Seat Position

Oooooh...good get, I love stuff like that. I've been going nuts recently with seat position. On my old steel bike (58cm), with alot of seat pole showing, the furthest i could put the seat back was 8.5cm behind the bottom bracket, using an old Campagnolo post. I've just moved it to about 6cm (I'm experimenting).

I don't know for sure, but those measurements of Lances sound more than reasonable.

It obviously depends on how much post is showing, but 6.5cm sounds a bit small. I have some Ritchey seat posts that provide a greater range, but then, 6.5cm might be perfect.

Quoted post said:

Originally posted by limetex
I watched Lance Armstrong on OLN. He was checking the set-back of his seat from the BB. He said to the mechanic "It's110.9 and I need 111.5". I guess he was talking mm, but that is about 41/2".

On my custom built 56 cm frame I have a 72 1/2 seat angle and the most I can get, with the seat (Flite) all the way back, is 2 1/2" nose to C/L of BB. Did I misunderstand?

111.5mm is equal to 11.15cm or 4.39inches.

The seat setback is the distance between the vertical imaginary lines of the seat's center and the BB center as viewed from the side (see illustration). This distance or the amount of setback will depend on the following:

1) Seat Tube Angle
2) Seat Post Height
3) Amount of Seat Rail Travel

If you increase the seat height by, say 1cm, between a seat angle of 72degrees versus a seat angle of 75 degrees, you will find that the setback on the shallower angle (72 desgrees) will have travelled more. In the same way you can achieve the same setback without increasing seat height simply by pushing the saddle back on its rail as mounted on the seatpost.

Note: It also depends on where LA is measuring from his seat but generally it is the center where the post clamps meets the seat rails.

BTW, if one measures from the point where the seat post meats the rail then even if one slides the seat on the rail the setback does not change. I personally measure setback from the seats center and not where it meats the post.

I have always measured from the nose of the saddle straight down and measured the distance from the plumbline to the center of the BB. This number can be put on different bikes if you use the same saddle.

Quoted post said:

Originally posted by pudster
I have always measured from the nose of the saddle straight down and measured the distance from the plumbline to the center of the BB. This number can be put on different bikes if you use the same saddle.

Exactly the way I do it but my point was that, if Armstrong was doing it this way, how was he managing to get 4 1/2" when the max I can get by this method is 2 1/2". Does he know something I don't ?

His saddle could have different rails than yours. And/or his post could have a different head than yours (they make a big difference in fore/aft position). Does the head clamp in yours have setback? Does his? That's easily a 2cm swing.

Measuring to the nose used to be OK. But in recent years, saddles have begun to come in a lot of different lengths. Take the Fizik Arionne as an example. It's a good couple cm longer than the Fizik Pave. You've got to measure to the middle of the saddle for precision (and even that's flawed if you don't sit in the middle of both saddles)...

Quoted post said:

Originally posted by Aztec
His saddle could have different rails than yours. And/or his post could have a different head than yours (they make a big difference in fore/aft position). Does the head clamp in yours have setback? Does his? That's easily a 2cm swing.

Measuring to the nose used to be OK. But in recent years, saddles have begun to come in a lot of different lengths. Take the Fizik Arionne as an example. It's a good couple cm longer than the Fizik Pave. You've got to measure to the middle of the saddle for precision (and even that's flawed if you don't sit in the middle of both saddles)...

Quoted post said:

Originally posted by limetex

I have a Shimano Ultegra post, which has a pretty average set-back, certainly not different enough to account for 2". The saddles are about equal too.
I have to believe that he was probably using the center of the seat to be talking 4 1/2". Although then don't think it's a big enough number. I thought that maybe someone may have known for sure. Thanks.

Quoted post said:

Originally posted by Aztec

Measuring to the nose used to be OK ... You've got to measure to the middle of the saddle for precision ... [/B]

Good point Aztec. I also used to measure setback from the BB to the saddle nose, but I have recently started measuring to the centre of the saddle - especially when swapping between saddles for testing.

Now for a slightly different question - what defines the correct saddle setback?

