The Kid Casino

Suspension Set-up: The basics

Whether you are a road rider or a racer correct suspension setup is the key to fast smooth riding and consistent lap times. To get the best out of your bike it needs to be set up for the conditions in which you will be riding. It is considerably easier to set the bike up for the Track as you know what conditions will be like for the next hour or so and thus you can dial in the optimum settings for the that particular situation.

To what extent you change your suspension settings will depend on whether your bike will also have to cope with riding on the road. Unlike Roads Tracks are generally smooth and grippy. So if you are only going to use the bike on the track you have the luxury of fitting harder springs and modifying the fork and shock internals. If you ride on the road as well as the track you will probably want to keep a certain comfort level and concentrate on just optimizing the current equipment

With incorrect suspension setup, tire wear is increased and handling suffers, which in turn can result in rider fatigue. Lap times can be dramatically slower and in extreme cases safety can be compromised. Hopefully the following guide will help you dial in your suspension for faster and safer riding both on and off the track.

Firstly you will need to check the Fork and Shock sag: this is the amount the forks and rear shock settle under load. To measure it do the following: push down on the forks a number of times to settle them, then mark the stanchion with a felt pen or put a cable tie where the dust seal is sitting. Next ask some for help to lift on the bars so the front wheel is just off the ground and measure the amount the forks have traveled down. This is the static sag (or unladen sag), This can be changed by adjusting the spring preload (more preload = less sag). Repeat the same process for the rear, this time measuring the distance from the wheel spindle to a fixed point on the tail. Now you are ready to begin setting up your suspension. The key is to do it a little at a time and make notes as you go. For road riding start with the wet track settings and work from there.

Basic Setup: Check the following

Forks sag 18-22 mm for dry track, 23-27mm for rain.

Shock sag 8-10mm for dry track, 10-14mm for rain.

Check chain alignment. If not correct, bike will crab walk and sprocket wear will be increased.

Proper tire balance and pressure, starting with 30psi front and 32psi rear (both dry and wet).

Steering head bearings and torque specifications - if too loose, there will be head shake at high speeds.

Front-end alignment. Check wheel alignment with triple clamps. If out of alignment, fork geometry will be incorrect and steering will suffer.

Crash damage, check for proper frame geometry.

Stock Suspension Tuning Limitations

Manufacturers plan on designing a bike that works moderately well for a large section of riders and usages. To accomplish this as economically as possible, they use valving with very small venturis. These are then matched to a very basic shim stack which creates a damping curve for the given suspension component. At slower speeds this design can work moderately well, but at higher speeds, when the suspension must react more quickly, the suspension will not flow enough oil, and will experience hydraulic lock. With hydraulic lock, the fork and/or shock cannot dampen correctly and handling suffers. The solution is to re-valve the active components to gain a proper damping curve. It does not matter what components you have, (Ohlins, Fox, Kayaba, Showa) matching them to your intended use and weight will vastly improve their action. Furthermore, if you can achieve the damping curve that is needed, it does not matter what brand name is on the component. Often with stock components, when you turn the adjusters full in or out, you do not notice a difference. In part, this is due to the fact that the manufacturer has put the damping curve in an area outside of your ideal range. Also, because the valves have such small venturis, the adjuster change makes very little difference. After re-valving, the adjusters will be brought into play, and when you make an adjustment, you will be able to notice that it affects the way the way the fork or shock performs.

Another problem with stock suspension is the springs that are used. Often they are progressive, increasing the spring rate with increased compression distance. This means that the valving is correct for only one part of the spring’s travel, all other is compromise. If the factory does install a straight-rate spring, it is rarely the correct rate for the weight of the rider with gear. The solution is to install a straight-rate spring that matches the valving for the combined weight of the bike, rider and gear to the type of riding intended.

Remember!

• Always make small adjustments, more is not always better.

• Always keep notes of what you have done.

• Suspension tuning is an art - be patient

Mark Thompson has spent the last 20 Years Racing motorcycles and managing Race Teams. He now runs the Trackbikes website.

Pocket bikes are miniature motorcycles — powered, for the most part, by oil- and gas-burning engines similar to those used in chain saws, weed whackers or other small motorized tools — and they look just like the real thing.

