Mismatched crank lengths

[Eldron]

15 minutes ago, dexterdent said:

That's how I understand it as well, as my horrible powerpoint drawing hopefully shows:

 

 

 

27 minutes ago, PeterF said:

This will maybe solve the problem at the bottom of the pedal stroke but won't it compound the problem at the top of the pedal stroke?

It will indeed.

The graphic is wrong though - the 175mm crank will effectively be 172.5mm at bottom dead centre and 177.5mm at top dead centre.

Practically it shouldn't affect much as meaningful power only starts at around the 2-3'o'clock position.

It is all theoretical though - I would not recommend anyone doing this!

 

[Eldron]

2 hours ago, Shebeen said:

are you legs the even same length to start with?

It might be 40-70% in total but I have only found LLDs significant enough to require intervention in less than 10% of my clients.

I'd guess the other 30-60% is in the less than a few mm range.

[DieselnDust]

12 minutes ago, Eldron said:

 

It will indeed.

The graphic is wrong though - the 175mm crank will effectively be 172.5mm at bottom dead centre and 177.5mm at top dead centre.

Practically it shouldn't affect much as meaningful power only starts at around the 2-3'o'clock position.

It is all theoretical though - I would not recommend anyone doing this!

 

 

but wait wait wait.....

are you saying oval chainrings are better than an oval pedal stroke....??

 

hat 

coat

door

[Sepia]

Ok, I read all this.  But my problem is that my one leg is actually 22mm shorter than the other or the other leg is longer than the other by the same amount (Hip injury)

Would different crank lengths help in this case when the difference is in the hip area?

[DieselnDust]

2 minutes ago, Sepia said:

Ok, I read all this.  But my problem is that my one leg is actually 22mm shorter than the other or the other leg is longer than the other by the same amount (Hip injury)

Would different crank lengths help in this case when the difference is in the hip area?

it might but you should use a physio to help you make the correct adjustments as saddle displacement may also be required

[TNT1]

Wait a minute, can't the OP get those new fangled biopace chainrings, rotor or whatever, and set them up so that his legs would effectively be the same length?

[dexterdent]

Wouldn't a non-round chainring have zero affect on your foot travel-circle/oval?

 

wait I think I get the joke now.

[PeterF]

17 minutes ago, dexterdent said:

Wouldn't a non-round chainring have zero affect on your foot travel-circle/oval?

 

wait I think I get the joke now.

Please don't encourage DieselnDust.😁

[eala]

Other than riding in circles i don,t think it will make a difference 

[Knersboy]

Everyone is always so mean to Biopace. Meanwhile it was a training device that actually made one stronger by making your gear bigger around the pedal dead spot.
 

Because a 42-23 smallest gear was too easy for us back in the day when gravity was weaker.

[NotSoBigBen]

Just as a matter of interest how much do you honestly ride per week?

As a layman I would imagine you have to do quite a lot of riding before developing a debilitating injury ... just a thought

[Jewbacca]

Why would one get injured? 

One leg would just get used to a slightly smaller revolution. It's not as if the pedal is going to be skew or wobbling about or forcing the knees in any sort of strange angle.

I'm pretty sure a lot of us ride their saddle 2.5mm too high or too low, so IMHO if you make sure your cleat position is good, drop your saddle height by 1.25mm then you will be fine ish.... I mean, I wouldn't do it forever, but I genuinely don't see how one would develop an injury. 

 

[dexterdent]

I think it ends up being a risk/reward thing. It's not going to cost me that much to get a new power meter after selling the shorter one, and someone will get a nice deal on an almost new perfectly working one. That would have been the medium term plan anyway (the engineer in me struggles with purposefully unbalancing a load like that) but was really thinking how nice it would be to have some power data to prove to my friends that my slower CTCT time is due to wind and not lack of effort.

The alternative is that I might or might not cause some permanent damage, and on the balance of this thread I'm not sure of the likelihood of that, but I am sure that it's definitely possible.

I'm also very aware that the power meter is mostly just a fun bit of data analysis I get to play with after some rides, and not really adding any specific value to my riding (which is about 6 hours a week, lets say half on zwift).

This is the answer I got to for me, and I'm sure that someone else, looking at the same responses, might get to another answer. That's cool too, please report back on your results so we can add to the collective knowledge when another person googles this kinda niche problem.