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Bike Fit General
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ITT: I answer questions and give advice on bike fitting, I'll be around for a couple of hours today so lay it on me.

Fitting is a broscience-filled field so I'll do my very best to cut through some of the "tradition" of bike fitting, especially regarding saddle tilt, knee angle, torso angle and medial/lateral tibial position etc.
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>>903447
>implying youre any better
You aren't.
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>>903451
post pics of your bike fit/ask a question or git out anon.
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Vaguely related, but any recommendations for someone who gets knee discomfort (stiffness, twingy feelings - but no pain) when riding in cold weather? I hate riding with tights on, on a long ride I can feel the tights 'gripping' my kneecaps and it's just as bad as riding cold.
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>>903456

Preliminary questions:

-Any history of knee injury?
-Is it one knee or both knees?
-Are your knees an equal distance from the top tube when riding?
-Is the pain in the front, back, sides of the knee or all the way through the joint?
-Do you ride hard right from the start or warm up a bit before riding at working pace?
-Just how cold is it?
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>>903456
That's normal when it's cold... there's not much blood supply to the knee joint itself, and as it is lubricated by the body, any lubricant will not work quite as well in the cold.
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>>903460
Thanks, that's been my thinking - any ideas for insulating the knees without uncomfortable tights or stockings?

>>903459
I had knee pain issues a few years ago that cleared up after rest and addressing the causes, the present discomfort is in both knees, in temperatures roughly about freezing (or a bit warmer if there's much wind), there's no pain at all and this occurs after I've been out in the cold for a while, doesn't go away after warming up and isn't related to ride intensity. And I have no fit issues when the weather's warm.
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>>903462
What were your knee pain issues and the cause of them?

>>903460
This anon is on the money- Your knees, when being blasted with cool air and freezing temps generally aren't able to produce enough synovial fluid and blood flow to keep up with the constant load on the knees (both can be genetic factors.)

Without seeing you in action this is about all I can advise for now
-Wear something insulating over the knee joints like wool/Neoprene sleeves or wear 2/3 length bike shorts with knee insulation (even if you can heat the joint up a few few degrees it'll do you good)
-Possibly assess your seat height: vast majority of people I see have their seat too low and don't know it because their technique has adapted to it.
-Definitely assess your knee in relation to the pedal spindle, despite what sheldon says, it's actually very important to not have it forward of the centre of the spindle; mainly because if your saddle is too low AND you have your knee past it, It causes some inefficiencies and possible injuries)
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>>903470
Also, here's a test for doing your own knee over pedal spindle test at home:

-Acquire or make a plumb bob (a star fishing sinker on the end of some twine will do fine too)
-Move the crank so that the pedals are horizontal, you'll need to measure the leading or "front" knee.
-Hold the string of the plumb bob against your Tibial Tuberosity (pic related) and see where the string falls (the weight at the end needs to be off the ground obviously)
-Find out how much forward or back you are of the CENTER of the pedal spindle, do this for BOTH knees.
-Adjust the seat rails fore or aft so that you're either right on the center of the pedal spindle or a few mm back if you prefer (it's better to be very slightly back if in doubt)

Note: If one knee is over the pedal spindle and the other isn't, always adjust so that the knee that is further forward is on the pedal spindle (the other knee will be a little behind and that's ok). Some people have uneven femurs and other factors that cause this, but it's not a big deal.
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>Fitting is a broscience-filled field so I'll do my very best to cut through some of the "tradition" of bike fitting
>KOPS is very important
just fuck off
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>>903479
You'll find that although it's harder to assess and qualify, recumbent bikes also need knee over pedal spindle relative to the hip joint anon.

Just because the power transfer is at different angles on a recumbent, doesn't mean the knee joint magically changes its biomechanics.

Get a grip anon, your shitposting isn't welcome here.
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>>903482
>knee over pedal spindle relative to the hip joint
Please explain in more detail.
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>>903486
Femur length and some other factors affect it, but in the power phase of a pedal stroke the; knee goes from power production via knee joint extension and transfers over around the 2 o'clock position to knee flexion. It does start at the hip fore and aft position and hip angle but the problem occurs in the knee itself.

