Had an in depth chat with the guys at TFTuned the other day whilst I was looking for some advice re set-up. My Reba 29er RTL’s are set at circa 25ish%. My riding trails are a very broad mix of technical ST & general XC stuff with very little top speed DH or mega jumps / drop offs.

To cut a long story short…they explained that the manufactures fork sag recommendations can be very misleading as it’s a VERY general rule. Obviously head angles, body position all have a dramatic effect on the forks initial sag and ultimately as to how it reacts to bumps / rocks / roots.

So…

1. What’s yours set at?
2. Have you followed the ‘general’ guidelines?
3. and have you fettled much with it?

The pressure guides were as much use as mystic meg and the lottery.

Generally start with about 25% sag and then see, first few rides with a shock pump and fiddle head on, lots of tweaking especially if I find the magic loop with everything on it. Also I will change it if I’m stepping it up a level or toning it down a bit. The less adjustment the fork has the harder it is to set with air alone.

…and another thing. How do you measure sag properly – when I sit normally on the bike the forks hardly compress at all as my weight is mostly over the back wheel. Id have to remove nearly all the air to get the recommended sag doing this. The only way to get the recommended sag with reasonable pressure is to stick my chin on the bars – which is not my normal riding position. I cant be the only one to have noticed this?

To measure sag
Front
Move the O Ring down or get them dirty
Get on bike, get mate to hold the bars
Stand and move to the “Attack” position ie weight forward elbows bent weighting the front (smoothly) return to sitting and get off.

For rear
Get on gently, lean bike over possibly and sit gently on the bike ie weight resting on the bike not bouncing.

The recommended pressures for my Revs didn’t suit me at all I like a fair bit of low-speed compliance so I took the pump with me and fiddled with them over the course of a few rides. When it seemed OK in this respect I made some more small adjustments to see if it would make it better/worse overall and then left it.

I think the static sag is somewhere in the region of 1/3 but I don’t have a ‘static’ riding position so it moves about quite a bit.

I always set mine for around 20% when I’m standing on the pedals and over the front. I want my forks working best when I’m on the way down.

Stand and move to the “Attack” position

Ahh – My “attack position” is arse touching the back wheel, eyes closed, face contorted in fear and buttocks clenched tighter than a gnat’s chuff.

This is the problem I think 🙂

Ahh – My “attack position” is arse touching the back wheel, eyes closed, face contorted in fear and buttocks clenched tighter than a gnat’s chuff.

At this point I may suggest seeking professional assistance in set up and skills 🙂

+1 on wanting the suspension working best when I’m descending. I set the sag on both ends of my bike standing with all my weight on the pedals. Stand up, bounce it up and down a few times, let it settle and then check it like that. As you say, just sitting on the bike the forks don’t sag much at all. Done like this, the bike comes out feeling very well balanced front to rear when out of the saddle.
I run about 30% rear, 20% front set as described.

Remember to wear what you ride in when doing this, no point setting the sag if you’re wearing your best asda suit.

I gave up setting sag by “attack position” because my attack position changes depending on the gradient of the trail, the terrain type of the trail, the camber, whether I’m pedaling out of the saddle, etc.

If I stand up in attack position I sag probably around 30 – 35% on 140mm forks – looks entirely too much sag, but on the trail when I’m down low facing downhill it works fantastically.

This combined with my shock fork not being accurate enough to gauge 1psi at a time so I gave up trying to get it more exact than the current PSI. 😆

I run my Fox 36’s with not much sag. I ride XC / techi / agressivly and look for stuff to pop off. Real combination.

I ride a Transition Covert with a CCDB rear. So for me my bike has to climb well as well as soak up big hits.

I like to sprint short uphills standing up and dont look for it to soak up small trail bumps.

Most of my mates think my forks are hard, but they suit my riding style and when I go to Woburn / Chicksands they still manage to save my ass when it goes pearshaped.

All set ups will be a sort of compromise if your ride a range of trails. Pick the compromise that suits you. Also worth experimenting as a lot of “advice” is complete rubbish. You have to learn it yourself.

About this much. (Holds up thumb and index finger). Tried to setup properly once, all seemed a bit soft so I put some more air in. Now it feels about right.

TBH I could do with switching to coils and getting a custom spring and gate valves made and tuned properly by someone who knows what they doing. I’m a fat fecker who rides it like I stole it.

I go by feel and bottom out prevention, means i generally arrive at around 15% sag. I dont worry about small bump stuff, your tyres are there to deal with that stuff, or just ride faster, the small bumps disappear then.

This “attack” position is misleading, who actually rides whilst attempting to touch their chin on their stem?

When im setting sag with customers, i generally get them in a standing, “strong” position. So standing, straight, neutral, with slight knee bend, heels slightly dropped if you want to call it that.

I mean, what postion makes more sense?

