The adjustable crankset experience

Posted by SuperClydesdale on June 17, 2010 under Cranksets, Road Bike Components | 2 Comments to Read

As regular readers will know, I am evaluating different crank arm lengths to see what is best for me.  I’ve concluded that “standard” cranks are just too short for a guy like me with a 36″ true inseam.   I want proportionally correct cranks (apparently, that’s the correct phrase — “longer cranks” implies that somehow the cranks are longer than they should be).

To test this out, I rented an adjustable crankset, which allows me to go from 180-200mm.  I just installed these on Friday.  So far, I have done four rides on the new cranks:

  • With 200mm crank arms:  Two 25-mile rides with moderate climbing (1700 and 1600 feet of climb)
  • With 190mm crank arms:  Two identical 34-mile rides with 2967 feet of climb.

The square taper bottom bracket:  the standard for custom-length cranks

I think it’s for ease of manufacture, because all of the custom cranksets that I am looking at use a square taper bottom bracket.  A square taper crankset  just needs a square hole to mount, unlike more complicated systems like Shimano’s Octalink, so it’s very easy for limited-production items like a custom crankset to be produced relatively inexpensively with just a square hole to worry about.

Luckily, a low-end bottom square taper bracket is pretty cheap, so It was only a $19 investment to get one at my LBS.

The evaluation of different crank arm lengths

I have been riding 180mm Dura Ace cranks on this particular bike, so the goal of the evaluation was to compare longer crank arms  from 190mm-200mm.  Unfortunately, the unit that Zinn (where I rented them) sent would really only go to 200mm, and that was a bit of a stretch because the crank arms that slide in & out of the “base unit” of the adjustable crankset were cut too short.  Only one of the two Allen bolts could clamp down on the arm.   This is not very secure, so, while I could try it out at 200mm, I couldn’t risk a  vigorous ride without fearing of damaging the cranks.  The only remedy for this would be to get Zinn to send longer arms.  I’m not patient enough for that.

200mm Crank arms

My first trial was at 200mm.  I set the crank arms, then lowered my seat by 20mm to keep my knee bend at the end of the stroke the same as I am used to (which I consider be correct).  As I cruised around my driveway, I could feel my legs making the more exaggerated orbit around the bottom bracket.    I made some turns to get a feel for how sharp of a turn I could make without the pedal striking the ground.

Satisfied that I had a feel for it, I headed out for a 25 mile ride with moderate climbing.  Perhaps jumping from 180mm straight to 200mm was a bit aggressive.  The first few miles felt very strange.  Surprisingly, after about 5 miles the unfamiliar feel faded somewhat, and I became accustomed to the pedal stroke.

I could definitely feel the increased leverage created by the longer cranks.   There was a noticeable difference in climbing ability.  It felt like I had some extra gears.  There is a ½-mile-long hill of about 7% grade a little less than a mile from my house.  Normally, I grind up it in 44/27 because I’m not warmed up (this is literally a few minutes into the ride).  On this ride, I was up in 44/25, and really could have gone lower, but I was still adjusting to the new feel.

On the flats and downhill, I could really jam.  My cadence initially seemed to be a bit lower, but in looking at my stats, its right there with that of my 180mm crankset.

The next day, I went out for another 25-mile test ride.  This time, I the pedal stroke didn’t seem awkward — It felt great.   I really felt the extra power.  My  intent was to open it up on the flats.  I found that could sustain a higher average speed over rolling terrain with the longer cranks.  The average pace for the ride was nearly 1mph faster than my average for the same loop, although the work effort was what I would call normal.

190mm crank arms

Next up was the 190mm.  This length I can test more vigorously because the arms can both be firmly clamped down by both bolts.

With this, I did two rides, each my standard 34-mile loop from my house that has significant climbing (2967 feet of climb).  I’ve done this loop many times, so I have a lot of data on it.  I finished these rides with an vigorelle does it really work average speed about .75 mph higher average speed for the loop.  The cadence was pretty much my average for the other rides with shorter crank arms.

This was interesting in that the pedal stroke felt normal from the first moment I tried the 190mm cranks.   On hills, I noticed that I had the power of at least one more gear.  On stretches where I normally have to get out of the saddle, I remained seated, which is far more efficient for a big guy when climbing.

Larger chain rings on longer crank arms

I picked up a 54-tooth chain ring this weekend.  I hope to be able to try that out with longer crank arms soon.  That will mostly be for downhill, but I look forward to really being able to fly.

