I am an engineer among other things, though I've never designed a bike. There is no doubt the truss system is as strong or stronger for the weight, but an isolated blow to one of the interior members of a truss would do a lot of damage to the overall capacity depending on whether that particular member was designed for tension or compression. In a dynamic system such as a bike frame, most of the members probably experience both T and C. In any case, my fear would be that should any of those small members go out of plane and become plastically deformed in transit or even from an accident, it could cause the whole frame to buckle depending on what kind of factor of safety is embedded in the design. It is an interesting concept, and fortunately bikes don't tend to undergo extreme loading compared to capacity until you really try to dial in the weight. I'm sure if you promised Moulton you wouldn't gain any weight, they would design a bike with only 5 lbs extra capacity to get the weight down as much as possible. With finite element analysis programs available today it could be done very quickly. The frame would be very fragile and deflection would become an issue if they went too small, but you could still get considerable moment capacity out of space frame of 9 gauge wire.

Oh ... I would not worry about it. This is the point of a forum ... honest discussion.

Have you ever read the Small Wheels for Adult Bicycles article? I only ask since you are new around here. But you may be familiar with the ideas already since you have an engineering background.

I had an idea of what you meant. But I rather just ask. And I think that you have some points. In my opinion, there is a difference between small and large wheel bikes. Performance-wise, the Bike Friday's and any other bike with an odd size take a hit from fewer high-end factory wheels, fewer high-end performance tires, and trickier gearing.

I actually have no idea how heavy a Bike Friday for a large person would be. Although I suspect that only specific sections of the Bike Friday frame would have to be reinforced. But how heavy would a Ritchey built for a heavy person be? I have no idea whether the frame has a relevant weight limit -- I suspect not -- but generally heavier riders have an issue with wheels making the sub-20 pound goal less likely.

Jur,
When I first started racing I saw big muscled athletic types who looked like they were world champs, and quickly found out that they were pretty hopeless on the hills etc, I also saw some older oddly shaped dudes, (who had years of racing under their belts), that were impossible to drop...go figure!!

When we do eventually met one day, let's have a good hard, but fun ride....I've made a few enemies in the past because of my aggressive attacks....:(

Jabbing your frame pump through people's spokes will do that to you. :)

Shhh, keep that secret between you and me, mate....it takes time to master that skill, damn well nearly get the fingers caught at times, and I lament the STI shifters because you can't flick up your rival's gears like on downtube shifters, (SIS). ;)
But the best is a good hard shoulder to the rib cage when winding up for a sprint....what me???...never!!

Makes a lot of sense to me.

[QUOTE=pm124;6010164]I wouldn't want to take Jur on. While there is no real performance difference by wheel size, anyone who can win a time trail UPHILL on a heavy R20 with a hub gear gets my immediate concession.QUOTE]


I agree, and I've checked out Jur's hill climbing times at other locations as well, very impressive indeed, however, I marvel at how you discount my abilities so easily without any inquiries. :D

Has Jur,

1: Raced and trained with Olympic and World Champ riders?

2: Been an A grade or Scratch rider in club and Open events?

3: Been describe as "One of the red-hot favourites" with an Olympic silver medalist in Aust and Sth Pacific champs?

4: Won Open Classic races?

5: Placed 2nd and 3rd in club champs, which club, BTW, is one of the strongest in our state, if not Aust?

6: Blah, blah blah, blah and blah? :eek:

He probably could still beat me though......on a climb at least.

Nah on all counts, very impressive pedigree steve, but I'm strictly a recreational rider, any hill climbing ability is either exaggeration or blind luck. I have a same-age riding buddy who loves climbing to such a degree it is literally all he does, and he is very good indeed. I used to beat him years ago but now he beats me by huge margins. For me the ride is more important than the time taken to do it. So I expect to be trounced in a proper race against you, steve. You can attack me all you want, that won't do much good if I'm already far behind! :D

I think, Jur, with me, it's a case of..."The older I get, the better I was", and those stats are only good on paper really, I should have said they were obtained against armless, legless and brainless trogs....but I won't say that, 'cos it makes me look better. heehee

PS: I didn't say how old the Olympic riders were either...that's my secret.

Hey ... I can lose to both/either of you two guys on any day. ;)

That's the spirit we're in, trying to justify why we will lose before sighting the competition even! :D

It gets all too serious with some older guys however, like they think they're still qualifying for the Olympics. I used to niggle them constantly during races by talking to them and asking, "Why did you do this or that" when they tried an attack or surge. It annoyed the heck out of them and I was often told to 'SHUT @##@%## UP'. To me, racing at times was a big joke, in fact I'm now enjoying being a 'Reci" more than competition.....well, sometimes.

I'm just under 300lbs and have no problem with a Bike Friday NWT. Was even heavier when I ordered it :)

Yes, I've discovered how wrong I was. It seems only their stock bikes have limits, and even then only the smallest (tikit, pocket crusoe) have "small" limits. Their others can be made to support quite a bit, and even the tikit made to order. I'm a believer, the kool-aid tastes great.