Let's think about tire choices. I love talking about bike set-up. I have a background in several different sports at a high level where equipment set-up was a big part of success; so this is something I think about a lot and as a result spend time tinkering with my bike setup and tires. I have also won my two biggest mountain bike races mostly because I made a risky choice with tires and it paid off. I don’t have a tire sponsor either, so I can use a lot of different tires, and I do; probably about 20 tires (10 sets) a year.
Let’s talk tire choice in a multiple step process:
- Know your riding style and ability
- Think about how the race will be won
- Pick your risk position
- Pick your tread
- Put the right air pressure in the tire
So Step 1: Know your riding style and ability. This one is huge and I see people make strange choices with this considered. So what are the factors here? I think the biggest is your ability and desire to control a bike while it is loose in the corners. The fast guys tires are getting a little loose regularly. If you like your bike to feel like it is on rails, then you are going to need more tread than others. The key here is to know what too little tire feels like for you and for that you need to try out different tires. No one can do this for you, what is good for someone else has basically no bearing on what is good for you. The second part here is how light you are on the bike, if you are light (figuratively and actually) on the bike you’ll be able to pick a lighter tire and have less of a chance of a flat.
Step 2: How is the winner going to win? This is so damn important to winning bike races; you need to have a strategy to win (or beat guys you don’t usually finish in front of) or you aren’t optimizing your set-up. So the options here are: will light tires allow you to stay with the lead group longer and make big gains from riding in a group? Or does the race head straight into single-track that is going to require more traction through a bunch of turns. Maybe the opening miles aren’t selective and you are fit relative to your competitors, so a heavier tire will allow you to let the bike free on the descents. The key here is to have a plan and then set-up your preparation to maximize that plan… then go race and see how it all works out!
Step 3: Pick your risk position. If you are just looking to finish a long endurance race or you are totally unfamiliar with the course and your completion, don’t worry about your tires. Pick something tried and true with decent sidewall protection. This is also good advice for training races where you don’t want to screw up your day with too light (or too worn out!) tire choice. Step 4 will have some ideas for you, but the key is not to overthink it. Likewise, big races with big goals require careful consideration about where you might finish with and without having to repair a flat.
Step 4: Pick your tread. First, your tread needs to match the course. You don’t want to be floating on your tread; you want the tread to dig into the dirt. If you are running a trail tire (like the Ardent) on a super hard packed XC course – like 80% of endurance mountain bike racing, you might be floating on the knobs and not digging in. This obviously is also a function of rider weight and tire pressure. The take away here is that the depth of the tire knobs needs to match the depth of the loose dirt on the trail.
Second, you need actual data and you can’t go on feel when it comes to fast tires. Low tread, light tires ALWAYS feel fast, here is where Strava can be helpful, because you can compare actual segment times. You will be surprised how when riding a fast tire and super loose you feel like are going so damn fast, but the segment times tell a different story.
Third, there are some engineering geeks out there that are kicking out some interesting tire drag data. I don’t think data is the end-all-be-all, but it helps you consider more about a tire then the grams.
Step 5: Put the right air pressure in the tire. This one can be tricky and I’ve been guilty of running too much pressure and it has cost me dearly on tricky climbs. Like risk position, this decision is about finding a sweet spot on the continuum. Lower tire pressure smoothes out the ride and helps with traction, but you increase your chance of flats. It’s also important to remember that tire pressure is definitely a function of tire volume and rider weight. Many lightweight tires are lower volume and need more pressure to suck up the hits without banging up the rim. Also consider the drag data I mentioned earlier, every psi below 30 increases rolling resistance a decent amount; all psi above 30, not much gains. Finally, remember that the faster you run into things, the more pressure you need, so as you move through the field and become a faster rider, you are probably going to need to increase your tire pressure. One personal note here, I usually put a little more pressure then I need in my tires and let the “right amount” of air out in my warm-up. This technique has bit me at a few 100-mile events when I had too much air in the tires at the first technical rooty climb that demanded lower pressure to maintain traction, so I had to get off and let some out.
All in all, careful choices must be made based on your ability, race course, tactics, and tire pressures. Don't simply use whatever tires came on your bike. That is simply not an approach that will get you on the podium. Neither is using whatever your buddy uses. Analyze your riding style and comfort against the risks you plan to take on race day, and use that info to make an informed and calculated decision on which tire and what pressure you should run.