Brompton-esque build; guess the weight

[Brucey]

In a LBS near me they have been building a Brompton-esque bike recently. I say Brompton-esque rather than 'a Brompton' because there are very few genuine Brompton parts in it; most of the parts are aftermarket parts made to 'improve' on the standard specification. The chap building the bike up received a large cardboard box of parts from his customer, which contained

- some duplicate parts (in standard and lightweight versions)
- some missing parts
- some assemblies which needed stripping down in order for the 'improved' parts to be fitted
- some parts that just didn't fit the bike or even one another.

So it was a bit of an e-bay jigsaw puzzle.

The specification is roughly as follows

- Titanium frame, fork, stem, seat pin and swingarm, 'made in china'.
- carbon fibre handlebar and mudguards
- aftermarket wheels for 2s gearing
- Schwalbe marathon plus tyres
- CNC machined ST chainset and flattie pedals
- Brompton 2s derailleur with aftermarket Ti parts (eg main spring, pusher plate etc)
- Brooks professional' saddle
-fancy aftermarket rear suspension buffer
- standard Brompton DP caliper brakes

Now there are other Ti bits and pieces that could have been fitted; brake bolts, pedal spindles and axles for example. And the CF mudguards are CF more for strength, not light weight per se. But you would have to say that most of the parts have been selected to be lighter in weight than the standard ones.

Anyone care to guess how much this lot weighed when built up?

Also whether I was surprised, and if so, in what way?

I'll probably give it a few days before I spill the beans.

cheers

[fatboy]

Marathon plus good for no punctures but hardly light!

15kg is my guess

[Jamesh]

And who the customer was?!!

Michael Hutchinson?

Jeremy vine?

Boris Johnston?!!

Cheers James

[NATURAL ANKLING]

HI,
9.5 kgs.

[ditty bopper]

Titanium goodies with Marathon Plus? Although I use and am a fan of those tires, I just can't imagine using them when weight matters. 14 kgs. (or about 31 lbs. this side of the pond).

[Sid Aluminium]

Anyone care to guess how much this lot weighed when built up?
cheers

A similar spec bike from another forum (not mine):

Lighter saddle & tyres. Guessing the one you saw is a porker in comparison.

[JakobW]

A standard S2L-X is 10.2 kg. Depending on what the wheels are they may not save much over the stock - indeed lots of custom wheels (silly deep carbon etc.) are a fair bit heavier - and the Brompton chainset isn't too bad (apparently a Ti BB is a better way to save weight). With the heavier saddle and tyres I reckon that build will have lost much of the weight savings; I'll go for 9.5kg overall.

[NATURAL ANKLING]

Hi,

A standard S2L-X is 10.2 kg. Depending on what the wheels are they may not save much over the stock - indeed lots of custom wheels (silly deep carbon etc.) are a fair bit heavier - and the Brompton chainset isn't too bad (apparently a Ti BB is a better way to save weight). With the heavier saddle and tyres I reckon that build will have lost much of the weight savings; I'll go for 9.5kg overall.

I don't even know what the bike is or even seen one, it was a guess.
Pick another weight sonny

[Samuel D]

Those tyres are porkers even in Brompton size. The saddle isn’t light either. Some of the titanium bits have no practical lightening effect (e.g. the derailleur bits). I’ll guess 9.8 kg.

[PH]

I don’t know the standard weight, but I’d be surprised if they saved much more than 1kg and shocked if it amounted to 3

[Brucey]

OK, time to tell then.

The shop's scales said 9.5kg, or about 21lbs. Hefting the bike told me that the scales were not far off.

Lighter than standard but I thought it'd be a bit lighter than that.

I guess the tyres/tubes are ~280g porky each,
the saddle is similarly heavy and the mudguards probably weigh about 250g too.

So you could build the bike 1kg lighter quite easily and another 1/2kg wouldn't be too difficult either. But that still leaves a bike (a useless bike with no mudguards, and tyres that puncture too easily for most city streets) which weighs 8 to 8.5kg.

cheers

[rjb]

So I am very happy with my 14.3 kg kingpin over 40 years old now, with stainless mudguards, sturmey dynohub lighting and a rear rack plus frame pump and tool bag.
I would have expected a modern bike to be a lot lighter.
viewtopic.php?f=15&t=3832&start=1590#p1395829

[JakobW]

Vindicated! (As is Natural Ankling of course ) Brompton Marathons are ~420g/tyre; the Marathon Racers are ~280g/tyre, and the bling tanwall Schwalbe Ones are ~173g/tyre. I don't know if anyone makes ultralight inner tubes (latex or otherwise) in Brompton sizes, but you could easily shave nearly 300g in tyres alone; I've done six months' utility and commuter riding on glass-strewn city streets with the Racers, and so far the only problem I've had has been a tack that would have defeated any tyre (I'm sorely tempted by a set of gumwalls purely out of vanity, but the £60 a set premium for pretty but fragile tyres seems daft for a utility bike.)

OTOH, I'm always a bit bemused by weight-weenie Bromptons. There's sometimes a bit of a misconception that because they're folders Bromptons are somehow lightweight. According to Brompton, my M6L weighs in at about 12.3kg, and if I fit dyno lights and a lightweight rack that will go up to maybe 12.8kg. It is a bit of a lump to carry for long distances, especially if I've got another 7-8kg of front bag (with laptop, papers, lunch &c) with me. The point is that the fold is so quick and easy that under most circumstances you unfold and wheel the bike rather than carry it; light weight would be nice, but would cost loads and make for a less practical commuter. The weight's a trade-off I'm happy to make for a bike that will happily carry my 6'5"/16 stone frame with 10kg of luggage on top, then get me onto a rush hour commuter train with no issues.

[Brucey]

IIRC the listed weight I saw most recently for M+ tyres in that size was 480g, but I might have remembered that wrongly. If so I think you could save 280g per tyre without too much difficulty.

However if the bike's utility value is diminished in any way then it just becomes a toy rather than a tool. Myself, I'd worry that the Ti parts are not as durable as the steel ones; it is not as if they come out of the depths of e-bay with a meaningful warranty in most cases. I note also that most Bromptons are not carried far; pretty much up steps only, they are wheeled along (or ridden) elsewhere. This makes the choice between weight and durability a bit of a no-brainer for most folk. Building a Brompton (super-lightweight or not) without either mudguards or rack is about the stupidest thing imaginable if it won't wheel along any more; at least this machine had strong-looking mudguards, complete with wheels.

cheers

[geocycle]

I don't think weight on a folder has much of an impact when riding but it does when you are carrying it to catch a train. My Dahon mu is about 10.5 kg with mudguards and rack and I'd not want anything heavier for a bike that has to be hefted onto luggage racks. I've already damaged my back once!