Or

Dont get into the mindset of “i must use all the travel”, if your riding doesn’t require it, it doesn’t require it. Having things too soft, will make for a nervous ride on slow steep tech stuff, pedal worse, wont save you, lose agility for hops and wheelies etc. It’s about quality rather than quantity.

The actual recommendations on the fork have never been within a country mile, for me- I’m 2 spring rates off for Rockshox, and about 30% out on the air settings.

As for amount of sag- that’s a matter of taste, also influenced by your suspension design and components. I run my Herb bang on manufacturer’s recommendations as they’ve had clever people with rulers and stuff work out the shock linkage, it works best reacting off a specific point. Forks, I stick where the whole bike seems to work best- my Revs I run harder, my Lyriks are probably about typical. If I ran my Foxes at the recommended sag I spent the whole time in the bottom of the travel, orrible.

All in all- fanny about with it til it works.

This “attack” position is misleading, who actually rides whilst attempting to touch their chin on their stem?

Your description of the attack position is misleading, weight forward over the bars arms bent a little – not kissing the crowns….

I tend to ride mostly over the front when I’m feeling confident and riding better. The better the fork is set the better that goes.

Again trying to tune a fork with air pressure only or by playing with the knobs randomly is never going to work.

Stick a shock pump in your Camelbak and take it along with you on a ride. Just remember the numbers in there last and work from there. Never really got on with setting by sag, such a vague measurement that’s totally throw out based on fork/rear setup, compression damping/spring rate etc.

Oil levels are also pretty important and usually nothing close to what manufacturers suggest.

I set air pressures so that I get around 90% travel after some proper descending. Usually this seems to be about 20-25% sag. You need the forks to hold up while braking hard downhill so you don’t wallow and lose balance if you get things wrong. A fork bouncing around at the limit of it’s travel while braking into a corner could send you into orbit.

When you’re in ‘attack position’ and not mid-move (corner/pump/drop/manual/etc) your weight should be entirely through your bottom bracket. That’s the position to be in when first setting fork sag. For rear shocks I’ve seen suggestions of using the halfway point between attack position and seated as a starting point. But they’re only starting points! My forks were at just under 20% sag but since having slippier seals fitted they’re a bit too soft feeling at that so they need a few more psi to feel right, so maybe closer to 15%. That’s still over 20mm of sag though. When I’m cornering and weight up the front that can easily push them towards 40mm sag before the G-force compression kicks in – the last thing I want is to be pushing hard round a natural berm, hit a rock and bottom out.

Dont get into the mindset of “i must use all the travel”, if your riding doesn’t require it, it doesn’t require it.

This is so true! I’m trying to think of when I use all the travel whilst riding correctly and it’s rare: Nose-diving landings I’ve used all the travel (and that’s saved me from an OTB). Maybe cornering through a really rough section of trail so I’m leaning on the bars and ploughing through the lumps and bumps – but I’m more likely to break the corner into smoother sections to turn in and straight line through the rough bits with the front lighter.

Stick a shock pump in your Camelbak and take it along with you on a ride.

Dont forget to componsate for the extra weight of the shockpump when setting sag

ndthornton – Member

Dont forget to componsate for the extra weight of the shockpump when setting sag

Very true, I also adjust mine by a few PSI depending on whether I have been for a Richard before heading out.

If you setup your sag for the downs… Shouldn’t you set it on the downs, as there will be more weight over the front due to the angle..?

Or at least angle the bike slightly when setting it?

I have my forks set up quite firm, my mate who’s pretty much the same weight rode my HT the other day and he hated them as they are stiff and you only get full travel on drops etc, but then again they are only 100mm Rebas on a 29’er

It’s got to relate to the bikes use IMO

I run My DH bike quite soft these days, I used stick religiously to about 25% with less sag at both ends but TBH I wanted the bike to grip as well as it can over roots and rocks more than I wanted it to pedal well so I’ve changed springs about and set it at around 30-35% both ends, I regularly find the bump stops on that bike…

On My HT however I’m still using 15-20% (110mm fork), I don’t bottom the fork all that often, but it feels comfortable for most of my riding…

Sag is only an indicator that the spring rate and preload is correct. But, with forks that have no compression damping adjustment, you have to balance making sure you’re not bottoming too soon, and that you are using the full capability of the suspension over your max hits (otherwise the suspension is set too hard).

I found with my air forks there was no-way at all to get everything even close to useable (due to my 16 stone). Adding air to give a decent sag would prevent the fork getting full travel.

Now converted to coil (with the correct weight springs after some experimentation), I get full travel over the nastiest hits on my regular riding, and this equates to 31% sag seated (on a 120mm travel fork). I really couldn’t care less if that’s in spec or not, the fork is as plush as a plush thing (to my MTB suspension ignorant body).

Edit: Just looking at my notes, I also experimented with preload to arrive at an ideal amount.