Where to buy cheap short crankset

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Where to buy cheap short crankset

Postby vosadrian » Tue Aug 28, 2018 11:00 am

Hi All,

I have an older commuter bike that came with Ultegra 6600 and is still 10 speed. Currently I am running a 6800 52/36 crankset at 172.5mm crank length. I want to try out shorter cranks in an attempt to see if it benefits general pelvic and back pain I experience by opening my hips up, but I don't want to spend a fortune to trial this. Easiest to get is R8000 crankset at almost $300. I might not like the shorter cranks, so ideal would be to find some shorter cranks from someone else who changed them... or some lower series new crank arms.

Can anyone recommend where I can find something cheap to try?

Thanks!

User avatar
MichaelB
Posts: 14775
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: Where to buy cheap short crankset

Postby MichaelB » Tue Aug 28, 2018 2:23 pm

What is the definition of 'short' ?

165mm ?

Doesn't the new R7000 come in 165mm ?

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Tue Aug 28, 2018 3:25 pm

MichaelB wrote:What is the definition of 'short' ?

165mm ?

Doesn't the new R7000 come in 165mm ?
Ideally I want 165mm crankset in 52/36. I have 6800 172.5 cranks at the moment, so could get cranks with different/no rings in 6800 and put my current rings onto it.

R7000 seems to come in 165, but it is hard to find and where I find it, it is almost as much money as R8000. Probikekit have R8000 165mm 52/36 at around $250. I was hoping to find some runout older cranksets like 67/6800 or 57/5800 but I have not had much luck and it has not been that cheap when I did find it. Probikekit seem to have a silver 5800 for around $150 (my preferred black is about $165). Was originally thinking a budget of $100-150 to try it out, so that would do... or maybe spend the extra $100 in case I like it and want to keep it for the R8000?

This is for my commuter. If I like it I would want to change my other bike which is Specialized FACT carbon cranks... going to be an expensive exercise to change that. Might get a BB converter and change to R8000. That is why I will try it on the cheaper bike that I ride more.

User avatar
MattyK
Posts: 3252
Joined: Fri Oct 01, 2010 1:07 pm
Location: Melbourne

Re: Where to buy cheap short crankset

Postby MattyK » Tue Aug 28, 2018 4:04 pm


skyblot
Posts: 282
Joined: Tue Sep 22, 2009 8:52 pm
Location: Brisbane

Re: Where to buy cheap short crankset

Postby skyblot » Tue Aug 28, 2018 7:52 pm

Remember if you go to shorter cranks, you will have to raise your saddle to account for the pedal being closer (AT) bottom dead centre. And how this will effect your riding position re the handlebars.....

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Tue Aug 28, 2018 9:21 pm

Thanks guys.

Yeah, I realise about the change in fit... that is why I am doing it. Plan to put the saddle up the same amount as the cranks is shorter (as a starting point). Hoping that opens up my hips a fair bit when I am in the drops and eases pressure on my lower back.

User avatar
Duck!
Expert
Posts: 9857
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: Where to buy cheap short crankset

Postby Duck! » Wed Aug 29, 2018 9:17 am

Sora is available in 165mm for a nice cheap option, but not with 52/26 rings (I don't think that combination is available below 105 yet). That said, all the 4-arm cranks use the same bolt pattern, so you can swap the rings, they just won't look pretty.
I had a thought, but it got run over as it crossed my mind.

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Wed Aug 29, 2018 11:11 am

Thanks all!!

I have done more research on the 165 crank option and I cannot see any negative to going for it on my commuter. All reports I see of people going to shorter cranks seem to be positive and I don't see any negatives. Maybe I will lose some power or something, but for my commuter bike, comfort is key and power not a big deal. I ride the bike about 150k a week and daily (morning and afternoon), so anything that can reduce aggravation of my inflexible and tight back will be a benefit. I am currently on 172.5 cranks, so changing to 165 should increase saddle height by 7.5mm and should reduce the knee height (which touches my chest when on drops) by 15mm. So I think it is unlikely I will want to change back.

That being the case, and the fact I can't see any cheap options below $150, I am just going to get the R8000 setup for only $100 more. If I went the cheap option I would want to change to better later to match my black bike.

The issue will be for my good bike which has the Specialized FACT carbon cranks. Also I have vector 1 pedals with the wider pods to suit the wider cranks. I am not sure if I have to replace the vector pods if I get a narrower crank. So the options I see are:

* Buy replacement arms from Specialized with a list price of $750 (but none in stock)... job done.

