Slide Rules

By Andy Ibbot

The most common question all riders have when cornering a bike is "How much traction do I have?" and "How do I know when the back/front will lose traction?"
Sliding a bike at either or both ends is a skill have few road or track riders embrace and yet this is one of the only ways to recognise when you are getting close to the 'edge'. And it's a fine line from the edge to the hedge as we all see week in week out in any form of road racing, and these guys are extremely good riders!
There are several different forms of sliding (backing it in, sliding it out and pushing the front) but only two results from getting it wrong, the highside or lowside.

The Lowside
Of the two the lowside is the least painful on you and your wallet. A lowside happens when you lose front tyre traction and the bike, which will already be leant over, simply falls to the ground and slides off the road or track.
Causes
The Highside
This is when the rear tyre breaks traction and then regains grip suddenly. The suspension compresses and then unloads very quickly effectively catapulting the rider over the highest side of the bike, hence the name. Very sudden and very painful in most cases as it's much the same as jumping out your bedroom window and landing on your head, shoulder, etc. Avoid at all costs!
Causes
Backing it in
It's one of the most spectacular images in motorcycle racing and there seems to be only a handful of riders that can do it - that is the ability to 'back it in' or slide the rear wheel into a turn. But why do it? None of these riders seem to be any quicker than the rest of the field so what is the point?
In theory, it squares off the corner completely when combined with a power slide on the exit. It's a bit like a rally car where the vehicle is sideways on the way in so it can be pointing up the track as soon as the exit of the corner comes into view. That's easier to do in a car as it has four points of balance in each corner, its wheels.
A bike only has the two so there is a hell of a lot more skill required to get the bike sideways without it high siding the rider into the green stuff.
The exception to the rule is Super Moto where the speeds are slower, the corners tighter and the bikes more set up for this kind of riding.

The ideal is to keep the rear wheel spinning but going at a slower road speed that the rest of the bike. If the rear wheel is locked then the bike soon goes completely out of control, but if it is still turning the gyroscopic effect of the bigger rear wheel keeps the bike balanced and under control. But it's a fine line…
On questioning several World-class riders on the technique there seems to be two ways you can get the bike to be unbalanced on the way into the corner.
There are pros and cons to both and the answer lies in using both of them together.
Using the rear brake alone is the more difficult of the two, as it requires an extra ordinary amount of concentration. Too much and the back end will come round too far and result in a crash. Too little and the effect is not enough. While feathering the rear you will need to be hard on the front brakes too. After all, you are approaching a corner and need to set your speed. Hard on the front makes the weight of the bike transfer to the front which is good as it makes the back of the bike lighter and therefore making it much easier to breakaway.
So far so good, the bike is out of line as you enter the first part of the corner. Now comes the hard part. You need to get the bike turned (leant over remembering that the more you lean the less grip you have) and release the pressure on the brake slowly enough that the tyre doesn't suddenly grip and highside you.
As you might have already worked out this is going to be easier to do on left-handers than on rights. On right-handers you will need to be able to get off the brake and into a knee down position as or before you turn the bike. This will be easier if you have a thumb operated rear brake. On top of all this you still have the front brake to control, the throttle, you need to looking into the turn, spot your reference points, set your body position as well as another half dozen other operating controls.

The other, 'easier' way is to over-rev the engine and use that as your brake. When you get into the braking zone rather than smoothly blipping the engine and changing down each gear with engine revs to match your road speed you just go for one big change and over rev the motor. This has the same effect as jumping on the rear brake and will cause massive rear end chatter if you just dumped the clutch.
The skill here is to feed the clutch out and control the slide and judder. If done right the transition from braking to power is smooth as you should be in the correct gear and revs if you did it right. The downside is you can over rev the engine to the point it will blow up. Remember that rev limiters only work on the way up the range and not on the downshift.
The other advantage of using the 'back-it-in' technique on the way in is that the bike becomes wider on the outside of the turn and could block someone trying to get around you. However, the inside of the turn is still wide open although you could get in tighter to the inside of the track if the whole plan worked out as you will be able to pull a very tight line.
Overall it looks very good but it is used less and less for road racing. But the backing it in Gods, Super Moto riders, use it to full effect and they use a combination of rear brake and downshifting.
So the ideal is to start to turn, this provides the lean angle to allow the bike to step out to correct side. Then brake using front and rear at the same time. And now downshift quickly and let the clutch out. See, it sounds so simple on paper…


