Or is it a gimmick? I agree that full suspension looks great for like downhill mtn biking, but otherwise, it seems to me like it adds weight and it soaks up some of your pedal energy.

It depends on what you use your bike for, where I ride the roads are far from smooth, and smaller wheels suffer more from speed bumps and potholes, I have dual suspension (more like a shock absorbent) that is designed to minimize power loss but still making the ride more confortable, I have tried the same bike but without the front suspension, and the ride is not as good, and my hands feel it afterwards

I'd use it for commuting around a city, with a backpack strapped to the rear pannier.

If the roads are poorly surfaced and bumpy, you will appreciate the suspension. If the roads you predominantly ride on are smooth, then suspension is not really necessary. You can fine adjust the degree of comfort you desire by tire selection.

For road riding I don't find anything more than 40mm tires run at moderate pressure is needed to be comfortable.

I shot this video on the roughest "road" [actually a long wooden bridge] that I ride regularly. I'm on 16" wheels with 40mm tires [that were harder than they need to be] - no other suspension. I actually faster on that bridge than lots of other big wheeled bikes because my tires do a better job of soaking up the bumps than their bigger, but thinner/harder tires do.

I'm using a thudbuster on a Dahon Vitesse with a 2.15" Big Apple Liteskin on the front wheel run at a low pressure. . . it's not a bad ride but I'd still rather have a Jetstream if I had the cash. The roads in east London are pretty terrible. I've been considering trying to improvise a suspension stem but I can't find the right seat post to use as a stem.
Having said that the Jetstream is a little heavier than my bike and doesn't have an IG hub, which I like a lot. And a downtube FS would be too heavy. . . so my bike is a reasonable compromise. . . and a suspension stem might be the best overall compromise as it'll not add much extra weight.

Here is me going through some bumps at speed:

Considering the fact that every bike I've even seen is equipped with full pneumatic tire suspension, it's not a question of if but rather which type(s) of suspension one should use and whether the type(s) chosen is being used to its potential.

I hadn't realized how nice iF Reach bikes are. . . where did you get yours from Folding-Bikes?

Test rode a few folders with suspension systems besides the tires (Birdy, Moulton, AirGlide) and didn't like the way they handled so I stuck with the Bike Friday Pocket Rocket which feels more like my regular road bikes. But I do use slightly wider tires on it - 1 1/8" or 1 3/8" vs. 1" on my 700c road bike.

There is poor and good quality suspension, and big travel and small travel suspension. First, let's eliminate poor quality - that is a gimmick. That leaves small vs large travel. For road riding, large travel has to be argued as being not necessary.

Chucky is absolutely correct that the very first line of defense against road bumps lies in tyres. Modern hype makes many riders over-inflate tyres leading to unnecessary harsh riding. Every tire has its optimum pressure setting, that should be used. Fat tyres due to generally weaker casings, employ lower pressure, giving a plusher ride. Narrow tyres have stronger casings because they need higher pressure to prevent pinch flats. This usually also leads to lower rolling resistance as there is less flexing in the casing. A tyre that is pumped even harder actually feels faster but careful testing has shown that to be not a real effect when the tyre is already pumped to a suitable pressure.

So the tyres are small travel suspension, with no weight penalty.

It is possible to use narrow high pressure tyres and combine that with small travel suspension to remove the harshness. That can actually lead to lower rolling resistance over uneven ground, as only the wheels have to be lifted over bumps instead of rider+bike. That sort of suspension is no gimmick. It also gives greater comfort than tyres alone.

So, avoid buying a bike with poor quality suspension - it will give you info as to the rest of the bike's quality.

The best approach is to start looking at bikes with no suspension - best bang for buck as good suspension costs lots.

If the bike as-is is too harsh, the next step is to get some plush tyres, and here Big Apples is the final name. Others also work very well, such as the Scorcher already mentioned. That should fix you up.