* Buy some R8000 cranks with rings ($250). Buy a hollowtech BB conversion for OSBB (~$100). Buy replacement Vector Pod for RHS (~$100)

Second option makes more sense... but I like my carbon cranks!!

User avatar
MattyK
Posts: 3252
Joined: Fri Oct 01, 2010 1:07 pm
Location: Melbourne

Re: Where to buy cheap short crankset

Postby MattyK » Wed Aug 29, 2018 11:55 am

I'm sure if it fails (which I doubt it will) you'll have no problem moving on short cranks to the triathlon crowd, where they are the new hotness.

If you need carbon, Cobb makes some very short options:
https://speedandcomfort.com/collections/cranks

Keep us updated on how it goes; I'm pondering the same if I update my groupset as my bike gets dual road/tri use.

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Wed Aug 29, 2018 2:29 pm

I will keep you updated. I don't expect it to be a miracle cure to my back issues but if I can ride for longer before the back gets unbearable, that would be great.

I like the looks of the Praxis cranks (which are available in 165) which seem well priced:

https://praxiscycles.com/product/zayante-carbon/

But it is hard to go past Shimano for durability, low noise and shift quality. My Ultegra (mixed series) on my old commuter is much quieter and smoother than my Ultegra 6800 with Praxis rings on Spec cranks on my good bike.

User avatar
Duck!
Expert
Posts: 9857
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: Where to buy cheap short crankset

Postby Duck! » Wed Aug 29, 2018 9:04 pm

skyblot wrote:Remember if you go to shorter cranks, you will have to raise your saddle to account for the pedal being closer (AT) bottom dead centre. And how this will effect your riding position re the handlebars.....
vosadrian wrote:Thanks guys.

Yeah, I realise about the change in fit... that is why I am doing it. Plan to put the saddle up the same amount as the cranks is shorter (as a starting point). Hoping that opens up my hips a fair bit when I am in the drops and eases pressure on my lower back.
Very valid point about the handlebars, especially given the reason for trying the shorter cranks is back pain. The adjustment of seat height to maintain proper leg extension will increase the handlebar drop, placing more demand on hip & spine flexibility. You will need to raise the bar by the same amount to maintain your posture geometry.
I had a thought, but it got run over as it crossed my mind.

User avatar
MattyK
Posts: 3252
Joined: Fri Oct 01, 2010 1:07 pm
Location: Melbourne

Re: Where to buy cheap short crankset

Postby MattyK » Wed Aug 29, 2018 11:10 pm

...to maintain your back angle yes.

But not to maintain your hip angle (relative to the knee at top dead centre). This angle will have opened up more.

Basically it's a big can of "it depends"...

Nobody
Posts: 10316
Joined: Thu Sep 18, 2008 12:10 pm
Location: Sydney

Re: Where to buy cheap short crankset

Postby Nobody » Thu Aug 30, 2018 8:27 am

Other issues are the saddle needs to go also back to maintain same position at point of maximum effort. So stem might feel too long after change. Gearing goes up. It should feel too short out of the saddle. This feeling for me lasted a long time and has made me consider trying 170s at times. It was a lot of mucking around to get right in the end, which changed the fit for three bikes. Certainly more changes than I thought I'd have to do. Although of minor benefit, I think it was worth the change for me in the end. Especially considering we all get older. My first bike was changed over 10 years ago.

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Thu Aug 30, 2018 11:33 am

I have done a little research and I am expecting to have to fiddle with the fit to get it right.

The issue for me is that I have pelvic and back pain. It is worse when in the drops. I find myself wanting to shift forward on the saddle to alleviate which I think is my way of opening up the hip angle. I also note that the top of my thighs slightly touches my chest when low on the drops. I am proportionately shorter legged and longer bodied. As a result, my saddle height is not that high compared to others around my height and my chest gets close to my thighs because of this which is basically indicating I have fairly acute angle at the hip at the top of the pedal stroke.

A reduction of 7.5mm in crank means that I lift the saddle around 7.5mm to get the same knee angle at the bottom of the pedal stroke. Additionally it means my knee goes 7.5mm less high at the top of the stroke. If my back angle stayed the same (lift bars by same a mount as saddle), I gain 15mm clearance between knee and chest which equates to an increase in the hip angle. Even if I don't raise the bars, I gain atleast half of that... If my chest stays in the same place, my knee is raising 7.5mm less high towards my chest (and my chest is actually higher since the saddle is raised by 7.5mm).