The snazziest models cost thousands and are made in Italy, but the ones that are selling by the container load run from $200 to $500. They come from China, among other places, and are getting snapped up by eager teenagers and, in some cases, not-so-teenagers.

At Broadtek LLC, a South San Francisco firm that imports them, the cardboard cartons containing the small bikes are stacked to the ceiling of a tall warehouse and are quickly going out the door to eager customers.

In Walnut Creek, Eric Rahin, owner of Sonic Scooterz, says he’s selling them in droves — “from college students to people in their late 50s. It’s basically a toy to have some fun with.”

Manufacturers say the bikes are supposed to be used only on closed race tracks, private roads or any other place where there are no public traffic laws and, more important, no big cars or trucks to run into you. Many buyers follow that advice.

But now you see some of these new pocket bikes zinging in and out of parking lots, up and down residential streets and, occasionally into the side of a car. And therein lies the rub.

“It’s very difficult for a driver (of a car) to see one on those bikes, because of their low height,” said San Francisco police Lt. Kitt Crenshaw. “We’ve had several accidents in the last few weeks, and people went to the hospital.”

The pocket bikes have a top speed of about 35 mph, but can be souped up to go faster. They evolved from tiny but highly sophisticated racing bikes that campaign on European race tracks and are sometimes used as training vehicles for Grand Prix motorcycle racers.

The bikes are faithful imitations of popular normal-size street motorcycles, which, for marketing reasons, are faithful imitations of pure race bikes, down to the disk brakes, handlebars, chain drives, twist-grip throttles and electronic ignition.

The little bikes weigh about 50 pounds, stand about a foot and a half high and can easily be put in the trunk of a car. They have tiny engines — 47cc or 49cc displacement, less than 1/20th the size of a big motorcycle. And they are enticing.

“It’s a fun little thing to ride,” said Matt Damon, a 21-year-old salesman in a Martinez pet store. “It’s a whole lot cheaper than a $6,000 or $7,000 big bike. For years now, I’ve been riding different types of motorcycles, but it’s more like the small bikes are a fun thing, instead of just transportation. And it’s easier to maintain and burns less gas.”

But Damon did admit, “I took it for a ride down the street and got pulled over. The officer was kind of nice about it. But I got a ticket.”

Police departments in the Bay Area and elsewhere in California have been cracking down on the little two-wheelers, saying they are a major accident waiting to happen. No police agency could come up with information about any deaths caused by pocket bike crashes, but police want them off the public roads before the inevitable happens.

“Their numbers are starting to increase,” said Milpitas police Officer Jay Johnson, who was assigned by his department to look into the phenomenon and ultimately write about it for the weekly Milpitas Post. “Most of the complaints we’re getting is that drivers can’t see them or there’ll be a group of them racing, or they’re running stop signs.”

For a while, though, until Johnson began studying up on the subject, and the California Highway Patrol sent out a memo clarifying just what is and what is not legal about the bikes, confusion seemed to be paramount.

In fact, it shouldn’t be. On many bikes, there’s a decal right there on the gas tank that says these things do not conform to “federal motor vehicle safety standards.”

After a lengthy consult with the state Vehicle Code and the Department of Motor Vehicles, the CHP explained that the bikes do not meet a number of standards required for all vehicles registered in California — the most telling example being the stipulation that “headlamp height (be) between 22 and 54 inches.”

Technical problems aside, it’s the safety issue that concerns authorities.

“We’re really concerned about these things mixing with traffic,” said CHP spokesman Steve Kohler. “If you think about it, something that small is difficult to see, when it’s mixed in with cars, trucks and buses. Drivers don’t even see full-size motorcycles. There’s no way they’re going to see these things.”

Or, as David Edwards, editor in chief of Cycle World Magazine and a man who puts about 20,000 miles a year on motorcycles, said: “When you get out in city traffic, you’ll be at more risk than on a full-size motorcycle. But they only hold (a little) gas, so you won’t go too far. And they’re noisy as hell, so at least people will hear you coming if not see you coming.”

- Michael Taylor, Chronicle Staff Writer
Wednesday, June 16, 2004