Setting Sag

Norm

Mayor McCheese
Team MTBNJ Halter's
Hi all! It's Norm the Suspension Retarded again!

Today's question is about setting sag on my Fox Float 120 RL suspension fork. It appears that I basically have 2 ways to set sag:

1. Air pressure
2. Rebound adjustment

I don't think that's supposed to be the way it works but I'm not sure. As far as I know sag is supposed to be controlled by #1 and #2 is supposed to be only the rebound. Correct?

It seems like the rebound has a pretty big impact on sag, at least when I make it soft. I was told to start with a soft rebound and go from there. But having the rebound set as soft as possible reduce the sag to...well 0%. Literally 0%. I got on the bike and the zip tie didn't move 1 millimeter.

So I backed it off maybe 5-10 clicks, pumped the shock back up from 80 to 90, then got on and just rode it around. Feels much more plush now. But I didn't bother to set the sag. I went to look online for how to set the sag, and it seems I'm only supposed to be able to control it with air pressure. So I figured I'd ask here first.

Thank you for your continued support!
 

J-Dro

Well-Known Member
Sag should only be controlled by Spring pressure (or air pressure in an air fork). Coil sprung forks usually have a preload adjustment that lets you set the sag. Either way, rebound setting should have nothing to do with the amount of sag. Rebound controls how quickly the fork returns to full extension after it is compressed.

To set the sag, put a zip tie around the fork stanchion, push it down against the fork seal, and then sit on the bike seat. Maybe pedal a few times as smooth as you can. Then, as gentle as possible, get off the bike trying not to compress the fork any further. Measure how far the zip tie has moved... Rule of thumb is that you want 25% sag to start and adjust from there.

Rebound is more of a personal preference but I like to set mine just so that I can detect minimal damping when the fork rebounds. Basically, I open it up to minimum rebound, then slowly increase it until I can just sense some damping slowing down the fork. You can always increase it more if the fork feels too bouncy on the trail.
 

Norm

Mayor McCheese
Team MTBNJ Halter's
To set the sag, put a zip tie around the fork stanchion, push it down against the fork seal, and then sit on the bike seat. Maybe pedal a few times as smooth as you can. Then, as gentle as possible, get off the bike trying not to compress the fork any further. Measure how far the zip tie has moved... Rule of thumb is that you want 25% sag to start and adjust from there.

Seriously this is what I did, pedaling and all. And the sag was still exactly 0. It was almost as if the rebound setting was "gumming up the works". When I clicked off a few times the fork was less "gummy".

Rebound is more of a personal preference but I like to set mine just so that I can detect minimal damping when the fork rebounds. Basically, I open it up to minimum rebound, then slowly increase it until I can just sense some damping slowing down the fork. You can always increase it more if the fork feels too bouncy on the trail.

You know, I may have had the rebound totally opposite of what was recommended to me recently. The damping was full-on, I think. Basically it was super soft. The thing is that just a few clicks down and the fork jerks back to position with a click - like I showed you Saturday morning before the race. Or Friday morning.
 

ytc100

New Member
Hi all! It's Norm the Suspension Retarded again!

Today's question is about setting sag on my Fox Float 120 RL suspension fork. It appears that I basically have 2 ways to set sag:

1. Air pressure
2. Rebound adjustment

I don't think that's supposed to be the way it works but I'm not sure. As far as I know sag is supposed to be controlled by #1 and #2 is supposed to be only the rebound. Correct?

It seems like the rebound has a pretty big impact on sag, at least when I make it soft. I was told to start with a soft rebound and go from there. But having the rebound set as soft as possible reduce the sag to...well 0%. Literally 0%. I got on the bike and the zip tie didn't move 1 millimeter.

So I backed it off maybe 5-10 clicks, pumped the shock back up from 80 to 90, then got on and just rode it around. Feels much more plush now. But I didn't bother to set the sag. I went to look online for how to set the sag, and it seems I'm only supposed to be able to control it with air pressure. So I figured I'd ask here first.

Thank you for your continued support!

Your spring is the only thing that should effect sag. As you stated rebound only controls how fast or slow the fork, well, rebounds after being squished. It's odd that it has an effect on your sag as the only thing supporting your weight is the spring.

The idea is to set the spring pressure until you get 20-25% travel when just sitting on the bike in riding position.

Found the attached chart for starting pressures.

Don't know if any of this helps.
 

ytc100

New Member
Seriously this is what I did, pedaling and all. And the sag was still exactly 0. It was almost as if the rebound setting was "gumming up the works". When I clicked off a few times the fork was less "gummy".



You know, I may have had the rebound totally opposite of what was recommended to me recently. The damping was full-on, I think. Basically it was super soft. The thing is that just a few clicks down and the fork jerks back to position with a click - like I showed you Saturday morning before the race. Or Friday morning.

Sounds like your rebound damper is acting strange. Could it be locking the fork out somehow - is the lockout lever moving around too?
Do you still get travel when the rebound is set "full-on"? (Which would be the most damping and slowest rebound).
 

Norm

Mayor McCheese
Team MTBNJ Halter's
Don't know if any of this helps.

Yes, it does a lot. Thanks!

Sounds like your rebound damper is acting strange. Could it be locking the fork out somehow - is the lockout lever moving around too?
Do you still get travel when the rebound is set "full-on"? (Which would be the most damping and slowest rebound).

I don't think it was locking it out. But now I know better how it's supposed to act I can play with it more. It seemed like when the rebound was full-on, it actually didn't rebound all the way. It stuck a little bit.

