Crank length
- Thread starter RAR
- Start date
JOSEPHWEISSERT
Zen MBB Master
My opinion: going from 170mm crank arms to 150mm crank arms is one of the best changes I ever made. I ride a V. I liked shorter cranks so much, I had a tool shop drill out my long cranks on my trainer bike also for winter training. The difference there was very noticeable and felt great as well. My X-seam is 42.5 inches. I could probably go down to 145mm or 140mm even, but I will have to experiment with that someday. In addition to short cranks, I switched to elliptical chain rings. I like them also. The combination of short cranks and elliptical chain rings is a good combination. You can search this forum for more information on crank length - there have been opinions expressed on both sides of the issue. But if you want to say "goodbye" to knee pain: 1) short cranks, 2) elliptical chain rings, 3) cadence around 90 RPM or higher most of the time. And you can run lower cadence a lot with no knee pain if you want to with short cranks and elliptical rings (60-70RPM). But I would recommend short cranks aside from knee pain because of better knee angle and better feel. The only disadvantage is your easiest gear will get a little harder because all your gearing will shift a little in the more difficult direction, so you might need to compensate by getting a bigger big cog in your cassette. This is due to a smaller distance traveled by your foot in a circle compared to how far your bike travels in one pedal revolution, and the force applied to the pedals. But this is a minor disadvantage and can be easily corrected if it is a problem at all - it might not be. This becomes an advantage in your biggest (most difficult) gear because you will go farther for the distance traveled by your pedals. So your biggest gear gets effectively bigger.
LarryOz
Cruzeum Curator & Sigma Wrangler
What Joe said.
I ride 140mm cranks now and have ridden many successful races and rides with them over the past year. T me it's all about sizing your crank to your leg length so you do not have too severe a knee bend on the back stroke. IMHO - that is what saves your knees all that pain!
I ride 140mm cranks now and have ridden many successful races and rides with them over the past year. T me it's all about sizing your crank to your leg length so you do not have too severe a knee bend on the back stroke. IMHO - that is what saves your knees all that pain!
DavidCH
In thought; expanding the paradigm of traversity
I gave myself a time trial on a 40 km loop with smaller cranks, I went down from 170mm to 165. I wanted to stick with Shimano Ultegra cranks as it's compatible with the Q Rings being used and that's the smallest they go. The rest of the money is going on race trim for the bike. Like new carbon race wheels and ceramic bottom bearings. I know the new handlebars (shorter than stock by 150mm) makes the bike more aero as my time has come down considerably and surprise ... not much knee pain either. So what I would like to know for next year... is it possible just to switch out Shimano cranks and put SRAM cranks in even though you are running a Shimano rear mesh (11 speed)? I have it on good authority that Q Rings loose their effect at around a crank length of 150mm and below, is that so?
ratz
Wielder of the Rubber Mallet
Yes you can run SRAM Cranks and a qring with a shimnao drive train.
You can not use shimano shifters with SRAM derailleurs nor sram shifters with shimano derailleurs as they use different cable pulls. SRAM is linear 1:1 shimano is not. Adapters can be added but over complicate things IMHO.
As of late you also can't mix SRAM shifters with shimano brakes. Forever the industry has used a 3:1 brake pull ratio. The awesome new shimano Slv brakes use 4:1 ratio. This happened when shimano rerouted their cables under the hoods. It will work but SRAM levers will feel over aggressive and lack touch on shimano brakes, and shimano levers on SRAM brakes will feel mushy. Some people will not notice or care, it depends on how you like your brakes. I will be testing SRAM levelers with ultegra 6800 rear brake on the new build I will let you know what I think.
As to shorter cranks. qRings shorten the time in the dead spot. By definition short cranks have a smaller dead spot. At some point if you tweak It right you won't feel the dead spot so you won't notice and improvement from the q ring it is still there but it becomes lessened at that point it is a cost benefit ratio question..high cost less gain. Personally I would probably run qrings down to 155mm, after that I would probably use praxis round rings.
Also on short cranks you can use the power tap C ring based power meter. That is about the best option on short cranks as most of the other pedal based meters don't work below 165mm or are not GXP compatible. So for about the cost savings from not adding q rings you get a power meter and the benefit of the short cranks.
With these upgrades if you plan to do them over 18 months it is best to figure out your end configuration so that you don't add parts you will have throw away latter.
trplay
Zen MBB Master
Oh no, here we go again. Q rings and the claim as the magic solution to biking! I believe these rings have been around since the 1800's, but am too lazy to look it up. I first saw these warped rings back in the 1970's. back then they were claiming all chain rings would soon look like this. It didn't quite work out like that but every ten years or so you see their rebirth in another repacking format. They usually cost more and come with even greater claims. Yes, I'm skeptical but in this case I think the Team Moose rule #12 applies. Rule 12 states "don't believe anything you read on the internet." Yes, this means ignore my skepticism also. These rings do seem to help some people, so the trick becomes matching those people with those rings and you get a winner--ding-ding! The high costs of these rings has made this a pretty risky endeavor but my dear friend Tiger Paw has solved this problem for the curious rider. He provided the the link to Doval rings made in Korea (Here) . You can buy a set for around forty bucks and try them for yourself. His set is shifting fine on SRAM cranks and yes they do appear to give him a boost. Not only that but they look good which might be the most important aspect anyway.
