Spire

I had a bike custom made a few years back and a profession fitter recommended that I lower the saddle a centimeter or so. The reason why I'm hesitatant is because the seat post would have to be cut (as it means the seat tube inside the frame) and I'm just cautious about doing something that is irreversable. The guy says there is enough seat post that even with the 1cm off to have it where it is now. I'm just apprehensive because of the irreversality.

Given that is it best to err on the side of a saddle being too high or too how?

linberl

If the post is so long that you have to cut it to drop it one centimeter, then if you decide later to raise even a couple inches that should not be a problem....for normal seat posts. I can understand your hesitation if it is a super expensive post (Thomsom or something like that). In that case, if it's a standard size can you just buy a cheap one to get the sizing right and then duplicate on the better post?

Spire

It is a carbon seatpost that came with the bike whose length matches the seat tube exactly (they are one on top of each inside the tube). There is certainly not the ability to move it out a few inches but a centimeter or two should do it.

The issue here is that I was fitted by the framebuilder a few years ago but the guy who did a fitting more recently thinks it's about a centimeter too high. If I drop it a cm, it could be a cm too low, if I leave it as is, it could be a cm too high. So all things considered, which would be better a cm too high or too low. The fitter seemed to think that erring on the side of too low over too high would be better.

linberl

Imo a bike should fit. If it doesn't you replace the offending part. Too high can cause problems just like too low can. Depends on how your body handles the different stresses. Too low will also reduce your power. Why did the fitter want your seat lower? Are you having any issues with it the way it is? Go buy a cheap seat post and cut it to the shorter length and try it. Once you get it dialed in, then you can feel confident adjusting your carbon post.

Spire

Thanks for the info but do you have and information on the question asked?

kingston 

IMO it's better to be a few mm too low than a few mm too high. If it were my bike, I'd cut down the post and try the fitters suggestion. If you don't like it you can put it back where it was.

linberl

AS I said it depends on how your body reacts. Too low can overwork the quads and reduce power. Too high can increase power, more glutes, but can over work the hamstrings. Which will be best for you depends on YOUR body, the flexibility in your muscles and ligaments. No one can tell you what is best for YOU. Now, for me, if it's too high, I get tenderness behind my knee in the hamstrings - if it's too low, my quads don't get bothered too much but the front and top of my knee will hurt and sometimes my hip because of the more closed hip angle. So if my seat is too high I tend to spin a lot more to save the hamstrings; I can push harder if it is too low to make up for the lack of power from the glutes, but I pay for it later off the bike. I set my seat post by starting with the standard recommendation and then rise it up until my hamstring hurts, then I drop it ever so slightly. But that's my body and me. Again - I suggest buying a cheap post (less than $20) and cutting it down and seeing how it feels, if you don't want to cut your carbon post without some certainty. Depending on your body, you might not even notice a difference...1 cm isn't a lot for some folks, and it is huge to others.

phughes

You don't have to drop it an entire cm, you can always go in between. Right? Oh, and between the two choices, I would always go lower than higher.

woodcraft

If the post cannot go down further, then it is likely hitting the water bottle boss, but in any case

It's not designed to be supported from the bottom and that extra length is not needed.

There is a minimum insertion line on the post, which shows how much has to go into the frame, usually about 4".

As long as that much or more goes into the frame, inches can usually be cut off

and still leave enough to raise the saddle much higher than you ever would want.

I often cut a couple of inches off the post just to save weight.