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

Pedantic critique: a measurement error from 25% sag to 29% sag is not 4%, it's 4 percentage points. The actual difference is 4/25=0.16, actually a 16% difference.

Also I couldn't make it through this very long video and the product is wildly expensive for what it is. 

This strikes me as excessive. Sag is a relative measurement anyway, there’s very little value in actually knowing the number. I guess you can get a little more precision out of it, and it could be cool to have as a team or a shop, but it’s pretty expensive for an individual

Sag is one thing, weight distribution is another. I think this is a component that varies quite considerably between people and isn’t taken account of at the moment. When you stick on a new stem that is 10mm shorter you’re changing your front wheel weight by as much as a couple of kg. His bar height no. 111-113cm is interesting, I need to check his theory - I am 5’7” and have landed at 110cm - again a 1-2cm change from my old setup has made a difference (positive). 

Id have no idea what sag im running. other than a starting point, thats all its good for - in the rear i'd guess closer to 20% than 30%(based on shock stroke) 
my bikes ride sick since I stopped caring about "but im about 30/20% sag"

Unless you have a bike with a very specific leverage curve designed around a specific sag point (old Santa Cruz?) sag seems almost completely irrelevant. Set up your suspension to your preferences for how it behaves dynamically on the trail not a single static value.

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. 

Back at it again creating his own hype by saying "don't believe the hype" and saying that he's going to change the mtb world. Not quite....

Setting sag is not that deep, I've done this with measuring the shock sag and just looking up what sag that is at the axle using a linkage model on the computer (cost 0€).

Let's say you have no idea what your preferred sag would be, how will it matter how you measure it?

You have to test sag which means the function is what matters, not how you got there. He's marketing his own invention as if the actual number is the important part which I feel is a pretty rookie mistake because most people know what clickbait is by now. 

His invention may limit inconsistency on a level that will only matter to the mechanic of top level athletes. I see no value for the consumer market for something like this, and as more people try to hint at is that if you can repeatedly measure something then that is the important part. 

So for simplicity let's say you have an airshock. You test sag till you like how it feels, then you should know which pressure this is. If you now use the same digital shockpump(digital pumps are more accurate than analogue if you repeatedly use the same pump, because a specific number on that is easier to read and plot in time and time again than say reading 197 psi off an analogue dial) over and over, you will repeatedly hit your preference.

His product seems like a product for people trying to make a new frame, to labtest things also without just looking at a monitor. Anyhow, I have litttle faith this will be a consumer hit product.

It’s not important how accurate your sag measurement is, what is important is that you measure it the same way consistently. Most air gauges and weight scales are not all exactly accurate or calibrated but who cares!?

As long as you are measuring the same way consistently then you can find the sag that works for you, even if it’s 31,5%

The fact is that sag as a measurement is a subjective number because we all have different tastes in how our suspension should ride and feel, it isn’t about hitting some exact specifically accurate measurement of sag that is defined by science as being the perfect setting…

I was under the impression that kinematics were created such that various figures/values (antisquat, progression, axle distance, etc) are designed and created to be set values at a given point in the shocks length when sagged (e.g. you have x antisquat at 30% of the shock stroke), not the wheel travel. So this would cause it to deviate from the intended values if you set sag based on wheel travel instead of shock length when weighted, no? Is my understanding mistaken?

I always new Dave was an avid MBAction reader - https://mbaction.com/garage-files-how-to-set-suspension-sag-using-motools-slacker-digital-sag-scale/8/

I like how he assumes none of us ever heard of that tool or read the Motorcycle Suspension Bible....but apparently we are all morons?

I don't normally get to caught up in everyones theories since there are many ways to do it, and each is fine as long as its vaguely repeatable, but this is claiming an awful lot of precision for measuring the sag without any way of checking the weight distribution which can introduce just as much error!

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.

Your onto something, but I just refuse to believe that someone wearing an all white kit, googles and half shelf, with a hip pack, on a DH bikes, knows much of fuck all.

Jokes and fashion aside, Rulezman is a knowledgeable dude, and I appreciate what he brings to the sport, but this is just totally unnecessary. 

The absolute best way to measure sag, is to use a telemetry system like BYB and look at dynamic ride height.

Second to that, seated on level ground, cos its free and repeatable, and tune from there. 

Sag is a reference point.

Do yourself a favor, cut your sag O-rings off and live free! This was actual advise from Mr Vorsprung himself in a Gondola in Queenstown.

It's even more irrelevant on a moto with the whole tape measure and sharpie mark on the rear fender that anyone can do for free.

I’m certain Dave is really good at what he does (I’d love some pro ride his tuned suspension vs. stock and see what they say).

My favorite part tho is his good ole Italian attitude aka very strong and confident about himself 😁

The line between having fun on a bike and totally geeking out is OFFICIALLY BLURRED!

That guys is silly as they come.  Again another rider trying to fix talent with gimmicks 

Hard to take a guy serious that rides Kendas.

"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. "

Wait what, maybe the language used is wrong, but more progressive bikes would likely need more than (over) 30% sag, while linear bikes can be run well under/less than 30% sag. 

As others have said, I roughly check the sag on my first setup to know the rough number of psi I need, then it's all about feel. My last 2 bikes have been a battle to setup due to overly low BB height. 

This is what I was going to put on his IG POST.. old school plot reading , like in my college days.. get your mm of shock strike and go to the leverage curve of the bike and voila you read your wheel travel.. i guess these days people are back to selling snake oil as the population gets dumber and dumber ( in a different way, too busy scrolling, zombies)

Jeeeesus, just buy tape measure and measure distance between rear axle and rear edge of the saddle if you want to be moto. Or go ahead and buy sag master from racetech for 10bucks, moto AF. This is just dumb.

This is where the argument for measuring at the wheel comes from - you are correct when looking at % sag at the wheel, but the change in rate through the stroke means you have an inversion of % shock stroke used vs % of wheel travel used. Ie on a progressive bike, 25% shock sag might equal 30% wheel travel and 75% at the shock is 70% at the wheel. But on a more linear bike 30% at the shock might be 25% at the wheel. 

Typical Dave with his absolute claims. Things like 15mm stems are the only way and anything else is too flexy and unusable. Using XC tires on his "enduro" bike. Claiming everyone should have a bike 2 sizes up with 1300mm+ wheelbase and any bike with pedal kickback is completely useless etc etc.

Granted he has some interesting theories but the way he dismisses everyone in the industry gets old real fast. This rebranded product is the perfect example of his attitude. He's numero uno and we're all plebs.

🤨 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.

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. 

This is an example of percent wheel travel as a function of percent shock travel. In this example, all have 160 mm of travel and a perfectly linear (in the mathematical sense ie. in the form mx+b) leverage curve. The green line is 50%, the blue line is 30%, and the orange line is 10%. The largest difference in percentage is at 50% shock travel. This is the point at which the aforementioned leverage curves converge. Running more sag on a more progressive bike can result in the ratio of up travel to down travel from the sag point being thrown off.

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. 

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