Folding Bikes - Interesting article on folding bike handling

Probably an older article featuring an early Dahon:

http://www.johnforester.com/Articles/BicycleEng/dahon.htm

this article is completely out of date and only applies to the first Dahon models- they have been continually redesigned since then and the comments in the article no longer apply

I like that article and have posted it on other folding bike web sites/wikies.

I think this is a problem with many folding bikes as they need to make tradeoffs in performance to get a small fold. On the other hand taking a bike with 16" wheels to 20 mph is an act of depravity. My Strida's steering is completely unstable, and causes some embarrassing starts, but since I keep it to 10mph or usually less it is no problem. On of the 'dirty secrets' of folding bikes is that they look sporty but are really only used for low and moderate speed riding, which is what I do.

One test of a steering system is to ride it no hands. I think it is interesting that the Raleigh 3 speeds have an even shorter 'trail distance'. I am tempted to get one just to see how it rides.

If you want a performance bike I think it has to be like the Moulton and separate in the middle.

I wonder if the Dahon Mu is any better.

geo8rge, comparing a Strida with a real bike is a bit of a stretch...

I have ridden my 349-wheeled Moulton and Brompton no-hands and considerably above 20mph, sometimes at the same time, YMMV.

Just because AM doesn't like folding mechanisms doesn't mean that they are inherently weaker or more flexible than a separable joint. A Stowaway joint is not a very impressive piece of engineering, for instance.

I have ridden my 349-wheeled Moulton and Brompton no-hands and considerably above 20mph, sometimes at the same time, YMMV.
Ditto the Brompton, add a Dahon and Bike Friday 20" as well.

Getting up to and over 20mph is not a problem – maintaining that speed is (for most, I'll wager). Handling is not an issue for the aforementioned.

Strange george - I can ride my strida3 hands off, but not my Brompton L3. Maybe yours has a fault ?

On of the 'dirty secrets' of folding bikes is that they look sporty but are really only used for low and moderate speed riding, which is what I do.

Says who - I don't think many people would call the standard Brompton sporty? A lot of riders may only go at a moderate speeds, but a fair proportion can comortably maintain higher speeds. Different bikes, for different folks...

My point is most folding bikes make many trade offs to achieve folding. That is an obvious fact. That is not to say that some bikes do it better, but folding such that the wheels meet after folding seems like it is a trick that is hard to pull off. Manufacturers also doubt they will not be rewarded with a higher price for the extra expense. There may be exceptions, perhaps the new Mu from Dahon. A Birdy I am working on seems to be stable wo hands.

As to being able to ride without hands, Strida is an extremely unstable bike even on flat terrrain. There are full sized bikes I can ride, make turns, use a cell phone ect while riding. Strida I can barely get my hands off the handlebars before it starts feeling it is coming undone.

Needless to say there are other reasons not to go fast on a bike with 16" wheels, namely they are easier to tip over as the pivot point is lower, and the wheel gets caught in smaller holes. Night riding is also much more complicated as you cannot count on seeing holes before you hit them.

Another point I think is obvious is that they use large diameter wheel in bike racing and other competitive bicycle events because they work better than small diameter wheels.

Another point I think is obvious is that they use large diameter wheel in bike racing and other competitive bicycle events because they work better than small diameter wheels.

geo8rge, read up about cycle history and think about "path dependance". Obvious isn't necessarily right...

Needless to say there are other reasons not to go fast on a bike with 16" wheels, namely they are easier to tip over as the pivot point is lower, and the wheel gets caught in smaller holes. Night riding is also much more complicated as you cannot count on seeing holes before you hit them.


I agree with everything you said. The only time I ever went over the handlebars was on my 16' wheel Piccolo. I was night time riding and the front wheel was swallowed by a wave.

Another point I think is obvious is that they use large diameter wheel in bike racing and other competitive bicycle events because they work better than small diameter wheels.

I recall (vaguely) that small wheels are often illegal in cycling competitions.

Although the nature of racing/competition and recreational riding are quite different. My physics is very rusty, but I can guess at a few reasons why a wheel size that is optimal for 30 mph is not optimal at 20 mph.

Personally, I think the big disadvantage of small wheels is the effect of big holes, logs, i.e., big wheels rise and fall more slowly. Otherwise, for my personal tastes, I think that the rest of the pros and cons are a wash.

I do think that you are correct that folding bikes must be disadvantageous from a performance perspective. As you write, it is obvious.

I do think that you are correct that folding bikes must be disadvantageous from a performance perspective. As you write, it is obvious.

