Originally Posted by
Jipe
2kg saving is a lot and would bring Helix at 9.38kg, still almost 1.5kg more than a Burke and a titanium Brompton. (I do not take into account weight weenies single speed Brompton that weight less than 7kg with the original frame but aren't really usable).
There is not a lot to win on the components: its a "naked bike" with few components, the transmission isn't high end but not heavy, same for the brakes, there are no other tires and no lightweight wheels in ETRTO 507. The only big weight savings on the components would require to use very expensive exotic components for the crank and brakes (something like the THM Clavicula SE crank, the Trickstuff Direttissima brake...). The frame material is already lightweight, only possible saving is by using high end carbon manufacturing for some parts (seatpost, rear arm, fork tube, stem, handlebar, saddle...) but this would also increase a lot the price (look at the prices of Schmolke, AX-lightness, THM...). More weight savings can only happen with a major frame redesign..
First I agree that the weight shaving potential with Helix frameset is not quite good. The design forces non-common 507 wheelset (much less common than 520), which cannot be switched with larger size due to the tight clearance.
The lefty fork only accepts much heavier disc brake system. And you cannot really shave much from the drivetrain either.
And here are some weight breakdown for steel and titanium Bromptons:
Steel frame/fork/rear triangle /stem /seatpost : 2000 + 550 + 780 + 730 + 540 = 4.6kg
Titanium frame/fork/rear triangle/stem/ $40 Carbon seatpost: 1280+280 + 430+460+240 = 2.7kg
Add ~6kg for boat anchor stock Brompton parts
Add ~4kg for cost-effective lightweight parts (wheelset, tire, pedal, saddle, brake lever, hinge clamps etc)
Add ~3kg for extensive but non-bouqitue lightweight parts (which will make 5.7kg full titanium brompton I have built)
Add ~2.5kg for crazy light parts (Clavicula, AX Orion, Schmolke handlebar/seatpost, Extralite hub, carbon rim, ti spoke etc)
So actually the weight loss with boutique German carbon parts are not worth the money. Clavicular SE is only ~120gr lighter than cheap Aceoffix crankset for example.