So I am confident that my hip angle will increase. I have tight hamstrings so tend to curve in my lower back which seems to cause my back pain. Hopefully not bending the hips as much will allow the hamstrings not to reach end of range and allow me to be more neutral in the lower back.

Nobody... I am not understanding how the gearing changes? My understanding is that most people tend to set cadence based on perceived foot speed. When you reduce the crank length, the foot speed goes down (at the same cadence), so people tend to pedal higher cadence to get to the same foot speed. Also, you need to apply more force on shorter cranks to get the same power at the same cadence. I think people tend to adapt by running a gear shorter than they would have before which gives them similar power by pushing same force at a higher cadence. So technically I thought it would make the gearing feel longer... not shorter as you report? I run 52/36 with 11-28. Plenty of gearing range there, and I rarely need the 36-28, so happy for it to feel a little longer.

User avatar
MattyK
Posts: 3252
Joined: Fri Oct 01, 2010 1:07 pm
Location: Melbourne

Re: Where to buy cheap short crankset

Postby MattyK » Thu Aug 30, 2018 12:32 pm

On your last point, there's a whole lot of biomechanics at play.
shorter cranks = lower muscle contraction speed, which probably (I'm not a physiologist) gives the ability to apply more force on the pedal.
Lower inertia in the leg too, so (maybe?) less energy wasted just rotating your legs in circles.
Decreased range of motion = muscles stay in a more efficient/effective position to apply force (not overextended).

And so on. (The above is all purely speculative, however there's reasonable evidence that crank length doesn't impact power unless taken to extremes)

Nobody
Posts: 10316
Joined: Thu Sep 18, 2008 12:10 pm
Location: Sydney

Re: Where to buy cheap short crankset

Postby Nobody » Thu Aug 30, 2018 12:39 pm

vosadrian wrote:Nobody...So technically I thought it would make the gearing feel longer... not shorter as you report? I run 52/36 with 11-28. Plenty of gearing range there, and I rarely need the 36-28, so happy for it to feel a little longer.
I said:
Nobody wrote:Gearing goes up.
Or gets longer as you describe.
It's as simple as the ratio of crank length to the chainwheel radius from the chain to the BB. That ratio decreases, so everything feels a bit harder to push as the chainwheel has effectively grown in reference to the crank. I dropped my chainwheel by 2 teeth after the change.

IIRC I dropped the chainwheel size as I was cross chaining too much into the lower gears on the rear after the change.

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Thu Aug 30, 2018 3:13 pm

Thanks for that.

You indicate it feels shorter out of the saddle. Did you mean longer?

I was particularly interested in out of the saddle differences. I figure that for seated riding you can just select a gear that achieves a comfortable cadence/foot speed and pedal force for the riding you are doing (within the limits of your gearing). But for standing in a sprint, I imagine the reduction in crank movement would effect the way the bike is thrown from side to side and may have effects on sprinting power. Not sure if much effect on standing climbing.

Nobody
Posts: 10316
Joined: Thu Sep 18, 2008 12:10 pm
Location: Sydney

Re: Where to buy cheap short crankset

Postby Nobody » Thu Aug 30, 2018 3:40 pm

vosadrian wrote:You indicate it feels shorter out of the saddle. Did you mean longer?
No, the out of the saddle experience hasn't got much to do with the gearing for me. It's 1cm shorter pedal to pedal. I feel it most out of the saddle for some reason. Although after 10 years I'm fairly used to it now. My ideal would be 165s seated and longer cranks standing. I ride just for exercise, so do all my hills out of the saddle. Maybe try someone else's bike if you can find one, before you buy.

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Thu Aug 30, 2018 4:42 pm

Nobody wrote:
vosadrian wrote:You indicate it feels shorter out of the saddle. Did you mean longer?
No, the out of the saddle experience hasn't got much to do with the gearing for me. It's 1cm shorter pedal to pedal. I feel it most out of the saddle for some reason. Although after 10 years I'm fairly used to it now. My ideal would be 165s seated and longer cranks standing. I ride just for exercise, so do all my hills out of the saddle. Maybe try someone else's bike if you can find one, before you buy.
I get you now... not shorter in gearing. I imagine out of the saddle would feel different if you were not moving your legs as much... maybe no need to move the bike as much. I like to have a good kick in a sprint, so will be interesting to see how that works out.