I haven't raced with it, but on the DT Mini (16") i only notice that the steering is way more responsive; when you're rolling in a straight line, i don't feel any difference at all, except that my Mini is so light that the effects of inertia (for breaking, accelerating, etc.) are far less juggernaut.

I only ride on a bike lane for about 15 blocks, and then on a bike path along the Hudson for 4 or 5 miles. But, I've never seen a road problem or hole that made me even blink. (Fools do rush in, though.)

On my inaugural ride I rode with way too underinflated tires on the large white gravel along a train tracks. (See Fools, above.) Hardly smooth pavement - but though I couldn't go too fast, I had absolutely no problem with balance or tipping.

Basically, I feel like the Mini is a Mountain Bike (in terms of posture) that books (in terms of efficiency). It's almost like having an Alfa Romeo Spider with a 12-cylinder engine ;)

We should (myself included) try to keep the following related concepts independent:

(1) small wheel bikes are at a disadvantage racing
(2) folding bikes are at a disadvantage racing
(3) small wheel bikes are at a disadvantage during "normal" riding
(4) folding bikes are at a disadvantage during "normal" riding

Furthermore, the original idea only refered to how the bikes perform instead of how convenient/useful they are.

Given that one could always add a folding mechnism to a regular bike (when designing a bike) and high-end manufacturers omit them, they cannot be optimal for riding. Consider a folding frame that was otherwise identical to a non-folding frame, the folding mechnism would add weight and complexity making it suboptimal.

Small wheel bikes, however, could be better than big wheel bikes. See a bunch of articles that reference Moulton.

Suppose that small-wheel bikes are superior to big-wheel bikes and folding bikes are a subclass of small-wheel bikes. Then we would get the following ordering:

(small-wheel bikes) > (folding bikes) > (big-wheel bikes)

I own a Dahon Mu SL and have taken it out on a 45 mile ride with a friend on a full size road bike. I fell behind climbing hills. Half way through the trip, my friend and I switched bikes. On the full size bike, I still fell behind climbing hills, and my friend went ape on the 20" folder. He also pulled away from me on the downhills. I was doing 32-33 MPH and he must have hit 35-36. While the big bike was a bit more comfortable, the Mu SL was at least as fast. My friend raved about the Mu. The curved tubing, minimal components, and aluminum frame make for a very stiff and light road bike.

That said, the Dahon has a hinge in the middle of the frame that creaks and is a major weak point. Thus, while good on smooth roads, I'd be worried about rough roads. The only real folder (e.g., you can fold in 30s or less) that can be taken off road is the Birdy. (Correct me if I'm wrong. The owner's manual says that the frame is fine for trails and tow paths, but you have to mind the low hanging derailleur.) Given that the average street in NYC is a touch more perilous than the average packed dirt path, I considered forking out the $900 for the Birdy Red despite the Alivio groupset. (Capreo will set you back $1250.)

As dcoli points out (haven't seen you on the path or campus in a while), though, lower the tire pressure on a fat tire and you can handle just about any passable surface (paved road/packed trail) on a folder with a hinge. I'm eager to try my girlfriend's downtube on the Croton path in NYC as soon as I get the stock wheels rebuilt.

So, I have a general question for the technical types. Assuming that the hinge-less frame is the optimal design, why couldn't this bike be made into a smaller, stiffer package by shortening the main tube and raking the fork and bars forward? This would maintain the wheel base, but allow a lighter, tighter fold. It would require a bit of fork redesign, but the Birdy could use that!

Could also use a swingarm to pick up chain slack as the stays fold under the bike. This would keep the chain nice and tense without a tensioner.

Perhaps this is a post for the frame building folks.

So, I have a general question for the technical types. Assuming that the hinge-less frame is the optimal design, why couldn't this bike be made into a smaller, stiffer package by shortening the main tube and raking the fork and bars forward?

Um - check out the mezzo - www.mezzobikes.co.uk (http://www.mezzobikes.co.uk) - bike does exactly that, making for fab, stiff ride.

Woa. And with 20" wheels. Nifty. I'll never be modern.

The Mezzo has 16" wheels.

Oddly, on the derailleur model they chose not to use Capreo cassette (9-26t), and opted for a 12-27t block instead. This limits the top-end significantly, and makes little sense IMO...

Here in a nutshell, is why I only ride/buy folding bikes now:

I do not "blast" down the street anymore. I am not interested in adding to the rising body count here in Southern California. I maintain a rather predicable speed about 10-15 miles per hour, no matter what type of bike I happen to use. That is why I gave up road bikes.