Rear wheel steering
Sliding the rear however does have several advantages. It is the ultimate in throttle control. It tightens the end or any part of a corner. It allows you to still ride fast with reduced grip. It looks so cool!
But it also carries the greatest risk - the Highside.
Steering with the rear wheel is all about throttle control. The more throttle you try and apply while the bike is leant over the greater the chance of the back tyre losing grip and spinning. Watch all world class racers and riders and you will notice that they all, without exception get the bike sliding in the final part of the turn when the bike is starting the come more and more upright. If you tried to slide a bike at the apex of a corner, the point at which your lean angle is greatest you will spin the rear very suddenly and fall off. Leave aggressive throttle roll on until the exit of the turn.
Many riders confusion the feeling of the rear suspension compressing as a slide. The feeling you get is similar but when the tyre is spinning the suspension actually unloads and works more efficiently over bumps. When the tyre is close to breaking away the suspension is taking a large load from the throttle application. This is the point just before the tyre starts to slide.
There are two different types of slide. The full on slide ways action and drive lines. Once the rear wheel steps out of line from the front you are in a full on Doohan eque slide. You will feel the back of the bike out of line with the front because your bum will be moving to the outside of the corner while your handlebars are turning to match and correct the slide. That's right, if you leave the bike to its own devices it will steer into the slide and correct. If you grab hold of the bars the bike can't do this and the slide will increase.
At this point you have two choices. Roll on more throttle and at the same time pick the bike upright to slowly regain grip and drive. Again, look at the world-class riders and you will see that they are still down the inside of the bike while the bike is upright.
The mere mortals choice and for the road this really is the technique to use, check the throttle. Don't roll it on or off just keep it constant. By doing this you act like a rev limiter and allow the rear tyre to regain grip more gradually thus preventing a highside.

Pushing the front
In terms of getting it right or wrong this is the most risky of all the sliding techniques. Again there are two ways of doing it and both can end in a lowside very quickly. Both involve the front tyre carrying most of the weight of the bike into the first half of the turn. Given it has the smallest contact patch it's much harder to get right than sliding the rear as the fine line between right and crash is so thin it beggars belief. Here we have the advanced techniques of trail braking and simply being very late back to the throttle.

Trail Braking
Carrying front brake into the turn gives the tyre a lot more workload to cope with than under normal cornering. As well as trying to grip the road surface the tyre is also having to cope with the forces generated by the brake which is trying to push the tyre to the outside of the corner. You can see a lot of excellent riders push this a little too far and end up low siding. There is less feedback from the front end as the suspension is compressed more than normal because of the brakes. The ideal is to do nearly all of your braking before you turn the bike and then slowly release the brake the closer you get to the apex which is also you greatest point of lean and therefore point of least traction as the contact patch is getting smaller.
There is very little warning and the only cure is to get back to throttle to take weight off the now over loaded front.
A point of thought for you before you try this. World-class riders are running on slicks with the best grip in the world, and they still lose the front, how do you think your road or track tyre would cope?

Closed throttle
Another, slightly less risky way to loose speed in the first part of the turn is to simply run in a little too hot and keep the throttle closed. It's something we have all done from time to time when we have entered a corner way too fast frozen on the throttle waiting until the speed is something we can cope with.
It's the same thing but done on purpose. At racing speed with racing lean angle this means that the front tyre will start to slide, as it can't cope with the speed and forces generated by that. This slide slows the bike down, the purpose of the technique. With this you get a little more warning as to when you are going to dump it all on the floor.
If your grip on the bars is loose enough you will feel them wiggle a little bit as the tyre starts to lose grip and roll of its edge. This is the limit and only throttle can possibly save you. To unload the front, just as the same as trail braking you need to get back to the throttle.