Suspension Tuning

I'm putting these thoughts into words - before I forget them again - mostly for my own use in the future, but hopefully others will find this guide useful too.

First off, Manitou Suspension rocks. Their forks and shocks are some of the must tune-able on the market with simple but effective shim stacks to control brake dive and pedal bob. Also the ride quality to price ratio is unbeatable. This tune-ability means they can be finicky to set up, but spending the time to do so is well worth it. I've previously owned the Tower Pro fork and currently ride the Marvel fork and Radium rear shock.

1. The Spring.
   Start with air spring pressure. Set the sag at 20% front, 30% rear. You'll probably change this later, but it's a good starting point. A proper suspension setup should bottom out once every ride or two; otherwise, you're not using all of the available travel and carrying around extra weight for nothing. Higher air pressure, while it does work, is the wrong way to achieve reduced pedal bob. We'll get to that in a minute.
   
   If you have a fork like the Tower Pro with coil assist, things get a little trickier. If you can barely achieve the desired sag with low air pressure and it bounces around like a pogo stick when you stand and pedal, try installing a lighter coil. If you have too much sag, even with high pressure, try a heavier coil.
   
2. Rebound.
   There are a few ways to find the ideal rebound setting. One way is to start with fast rebound and work your way down until the bike feels stable. The problem with this, is that you may think the bike rides well, but you could be sacrificing traction without knowing it. You can also start in the middle, which is probably close to the ideal position, but this can leave you wondering which way to adjust it to get it just right. My suggestion is start slow and work you're way up. Slower rebound will result in better traction but run it too slow and the shock will pack down and ride harshly. Slower rebound will also help reduce inefficiency from pedal bob.
   
   *edit: Racing last weekend, I ran the compression damping wide open and slowed down the rebound for a fast, flat trail with small, infrequent bumps. The result was good compliance and more traction.
   
3.  Compression Damping.
   Compression speed should be proportional to rebound speed. Fast compression and slow rebound will make the fork pack down and handling will suffer. Similarly, slow compression and fast rebound produces a strange ride too. Best bet is to match the rebound speed. You'll know you have it right when pedal bob and brake dive are minimized. Manitou makes this nice and easy with the ABS+ knob.
   
4. Lockouts.
   Say 'no' to lockouts! I hear a lot of people say they want/like lockouts so that their bike will "climb like a hardtail/rigid". This is wrong. A properly tuned full suspension bike, with much better traction, will out-climb a hardtail. The exception to this is if you're sprinting up a paved hill, but we're talking about dirt in this post.
   
5. Tire Pressure.
   I might as well throw this in here too. With a full suspension bike, you might be able to get away with a little bit lower tire pressure. The biggest issue is cornering. You don't wont the tire rolling sideways; I find this is the limiting factor with low pressures. A little bit higher pressures can result in faster rolling with all the traction of properly tuned suspension.
   
6. Racing.
   In my opinion, a good trail day setup is exactly the same as race day setup. Partly because this is what you're used to, and partly because it should already be optimized for traction, efficiency, handling, and comfort. At the most you might want to turn up the compression damping, especially if it's a short sprint. Even then, I've found the reduced traction and bump absorption can throw off your handling expectations.
   
   Of course you may want to tweak the settings for different types of trails. Fast trails with small bumps require different settings than slower trails with bigger hits or fast trails with big hits. If you have the suspension set up properly for your home trails, it shouldn't be difficult to adjust it to another trail after a practice lap or two.
   
   Most rear shocks have multiple compression rates like forks. The Radium has firm and soft settings, no lockout. I always run it on the soft setting, but I'll reserve the firm setting for race courses with short steep climbs for a little extra power transfer out of the saddle.

One last thing. Most suspension setup guides I've read end here and imply that each adjustment is something to be tuned individually. But that's wrong. Spring pressure, rebound, and compression damping are all interrelated. Rebound and compression should be proportional to each other, and both are inversely proportional to spring pressure. For any rider, there's a small range that will work well for a specific trail. As you increase spring pressure, you should open up the compression damping to keep the fork moving and rebound should be adjusted to match. Similarly, as you decrease spring pressure, you should increase compression damping to keep the fork from blowing through the mid-stroke, and rebound should be slowed as well to keep things under control.

So that concludes Suspension Theory 101. I'll try to keep this post updated if/when my ideas change or expand.