Tandem Cycling - Crank arm length on my single vs. tandem
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05-31-06, 08:31 PM
I have ridden the same single since 1992 -- Trek 5200 OCLV -- which has served me very well. I am just now buying a new single and it should arrive by next week -- Cannondale Six13 Team 1.
I am a short rider at 5' 6.5" and around a 28" inseam (maybe 28.5"). My 5200 has 170mm crank arms and that is what I'm used to after all these years. When I ordered the tandem last summer I didn't even 'think' about crank arm length ... just totally went over my head, etc. Well, when ordering my new Cannondale single, I wanted to be sure I had 170's if at all possible so I would be comfy and close to the more appropriate crank arm length for me (actually, I would need a 165 according to some formulas I've seen).
In doing all of this, I noticed tonight that the tandem has 175's in the front!!! Wow! Now, I think I totally udnerstand why I ALWAYS felt SO TIRED and SPENT no matter who my stoker was. I never did feel "right" and I just could not put my finger on the reason. I swapped seats, seat position, stems, stem, and handlebars to no avail. I just thought it was "me" on a tandem with various stokers, etc.
Well, now I am truly wondering if it is the crank arm length. Any thoughts?
Well... I don't think this necessarily relates to your crank arm length. It's just more work piloting a tandem! Having said that: I've ridden 175s for ever, and have a set of 170s on my 2nd tandem. Frankly, 170s sound too short for you. 172s would seem to be your size. How many variations have you tried? If only 170s, I don't see that you really established they're the right size. I went from 170s to 172, 175s 177s, back to 175s over the course of several years of racing before settling on 175s. I do hvae 175s on my A tandem. Good luck.
06-01-06, 08:07 AM
ElRey -- Yes, I understand that piloting a tandem requires much more effort, etc. especially after making several posts here last summer and learning that it is typical. However, there is still that oddity that I couldn't figure out that I felt was something I should be able to determine and modify. And, now I think it is crank arm length.
Here is one of the two calculators I was referring to: http://cranklength.info/crankCalc.htm
I have only used 170's and now 175's on the tandem. So, I don't have any experience with 172's. But, given what I have seen on crank arm length using forumulas such as the above, I see a trend toward the shorter crank arms given my short inseam.
the only real answer is in experimentation. Good luck with it!!!!
06-01-06, 08:21 AM
I'm 5'8" w/29" inseam (and seem to be shinking as I used to be 5'9" w/30").
Tandem cranks @ 175mm (Somewhat narrow tread / Q-factor)
Solo bike cranks @ 170mm (Very narrow tread / Q-factor)
Fixed gear cranks @ 165mm (Average tread / Q-factor)
Yes, they all "feel" different, but they also "feel right" for each application. It only takes me a bit of time to adjust, but adaptabilty varies greatly by individual. In fact, with tandems it's not all that bizarre when you hear about a team that discovered they had mis-matched cranks... (175 R / 170 L for the captain & 170 R / 175 L for the stoker) ... about a year after they started riding.
For the tandem, I like the slightly longer lever and Debbie appreciates that the slightly longer cranks slow my cadence a bit. On the road bikes, 170mm is all I've ever used. On the fixed gear, the short cranks feel really weird for the first 10 minutes, but are really appreciated when you're spinning like mad on the steeper downhills.
Try to find some different length cranks to play with and go with what "feels" the best to you...
When we bought our Burley Rivazza, we hoped to get cranks in our preferred sizes, but Burley doesn't let you choose (I guess they only buy those two sizes). The lbs we ordered the bike from would have switched them out for us except that they don't carry that model of FSA carbon cranks. They did contact FSA, though, and FSA also declined to switch them out for us (thanks, guys). We've gone ahead and used the sizes they sent us and have loved the bike ... but I still wonder whether it wouldn't have been even better with the sizes we use on our single bikes.