Parts are on the way, so I am doing this. I would not be confident I could get a good idea if it would benefit me without riding it for a month or two and fiddling with fit to get it right. From reviews of people who have done it and also blogs from bike fitters, it seems there is nothing to lose and something to gain if you not very flexible like me. I can always sell the parts if it does not work out.

User avatar
Duck!
Expert
Posts: 9857
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: Where to buy cheap short crankset

Postby Duck! » Thu Aug 30, 2018 7:41 pm

MattyK wrote:...to maintain your back angle yes.

But not to maintain your hip angle (relative to the knee at top dead centre). This angle will have opened up more.

Basically it's a big can of "it depends"...
Back angle and hip angle are very closely linked when triangulated (or more correctly, quadrangulated, including shoulder position) against the handlebar position. Obviously we're seeking to maintain the relative position between pedal at bottom dead centre and saddle. Shifting that plane upward while leaving the bar untouched will reduce - tighten - the hip angle at BDC. The shorter crank may still open the hip angle at TDC relative to the current position, but not as much as could otherwise be achieved. Maintaining the contact point geometry at BDC by also raising the bar the same amount will maximise the opening of hip angle at TDC made possible with the shorter crank.
I had a thought, but it got run over as it crossed my mind.

User avatar
Duck!
Expert
Posts: 9857
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: Where to buy cheap short crankset

Postby Duck! » Thu Aug 30, 2018 8:10 pm

vosadrian wrote: Nobody... I am not understanding how the gearing changes? My understanding is that most people tend to set cadence based on perceived foot speed. When you reduce the crank length, the foot speed goes down (at the same cadence), so people tend to pedal higher cadence to get to the same foot speed. Also, you need to apply more force on shorter cranks to get the same power at the same cadence. I think people tend to adapt by running a gear shorter than they would have before which gives them similar power by pushing same force at a higher cadence. So technically I thought it would make the gearing feel longer... not shorter as you report? I run 52/36 with 11-28. Plenty of gearing range there, and I rarely need the 36-28, so happy for it to feel a little longer.
Nobody wrote:
vosadrian wrote:Nobody...So technically I thought it would make the gearing feel longer... not shorter as you report? I run 52/36 with 11-28. Plenty of gearing range there, and I rarely need the 36-28, so happy for it to feel a little longer.
I said:
Nobody wrote:Gearing goes up.
Or gets longer as you describe.
It's as simple as the ratio of crank length to the chainwheel radius from the chain to the BB. That ratio decreases, so everything feels a bit harder to push as the chainwheel has effectively grown in reference to the crank. I dropped my chainwheel by 2 teeth after the change.

IIRC I dropped the chainwheel size as I was cross chaining too much into the lower gears on the rear after the change.
Another angle to look at it by..... For a given linear leg speed, a shorter crank will cause the pedals to scribe a greater arc of the crank's rotation than a longer crank -> greater rotational speed -> higher cadence for the same leg speed. Gearing is entirely related to rotational speed, so a higher cranking cadence will correspondingly increase wheel speed, therefore your speed over the ground. As noted above, the shorter crank places the pedal closer to the chainring, reducing your leverage. These factors conspire to make the gearing feel harder, hence the suggestion for some gear correction. With appropriate gearing, shorter cranks are easier to spin up to higher cadence, which comes back to the first point about linear speed and cranking arc.
I had a thought, but it got run over as it crossed my mind.

CKinnard
Posts: 3459
Joined: Mon Jun 30, 2014 10:23 am

Re: Where to buy cheap short crankset

Postby CKinnard » Thu Aug 30, 2018 8:47 pm

Adrian, you have to ensure you understand where the main pain is coming from.

If it is your lower back, then shorter cranks and raising the saddle are not the solution.
All you have to do to explore greater comfort is raise the stem. This will decrease back angle, or flexion in lower lumbar segments. If that doesn't work, try a shorter stem.

If the pain is more so in the hip JOINTs, then yes you would be better off with shorter cranks to reduce flexion ROM in hip joint.

If it is a combo of lumbar and hip joint pain, then that's another post.
Based on our previous interactions, I'll put my money on it being a lumbar disc/stenosis issue.

vosadrian
Posts: 1176
Joined: Fri Mar 22, 2013 4:58 pm

Re: Where to buy cheap short crankset

Postby vosadrian » Fri Aug 31, 2018 11:09 am

CKinnard wrote:Adrian, you have to ensure you understand where the main pain is coming from.

