Rear Slides and Saves

[Jaybird180]

I'd like to discuss rear slides a moment. In all cases below, the rider is leaned over in a turn. For simplicity sake, let's say the rider is mid-corner, established in said right turn and the corner is flat, level and symmetrical. Let's also define the apex of the corner as the geometric center of the turn. Let's also say the rider's throttle control is standard.

1. Bike on dry pavement the rear end slides, the rider is loose on the bars and allows the bike to attempt to self-correct. Which way do the bars turn?
2. Bike on a compromised surface and the rear end slides, the rider is loose on the bars and allows the bike to attempt to self-correct. Do the bars turn?
3. Can the rider in either scenario turn the bars to give a corrective action? Is the answer the same for both conditions 1 and 2?
4. If the rider give the opposite input to the bars in a slide scenario will the rider's action aggravate the situation? Is the answer the same for both conditions 1 and 2?

After the above scenario #1, let's assume the rider's throttle control isn't standard. In fact, the rider has a timing error with the increased roll-rate and initiates a pickup of the bike post-apex in attempt to alleviate some of the turning forces. Due to the timing error, the throttle comes on at the same time (or perhaps with a microsecond lead) as an aggressive pick-up steering input. The rear end begins to slide.

• Is the slide in the same direction as above?
• Because the bike is vertical (or nearly so) but still following a circular trajectory which direction does the front end turn for corrective action?
• Can aggressiveness of a pickup cause an upset of traction?  (I once called this a quick "un-flick")

 

[Hotfoot]

3 hours ago, Jaybird180 said:

I'd like to discuss rear slides a moment. In all cases below, the rider is leaned over in a turn. For simplicity sake, let's say the rider is mid-corner, established in said right turn and the corner is flat, level and symmetrical. Let's also define the apex of the corner as the geometric center of the turn. Let's also say the rider's throttle control is standard.

1. Bike on dry pavement the rear end slides, the rider is loose on the bars and allows the bike to attempt to self-correct. Which way do the bars turn?
2. Bike on a compromised surface and the rear end slides, the rider is loose on the bars and allows the bike to attempt to self-correct. Do the bars turn?
3. Can the rider in either scenario turn the bars to give a corrective action? Is the answer the same for both conditions 1 and 2?
4. If the rider give the opposite input to the bars in a slide scenario will the rider's action aggravate the situation? Is the answer the same for both conditions 1 and 2?

After the above scenario #1, let's assume the rider's throttle control isn't standard. In fact, the rider has a timing error with the increased roll-rate and initiates a pickup of the bike post-apex in attempt to alleviate some of the turning forces. Due to the timing error, the throttle comes on at the same time (or perhaps with a microsecond lead) as an aggressive pick-up steering input. The rear end begins to slide.

• Is the slide in the same direction as above?
• Because the bike is vertical (or nearly so) but still following a circular trajectory which direction does the front end turn for corrective action?
• Can aggressiveness of a pickup cause an upset of traction?  (I once called this a quick "un-flick")

 

Points 1-4 is covered specifically and in detail in Twist of the Wrist II in Chapter 10: Rider Input, Riding and Sliding. There is a good diagram and description of what the front wheel and the bars will do in a slide, which way they will turn. It also tells you exactly what happens if the rider tries to turn the bars or gives the opposite input. It is better read there than answered here, since there is a thorough explanation, diagram and photo.

In regards to your second set of questions - yes the slide would be in the same direction - the angular momentum of the bike would send the rear wheel to the outside of the curve.

If the bike is nearly vertical, you are not on a circular trajectory anymore. The front wheel will still turn the same direction as your scenarios above (as described in TOTW II), but if you are mostly upright it wouldn't be much, because at that point you are going mostly straight.

The pick up will improve your traction by getting the bike more upright. However it is always possible to upset the chassis or suspension with an overly aggressive bar input; it would seem very unlikely especially in good traction conditions for it to actually cause a crash but possibly if you seriously overloaded the front suspension with a really heavy bar input, way oversteered it, OR unintentionally braced with your other arm thereby loading BOTH bars and creating a rigid transfer point between the bars and your body (and thus the rest of the bike) you could cause a wobble or an unwanted bounce from the front suspension or tire. If a rider tries to do a really aggressive, fast pick up right around the moment where he/she is trying to begin their roll-on, how likely is that the roll on itself will be smooth and progressive? If the roll-on is, as a result, too abrupt, what could happen to the rear tire traction?

 

[Jaybird180]

I'll check out Ch 10 again.

Thanks for the catch about the pickup and the change in trajectory, however I'd always  thought of it as a way to finish the corner with throttle but the rider ins't yet going down the straight. Or perhaps as a way to quickly arrest the circular trajectory and get the bike pointed straight. Perhaps I've got a misunderstanding about that area....?

[Hotfoot]

What is your understanding of HOW to do the pickup? How it is different from simply countersteering out of a turn?

[Jaybird180]

Pickup is a conscious decided effort. The rider intends to lift the bike to vertical at a much earlier point in the turn than allowing a lazy vertical movement later when the bike is decidedly passed the exit.

[Hotfoot]

Yes it sounds like there may be some misunderstanding of the purpose and application of the pick up drill, and some pieces that are missing. I'll PM you and we will get it sorted out.:)

[Jaybird180]

AWESOME!!!