makeinu

Dollar for dollar, quality for quality, where do you guys suppose the extra weight of folding bikes comes from?

From what I can tell there are probably 4 main areas where folding bikes might be significantly heavier than nonfolders:
1. Solitary main tubes with hinges. Strength for strength the monotube construction is itself probably heavier than a triangulated design. The beefed up hinges must add some weight too.
2. Long folding handlebar posts. Flexible handlebars is one of the most common complaints of folding bikes and many folders compensate with oversized posts and beefier hinges. The Swift (one of the lightest stiffest folders around) notably sidesteps the entire hinge problem by simply not folding its handlebar post at all.
3. Long oversized seat posts.
4. Wheels. Although these should really be lighter than the usual large wheel formats, the kids and BMX markets combined with the commuter demographic seem to skew the availability of rims, tires, etc towards being heavy and overbuilt.

How is the extra weight typically distributed across these categories? In other words, how does a typical folding bike frame weigh compare to a typical diamond frame, a typical folding bike seat post compared to a typical diamond frame seat post, etc, etc?

awetmore

Related to #1 is that most bicycles use butted tubing, but few if any folders do. This allows for significant weight decreases. Since folding bicycles don't use standard tube lengths and place different loads on the tubes most don't use butted tubing.

Folders can be very lightweight. Bike Friday showed a 14lb folder at the Oregon BCA show this year. It used a carbon steerer and a custom lightweight (and aero shaped) seatpost. I bet they'll have it at NAHBS too.

I disagree with you on rim and wheel weights. First off there are many lightweight rims available in the smaller sizes. A second point is that a wheel that is smaller is also lighter because there is less material used. One issue is getting double butted spokes in very short sizes, but the potential weight savings are also lower with the short sizes.

My Swift Folder had a heavy steel seatpost and stem mast. Note that Bike Friday also doesn't use folding stem hinges in any model except for the Tikit.

alex

makeinu

Hmmm, Dahon says that all their aluminum frames use double butted tubing and the Birdy and the Reach from Pacific Cycles are also advertised as using butted tubing.

Which folders don't use butted tubing?

Well, yeah, but at some trade shows you'll see sub 10 pound bikes from nonfolding manufacturers. I'm trying to figure out where that extra 4 pounds is. Mostly in the frame? The seat or handlebar posts? You obviously don't think it's in the wheels. Monotube frames and long posts obviously present a bit of a compromise, but are they equally egregious or do some dominate?

energyandair

Perhaps some of the weight difference is in components. Most really light road bikes seem to have much more expensive and presumably lighter components than the typical folder.

David

pm124

Yes, mine is double or triple butted. It is so paper thin that I worry about it. However, the seatpost is a monsterous 500gms. They make a titanium post in Japan at half that weight. I'm happy to carry around the extra weight given that I had one break on me.

The stem is also very heavy. To eliminate flex, R and M used a thick alloy base. I would prefer a Syntace-style adjustment system over the massive amount of metal approach. The 8Kg Birdies are all pre-2002, before they were reinforced for touring. Without these two parts, the bike would be about 8Kg with my relatively heavy mountain bike/105 parts on it.

My wheels are light, and could be even lighter. Were I to do another custom build, I would probably lace up 14 front (28 hole hub) and 18 rear (36 hole hub) American Classic hubs to an undrilled 369 rim. This would probably be in the 800gm range. As it is, my heavy duty wheels weigh about 1000gms, petty damn light! But yes, there are much lighter rims and tires available for road bikes, after adjusting for differences in size. The Alex rims that came with the bike are thinner and subjectively seem to be better quality than the Velocity replacement rims (no lip, better machine work).

jur

re wheels: For my Swift I tried to make the lightest weight wheels I could. I used American Classic road hubs (58g & 205g), 16 butted spokes front, 28 butted spokes rear, and the lightest rims I could reasonably find, Velocity Aeroheats. The weight came to about 500g F and 700g R. A 1.2kg wheelset is not hyper-light but not bad either. I don't see how that can be further reduced though; lighter rims are not available I think.

chainstrainer

Dollar for dollar, quality for quality, how do you guys suppose folding bikes and non-folding bikes should be compared? My folder weighs 19.4 pounds and cost me $599.00. On a dollar-per-pound weight, how does this compare to a non-folding, quality bike? Let's assume quality of construction in my folder is top-notch, which it happens to be, but convenience of conveyance is not a factor. Any thoughts?

pm124

The only way to go lighter is to reduce your wheel size.

By the way, the lightest Birdy at present is the Speed, which uses Tune components and weighs in at 10Kg. Tune components are lighter than Dura Ace. Moreover, the frame is a stiff and light monocoque, so the new seatpost and stem are obviously much heavier than before.

