Have We Been Measuring Sag Wrong? (and how to fix it...)

yzedf
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Hebron, CT US
Fantasy
6/16/2025 10:47am
WillijPDX wrote:
🤨 I get the nerding out on sag, but the kit is as expensive as a shock wiz, with the shock wiz being way more useful...

🤨 I get the nerding out on sag, but the kit is as expensive as a shock wiz, with the shock wiz being way more useful to dial in your suspension to riding style, compliance, and terrain. Strikes me as some obsessivness getting way out of control.

yzedf wrote:
The wiz only works if you run air, which this guy is a big coil advocate. This video did get me to check my shock for the...

The wiz only works if you run air, which this guy is a big coil advocate. 

This video did get me to check my shock for the first time in a month, so that’s good I guess. 

WillijPDX wrote:
I agree with you but that wasn’t my point. I am saying the cost is as expensive as a tool that is better for the vast...

I agree with you but that wasn’t my point. I am saying the cost is as expensive as a tool that is better for the vast majority riders. Fine if a shop or fitter buys it to help people for their initial set ups. Just not a price point for an individual for what the kit actually does. 

Duck tape, a stick and a helper with a tape measure will be good enough. 

DubC
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CA US
6/16/2025 10:48am

What a time to be alive. Unbound opulence. 

Kids, make sure you understand the gradient of the trail you are riding that day too so you can make sag adjustments based on likely weight distribution changes due to gradient variances. Spend 1-2 hours on bike setup/prep. Ride ~4-5 laps of 3-5 minutes each (total ride time 12-25 minutes). Spend 2 hours analyzing data, posting strava, posting grams, posting trailforks, posting youtubes, arguing with netbangers. Sit back, soak in all the WINNING. 

This is TRULY what peak cycling enjoyment looks like.

13
yzedf
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Hebron, CT US
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6/16/2025 10:49am

WE'VE BEEN MEASURING CRANKS COMPLETELY WRONG! THEY SHOULD BE MEASURED FROM THE GROUND!

It’s the rocks to the bottom of my SXg that’s usually my limiting factor LOL 

3
29
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AT
6/16/2025 11:00am

While we’re on the topic of suspension gimmicks, is there anything in the vicinity of System 2 from Motion Instruments?


BYB is too expensive for how I’m bumbling down the trails, and Shockwiz doesn’t work on my bike (Öhlins fork and coil shock). 

Don’t think anyone near me is doing rentals or setup days either. 

System 2 would have been perfect in terms of ease of setup and relatively low price compared to other options but never came to be. 

4
Fox
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Durango, CO US
6/16/2025 11:10am

Not sure I wanna watch this. Dave's voice saying "IT DOESN'T MATTER" about weight on one of his other vids from a few years back still rings in my head! 

It does matter a little for me as much of my riding in the summer is long rides for long descents at10k feet + elevation. But his voice is there reminding me to not sweat it too much. 

If I watch this vid, am I gonna be stuck with some other thing in my head about sag? 

1
yzedf
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Hebron, CT US
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6/16/2025 11:19am
Fox wrote:
Not sure I wanna watch this. Dave's voice saying "IT DOESN'T MATTER" about weight on one of his other vids from a few years back still...

Not sure I wanna watch this. Dave's voice saying "IT DOESN'T MATTER" about weight on one of his other vids from a few years back still rings in my head! 

It does matter a little for me as much of my riding in the summer is long rides for long descents at10k feet + elevation. But his voice is there reminding me to not sweat it too much. 

If I watch this vid, am I gonna be stuck with some other thing in my head about sag? 

Use percentage of wheel travel instead of shock. He’s the euro distributor of a $350 tool. 

That’s pretty much the whole thing. 

1
6/16/2025 11:54am

I think this device is Nice!  Its pretty easy to do and If You want to Setup the Bike with more weight(Winter/ different cloth helmet) then its so easy to do IT with this device! And the Option to Check  the bushing Play is also realy cool! Yes there are Other ways to Check it but i think this gives You a good indication how bad it is.  but yeah He is pretty confident about it 😁

1
3
Splayleg
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Los Gatos, CA US
6/16/2025 12:40pm
perplex26 wrote:
I think this device is Nice!  Its pretty easy to do and If You want to Setup the Bike with more weight(Winter/ different cloth helmet) then...