This transition is always under the most load of any part of the pedal stroke and if your knee is too far forward relative to the pedal spindle, the transition can become very jerky and inefficient as the transfer angle becomes very acute and the knee has to "pull" back at a more perpendicular angle to where the power transfer needs to be = less power and smoothness.

Most riders who have ridden with this setup over time generally compensate with excess ankling and lose power as a result, although if you have very long lower limbs, you will get away with this easier than most.
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Ok lads, I've gotta go in about half an hour so if you have any quick questions I can answer them, otherwise I'll be on tomorrow.
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>>903487
That really has nothing to do with whether the knee is over the spindle or not.
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>>903495
What's the best way of " transfering" your fit to a new bike with different measurements different application.
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>>903496
It does actually, the straighter the knee joint is at any phase of the stroke the more power it can produce; and the more acute the transfer angle between extension and flexion the more the legs have to adapt to a badly dialed in pedal position.

if you think you're fine on your bike, then leave it as it is; I'm not gonna lose sleep over you having a bad fit.

>>903497
Top of saddle to center of pedal spindle height is a good place to start, then get your seat fore and aft sorted.

Next is upper body, stem length and reach are a little different and the gold standard is hip angle being the same as on the old bike, but start with having the distance between where you sit on the seat and where your hands hold the hoods/bars. Hip angle isn't always simple on the new bike so for a start it's sometimes better to just make sure you're not too bent over or too upright and reaching out too far and rounding your shoulders forward.

A rough fit guide order without seeing at least a before and after pic:

-Height between top of saddle and centre of pedal spindle when the crank is IN LINE with the seat tube (not at BDC)
-Seat fore and aft and knee over pedal spindle adustment
-distance from sit point on saddle to hoods
-If possible, try to get the same height offset between top of saddle and where you grip the hoods (measure this from the ground with a ruler if you're at home)
-Saddle nose tilt, you want to be mostly on your sitbones (Ischium) with your perineum sharing the load as much as is comfortable.
-assess the new fit: take pics/vids from sides and front in a warmed up state.
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>>903502
I forgot to mention: handlebar width and how turned in/out your hoods are in their mounting matters a lot too, having them mounted so that the wrist is neutral in line with the forearm and the rider is easily able to tuck their elbows in without trying.

Of course, like most upper body bike fit issues it's a constant compromise between comfort, efficiency and aerodynamics and often the issues can lie within the lack of flexibility of the rider.

But that's an issue for another day, I'm out for today so have fun while I'm gone kids.
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>>903502
None of this ties the rider's position to gravitational acceleration as KOPS does.
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>>903447
I see that picture an I think in my Jewerly
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>>903547
"and"
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The guy at the shop angled my handlebars downward so my wrists wouldn't be as bent, but I read online that you should never have them downwards, only parallel or slightly upwards.
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>>903447
Still there, physio guy?
My GF often experiences knee pains in both knees (not at the same time) while riding. I adjusted the saddle height and position for her as I do for myself (your leg fully streched with your heel on the pedal with the pedal in six'o clock position and the trick with the plumb-bob). I never have problems, but she does. Any Ideas?
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>>903553
Instead of tilting them downwards , you should make them straight, and instead turn that stem upside down.
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>>903456
Use thick loose wooll socks, with fingers cut out, and slide them over knees. That should keep them comfortable, without putting thick pants on. Cold is one of joints worst enemys.
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>>903558
I see, but is there anything wrong with having them angled downwards?
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>>903456
this, t b h f a m
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>>903447
>LBS bike fit.gif
riding a bike like this clearly makes you impotent.
no question.
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I'm Back for a little while guys and girls, so I'll try to answer a few more q's.

>>903505
KOPS and the 98% of GT just happen to fall into the right biomechanical bracket for most non athletes anon and are a great starting point that allow for the body to adapt slowly to changes before you start getting funky with goniometers, spots, lasers and the like. They've worked for many and still continue to do so.

