have one to ride while you are "working" on the other one.
SILVIO: my new short crank arms made me feel really fast. I am sure I was 7% faster and felt more reclined, like down to 20 deg or so. I think I shall rename myself silVio so that no one gets any funny ideas about replacing me with a faster yellower model.
IVAN: the short crank arms were interesting during my 2 hour ride time today. Too early to say if it made me faster. I couldn't sprint any faster but cruising along did seem a little easier. Was this better aerodynamics with less flailing legs as it was only noticeable at 35-40kph or was it all this recent Vendetta talk going to my head. I was definitely spinning more and thus using different gears. While I definitely lost some leverage, it was perfectly natural to just spin up more so no penalty loss. The HUGE DIFFERENCE for me was stability. It is much easier to keep Silvio tracking straight with these short crank arms. I did some no hands riding today and I could further and straighter. So my first 2 hours says I like it!
Unfortunately had my closest call today on Silvio when 2 motorcycles and 2 cars turned in front of me at an intersection. Yikes! How they managed to miss my 800 lumen flashing front light I do not know!!
Those cranks look like the handy work Mark over at BikeSmith, but I don't remember him doing Carbon mods for SRAM. He lives in my area I'll have to ask him the next time I see him.
This article is old but has a lot of good references in it.
I was astonished to see my knee angle was 60 degrees (or less).
Ouch! No wonder my knees hurt!!!!
I am hoping that adding the 100mm chainstay extension will open it up a little bit, but according to my calculations even that ane 150mm crank arms will not get me to the 90 degrees that I should be shooting for.
I think this will also definitely help my stability on the bicycle (less flailing too.)
Am I just a strangely sized person that I can't get the right fit?
Ivan, how did you come across those 150mm cranks. Where they specially shortened somehow. The smallest cranks I can see on any SRAM crank arm is 162.5mm. What is your measured leg angle when your pedal stroke is the closest? Thanks!
I have SRAM FORCE 22 170mm now.
If anyone see a compatible set of 150mm cranks, please forward me the information!
Hey Larry, hard to tell by the photo. What is your xseam and how tall are you?
I have legs of a 5'10" guy. That was my original height before my spine compressed made me about 5'8". My xseam is roughly 42".
I installed the 100mm extension a couple of days ago. The extension won't open it up more, what will happen is the handlebars will rotate downward into your belly area. The BB/pedals will sort of rotate up and back towards you.
In order for me to get clearance for the top of my thighs on the pedal back stroke I moved the handlebars closer to me, thus my arms are a little more bent now. My thigh still touches some, but I can't go back any further.
I'm using 165mm crank arms. I've tried 175mm, 172.5mm, 170mm, 155mm, and 145mm, and settled on 165mm. With short arms you give up leverage and you swill pin a higher cadence. I like the leverage for hills, that's where you will miss the leverage.
Make sure your boom is adjusted to work for you. Generally if boom is in too far in, the top of the knees may ache, out too far back of knees may ache.
For me, it takes trial and error on anew bike with lots of small adjustments to get it right. So you may need to experiment some.
The bike smith is a good source for short cranks: http://bikesmithdesign.com/Short_Cranks/shorten.html
Bike Smith is where I got my short cranks.
I have 155 105s on my Silvio V1 and 158 Sram Apax on my Silvio V2.1>Bikesmith did them both.Im happy with them. Jack
I am 5'7'' (or a touch under at the start of the day!)
X-seam is 40.5"
Thanks everyone for the feedback.
I am hopefully installing my chainstay extension (thanks in advance to BentAero for the help) tonight and will be able to experiment with the boom and body position also.
It sure would be nice to have a full set (140 - 165mm ) of cranks to just try out! dream on!
Bob also said he thought I was sitting too far back in the seat (but not in right place), so maybe everything will work out and get me a better position!
I will let you know how it goes and hopefully post a photo of the new setup.
