Video: Tech Tuesday - How To Accurately Measure Sag
There is a lot that goes into setting up a shock for your weight, local terrain, and riding style. Accurately setting shock sag is a fantastic starting point but how do you do it? In this video, Henry Quinney covers everything you need to know to properly set sag on your bike.
Author Info:
Must Read This Week
Sign Up for the Pinkbike Newsletter - All the Biggest, Most Interesting Stories in your Inbox
PB Newsletter Signup
Rockshox: patents and refuses to allow others to use handy lines.
On dirtbikes you measure a bit different, sim to what you are suggesting....
Did you put any work into making it a reality?
If so, feel free to challenge their patent, and make it free for everyone to use.
I am willing to bet a 6pack on the fact that if you had an idea, that could lead to you making money, you would do everything you could to protect that, so others couldnt make money from it.....
Let me know if you need a little guidance
Which is why you're usually downvoted into oblivion.
I dont need to try and convince you of anything
What ever will I do if the other PB comment pundits dont approve of what have to type, how will I come back from that?
Im not to stressed over here about what you think, doesnt bother me one bit
We've been using O-rings and zip ties on fork and shock shafts to measure travel for DECADES, so adding ruler marks, like the rulers and calipers we normally hold up next to the o-ring, is pretty f*cking obvious a thing to do once we had the technology to print onto slick metal surfaces in a way that was durable enough to withstand sliding past the bushings repeatedly for tens of thousands of cycles.
Oh and there's also the thing they didn't invent the idea.... SRAM copied it from another field, and that's another problem with the patent system, you can re-patent existing inventions that do the same thing simply by taking advantage of the earlier patent not listing "bicycles" as an intended application for the invention.
I don't think what you say is entirely true, I'm not an expert, but you are getting a patent in IP, that IP can't just be transferred directly to another application....it doesn't work like that.
If we use SRAM as an example, they may have patented the application of "% sag on bicycle shock body" while somebody else had the patent for "applying markings on anodizing on a friction surface", SRAM would of noted that secondary patent in theirs patent application and would have to, potentially, pay royalties to the initial party for using their idea. The novelty of the idea of applying it to shock bodies was SRAM's.
Most companies don't want to take that risk, and either pay loyalties (might be cheaper than lawyers) or just make forks without marks and accept that they sell 0.1% less of them.
Too squishy? Add more air.
Not enough squishy? Let some air out.
That'll be £5.
Too boingy? Put a bigger boing in.
Not boingy enough? Smaller boing.
That's for free, but compression advice is £5 a minute and you have to argue with internet people about it first.
Also, if you use plastic callipers it's easier to measure the sag without scratching the stanchion.
And if you need them to tell you what 30% percent of one of those numbers is... then you're too stupid to even try and set sag at all.
As he says in the intro: "Accurately setting shock sag is a fantastic starting point but how do you do it?" We still don't know.
Sag is an utterly meaningless point of air pressure which is nothing more than a starting point which you're probably going to change from anyway (unless you like how it rides...giggity).
To answer your question, sag is sag, and don’t factor in those three mm.
I have also noticed that many, if not most, riders do not use all of their available travel, even in bike parks.
I have always set my shock and fork pressure using jumps. I built one in the back yard of my previous residence. Now I use a jump line called Solstice (in Salida). I stamp the jumps in open mode and set the pressure such that nearly all of the travel on both ends is in play without serious bottom outs. This procedure does yield a sag (for me) between 15 and 30%, but (for me) is more accurate and repeatable.
100% sag = 100% travel,
0% sag = 0% travel,
30% sag ≠ 30% travel.
Why is that? Bike rear suspension kinematics almost never have a linear leverage curve. So 1mm of stroke travel of the rear wheel on the beginning of the shock stroke does not equal 1mm of shock stroke travel on the end of the stroke. It's not all that important if you set you bike up by feel, but it does have an impact when comparing bikes because 30% sag on one bike may by quite a different amount of travel than 30% on a different bike. So for instance in bike tests, it might preferable to compare bikes set up at 30% travel (whatever the sag is for that), instead of simply going for 30% sag readout on the shock, to get the most consistent comparison.
Sag is also determined by negative air spring volume/pressure/compressionratios more than the mid-stroke that actually matters. Rockshox Debonair B1 fork springs give you totally different response to C1 at the same sag.
Set air pressures by frequency: www.shockcraft.co.nz/technical-support/setup-suspension/1-page-suspension-setup-guide
for forks use the same method, just divide for travel into 100. 100 divided by usable fork travel of 165mm- '.606'.... measure sag lets say 33mm, then multiply .606.... bam, %20 sag
hope this helps.
Also which "Fox Float"? There are many shock with that name, and almost all will require different pressures to reach the same sag on a single bike. I've had various "Fox Floats" on various bikes, and some required 20-30 psi less than my weight, while others needed 80 psi more than my weight.
The shock's brand (and model) alone has almost nothing to do with how the final pressure will correspond to your weight.