Rider Question: What is the correct mountain bike tire pressure to run?
The art of setting your mountain bike tire pressure is one of the most important adjustments / tweaks you can perform for any ride.
Whether you’re a DJ, XC, AM, FR and/or DH* rider, racing or riding for sport, bicycle tire air pressure is the key to winning races, avoiding crashes, cleaning a technical hill climb, or ripping the descent.
*Mountain Bike Lingo: DJ = Dirt Jumping, XC = Cross Crountry, AM = All Mountain, FR = Free Ride & DH = Downhill
First things first. You need a high quality bicycle tire air pressure gauge. Here are some recommendations to check out that are good deals. Click the photos for more details:
Like any piece of bike equipment, they don’t last forever, and can loose calibration over time.
Tip: Consider purchasing two tire pressure gauges, so you can compare their accuracy against each other occasionally. Also if one breaks on you before a ride, you have a back up ready to go. I am a big fan of the simplicity of digital air gauges, but I still think a high-quality analog gauge may last longer if it undergoes extreme shock or crashes. Plus diigital gauges need batteries. This being said I would probably purchase a digital gauge for home, and an analog gauge for your pack.
Some quality bicycle air pumps have gauges as well. These air pumps work great in the garage, or at the bike trail head, but if you want to make a tweak on the ride they are useless. Plus their gauges go out of whack too overtime from use and abuse, so at least get one quality analog or digital tire pressure gauge to check against your garage bike pump’s gauge occasionally, and carry it in your pack.
Tip: Understand, even a half a pound of air can be the difference between avoiding a big wreck. While many riders get comfortable with squeezing the tire to guess at the correct psi when they don’t have a gauge, nothing can beat the accuracy of a gauge.
Tip: Proper MTB tire air pressure can extend the tire’s life.
Skimming the surface of the basics. A rider must first identify the actual maximum tire air pressure, or pressure range located on the side wall of the tire recommended by the manufacturer. If a rider is running tubes, the correct tube is imperative. Obviously if your running UST rims you might still consider a tube(s).
Tip: UST riders should consider at least carrying one Tube as a back up in case your Stan’s cannot save the day. If you flat a tire, while it is messy, yank the tire, install a tube, replace the tire, and ride on. Don’t let your Stans Tire Sealant supply run low, flatting is no fun.
Tip: For riders running, or considering Stan’s rim strips, only run UST tires. A UST tire has a much stronger side wall and the tires perform / handle much better, especially at lower pressure settings. Stans UST rim conversion kits work great, and you can upgrade to dedicated UST rims if you like the way UST tires feel, or run them indefinitely since you can run your rim both ways. For example if you ever decide you want a run a tire you like a lot that is not available in a UST model, pull your rim strips.
A general rule of thumb is that the higher you set a bicycle tire’s air pressure (not exceeding the maximum air pressure recommended) the faster a tire will roll on harder surfaces. This does not however mean a mountain bike rider will necessarily ride a trail / course faster. The affect of too much, or too little pressure air can cause traction loss depending upon the trail’s surface conditions the tire selected, and other factors.
Here are the reasons why tire air pressure will vary so considerably between riders and bike setup:
1 ) Trail type (i.e. downhill, rocky)
2 ) Trail surface condition (i.e. muddy)
3 ) Tire type (i.e. width, compound)
4 ) Bike type (i.e. full suspension, front suspension only or hard tail)
5 ) Rider weight plus gear
6 ) Suspension adjustment
7 ) Rider skill level / experience?
8 ) Proper equipment (i.e. a XC bike on a difficult FR trail)?
The ultimate goal is to set your MTB tire pressure where the tire provides the most traction, without flatting. This means you are going to have to test each tire you run until you establish where it works best for you.
Start closer to the maximum air pressure and test the tires out. Try decreasing 5 pounds of air out of each tire and test them again. How do they climb? How do they corner? Try another 3-5 pounds decrease and try them again. Often times as you lower the air pressure, the tires begin to hook up much better, but the danger is as you reduce pressure you risk flatting or even denting the rim. If your hitting the rim or flatting often, you need to increase air pressure. Slowly increase 1-2 pounds in the appropriate direction for fine tuning.
Technique #1: The correct mountain bike tire selection is the key to traction through proper air pressure adjustment. (Upgrade your tires to the type of terrain your running)
Consider the type of compound a tire is constructed of, its weight, width and type of terrain it was designed for. The key to finding tires that works best for your bike and riding style, is simply to try several until you find the tires that hook up the best.
Technique #2: Most riders prefer 2-4 pounds more air pressure in their rear tire, then in their front MTB tire. (i.e. front 32 pounds / rear 35 pounds) This applies to riders running either the same width front and rear tires, or a wider tire in the rear. Riders who opt to run a wider tire in the front most likely will follow this rule as well.
Technique #3: Heavier weight riders / more aggressive bicycle riders generally require higher tire psi as they carry more speed / compress the tire more. This excludes those who are running heavy duty tubes and dedicated DH tires, but there is a limit. Exceed the limit and rim damage can occur. Skirt the limit and traction loss / increased rolling resistance become evident. While UST rims also allow for lower pressure , the same rule applies.
Techniqe #4: Unless your racing you can adjust your tire pressure during the ride, but that doesn’t always mean you will be able to when you rallying with other riders. Most riders select a bicycle tire pressure that works best for the majority of the ride, but not always. If 70% of a dry dirt trail is hard pack flats and 30% technical rocky hill climbing, a rider must decide which air pressure makes the most sense. If you run the tires at high pressure, a rider will most likely gain speed through the flats, but may loose traction during the climbs, as the tire tends to bounce more off the rocks. Some compensation can be made on the climbs if the rider can push harder gears and maintain faster speed. This of course requires better physical condition and a higher skill level. In the end the rider alone must decide which part of the trail the tire should work best for.
Technique #5: Temperature effects air pressure. Hot air expands, and cold air contracts. Thus on a hot day, your tire air pressure will increase. Just like on a cold day your tire pressure can decrease. Consider this when setting your pressure as you become more experienced with the art of setting air pressure.
Technique #6: Two cyclists’ brains are better than one. Exchange data with fellow riders.
Technique #7: Several pounds of air can be lost when you remove the bike pump. Add a bit more than you want, and then bleed the air down with your gauge.