Archive for the ‘Cranks and BBs’ Category
Crank clearance with pedal Extenders
Follow on to Knee Savers First Impressions
I have been riding a few months now with Knee Savers and Shorter Cranks and have to say that the results have so far been all positive.
The Knee Savers/Pedal Extenders keep my feet from rubbing the crank arms and give me more ways to position my feet while riding. They also allow a lot more toe out which I seem to need for my right foot.
This is a follow on from Short Cranks First Impressions.
Short cranks so far have turned out better than I expected. I wasn’t sure that there would be a noticeable effect. But I was wrong.
I expected the improved spin but also expected to lose some climbing Torque. My climbing torque seems to have improved and my spin is definitely better. I seem to be spinning faster and climbing hills easier with more kick as I get towards the top.
The big surprise is that the shorter cranks seem to have improved the load balance on my legs. I have had three surgeries on my left knee and my right leg is much stronger than the left. The combination of shorter cranks and spinning faster seems to work my left leg more. Yes, my left leg is showing the signs of working harder, more muscle soreness and an occasional cramp. But I think that is a good thing and may explain why I am climbing better.
Special thanks to:
5349 Elliot Ave S
Minneapolis MN 55417-1741
Mark helped me pick out the right cranks for me. He was very patient and helpful whenever I had a question plus he did some nice work on the cranks.
So far my feeling is that I should have gotten Short Cranks earlier and that short cranks are one of the best improvements you can make on a LWB recumbent.
5/12/09 Update: I can’t recommend this idler kit for the Slipstream. I have done a bit of riding with them now and have to say I am not impressed. The concept is good but the reality is increased noise and an idler that doesn’t seem to follow the chain line very well. This is an expensive upgrade without significant benefits.
TerraCycle offers a Longbikes Slipstream Idler Kit that looks very nicely made. It replaces the rubber idlers seen on most recumbents with coged idlers that have high quality bearings. TerraCycle claims that the better idlers provide improved efficiency and quieter operation. This improvement is not inexpensive, $154 for the kit.
I agree with TerraCycle’s explanation of why good quality idlers are important but I am not sure how noticeable the improvement will be for most riders. I have ordered a Kit and will document my experience.
The kit is not easy to find at the TerraCycle web site, the link above will save you time finding it.
(more description of the kit and TerraCycle’s explanation of why high quality idlers are important follow)
I have my new shorter cranks but so far haven’t been able to get the Shimano HollowTech II cranks that I am replacing off. Every time I start this job I find that I am missing another tool. Here’s a nice set of instructions with a tool list so you won’t have the same problem.
Just be sure you have all of the tools they list as required before you start.
I have removed mine and it was as simple as the video shows once I had the tool to remove the caps. This is a beautifully designed set of cranks that is extremely easy to work on. I just wish they came in shorter lengths for recumbent riders.
Thanks to the folks at enduro fork seals .com for a very nice set of instructions.
If you are replacing your crank arms with shorter cranks this video shows you how. Don’t forget you will need a crank puller, the standard tool is a Park Crank Puller.
I have been investigating steps needed to install my short cranks when they arrive. Here’s how the UN54 68/115 (or 118) BB for the Slipstream will install.
Make sure you have the special tool needed to install the BB before you start. I use a Park BBT-2 Bottom Bracket Tool for Splined Bottom Brackets.
macpublish suggested in yesterday’s comments that I consider Q-Rings if I am changing cranks. I rode Shimano Bio Pace in days of old so really haven’t paid much attention to Q-Rings, the stories sound the same to me.
Continued from Are your crank arms too long?
Ok, I have decided that I want to replace the standard 170 MM cranks on my Slipstream with 155 MM cranks more appropriate for my Hobbit legs.
So I Googled and found almost nothing. Looks like the shortest commercial Road and MTB cranks are 165 MM. There are 155 MM and shorter cranks out there but they are BMX cranks and cranks for kid’s bikes. None of those are drilled for a Triple Chain Ring. There is no way I can give up my Triple.
Note: There is some feedback that calculated lengths using this tool are too long (3 MM from feedback). I would not take the calculated lenghth too literaly and lean toward shorter lenghts. I also think that recumbent riders should consider shorter cranks because of seating position.
I have been thinking that I should shorten my crank arms since I started having hip problems but I am not sure that the effect is significant. However, I do know that it will be expensive. A friend is going to let me ride his recumbent with shorter cranks before I proceed but I am prettty sure I will make the change.
So if I do change “What is the correct crank arm length?”.
Well to answer that question I found a neat little web page, Optimum Crank Arm Calculator.
This program by Machine Head Software calculates the optimum crank arm length base upon the riders inside leg measurement. This approach is based upon the technique is from The Racing Bike Book, By Dave Smith, Ben Searle & Steve Thomas (foreword by Sean Kelly), ISBN 1-85960-319-X. The book gives a table of recommended crank sizes in millimeters for inside leg measurements between 72 and 96 centimeters.
From this table of values the following relationship was developed:
Recommended crank length in millimeters = (1.25 * Inside Leg in cm ) + 65
I tried it out and with my very short for my height legs (29″ inseam) it recommends 157 mm cranks instead of the 170 mm I am using now.
See Cranks for more postings about Shorter Crank Arms, where to get them, how to install and remove cranks and Why I love them.