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Featured Just how much contact do you have with the road?

Discussion in 'New Riders and Riding Tips' at netrider.net.au started by iClint, Mar 12, 2015.

  1. #1 iClint, Mar 12, 2015
    Last edited: Mar 12, 2015
    Note: This is aimed at newer less experienced riders in the hope to build their confidence cornering.

    One myth I have heard repeated many times is you shouldn't use your brakes while riding with the bike leaned over as you have less contact with the road.

    The truth is with modern bikes/tyres you actually have more contact with the road while leaned over and even more with the tyres loaded correctly.

    While riding in a straight line your contact with the road is very small but this is all you need as you actually want less rolling friction for the bike to be more efficient.

    Screen Shot 2015-03-12 at 7.57.17 am.

    When turning though you need more contact with the road as you are battling many forces as you attempt to change the bikes direction.

    Hearing nonsense such as you have "Less" contact with the road while leaned over doesn't inspire much confidence with new riders as they try to overcome their own basic instincts so I thought I might share some photos showing exactly what your tyres are doing in real world situations.

    The Quality of the photo's are grainy as they have been enlarged and corrected to remove shadows and give the best detail

    In the picture below the bike is accelerating out of the corner there is not much load on the tyre other than that caused by the bike attempting to turn rather than travel in a straight line (centrifugal force) as the bike travels in an arc around the corner. A much larger contact patch with the road is created when compared with just traveling in a straight line.

    Screen Shot 2015-03-12 at 7.40.32 am.

    In this next photo the bike is braking hard in the corner with the bike leaned over there is much more load on the tyre as is evident in the amount of suspension left. The tyre is now almost completely pressed into the road and is supplying a massive amount of grip, this is simply achieved through good braking technique i.e. Set up and squeeze, more and more brake force can be applied as the tyre is pushed harder and harder into the road.

    Screen Shot 2015-03-12 at 7.55.01 am.

    Of course the tyre has a finite amount of grip and if that grip is exceeded the tyre will break traction with the road, BUT as is shown in the photo's the contact with road is NOT lessened as the bike is leaned over but actually increased and as the tyres are pushed harder into the road more grip is generated.

    The same is true of the rear tyre.

    As the bike is leaned over the contact patch becomes larger again. In the next picture the bike is decelerating the load on the rear tyre is minimal but the tyre is still being pushed into the road as it again battles the forces put on it as it travels in an arc.

    Screen Shot 2015-03-12 at 8.21.09 am.

    The really interesting thing is what happens when we really start to put a lot of load on the rear tyre and just how large this contact with the road can become.

    In the next photo many forces are being applied to the rear wheel, as more and more load is applied the bike can accelerate harder without breaking traction, the harder the bike accelerate the more load is applied to the tyre. You may have heard this being described as "Rolling on the throttle" as you exit the corner.

    Screen Shot 2015-03-12 at 7.44.02 am.

    I hope this gives some newer riders the knowledge to feel more confident the next time you are tipping your bike into a corner, as well as no longer fearing the brake lever with the bike tipped over.

    For newer riders please keep in mind that some of what I have described here are some of the more advanced techniques of cornering and braking, these are skills you must build up to. It is also extremely important you maintain your bike, closely monitoring tyre pressures and making sure your bike is in top condition every time you ride.

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  2. AFAIK the problem with braking in corners isn't so much breaking traction, but standing the bike upright causing you to go wide. Also the result of locking either wheel while in a turn is far more drastic and harder to recover from whilst navigating a turn.
  3. #3 iClint, Mar 12, 2015
    Last edited: Mar 12, 2015
    I'll answer this for you as it is another misconception.

    Yes braking with the bike leaned over will stand the bike up.... Solution = counter steering!

    As the bike wants to stand itself up you simply push on the bar for the direct you want the bike to continue traveling in to counter the bike wanting to stand back up.

    But one day you are going to need to perform an emergency stop in a corner and if you are scared to or don't know how to use your brakes in a corner or have never practised how will you save yourself?

    In our learner/P training they tell us to just stand the bike up and brake while this isn't entirely wrong it is incredibly dangerous as you rarely have room to just stand the bike up and brake without running off the road or crossing to the wrong side.

    an emergency brake can be performed in a turn using the exact same technique as braking in a straight line.
    - set up the brakes
    - squeeze
    - as the tyres become loaded you can squeeze harder

    While doing this though you need to apply a force on the bars to counter the bike wanting to stand up.

    here's the trick bit. :D as the bike slows the angle the bike is leaned over at reduces until you are completely up right and appling the maximum amount of brake force you can.

    So effectively you have stood the bike up and braked all at the same time reducing the risk of running off the road or into oncoming traffic and your overall stopping distance

    as for the risk of locking the wheels if you set up and squeeze the risk is really no greater than doing it in a straight line.