The overall design seems to favoribly fit me in all the right places. I can step over the low frame with a skirt and other business attire, stretch my legs without cramping and ride upright-the right options now.

The smaller wheels seem to go better with internal hub gearing (i.e. three speeds) which is what I only need even here in a greatly rolling hilly area where I mostly ride.

The last reason is still the most important reason of all. It is better to compromise with a folding bike than to have no bike at all. The theft rate is extremely high here and I am in better position of not having being stolen with the bike with me at all times. Plus with the added thought of almost no chance of being stranded somewhere due to it being stolen-after all, the ones that were taken from me were all outdoors locked up supposely securely.

The Mezzo has 16" wheels.

Oddly, on the derailleur model they chose not to use Capreo cassette (9-26t), and opted for a 12-27t block instead. This limits the top-end significantly, and makes little sense IMO...

Yeah, I clocked that. But as a stop start commuter in London, which I guess is what the bike was designed for, it works out very well indeed. I very occasionally miss a higher gear, but not that often. According to the Folding Society road test, ATB chose the 12-27 cassette because the Capreo cassette would have required a Capreo hub, limiting the scope for picking alternative clusters. I might pick up on the reviews suggestion of an 11-32 cassette at some point I guess. I own a DT IXFS and a Mezzo, and the Mezzo is by far the one I spend most of time time riding - even at weekends.

According to the Folding Society road test, ATB chose the 12-27 cassette because the Capreo cassette would have required a Capreo hub, limiting the scope for picking alternative clusters.

You can alter the Capreo cassette if you want more bottom end: 9 - 32t provides a good all-round range. The gaps between the gears are bigger, but this is not a major issue for most people...

Probably an older article featuring an early Dahon:

http://www.johnforester.com/Articles/BicycleEng/dahon.htm

Returning to the article that started the thread, I've seen it linked on other bicycle discussion groups before. Forester was evaluating an early model of Dahon, for the plaintiff in a lawsuit against the company. His comments do have some general instructional value, but I don't think they were intended to apply to folding bikes in general. The case was summarized elsewhere on his web page, here http://www.johnforester.com/Consult/cases2.htm, the second case down.

I think the article does apply to all folding bikes namely:

1) It is not well understood what makes a bicycle stable.
2) Designing a bike for maximum stability is a difficult thing that involves allot of trial and error.
3) Adding a hinge to the frame and the condition that the wheels come together perfectly when folded makes it even harder. My guess is that the exact fork design of all folding bikes is at least in part influenced by folding not performance.

I suspect that the latest CAD software makes things easier.

this is way before my time . therefore i have only third hand info about this...
what I can say is this.....

DONT BUY ANY CHEVROLET products as Ralph Nader has prooven that the Corsair is dangerous at all speeds... ( for the younger ..lol folks here ) The Corsair was a chevy with rear engine an attempt to copy a Karman Ghia with a Porsche, just way cheaper.. Ralp Nader did some ridicoulous "tests"with it and got notority about going against a big company and won.....

That is not the case with the Dahon story. First of all we are talking about one of the earliest Dahons from 20 plus years ago ..... take a beloved Raleigh twenty or any other small wheel bike and one could come to the same results..... especially if you get paid to proove a design flaw. Unfortunately Mr Forrester doesnt disclose this, nor the model, nor the date and and and..... He allegidly got so much disgruntled about the fact that his client lost the case, that he made his "findings"available to everyone. Now he is laughing about the wonders of the internet that his article comes up in google way up in the ranking... This happens cause a lot of people actually providing links to his stuff and a lot of people reading it.. therefore the google search engine gets renewed all the time.

Yes I am a Dahon dealer ....
still this is ridicoulous at best .....

Thor

More emphatically, if you can't handle a bike because of wheel size, geometry, speed, balance, or perceived and/or verifiable folding issues, etc., maybe you should ride a different bike. Trikes look pretty cool.

DONT BUY ANY CHEVROLET products as Ralph Nader has prooven that the Corsair is dangerous at all speeds... ( for the younger ..lol folks here ) The Corsair was a chevy with rear engine an attempt to copy a Karman Ghia with a Porsche, just way cheaper.. Ralp Nader did some ridicoulous "tests"with it and got notority about going against a big company and won.....



Sorry, I have to correct you before someone else does...it's "Corvair". "Corsair" is an airplane.

:D

That being said...

The Forester article did concern me when I first started looking for a folder, and Dahon was at the top of my list...until I noticed the date.

For the record, I've ridden my Dahon Speed 7 all over the place with no problems. For urban commuting it's tough to beat. Ride on road...catch the train...ride some more...fold it and stow it. Love it!

