Help finding a dropper post

donslow

Hey all,

I’ve decided to bite the bullet and invest in a dropper post, problem being, it’s such a minefield of information, I’m not sure which size dropper to get

Here’s what I do know...
-Seat post diameter 30.9mm
-Seat currently set at 220mm from bottom of rails to top of seat tube
-Internal seat tube clearance from top of seat tube to where ruler stops going down 360mm
-External measurement from top of seat tube to top of internal routing lug 280mm

Any advice on what drop I should be looking at would be a massive help

reaperactual

Great, you have all the measurements you need to compare with a dropper post's measurements.

Although you will get a better idea of max insersion depth by dropping you current seatpost down to check for there are no internal seat tube obstructions like bottle cage bosses etc.

Example:- Check out this Brand X dropper post. Scroll through the images (No 8) for the full diagram and measurements for each of the dropper travel options.

Ideally you want the highest dropper travel possible within the space (220mm ish, stack height) you have to play with.




https://www.chainreactioncycles.com/brand-x-ascend-dropper-seatpost-125mm-150mm-/rp-prod149024

donslow

reaperactual said:

Great, you have all the measurements you need to compare with a dropper post's measurements.

Although you will get a better idea of max insersion depth by dropping you current seatpost down to check for there are no internal seat tube obstructions like bottle cage bosses etc.

Example:- Check out this Brand X dropper post. Scroll through the images (No 8) for the full diagram and measurements for each of the dropper travel options.

Ideally you want the highest dropper travel possible within the space (220mm ish, stack height) you have to play with

That’ll be what this measurement was
“-Internal seat tube clearance from top of seat tube to where ruler stops going down 360mm”

Speaking with the LBS this morning (had my bike there with me) he seemed to think I should be looking at 125mm drop, he made it sound legit but your potentially saying I could get away with more or am I reading it wrong?

donslow

In hindsight, he MAY have been looking at the measurement from the top of the seat tube to where the internally fed cable would come out (280mm)

I think he was also bearing in mind the potential collar size of a dropper which obviously takes up some of my 220mm stack

reaperactual

Dropping your sestpost down rather than a ruler will make sure there aren't any internal narrowing or obstructions that may not be visible.

reaperactual

A 125mm dropper would probably be a safe bet but it might not need to be fully inserted so your saddle might not be as far down and out of the way as it could be with a 150mm dropper when dropped.

An ideal scenario would be dropper fully inserted with collar touching top of seat tube and the top section not being too long when fully extended to a point where you can't comfortably reach the pedals. If you can get away with a longer travel dropper that will fit within the overall stack height it would be better.

Sorry it's hard to explain, hopefully you can work out what I'm trying to say with the above?

donslow

Makes perfect sense, if I have read this right....

Basically the dropper travel should be as long as your seat tube can handle without it being longer than your stack when fully extended

Something like that? Look who’s having difficulty explaining now ha ha

reaperactual

Lol, funny how simple points are so hard to explain sometimes.

I bought a bike with my very first dropper installed which was 150mm travel. Didn't pay any attention or give a second thought to it.

When my bike arrived the dropper was too high for me when fully inserted (with the collar touching the seat post clamp) and I was still stretching to reach pedals!

The section and measurements below the collar are all to do with the dropper fitting in the bike frame, the section above the collar (whatever the travel) is a personal fit specific to the individual user. This is a lesson I learned the hard way.

Too tall and it just won't work for you, less travel (and stack height) is definately the safer option because the only consequence is the seat won't go down as far as a fully inserted dropper.

Thinking about it, realistically we're only talking about an inch higher at most when dropped between a 125 and a 150mm travel dropper.

steve_sordy

Great responses from @reaperactual He pointed you to the same website and gave the same advice that I would have done.

With the dropper fully extended and the body fully inserted into the seat tube, if the saddle is still too high for you..... Do not convince yourself that just using the dropper's capacity to drop will solve the problem. It won't!

I had this on a YT Capra that came out of the box like that. It was only about 10mm, and yes the saddle will drop and you can get it perfect before you set off. But not when you are riding ! After I had used the dropper, I could never get the saddle to the correct height whilst pedalling over undulating terrain. I was on the point of buying a new dropper when the 150m travel dropper failed and I was able to replace it with a 125mm version. Happiness in abundance!

donslow

Thankyou guys, very much appreciate the time and effort

@reaperactual seems to becoming my own personal bike advisor, every time I put up a post, BAM! He’s there with help ha ha

@steve_sordy some valid points you make

So if I have this right, my current stack is at 220mm so providing I can get 220mm above my seat post, fully extended, including collar, and providing all fits nicely into my seat tube, and with the minimum insertion point within, I should be set?!