... I always used to use KOPS (knee over pedal spindle), but I've seen some alternative views lately and I would REALLY like to solve this one. Any thoughts on KOPS or other methods anyone?

Thanks

Ian

So how do you calculate what is the proper seat setback? Height for weight? Is there a chart or a set of calculations or its just based on personal preference?

Quoted post said:

Originally posted by sugufish
So how do you calculate what is the proper seat setback? Height for weight? Is there a chart or a set of calculations or its just based on personal preference?

The classic way is to get in your comfortable position on the saddle by riding a few minutes. Then, with the crank arms in horizontal position, drop a plumb bob from the bony projection just below your kneecap and see where it falls relative to the pedal spindle.

Directly over the center of the spindle would be considered the "neutral" position, and a good start point. This neutral position works for me, others make adjustments to it.

Some riders like to sit a cm or two further back for more seated power at low rpm, while others say they can spin better with the knees a cm or two forward of the spindles.

It seems that moving the seat forward or backward effectively changes the seat tube angle. The KOPS procedure seems to be a very reliable 'safe' point, so long as your cleats are positioned correctly with respect to the ball of your foot.

Moving the seat forward effectively increases the seat tube angle, and basically puts you in more of a TT position. A more forward position is good for steady spinning and areodynamics, but is less comfortable and not especially suitable for power changes (e.g. sudden accelerations).

Moving the seat backward makes for a more 'slack' seat tube angle, which is more comfortable, and is better suited for hill climbing and such, where lower cadence power changes are needed. It seems many (if not most) prefer to be seated a little further behind 'neutral' than forward where general road use is concerned.

In any case, moving the seat forward or backward will change the seat height settings required to get the same angle of knee extension. A simple goniometer and plumb bob can be very help where getting optimum seat settings is concerned, and even a small adjustment in the right direction can make for a significant change in power output.

Hi all,

Thanks for the messages on saddle setback. Like Ted B, I have also tried a goniometer (angle measurer). I have a book that says the knee angle at furthest extension should be 32 degrees. I made a fixed angle gomiometer by screwing two pieces of wood together and tried to set my seat height based on the knee angle.

I've also seen suggestions that the knee angle should be more like 15 degrees, but I think that would feel too stretched. Any other thoughts on knee angle / seat height / setback?

I am sure that it's critical to get the seat in the right place (height and setback), whereas reach to the bars is more personal preference, so it doesn't matter how long it takes to find the best reach - or even if you change it over time.

Ian

Quoted post said:

Originally posted by ian-m
Thanks for the messages on saddle setback. Like Ted B, I have also tried a goniometer (angle measurer). I have a book that says the knee angle at furthest extension should be 32 degrees...I've also seen suggestions that the knee angle should be more like 15 degrees, but I think that would feel too stretched.

30 degrees is a good rule of thumb, and is generally considered to be both efficient and safe. You can go to 25 if it doesn't bother you, but I don't think there is anything to gain by going more extended than that.

Armstrong's (I wish people would stop obsessing about him so much) setback is actually quite small compared to the "traditional" climber/tt-er seat postion.
Lance spins like a trackie and so has his seat forward compared to most to accomodate this. (i use the same bike as he but I can tell by looking at the two that his seat is forward of where mine would be) Thus he must be measuring to the "centre" of the saddle.
measuring this way is fine as long as you always use the same saddl e (meaning that they have found one that they like!) and always sit in the same way. The reality is that people do NOT sit in the same position all the time and need a seat posi which will alow for a multitude of positions. The whole thing about knee over the pedal spindle is also rubish. It make no account of the fact that people will all have different sized feet, tibias and femurs and muscle proportions will be different too. The multitude of seat positions in the peloton should be proof enough of this. I sit comfortably with my right knee about 2cm behind the spindle.

My point is everybody is different and mathematical formulas can never EVER replace the senses of the individual rider (they can only give you an estimate). If your seat position is uncomfortable then for God's sake change it and try another until you get it right! Don't just blindly copy a man who is just another cyclist.