MTB Brand X dropper post size

[Les84]

I am looking at getting a Brand X dropper. I have a M Bizango Pro with a seat tube length of 460.

From the coller to middle of the seat rail is 240mm, what size dropped will I need, I am a little confuse if it’s a 150 or 170.

Thanks

[bobbo89]

The 150/170mm refers to the amount the post extends so you can fit either post, just that a 170mm will drop/rise further giving you 20mm more stand over clearance.

Biggest thing you need to make sure you get right is obvs the seat tube diameter which research suggests is 31.6mm but there's also the cable routing which I suspect the frame won't be stealth compatible..

[Les84]

bobbo89 said:

The 150/170mm refers to the amount the post extends so you can fit either post, just that a 170mm will drop/rise further giving you 20mm more stand over clearance.

Biggest thing you need to make sure you get right is obvs the seat tube diameter which research suggests is 31.6mm but there's also the cable routing which I suspect the frame won't be stealth compatible..

The seat post diameter is correct at 31.6, the cable has a port at the back lower of the west tube for internal routing.

The 170 is obviously longer in the seat tube itself, I assume I would adjust upto the point the seat is 240mm high and then clamp.

My concern is the maximum length in the seat tube.

https://www.chainreactioncycles.com/mobile/brand-x...

https://geometrygeeks.bike/bike/voodoo-bizango-pro...

I have a medium

Edited by Les84 on Wednesday 21st September 10:19

[bobbo89]

You'll have loads of room in a hardtail like yours so don't worry about that, I run a 240mm dropper in a hardtail frame with a much shorter seat tube no worries.

Your current seatpost is extended out of the frame by 240mm, dropper post gives 170mm rise meaning it'll need to protrude from the frame 70mm for it to be set at the same height.

Knock that 70mm off the 499mm (length of a fully extended 170mm post) and your well below the 460mm (centre-top seat tube length of your bike in a medium) leaving 31mm of wiggle room.

Obviously it's your call though and yours to decide whether you actually need 170mm of drop, I;d always fit the longest dropping post I can fit but that's just me. CRC and Wiggle are fantastic when it comes to returns too if should whatever you buy not fit.

[Les84]

bobbo89 said:

You'll have loads of room in a hardtail like yours so don't worry about that, I run a 240mm dropper in a hardtail frame with a much shorter seat tube no worries.

Your current seatpost is extended out of the frame by 240mm, dropper post gives 170mm rise meaning it'll need to protrude from the frame 70mm for it to be set at the same height.

Knock that 70mm off the 499mm (length of a fully extended 170mm post) and your well below the 460mm (centre-top seat tube length of your bike in a medium) leaving 31mm of wiggle room.

Obviously it's your call though and yours to decide whether you actually need 170mm of drop, I;d always fit the longest dropping post I can fit but that's just me. CRC and Wiggle are fantastic when it comes to returns too if should whatever you buy not fit.

Appreciate your detailed reply there mate, if I looked at a 150 for example am I right thinking it will need obviously come out from the frame by 90mm for the total 240 rise but then at its lowest it will be the same as the 170 will be?

[GravelBen]

Les84 said:

if I looked at a 150 for example am I right thinking it will need obviously come out from the frame by 90mm for the total 240 rise but then at its lowest it will be the same as the 170 will be?

Set it for your normal seat height when extended.

Then the 170 will put your seat 20mm lower than the 150 when the dropper is down.

[Les84]

bobbo89 said:

You'll have loads of room in a hardtail like yours so don't worry about that, I run a 240mm dropper in a hardtail frame with a much shorter seat tube no worries.

Your current seatpost is extended out of the frame by 240mm, dropper post gives 170mm rise meaning it'll need to protrude from the frame 70mm for it to be set at the same height.

Knock that 70mm off the 499mm (length of a fully extended 170mm post) and your well below the 460mm (centre-top seat tube length of your bike in a medium) leaving 31mm of wiggle room.

Obviously it's your call though and yours to decide whether you actually need 170mm of drop, I;d always fit the longest dropping post I can fit but that's just me. CRC and Wiggle are fantastic when it comes to returns too if should whatever you buy not fit.

Appreciate your detailed reply there mate, if I looked at a 150 for example am I right thinking it will need obviously come out from the frame by 90mm for the total 240 rise but then at its lowest it will be the same as the 170 will be?

[bobbo89]

Les84 said:

Appreciate your detailed reply there mate, if I looked at a 150 for example am I right thinking it will need obviously come out from the frame by 90mm for the total 240 rise but then at its lowest it will be the same as the 170 will be?

No worries bud, that's right although as Ben above says, easiest way is to just set it how you want it fully extended.

[Les84]

bobbo89 said:

No worries bud, that's right although as Ben above says, easiest way is to just set it how you want it fully extended.

Good bit of info thanks. With the Bizango having cable rooting hole at the bottom of the seat tube will i loose a little bit of room to play with on the 460 number

[bobbo89]

I'm going to assume that the seat tube length on these factors in the slight curve at the bottom just before it meets the BB, the measurement should be that of the straight section of seatpost, essentially what is the max insert.

If it were me I'd just get a 170mm ordered as like I say, always best fitting the biggest dropper you can but if you're anxious just get a 150mm. Like I say though, Wiggle and CRC returns are amazing for if stuff doesn't fit...

[Les84]

Late reply, little update.

They finally gone on sale and went for the 150, hopefully its the right choice.

Thanks for everyone’s advice so far.

[Les84]

Ok fitted today and wasn’t smooth at all but I’m not good at this sort of thing.

Would anyone have any ideas why the seat is wobbling slightly in the seat rails, tightened it up but its still has movement?

thanks