Mountain Bike Reviews Forum banner

Setting Sag on a Fork

1390 Views 7 Replies 7 Participants Last post by  The Hired Wrench
I am looking for some help on setting sag on a fork. I have the Rockshox Dart 3 and read the manual on using a zip tie and determining the amount of sag. It sounds easy enough. The Rockshox manual says recommended is 15mm - 25mm.

Do I set it to the low end at 15mm or at 25mm or somewhere in between? How does it affect the ride based on easy or rougher trails?

Thanks.
1 - 8 of 8 Posts
idm im not sure but i thought you set your sag according to your weight
for example:

XC racers set their sag at the lower end.
Downhillers set their sag at the higher end.

most people talk about sag in terms of percentages. so like the general starting point is 20% of your total travel. your fork has 100mm travel so 20% of that is 20mm.

see http://www.bicycling.com/article/0,6610,s1-5-31-1065-1,00.html for sag setting procedure.
The effect on your ride can be figured out fairly intuitively. When you set more sag you have more "negative" travel-- meaning if your front wheel goes into a hole, it can drop the wheel further before it starts dropping the bike into the hole. You lose a bit more positive travel (on a 100mm fork, if you're sagged to 20mm, you can only compress 80mm more), but -- and correct me if I'm wrong here -- you'll have an overall plusher feel to your ride.

Set it somewhere in between and tweak it up and down as you see fit!
A little more application-specific advice...

Preload makes the fork feel firmer at the top of the travel, when you want it to be soft. If you're over 180lbs, put in the 'firm' spring and leave the preload dialed all the way soft, otherwise, just leave it soft. If you're 220lbs+ get a new fork, the required preload is going to feel terrible, and you'd really benefit from a stiffer fork that can run larger brake rotors. Preload just makes the fork feel harsh.


On a more sophisticated fork, a little bit of preload, combined with rebound and compression adjustments, plus the right spring, can be a benefit. It's included on the dart because it's cheap and they can advertise another 'feature.'
scottzg said:
On a more sophisticated fork, a little bit of preload, combined with rebound and compression adjustments, plus the right spring, can be a benefit. It's included on the dart because it's cheap and they can advertise another 'feature.'
Are you saying that the preload adjustment is basically useless on the dart?
Robmc7759 said:
Are you saying that the preload adjustment is basically useless on the dart?
yes. Not completely useless, but basically useless. It's no mistake that RS doesn't bother with preload adjustment on their higher end coil forks. I also think that the rebound adjustment is too coarse to be useful.

But hey, it's an adjsutment, so you might as well play with it.

I ran some thinner oil in the damper of my dad's dart and used the preload and a partial turn of the compression knob to keep the fork from diving under braking. It improved it a fair bit. If you're to the point that you're fussing with it like that, though, you'd be better served with a fork with a nicer damper.
ACSN said:
I am looking for some help on setting sag on a fork. I have the Rockshox Dart 3 and read the manual on using a zip tie and determining the amount of sag. It sounds easy enough. The Rockshox manual says recommended is 15mm - 25mm.

Do I set it to the low end at 15mm or at 25mm or somewhere in between? How does it affect the ride based on easy or rougher trails?

Thanks.
i like to be a little conservative when it comes to sag settings, as we are not in a truly high-speed application, a 25mm sag in an 80mm or even a 100mm fork will do no more than eat up usable positive travel. use 25mm only if you feel you're not using the fork's full travel. say your ziptie is 10mm below the full travel mark after a lap at your local favorite.

as most have said, a good damper tuning will do more than dialing in huge amount of sag. what good is your fork without controlled operation? not very. so lets talk about valving and oil weight and worry less about sag (basically a negative travel setting that will keep the front wheel on the ground over 'chattery' or 'dippy' sections as momentum wants to propel forward and the damper has NO time to react)

beginning with

how much do you weigh?
whats your riding style?
where is your home-base and what type of terrain is it?
when you climb a hill, do you feel inefficeint or bogged down?

these questions will determine, in order;

spring rate
oil weight and valve size (a dart three will leave ONLY oil weight as an option)
negative travel
preload
See less See more
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top