Flat tires will happen…
Avoiding flat tires is just one more reason to avoid riding in the gutter at the edge of the road, where debris accumulates. CyclingSavvy lane-positioning strategy prevents flat tires while it improves your interactions with other road users. Is that thought new to you? Check out our online materials and course offerings!
Still, if you ride a bike, the question is not “if” but “when” a flat tire will interrupt your ride.
Repairing a flat tire on a standard bike with clincher tires and tubes is straightforward, and a just little more complicated if you are running tubeless tires. Flats can usually be repaired with a hand pump, tire levers, and a spare tube. Detailed instructions are here.
But – if your ride is an e-bike, repairing a flat tire can get more complicated, so let’s discuss this.
A mid-drive e-bike has the motor centrally located near the cranks and pedals. Aside from the weight of the bike and motor, repairing a flat on a mid-drive e-bike is not too difficult, because the wheels are like those on most bikes.
Not so with a hub-drive model. A hub-drive e-bike has a very large front or rear hub that houses the drive motor (left illustration).18- to 22 mm hex nuts secure the axle. Wheels with hub-drive motors are quite heavy, so much that many bike shops which service e-bikes have powered bike stands to lift a bike off the ground. Some e-bikes tip the scales at more than 70 pounds! Unless you have a way to lift the bike and the large, rather heavy wrench for the large nuts that hold the wheel in place, you can’t remove the wheel to replace the inner tube.
A bike shop will always replace the inner tube, so it can guarantee its work. You might plan to walk or call Uber to get home. But wait! It is possible to lay many bikes down and patch the inner tube without removing the wheel. Instructions on exposing and reinstalling the inner tube are here. This is more cumbersome than working on a wheel you have removed from the bike, but it can fix the flat tire and get you rolling again. This trick is not practical on e-bikes with 20″ fat tires.
An ounce of prevention is worth a pound of cure, as the saying goes.
Prevention is the key
While no countermeasure is 100% effective, there are several ways to prevent flats through equipment choices and maintenance.
Inspect Before Every Ride
I tell participants in my CyclingSavvy classes to remember the ABCs: Air, Brakes, Chain/cranks/cassette. All tires have the tire pressure range marked on the sidewall. Do not ride if the tire pressures are below the minimum setting. Check air pressure before every ride, at least with a thumb-and-finger squeeze.
It is normal for air to seep out slowly through rubber. Top up pressure weekly with a pump that has a pressure gauge. If the tire pressure is low, the tube can bottom out on the rim, causing a pinch flat — also called a snakebite flat, because it leaves a pair of holes in the inner tube. Low pressure also can rotate the tire and tube under acceleration and rip the valve from the tube.
Check tires for any bulges, tears, or signs of excess wear such as threads showing through the tread area. Replace worn or damaged tires. Many tires have wear indicators. Replace tires when the wear indicators are no longer present.
Sealants in Inner Tubes
Tire sealants are thick liquids reinforced with solid materials that clog up a hole. Some sealants can be injected into an inner tube through the valve, or are pre‑installed in new tubes, and claim to repair holes to 3.0mm (about 1/8”). Use only a sealant intended for use in inner tubes. We have seen positive results with sealants for very small punctures from thin glass shards and thorns. If the object that caused the puncture is still embedded in the tire, you must remove it. If not, it will enlarge the hole in the tube with every turn of the wheel.
Some tires have a layer of Kevlar fabric under the tread. Several companies market liners that fit between the tire and the tube. Some liners are Kevlar-reinforced, some are heavy plastic strips, while a new style of liner is made from a multi-cell foam 15mm (about 5/8”) thick in the center section.
I have seen very good results with the multi-cell foam liners. The manufacturer claims that they prevent about 90% of flat tires. But no tire liner will prevent a puncture from a 2” nail.
These liners are pricey. Installing of a multi-cell foam liner in a 20x 4.0 fatbike tire on the drive wheel can cost nearly $150. Yet, that is about the price for repairing one flat tire on the drive wheel (parts and labor) at most shops. So, if the liner prevented one flat tire, it has paid for itself.
“Thornproof ” inner tubes are another option, with thicker rubber under the tire tread.
Any of these options increases rolling resistance — but that is not a major issue with an e-bike.
Tubeless, flat tire resistant
Some tires and wheels can go tubeless. Tubeless technology for mountain bikes has been around for just over 20 years. As a mountain bike racer, I have used tubeless tires since their introduction. In 20 years, I have only had two flats with tubeless tires, caused by a catastrophic tear in the sidewall when I ran over a partly buried section of metal fence post.
Tubeless tires are made flat-resistant with sealant. I use a “Race” sealant that will repair holes to 7mm (about ¼”). Many sealants will seal holes to 4mm. Most sealants dry out, so you need to top them off at least every 4-6 months; even more regularly in hotter climates.
Tires should be classified as UST (Universal Standard Tubeless) or TR (Tubeless Ready). Rims need to be either tubeless-compliant with no spoke holes and a smooth inner rim surface, or converted to tubeless using an approved rim-sealing tape.
If a tubeless tire does get a flat, and adding sealant doesn’t work, then a tube must be installed.
In recent years, tires for general use on paved and gravel surfaces have trended wider. Research has shown them to roll as easily as narrow tires, under real-world conditions. Wider tires give a more comfortable ride, with lower air pressure, and can run tubeless. Tubeless doesn’t make sense at least yet for narrow, hard-inflated road tires: an overinflated tubeless tire is more likely to blow off the rim. — dangerous, and the sealant makes a real mess..Here’s some good general information on choices.
There are tubeless 26 x 4.0” fatbike tires and some 26” fatbike rims. There are tubeless 20 x 4.0″ tires, but I am unaware of any wide 20” rims that can be converted to tubeless. Check with your bike shop.
One more thing…
You may want to do a roadside flat-tire repair if you have a small e-bike with 12.5″ tires and a hub drive motor. Before you do, check to see whether the drive-motor power cord can be disconnected. There is usually a connector somewhere near the drive motor. We have seen several inexpensive small and folding e-bikes that have drive motors wired directly into the battery box or control module. This complicates on-road repairs greatly and may even prevent a tire repair altogether when you need to replace the tube during a ride.
ABEA welcomes e-bike riders in CyclingSavvy courses, but we don’t have the equipment to remove and replace a hub-drive e-bike wheel on the road. Please come to class with your equipment, and tires in good condition. This applies not only to e-bikes, but for all riders. Remember the ABCs!