If it is your lower back, then shorter cranks and raising the saddle are not the solution.
All you have to do to explore greater comfort is raise the stem. This will decrease back angle, or flexion in lower lumbar segments. If that doesn't work, try a shorter stem.

If the pain is more so in the hip JOINTs, then yes you would be better off with shorter cranks to reduce flexion ROM in hip joint.

If it is a combo of lumbar and hip joint pain, then that's another post.
Based on our previous interactions, I'll put my money on it being a lumbar disc/stenosis issue.
Thanks for the info guys!!

CKinnard, when riding my main pain is lower back. It increases when I bend forward more in the drops (but will still arrive a little later even when on the hoods or bars), and is alleviated (for a short while) by stretching (arcing) my back when coasting down a hill. It seems to be related to having my back in constant flexion when riding. Having said that, I get a variety of pelvic pain (groin, glutes, adducters) issues that are aggravated by riding (felt after riding for a day or two), but don't really cause any major pain when on the bike (but necessitate more rest after a ride than I used to do).

Changing the cranks is not about fixing my issues. It is just an attempt to maximise comfort on the bike so I can do what I enjoy despite my issues. If riding were the cause of the issues they would go away when I stop for 3-6 months which I have done several times with no real improvement other than the aggravation during/after a ride not being there. For me riding is about riding fast in fast bunchs or solo and pushing my limits. I could buy a flat bar and set it up so I am sitting with a straight back but I think I would lose interest in that quickly. So the current effort is about making changes that can benefit my comfort to keep me doing what I love whilst dealing with these issues.

One theory I have is that my tight hamstrings result in me bending more with lower back flexion than at the hips. The more acute the hip angle, the tighter the hamstrings, and the more back flexion. Short cranks should reduce this effect. It is just a theory and this whole exercise is just a test really. It might be a waste of a couple hundred dollars.

My brother (who is taller than me) recently got a new bike and got a fit done. The fitter suggested 165 cranks and an SMP saddle which he did. They then fitted to the new bits. He is more comfortable than he thought possible on a bike. He is performing better than ever in terms of power output and climb PRs. The fit was radically changed from his previous fit that was not done by a proper bike fitter. In truth, the 165 cranks are probably only partially responsible (and may not have any effect), but this does say to me that short cranks do not negatively effect comfort or performance. I am confident I will not experience problems from going to short cranks.... but I may not experience any benefit to my issues either.

User avatar
MattyK
Posts: 3252
Joined: Fri Oct 01, 2010 1:07 pm
Location: Melbourne

Re: Where to buy cheap short crankset

Postby MattyK » Fri Aug 31, 2018 2:31 pm

The other item to consider is a different saddle with a cutout or noseless that allows you to rotate your pelvis forwards more. Should help minimise arching your back.

CKinnard
Posts: 3459
Joined: Mon Jun 30, 2014 10:23 am

Re: Where to buy cheap short crankset

Postby CKinnard » Fri Aug 31, 2018 6:37 pm

vosadrian wrote: CKinnard, when riding my main pain is lower back. .
Yep, I understand cycling isn't the cause of your issues, but does irritate them.
Your lumbar spine symptoms are likely to remain sensitive to your back angle despite what you do with cranks...though with aggressive core and superficial trunk mm strengthening, and glut and hams stretching, could ease more than either of us think.
The other symptoms you talk of (groin gluts adductors) will likely benefit from shorter cranks.

As for shorter cranks, and your brother's experience, I am 186cm, inseam 88.5cm....and own 170, 172.5, 175 cranks. I have felt most comfortable and feel I perform better with the shortest. Also, mountain bikers, BMX, and track cyclists use shorter cranks, relatively.
I am open for individuals to trial a range of crank lengths and use whatever feels better. There's so many variables that impact comfort and power generated.
Generally, as one ages, I think there's benefits to shorter cranks because it reduces the range of motion of arthritic knees and hips, and stiffer scarred and weaker hamstrings and quads.
Also, visceral fat reduces pedaling circumference comfort.
And external iliac arteries and veins do not kink as severely with a shorter crank. These are prone to endofibrosus and scarring in a few.

Something I didn't consider previously.
In favor of you experimenting with shorter cranks for your low back symptoms, your hip joints will flex less....and it is possible some nerves of the lumbar and sacral plexi will be tractioned less so. This may reduce irritation of some neural and adjacent tissue in the lumbar spine.....and therefore reduce low back symptoms.

You may also benefit from the higher cadence on the shorter cranks (less peak load through the lower limb muscles.)

Who is online

Users browsing this forum: No registered users