Brompton suspension block (title changed from 'newbie questions ')

[robjh]

As a very new owner of a second hand Brompton, I notice that there is considerable play in the joint where the rear section clicks on to the seat tube, as in the picture

Is this a normal feature or should I be doing something to make the join more rigid?
It feels like there is a constant flexing as I ride which I find disconcerting, and which feels, with my Brompton newbie's hat on, unsafe.

 

[mitchibob]

Probably switch out the suspension block for a firmer one.

 

[ianrauk]

Probably switch out the suspension block for a firmer one.

This. There are plenty of aftermarket firmer blocks you can buy.

 

[a.twiddler]

Is it the free play that worries you? If you lift the bike the rear triangle will sag a bit, and there's a bit of play there. When I bought mine, second hand, I wondered about the free play but reading these forums soon eased my concerns. On early Bromptons there was no catch at all, and the rear triangle would swing under if you lifted the bike. It was part of the Brompton folding technique, and some might say that having to undo the catch to fold it breaks the rhythm for those who value such things.

You can rotate the suspension block about half a turn which disables the catch, and the rear end will swing freely when the bike is lifted as on earlier models. The catch can be retrofitted to older bikes. The slight play seems to be part of the design. I find the catch useful for when you want to pick the bike up and lift it over things for example, so I leave it engaged.

If you feel a slight flexing, that's probably the suspension doing its job, as long as it's up and down and not side to side. As others have suggested, you can get stiffer rubber blocks if there's too much movement, if you are a heavyweight, for example. It sounds like you just need to ride it and get used to its quirks, so you get comfortable with it, before rushing out and modifying it. There's loads of information on here and on the internet.

 

[steveindenmark]

It is normal. Even in brand new Bromptons.

 

[robjh]

Thanks for the replies. Now that I know it's called a suspension block I'm getting much more successful searches on it!

I can also stop worrying that the bike is going to come apart under me as I'm riding

 

[rogerzilla]

The Joseph Kuosac block is very hard and makes a big difference. It also shows you why the block is there in the first place: it's a way to provide a tolerant, uncomplicated connection that would take some serious engineering if it were a rigid, yet detachable joint. If you hit the wrong sort of bump with the JK block, the lack of compression means that the rear triangle does lose contact with the seat lug, momentarily. It can't flip from under you but it does make quite a clunk.

 

[Tenkaykev]

As I understand it the new suspension blocks are a all a standard stiffness and stiffer than the originals. There’s a video on the excellent Brilliant Bikes YouTube channel where they compare the various suspension blocks and test ride them ( with a camera pointing at the blocks as they’re being ridden. )

 

[berlinonaut]

Is this a normal feature or should I be doing something to make the join more rigid?

As others have said: A little rattle at the suspension block is normal.

It feels like there is a constant flexing as I ride which I find disconcerting, and which feels, with my Brompton newbie's hat on, unsafe.

This may be a hint from a worn rear frame hinge (if it is more of a wobble than of a hopping). Let the rear frame hang loose and try to move the rear wheel sideways, grabbing it from behind. If there is recognizably play (Brompton speak as far as I remember of 2mm at the outmost end of the rear wheel) it is time to change it for a fresh one - a job for a workshop. If there's less or no play you probably just suffer from Brompton newbie paranoia (which indeed may be lindered by a stiffer suspension block).

 

[robjh]

As others have said: A little rattle at the suspension block is normal.

This may be a hint from a worn rear frame hinge (if it is more of a wobble than of a hopping). Let the rear frame hang loose and try to move the rear wheel sideways, grabbing it from behind. If there is recognizably play (Brompton speak as far as I remember of 2mm at the outmost end of the rear wheel) it is time to change it for a fresh one - a job for a workshop. If there's less or no play you probably just suffer from Brompton newbie paranoia (which indeed may be lindered by a stiffer suspension block).

The flexing is front-to-back (or up and down if you like) but not sideways. It probably is just paranoia (but I may also look for a stiffer block).

 

[Tenkaykev]

Speaking of suspension blocks, I saw a post elsewhere where a Brompton owner had customised his block to match the bike’s colour scheme. They’d stretched a coloured balloon over it and snipped the ends of. Simple, cheap and it looked quite effective.

 

[Kell]

I have the Joseph Kuosac rear block as I

a) am quite heavy and
b) this caused w-a-a-a-a-y too much bobbing for my tastes.

I was given the block as a freebie to test - so long as I posted my findings.

Here were my findings. It is a LOT stiffer than the old FIRM block that was fitted to mine. I like it. YMMV.


View: https://youtu.be/BxeEln3X2qs

 

[12boy]

I have a firm block and was a little irritated by its squeaking, even when greased. I put a section of neoprene fuel hose with an ID just big enough to go over the interior bolt inside the block. This eliminated the squeak and increased the firmness as it limited the blocks ability to expand internally. Thousands of miles later it is still firm and doesn't squeak.

 

[cougie uk]

This reminds me I bought the stiffer block and haven't gotten round to putting it on. If only I'd been confined to my house for months on end - I might have found the time...

 

[Tenkaykev]

This reminds me I bought the stiffer block and haven't gotten round to putting it on. If only I'd been confined to my house for months on end - I might have found the time...

I've still got a Joseph Kuosac mid rise bar waiting to replace my S bars. In the meantime I discovered that having the seat post a little lower than it should be for my height takes away that initial "falling over the handlebars " feeling when coming from my M bar Brommies.