06-01-06, 03:14 PM
I'm just about 1/2 inch taller than you, and have always used 172.5 mm cranks on my singles, and like you, our Burley was delivered w/ 175's on the front. From my perspective, the only real difference I can notice is that I tend to spin 5-10 rpm's faster on the single than I do on the tandem. I've not been able to determine yet, if that was due to the longer crank arms or the fact that Pam prefers to not spin that fast.
I also get more tired on the tandem, but am sure that's just from the increased effort required to pilot, as well as the fact that we're hauling twice as much bike up and down hills at what I feel is probably a 60/40 split of the workload between captain and stoker. I consider it a small price to pay for the opportunity to ride with my sweetie!
Edit...maybe I need to rethink that 60/40 above. Did an easy 30 miler today, and shortly after taking a coke break at 15 miles we hit a pretty reasonable hill. As I huffed my way over the crest, I commented that the first hill after a break always seemed hard. Her reply...."Oh, did we go up a hill? I didn't notice!".
06-02-06, 07:30 AM
from what I've read, there are about as many different opinions on crank length as there are people who care about crank length.
Personally, I think its personal. If it feels right, it is right (on the bike, anyway...). One of the problems with the formula is that it doesn't take into account the proportion between upper and lower leg. As it does hint, if you have longer femurs (proportionally) you'll probably want slightly longer cranks and vise versa. But if you've been riding 170s and have been happy, I'd stick with 170s (unless you like screwing around with your position (which I don't) or have some disposable income to drop on crank experimenation).
Also, you shorter cranks will undoubtedly be a little easier to spin than the longer cranks--so if you're a "spinner" rather than a "masher", that is something to consider.
By the way, if you want another formula, Lennard Zinn claims that you should take your cycling inseam times .216 for the proper length (so he automatically recommends slightly longer cranks than your formula). But its all taste.
06-02-06, 09:10 AM
FWIW: Every formula suggests that 165mm "should" be the right length given my inseam or, using a factor of .185 x the top of the femur to ground. From a practical and cost-benefit standpoint, if I decided to adopt the "optimum" formula-based cranklength I'd have to layout over $2,500 for new cranks...
3 sets of 175/170 daVinci cross-over cranksets (remembering that Debbie's cranks are way too long by any formula)
2 sets of 170 cranks on my road bikes; one set of 110 TA Specialties Zephers & one set of Campy Chorus
1 set of 170 cranks on my off-road bike/ TruVativ somethingorothers
1 set of 170 cranks on Debbie's road bike; Campy Centaur triple
So, maybe.... just maybe if and when we ever have a reason to upgrade a set of cranks or to replace one of the bikes in the stable...
06-02-06, 03:40 PM
Thanks for all the feedback. I have asked my LBS ownder to swap my 175 Travativ's out with some 170's and he said he would oblige. Just have to order them as I'm not sure he has then in stock.
06-03-06, 01:51 PM
I ride 165's on my track bike, 170's on my fixed gear rain bike and on my tandem, and 175's on my road racing bike. I can't really feel the difference between them, and I've been riding for about 35 years. (btw, I'm 6'1 with 35" inseam.)
If you do the calculations, there's about a 3% difference in pedal arc circumference for every 5 mm of crank length. This translates to about 3% more foot speed required for every 5 mm you add to the crank. This is why you use shorter cranks on the track - you're stuck with one gear, so you need to leverage leg speed (ultimately foot speed). For a given angular velocity, the linear velocity of your foot will be less with a shorter crank (or, in reverse, tor a given linear velocity of your foot, you'll be cranking faster). This gives you an advantage.
For tandems, I think it's a good strategy to give the experienced rider slightly longer cranks. Since this is usually the driver (I've never liked "captain," "driver" is the track term), 175's are appropriate for the front. Not only does this give a bit more leverage for the additional weight and higher startup inertia required, but inexperienced stokers are usually uncomfortable pedaling at the spin rate of an experienced cyclist, so a 3- to 6% difference in foot speed might help to match a team with disparate experience.
06-03-06, 08:18 PM
Concur that most folks will not feel a 5mm difference in crankarm length. On our tandem(s): pilot 5'7", stoker 4' 10 3/4" . . . and we both use 170mm crankarms.
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