LarryOz
Cruzeum Curator & Sigma Wrangler
My Garmin Pedals are configurable with cranks down to 110mm.
There are known problems with Q-rings and crank or pedal based power meters - i.e. not reporting exactly the right power - I have confirmed this in testing. It's not much - just a few %, but it is consistent.
My X-seam is about 40.5"
Not magic - but maybe something.....
As far as the merits of Q-rings: I have tried many different way to either prove or disprove the claims.
Then it occurred to me that you will never be able to really detect "more" or "less" power going to the wheel when comparing Q-rings to round rings, or any other kind of rings for that matter.
It is all a subject "feel" that you have when you are pedaling.
Like Moose said: some people claim great things (like less knee pain, etc). It you feel they help you - then use them.
At this point, I believe after all my testing that there is some non-quantifiable benefit to them so I'll keep using them.
JOSEPHWEISSERT
Zen MBB Master
Regarding any effect from elliptical rings, the experience that convinced me (that there is an effect from the elliptical rings) was when I rode with 150mm cranks and with the elliptical rings slightly out of tune. When I got home and got off the bike, I went up the stairs and it was as if I had been doing squats with a barbell on my back for the entire ride. Then my legs were sore the next two days. Very odd since I ride a lot and that never happens. So it seems safe to assume there is also an effect, although positive, when using 150mm crank arms and properly tuned elliptical chainrings.
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DavidCH
In thought; expanding the paradigm of traversity
Well that's good news because I sure don't feel that. Joe, did you post a picture of your new cranks?
JOSEPHWEISSERT
Zen MBB Master
Yes, there are two pictures of the bike and its cranks in this post: http://cruzbike.com/forum/threads/vendetta-winterizing.9193/#post-116095
JOSEPHWEISSERT
Zen MBB Master
ratz
Wielder of the Rubber Mallet
This thread can get you up to speed on the topic.
http://cruzbike.com/forum/threads/q-ring-upgrade-ahhhhhhhhhhhhh.7784/
My experience with Q-rings is limited to DFs and it was only for about a dozen or more rides. You are describing nearly identical effects I felt especially after the first few rides coupled with persistent knee pain in my left leg. The chainrings were properly set up on the bike.
From what I read around the web on cycling sites and Rotor's own literature, it is apparently normal to experience some muscle soreness or discomfort at first. I would have been surprised if there was no difference because leg muscles are being used differently from standard round rings. Muscles will adapt and then there should be no soreness. Same thing occurs to a body builder when trying new exercises that isolate different muscle groups, soreness at first then adaptation.
Even though I had muscle soreness and nagging left knee pain, I continued to use the Q-rings against my better judgment because I found them to be much more efficient, pleasurable to use and my speed went up, especially acceleration. Front shifting was even improved, strangely enough. I never tried them on a recumbent and many bent riders claim oval rings yield more benefits on a recumbent, so I'm looking forward to using them on my Vendetta.
marshall2389
Guru
An effective pedal stroke will actuate the pedalers ankles, knees, and hips through acceptable ranges. Too short and you're spinning your feet wildly in circles devoting all your energy to changing the momentum (accelerating) your legs instead of putting power to the pavement. Too long and your knees and hips bend so much you lose leverage (crouch down low so your butt gets close to the ground (large joint angles) and see how hard it is to stand back up). The exact ranges of angles that works well with your body takes experience and fitness. When choosing crank length keep these things in mind:
- Your x-seam. Longer legs means longer crank length.
- Hip angle. More closed hip angles produce greater power from lower cadence and longer cranks.
- Ankle actuation. The more you point your toes at the end of the stroke the longer crank is needed for bending of other joints. In my experience I point my toes much more with a clipless setup (as compared to platform pedals).
snilard
Guru of hot glue gun
Mr. Ratz, are Your sure that PowerTap C will clear V's BB clamp?
ratz
Wielder of the Rubber Mallet
That's a good question. It should; the Power2Max one does and they are very similar on the back side design; from photo graphs the PowerTap C looks to have a slightly bigger opening; but I'm guessing a quick email to them would confirm the inside diameter. The Power2Max ones are Spindle specific so they designed tight to the 24mm bearing cups. Since the PowerTapC is spindle agnostic they had to account for BB30 external cups without screwing up the Q factor. Hence I doubt there will be a problem .... but until someone tries it....
Point of detail thought; the Yellow V's the clamp was bigger and I had to get cut with the left right offset by 2mm to get it to work; on the the new V20's the clamp is more refined and I had no fit issue there is a good 1.5mm clearance which is fine for such things. On the Silvo's there is a massive amount of clearance.
snilard
Guru of hot glue gun
What BCD do You have?
