da_shimano_05

im going to buy a fork
which is better Air fork or spring fork?

Chone

Your topic title should read air or coil.

Generally speaking, air means lighter and progressive and coil means heavier (but more resistant) and linear. It was something like that I can tell you however that air sprung forks are usually the fork of choice for XCers and racers and coil sprung forks are the choice of freeriders, downhillers, etc.

*Waits for someone else to post a more informative post that is less of a mess lol*

diff_lock2

Well... my so called "XC bike" came with air...

da_shimano_05

so i guess air fork is better for my all mountain biking!
i don't do jumps or drops or downhills.

mx_599

pretty good explanation. i would call them springs though....that is perfectly okay.

springs allow for finer tuning in a narrower range of dampening (gastro?). air tuning is broad and not as tuneable. although still very good

to answer your question:

neither is better than the other. don't feel like air is lesser quality or vice versa. figure out what you think you will use yours the most for...

mx_599

i just read what i wrote above and thought maybe it wouldn't make sense to people...or maybe even to myself.

in otherwords, it is much more difficult to get an air fork dialed in to smooth out small chatter bumps and then have it work well on a big g-out, drop, jump, whatever...

however, with the proper spring rate, sag, and comp/reb adj, it is much easier to have a fork feel plush on small stutter/ choppy bumps and then have it take a big hit as well. only the final 5-20% of travel being very progressive due to a sharp rise in air pressure inside.

but with an air fork, it is going to get progressively stiffer from the get go as Chone mentioned. therefore, if you have an air fork dialed for huge stuff, than it probably won't have as great a potential for plushness on small bumps

hope that helps...anyone disagree?

digger

****lurks with interest****

mcoine

maybe I am misunderstanding, but lets not confuse dampening with spring rate. Also, I would not call an air spring "not as tunable" because you can set an air spring at any rate, just by adjusting pressure. In a coil spring, you are stuck with the rate of the spring, and if you want to change the rate, you have to get a new spring.

Flak

Then what is dampening?

I stiffen my fork up with the turn of a knob on the fly.

Or are you saying that the travel becomes stiffer, but the spring will expand and contract at the same rate no matter the stiffness setting?

mcoine

With no dampening your bike would bounce like a pogo stick. Dampening applies resistance to the spring, in both compression and rebound.

mx_599

not confusing the two. what i am trying to say is this:

dampening occurs all the time...through the full amount of travel. if you were to take say an inch of that that travel somewhere in say the middle of the stroke (narrow range), it is my opinion that a spring will allow for finer tuning than air. air is at the mercy of increasing pressure, springs not necessarily...more so at the very end of stroke.

in my opinion, you cannot set an air fork at any rate due to the nature of a compressing gas.

this is precisely why i think springs offer more tuneability. you do not have increasingly compressive gas messing with your other adjustments.

mx_599

dampening is controlling the oil flow through orifices and shim valve stacks affecting shaft/stanchion speeds.

mcoine

ok, but how many forks have linear rate springs, as opposed to dual rate springs.. I am actually asking, because I don't know.

mx_599

most fork springs and shock springs i have dealt with are linear. come to think of it, i mostly just notice progressive winds in automobile stuff. i am sure they are found in bikes too. however, not really in motocross. often times the springs will have a taper to them, but that is not progression. i have seen progressive winds for other types of motorcycling....but again, not for motocross.

...and maybe i am wrong on everything because i am basing a lot of it on motocross experience. however, i think they are very similar.

again, everything i have typed above is my take on things from working with suspension over the years. i am not saying i am right. my opinion

mcoine

Oh, I agree, I know you have a background in motorcycles, where they figured out all this years ago. I just recently found a pair of Progressive dual rate fork springs for my '75 honda cb400f (a street bike, i know), but I figured most of the motorcycle and mtn bike world was using dual rate springs.. I guess not.

mx_599

and then another question is how does the progressivity of compressed air compare to a progressive spring?? to be honest, i have not worked with many mtb systems to tell you if they are linear or progressive. someone like Maelstrom or Gastro or others who have more exposure to the mtb scene could probably answer that better. i am way out in the boonies. the only fully suspended bikes i run into are wally world ones

mx_599

exactly...most of the progressive springs i have run into are used on a system that has no rising rate linkage etc. like on motocross bikes from the 70's where they have dual shocks between the seat sub frame and swing arm. there is no linkage to create a changing curve, so i have seen plenty of progressive winds for them in like white brothers catalog and stuff. as far as i know, you wouldn't want to use them in a linkage based design.

i should probably shut-up now and go find a motocross forum or something. i know i cannot apply everything to bicycles.

now i am curious. all you DH'ers and FR'ers out there...what is commonly used for springs? progressive or linear??

thanks!

C-daleRAG

Bahhh! I'll talk MX with ya anytime.


As far as air or spring, I choose spring with a stable platform air valve. Keeps my ride height up where I like it yet stays plush over choppy roots and rocks and will also soak up a big G out. I use to have a full air fork and I liked it over choppy stuff but G-outs was not so great. If I pumped it up to take the G-out's better, then it suffered on plushness. Personally I thought the tunability of the air was a little harder to pinpoint.

Svr

Chone is right. Springs come in many forms. Compressed air and a coil of steel wire are both springs.


Which one is better? Niether. A simple air spring might be progressive, unless it's countered by something. That 'something' is known as a negative spring, and quite a few of the higher end air sprung forks have adjustable negative springs to counter the progressiveness of a simple air chamber.

Steel wire coil springs weigh more, but can be wound to mimic almost any rate desired.

Both types work well, but it's the entire package that counts. Don't make a decision based only on spring type.

Help Im A Noob

anyone have a simple answer so i dont have to read all this?
air............... both are just as good ................coil

mx_599

crap...you beat me to it. i wasn't able to post until tonight. i didn't think anyone would pick up on that before i got here. oh well. i wanted to correct myself with the negative air chamber. i was only considering positive pressure. i believe some forks only have positive pressure anyhow.

the question still remains how well negative pressure will compensate for built up positive pressure. this also depends on how much neg pressure a rider uses. still a nebulous situation

also, i do not agree that compressed air is a spring. it acts as a spring...but it is not a spring

mx_599

exactly.

if weight weren't an issue, i would probably tend to choose springs rather than air

ed 

C'mon...weight's not an issue when it comes to springs.
There's just nothing better than a nicel coil fork. Who cares 'bout 3/4 pound, right?!

I have just graduated from a 24lb hardtail to a 32lb dually. I love the pain!!!

Chone

Hmm there are some light coil forks, for example a Fox Vanilla RLC is 3.98 pounds, the same weight as some air forks like the Marzocchi MX Comp/Pro.

Yeah, I want a Vanilla so much...

mx_599

don't be lazy


both good, depends on use...read for details