Velo Bike Shop

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Common Questions

How does a tubeless tire work? What do you do if you flat?

Tubeless tires and rims are similar to standard clincher types in all but a few details. Tubeless rims must be sealed where there are spoke holes and at the joint area and use a special valve stem with O-ring seals on either side. Most tubeless rim makers, like Shimano and Campagnolo, eliminate the rim's inner spoke holes completely, and thus the need for a rim strip. Stan's NoTubes makes a retrofit rim strip which converts conventional wheelsets to tubeless in conjunction with their latex-based sealant. Tubeless tires have an inner coating of rubber to seal the carcass (standard clincher tires are too porous to hold air for any length of time) and the reinforcing cords molded into the beads must be stronger to prevent the tire from blowing off of the rim when inflated at high pressures. At present, only Hutchinson makes tubeless tires for the road-under its own brand and for Specialized. Hutchinson's tubeless tires use a carbon fiber bead.

The way tubeless tires and rims inflate is that the rim and tire are designed to contact each other just tightly enough to make a reasonably airtight seal when the tire is loose on the rim and uninflated (automotive tires operate exactly like this). A quick burst of air pressure spreads the tire beads outwards towards the rim flanges. The inner rim profile is tapered to fit the tire beads more snugly as they spread outward, so once the tubeless tire is "started," easy hand pumping is all that is required to finish the job. When enough air pressure is achieved, the beads "pop" into place audibly and are sealed.

There are three strategies to fix a punctured tubeless tire. The first is to remove it exactly as you would a standard clincher: Unscrew the valve stem with finger pressure and then install a conventional tube -- this is the preferred method because it is a no-brainer. The second is to patch the inside of the tire carcass with a glueless patch from innovations in Cycling, and the third is to inject a one-once bottle of Stan's NoTubes into the tire (usually by removing the valve core and squeezing the fluid into the stem-- reinflate and go).

Why don't more riders use triples?

Triple cranksets provide a comfortably low gear range for climbing while retaining a closely spaced racing-type cogset to enhance riding on the flats and rollers. The alternative to a triple is a widely spaced cogset (12x28), which is still not low enough to make a huge improvement on excrutiatingly long climbs, and creates big jumps between gears -- which makes riding on the flats quite annoying.

Foolish pride is the main reason that most roadies will not resort to a triple chainring setup. Pro racers don't use triples, and they set the fashion for rank-and-file riders. We don't want to be seen riding a triple because it screams out that we are unwilling (or unable) to suffer profusely on climbs -- like the "real men" in the peloton. Another reason is that most rear derailleurs cannot handle the capacity (take up enough chain) of a three-ring crankset, nor can many front derailleurs swing wide enough to correctly shift three chainrings. Now that Shimano Dura-Ace and Campagnolo Record groups feature triples, that is a moot point.

How many tubes should I bring on a ride?

Two tubes is the perfect number. You'll need one to fix the only flat you'll get today, and you'll wave the second one at the jerk who never brings his own spares -- or only brought one and punctured a second time. Wave the tube, but never offer it -- the only thing you should leave an unprepared rider with is a memorable lesson. Also, many of us forget to repair or stow a punctured tube and bring it along for the next ride. Having a second is a god-send in such cases.

What things should I check before every ride?

Always check the quick-release levers. Open them a little less than half way, not so far that you mess with the wheel alignment, but enough so you can check that they close tightly. Next, check tire pressure so you will be able to trust your bike in the corners. I spin the wheels to check for brake drag, cuts in the tires and wiggly rims, quickly put the front tire in between my knees and twist the stem to ensure it is tight, and then squeeze the brake levers to ensure that the pads hit the rims at the right place. If I am using tubular tires (I almost always do), I grab the tire at a random point and roll it on the rim to ensure that it is securely glued, and then I ride.

How much air pressure should I run?

Every tire has a sweet spot where it rolls faster and yet absorbs road shock -- and more pressure is not always better, as many believe. Three features determine where this mythical tire pressure should be set. First, check the ratings on the tire. Some are rated as high as 220psi and others as low as 125psi -- usually there is a high/low range, and the best place to begin is the middle. Second is the diameter of the tire. Smaller-diameter tires (19mm) require significantly more pressure to support the same weight when compared with a larger-volume tire. 100psi may be more than ample for a 25mm casing while a 19mm TT tire will run almost flat at that pressure. Third is rider weight. All you need is sufficient air pressure to prevent unnecessary tire flex, and not so much that you bounce all over the road on rough pavement. Riders in the 200-pound range will discover that they can get a smooth, efficient ride at close to the tire's maximum rated pressure, while a 105-pound female or junior rider may achieve the same performance near the tire's minimum pressure rating.

