DyingAndDying

Front suspensions are cheap so it's easier to just to be a new one, but I just want to know how you'd make the spring longer so it absorbs the impact of say riding up on a curb

rsbob 

Spring? Most are oil based shocks which can be adjusted by turning a dial on the top of the shock. Since you cant post a picture yet, please describe in detail what you have. The only thing I can imagine are the the old StringRay bikes with a single spring on the front fork.

Rolla

Coil spring/oil forks are a thing (like Rock Shox Silver 30), but they're heavy and they don’t offer much adjustment. You can’t increase the spring length, but you can buy springs of different durometers. You’re still talking lowest-common-denominator suspension, though; lighten the spring too much and you bottom out on small bumps. If you’re serious about plush travel, upgrade to an air shock, or learn to lift up the front wheel when you go over a curb. Or just htfu.

veganbikes

Cheap? My Fox 34 retails for almost 1k. My Rockshox SID is probably close to the same at retail (though that was on a big closeout and a little older and honestly I wish I had more travel). Not complaining I do love the forks but they are not cheap and at least with the Fox fork I got what I wanted.

The cheap stuff really isn't all that great and is fine for an occasional rider who doesn't really care. There are no curbs in the forest or the mountains so not sure where you are that they would exist there but if you are in an urban environment you probably don't need to go up and down curbs since you wouldn't want to ride on a sidewalk except in an emergency. However if you are looking for more comfort and adjustability you want a decent air fork, stick with known quantities like Fox, RockShox, Manitou, Marzocchi, SR Suntour (but be aware they do a lot of low end stuff as well that is cheap coil) make sure of course that the fork will fit your bike in all ways it would need to but best bet is to ask your local bike shop and they can help out or be honest and say "hey the bike isn't worth it save up for something that makes more sense".

cxwrench

So you don't really know how suspension works, right? Something has to be the spring and it sure as hell isn't oil. It's either a coil spring or air. Coil forks and shocks have oil in them, they are dampers after all, so do air forks and shocks. It's not 'coil' vs 'oil', it's 'coil' vs 'air'.

50PlusCycling

Depending on the fork you either back off the spring preload or decrease the air pressure, some forks have a damping adjustment lever or knob which allows a fork to react more quickly or more slowly over bumps. You can find out all you need to know by reading the instructions which come with your fork. Online manuals are available if you don’t have your fork’s original instructions.

big john

When he said suspensions are cheap I knew he wasn't talking about any suspension I know about.

rsbob 

Hilarious response. Non doubt true but the way you said it made me laugh.

Rolla

Forks with coil springs are cheap. A RS Silver 30 is less than $200. You definitely don’t get what you don’t pay for, though.

indyfabz

A cold shower?

Kapusta

On the one hand many coil forks are very cheap.

OTOH, some people spend $500 to convert their air shock to coil.

Kapusta

I prefer water-based suspension.

big john

I had a couple elastomer forks bitd. They were cheap compared to what we have now. I bought springs and a damper kit for one of the old Manitou forks and it was actually pretty good after that. I have a 160mm Fox 36 on my bike now but it's the cheapest model. It's bigger and better than my first motorcycle fork.

cxwrench

Glad it did the job!

badger1

Just take the spring out and stretch it. One way to do this: soak it in water for about 6 hours, and then hang to dry with a weight on the end. 5 lbs. or so is typically enough.

Re-install, and you should be good to go over any curb.