Brompton superlight weights

[rogerzilla]

Just because it's difficult to see how this breaks down, and I've done some research.

Brompton quote a saving of 790g to 1050g depending on version (the E model with no mudguard can't save anything on the mudguard stays) and seat pillar length.

Let's assume an L or R model:

Steel fork: 532g inc crown race
Ti fork: 276g inc crown race

Steel rear frame: 755g
Ti rear frame: 468g

Pump: about 80g (mine lost its red rubber crud ring), omitted on the -X models

Add that up and you have 623g, although omitting the pump's a bit of a cheat because you'll need a mini-pump or CO₂ instead.

Brompton quote a 50g saving for the current aluminium seatpost, although ISTR the saving was greater for the old Ti seatpost.

673g so far.

The superlight front wheel is claimed to save 85g.

758g so far.

And then you have an alloy headset (guess at 50g saving), Ti mudguard stays (say 50g again) and a Ti folding pedal bolt (20g?).

So it all adds up to around 878g, which is in the middle of the range quoted.

Of all the parts, the best g/£ saving is just leaving the pump at home    After that, it's all much of a muchness.  The rear frame is by far the most expensive upgrade, but saves 2/3 of a pound of unsprung weight.

[LittleWheelsandBig]

Tyres are pretty good in the grams/£ ratio.

[Majorbloodnok]

Tyres are pretty good in the grams/£ ratio.

Rolling weight....best weight saving investment I reckon

[rogerzilla]

But for some reason they don't put lighter tyres on the superlight.

[Biggsy]

Rolling weight....best weight saving investment I reckon

Debatable, especially with small wheels.

Rotational Weight

[LittleWheelsandBig]

But for some reason they don't put lighter tyres on the superlight.

I do, Kojaks are the go.

[LittleWheelsandBig]

Debatable, especially with small wheels.

Debatable perhaps but not "especially with small wheels."  Run the numbers, 100 g off the tyres is worthwhile regardless of wheel size.

[iakobski]

Rolling weight....best weight saving investment I reckon

Debatable, especially with small wheels.

Rotational Weight

The debatable bit is only about climbing.

Rotating weight is definitely worth more than non-rotating weight, especially on a bike used for town/city riding.

[Biggsy]

Debatable perhaps but not "especially with small wheels."  Run the numbers, 100 g off the tyres is worthwhile regardless of wheel size.

Could you run the numbers for me, please?  How much quicker can you accelerate from, say, 5 to 20mph with the same power and 100g off each 16-inch tyre?

Of course there's an advantage, but I wonder if it's less than commonly thought.

(I'm not trying to dissuade anyone from saving weight anywhere, by the way, as I'm a bit of a weight weeny myself - but we shouldn't get carried away in thinking there's more benefit than there is).

[LittleWheelsandBig]

Could you run the numbers for me, please? 

Sure, as soon as you put the measurements in metric. 

Perhaps it would be better to work out how much the lighter bike and rider would be ahead of the heavier one.  A 0.001 g improvement in acceleration doesn't sound like much but gaining a wheel length is useful for a racer.

[Biggsy]

As we're discussing rotational weight, we should compare the difference in acceleration of 100g off each tyre to 200g off a static part of the bike.

10 to 30 kph with 385 423mm tyres

[Cheysintow]

I've owned the 2009 ti raw laquer super light s type with all the bells and whistles(SXL3?) for a year. The best thing is the easy wheels. Where bikes are not allowed, I fold everything but leave the seat post up and wheel it like that. However with the S bag fully loaded it can fall over in this stance so I stand on the titainium rear rack when its staionary. Because of this the rear rack is a little bent.

So I say, it doesn't really matter how light you bike is, just get easy wheels and let your bike carry all your stuff. Remember to push the seat post down if you are tacklijng stairs. Right I best go scalp some more cyclist in Cambridge.

[rogerzilla]

Here's how it adds up, since I now have two to compare.

S3L-X with all the titanium parts (including the discontinued seatpost), a Flite saddle and Kojaks.  No pump, obviously, because the Ti rear triangle omits the bracket! Weight-adding items include AM hub internals (not much more than an AW or SRF3), 52 x 15 gearing*, leather grips, stubby bar ends and a couple of light brackets.  XTR SPD pedals.  23lb.

M3L with the extended steel seatpost, Marathon Plus tyres, a Charge Spoon saddle, 44 x 13 gearing , cork grips, SON front hub, Cyo headlamp and Brompton battery rear lamp.  Stock Brompton pedals. 28lb.

Both bikes have Eazy wheels, proper Sugino XD cranks, a Shimano BB. mudguards and Sturmey-Archer trigger shifters rather than the plastic Brompton shifter.

5lb is a huge difference.


*the additional chain required probably adds more weight than the sprockets themselves

[Jurek]

FWIW
I've just put mine on the scale,
2-speed.
Flat bars
Ti forks & triangle
Marathon plus rubber.
The rest is bog standard
= Just shy of 11kg.

It is not a lightweight bike.

[1nterceptor]

 The changes I've made to lighten my bike helps me carry it up and down the stairs at my job and at train and bus stations. Maybe you don't climb 3 floors of stairs so a lighter bike may not make a difference to you - but for me it helps. I also volunteer on a lot of charity rides. By lightening things that rotate; pedals, chain, chain ring, tires, etc. - I'm able to ride 100 miles and more at a decent clip. Again if you only ride 1 mile to the train station, a bike that's quick to spin up to speed may not interest you.  In this video I'm able to keep up and pass roadbike riders(on flat sections and uphills):

https://www.youtube.com/watch?v=ROYHoXiJNOM&index=7&list=UUHyRS8bRu6zPoymgKaIoDLA

[rogerzilla]

Yes, due to their value I keep them in the house rather than the shed, and getting the M3L upstairs is a challenge.

[Kim]

The changes I've made to lighten my bike helps me carry it up and down the stairs at my job and at train and bus stations. Maybe you don't climb 3 floors of stairs so a lighter bike may not make a difference to you - but for me it helps.

Is the strongest argument for keeping a Brompton-type folder as light as possible, especially if you're relatively short (ie. it would touch the ground if held in an extended arm).

I went for knee-friendly gearing rather than lightweight on mine, as that's more important for how I use the bike.  It's not light at 14.2kg.  While I'll carry it up the odd flight of steps, I try to use lifts for the downward direction, and generally wheel/roll it (with luggage attached so I don't have to carry that) wherever possible.

[1nterceptor]

I ordered my 6 speed with reduced gearing(44T). But it was still not low enough for the hills in my area.
I swapped the original chain wheel/ring to a Shimano 10 speed Dura Ace 39T ring. Now I can ride up steep
inclines where other riders(all kinds of bikes) usually walk:

https://www.youtube.com/watch?v=5AT6wI_J2MI&list=UUHyRS8bRu6zPoymgKaIoDLA&index=15

I also swapped the chain to Shimano 10 speed Ultegra. That along with other changes I made; ti seatpost,
ti pedals, carbon/ti seat, various ti nuts and bolts - made my S6L-X weghts about the same as a S2L-X:

https://www.flickr.com/photos/44332608@N03/16805771311/in/dateposted-public/