Any time your bicycle bounces, you are trading horizontal momentum for upward acceleration that is never recovered. What makes a pneumatic tire efficient is that it deflects over objects it contacts without lifting the mass above it (you and your bike), and as it rolls over the object, it springs back and returns most of the energy it stored as it rolls over the back side of the object. This happens billions of times in a day's ride, so if you use the correct tire pressure, you can save gobs of energy in the form of better rolling resistance. Too much pressure will rob your strength -- especially if you are a lightweight rider. If you bicycle bounces, release five or ten ounces.

How many CO2 cartridges should I carry?

If you run tubeless tires, carry two, because you'll need one sometimes to get the tire bead reset and may have to use the second to pressurize the tire. If you are unsupported and competing in a road race, carry two -- use one to inflate the tire and the second as a backup in case you mess up the first try. All others should carry one cartridge and a tiny hand pump. I only use CO2 cartridges when I am in a time crunch -- like a race, a training ride or group situation where others are waiting for me to fix a flat. CO2 fillers are foolishly wasteful in an environmental sense (although they are recyclable), and a hand pump can refill a thousand tires without running out of air. Before you reach for that steel cartridge, consider a hand pump.

How often should I upgrade my helmet?

Replacing your helmet once a year is probably reasonable for a high-time cyclist (2,000 miles a month), and the rest of us should consider a replacement after two years. Crashing is a different story. The closed-cell foam that protects your head is a one-time deal; once it has been compressed, it will not dissipate the shock as well the next time. If you crash hard enough to scar the shell, you should buy a new helmet. Six seconds in the hospital emergency room costs more than the best helmet made -- don't sweat the price.

Do you put lube on your pedals?

NO. Modern pedals are equipped with sealed bearings and do not need regular maintenance. Theories that oiling your pedal's engagement areas will assist you in clicking free in the event of an emergency are fabricated by anxious Freds who should be on roller blades in Brazil. Dry pedals and cleats will release consistently at the same pressure. Spray-lube will cause them to release too easily and initially, and as the lubricant sloughs off or combines with dirt, the release pressure will become erratic as it firms up. Use mountain bike shoes and pedals for cyclocross, because, unlike plastic road cleats, their smaller, metal-to-metal interfaces release consistently in wet, muddy and dry conditions.

How many gels should I carry with me?

The rule of thumb is that 15 minutes before your start and every 45 minutes afterward is the minimum interval between food intake. Those who can't eat solid or gel-type foods while they are in motion use carbohydrate fluids in their water bottles. I prefer gels because there are times during a high-watt interval when my stomach can not handle anything but water, so I can continue to hydrate -- which is most important -- and eat later.

Do I need both water bottle cages?

Not necessarily. One water bottle contains about as much as an average body sweats in 45 minutes to an hour of cycling. Your body can store about an hour's worth of water, so a single bottle can get you safely through a two-hour ride before your body will enter the throes of dehydration. Two bottles are perfect for longer rides, or where you will be riding unsupported. Another reason to use two bottles is that you can put water in one and mix the other with an electrolyte/carbohydrate substance. Use each as needed, and the pure water can double as a cooling spray during hot weather.

What does compact mean? Why doesn't everyone ride it?

Tradition dictates most of cycling's trends, and standard, 53x39-tooth chainrings have been the choice of champions for almost 50 years. Compact cranksets use smaller-diameter chainrings (50x34 compared to 53x39). The theory is that compact cranksets are lighter weight, and when used in conjunction with an 11-tooth cassette cog, provide a lower climbing gear without sacrificing top speed (this assumes that we are comparing an 11x50 compact with standard 52x12-tooth gearing). SRAM Red takes full advantage of the wide gearing range of a compact system while Shimano Dura-Ace and Campagnolo Super Record maintain the 53x12 standard as their preferred gearing. Compact is best for most cyclists, although the advantage of running a 53x12 is that one always has the option of switching to an 11-tooth cassette for faster courses and time trialing. Compact riders are limited in that respect.

Road Bike Action Magazine

Looking for more information? Check out these articles:
Carbon Repairers have you Covered
Tips for Preventing Cramping
Crossing Train Tracks
Sewer Grates
Riding in the Rain
Road and Racing Tips
Cleat and Pedal Installation and Care
Safety Tips for Biking in Washington

Velo Bike Shop
Open 7 days a week
Sun: Noon–5pm
Mon–Thursday: 10am–7pm
Fri & Sat: 10am–6pm

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