from Rookie’s keyboard,
Hello, friends
The other day I decided to try a new commute path. You have to try new things in life, right? Otherwise, you risk staying the same for way too long.
Well, sometimes those new things aren’t all that exciting.
A large section of my new route ended up being crushed limestone – something that my road bike did not like all that much. And when my road bike doesn’t like something, I don’t like it either.
Some of you may be unfamiliar with that term, to begin with. So here’s a little basic info:
Crushed limestone is made by breaking mining limestone or dolomite rock deposits with the help of rock-crushing machines. Once the stones are broken down, they’re filtered by size.
Crushed limestone has many uses such as:
- Road base
- Railroad ballast
- Backfill retaining walls
…etc.
The properties of crushed limestone make it a frequently used material for road construction. Therefore, the chances of stumbling on a crushed limestone road when riding a bike outside of a city are relatively high, especially if you make a detour and switch to smaller roads.
Why I Don’t Like Limestone Roads
Punctures
There are three main ways to get a flat tire:
- Pinch flat. The inner tube is pressed against the rim when the wheel comes in contact with the edge of an object at a high speed.
- Puncture. An external object pierces the outer tire and then the inner tube.
- Internal flat. A spoke eyelet, a nipple or a spoke pierces the inner tube. The usual causes of an internal flat are excessively long spokes, poorly tensioned spokes, or the absence of a protective rim tape.
Road bikes are a lot more likely to experience pinch and puncture flats than bicycles with fatter tires for the following reasons:
- Thinness. Road bike tires are lighter and thus thinner. This is especially true for the so-called competition tires.
Competition tires are so thin that flats are a very common occurrence even when riding on regular paved roads.
For that reason, it’s highly advisable not to use a competition tire on crushed limestone. If you do, a flat or a series of flats is practically guaranteed.
Conversely, MTB tires are heavier, thicker and more puncture-resistant to match the style of riding and the terrain that MTBs are used on.
- High air pressure
Road bike tires operate at 2-4 times higher air pressure than MTB tires. The high air pressure makes the tires firm and improves their rolling resistance. As a result, it takes less effort to pedal and reach higher speeds.
The high air pressure is beneficial to puncture resistance too. The higher the air pressure, the harder it is to get a pinch flat (regardless of the bike tire).
Also, the higher air pressure makes it more difficult for an external object to pierce the tire thanks to the extra firmness.
However, the high air pressure also prevents the tire from deforming upon meeting an object. As a result, the stress isn’t spread over a larger contact area, and a sharp object can penetrate the tire.
Crushed limestone is made of small stones which have multiple sharp edges. This greatly increases the chances of getting a flat.
The recommended measures to reduce this outcome are:
1. Run the widest possible tires that your frame and fork can operate with while still having a sufficient amount of clearance.
If you have a newer bike, you will more than likely be limited to tires between 25 and 32mm. If you have an older road bike from the late 70s, for example, you may fit even 35mm tires.
Wider tires are not only more resistant to punctures, but they can also operate at lower air pressure and will thus provide more comfort.
That said, it’s possible to ride on crushed limestone even with 23-25mm tires. However, the ride will be quite harsh due to the high air pressure.
2. Make sure that the tires have extra puncture resistance. Puncture-resistant models will be heavier than regular ones but the weight penalty is worth it. At the end of the day, it doesn’t matter how fast a bike allegedly is if you spent most of the day on the side of the road playing with tire levers and patches.
3. Use the appropriate air pressure. If you’re unsure go with the higher setting. It’s better to have more air in the tires than not enough. As mentioned, the extra air protects from pinch flats and pushes away external objects.
Frame and Fork Protection
When riding on crushed limestone, the tires will be throwing small stones and debris at the frame and fork persistently. The stones will damage the paint whereas the small debris will make the drivetrain gritty.
Below is a list of tips meant to exercise some damage control:
- Enough clearance
Make sure that the fork and frame offer at least a few millimeters of clearance. Otherwise, small stones may get stuck between the tire and the frame/fork. When that happens the tire will push through and scratch the frame/fork with the stone. In extreme cases, the wheel may even seize and cause an accident.
- Frame protection
Frame protection represents a thin folio that acts as another outer layer. (It’s frequently) installed on mountain bikes.
It’s a good idea to put frame protection on the downtube, chainstays and the rear of the seat tube.
- Full Fenders
Full fenders will stop a lot of the dirt and rocks thrown by the tires. That said, most road bikes do not have the clearance for full fenders, especially if you upgrade the tires to wider ones.
Fenders help only when they encompass the entire wheel. The two most impart sections are the area between the fork and the rider as well as the one between the rear tire and the seat tube. Clip-on fenders are partial and do nothing for those sections.
- Crank Protection
The crank area near the bottom bracket can also be easily damaged by small tones and occasional contact with the ground. Hence why mountain bikes use crank protectors. To protect your cranks, you may consider a pair.
- Gear Ratio
The rolling resistance on gravel and limestone is higher. Thus, you may find the current gears on your road bike too high to maintain a decent cadence. If that’s the case, you may consider adding a cassette/freewheel with a larger rear cog and/or using a smaller chainring at the front.
Until next time,
Rookie
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