Correct me if I’m wrong but theoretically, if I have say, 150mm dropper with 30mm collar I’d be looking at the collar about 40mm above my seat post?! But then probably not as the seat MAY take up that 40mm anyway

Or have I got this wrong and I’m just reading too much into it?! Apologies for the stupid questions

donslow

Have just read this

“To choose the correct travel dropper post, measure from the seatpost collar to the seat rail (in your climbing, or highest setting) on your current bike. Subtract 50mm from this measurement and the resulting number is the maximum travel length dropper post you can comfortably run.“

So this is suggesting 170mm :-s

donslow

But looking at the diagram @reaperactual sent over, I THINK 125mm might do it it it doesn’t give measurements from top of travel to seat rails so with 125 I might need som of the dropper post above my seat tube top, the same could be said for the 150mm also

Hmmm, Might order the 150 and return if no good

Hmmmm decisions decisions

mully79

What bike do you have ?
170mm as long as your frame can take the length of the dropper. (see reapers first post)

if it bends or has bottle bosses double check for obstructions.

reaperactual

I went back to the diagram on C.R.C. and remembered how damn complicated it is! 🤯

So the overall length of the 150mm dropper is 459mm, the length from the very bottom to the bottom of the collar is 254mm.

= 254mm is the max insersion figure.

Maths isn't my strong point and not too confident I'm on the right track here but I think that would make the rest of the dropper from the bottom of collar to the centre of the saddle rail mounts 205mm?🤔

donslow

reaperactual said:

I went back to the diagram on C.R.C. and remembered how damn complicated it is! 🤯

So the overall length of the 150mm dropper is 459mm, the length from the very bottom to the bottom of the collar is 254mm.

= 254mm is the max insersion figure.

Maths isn't my strong point and not too confident I'm on the right track here but I think that would make the rest of the dropper from the bottom of collar to the centre of the saddle rail mounts 205mm?🤔

That’s what I’m seeing, so On a 150mm brand x dropper I’d need approx 15mm of the post above the seat tube, not so terrible really (but the diagram measurement doesn’t show up to the rails)

A buddy of mine recently bought the 150mm brand x dropper so I’m gonna get him to measure from the collar to the rails and see what’s what

mully79 said:

What bike do you have ?
170mm as long as your frame can take the length of the dropper. (see reapers first post)

if it bends or has bottle bosses double check for obstructions.

It’s a 2018 Dartmoor hornet, pretty straight seat tube with no obstructions as I can tell (measurements on first post)

reaperactual

I reckon you'll be safe with the 150mm travel with your current saddle to top of seat tube at 220mm, 15mm up isn't going to be noticable.

If the theory and maths is correct that would make a 170mm travel dropper put your saddle at 225mm? As you say given the small discrepancy (3.5-7mm?) with the final clamp and rail position I reckon that is just a little too close for comfort to attempt to fit?😬

reaperactual

donslow said:

Thankyou guys, very much appreciate the time and effort

@reaperactual seems to becoming my own personal bike advisor, every time I put up a post, BAM! He’s there with help ha ha

@steve_sordy some valid points you make

Lol! Just spotted this. Covid, lockdown, furlough innit!😆

If you fancy splashing out the cash my second go to recommendation is usually the One Up Dropper Post.

Heard good things, made for max travel in limited space and can be customised to fit better using shims.

https://www.oneupcomponents.com/products/dropper-post-v2

donslow

@reaperactual i believe you’ve done it again! Ha ha

Had a sit down, cuppa and a flush of brain of the info I’ve read to start again clear headed

Reading this....

reaperactual said:

I reckon you'll be safe with the 150mm travel with your current saddle to top of seat tube at 220mm, 15mm up isn't going to be noticable.

Made me realise I was over thinking / complicating things and it really is as easy to work out as measurement(s) a, b & c

Think 150mm on most droppers would do it, but at least now I can see what I’m looking at with relatively educated eyes

Gents, thankyou once again

@reaperactual .... will look forward to hearing from you when I have another issue ha ha

reaperactual

Ah yes, a nice cuppa, a sit down, looking again with fresh eyes and it just clicks.😇

Then you wonder why it mashed your brain in the first place?🤪

Same story for me too except I took longer to work it out! 😟😆

Happy shopping @donslow. 😎