Mountain bike forks

Shibooty

Hi I'm new to mountain biking just got a cannondale sl5 and it as been upgraded with rockshox tora 318 u-turn fork but the guy said he haven't put the right amount of oil in the forks so lost about 30 to 40mm it's that right or are the forks broke thanks

mattv

If it's not got enough oil in a fork, it generally just affects the lockout and damping. Is it that it won't compress to full travel? All the way down? Thats a common failure on rockshox of that era, a seal goes inside the fork. Part is like £13. And a lowers service as well, expect a local shop to charge around £50-55 to fix and lowers service.

cooldad

Or maybe they're U turned down.

bartimaeus

But you could try replacing the oil in the damper - measuring the right amount. It does make a big difference - the tolerance is pretty tight on the volume needed (to a ML or two).

Shibooty

Thanks for replys sounds like it the oil as when I'm on the bike the forks drop 30mm straight away thanks will try new oil in damper and bottom legs

The Rookie

That's not a lack of oil.....when you are on the bike in the normal riding position (not seated) the forks should drop by about 25% of the travel! you adjust the spring not the damper (where the oil goes) to adjust this sag.

Shibooty

That's all adjust right m8 got to be oil

97th choice

Sorry, can you clarify that? when the bike is unweighted the forks are fully extended, and when you get on they sag by 30 - 40mm, right?

rockmonkeysc

Thats not oil. Either the spring is too soft or something internal is broken or the u turn is wound down.
The damper just controls how fast the fork compresses, not how much it sags. Thats controlled by the spring.

CitizenLee

If they are adjusted correctly then they should drop 25-30% of their travel when you get on the bike. It's called sag, and you need it for the forks to function correctly on the trail. I'd be more worried if they didn't drop when you got on it.

Shibooty

Yer they do sag but to much it's like half of the 130mm travel just had all new seals but not enough oil I think

The Rookie

NO no no.....oil goes in the damper, it is not part of the spring that holds your weight up, the spring (air or coil) is too soft, it has NOTHING to do with oil.

Shibooty

It do have something to do with oil coz I've just came back from my local bike shop he topped the oils up in the damper and bottom legs and wot do u no back too normal now it only sags abit not half way thanks for all your replys great help lmao

cooldad

Unless they were air and he pumped them up.
Kaching.

The Rookie

Suggest you learn the difference between a spring and a damper.....oil did not make any difference at all.....

I rebuild car suspensions as well as bike forks, all they did was add air or change the preload to fix your sag, they may have added oil and charged you for that as well....'lmao'

Shibooty

No I think u need to learn m8 preload adjuster was tuned right out and the same when I had them back so think u need to learn more don't you lmfao and there is no air on this ones m8

cooldad

Please stop with the text speak. Apart from being against the rules, it's annoying and makes you sound like an idiot.

But as you are an expert, why ask in the first place?

The Rookie

Preload needs to be wound in to reduce sag......

But I'm sure you can explain in simple terms how damper oil changes the sag.........

rockmonkeysc

Oil is used for damping. Damping controls the SPEED that the fork moves in either direction it does not stiffen or soften the fork.
The is some oil in the lowers but that is purely for lubrication.
Have a read about how suspension works.

bartimaeus

A lack of oil in the damper can limit the amount of available travel - though the manual actually suggests "Oil volume is critical. Too much oil reduces
available travel, too little oil decreases damping performance". Either way, it doesn't sound like that is the problem here.