I think this device is Nice!  Its pretty easy to do and If You want to Setup the Bike with more weight(Winter/ different cloth helmet) then its so easy to do IT with this device! And the Option to Check  the bushing Play is also realy cool! Yes there are Other ways to Check it but i think this gives You a good indication how bad it is.  but yeah He is pretty confident about it 😁

How do you choose which words to Capitalize and do you by Chance wear googles around your neck while wrenching?

5
6/16/2025 12:43pm Edited Date/Time 6/16/2025 12:48pm
Fox wrote:
Not sure I wanna watch this. Dave's voice saying "IT DOESN'T MATTER" about weight on one of his other vids from a few years back still...

Not sure I wanna watch this. Dave's voice saying "IT DOESN'T MATTER" about weight on one of his other vids from a few years back still rings in my head! 

It does matter a little for me as much of my riding in the summer is long rides for long descents at10k feet + elevation. But his voice is there reminding me to not sweat it too much. 

If I watch this vid, am I gonna be stuck with some other thing in my head about sag? 

Yes

And I thought he did a video saying weight was super important, or maybe that was just lightweight wheels and xc tyres at 30-something psi, and the rest of the bike weight didn't matter?

@AG Pennypacker  - it doesn't matter what tyre you use when you pump them all up rock hard!

1
synBike
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Location
North Vancouver, BC CA
6/16/2025 12:49pm
No, we haven’t been measuring sag wrong. Any method of measuring sag that is repeatable is an acceptable way to measure sag. As it is something...

No, we haven’t been measuring sag wrong. Any method of measuring sag that is repeatable is an acceptable way to measure sag. As it is something that must be tuned as opposed to setting to a specific percentage, being able to repeatably measure sag is the most important thing. You can do this seated and measuring at the shock just fine. If someone wants to measure it with a whole bunch of kit that’s fine, but telling everyone they are wrong and do it wrong is silly. It is definitely worth noting that on more progressive bikes you shouldn’t be surprised if you run under 30% sag at the shock, though. 

As an aside, I find it comical that there’s all this accuracy and yet wheel travel is being measured by eyeballing a ruler in the frame and the measurement is impacted by horizontal wheel travel as well. 

This 1000%. Sag is a nearly useless measurement for anything other that a very initial baseline for setup on a new bike. Depending on the kinematics and dampers involved you might be anywhere from 22-32% sag between platforms with an optimum setup. 

The real question is not if we are measuring it correctly but if we should we be measuring it at all 😂 

4
6/16/2025 12:54pm
perplex26 wrote:
I think this device is Nice!  Its pretty easy to do and If You want to Setup the Bike with more weight(Winter/ different cloth helmet) then...

I think this device is Nice!  Its pretty easy to do and If You want to Setup the Bike with more weight(Winter/ different cloth helmet) then its so easy to do IT with this device! And the Option to Check  the bushing Play is also realy cool! Yes there are Other ways to Check it but i think this gives You a good indication how bad it is.  but yeah He is pretty confident about it 😁

Splayleg wrote:

How do you choose which words to Capitalize and do you by Chance wear googles around your neck while wrenching?

Sorry but english is Not my mother tounge. And grammar is also difficult for me! But Nice that You think that you are a  better Person or You are smarter because your grammar is on Point. My Phone dose also some auto correction which makes it worse. In contrast to You i wrote my Personal opinion about the device! 

 

4
6/16/2025 1:12pm

Hard to trust somebodies judgement when they are wearing all white mountain bike clothing doing measurements with goggles around their neck. 

2
6/16/2025 2:26pm Edited Date/Time 6/16/2025 2:27pm

I have the DRC tool for measuring sag on my moto while solo. I think these are still too much money, but it's a lot better than the $150+ for the Slacker tool. Accomplishes the same thing and is $40. 
https://www.rockymountainatvmc.com/parts/drc-sag-checker-p 

2
6/16/2025 2:32pm
No, we haven’t been measuring sag wrong. Any method of measuring sag that is repeatable is an acceptable way to measure sag. As it is something...

No, we haven’t been measuring sag wrong. Any method of measuring sag that is repeatable is an acceptable way to measure sag. As it is something that must be tuned as opposed to setting to a specific percentage, being able to repeatably measure sag is the most important thing. You can do this seated and measuring at the shock just fine. If someone wants to measure it with a whole bunch of kit that’s fine, but telling everyone they are wrong and do it wrong is silly. It is definitely worth noting that on more progressive bikes you shouldn’t be surprised if you run under 30% sag at the shock, though. 