Incase anyone is looking at those picture and figuring out the ergos. It looks like that the boom is too short, (perhaps too far back after it's lengthened) AND your are touch too far back on the seat. I be curious how far back other sit; we definitely are sitting to the front of the seat. If you only scooted forward the knee bend problem would actually get worse. If you get the boom longer the feet will move out and down which fixes that knee angle. The extension will then elevate the feet for the aero you seeking. Just adding the extension won't solve it; as those feet need to move forward horizontally to fix the knee bend. It was riding the quest that taught us that we always start with the booms too short.
Mrs Ratz is 5'7" also with long legs fitting her was a challenge as it was easy to miss the optimal position in a number of ways. Her boom appears to be set longer than your picture; thus her crank is farther forward and lower that what you have pictured. Boom length 33", and from the slider clamp to the handlebar clamp is 13"(short arms), neither her nor I break 90 degrees at the knee when we pedal. We are however using 165mm cranks. I'm guessing gary can get you all situated; this really one of those you have putter with until it's right or have someone fit you on the bike that has done it before.
Yeah, looking at the close up, right knee looks a little too bent, at least it would be for me, which would cause my knees to ache. As far as where Larry is on the seat, I can't comment. I do like the Angle Tech rear seat pod however, looks like lots of room too.
Though pricey, you can always try http://www.powercranks.com/OrderPowerCranks.html. Here are a couple of photos from their website...
Larry, from your photo a chainstay extension doesn't look workable, to me -- I'll be interested to hear what happens with that! Seems like lengthening the boom and shortening the cranks are the things to try.
As for the position in the seat, I used to have some discomfort in my lower back if I scooted all the way back in the seat, so I would sit forward a bit. But, on my last couple of rides I found it perfectly comfortable to sit all the way back in the seat. I'm not sure it matters much, except that it does affect the pedal/handlebar/headrest adjustments.
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.
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.
Thanks to everyone for all their comments - it is so very helpful!
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.
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
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.
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.
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.
My Silvio 1.0 has SRAM Apex cranks shortened by Mark Stonich to 150mm.
The Apex cranks come with a BB but just install the short cranks on your present Force BB and be done.
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!
Here are two references for adjusting Q-rings that I found helpful.
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!
Real happy to hear that your fit is coming along nicely and those short cranks are helping!
If Cruzbike offered an ~50mm extension I'd order it now, but maybe I'm just being too picky (those 100mm extensions look huge).
Check this post for adjustment discussion Larry.
(perhaps a poorly titled one?)
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!
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.
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.
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.
However - in the top photo, your right leg looks pretty good. What am I missing?
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.
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.
I have now moved my boom about 1" closer to me - still have 60mm extension, Ventist seat pad, 150mm cranks, and Q-rings installed.
Per suggestion of Steve, I first tried to position myself with my heel flat against the pedal with my leg fully extended and knee locked. Then when I clip in, I have a slight bend in my knee at the same position. Seems to work pretty nicely. My knee is still bend more than I would really like when when pedal is closest, but much better than it was. Went on about a 30 mile ride last night. Felt pretty good. Think my knee and calves are almost totally recovered now . Will try about a 60 mile ride today as my final longish ride before then Mid-Atlantic event next Sat (23rd), then a few easy rides next week with final tuning if needed. My only issue now is that I have a "clanking" sound from my derailleur (Gary thinks it might be the clutch). It seems to get worse the faster I go. It is not related to how hard I am pushing, so pretty sure it is not in the BB. Very annoying however - hope to get this resolved before the Mid-Atlantic, as I would hate to have to ride with it clanking like that for 12 hours. Here are my last pics of my positions:
Hi Larry, the clanking sound - check the q-ring when at it's largest dia, the chain my be rubbing the top-inside of the front derailleur.
Wow that's looking a lot better. One last thing you can try. Those look like SPD clipless pedals. If so; mount the shoe bracket as close to the heel as the shoe allows. That will take a few more millimeters out of the leg bend. It feels weird at first but your legs will quickly adapt; you clip-in technique will be off for a few days as you miss the peds but that come back fast.