BikeCo Tips & Tricks: Basic MTB Suspension Setup
2020 brought a lot of new faces to MTB. We’re stoked to see more people benefit from the sport we all love. That said, a lot of shops simply can’t support rider development like we can. So, here’s a video & blog going through Basic MTB Suspension Setup.
We’ll look at sag, rebound, volume spacing, compression as well as high and low speed damping.
If you’ve linked over from YouTube skip the first video (but you might want to read the support text) and go straight to the second video.
Let’s jump in.
So in the first video we touch on two main theories of suspension. Sag & Rebound. Let’s take a minute and expand a bit further.
Also known as Droop in the motorsports world. Your bike needs to “sit into” the suspension when you’re riding.
This downward suspension is critical to compliance, braking and pedaling efficiency.
TOO LITTLE SAG
Without enough sag your bike will feel like it’s skipping across the terrain. Because, it’s skipping across the terrain!
It’s sometimes thought that stiffer is more efficient – but – on moderns bikes the design requires a percentage of sag to put the drivetrain into the most efficient position. There’s also the difference between laboratory efficiency and trail efficiency. Without some “bite” you’re going to spin wheels.
Another to take into consideration: anytime your tires are off the ground you’re unable to change direction. Or brake. Or pedal for that matter. Point is, skipping across terrain isn’t totally ideal.
TOO MUCH SAG
If the bike sits too deep into its sag it will loose efficiency as well. It’s likely to run through (use more travel than appropriate) the stroke as well.
Hard bottom outs are hard to control. If you’ve got so much sag that you’re consistently hitting the bottom its’ going to take a big toll on the components too. Hard mechanical bottom out takes the spring rate to INFINITE and jars everything. Bolts, bits, and riders…
HOW MUCH SAG
There is an acceptable range on either side of typical setup for personal preference.
Most rear shocks are setup in the 30-37% sag range. That means the sit 30-37% into the travel, leaving 70-63% of the shaft exposed.
I’ve only had it happen once, but a client inverted that concept and thinking 70% sag was 30% was sure something was wrong with the shock. Something was wrong, but, not so much with the shock… We had a good laugh later.
Forks are typically setup in the 20-25% sag range.
It’s important to note that the fork should be setup at miminum equal to the rear shock in feel. Your fork can be even, or stiffer than the rear end. Don’t setup the fork softer than the rear end or you’re a lot more likely to go over the bars.
Rebound controls the shock’s extension. You increase the rebound control by slowing the flow of hydraulic fluid inside the damper.
The faster you ride the faster your rebound will be. You want to find a balance between a pogo stick bouncing you off line and too slow of rebound which will pack up and eat up suspension.
Generally I set my rebound frequency pretty close front to rear, although my fork’s air spring is set slightly stiffer than the rear shock.
Personally I know about the frequency I like when I bounce on the bike I think “One, and, a”. It’s not as useful without knowing speed I know, but, at the end of “one, and, a” the bike has resettled. It also helps me focus on the balance fore and aft if I know when I expect it to settle, rather than trying to feel both sides at the same time every time.
Rebound can get into the weeds pretty quick. Usually suspension manufacturers have a decent setup sheet based on weight at this point. But, you’ll have to fine tune it depending on your riding. Try to adjust it no more than about two clicks at at time.
Be wary just “taking” your fast buddy’s setup. For instance, I weigh more than the rest of the guys at the shop. I usually have to run a bit more rebound to make up for the additional air spring forces (from having a higher starting PSI at sag).
Almost all suspension offers air pressure, rebound and volume spacing tuning. With these three features interacting you can do a lot with your bike.
Let’s look at volume spacing, compression and high and low speed damping in the next video.
Between these two videos we hope you’ve got at least an understanding of what air pressure, rebound, volume spacing and compression are.
Admittedly it can be a bit of a challenge wrapping your head around “what does what” and in which combinations you’ll get the results you want.
But, let’s review again real quick.
Like air pressure and rebound most shocks have volume spacing accommodations. Volume spacing modifies how an air spring compresses.
ADDING VOLUME SPACERS
By adding volume spacers you reduce the air springs’ volume. This compresses the air more per MM of travel.
So, if you’re setting the same sag measurement you’d have LESS air in the shock at full extension. The volume spacer accelerates the ramp rate meaning at an equal sag the piston actually has the same PSI in either configuration. The ramp rate would continue exponentially giving the reduced volume setup a higher PSI at every position further in the travel.
You would add volume spacers if you were using too much travel for conditions or wanted a bit more support for corners or bigger terrain.
REDUCING VOLUME SPACING
Removing volume spacers does the opposite, making the shock feel more linear.
You might remove volume spacers if you weren’t getting full travel in appropriate conditions or if the suspension became too jarring to handle, making it ineffective as, you know, suspension.
Something we note in the video – for each rock, ledge, or whatever, a certain force is input to your suspension. That force needs to be dealt with.
With LESS spacers it will take MORE mm of travel to build the appropriate resisting force.
With MORE spacers it will take LESS mm of travel to build the same force.
I personally setup just below the total support I want with volume spacers and the fine tune with compression.
Compression is the opposite of rebound. It hydraulically controls the shock compressing. (finally a term that makes complete sense right?)
Adding compression will slow the shock (or fork) shaft input. This is used to better control the air spring “in” just as the rebound helps the air spring “out”.
Compression is set to help resist the shock diving too deep and to offer support to the rider.
Support helps keep the rider chest up, in the attack position with a bike that’s able to change directions. Without enough support your bike will feel like it’s burying the front end which can more easily launch you over the bars.
The rear shock’s compression has a similar job, to provide appropriate support for riding style.
HIGH & LOW SPEED DAMPING
The last thing we examine in these videos is high and low speed damping. In the past LOW speed damping was referring to the beginning of a shock or forks’ stroke. HIGH speed referred to the end of stroke. Not anymore.
Low speed damping modifies slower shaft speed inputs. Low speed adjustments are available on both rebound and compression depending on suspension models.
High speed damping modifies higher shaft speeds. Depending on suspension you may have high speed damping on rebound and compression.
As a reference, a smooth landing that uses most of the travel at a slow input rate is operating on the low speed circuit.
A harsh hit, like sprinting into a curb, might only use a small portion of total travel but if the shaft speed is fast it is operating the high speed circuit.
We know that there’s a lot of factors to take in when you’re learning about suspension.
Which is why at BikeCo our team offers client’s unmatched after sales service on bikes, suspension and Pro Tune services. We reach out to clients with a series of loaded questions to help fine tune setup. Suspension, Tire Pressure, Cockpit Setup – these are all factors that go into getting your bike from the “this is good” to “oh man, it’s dialed”.