Bobbing Titanium Seat post for Brompton

sdawila

Regular
Hello everyone,

I am in the midst of confusion over the use of upgrade material for my Brompton bike. I am confused about the use of titanium seatpost which also results in bobbing when pedaling. and on the other hand the use of aluminium is also very rarely used by Brompton bicycle users.

Bobbing is commonly known amongst cyclist to be a very ineffective because energy is wasted due to titanium flexibility that cause bobbing (movement to left-right shake).

Perhaps anyone can help by giving input or experience on this matter ? Thanks in advanced.
 

Milkfloat

Veteran
Location
Midlands
The material choice on its own has no bearing on the flexibility of the post..
 

Kell

Über Member
I've never experienced it on the standard post.

Plenty of pedal bob with the standard (and even the firm) suspension blocks.

Lots and lots of vibration in the stem, but can't say I've noticed anything untoward in the seat post.

Any vibrations in the wheels get amplified by the length of the seat post and stem, and they're so long on a Brompton, that's what causes a lot of the problems.
 

mitchibob

Active Member
Location
London, UK
I bought a cheap titanium seatpost via ebay from Taiwan I think, primarily to help smooth the ride a bit after fitting Super Firm suspension block. I don't get any bobbing, even at pretty high cadence and I've weighed between 75kg and 63kg since I've had it. However, before getting Super Firm suspension, I would get bobbing at high cadence.

It weighs over 300g less than the standard Brompton seatpost and pentaclip. Not flanged, so can pull straight out, so more nickable, although it's rare that I've left my Brommie where that'd be a problem. I'm not a big fan of the seat attachment, but it does do the job. For 60 quid, I'm not going to complain.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
Its the basic suspension that causes bob. Full Suspension MTBs have sophisticated shocks and pivot set ups to eliminate this, a brompton is very basic in comparison. At worse you may get a mm or so of lateral flex in a seat post, but no vertical compliance, which is where the bob comes from. That vertical compliance is in the bikes suspension.
 

Kell

Über Member
Get a Joseph Kuosac suspension block.

Completely eradicates pedal bob.

In the video below, you can see the bob of me pedalling my bike on a firm block (sat down) versus me stood up bouncing on the pedals on the JK block - no bobbing at all. (apologies for the sound quality - put the vid together on my phone.)

(PS - I'm 15 1/2 stone/95kg)

View: https://www.youtube.com/watch?v=BxeEln3X2qs
 
OP
sdawila

sdawila

Regular
I bought a cheap titanium seatpost via ebay from Taiwan I think, primarily to help smooth the ride a bit after fitting Super Firm suspension block. I don't get any bobbing, even at pretty high cadence and I've weighed between 75kg and 63kg since I've had it. However, before getting Super Firm suspension, I would get bobbing at high cadence.

It weighs over 300g less than the standard Brompton seatpost and pentaclip. Not flanged, so can pull straight out, so more nickable, although it's rare that I've left my Brommie where that'd be a problem. I'm not a big fan of the seat attachment, but it does do the job. For 60 quid, I'm not going to complain.
excellent, do you mind sharing what is the brand ? I might want to get one too but since a friend of mine complained and not happy to one of the best brand for Ti upgrades in brompton.
 
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