Brompton how light can it go

[jackthelad]

I was reading about the titanium 2 speed brompton and it comes in at 9.6kg.I was wondering if this bike could go lighter with hand built wheels,carbon seat post etc,what are your view any appreciated

 

[Flying Dodo]

You could do all the above, which would certainly reduce the weight a bit. It would be fairly expensive though.

If you really wanted to go any lighter, you could try using helium for the tyres.

 

[TheDoctor]

It's getting tricky to find things to lose weight from, without compromising the bike beyond all usefullness.
I mean, would you really go single-speed to drop a hundred grams or so?
Shame no-one makes a carbon main frame...

 

[Night Train]

Shame no-one makes a carbon main frame...

Yet!

I am sure now you have said it someone will start thinking about how much a Brompton fan would pay for one.

 

[TheDoctor]

I'm starting to think about liberating some carbon pre-preg from work.
And an autoclave...

 

[JC4LAB]

Just as important is how light can you yourself become....as a 17stone Brompton user myself Ihave given up light bikes. Body weight would be much easier and cheaper to get off....Titanium oiptions would be more for strength than weight reduction in my case.. eg..as a heavier rider I find seat post stems can bend just a touch over time making them a tough fold.Steel ones are cheap to replace though at a fifth of the price of titaniuim)..

 

[RecordAceFromNew]

Given it is something you carry around with you imho the OP asked a fair question. Unfortunately having looked into it a little bit I think challenges are considerable. I am happy to be proved wrong though.

Lets take the seatpost, over 53cm of tube with the standard weighing about 400g. When you consider a typical light carbon post about half that length typically weighs about half that, it becomes obvious that lightening it is not going to be a very promising exercise - especially when bending moment at the clamp increases when doubling the length. Unsurprisingly perhaps that is why Brompton used to sell a Ti post. Also unsurprisingly a current 3rd party Ti post weighs about the same as the steel one despite costing 200 euros. To make matter worse, if you have long inseam like me and need the current telescopic post you will need to carry another 360g!

But the main reason why it is challenging is because so few components are consistent with modern standards where choice is plentiful. Certainly not the hubs, nor the brakes, nor the BB. If you want to get away from a heavy (unless very expensive) 119mm square tapered BB by changing the chainset at the same time, you will find it hard to get a chainset as light as the existing Stronglight 55.

Lighter saddle, tyres (e.g. Kojak) and tubes are probably the easiest avenues, if not taken already.

 

[Red Light]

A guy, Len Rubin from the US of A has developed the "Ultimate folding bicycle" a titanium framed Brompton with a target weight of half that of the standard Brompton. Rumour was at one time Brompton were going to make them but that seems to have evaporated. His website is www.ufbusa.com

 

[TheDoctor]

Given it is something you carry around with you imho the OP asked a fair question. Unfortunately having looked into it a little bit I think challenges are considerable. I am happy to be proved wrong though.

Lets take the seatpost, over 53cm of tube with the standard weighing about 400g. When you consider a typical light carbon post about half that length typically weighs about half that, it becomes obvious that lightening it is not going to be a very promising exercise - especially when bending moment at the clamp increases by a factor of 8 when doubling the length. Unsurprisingly perhaps that is why Brompton used to sell a Ti post. Also unsurprisingly a current 3rd party Ti post weighs about the same as the steel one despite costing 200 euros. To make matter worse, if you have long inseam like me and need the current telescopic post you will need to carry another 360g!

But the main reason why it is challenging is because so few components are consistent with modern standards where choice is plentiful. Certainly not the hubs, nor the brakes, nor the BB. If you want to get away from a heavy (unless very expensive) 119mm square tapered BB by changing the chainset at the same time, you will find it hard to get a chainset as light as the existing Stronglight 55.

Lighter saddle, tyres (e.g. Kojak) and tubes are probably the easiest avenues, if not taken already.

I agree, it's a fair question. I'm just stumped for an answer!!
Loving the idea of a Ti Brommie though.

 

[Brommyboy]

You can spend as much as you like on lightening the bike: try these for saving a 20 grams at about £30 -
http://www.brompfication.com/39-hinge-clamp-lever-bolts-titanium.html

 

[mickle]

One word; Steve Perry.

 

[dellzeqq]

that's two words

 

[mickle]

Good point.

 

[jackthelad]

guys I came back to this post as some guys have related to small items to save a few grams here and there.This is not what i was getting at but basically making the bike lighter.Has brompton looked into other materials like more titanium in the frame or selling the frame seperately so people can build the bike with hand built light wheels folding tyres etc.What do you think the limit weight would be on a brompton to make it for what it is intented for,(carrying)

 

[Yellow Fang]

I suspect none of Brompton's tubes are double butted, Actually, there are only basically three tunes that are worth double butting: the head tube, the main tube and the steerer. It has to be said Bromptons are heavy to lug about, especially from one station platform to another.