LBS who will swap crank on new bike

fret_wimp2

Ive started having a little knee pain after cycles, and rather than let it fester im looking to resolve it.

Im playing with different saddle heights, and have increased it by about 1cm, logic being that I will stop my leg coming too high at the top of the stroke, where knee flexion is greatest.
Problem with this is my leg is also a lot straighter at the bottom so i dont think it will end up solving my issue.

Next thing to try is shorter cranks. the bike currently has 175mm shimano 105 crankset, id like to try a 160.

As i was considering getting a new bike more suited to what i want, this may be a good opportunity to make a slightly better choice 2nd time around.

Are there any shops that will just do a like for like swap if the bike is brand new and im purchasing from them?

magicbastarder

going from 175mm to 160mm is a very large jump, no? most small bikes ship with 170mm IIRC.
it may be that shortage of parts might scupper your idea.

fat bloke

fret_wimp2 wrote: »

Ive started having a little knee pain after cycles, and rather than let it fester im looking to resolve it.

Im playing with different saddle heights, and have increased it by about 1cm, logic being that I will stop my leg coming too high at the top of the stroke, where knee flexion is greatest.
Problem with this is my leg is also a lot straighter at the bottom so i dont think it will end up solving my issue.

Next thing to try is shorter cranks. the bike currently has 175mm shimano 105 crankset, id like to try a 160.

As i was considering getting a new bike more suited to what i want, this may be a good opportunity to make a slightly better choice 2nd time around.

Are there any shops that will just do a like for like swap if the bike is brand new and im purchasing from them?

I'm sure if stock permits then any shop will facilitate you. That's a massive change in crank length however. You're quite literally going from one extreme to another in that 175 is about as long as cranks can be, and 160 is about as short.

Self-diagnosing bike fit like that can end up being very expensive, as there are so many things that you could potentially change - saddle type and position, cleat and pedal position, maybe even the bike is the wrong size. IMO definitely worth going to a bike fitter and letting them have a look at you to see what the likeliest culprit is.

fret_wimp2

magicbastarder wrote: »

going from 175mm to 160mm is a very large jump, no? most small bikes ship with 170mm IIRC.
it may be that shortage of parts might scupper your idea.

The bike is a cube SL Road, size 50 XS by cube's sizing. just measured the crank and its 175.

ive no idea if 15mm is too big of a jump. multiple articles online favor the idea that most crank size differences are too small to be of real use, which is why I'm considering making the biggest jump available.

fat bloke

That's very very unusual, (in fact that sounds like an error), if a bike size XS has that crank on it. 175 usually comes on sizes 58 and up, which is Large or Xl in most frames.
Where are you measuring from? Cranks usually have the length stamped on the inside of the crank arm towards the pedal end. Any XS bike I've ever bought had a 170 or shorter on it.

cyclocross!

fret_wimp2 wrote: »

Ive started having a little knee pain after cycles, and rather than let it fester im looking to resolve it.

Im playing with different saddle heights, and have increased it by about 1cm, logic being that I will stop my leg coming too high at the top of the stroke, where knee flexion is greatest.
Problem with this is my leg is also a lot straighter at the bottom so i dont think it will end up solving my issue.

Next thing to try is shorter cranks. the bike currently has 175mm shimano 105 crankset, id like to try a 160.

As i was considering getting a new bike more suited to what i want, this may be a good opportunity to make a slightly better choice 2nd time around.

Are there any shops that will just do a like for like swap if the bike is brand new and im purchasing from them?

Changing Shimano cranksets is a very simple job that should only require an allen key and a crank lock remover. Plenty of tutorials online. If you around North Kildare I have a spare crank lock remover you can have.

Macy0161

I'd say a bike fit is the best solution first tbh.

Not going to go anywhere near medical advice, but if you google cycling knee pain it will give you potential causes if you haven't done so already. I'm kinda surprised the top of the stroke would be the issue. fwiw, when I was having ITB issues, at a bike fit, my saddle was too high.

Might also be worth a trip to a physio - knee pain could be a number of things (glutes not firing putting more through the quads was another factor in my ITB issue).

fret_wimp2

cyclocross! wrote: »

Changing Shimano cranksets is a very simple job that should only require an allen key and a crank lock remover. Plenty of tutorials online. If you around North Kildare I have a spare crank lock remover you can have.

Thanks for the offer! swapping over isnt really a problem, i just wanted to see if its possible to save the cost of a crank i may not need, by buying a new bike. makes complete sense really!

Macy0161 wrote: »

I'd say a bike fit is the best solution first tbh.

Not going to go anywhere near medical advice, but if you google cycling knee pain it will give you potential causes if you haven't done so already. I'm kinda surprised the top of the stroke would be the issue. fwiw, when I was having ITB issues, at a bike fit, my saddle was too high.

Might also be worth a trip to a physio - knee pain could be a number of things (glutes not firing putting more through the quads was another factor in my ITB issue).

Im not sure it is the issue but some research suggests that the top of the stroke is the most knee flection and front of knee pain can come from the knee going too high.

Bike fit may be the best solution, but i'll experiment with saddle height first.
Its also highly likely im overdoing it. I've gone from zero cycling or running to cycling and running 3-6 times a week & pushing myself hard on most of those outings. more rest days and stretching/mobility work could equally be the solution.

More experimentation needed.

Macy0161

Not saying it's the same thing, or giving medical advice, but my own experience is I get front of knee pain/ twinges when my quads are tight as feck and/or when I'm grinding at low cadence (which I seem to have a habit of doing while zwifting).

fat bloke

Tbh when I read the word "running" that was diagnosis enough for me! Pounding the pavement is much harder than on knees than millimetres of seat post or centimetres of crank length!

hesker

+1 for physio/stretching exercises. I’d try that before buying any new gear.

Many physios are not that into doing massage as it can be hard on the physio to be doing that routinely. I’m lucky enough to have found a good massage therapist that I go to every 6 months or so. Has made a world of difference to me

gaffmaster

Slide your cleats as far back on your shoes as they can go - so move them as close to the heel as possible. This moves your foot forward on the pedal and helps stabilize the feet. It's not a replacement for a bike fit, but it might help you out in the short term. Be careful with making your saddle too high - can present loads of other problems, especially in soft-tissue areas, cough. You might also benefit from a cleat with more float to allow lateral movement of the feet.

dub 24

You should consider getting a bike fit that way the fitter can guide you towards the bikes that suit you. They are also very knowledgeable when it comes to niggles and pains relating to cycling and might even be able to resolve the issue without heading down the medical route.

triggermortis

+1 on the bike fit.

They will detect things you don't even know about and suggest remedies. When I got a fit, the guy told me my knees were rotating inwards with each stroke of the pedal. He showed me this with a laser on my knee cap. The remedy was insoles for my shoes.
I'd never have figured this out on my own

Paul Kiernan

Are you sure your current crank is 175? You said you measured it but it's stamped on the inside of both cranks down near the pedal!

CramCycle

fret_wimp2 wrote: »

Im playing with different saddle heights, and have increased it by about 1cm, logic being that I will stop my leg coming too high at the top of the stroke, where knee flexion is greatest.
Problem with this is my leg is also a lot straighter at the bottom so i dont think it will end up solving my issue.

Regardless of crank length, if your leg is too straight when your crank is at 6o'clock, then your saddle is too high, end of discussion there. Go to a bike fitter first, and get sorted properly, shorter cranks won't do you any harm though, although you will struggle to find anything shorter than 165mm in common cranks.