Underneath a Brompton....

[richrboo]

Hi

Is there meant to be a sleeve in the lower section of the seat tube on a Brompton? Below is a photo of mine, looking from underneath and inside the seat tube it is unpainted.

Is this a problem area that needs regular cleaning?

I assume the seat post going through the bottom of the tube pushes out dirt each time the bike is folded, but wondered if other Brompton owners pay attention to it?

Rich

 

[Schwinnsta]

No, nothing should be there. Yours looks correct but your rear tire does not look centered.

 

[Inertia]

Hi

Is there meant to be a sleeve in the lower section of the seat tube on a Brompton? Below is a photo of mine, looking from underneath and inside the seat tube it is unpainted.

Is this a problem area that needs regular cleaning?

I assume the seat post going through the bottom of the tube pushes out dirt each time the bike is folded, but wondered if other Brompton owners pay attention to it?

Rich

View attachment 538596

I think Bromptons come with a sleeve for there which can be positioned to enable you to easily know when you have raised the seat to the correct height. Its not recommended if you use varying heights, i.e. more then one person use the bike.

 

[Gunk]

I think Bromptons come with a sleeve for there which can be positioned to enable you to easily know when you have raised the seat to the correct height. Its not recommended if you use varying heights, i.e. more then one person use the bike.

The seat position sleeve is situated by the clamp, you can’t see it from underneath the bike.

 

[Inertia]

The seat position sleeve is situated by the clamp, you can’t see it from underneath the bike.

Thanks for the correction. I knew there was a sleeve that came with them, so thought that may be what the OP was talking about.

 

[richrboo]

No, nothing should be there. Yours looks correct but your rear tire does not look centered.

Thanks. Though I'm now worried about the rear wheel! Having a look and the rear wheel is closer to the right hand side of the triangle, than the left side. The right hand side of the rear triangle is bent inwards to accommodate the tyre. I assume if the wheel is out of line then I would have issues with the brakes and mudguards. Aren't all Bromptons rear wheels like this?

 

[Schwinnsta]

I believe it should be centered. If your concerned about the frame, fold the rear triangle and see if the wheel is concentric with the main tube. Hopefully, all you need to do is center the wheel.

 

[berlinonaut]

Thanks. Though I'm now worried about the rear wheel!

No need to worry. Your pic looks completely normal, the rear wheel is not supposed to be centered between the chain stays and it is not on any Brompton. Trouble with forums is that it is hard to distinguish between information and claims and a lot of posters do post (false) claims and call them information...

I believe it should be centered.

You believe wrong.

 

[rogerzilla]

The rear tyre should line up with the seat tube but it will look off-centre in the "rear triangle".

 

[midlife]

Just out of curiosity why does a Brompton rear wheel not sit in the middle, is it something to do with the fold?

 

[MichaelW2]

Is the bottom bracket shell offset from the centre line of the frame?

 

[berlinonaut]

Just out of curiosity why does a Brompton rear wheel not sit in the middle, is it something to do with the fold?

It does sit in the middle of the frame, but not in the middle between the chain stays at the rear hinge, probably due to the folding mechanism and the OLD being just 112mm on a Brompton in opposite to the 135+mm on a normal bike. On many normal bikes you still do have the same situation.

 

[MichaelW2]

Assymetric or offset chainstays have been used with std 135mm hubs and dishless wheels in the Pace RC100 and Orbit tourer. It must have been a 1990's thing.

 

[Schwinnsta]

Mine appears centered, hard to tell with fenders. Rear brake appears centered as well.

 

[berlinonaut]

Mine appears centered

In this case your bike may have a problem... From simply looking at Brompton rear frame:

What do you think: Why is there a dent in the chain stay on the drive side and none on the none drive side? When looking on a Brompton from above with the rear frame folded: How come that the dropout of the non-drive side is sticking out far more than the one on the drive side? You can see it in the picture above as well but not as good.

So if your chain stays really do have the symmetric distance from the tire your rear wheel is not in line with the frame and your Brompton has a defect...