Short cranks !

[Gringo]

Hi folks, the benefits of short crank arms has been discussed many times over the years.
I personally use 155mm crank arms because of restrictions in my knee movement, 155 vs 175mm =40mm reduction between straight leg and fully bent knee.
The biggest problem with short cranks is that in order to get full leg extension you raise the seat, this in turn increases the ride height and reduces your ability to put your foot flat on the ground. as an engineer I overcame this issue by making a pedal adapter (also known as pendulum pedals) these places you’re foot closer to the ground and mean you don’t need to raise your saddle ps I have these on 4 of my bikes
To make these I would have to buy sacrificial pedals for the spindles, bearings and billet aluminium, plus several hrs work.
Anywho, completely by accident on Alie Express I came across the exact same thing only advertised for a different reason (Effort Saving adapter)
iv included a picture of what I’ve made and the AlieExpress version. https://www.aliexpress.com/item/1005001812449698.html?spm=a2g0o.order_list.order_list_main.16.18751802eOfSGT

 

[Az.]

You don't have problems with crank length while cornering?

 

[flecc]

Hi Gringo,

Cycle engineers Highpath Engineering have for many years made these swing cranks in Britain. LINK
.

 

[Gringo]

Hi Gringo,

Cycle engineers Highpath Engineering have for many years made these swing cranks in Britain. LINK
.

Indeed they have but £300 is a little more than most would be comfortable paying. £17 on Alie is affordable

 

[Gringo]

You don't have problems with crank length while cornering?

You would have a problem if you fitted them to your original crank arms but not if you’re using shorter arms

 

[Az.]

Hi Gringo,

Cycle engineers Highpath Engineering have for many years made these swing cranks in Britain. LINK
.

These are different.

I would say Highpath Swing Cranks are better for people with bad knees.

 

[Gringo]

These are different.

But do the same job

 

[Az.]

But do the same job

No

 

[Gringo]

No

Yes

 

[Az.]

Yes

No LOL.

On Highpath crank rotation circle is much smaller.
On yours rotation circle is the same (as it would be on cranks without modification), but circle is lower. You would have similar effect if you would lower bottom bracket by an inch or two.

 

[Gringo]

If you have read my post you’ll see I said I use a shorter crank arm than originally came with my bike, the Alie adapter I linked to simply puts the pedal where it would be at the bottom of the stroke (maybe a few mm more)
the highpath ones are more adjustable but do the same job

 

[flecc]

Indeed they have but £300 is a little more than most would be comfortable paying. £17 on Alie is affordable

Agreed, but reflecting how impossible it is for us to compete with the Orient.
.

 

[Gringo]

Agreed, but reflecting how impossible it is for us to compete with the Orient.
.

Highpath created a adjustable length crank arm and then added an adjustable length swinging pedal arm, this make for an expensive product but it does have a lot more adjustments And it’s a one product solution.
The Alie product requires you to either buy shorter arms or drill and tap your existing arms to the length you need (sometimes that’s what I do)
the two products aren’t really comparable as to value for money but basically the results are the same.
i posted this here because I thought it might help someone else with knee issues. On the last bike I did, it cost me £40 (£23 for 155mm Bosch crank arms and £17 for the bits from Alie)

 

[Az.]

If you have read my post ...

I have read. I just suffer from short term memory loss

£350 for something so simple is insane really. Is this price for one side only? Does it mean one is expected to pay £700?

 

[Sturmey]

...The biggest problem with short cranks is that in order to get full leg extension you raise the seat, this in turn increases the ride height and reduces your ability to put your foot flat on the ground.........

This is something I played around with a bit. Some observations/comments.
I notice many of the older hybrids seem to have lower bottom bracket heights to begin with. MTBs on the other hand are often over an inch higher.
One of the great advantages of disk brakes is that you can relatively easily adjust the bottom bracket height/geometry by changing the wheel size. In particular, I like to fit a smaller wheel at the rear which 'relaxes' the handling, giving more stability and makes it easier to put your feet on the ground. I have done this with my Carrera Vengence by replacing the 175mm cranks with 170s and the 27.5 rear wheel with a 26 inch. I am in the process of gathering up bits to build a 'mullet' (24R/26F) at present. All my builds could be considered as 'Ratbikes' as I use cheap/free secondhand bikes and parts.