Extended tire lifeI am told that tire warmers help prolong the life of a tire (a DOT tire used for track days, for example). Is this true and, if so, is it dramatic? An extra track day, perhaps?Richard KihnleyWest Palm Beach, FL
How many times a tire heats up and cools down is one of many factors that determine its longevity, and using tire warmers will extend a tire's life by minimizing the number of heat cycles. Street tires and the hybrid high-performance sport tires are only slightly affected by heat cycling, as they are designed to warm up and cool down often, with little degradation in performance. DOT race tires, on the other hand, are intended to be used at peak performance for just a single heat cycle. Using warmers will make a noticeable difference in how long those tires will hold their performance. There are many other aspects toconsider-temperature, the track, your riding, how powerful your bike is and so on-but it's doubtful you'll be able to stretch a DOT race tire's lifespan by a full track day just by using warmers.
When too soft means too stiffI was reading your very helpful article on suspension tuning ("Suspension Tuning Guide," online at www. sportrider.com) and noticed this passage, which is counterintuitive to me:
"An easy way to check if your shock spring rate is in the ballpark is to measure the rear 'free' sag, that is, the sag without your weight on the bike. This number should be between 0 and 5mm-with the bike off its stand and on its own, you should be able to lift the rear end just slightly and top out the suspension. If your bike is topped out at rest, you need a stiffer spring, because you have got a lot of preload dialed in to achieve the correct static sag. Alternately, if your bike has a lot of free sag (you can lift the rear a bunch before it tops out), you need a softer spring."
I believe the words "stiffer" and "softer" should be swapped to make the sentence accurate. A soft spring will sag at rest (under the weight of the bike alone), and a stiff one would "top out." Thanks for the article.Jeff CulottaFrom Srmail
The sentence is correct. It may help to picture it this way: If you have a spring that is way too stiff, it's hardly going to move when you sit on the bike. Say the spring is stiff enough that it will only let the rear end drop by 5mm when you sit on the bike. To get 25mm of rider sag (from fully topped out to the position with you sitting on it), the free sag would have to be 20mm.
The opposite is true with a very soft spring. The rear end will compress significantly when you sit on it. For example, a soft spring may let the rear end move as much as 50mm when you sit on the bike, if there was that much travel available. To get just 25mm of sag, you'd have to crank in a boatload of preload, and the spring would top out hard against its stop, wanting to move a further 25mm beyond where it normally rests under free sag.
Drag Racing An FZ1For the quickest times in the quarter-mile, do you suggest shifting just past the horsepower peak or clicking the next gear at redline? I have an '02 FZ1; the power peak is at 9750 rpm and redline is 11,500 rpm. Also, what do you suggest for suspension setup on the FZ1 for the dragstrip? My thought was to go to the lightest setting on the rear shock's spring preload and compression damping and the heaviest setting on the rebound damping, and tying down the front suspenders.DuaneTwin Falls, ID
Minimizing your quarter-mile time requires you to maximize the amount of thrust, or driving force, to the rear wheel for the whole pass. Thrust at any speed depends on torque, rpm and gearing, and you can download a spreadsheet at www.sportrider.com/0704 that will help you calculate the optimum shift point for each gear-most often it ends up being somewhere between the power peak and redline. The lower you can get your FZ1 on its suspension the better it will launch at the dragstrip. Look into a strap for the front end and a lowering link for out back. You can also slide the forks up in the triple clamps, but keep an eye on tire clearance. Dial in maximum compression and rebound damping and preload up front; this keeps the front end from bouncing up into a wheelie off the line. You can run rear preload a bit soft to help keep the rear end low, but firm up the compression damping to reduce weight transfer and wheelies. With your FZ1 it's all about keeping that front wheel on the ground.