Remember that bike fitting is a process rather than an event, If I were to raise someone's saddle 30mm in one hit, the chances of them getting injured are suddenly much higher. Small increments and riding at recovery rate (<70% of normal load) are the best.

>>903553
Which way are your wrists bent anon? wrist pain can occur from excess wrist movement in any plane, as well as Ulnar Nerve pinching in some riders. I need more info.

That stem does look high by the way, if your bike is properly sized and you don't have a large gut it'd be worth trying to get it flipped and lowered in time; but if you commute or have hip/lower back issues then probably best left alone until you can actually see someone about it in person.

>>903556
I'm here anon, with questions:

-Does she have any pre existing knee injuries?
-What part of the knees hurt? Does it vary?
-What type of shoes and pedals?
-Do her hips tilt from side to side as she rides?
-Looking from front on, are both her knees about the same distance from the top tube? Does this vary and are they either very close or very far that you can tell?

I don't think at this stage her seat height would be too high, get back to me with answers and I'll see what I can do.
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>>903502
>leg extension is the same as kops
What the actual fuck am I reading?
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>>903447
>Fitting is a broscience-filled field so I'll do my very best to cut through some of the "tradition" of bike fitting, especially regarding saddle tilt, knee angle, torso angle and medial/lateral tibial position etc.
>entire thread is broscience tier shit
Jesus fucking Christ.
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>>903451
>>903611
>>903479

That salty samefagging, give it a rest son.
You have some better qualification or links to papers to contribute instead of ad-hominem accusations?

>>903610
maybe you should actually read this:
>>903610
It just happens to work as a progression towards a better fit, for people with unusual leg dimensions I generally throw it out the window but for the purposes of this thread it'll greatly reduce the chances of me giving injury causing advice.

If you want to win an internet argument over something, go somewhere else; as this will be my last response to you.

Unless you want to pay me for my time, that is; then we can discuss how dick length affects riding or whatever else you like anon.
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>>903614
I'm not samefagging unless you consider >>903610 and >>903611 samefagging, because those were both me. But yeah, run away when you say something retarded and just try to dismiss it as someone samefagging.
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>>903614
Why would I need to link to a paper to point out that you are advancing to contradictory fit methodologies?
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>>903654
*two
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I have a cross bike I would like to buy but I'm afraid it's too big for me. Bikesdirect, so I won't be able to test ride. Will anyone be able to tell if the bike will fit me well if I send my current bike geo and the cross bike geo?
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>>903654
Your filename seems like it might suggest otherwise m80.
Where's the second time you told the guy to fuck off?
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>>903678
>>903501
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What do you know that the average bike mechanic doesn't?
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>>903608
Sorry for the late reply.

>Does she have any pre existing knee injuries?
Not really. She experienced these problems the first time while touring a few years back. Don't know if the bike was properly fitted. They do come back if she pushes herself to hard.

>What part of the knees hurt? Does it vary?
Not the back nor the side, more like the front (she can't really tell, just "on the inside"). The position of the pain doesn't vary.

>What type of shoes and pedals?
She commutes by bike, so non-sporting shoes, like boots with small heels or flat sneakers. She uses simple platform pedals.

>Do her hips tilt from side to side as she rides?
No. I told her to check for that as it indicates that her saddle was too high.

>Looking from front on, are both her knees about the same distance from the top tube?

Hard to tell because she has a ladies' frame. I told her to watch out for lateral movement of the knee as the joint isn't really cut out for that. I think she makes a conscious effort to make a strictly up and down movement. Sadly, I don't have my bike here to check, but I can get back to you with this.

Oh and we live on the foot of a hill, so we have to climb first thing in the morning. Her commute is just 1.5km tho.
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>>903779
He "knows" he's better than the average bike mechanic, even if it isn't actually true.
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>>903455
> talk shit post fit fuccboi
Thread replies: 42
Thread images: 10

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