Ajustable travel forks, gimmick or genuinely useful?

[Techno Destructo]

mine are air and oil. so when i want soft i just take a bit of air out. when i want stiffer just add some air. simple

Whilst preload adjustment is all fine and dandy, I'm really after the opinions of people that have used and abused on-the-fly adjustable travel systems.

Well, Rik, you rode with me on those city rides... I've got 04 Psylo SL's with U-Turn and lockout, and I've been using them for several months (I got the 04's through a connection...). You've seen me doing stair gaps and generally abusing those forks. As well, Squid's seen me push it a bit on those forks on the trails. But both times, the travel was maxxed out. I suppose the reason why I'm always seen with max travel is that I consider my bike (a Brodie Holeshot) to designed for air/abuse - which it is. So the application I use my bike towards kinda needs big travel.

I probably use the max travel 90% of the time, and the times I use the lower travel - I put it to it's minimum (I actually haven't ever ridden it at half the travel range - about 100mm)
Here's the reasons why I turn down the travel to a lower setting:
Less bob when pedalling - for xc and on road reasons
Lowers the front end angle of the bike, making it more nimble, twitchy, and a better xc position.
Moving the bike around in cars or shuttling or any other time I want to protect the stanchions more (I know, not your usual reason for buying adjustable travel, but it's handy in those situations)
Dirt jumping - although I'm not completely convinced of the advantage of less travel in that realm - I just go by other people's tips and recommendations.

In hindsight... would I look for adjustable travel in my next fork? Probably not. It's a nice feature, but it certainly wouldn't be a deciding factor when purchasing. I like it, but I certainly don't NEED it...

Now... the lockout... that's a different story. I would definitely get another fork with lockout - like a Fox or another RS... That comes in very handy when on the road gettting from point a to point b. Nice on long, smoother hillclimbs too.

 

[Cúl-Báire]

Pics? I wanna see pics of the 04 Psylo's, are they just the same or any different?

 

[Techno Destructo]

Same internals. Different graphics. Made in a different factory, from what I understand. If you want to see photos, in the Watering Hole, the Sydney night ride (Aug 27th?) thread has photos of a bunch of us. I'm on a white Brodie Holeshot hardtail with red forks up front. Those are the 04 Psylos. Not a very good picture of them, but then again... there ain't much different.

 

[wombat]

And Shayne... I agree with you re the spring's actual "rate". IMO the only effect "reduced travel" could have on a spring's true "rate" would be the reduction in time available for compression and therefore a very VERY minimal effect on the WAY the spring compresses. What do you reckon?

Exactly. In my (limited) understanding, you can't make the spring rate any different without changing the spring; all you can do is adjust the preload. From memory though, the Psylo springs aren't a constant pitch, I'm pretty sure there's a progressive wind in the middle somewhere. So maybe that has something to do with it.

Thought: I suppose you could change the spring rate without changing the whole spring if you had a dual pitch wind (try and stay with me here), and you wound the bottom stop from the middle of the spring, down to the bottom to the spring, so you effectively have a stiffer spring. Does anybody know exactly how the u turn sytem works?
Hmmm, I'll see if I can find my old one, I think it's still in the cupboard.

 

[S.]

I get what you're saying wombat, but that would be pretty hard to do because the spring stop would have to be on a slant all the time.

The way I thought of doing it was to have whatever shaft the U-turn knob is connected to, use 2 separately threaded sections. The top threaded section would wind the top of the fork down, whereas the bottom one would wind down at maybe half the distance:turns ratio of the top thread. Thus, the spring gets compressed by half the distance it would if you were simply to compress the fork that far by pushing on it.

The flaw with my theory is negative springs...

 

[wombat]

Hmmm, the spring wouldn't need to be on a slant, you simply have the rails on the bottom stop cut on a slant to match the pitch of the spring.

The way I understand your idea though is that you're simply compressing the springs part way as you reduce the travel. If that is the case then you're not actually increasing the spring rate, unless it's a progressive spring, in which case you're kinda upping the compression damping, not really the spring rate...i think..... :?

 

[S.]

Well, you assumed it was a progressive rate spring, and so did I. Unless the compression damping is completely linear, it's also gonna be affected by the u-turn (unless you do it so that it doesn't lower the fork at all).

I didn't say the spring would be on a slant, I said the spring STOP. But even still, I don't know if that'd be good for the fork.

 

[wombat]

I think we're talking at cross purposes here. When I said compression damping, I didn't mean the oil/air damping circuit as such, I meant the inherent ramp up that is present in a progressive wind spring.

All that you do by compressing the spring part way (with a progressive one) is to move part way through the softer travel, and get closer to the stiffer part of the wind. Effectively the spring will ramp up sooner, as if you had upped the damping.