I would never put in miles on a bike that weighed much under 18 pounds, road or otherwise. I value my life too much. I think that Dura Ace components kind of push the limit of the weight/strength trade off. But it is nice to climb on a light bike, and nicer still to have a light bike when you have to carry it.

jur

I checked the Velocity catalog data for 349 vs 406 rims, and the difference is a mere 30g per rim. The spokes are shorter so that's another saving but surely it can't amount to much? So that would make the smaller wheelset 60g + ??g = maybe 200g? lighter, getting it to an optimistic 1000g. But 800g?? You have to have superlight rims for that. Not sure such exist.

Edit: just recalc'ed the front wheel: hub 58g, rim 300g, so 16 spokes = 140g, that is 9g per spoke+nipple. Shorter spokes can't save more than say 3g, that's perhaps 50g. So a 349 front wheel with 16 spoke would be approx. 500-80=420g. Back wheel, 100g+30g lighter, so 700g-130g=570g. Total, 1000g. Knock another 100g for 16 spokes on the back wheel. So it's getting to 900g. Road bikes have to got to extraordinary expensive carbon rims to get to that sort of figure. But then they have all the advantage in frames at 1kg.

makeinu

Do you have any idea what the frame and stem+post weigh on your Birdy? The long seatposts on folders are obviously way heavier than their shorter, thinner, diamond frame counterparts. Over a pound doesn't seem to be uncommon for a quality folder seatpost that isn't exotic. I imagine that's probably about a pound heavier than the diamond frame equivalent stub seatpost. Of course, the seatpost on a diamond frame mates with its own frame tube.

I'm guessing that, in the end, monotube folding frames are probably about the same weight as diamond frames and that the required extra weight is bumped to the seatpost (which, on a folder, has little or no reinforcement from the frame). Given the fact that some of the lightest folders (bike fridays, swifts, etc) don't have folding stem posts, the weight savings I've seen from stem post swapping on downtubes, and the apparent difficultly of eliminating stem post flex, I'm also guessing that the weight of the stem post is even more significant.

I'd conjecture that overall the stem post probably accounts for about 60% of the extra weight, the seatpost for about 30% and, the frame for about 10% (with, perhaps, a 10% savings on smaller wheels, excluding exotic materials). Although I imagine there would be a difference between hinged and unhinged, I bet an unhinged frame saves much less weight relative to hinged than an unhinged stem post because the frame can be more easily designed to appropriately distribute the load on its hinge whereas the stem post requires a design which loads its hinge in a necessarily unfavorable way (ie stem posts must be overbuilt, including their hinges). Does anyone have any data to support this hypothesis (specifically frame and/or stem post weights and how they compare to diamond frame designs)?

What bike do you have?

jur

A typical good road frame would be roughly in the region of 1.2kg down to 1kg. My Swift frame is about 1.8kg. The fork is about 900g by itself. (These are figures supplied by Peter Reich, I am not sure about how accurate they are and if there are any fittings included.) Road forks which are almost all carbon these days are about 500g. So the frame and fork for the Swift is roughly 1kg heavier than typical road frames.

The seat post is over 500g. My weight weenie post which was about 350g broke last weekend so I'm back on the original. The Swift stem riser is actually quite light, 320g for the SS version and 130g for my custom ally one.

Bacciagalupe

Seems to me it comes from 1) the use of metal instead of carbon fiber, and 2) use of lots of mountain parts.

There are no mass-produced carbon folders, and the ultra-light road bikes use lots o' carbon. Carbon frame, carbon wheels, carbon stem, carbon handlebars, carbon brake levers, carbon seatpost, etc etc

A handful of folders use light road components (e.g. Ultegra) but most use mountain parts, which will be rugged and heavier.

Also, keep in mind that the Pacific Reach does not have a monotube design, and still weighs in at 10kg (22 lbs).

I.e. no one easily replaceable part stands out, IMO.

awetmore

Sun M14A weighs 225 grams in 349mm. I think that is about 50 grams lighter than the Velocity.

J&B still stocks them.

alex

jur

Google didn't turn up a J&B shop, only the distributer. Who are they?

makeinu

Hmmm, interesting. Obviously the frame difference is more than I thought and the stem riser less than I thought. I wonder if the fact that the Swift actually has a sizeable seat tube incorporate into its frame makes its frame a bit heavier than Dahon-esque designs. On the other hand I wonder how much heavier Dahon-esque seat posts and hinged stem risers are.

Do Dahons use longer seat posts than Swifts for the same fit?

That sounds very plausible. For example, look at the Dahon Mu. It's both one of the lightest and one of the heaviest folders on the market, with it's overall weight just about doubling based on component selection. Perhaps the seat post, at around a pound, really is the single component with the biggest difference across the board.

However, I wouldn't base too much about diamond frames on just the Pacific Reach (whose 2008 model is speced at 8kg, btw). Diamond framed folders are a bit of a niche market and I wouldn't expect to see optimal designs. After all, it's only one design.

Speedo

???

