Gravel Tires

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Hi, we are back with our second installment on the subject of Gravel Cycling to talk about all things rubber – the tires we use and how they might differ from what you might be used to in the paved realm. Three tire characteristics will govern the quality of your gravel experience, all of which we need to get right: Tire width, tire tread and air pressure.

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If you are riding a standard road bike you are probably on tires ranging from 23mm to 28mm in width. If you have ever had to navigate gravel on 23mm tires you understood the importance of width as those skinny hoops tried to keep you upright ploughing a wobbly groove in the road. Floating on the top beats carving grooves through the gravel. While opinions on tire width vary, most gravel riders would agree 32mm is the minimum width that will keep you on top of the gravel. Go for tires that will keep you comfortable and safe, keeping in mind the maximum width tire you can put on your bike is limited by the clearances in the frame and fork.

                                                                 Fat is fast - go as wide as you can

                                                                Fat is fast - go as wide as you can

There are two main things we need to understand about air pressure, the first is the relationship between air pressure and rolling resistance. If you are used to running something like 25mm tires on the road you have probably been pumping them up to 100 pounds or more of pressure. This is in line with what used to be the prevailing wisdom that higher air pressure equated to lower rolling resistance and hence faster speed. More recent data from both lab and road testing have proven this old wisdom mostly wrong. We will spare you all the details and condense the findings to this: High pressure causes tires to bounce over bumps, converting hard earned horizontal motion into wasted vertical motion and transmitting road harshness into the rider's body leading to fatigue. Low pressure allows the tire to deform on the bumps, absorbing the shock conserving energy and your body. High pressure is good on perfectly smooth roads, but an impediment everywhere else. Our local paved roads tend to fall into that everywhere else category, and out in the gravel world things get even rougher.  

How much pressure you need is governed by the relationship between pressure and volume. As tires get larger they hold a larger volume of air and require less air pressure to safely support the weight of bike and rider. In 23mm tires, you need 100psi or more to prevent pinch flats resulting from the rubber from getting pinched between road and rim on bumps.  

                                                  Pinch flat in the making

                                                 Pinch flat in the making

In a wider tire, say 40mm, 60psi might provide the protection, and have the same feel of firmness as the 100psi in the 23mm tire. If you put this information together with what we said about rolling resistance above, you will see that we don’t need to ride on hard firm tires; we want our tires to be soft to absorb the bumps. The good news here is that with the added volume provided by wide tires, there is plenty of buffer between rim and road for you to ride at surprisingly low pressures. When width and pressure are right, we can be Fat and Fast. The actual pressure you ride at will depend on several factors like rider weight, the relative gnarliness of the roads, and how much road vibration you want to tolerate. One guideline that might be helpful: if you feel like you’re running a jack-hammer while cruising the gravel, you have too much air in your tires. After mounting new tires, I find it helpful to take a gauge and pump out on the road and experiment.

                  Precision Gauges can be a big help

                 Precision Gauges can be a big help

We mentioned pinch flats above, and one of the challenges common to both mountain biking and gravel biking is finding the point where pressure is low enough to smooth out the bumps, but high enough to avoid the pinch flat. Tubeless tires, now standard in mountain biking, takes the pinch flat out the equation - there is no tube to pinch, and hence no flat. The tubeless set-up requires tires and rims specifically designated as "tubeless" and a liquid sealant that rides inside the mounted tire. The sealant is formulated to ooze out through any puncture holes in the tire and congeal to stop the leakage of air. It's not uncommon to ride an entire season with punctures in a tire without ever finding out about it until you take the tire off and examine it. 

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Finally, the topic of tread. Simply put, you probably need less tread for gravel than you think you do. Traction, or grip, is dependent on the amount of rubber that actually meets the riding surface. The deep tread knobs typical on mountain bike tires can find traction in sand, loose dirt or muddy conditions because the tread sinks in and gets surrounded by the surface material. Gravel behaves differently - the same deep tread typically provides no advantage in gravel. The most contact on gravel is provided by smooth, supple tires that can deform around the individual gravel chunks.

                                                                This may be all the tread you need...

                                                               This may be all the tread you need...

Some riders will choose to ride tires with deeper tread patterns for added traction based on their local gravel characteristics, which may include sandy or wet road conditions. In some places, the Flint Hills of Kansas for example, the roads are covered with very hard sharp flint chips which can be deadly to thin-skinned tires.

