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Sag


larlev

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I've been reading a lot on setting sag. I've set my stumpy per Specialized website.

I was messing around today with the bike. I'm 180lbs with riding gear, water, etc.

I've weighed myself with home scale....supposedly good scale, within .5lb accuracy 

Specialized says 84psi for fork, 217 for shock.

I'm wanting 26mm sag on fork, so I've had to lower pressure down to 70.  I'm basically splitting the difference with 23mm firm and 30mm plush. 

Shock is set and st 217 with gear on I'm not getting oring in the sag tool. Been very careful with getting on and off the bike.

 

 

Guess my question is how accurate are the manufs recommended air pressures? Seems I should ignore the numbers and just go by measuring. Is this how most of you do it, or are you using manufs info and calling it good?

 

Edited by larlev
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I always seem to end up using significantly lower fork air pressure than recommended for my weight. The shock recommendation is often enough pretty close, though the mfg spec may be for 20% sag and I prefer 25-30% for most of my riding.

As a general rule, after initial sag setting, I'll set the o-ring on fork and shock on each ride to monitor whether I've used most of the travel (90%?) at some point. If that is not the case, I'll lower the pressure some to dial it in to better make use of all that the suspension offers for my riding style/location.

Edited by Ridenfool
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16 minutes ago, Ridenfool said:

I always seem to end up using significantly lower fork air pressure than recommended for my weight. The shock recommendation is often enough pretty close, though the mfg spec may be for 20% sag and I prefer 25-30% for most of my riding.

As a general rule, after initial sag setting, I'll set the o-ring on fork and shock on each ride to monitor whether I've used most of the travel (90%?) at some point. If that is not the case, I'll lower the pressure some to dial it in to better make use of all that the suspension offers for my riding style/location.

I'm finding if I measure 3x's I get a damn different measurement each time. Ugh. I'm sure its rider error.

I'm setting at 82/212 and forgetting it for now. I'll ride and see where I'm at.

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Fork sag is super hard to measure consistently and, from my experience and what I hear from lots of others including pros, pretty useless. When your fork feels good, it’s right. I’m usually at less pressure than the manufacturer’s recommendation.

As for the rear, most frames are designed for 25-30% sag, so measure that and once you’re close tune based on travel used, ride feel, etc. 

Compression, rebound, and volume spacers play a big role, so once you’re in the ballpark with air pressure move to those. 

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I aim for a buttery smooth ride. When I'm out of shape, like now, I can run less pressure as I'm not hitting things as hard as I would were I in more optimal condition. Keeping an eye on the o-rings is a consistent feedback mechanism. As my physical conditioning improves I'll likely be adding air to keep me in that 90% or so travel use range.

Carrying a shock pump adds weight on every ride. Carrying more weight increases the level of workout, thus, leading to better conditioning. Or, so I keep telling myself every time I hoist that heavy pack onto my back.

Edited by Ridenfool
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2 minutes ago, Ridenfool said:

I aim for a buttery smooth ride. When I'm out of shape, like now, I can run less pressure as I'm not hitting things as hard as I would were I in more optimal condition. Keeping an eye on the o-rings is a consistent feedback mechanism. As my physical conditioning improves I'll likely be adding air to keep me in that 90% or so travel use range.

I'm with you on conditioning. Being off the bike for 8yrs has been interesting. Everything is sore after a ride. I guess being 48 doesnt help either. 

I swear I could do some of those lines back then that I cringe looking at now. Sure did miss the hell out ofv riding 

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12 minutes ago, DanielC said:

Fork sag is super hard to measure consistently and, from my experience and what I hear from lots of others including pros, pretty useless. When your fork feels good, it’s right. I’m usually at less pressure than the manufacturer’s recommendation.

As for the rear, most frames are designed for 25-30% sag, so measure that and once you’re close tune based on travel used, ride feel, etc. 

Compression, rebound, and volume spacers play a big role, so once you’re in the ballpark with air pressure move to those. 

+1

one of the biggest revelations for me when doing the Specialized suspensión tuning clinic was how fork Sag is hard to do on your own consistently, and you tend to over pressurize when doing it on your own.  I agree on spending more time on compression and rebound.  It has made a huge difference for me.

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As a pro mechanic I can say that manufacturer's air pressure recommendation are one of the more frustrating when it comes to helping customers with suspension tuning. Those charts don't take into account bike setup, riding style, a rider's proportions, ETC. I have been as much as 80psi off a manufacturer's recommendation to get the proper sag (then it obviously took some work to get the proper spring rate), but people will still argue when I tell them I recommend anything but what the sticker reads.

 

Bottom line, set your sag by taking measurements and then tune your fork/shock with that as your baseline.

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1 hour ago, Big_papa_nuts said:

As a pro mechanic I can say that manufacturer's air pressure recommendation are one of the more frustrating when it comes to helping customers with suspension tuning. Those charts don't take into account bike setup, riding style, a rider's proportions, ETC. I have been as much as 80psi off a manufacturer's recommendation to get the proper sag (then it obviously took some work to get the proper spring rate), but people will still argue when I tell them I recommend anything but what the sticker reads.

 

Bottom line, set your sag by taking measurements and then tune your fork/shock with that as your baseline.

Makes perfect sense.  What they are recommending isn't working. 

Was starting to get frustrated.

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Also, unless you are using a digital shock pump, and even if you are, I find the pumps to be the source of much frustration. Every time you put a pump on or take it off you are losing some pressure, so when talking about 70 vs 84, I'd expect a few psi is tied up in gauge calibration and pressure loss from the pump.

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8 minutes ago, Mattlikesbikes said:

Also, unless you are using a digital shock pump, and even if you are, I find the pumps to be the source of much frustration. Every time you put a pump on or take it off you are losing some pressure, so when talking about 70 vs 84, I'd expect a few psi is tied up in gauge calibration and pressure loss from the pump.

As I understand it you only lose pressure when attaching the pump.

When removing the pump the Schroeder valve is closed before the seal breaks and what is heard escaping is only the pressure remaining in the pump's hose.

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59 minutes ago, Mattlikesbikes said:

Also, unless you are using a digital shock pump, and even if you are, I find the pumps to be the source of much frustration. Every time you put a pump on or take it off you are losing some pressure, so when talking about 70 vs 84, I'd expect a few psi is tied up in gauge calibration and pressure loss from the pump.

In my "anal, have to have tools mind" I bought 2. Rock shox digital, and one that has a valve at end of hose that can be open or closed. It works really well. 

15464488668312131037572977426551.jpg

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I have multiple shock pumps. Standard 300psi Rockshox, 600psi Rockshox and a digital Fox pump. The digital is good for suspension that is sensitive to small psi changes. As far as accuracy they're probably all off a bit. Basically set your suspension to whatever psi gets you where you need to be and use that as your reference. Same goes for tire pressures.

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Another way to look at it is that the numbers really don't mean anything. Achieving repeatable results is more about whether the reading on the pump is consistent.

If you find that 100psi indicated is what works for you, airing it back up to a 100 reading on the same pump should provide consistency. Regardless of whether the actual pressure is 95 or 105 you are able to duplicate what you have determined to work for you based upon the reading on that pump.

Edited by Ridenfool
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I’m with Ridenfool. On small volume high pressure and high volume low pressure (i.e. plus tires) every pump seems to be way different. I just got a nice digital gauge for tires and grab whatever pump. I need a new shock pump guess I need to shop digital ones. My 15 y.o. Trek Wrench force is all over the place lately!


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