Recently, I saw a forum post I’ve seen all too many times. The rider left his house on his GSX-R600 following his friend on an SV650. The GSX-R hadn’t been out of the garage in almost a year. The tires weren’t fresh. It was chilly, about 52 degrees, the poster guessed. They rode down the street to make a right turn at the intersection and the GSX-R hit the deck halfway through the turn. “The front tire lost grip. I was going so slow!”
The blame went right to the old, cold tire and rightly so. Old, cold rubber isn’t very grippy. But there are times when we must ride on old or cold or old and cold tires, and this article will describe the problem and the solution. This forum post and my 18 years of teaching winter schools points to one particular series of events that is responsible for over 98-percent of these chilly tip-overs.
Two-percent of the cold-tire crashes are grabs of the brake lever that immediately overwhelm the front tire, or stabs of the Throttle that cause the cold rear tire to break loose in an instant. You probably could have guessed at those two issues and work hard to avoid them on your own cold tires. Most riders know that a tire slides when it’s finally overloaded and they ride gingerly on cold tires…they are “smooth”. But the most common cold-tire crash I’ve seen isn’t as easy to explain. In fact, it leaves riders shocked and decidedly un-confident…“I was just cruising…”
Let’s start with leaving the pits (or riding away from your house because this is a common first-intersection crash). The rider is riding slowly, warming his body and tires, with speeds probably 50-percent of his true pace. He turns into a corner gingerly, thinks to himself, “I’m in way too slow”…and picks up the throttle nice and early.
When he picks up the throttle, where does the weight go? Correct, to the rear…and off the front. The front contact patch gets smaller, and remember, it’s not warm yet. And now the crash is just one step away.
Because the rider entered the corner slowly and picked up the throttle “nice and early”, he often does not yet have the bike pointed out of the corner. To put it another way, the bike hasn’t changed direction to match the exit path the rider wants. What does he do as he picks up the throttle? How about lean over further? And BAM!…he’s down.
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He entered slowly and opened the throttle before the direction change was complete. That made the front contact patch smaller…and then he asked that contact patch to work harder by adding lean angle. No problem on a warm tire but ask any tire engineer and she’ll tell you the exact heat window her company’s tires are designed to work within. Tires need heat.
The most common spot for this crash is a 180-degree corner where the “direction change” comes fairly late…easy to get in too slow and try to fix it with the throttle…but then you arrive at the direction change with a small patch of cold rubber. No grip.
The fix to this incredibly common cold tire crash receives major attention at the Champions school on cold and/or wet days. We get riders focused on: Use the brakes until you’re happy with your direction, and: Don’t accelerate until you can see your exit and take away lean angle. These two concepts are relentlessly discussed during winter days because they reduce those cold-tire crashes so drastically.
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For our forum poster who lost the front in the right-hand intersection turn, the answer is to leave the throttle shut and weight forward as the bike turns into the corner. Put another way, leave the cold contact patch loaded at the turn-in.
This crash will happen anytime front grip is low and the rider’s mind isn’t on the front contact patch…rain, slick pavement, new tire, old tire. I encourage you to study how you unload the front tire and then ask it to work harder by Adding Lean Angle, realizing you are asking less rubber to do more. The more we stress loading the front tire at the direction change, the fewer crashes we have at the Champ school.
Source: Cycle World