[kiwimtbr]

Hey,

Could someone explain to me the advantages of a layback seat post?

Kiwi

 

[Dropout33]

I dont think it comes down to advantage or disadvantage. It has more to do with fit in my experience.

Sometimes you need a little more room in the cockpit and the layback gives you that.

I'm no expert but I am sure one will chime in

 

[AndrwSwitch]

Are you thinking about buying one?

If your saddle is already as far back on the rails as it can go, you might benefit from it.

IMHO, saddle adjustment should never be used to make more room in the cockpit - only to get your body in the right position to pedal efficiently and safely. Overtraining injuries blow.

 

[kiwimtbr]

Yes i have been thinking about getting a Thomson elite 7 degree layback post.

Cheers for the advice

 

[pebbles]

I have a layback seatpost for my GF Mullet. With the stock seatpost I felt a little cramped on XC rides, so i got the Thompson. Now its like I have two bikes, one for XC, and one for urban/pumptrack! I cut the stock seatpost and put a DJ seat on it and kept the other seat on the Thompson.

 

[perttime]

It is all about fit.

I need it on one bike: with the short fork I have on it, the seat tube angle gets pretty steep, so I need a set back post to get the seat the right distance behind BB, for a balanced position.

 

[DiRt DeViL]

Set back posts are meant to allow the top of the knee to be parallel to the pedal spindle, this means that is more for fitting purposes than making room on a cramped cockpit.

 

[Gasp4Air]

Some may use it to position their knees relative to the pedals, but many, like myself, use it to increase the seat to handle bar distance, aka "stretching the cockpit". Similarly, on the front end, you can use a longer stem to the same effect. (Changing stem length can also affect steering feel). I'm long legged, and I use a 1" setback post as well as a long stem. When these measures, as well as seat post height reach their limits, a larger frame may be indicated.

 

[Harold]

Fit and rider position.

On the stock seatpost/stem combination on my bike, I was a little far forward and my pedal stroke didn't feel right. I looked at my fit and figured I could maintain the same reach if I got a slightly shorter stem and a laidback seatpost. Doing so would move my body to the rear slightly, changing my knee position over the bb. Turned out, that's exactly what I needed. Fit's about as close to perfect as I can figure right now.

 

[shiggy]

Some may use it to position their knees relative to the pedals, but many, like myself, use it to increase the seat to handle bar distance, aka "stretching the cockpit". Similarly, on the front end, you can use a longer stem to the same effect. (Changing stem length can also affect steering feel). I'm long legged, and I use a 1" setback post as well as a long stem. When these measures, as well as seat post height reach their limits, a larger frame may be indicated.

Not the same effect. The saddle location affects pedaling position. I need to get that right before I set the cockpit length.

Even if you do not care if you get your cockpit length by changing the saddle location or the stem length, which you choice to do changes the weight distribution, which changes the handling of bike.

 

[kiwimtbr]

So can someone explain to me the way to check for fit ie knee position to bb etc

Kiwi

 

[smilinsteve]

My top tube is a bit short. Increasing stem length increases weight over the front. A lay back post moves weight back. These 2 variables can be used to give you the forward/back adjustment you want.
The postion of the knee over the pedal is something I haven't thought about much, but I assume there has to be some "safe zone" where you can have some adjustment without problems. After all, different seat tube angles affect your knee position and so does the length of your leg which effects the height of your seat which effects the horizontal distance the seat sits behind the bb, etc.
So, how much safety factor is there in choosing your saddle, and therefore knee, position?

 

[shiggy]

My top tube is a bit short. Increasing stem length increases weight over the front. A lay back post moves weight back. These 2 variables can be used to give you the forward/back adjustment you want.
The postion of the knee over the pedal is something I haven't thought about much, but I assume there has to be some "safe zone" where you can have some adjustment without problems. After all, different seat tube angles affect your knee position and so does the length of your leg which effects the height of your seat which effects the horizontal distance the seat sits behind the bb, etc.
So, how much safety factor is there in choosing your saddle, and therefore knee, position?

None. Or lots. It can be highly personal. I am much more sensitive to saddle position than I am cockpit length.

But I also am constantly moving fore and aft on the saddle for the situation. And I also want my bars placed in a narrow range of position relative to the front axle.

 

[AndrwSwitch]

I'm fairly paranoid about my pedaling position, and I also find that I intuitively center myself over a point somewhere between the bottom bracket and the position of the pedal when it's at the front of its circle. I just put the saddle wherever my butt dictates, as long as the length from saddle to pedals gives me the stroke that feels comfortable to me.

The amount of weight I put on my pedals varies - anywhere from almost none of it if I'm cruising slowly on pavement to quite a lot if I'm sitting and climbing something steep and loose. Now and then, I'll actually lift my butt off the saddle on climbs of that type. I think that if the saddle position is correct, I should be able to transition between those extremes without having to make a big adjustment.

I just put my handlebars wherever is comfortable for me. The positions are very similar on the two road bikes I bought new, a little off (which I notice) on the road bike I bought used, and a little shorter (which I notice, but prefer for that application) on my mountain bike.

I think messing with saddle fore-aft positioning to try to save a bike that's really too small is a mistake, and have heard stories about people hurting their knees with improper fore-aft placement. But I leave researching that up to those who disagree with me.

 

[beenee98]

I got a straight thompson but found out that i didn't have enough room for correct leg positioning so swapped it for a layback post. Much better - had nothing to do with looks or anything, was simply i needed the extra room to have the correct positioning

 

[Gasp4Air]

Not the same effect. The saddle location affects pedaling position. I need to get that right before I set the cockpit length.

Even if you do not care if you get your cockpit length by changing the saddle location or the stem length, which you choice to do changes the weight distribution, which changes the handling of bike.

The "same effect" I meant was the lengthening of the cockpit. I did mention that moving the saddle is done by some to affect pedaling, and also that changing stem length would affect steering. But I agree that it could have been expressed more clearly that changing the seat position and lengthening the stem can have additional ( and different) impacts on the bike.

 

[perttime]

So can someone explain to me the way to check for fit ie knee position to bb etc

"The traditional method for achieving horizontal saddle position is to position the rider's saddle so that the bump below the knee (the tibial tuberosity) is over the pedal spindle with the crank horizontal to the ground. I'll call this the "KOPS" (Knee Over the Pedal Spindle) method (see Figure 1).

The common way to check this position is with a plumb bob. Typically, a framebuilder will choose a seat tube angle that places the saddle at the center of the seatpost clamp with the rider's knee in this position."

The article goes into all sorts of details on why it isn't exactly God's Gospel either.
http://www.sheldonbrown.com/kops.html