20 inch wheel folder stability

[RogerK]

I have a dahon speed 7 with 20 inch x 1.5 tyres. I find going down hill at speed quite hair raising compared to my normal size bike.
Would putting fatter tyres on, 1.75 or even 2 inch improve the stability. Has anyone done this?

[horizon]

I have the same and am very happy with the stability of it. But I wouldn't go down hills at speed on it. Wider tyres may improve matters but the smaller wheels will still (AIUI) suffer worse in potholes and on rough ground.

Others may have further info on this.

[moultoneer]

All smaller wheel bikes are more responsive, or twitchy! You get used to it. An advantage is that you can usually "catch" the bike if the front wheel slips on a wet or icy surface, because you can turn it very quickly. Putting fatter tyres on won't change it noticeably.

[horizon]

All smaller wheel bikes are more responsive, or twitchy! You get used to it.

Yes, I agree. Is that what the OP is experiencing perhaps? I found stability to be (surprisingly) excellent so going fast shouldn't be any different after allowing for the small wheels. I just wouldn't go fast downhill.

[niggle]

My Pacific Reach is, IMO, good at fast descents, particularly twisty ones. It has 451mm rims, 28mm tyres and full suspension- I set my personal downhill speed record of 56mph on it It has good brakes and responsive steering- which if you have just stepped off a 700c bike might feel twitchy until you get used to it: it is fast steering and goes exactly where you point it. Unstable means something else to me, e.g. speed wobbles. When I fitted drops for a bit that seemed to make it a bit slower steering.

[drossall]

I've got a Dahon Vitesse 7, so pretty much the same as RogerK's. I agree that it does not feel as stable as a "proper" bike.

That said, I think confidence plays a significant part, and you tend to be more confident on a familiar bike. I'm happier on it now than I was at first, and in most riding it's fine.

[squeaker]

Would putting fatter tyres on, 1.75 or even 2 inch improve the stability. Has anyone done this?

Now have 50mm Big Apples (was 40mm Marathons) on my Dahon Vitesse, primarily for comfort, but does slow the steering down slightly. The extra pneumatic 'suspension' also helps, of course

[Freddie]

A number of these folders are poorly designed with respect to front geometry. Yes, a small wheel won't hold a line as readily as a larger one and will be more responsive to input, but it should not be too difficult to ride, if the geometry is optimised. There is an interesting read about modifying the trail of a folder and the improvements it made to handling here. Note the bicycle the author of the linked article had difficulties handling was also a Dahon.

These designs are really quite new and there is little in the way of knowledge of best practice when designing a folder, this assumes manufacturers are much interested beyond shipping as many as possible with the consideration that most won't be ridden further than 3 miles at a time. Look at the travesty that is the Sinclair A-bike, any child above the age of 8 could tell you that design would not work as a functioning bicycle on typical road conditions, but it folds to a small size, so what does usability matter?

[robgul]

If the 20" wheels worry you, try an even smaller wheeled Brompton ... the work of Satan - worryingly unstable IME.

As suggested, folders are not designed for fast descents, that said I'm reasonably comfortable with letting my 20" Dahon on skinny Panaracers go pretty quickly downhill.

Rob

[Freddie]

I'm sure smaller wheels will hold a line worse than larger ones (they are inherently more unstable), but how much of the handling problems with folders are the fault of small wheels and how much is the fault of poor front end geometry and too short "top tubes". If you read the link I gave above, it seems the case that these bikes could be made to handle somewhat normally, perhaps at a small cost to the size of fold.

I'd suggest most of these manufacturers are more concerned with flashy features than making a well behaved bike, which is something I sincerely doubt they know how to do in the first place, as they are probably just copying and perhaps slightly modifying geometry and designs from other manufacturers; they seem to have little concept of how to alter their designs to make a bicycle that has reasonable handling (note the previously linked article was written in 1989!) and think the poor (unsafe?) handling is just something the user should have to overcome.

[robgul]

I'm sure smaller wheels will hold a line worse than larger ones (they are inherently more unstable), but how much of the handling problems with folders are the fault of small wheels and how much is the fault of poor front end geometry and too short "top tubes". If you read the link I gave above, it seems the case that these bikes could be made to handle somewhat normally, perhaps at a small cost to the size of fold.

I'd suggest most of these manufacturers are more concerned with flashy features than making a well behaved bike, which is something I sincerely doubt they know how to do in the first place, as they are probably just copying and perhaps slightly modifying geometry and designs from other manufacturers; they seem to have little concept of how to alter their designs to make a bicycle that has reasonable handling (note the previously linked article was written in 1989!) and think the poor (unsafe?) handling is just something the user should have to overcome.

Yebbut - what's the "normal expectation" of a folder for MOST users (and therefore the manufacturer) - relatively short commute rides at low-ish speed and a good fold? - so there's the compromise.

Rob

[RogerK]

Thanks for all the replies and the interesting article.
I may try some big apples as this may become my only bike for a while due to moving home and storage problems.
As for doing 50 plus mph, I don't think I could afford the cost in extra underpants!!!!!

Thanks
Roger

[Freddie]

Yebbut - what's the "normal expectation" of a folder for MOST users (and therefore the manufacturer) - relatively short commute rides at low-ish speed and a good fold? - so there's the compromise.

Rob

My normal expectation of a bicycle is that it is safe to ride, these folders invariably are not. They are compromised in ways they need not be, because the people building them know not and likely care not about geometry and have put no effort into trying to make their creations handle acceptably. What good is a small fold if you end up under a bus, because you cannot look over you shoulder without the bicycle deviating from its line unpredictably?

I know it is hard for people to believe, but these bikes need not ride as dangerously unstably as they do.

[drossall]

Oh I think my Dahon is a pretty good balance between portability and rideability. I don't think it's poorly designed at all. It just has to compromise, by the nature of its purpose. In every direction, the pressure is to keep it short so that the folded package will be small. Ideal geometry may not be compatible with that.

I've ridden it nearly 40 miles at a time with no problem. Given a choice, I'd ride a "proper" bike, but, if I'm going by train, then getting on the Dahon at the other end can still put a smile on my face.

[Brucey]

I will own up and say that I don't mind low trail that much in a large-wheeled bike. But I will also say that with high trail, the same bike will often be a fair bit more stable (in the absence of a front load).

I find that most bikes with small wheels feel less stable than larger wheeled bikes. One yardstick for this is whether you can ride no hands or not. I can't claim to have tried every small-wheeled bike but so far my personal score is a big fat 'ZERO' when it comes to stable riding no-hands with small wheels.

On the other hand that people can ride large wheeled machines with a much higher than normal trail quite happily seems evident from the number that I see being ridden with bent forks or forks facing the wrong way.

Fool that I am, I may shortly be getting a 20" wheeled moulton. Will it be OK no-hands...? Only time will tell....

cheers