saddle fore aft position KOPS

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hoogerbooger
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Joined: 14 Jun 2009, 11:27am

saddle fore aft position KOPS

Postby hoogerbooger » 8 Jun 2019, 2:00pm

Colin531 suggests that Knee Over Pedal Spindle (KOPS) is a useful rule of thumb method for saddle fore aft saddle position ( having set the saddle height)

His guide says the plumb-line should be held at the top of the shin ( not kneecap it seems). Is that the correct interpretation as it makes quite a lot of difference. ( even with my missus who definitely doesn't have knobbly knees)

Colin indicates that the KOPS method is also much maligned on t'internet. Views welcomes on how the KOPS approach should be done & other approaches for initial set up to get into the right ball park for a touring/leisure cyclist.

PT1029
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Re: saddle fore aft position KOPS

Postby PT1029 » 8 Jun 2019, 2:49pm

As I understand it, it is what I would call the hinge of the knee/sticky out bit over the pedal axle (crank horizontal/forward).
I recall somewhere seeing a plumb line from the front of the knee cap over the pedal spindle which I take as wrong.
If I used the front of the knee cap over axle version, my saddle would be rediculously far back (on a 72 deg seat angle) combined with a rediculously short handle bar stem.
I do many miles without leg ache/issues, so it can't be that bad!

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531colin
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Re: saddle fore aft position KOPS

Postby 531colin » 9 Jun 2019, 6:11pm

For KOPS I believe its traditional to hold the plumbline on the little knob on the top of the shinbone. ...this is where the patellar tendon attaches, its called the Tibial Tuberosity if you want to give it its full title. Big name for a little bony lump. ( reminds me of somebody.....)
The usual (alternative) method of finding saddle setback is the "balance point" method. I think that recreational/touring cyclists are comfortable with very little weight on their hands, and certainly roughstuff cyclists need to be balanced fore and aft on the bike, otherwise its more difficult to un-weight the wheels in turn going over bumps, or to get the weight off the front wheel going down hill. Steve Hogg on balance point here https://www.stevehoggbikefitting.com/bikefit/2011/05/seat-set-back-for-road-bikes/....its long! Steve is talking about racing cyclists being balanced when on the drops, for recreational cyclists I feel being balanced on the hoods is a better bet. I talk about balance point in my DIY stuff, its shorter than Steve Hogg's!
The usual objection to KOPS is that there is no science behind it. Fancy that. Or that Kops doesn't facilitate a smooth transition between pedalling seated and standing on the pedals....for recreational cyclists, I'll take comfort as a priority over that.
Something which many people find counter-intuitive and therefore difficult to get their head round....If you want a reasonable stretch forward to the handlebars, you are also going to have to move your saddle backwards. Yes, thats it, to reach forward, you need your saddle back. The reason is simple; as you lean forward, your torso is cantilevered further and further forward. If you adjust nothing else, cantilevering your torso forward puts more weight on your hands. To take weight off your hands, move backside back. You can try it on your existing set-up by just sliding back in the saddle. ...please don't tell me I'm wrong without trying it.
Also, please don't tell me that your set-up is nothing like this and you are perfectly comfortable because you can do X, Y or Z. If you are young enough, fit enough and strong enough you can get used to almost anything.

ANTONISH
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Re: saddle fore aft position KOPS

Postby ANTONISH » 10 Jun 2019, 8:33am

Bernard Hinault's book " Road Racing technique and training " attributes KOPS to Daniel Clement who used to be the French national coach.

" Sit on the saddle in a normal position , shoes in the toe clips with the cranks horizontal and the bike on a perfectly level surface. A plumb line which passes from the end of the femur of the forward leg, just behind the hollow of the kneecap should basically fall over the pedal axle"

Bernard Hinault subsequently had his saddle set further back from this to obtain (for him) the optimum position.

I think for most of us it's a good starting point - not many of us using toe clips these days though.

Witterings
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Re: saddle fore aft position KOPS

Postby Witterings » 10 Jun 2019, 12:13pm

Another easy ish way is put the plumb line on the front of the kneecap and line it up with the end of the crank arm ... the difference in distance between there and the middle of the axle's pretty much the same as between the top of the shin to the front of the kneecap.