I've never been entirely convinced by the fat tyre route. . . I mean, yes, on a rigid, small-wheeled bike I'm going to use fat tyres, but the drawback is much more rotating mass, so whilst you're not adding a huge amount of weight to the bike you're adding it where it matters most in terms of ride quality. That's why I spend the extra and get folding bead tyres. The maxxis grifter on my rear wheel has performed well and weighs under 400 grams whereas a standard Big Apple according to my scales is over 600.

BD-1's are popular in the country side of Japan because the roads are alittle more bumpy and the suspension does really help take the vibrations away.

specifically...the downtube full suspension bike.

My personal experience is with narrow HP 406 & 451 tyres and NO suspension on the bike.

I've ridden centuries, (miles and metric), multi day tour, fast group riding and general commuting....didn't think I needed suspension, didn't suffer from harshness...... and I've broken my back/spine twice.

Maybe I have my bike set up right?

It will be interesting to see how my opinion might change when I restore my F frame Moulton.

Were your accidents from road-racing Steve?

Sort of, both accidents were when I was out training by myself.

Not looking for sympathy, but.......

1: New bike, 100km into a 120km ride, slight down hill, eating banana, stretching, riding no hands.... bolt on seat clamp sheared off, landed on rear wheel, long burn mark next to my crack, landed next on the road fracturing coccyx, rolled onto hip... good bye skin. Couldn't sit for weeks. Kids were singing "Breaka breaka tailfeather"

2: Training one morning, hit from behind by car doing 80 kms, Fract t12, crushed right calf, massive DVT, severe head lacerations, left ear mutilated then rebuilt. 2 years out of work........ and so on.

Racing is safer, I hope.

Wide tires that are also fast are those with supple casings which tend to be reasonably light as well. Rotating mass is only an issue during acceleration and since a small wheel bike starts with very light wheels this isn't really an issue...so the more important issue is rolling resistance where a wide + supple tire will be faster.

Full suspension is not really necessary, but it can be very effective in the right situations...

Reach Racer, full suspension, narrow high pressure tires...

Full suspension can give small wheel bicycles a more comfortable ride.
https://www.youtube.com/watch?v=bkRJe5_oOx8
https://video.google.com/videoplay?do...70086389552343

In most cases a suspension on a bike that is going to be ridden on the road is more of a hindrance than a help as it adds weight, can affect handing, rob power, and add another degree of complication to the bicycle.

Running higher volume tyres at proper inflation pressure can do much to smooth out your ride and if the ride is better you will often go faster.

Am running some 20 by 1.35 Comets on my P20 road bike and at 100 psi they offer a very nice ride and get even better when the bike is loaded for touring.

The 20 by 1 3/8 Kendas on my R20 roll out fast, handle well, and do a nice shop of taking up road shocks.

Have noted that because I sit far more forward on the road version I am more sensitive to front tyre pressure while on the the more upright R20 the rear pressure is more critical as the front end is pretty light / unweighted when I am riding.

You can always run a slighty wider tyre in the rear to increase your comfort level as well.

On bikes with wheels smaller than 20 inches you are going to have to do more to deal with ride quality issues so having very good tyres will make a lot of differences and a well designed suspension is a beautiful thing but these are also very expensive.

I don't find it necessary, even on the pothole riddled roads I have to travel on.

My 8FS is a very comfortable ride in the city and feels like a full size bike. I just need to fix the slipping gears. Is this a common problem with suspension folders?

Probably more to do with the SA hub.
When adjusting the tuning nut, position the arrow just above the mark on the hub, that may help.

The rider adapts to the bike - whatever the bike. On harsh suspension your brain will learn to automatically detect bad surface conditions and stand off saddle with fully bent knees and bent elbows, relax the hand grip and just easily roll over. On bikes with full suspension you just pedal with more effort.
On my Brompton, I replaced the grips with Ergons and use a Brooks B17 saddle, and I replaced the stock elastomer with a stiffer version and its a faster ride and no less comfortable.