As an aside, I find it comical that there’s all this accuracy and yet wheel travel is being measured by eyeballing a ruler in the frame and the measurement is impacted by horizontal wheel travel as well. 

synBike wrote:
This 1000%. Sag is a nearly useless measurement for anything other that a very initial baseline for setup on a new bike. Depending on the kinematics...

This 1000%. Sag is a nearly useless measurement for anything other that a very initial baseline for setup on a new bike. Depending on the kinematics and dampers involved you might be anywhere from 22-32% sag between platforms with an optimum setup. 

The real question is not if we are measuring it correctly but if we should we be measuring it at all 😂 

Agreed on all counts. If it's repeatable, it's as valid as it can be, but it's not a very meaningful target in itself, it's a byproduct of having the necessary spring rate for the loads you put on the bike and the ride quality you're looking for. Worrying about the precision of the sag measurement like that is utterly pointless if you're ignoring the factors that actually matter when selecting spring rates.

On that note, we have a few different ways that we calculate spring rates for the Telum on any given frame (tuninghub.vorsprungsuspension.com) - if you know what you want already, you can tell us how much sag you want, or what spring rate you prefer if you already run a coil. 

However, the default way we do it is actually to estimate how much force you're able to put through your suspension (based on your weight and how hard you ride, what kind of terrain you're on, how big you send it etc) at a point very deep in the travel (not quite bottom out because some frames do whack stuff at the very end of the travel that's better to ignore for the sake of ride quality the other 99.9% of the time). Then we work backwards to work out what spring rate that requires, and how much sag that gives you as an incidental outcome of the spring rate that's necessary for you to be able to use your travel effectively. On some bikes, that might mean you're at 25% sag, others you might be at 35%. This is due to the characteristics that are designed into the frame's leverage rate that mean you can't necessarily translate sag figures from one very linear or even falling-rate frame to a very progressive one. 

There are other ways to do it too, like using the spring energy storage, but there are some limitations to that particular method insofar as being heavily affected by the progression prior to the sag point with certain leverage rate curves. Natural frequency can be used too, but it doesn't translate particularly well between different bike travels because the whole point of longer travel is softer springs (lower natural frequency) and it doesn't do anything to account for bottoming resistance or travel usage.

12
brash
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950
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4/24/2019
Location
AU
6/16/2025 4:45pm

what a co-incidence, the other site has an article on exactly this topic lol

 

4
6/17/2025 9:47pm

Love that the two top guys in the squish world replied here and not on the other wise.  Vital superiority 

1
6/23/2025 9:33am
29 wrote:
While we’re on the topic of suspension gimmicks, is there anything in the vicinity of System 2 from Motion Instruments?BYB is too expensive for how I’m...

While we’re on the topic of suspension gimmicks, is there anything in the vicinity of System 2 from Motion Instruments?


BYB is too expensive for how I’m bumbling down the trails, and Shockwiz doesn’t work on my bike (Öhlins fork and coil shock). 

Don’t think anyone near me is doing rentals or setup days either. 

System 2 would have been perfect in terms of ease of setup and relatively low price compared to other options but never came to be. 

Motion Instruments is done.

BYB V3 is the next option.

1
DServy
Posts
239
Joined
5/28/2015
Location
Jackson, WY US
6/23/2025 9:52am
29 wrote:
While we’re on the topic of suspension gimmicks, is there anything in the vicinity of System 2 from Motion Instruments?BYB is too expensive for how I’m...

While we’re on the topic of suspension gimmicks, is there anything in the vicinity of System 2 from Motion Instruments?


BYB is too expensive for how I’m bumbling down the trails, and Shockwiz doesn’t work on my bike (Öhlins fork and coil shock). 

Don’t think anyone near me is doing rentals or setup days either. 

System 2 would have been perfect in terms of ease of setup and relatively low price compared to other options but never came to be. 

Motion Instruments is done.

BYB V3 is the next option.

If only it worked for bikes with shock tunnels. Looking at you Forbidden…..

6/23/2025 12:56pm
TEAMROBOT wrote:
A lot of good thoughts here, but just to play devil's advocate, have we considered the possibility that he's right and we're all stupid and everyone...

A lot of good thoughts here, but just to play devil's advocate, have we considered the possibility that he's right and we're all stupid and everyone in the bike industry has collectively been doing it wrong for 30-40 years and he alone can tell us the answer and it requires buying this expensive new product from his webstore?

I mean at least consider it, is what I'm saying.

I start most endeavors with the assumption that I'm doing it wrong. 

His video convinced me otherwise. 

1

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