How to mark seatpost position?

Question

Is there an effective, non-destructive way to mark the seatpost position?

We share some bikes within the household, meaning that the saddle height is adjusted often. When I had an affordable Decathlon bike, it came with a seatpost that had centimetre markings on it (like this). This was very helpful in quickly setting the preferred saddle height for any family member. Unfortunately, most other manufacturer's don't include this feature, and Decathlon's own seatpost is not great (no angle adjustment for the saddle).

Is there a reliable and ideally reversible (or at least non-destructive) way to mark certain positions on a seatpost? A hard scratch would work, but it is not reversible. I have not found a marker pen that works because of: (1) black background (2) it rubs off easily when the seatpost is slid down.

Answer 1

Not a strict answer to the direct question, but an answer to the question of sharing between different people. If you are ready to change the seatpost, having a dropper post is a nice solution when sharing a bike (these are sometimes fitted on shared/rented bikes).

The less fancy ones have levers under the saddles (so no need to mess around with internal or external cable routing), which is not perfect when using it offroad, but when sharing a bike, that is perfect.

The seatpost is adjusted for the tallest person, and for example, with a ribbon of tape, you can mark the position for the smallest one. Then, when you need to change the height, you just need to actuate one lever and adjust the seat (and the saddle remains correctly oriented).

A side benefit of this solution is that such seatpost avoids the use of a quick release (it also works with anti-theft collars), which is a benefit in areas where components theft is an issue.

Answer 2

Some marker pens are more robust than others (especially if there's grease around), and on a black background it's often possible to catch the light and make it much more visible. Taking that a step further, security marking pens that glow under UV light would show up nicely with a suitable lamp.

What I really suggest though is that you mark it as the one you like was marked, with a scale. For black anodised aluminium, you can use a scriber instead of the factory's laser engraving. Better still, a carpenter's marking gauge can transfer a measurement from a ruler to make a nice line around the post, perhaps al the way round every 5cm, with smaller markings every 1cm, starting from the minimum insertion mark.

I keep meaning to scribe my MTB seat post, because I want to mark one height for road (and gravel) where I want to ride seated for a fair distance, and a lower one for proper trails. I'd just mark 2 positions as tidily as I can, but if you've got kids who keep growing, a ruler scale is better.

Answer 3

Rather than marking the seat post you could use the fingers on your hand.

For example:
Nancy's seat is three fingers high.
Bob's seat is eight fingers high - four fingers plus four more.

Each person doing the adjusting would have to remember how many of their fingers were used.

Answer 4

Both permanent silver metallic markers and permanent gold metallic markers work well. They leave a clearly visible mark on the (usually black) seatposts.

After finding that my own handwriting, of lines and numbers, looks less than very elegant on the seatpost of one of my bikes, for my second attempt (image below) I used painter's masking tape and a permanent marker from a popular brand sold in my area.

As you see, the mark itself is perfectly opaque, but the masking tape left streaks. Hence it appears that masking tape is not the right tape for this task. You may want to experiment with simple adhesive tape.

"Why just two lines; and why such fat lines?", you may ask.

This is for the seatpost of a child's MTB (hot off the assembly line).

The two lines mark the recommendation of the trails coach, as well as the child's own preference for a setting that is not as high as the coach suggests.

Why fat lines? Because although nominally permanent, the mark consists after all of just particles on the surface. It will get abraded from inserting and taking out the seatpost. I'd like it to remain visible even after some abrasion.

Answer 5

String and knots

Attach a piece of string somewhere on the underside of the saddle, then add a knot to it for each person that wants to use this system. The knots are spaced so that at the correct height for each person, their personal knot just about touches the quick release (or whichever point of reference is convenient).

Obviously you will have to remember which knot is yours, unless you go with a more sophisticated system that makes them distinguishable. Although realistically, you might very well be the only one using it anyway :)

Answer 6

String and knots has been suggested (and similar) but if you're doing this often, you may want to make a jig. This is a common trick among woodworkers.

Take a single piece of wood, cut everything at the correct angle and so on that it mates cleanly with both ends. It should sit cleanly on the frame seat tube and possibly have some sort of cutout for the saddle rails.

If you are adjusting for multiple people who have known-good seat configurations, each can have their own jig. They could be made out of plastic as well. I have done this in the past with both plastic and wood and it has worked.

I have also scored aluminum seat posts and I've never had a problem with one in over 25 years of competitive riding. The only seat posts I've ever seen shear, other than accidents, were carbon fiber.

I appreciate over-caution but sometimes it just makes things unnecessarily complicated. My bike mechanic always carried a knife in his pocket and he'd mark the post at the frame with it after each fit. But that's your personal choice.

Answer 7

A separate saddle/seatpost for each rider, and a QR in the frame.

For exact height setting, put a piece of tape around the seatpost just-above where it enters the frame, or a better solution is to clamp on a band-on reflector so it rests on top of the frame and acts as a hard-stop.

Do all of you have exactly the same preference for a saddle and saddle angle too? That's unusual, especially across genders.