Shorter cranks on SuperCharger 2

[sammcneill]

Hi All

I posted elsewhere on this forum that I’d fallen off my eMTB and wrecked my knee.
I was dropping my SuperCharger2 off for servicing today and replace the Ergon grips (not been ridden in four months due to my wrecked knee).

The owner of the LBS suggested I may want to consider shorter cranks on my bikes moving forward if my knee never regains full range of motion. I saw the surgeon today (2 weeks post-surgery for second time
On this knee) who told me I definitely won’t ever get full range of motion back but he felt with hard work I should get enough to pedal a bike (he’s a keen cyclist himself).

So Question Time: has anyone here dropped to a shorter crank on their R&M specifically to make it easier to pedal due to limited knee movement?

I’d be super keen to hear any experience in this space or if anyone knows a way to calculate the difference a shorter crank would make on the knee revolution?

If interested, here’s the iteration of my knee over four months from when I fell off and completely ruptured my quadriceps tendon off the patella:

A few hours after the accident at the hospital:

Two weeks post surgery #1

Three days post-surgery #2

Two weeks post-surgery #2 (today)

Happily, the surgeon said in front of my wife today “it’s a massive job rehabbing this one Sam - it should definitely qualify for an NBD at the end of it all!”

I couldn’t agree more and my wife heard it first hand from the surgeon!

 

[Jay Kay]

Ouch. I recall way back someone changing cranks for this reason, and it helping their knee problem. Hopefully they will resurface again to confirm.

 

[Seventysomething]

Hi All

I posted elsewhere on this forum that I’d fallen off my eMTB and wrecked my knee.
I was dropping my SuperCharger2 off for servicing today and replace the Ergon grips (not been ridden in four months due to my wrecked knee).

The owner of the LBS suggested I may want to consider shorter cranks on my bikes moving forward if my knee never regains full range of motion. I saw the surgeon today (2 weeks post-surgery for second time
On this knee) who told me I definitely won’t ever get full range of motion back but he felt with hard work I should get enough to pedal a bike (he’s a keen cyclist himself).

So Question Time: has anyone here dropped to a shorter crank on their R&M specifically to make it easier to pedal due to limited knee movement?

I’d be super keen to hear any experience in this space or if anyone knows a way to calculate the difference a shorter crank would make on the knee revolution?

If interested, here’s the iteration of my knee over four months from when I fell off and completely ruptured my quadriceps tendon off the patella:

A few hours after the accident at the hospital:

View attachment 179845

Two weeks post surgery #1

View attachment 179846

Three days post-surgery #2

View attachment 179847

Two weeks post-surgery #2 (today)

View attachment 179848

Happily, the surgeon said in front of my wife today “it’s a massive job rehabbing this one Sam - it should definitely qualify for an NBD at the end of it all!”

I couldn’t agree more and my wife heard it first hand from the surgeon!

I use shorter cranks because I cannot bend my knee past 90 degrees, had surgery in 1975 and replaced my right knee in 2018, I have 140 mm cranks on my Specialized Vado, I tried 160 mm but still not enough to keep my foot on. The Bosch and Brose motors both use the same isis spline crank mount, fairly simple to change out. I am a casual rider so I cannot tell a lot of difference in cadence, I can get my bike up to 25 mph comfortably at about 80 to 85 cadence with the enviolo cvt IGH

 

[sammcneill]

I use shorter cranks because I cannot bend my knee past 90 degrees, had surgery in 1975 and replaced my right knee in 2018, I have 140 mm cranks on my Specialized Vado, I tried 160 mm but still not enough to keep my foot on. The Bosch and Brose motors both use the same isis spline crank mount, fairly simple to change out. I am a casual rider so I cannot tell a lot of difference in cadence, I can get my bike up to 25 mph comfortably at about 80 to 85 cadence with the enviolo cvt IGH

This is great news and very comforting to hear!
After an intensive physio session yesterday I got my knee to bend to 110 degrees but I’m absolutely paying for it today (very stiff and sore and back to about 90 degrees ROM).

I’m only 2.5weeks post open knee surgery so still swelling and inflammation but great to know shorter cranks can work if less than 90 degrees ROM in the knee.

Thanks for replying!

 

[Seventysomething]

This is great news and very comforting to hear!
After an intensive physio session yesterday I got my knee to bend to 110 degrees but I’m absolutely paying for it today (very stiff and sore and back to about 90 degrees ROM).

I’m only 2.5weeks post open knee surgery so still swelling and inflammation but great to know shorter cranks can work if less than 90 degrees ROM in the knee.

Thanks for replying!

Give it time and do the therapy, very important to do early, although painful sounds like you will be back to 110 degrees + soon, then you would be able to use the stock 170mm

 

[sammcneill]

Sharing a positive update! For the first time in 4.5months I was able to ride a bike … my R&M SuperCharger 2… knee rehab has been hard and it didn’t feel comfortable but got a few turns of the pedals on the driveway yesterday and then a 5km ride today.

I had a short video but does not look like I can upload videos to this forum. A still instead:

Left knee was the ruptured quadriceps tendon and in good flex in this still. This is half the scar (above my knee):

Lovely to then follow up with a 5km ride today:

All very slow and knee was tentative but got there! Felt great to get it done.

Interestingly, the geometry on my eMTB (Specialized Turbo Levo) and my gravel bike (Soma Wolverine) do not allow me to pedal a full rotation with current knee flexibility.
Hope to get on them soon!

 

[sammcneill]

Massive Knee Injuries Change Everything: Why I’ve Not Been Blogging Recently

During an innocuous Easter bike ride, I managed to fall off and wreck my knee, rupturing my left quadriceps journey. This post is the fallout and recovery from that accident: two surgeries and 218 …

samuelmcneill.com

A cathartic retelling of my knee injury and subsequent journey. I’ve zero expectations anyone reads it fully, but if you’re suffering insomnia this may help a little…the good news is my knee is REALLY better (but not perfect) and I'm riding all my bikes again.