Choosing a Dropper Post

MarioM

Likes Dirt
I did do a search but could not find what I wanted . Can anyone offer advice on choosing the right drop on a dropper post ? Will be picking up a new bike shortly and want to purchase a post but don`t know which drop to get 4" or 5 " or doesn`t it matter ? The frame is a small if that makes a difference and I do know what diameter to get . Or is it just a case of working out how far you install into the frame to work out the height in the up position ?

Gee I hope I made sense here .
 

moorey

with a big stick
My rule of thumb. More is better, as long as when fully raised it isn't too high, even when inserted as low as it can go. Measure how much post you have exposed at the moment, if you have it set for pedalling. Allow about an inch for the head of dropper. If you have 6" out, get a 5" dropper. 5 out, get a 4" dropper.
If you have more than 7" out, consider a 6" dropper.
If you have a very low stand over frame, a 4" at minimum insertion, at full lift,mightn't be high enough. I've had this issue with previous 4" droppers in low frames, and I'm a runty chunt.
 

moorey

with a big stick
Best to wait, but if you know seat tube length of both old and new bike, you can make an eddacated guess.
 

Nerf Herder

Wheel size expert
If the store has floor stock of your bike ... ask the store if you can get them to measure the post height at full extension for you

measure from the bottom of the expansion slot on the frame to the bottom of the rails


this gives you max height at full extension as an eg 255mm

Then for your chosen dropper get the max length + minimum insertion line (and max insert depth)

Eg for a 385/125 LEV DX the dimensions are

385mm length
110mm min insert
220 max insert

So the effective lengths are
Max length @ min insert => 385 - 110 = 275mm
Max length @ max insert => 385 - 220 = 165mm
+/- 5mm and depending on how long the frames expansion slot is.

So as for the example with ideal post length of 255mm and presuming the frame can take at least 135mm of post then the 385/125 will suit as 255 falls within the effective post range of 165 and 275mm ... note the difference in static post you will be carrying when the post travel is dropped.

Other considerations are whether you like your post slammed when dropped or prefer to carry a bit of post ... adjust your chosen post length accordingly. eg if you want it slammed you may want to opt for a longer post and travel ... if you like a bit of post then you may opt for a short post with less drop, but carry more of the static post above the seat clamp

eg on my trail bike I was running a 335/100 ... whilst on my AM I ran a 385/125 ... have subsequently gone 125 and 150 respectively as I want to clear steeper stuff at the cost of carrying a little more weight and having to micro adjust post height with my remote more often which comes naturally with practice
 
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