Minimum seat post length

Discuss light weight issues concerning road bikes & parts.
Post Reply
Monkeychunki
Posts: 31
Joined: Fri Oct 11, 2013 5:55 pm
Location: West Sussex

by Monkeychunki

Hi, I presume this has been asked before however I can't find any posts.

I have cut back my 3t seat post to the minimum length however I haven't thought about the fact that the seat tube height above top tube differs per bike... is there a standard measurement that should be followed from a frame perspective e.g. 3cm seat post depth from the top of the top tube?
Ridley Helium SL 2016 (M)- 6.08kg
Super6 Evo Hi-Mod (M) - 6.10kg
Caad 10 2013 -7.65kg (Zwift)+ Tacx Neo 21.5kg :)

djwalker
Posts: 165
Joined: Sat Oct 31, 2009 7:35 pm

by djwalker

Every seatpost has a minimum insertion length that is marked on the post. Measure the distance from this line to the bottom of the post. This is the amount of post that needs to be inside the seattube. Once you set your seat height on a particular bike you can cut the post off below the seat tube clamp so that the length of post inside the seattube will be what you measured above. Since the amount of seatpost sticking out of the seattube is usually different on every bike so also will the total seatpost length be different for every bike. So, the post won't be swappable between bikes. And, you also won't be able to raise the seat in the future. For example if you get a different seat. It would be better to leave a few centimeters longer than the minimum for this reason. Note that some seatposts, like my mcfk one, do not allow cutting the seatpost at all.

by Weenie


Monkeychunki
Posts: 31
Joined: Fri Oct 11, 2013 5:55 pm
Location: West Sussex

by Monkeychunki

Ok cool thanks for this it makes sense. I thought that the frame would also have a minimum insertion measurement because I assumed that the seat tube height above the top tube may differ per manufacturer and model. I guess this isn't the case then.
Ridley Helium SL 2016 (M)- 6.08kg
Super6 Evo Hi-Mod (M) - 6.10kg
Caad 10 2013 -7.65kg (Zwift)+ Tacx Neo 21.5kg :)

RyanH
Moderator
Posts: 2199
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

That's actually a fair point and I think the rule of thumb is that it should at least pass below where the seat stays meet the seat tube.

User avatar
Wingnut
Posts: 1884
Joined: Sat Jun 23, 2007 12:41 am

by Wingnut

I usually go about 1 inch below the top tube to be safe...
"It's not the destination...it's the ride!"

Post Reply
  • Similar Topics
    Replies
    Views
    Last post