I dispute the premise. My BF NWT weighs in at 26 pounds. My Guerciotti steel framed road bike weighs in at, you guessed it, 26 pounds. I'm 6'3", so these are both big frames. Both have triples. Both have 36 spoke wheels. Niether was built up to be very light weight.

Given those bikes as a starting point I suspect that I could lighten them up to the tune of $500/pound, but I consider 26 pounds to be light enough for my needs.

Speedo

awetmore

J&B is a distributor. Most bike shops have accounts with them and can order the rims.

alex

makeinu

Obviously I could go ahead and give examples of comparable folder/nonfolder pairs where the folding bike weighs more. Thats not the point.

The premise of this thread is not to assert that every folding bike in existence is heavier than every comparable nonfolder in existence. The premise is that given a comparable folder/nonfolder pair the folding bike will, in many cases, be heavier than its nonfolding counterpart. Now I've stated this premise as a generality (implying it is applicable to not only many, but most cases), which, depending on how you count may or may not be true. That's not the point either.

If my point was to assert a precise universally encompassing statement about all bikes then I would have done so, but in the interest of brevity and the utility of open forum I've instead decided to layout a general notion and trust respondents like yourself to apply whatever interpretation you find most conducive to sharing information related to the ensuing questions. You have, unfortunately, decided to do the opposite and apply the least favorable interpretation, thus deriving a contradiction and stopping the discussion in its tracks before it even begins.

Why? What advantage is there to choosing an interpretation which leads to contradiction when alternative interpretations are possible? I don't mean to be rude, but I just get frustrated when people do this and was hoping that reading your perspective would allow me to be a bit more understanding.

pm124

I misremembered the weight of my rims. I recall the rims being about 250gms. Are you sure that they are 300? Also, a thin guage spoke is needed for those tiny wheels b/c they have to be bent like crazy. Either way way, your estimates of savings were generous, so I'm sure you are right.

Speedo

Sorry that you're frustrated but

The premise is just plain wrong.

If you compare a $300 Downtube to a $3000 road bike the road bike is very likely to be much lighter. If it wasn't I'd be pretty disappointed in the $3000 bike. If you spent $3000 on a folding bike, a lot of that money would go into the lighter frame and components that would result in a lighter bike.

My NWT and Guerciotti example is very much to the point because they match up with your dollar for dollar and quality for quality qualification. I think if you were taking that condition seriously, and added a function for function qualification (i.e. compare touring bikes to touring bikes and fast bikes to fast bikes) the differences would be peanuts.

Speedo

Fat Boy

I can see the argument that Dura-Ace pushes the limit on the weight/dollar ratio, but they're just fine strength wise. It's light, sure, but it's also strong enough to last years and years.

makeinu

Who says we should add a function for function qualification? Perhaps we should in fact, do the opposite and consider whether perhaps folding bikes tend to be heavier for the very reason that they also tend to serve different functions. Do you seriously think your NWT and Guerciotti example is representative of all dollar for dollar, quality for quality comparisons? Do you really think that there isn't a single folding bike in existence which features a higher weight at the same quality and the same price as a nonfolding counterpart?

The only thing wrong about the premise is your interpretation. The only way such an open ended premise like the one given could possibly be wrong is if all folding bikes weighed the same as all nonfolding bikes, which will obviously never be the case. As long as there remains at least one folder which is heavier than at least one nonfolder then the question of what design features make it heavier will always have a valid premise.

Yet still you continue to insist on applying the least favorable interpretation to, once again, trumpet the incorrectness of what's really just your own interpretation. And for what purpose? There must be thousands of ways to interpret ambiguities in this thread into incorrect statements. What does that accomplish? Am I going to go find some lot of exceedingly heavy bikes optimistically listed for $3000 each on ebay just to say, "Look Speedo, you are just plain wrong these $3000 road bikes are way heavier than my Downtube"? No, that would be absurd because I know your statement implied whatever context makes it valid as did my introduction to this thread. So why are you doing it to me? Why have you decided to pick a argument when you know full well that you could just as easily have said, "Gee, makeinu I think the folding bikes out there which are heavier are probably so because they're meant to serve a different function" or "...because those particular folders are mostly in a lower price bracket where something has to compensate for the extra cost of low volume production and it just so happens to be extra to be beefy folding hinges" or whatever other scenario you'd think forms a valid premise within the context of this discussion?

Speedo

Let's see...

How about a Dahon Speed Pro 22.9 pounds for $1240 vs a Trek Pilot 2.1 at 22 pounds for $1540. Similar prices similar applications 0.9 pounds difference.

If you account for the price difference by a $500/pound rule you get it down to 0.3 pounds. Where's the beef?

Speedo

Speedo

Why didn't you name the thread "Why does this bike weigh what it does?". My contention is that there is very little weight penalty in folders simply because they are folders.

(edit) Meaning that there is very little in the way of extra weight.(/edit)

Speedo

makeinu

Thanks for your input.