Reading the article peaked my interest in "trail". It is true that increasing trail increases stability. It seems to me that it is easier to get a larger trail on larger wheel bikes. People have commented on how stable the Xootr Swift is, yet eyeballing the trail measurement based on pictures, I wouldn't think that it would be large compared to a racing bike with 700c wheels. Does anyone know if it is reasonable to compare, as a measure of stability, the trail of a 700c wheeled bike vs the trail of a 20 inch wheeled bike?

this is way before my time . therefore i have only third hand info about this...
what I can say is this.....
. . .That is not the case with the Dahon story. First of all we are talking about one of the earliest Dahons from 20 plus years ago . . . He allegidly got so much disgruntled about the fact that his client lost the case, that he made his "findings"available to everyone. . . .
Yes I am a Dahon dealer ....
still this is ridicoulous at best .....
Thor

I'd agree that Forester's article shouldn't be taken as having anything to do with present Dahon models. I might be a little worried if I bought one of those, ahem, "classic" Dahons on Ebay, but that doesn't apply to the more recent ones. I like mine.

But did his client really lose the case? Forester claims that Dahon settled on the day the trial was to start. That doesn't mean that they were in the wrong, of course. They may just have paid out some money to the plaintiff to avoid the uncertainties and expense of a trial. Does anyone know the terms of the settlement?

Speaking of trail, the stock Raleigh Twenty is not ridable no-hands due to inadequate trail and the nylon bush used at the top of the head tube.

I can ride my R20 no-hands. I cold-set the fork, reducing the blade curvature, thereby increasing trail. I cleaned and silicone-greased the nylon bush, thereby reducing the friction. Look mom, no hands!

Oddly, on the derailleur model they chose not to use Capreo cassette (9-26t), and opted for a 12-27t block instead. This limits the top-end significantly, and makes little sense IMO...

I now have the dubious honor of owning two different kinds of 20" folder. The first, a Giant 1/2way has seven speeds from around 33" to 75". Too narrow a range IMO. My Downtube has a much wider range 25" to well in the 90"'s. The derailleur cage on the Downtube practically drags on the ground!! Especially on the low end, adding even one tooth results in the need for a significant amount of cage length to wrap the additional chain. That is the reason why on the 16" Mezzo the gearing range has to be curtailed. The designer has the choice of biasing the 40" or so of total range towards the top end or the low end i.e. 23" - 63" vs 53" - 93" either of those two ranges will need the same length of derailleur cage but the second range would only be rideable by extremely fit cyclists and the first would frustrate moderately fit (average) riders. The end result (33" -73" is the compromise). On full size 26" and 700C wheels the length of the rear derailleur is never even a consideration but on a 20" wheel it starts to become an issue and on 16" wheels is 'is' an issue. And while I am in a pedantic frame of mind: The Chevrolet model that Nader took so much exception to was the Corvair and IMO although Chevy may have started out with a flagrant copy of VW's Type I motor they solved all the problems experienced by the VW motor and improved on it in several key areas.

H

My Downtube has a much wider range 25" to well in the 90"'s. The derailleur cage on the Downtube practically drags on the ground!! Especially on the low end, adding even one tooth results in the need for a significant amount of cage length to wrap the additional chain. That is the reason why on the 16" Mezzo the gearing range has to be curtailed. The designer has the choice of biasing the 40" or so of total range towards the top end or the low end i.e. 23" - 63" vs 53" - 93" either of those two ranges will need the same length of derailleur cage but the second range would only be rideable by extremely fit cyclists and the first would frustrate moderately fit (average) riders. The end result (33" -73" is the compromise). On full size 26" and 700C wheels the length of the rear derailleur is never even a consideration but on a 20" wheel it starts to become an issue and on 16" wheels is 'is' an issue.


Sorry for going OT, but the above only reinforces my case for a Capreo cassette on the Mezzo!

lol
corvair it is of course and not corsair .... double dummy as I am in the progress of buying a corsair ( sailboat that is ) I must have thought boats when I wrote that.

Indeed the late model corvairs especially the judd version ( made in St Louis with a big turbocharged engine and vastly improoved brakes and running gear ) is a real cool car. Even the regular ones are not bad at all .... Nader got one of the very early ones where the suspension and brakes were designed for a front motor rear driven car versus the rear engine corvair... they really handled pretty bad. ( by that matter all cars from that era handled pretty bad compared to todays )

But the comparison is still pretty right on... early Dahons are not even close to todays versions

Thor
Corsair owner ( sailboat that is , i hate to burn gas on the weekends )