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Straight line -vs- trail braking
One of the questions that I seem to get fairly frequently is what do I think about trail braking into bends. And when I do discuss it, it's often a bit of a biking hot potato, with supporters on the one hand and others who say it's a dangerous race track technique with no place on the road. First of all, it's important that we understand the difference beween the two techniques, but also how they are linked. And we also need to be aware of what is sometimes called the 'Traction Pie'. Essentially, is explains how it's possible that we can divide up the grip that's needed BETWEEN braking AND cornering at the same time.
The classic braking technique on the approach to a corner is to complete all braking before we start to steer the bike. The big advantage of this technique is that it separates traction management into two phases, FIRST braking THEN cornering. By keeping them apart we allow the tyres to use ALL their grip for one task OR the other. As a result, we significantly reduce the risk of losing traction at either end of the bike.
By contrast, when using the trail-braking technique the rider carries the brakes from the upright approach into the corner, gradually reducing the pressure on the brakes while adding lean angle until the brakes are off and the bike is at the chosen lean angle.
So what's the problem?
Essentially, because the braking forces are using up traction AT THE SAME TIME AS the leaning forces, it's possible to exceed the total amount of traction they tyres can deliver. And if that happens, we're in trouble.
It's that potential for loss of grip that's always been used to promote the traditional upright braking approach to bends - if a wheel does lock under braking, upright it's controllable even on a bike without ABS.
Separating braking and steering is by far and away the simplest way of dealing with a bend, and there's far less to go wrong. Not least, if we're off the brakes, we free ourselves up mentally to look around the corner to see what comes next. If we're on the brakes, we're actually mentally focused on the road surface itself (think about it) and what we might hit if it all goes wrong - cars, walls and other hard objects - and that in turn leads us in the direction of target fixation.
So why bother with trail braking at all? Two reasons.
The first is simply 'advantage' - since we carry the brakes into the first part of the corner, it's possible to brake a little later, which means we carry speed a little further down the preceding straight. You've probably realised where this would be an advantage - on the track.
You may also have heard that "the bike steers better with the forks compressed". It's actually written on Freddie Spencer's site and it's hard to argue with a racer as talented as Freddie. But I can honestly say that every road bike I've ridden has, to a greater or a less extent, sat up and headed for the ditch on the brakes. Maybe a race bike set up on race tyres and race geometry does steer OK on the brakes, but my thinking is that this is a misunderstanding of what's happening - as the bike slows on the brakes, it turns on a progressively tighter line simply because the speed is dropping.
Anyway, we're not riding on the track, we're on the road. We're not out-braking other riders, nor trying to squeeze half a second off our point-to-point time. In fact, attempting trail braking as a regular approach to getting round bends risks all the things that goes wrong in bends:
- running in too fast
- turning in too early
- running wide later in the corner
But with an added problem - because we're braking and steering at the same time, we'll be edging closer to the limit of traction. And of course, we're assuming that the surface can deliver the grip we're asking for - but surface grip can very from metre to metre. When we deliberately trail brake into a bend and get it wrong or the surface fails to deliver, the bend will bite back - hard! Which brings us right back to the benefits of braking upright to sort out speed before we reach the bend itself. On the road, braking hard and late is rarely the key to riding quickly - it just unsettles the bike and unsettles the rider!
As it happens, Nick Ienatsch - another US racer and writer for the US mag Sport Rider who is a big fan of trail braking on the track - says in his 'The Pace' articles that trail braking makes steering more difficult and is out of place on the road.
So if we're not simply trying to use trail braking to ride faster, what's the other potential benefit?
The simple answer is that we're not on a track, and that means the road ahead is essentially unpredictable. Not only do we misjudge corners - the bend that looked easy a moment ago suddenly starts tightening up - or we may find the road blocked just out of sight. Even if we approach the bend 'at a speed that allows us to stop in the distance we can see to be clear', if our forward progress reveals a couple of cows wandering around mid-corner, we're going to have to lose some speed. We cannot throw our hands up and say "but I can only brake in a straight line", we are almost certainly going to have to carry those brakes into the corner itself.
So now we really are talking about a technique that is of genuine use on the road. So long as we weren't planning on enter the corner at knee-down speeds, then our modest lean angle allows for those brakes to be carried into turn.
And then we have two further options. We can keep the brakes on, and maintain our lean angle - and then, as I just mentioned, our reduction in speed will automatically make the bike turn tighter. That will deal with decreasing radius corner. Or we can use the reduction in speed to reduce our lean angle, and now as the lean angle comes up we can use the second option - brake progressively harder until the bike is upright and we're braking at emergency levels. That will get us stopped if the road is blocked.
But in both cases we have to understand that if we haven't already locked up the front wheel by braking in a straight line, there is ALWAYS grip to begin to steer and add some lean. It may not be much if we're braking hard, but it's there all the same.
We just have to lean the machine gently to start with, and remember that as we feed lean in, we feed the brakes out.
Mix and match. Slice that pie between the leaning and braking.
One final tip. Having got the speed where we want it, release the brakes smoothly and progressively - don't suddenly ping them off. If we do, that will unload the front suspension equally suddenly, and that will give us a very nasty surprise indeed. Because we've added a little extra counter-steering input to fight the bike's 'sit-up on the brakes' tendency, removing the braking force means that extra steering input makes it fall into the corner rather abruptly.
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