Anyway, if the better method for dialing it in is to make it rebound faster and go from there, I guess it's not such a big deal. I just actually read this in the online manual:

Rebound setting is a personal preference and varies depending upon spring preload, spring rate and riding style. Rebound should be as fast as possible without kicking back. If the rebound is too slow the suspension will not function properly and the wheel will not follow changing terrain.

My bold above. Clearly I had it set the complete opposite way. I misunderstood what I had been told. Today the wheel most certainly did not follow changing terrain.
 

ytc100

New Member
...It seemed like when the rebound was full-on, it actually didn't rebound all the way. It stuck a little bit.


...If the rebound is too slow the suspension will not function properly...

That's interesting.

I think by "suspension will not function properly" they are saying that the fork will "pack up" at slow rebound settings, which is normal. Too fast and it will kick back. As noted you'll have to experiment some to find a balance that works for you.

I don't think the fork should stick down though even at full slow rebound.
 

Norm

Mayor McCheese
Team MTBNJ Halter's
I don't think the fork should stick down though even at full slow rebound.

Agree.

Here's a question. Should I set sag just sitting in the saddle or in "attack" position where I'm on hands & feet and off the saddle, weight slightly forward? It seems you should set based on the latter since that's when you'd be taxing the fork the most. OTOH, you could very well end up with a pretty a soft fork that way. But there's really no "normal riding position" per se.
 

walter

Fourth Party
I was told, to either have the bike next to a wall, or have someone with you, and gently sit on the bike, where ever the o-ring/zip tie moved to, that was your starting point.
 

Shaggz

A strong 7
norm - i have a pretty decent "guide" to setting front fork suspension from last months MBA. i can drop a copy i the mail if you'd like.
 

Norm

Mayor McCheese
Team MTBNJ Halter's
Sure, that'd be cool. I still wonder about the weight distribution. When I'm just sitting on my bike most of my weight is over the rear wheel. But when I'm riding "where suspension matters" my weight is much more evenly distributed.

I played with it a little over the weekend and it's much better now, though it rebounds pretty hard and it may dive down a little in hard corners. Probably can't have everything but I can try.
 

stb222

Love Drunk
Jerk Squad
though it rebounds pretty hard and it may dive down a little in hard corners. .

brake diving and diving in corners is lack of compression damping. While you can adjust the air spring to account for this (at the cost of small bump sensitivity), newer forks should have comp or platform adjustment. Most people won't notice a difference with compression damping but if you for has some kind of platform, it helps. Diving should not have nything to do with rebound.
 

Norm

Mayor McCheese
Team MTBNJ Halter's
brake diving and diving in corners is lack of compression damping. While you can adjust the air spring to account for this (at the cost of small bump sensitivity), newer forks should have comp or platform adjustment. Most people won't notice a difference with compression damping but if you for has some kind of platform, it helps. Diving should not have nything to do with rebound.

I'm still not sure if it does or not. It rode real well on the roots at speed yesterday. And I was trying to stay in the local bmx/dirt bike trails with it, but those are some hard ass corners that you really don't see in normal XC riding. Basically those grooved out turns that the dirt bikes tear through by peeling out and turning.

Several people have told me that I ride my fork too hard since I don't get the full travel out of it. I have it now so that it was about 110mm, which is pretty close to the advertised 120mm of the fork. And the Fox forks apparently rarely get advertised travel anyway. But I'm not bottoming out.
 

Maurice

New Member
I believe it's best to set it assuming a riding position.

Also, you want your front end to dive down in corners, you'll get more grip as the head angle steepens. My fork still has a spring that is too stiff and it will wash out badly in corners. Better now with a softer spring. That and the crappy tire that was on there (rip) really sucked.

IMO you really need some extreme terrain for the fork to pack down in the slowest rebound setting; riding cross country is not that demanding on the fork. Even coming down the big descent at Round Valley at full speed my fork will not pack down at 2 clicks before slowest. On the other hand it helps a lot when climbing.

Is your fork still getting stuck? That sounds serious and should not happen. It may get stuck compressed when it's really cold, but it shouldn't affect compression in the slightest. Even if you had compression settings it wouldn't make a difference in setting sag.

Maurice
 

hardtale70

She's Gone From Suck to Blow
Shop Keep
While playing w/ the front the rear has to be near perfect as well. When my racebike was set to handle roots and rocks it had to be changed for south jersey enduros. In the pine barren events, coming out of a swamp and then having to immediatley blitz thru 20 sand whoops was common. even if the front was set perfect to sand, if your rear comp and rebound weren't just right you were over the bars by the 3rd whoop. So both need to be set together on FS..............
 

Norm

Mayor McCheese
Team MTBNJ Halter's
Maurice,

Good thoughts. I agree that riding/"attack" position seems to make more sense. On the fork diving it seems impossible to get a good amount of plushness to the fork in rocks then have it not dive, at least a little, in corners. The way I had my fork set on Sunday, Chimney Rock felt double as rocky as ever. The soft or "full on" rebound was adversely effecting it for sure. So it may be that it's not acting quite right.

Brett,

Good thoughts on the balance. Funny thing is that when I went through this with the rear suspension the fork wasn't an issue at all. It felt fine and I really seemed to have the bike dialed in, for exactly one ride at MD. Then it crapped out and now I'm almost back to the drawing board with this. I rode LM with the fork like this and didn't notice at all. But the next day at CR it was really rough. I do adjust a little depending on the park but I don't have it worked out enough to really say how they work together. But good thoughts regardless.

I'll have to play with it a bit more during the week.
 
Top Bottom