                                         ...or this may be the tread you need

                                        ...or this may be the tread you need

A final word: everyone with experience in the gravel has opinions on what works best in choosing tires, tread and pressure, and we are no different. Talk to other riders, do your research, but most of all, get out there on the road and find out what works for you. When you come back wearing a smile, you'll know you're getting it right.

                                                            These guys got it right

                                                           These guys got it right

Come back next week, for a discussion on the bikes we love – the All-Road Bikes.

At FBC the owner and staff have a passion for cycling – we all ride to help you ride better. Come and see us in Freeport at 120 South Chicago in Freeport to find out how we can help you get full enjoyment out of your cycling experience.

Intro to gravel cycling

Part 1 - Why Gravel?

 They're happy - they found some nice gravel

They're happy - they found some nice gravel

If you haven’t been totally daydreaming while cruising your bike down the usual tarmac roads in the last couple years, you have noticed a significant movement of cyclists off the pavement and on to the gravel roads.  It isn’t just us; gravel riding has emerged globally as a new and growing genre in the world of cycling.  In the shop, we often get asked what is it that attracts people to ride gravel roads, especially here in Northwest Illinois where our paved rural roads are so perfect for riding.  People have many questions about gravel cycling, but the first is always: “why?”.

 So guys, why are we doing this anyway?

So guys, why are we doing this anyway?

1.  Gravel changes the scenery. Admit it – you’ve ridden the same pavement to the same places hundreds of times, and unless you are willing to put your bike on the car and go somewhere else, you’re going to ride them hundreds more.  Gravel roads offer an easy way to see the places you haven’t seen, and take you places you haven’t been.

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2.  Gravel changes the game. After years of honing your bike handling skills on solid roads, the shake and shimmy of gravel challenge those skills in a way that makes you focus more on how you actually handle your bike. This new challenge to your skill on the bike elevates the ride into a new level of engagement.  The impetus behind the mountain bike boom of the ‘80s and ‘90s was much the same: it’s more exciting.

 Sign says "Things are about to get exciting"

Sign says "Things are about to get exciting"

3.  Gravel has less traffic, way less than paved roads.  While we’re not afraid of a little traffic, the quiet of the un-beaten path is relaxing.

 CAR BACK!! Yeah, waaaay back

CAR BACK!! Yeah, waaaay back

4.  Gravel is great in the Winter. While paved roads get salted and sanded into sloppy messes following winter storms, gravel roads get only the plow. As a result, winter gravel roads tend to be firm, dry and a little crunchy with a thin layer of gravel that gets scraped to the top providing a good grippy surface.

 Solid grippiness

Solid grippiness

5.  Gravel is great for training. Depending on conditions, gravel generally creates more rolling resistance than smooth pavement. A ride on gravel will usually take more effort, or if you prefer, burn more calories than a ride of equal distance on pavement. Additionally, most gravel roads were built without much effort put into reshaping the land, meaning that the hills can be steeper and more frequent than their paved cousins. For the cyclist, gravel sometimes becomes a bit of interval training – always good, whether you think you need it or not.

 Sometimes the gnar makes it a lot harder

Sometimes the gnar makes it a lot harder

Join us again next week for part 2 – Tires and air pressure

At FBC the owner and staff have a passion for cycling – we all ride to help you ride better. Come and see us in Freeport at 120 South Chicago in Freeport to find out how we can help you get full enjoyment out of your cycling experience.

FrostbitE 40 recon

Oh man was I in need of a good ride! Life has been busy lately, stress has been high, my life has been out of balance. What I needed was a nice long ride with some good pals. I sent out a few texts and wham-o we were all set to ride Saturday morning.

With the Frostbite 40 coming up we decided to ride a route I thought would be a good option. Everyone came from different directions so it worked out perfect to meet in Pecatonica.

Temps were perfect, 20's and cloudy, with a 100% chance of awesome. The roads were frozen but some recent warm weather created some ruts in the road which caused a minor accident. We addressed some issues and pressed on. A couple miles later we rolled into Rock City to clean out some cuts and grab a PBR and snack.

When we left Rock City the sun came out and on we rolled. I love steel bridges on gravel roads so we took a route through Epplyana where one of these bridges are located.

A few more big climbs and then it was smooth sailing back to town. I think this is going to be an excellent course for the Frostbite 40. I might make a couple changes but we all seemed to agree it's got some good flavor.

Rolling back to the start with just a few miles left our spirits were high, and I was super grateful to have such good like minded friends to share the miles with. The weather was great, the route was great, but having good riding pals is what makes days like today one you don't forget.