Something I used to get wrong before I had a bike fit was my foot would be tilted up when I did it but I believe your foot should be horizontal with the ground and it can make quite a difference.

hoogerbooger
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Re: saddle fore aft position KOPS

Postby hoogerbooger » 10 Jun 2019, 4:35pm

Thanks for the comments.
(Having posted I've been trawling the web, plus my missus & her bike have been on the turbo trainer with plumbline etc)

With the set up she has been using, but which recently has been causing a bit more neck/shoulder/wrist pain, KOPS suggests her saddle was 3/4" or so too far forward.

I found stuff online also about balance and that this should be best when the hip is lined up with the axis of the seat tube. This also suggests that her saddle is 3/4" or so too far forward.

Simples !....almost . If I understand things correctly, pushing the saddle back that 3/4" should as a rule of thumb be good for balance and transmission efficiency+ reduce weight on her (slightly arthritic) hands(thumbs).

But is that not more likely to cause neck/shoulder ache ?

( for info its a flat bar converted mountain bike roughstuff tourer with long round the corner bar ends. Bar ends used for up hill and headwinds, palm on bar ergo grip or holding grip at levers most of the time)

As I could, I've added a 1cm spacer and raised the handlebar height....... I presume this may be a bit better for the neck...but puts back some of the weight on the hands undermining the benefit of moving the saddle back ?

Is the above logic correct ?

The other issue we have is the frame probably too long ideally. It's running currently with a 50mm stem so not much option to shorted. the raised handlebars (grip section) are now about a centimeter above saddle height.

I'm thinking that with this frame we have a neck ache vs hand ache compromise & we'll just have to see if the slight tinkering helps or hinders.......but should serious aches continue we may have to think about a new frame.

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531colin
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Re: saddle fore aft position KOPS

Postby 531colin » 10 Jun 2019, 6:32pm

I would expect pushing the saddle back 3/4" to take weight off the hands. This should mean riding without tension is the shoulder muscles, so I would expect less discomfort in the neck.
I think raising the bars even by as little as 1cm should help as well; in the last few years my bars have crept up to be slightly above the saddle, I too have arthritic hands (and I shall be 72 this month, that's crept up on me as well!)
I would be inclined to try the bike as it is now, and only changing more stuff if you need to. A quick google found a 35mm stem https://www.wiggle.co.uk/race-face-chester-mtb-stem-35mm/, I'm sure there will be more. Also with a high-rise stem I believe the length is measured along the stem, not horizontally, so with something like this https://www.amazon.co.uk/Acor-High-Rise-Ahead-Stem-Lengths/dp/B00GZ8J9V2/ref=pd_sbs_200_7?_encoding=UTF8&pd_rd_i=B00GZ8J9V2&pd_rd_r=b7eaa148-8ba6-11e9-a473-6ff71fc7a21c&pd_rd_w=TddUI&pd_rd_wg=cIiPl&pf_rd_p=18edf98b-139a-41ee-bb40-d725dd59d1d3&pf_rd_r=3HJVJN7KEXJRG747HCTE&refRID=3HJVJN7KEXJRG747HCTE you might be able to get the bars both closer and higher. Again, other makes available.
I think its worth spending a bit of time to get comfortable on the existing bike. Then if you do decide on a new one, at least you will know whats needed, rather than simply knowing what doesn't work.
I don't think raising the handlebar will put weight on the hands.
I don't understand the thing about lining up the hip with the seat tube.....won't that change the riding position depending on the seat tube angle?

hoogerbooger
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Re: saddle fore aft position KOPS

Postby hoogerbooger » 10 Jun 2019, 7:04pm

Thanks for the comment. We will test the tweaked set-up with 4 weeks in northern Spain .....the 1st proper tour in 4 years since a car unkindly broke various of my missus' bones ( The arthritis is just an age related added extra). We'll see how it goes & consider set-up from there.

RE lining the the hip up with the seat tube angle: I didn't see a specific reasoning. But found two places citing the principle. There is obviously some logic that moving your weight affects the balance, by why the sweet spot should be in-line with the seat post angle ?? I don't know.