Conclusion of using a longer crankset

After just four rides, I have convinced myself that I can effectively use and will benefit from the use of longer cranks.  While I was unable to test the 200mm as vigorously as I would have liked, I was able to get a good feel for them.  According to the two schools of thought around appropriate crank are length (basing it on inseam or on femur length), I should be using somewhere between 183- 197.5mm cranks.  This is a bit of a rehash for people that have read articles on this topic here before, but take a look at the two tables below the first table is inseam-based, the second is femur length (based on femur lengths I extrapolated based on research revealing average femur length to height for Caucasian males).

Recommended crankset length based on inseam

Recommended crankset length to femur bone

Recommended crankset length to femur bone

I’m “voting with my pocket book” — I just ordered 195mm cranks.  I decided on 195 over 200mm to reduce the chance of pedal strike.  Without a custom frame with a higher bottom bracket, the pedals are going to more apt to hit the ground if I’m not careful on sharp turns.  195 will reduce that a bit.

I spoke to Tom at High Sierra Cycle Center (1-800-438-4399), who has been making custom cranks for more than 20 years.  Tom is nice guy, and a wealth of information.  I told him that after studying the pictures of his cranks and the cranks on Zinn’s web site, that it appeared that the cranks were identical.  He admitted that for the Zinn “non-integrated” cranks, he has been manufacturing them in partnership with Zinn.

Here’s the plus:  High Sierra is a lot cheaper.  Same crank, lower price.  You decide.

High Sierra is coming out with a new integrated bottom bracket crank design in the immediate future as well.  They will still offer the traditional square-taper crankset, but it sounds like the new one has some special characteristics.  I’ll hopefully provide more on that soon.

Why did I order longer cranks? Even after just four rides, the result is obvious.   190mm cranks felt exactly like my 180mm, but I get power for less effort. That means faster climbing, and more power on those long pulls. Plus, It’s a relatively inexpensive modification.  $350 for a crankset is a good price  – what else can you spend $350 on to get such a big impact on performance?  People will drop $1000 on a wheelset just because they are a little more aero.  This effects your quality of life!

The cranks come with a 1-year warranty.  They are a little beefier than my Dura Ace 180mms but they are designed for hard use by big riders.  That’s worth a few grams in my book, as longer crank arms means more leverage on the cranks and more stress on them.  Plus, the extra power gained overcomes the negative impact of any slight increase in weight.

A Special Offer for SuperClydesdale readers

I spoke with Tom at Sierra about getting a group discount for superclydesdale.com readers. If at least 10 people to buy cranks, he will give everyone a 15% discount.  15% off of an already inexpensive crankset is a screaming deal.  It’s too late for me – I already ordered mine, but if you are interested, fill out the form below.

Once I get my cranks, I will re-post this offer, along with a photo of the crankset.

Tom is a wealth of knowledge, having been making these cranksets for over 20 years.  If you have questions, please ask me.  I’d like to collect the questions and answers and share them with everyone for mutual benefit.  Send your questions to jack@superclydesdale.com and I will update this post with answers.

Fill in your e-mail address and I'll send you an e-mail when there's enough people to qualify for High Sierra's 15% off offer.
  • macspud said,

    Hello SuperClydesdale,
    I came across your post/site whilst looking for crank arms a bit more to my size, very hard/impossible to find unless custom made and very pricey.
    Having had the 195mm for over a year now, what are your experiences with them, Are you still using them, have you extended further.
    I hear you, when it comes to things cycling not being made for anything over average size.
    It’s much the same for everything else over in the UK where I am. Seem about the only thing that fits off the shelf are underpants, most other things need to be looked for to get something anywhere near a long enough fit.
    Anyway I digress, I would be very interested in your finding on long pedals
    Regards,
    Macspud.

  • macspud said,

    Hello SuperClydesdale,
    I came across your post/site whilst looking for crank arms a bit more to my size, very hard/impossible to find unless custom made and very pricey.
    Having had the 195mm for over a year now, what are your experiences with them, Are you still using them, have you extended further.
    I hear you, when it comes to things cycling not being made for anything over average size.
    It’s much the same for everything else over in the UK where I am. Seem about the only thing that fits off the shelf are underpants, most other things need to be looked for to get something anywhere near a long enough fit.
    Anyway I digress, I would be very interested in your finding on long pedals
    Regards,
    Macspud.

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