This latest edition of the BST© Series (BrakeSteerTurn) article will focus on mountain bikes. Our very first endeavor into the mtb realm…
This article was prompted by a recent customer who came to the shop where I work. He brought his 2015 Santa Cruz Bantam in for some service and as we began the go over the bike we got to talking about its performance and setup. Here are 3 key tips to consider.
Turns out this was his his first year of riding and he had purchased the bike used. He rode the bike the entire season as-is. Meaning he relied on the previous owners setup without changing anything. He told me that at some trails, the bike was pretty good, solid feeling. But at other trails, especially as speeds increased it was too bouncy, a bit jarring and unpredictable over the bigger bumps.
Basic Suspension Setup
I went on to explain that initial sag and rebound settings were the absolute most important and critical settings to dial in and get right. He acknowledged he didn’t really have a good grasp on these attributes of a suspension type bike. I told him no worries, there is a wealth of reliable info out there and then pointed him to some selected sites and channels for setup advice. (Fox, Fork-Shock Sag and for the ultimate on suspensions, the Race Tech (Suspension Bible) For more detailed and technical information check out Vorsprung Suspension.
Meanwhile, I set an initial baseline sag of 24% front and 22% rear as well as a baseline rebound setting for him. I let him know that his ideal settings will vary depending on the trail and style of riding and that he should tweak his final settings after experimenting with slightly different setups. It is very important to understand that each rider is different and has a different riding style. Simply leaving sag at 25%-30% and never micro-adjusting it is counter-productive. Same goes for Compression and Rebound settings. Baseline settings are good for just that- to establish a Baseline.
While we will not go over the exact steps to set sag, it is vital to understand how important correct fork and shock ‘spring’ sag is to each particular rider. Now, even though an air damper has no coil spring, in essence the ‘air’ is the spring. Sag, is simply how much a bikes suspension compresses under the weight of a rider. Setting sag is basically determining a specific amount of ‘preload’ on the ‘spring’. Preload is the amount that the ‘Spring’ is compressed at rest or in full extension. Too little sag and the bike will usually feel very stiff and will not compress properly when it needs to, I.E. under braking and bump compliance. Too much sag and the bike will pitch and possibly compress too much fore and aft. The take away here is that proper suspension setup is very important to stability and cornering.
Tires and Pressures
The next topic we discussed was tire pressures. Now this is both a science and an art combined in one. There are so many types of tires and compounds and most are effected differently by pressure. Finding the correct pressure for a particular trail for a particular rider takes TIME. It takes patience. Unfortunately, most riders set the pressures and leave them for all of their riding. When the tires get a bit low, they just pump them back up to whatever their shop, a friend or website has suggested.
Does it work fairly okay? Most times it does. But are they taking advantage of their particular tire, bike and suspension? Their style of riding? No. So find a baseline, then experiment. Ultimately, tire pressures (whether tubed or tubeless) should be low enough to provide good grip for cornering and braking but not pinch against the rim or blowout. Yet stiff enough to provide the proper amount of stability, grip, feedback and bump compliance.
Lastly, we discussed body/riding position. Some and most riders tend to be “front-end” riders and a few some are “rear-end” riders. Most riders tend to be leaned forward and push the front end, hence front-end riding style. Body positioning is much more critical on a mountain bike than a road bike, therefore having a good baseline enables a rider to be able to micro-adjust her or his position while riding. MTB riding requires a rider to constantly be changing their body position in order to maximize speed, stability and grip. What is referred to as the; Rider Triangle. A riders hands, butt and feet, these are the three points of contact that provide feedback and determine the baseline body position.
Typically, shorter riders, 5′ 8″ and under benefit from flatter bars and a lower bar height I.E. (less stack spacing) this is so they are not in an unnatural position that has them tilted slightly rearward and consequently pulling on the bars which negatively affects cornering ability. Taller riders, 5’9″ and up may benefit from a riser type bar, so as not to have too much weight on the front end, have too much forward lean and subsequently having a hard time lifting the front end. Although these can be subtle nuances that may not even be visible, they do have an effect on the bikes handling as well as rider control. Seat fore/aft is another adjustment to be experimented with, in regard to cockpit length and control. Again, depending on riding style the position will vary on arm reach, maneuverability and rider comfort.
Finally to wrap it all up, remember that any suspension bike hardtail or full squish requires regular MAINTENANCE. Depending on how hard a rider rides, riding conditions, how much cleaning maintenance is done and brand of damper, service intervals can vary. But as a rule of thumb 75 hours give or take is about how much time before the front forks need a “Lower Leg Serving” (you’ll see intervals vary from 50 to 100 hours) This basic service of cleaning out the inner fork tubes, re-greasing, checking/changing stanchion wiper seals/foam rings and replacing the fork oil is paramount for fork performance and life span.
Service is usually not too difficult with the aid of most manufacture specs and video tutorials. If the bike has a rear shock it is usually around 50-60 odd hours before having to perform an “Air Sleeve Service”, which entails checking/replacing O-rings, washer seals and replacing the oil. But again, the time table will depend on the aforementioned variables.
The Take Away
A properly setup suspension will yield dividends for a rider, both in performance and riding enjoyment! Finding the recommended baseline and then further setting up the bike for a specific rider and riding style is the key to maximize the bikes designed and intended potential. We all know that a clean bike is happy bike… but a well setup bike
is also a very happy bike!