Originally Posted by
linberl
Uh, you must have an interesting idea of "not too much". The single speed titanium is what, 22 lbs stock. Before you drop 5 pounds off it somehow and at some price, you need to add in weight for some gearing to be more or less equivalent with the other lightweight bikes mentioned. With Brommie, you're capped out at 6 but that probably adds what, at least 2 pounds? So now you've got to go from 24 down to 17 "without spending too much". Seven pound drop cheaply, I don't think so.
Actually now we can do that thanks to cheap aftermarket titanium, carbon and CNC aluminium parts.
Steel frame + fork + rear triangle + handlepost weighs around 4.2kg, Full titanium setup weighs around 2.5kg.
I have built a full titanium Brompton clone that weighs 12.7lbs. If I just transfer parts to steel Brompton frameset, it will be ~7.5kg or 16.5lbs.
And if you start from superlight version with titanium fork and rear triangle, it will be ~6.8kg or 15lbs.
For gearing, many forks are now using 3 cogs (11-14-19T for example) or even 4 cogs (11-13-17-21T) now, which somewhat helps the gearing problem.
Originally Posted by
linberl
And just the seatpost for the Brompton is $200 USD in titanium, not exactly inexpensive. Sure you can do it, but it costs big bucks. Folks who bought a Helix got one hell of a bargain imo, and the changes they need to make to drop weight aren't all super expensive, just some of them.
It is indeed quite puzzling why they included a very expensive to make titanium seatpost - it's not even a standard design and needs additional welding point.
That said, now you can get a two bolt titanium seatpost for brompton (31.8x580mm) for around $80 shipped.
Of course it is way more expensive than aluminium one with similar weight (I got one at $20 shipped!)
And much lighter carbon fiber one is now around $40-50. I am using two of them, one for the titanium Brompton clone and one for TSR.