    Yes you are using more of your available grip in a turn, but there is much more grip there than most of us actually realise when good technique is used.
  4. Nice photos, they really illustrate well what you normally see in diagrams/drawings.

    Two observations from a newbie:

    1. During the HART "P plate test" - the longer version, the instructor had enough time to cover some skills not required for the license test including braking while cornering - playing withth brake balance front & rear. Very educational in a safe environment. Showed one reason for always using the rear brake as well – so you will automatically use it, not just remembering it just after it’s too late.

    2. Saturday morning “Netrider Cones” is fantastic for a complete beginner to put aside the worries of dangers of other road users etc. and find out how much grip your bike really has in a corner. I learnt that in the dry at Elwood my guts/ability/common sense ran out long before I approached my bike's limits. Caveat being in those particular conditions – i.e. didn’t make me think I was Marc Marquez in every corner.
  5. Good post iclint.

    I'd like to add - the more lean angle your bike has, the more turn rate it must be experiencing for the given speed, and that means the more traction being chewed up for turning, thus leaving less for braking. As you bring a bike up, it turns less, so more effort can go into braking. It's a seesaw trade off.

    I sometime think riders misdirect themselves about the contact patch when it's really a traction picture that you're trying to manage.

    I think the following two articles round out the discussion and give the underlying physics reasonably simply.
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  6. This is true, but it should also be pointed out that riding around at speeds approximating the speed limit, your bike/tyres will usually have a large reserve of traction available and you do not come close to using anywhere near your available traction for turning, so you can usually brake within a corner without problem or bother. It is still of course far preferable to do any braking before you get to the corner and then use the throttle within the corner.
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  7. True, much easier to speed up than it is to slow down.

    The post isn't about how to setup for, or enter corners robsalvvrobsalvv Noob 101 threads have that all covered this thread is purely to demonstrate what ones tyres are doing in the corner. Showing how tyres flatten out and deform under different loads when the bike is leaning over.

    Regardless of how we enter a corner has no effect over what might happen mid corner, and the truth is many riders new and old are nervous about tipping a bike over and worse, terrified of touching those brake lever in a turn.

    Motivation for this thread came from eating an ice cream at bald hill and overhearing conversations behind me spouting a lot of crap, one of them was about having less contact with the road when the bike is leaned over.
  8. FWIW if I mess it up and need to lose a small amount of speed in a corner, then the rear brake is my tool of choice. Or if I really mess it up rear brake plus a little front brake. Although the theory is that the bike stands up when you brake, I've never found that to happen. Personally I've always found that my turn tightens if I brake mid-corner. Obvs as I said before, best to get your speed right before the corner so you don't need to brake and power through with the throttle open.

    I followed a couple of bikers through the Royal National Park on the weekend (no P or L plates). They were really nervous about leaning their bike over. They were even holding me up a bit and I was driving a Nissan Micra with 2 adults and 2 kids in it!!
  9. You said the rear brake is your tool of choice, the short answer is when you use the rear brake to slow the rear wheel the front wheel effectively wants to turn around the rear wheel tightening the line. It's a handy tool but IMO it is bad practice, counter steering remains the most effective way to turn a bike (tighten a line)

    Using both brakes together and loading the front tyre will create more friction between the front tyre and the road. This added friction gives you more grip to turn the bike but you will have to over come the bikes desire to travel in a straight line (stand up) which also increases.
  10. ^ is why I linked the msgroup articles that I did. It directly addresses this fear.
  11. Don't forget the traction circle!


    PS I'm always impressed by people that can use their rear brake subtly enough to use it in corners without coming off. Maybe I'm just ham footed but I'm much more delicate on the front. Or I just use engine braking, which also can be used delicately.
  12.  Top
  13. ??

    Well, let's look at a normal and reasonable example. You are traveling at 50 MPH in a curve that has a radius of 335 feet. As a result, your bike is leaned over at an angle of 27 degrees and you are experiencing lateral acceleration of 0.5g's. How hard can you brake in that case without exceeding the traction your tire's provide?

    Again assuming that your tires (and the roadway) support 1.0g's of force before skidding or sliding, then you can apply as much as 0.87g's of braking force. That is a WORLD-CLASS BRAKING EFFORT before a slide will occur! Most riders cannot get a deceleration rate of more than about 0.80g's, even in a panic stop!

  14. When I've looked at racers data its pretty close. (They measure longitudinal and lateral acceleration). Well perhaps a bit more oblong but a circle isn't a bad approx.
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  15. LjiljanLjiljan What's the confusion? In the diagram above, the circle represents 0.9g.

    But in the example, if the circle represents 1g and you're cornering at 0.5g then a bit of Pythagoras gives you braking possibility up to 0.87g.
  16. The straight down arrow in the last of the OP pictures of the bike leaned over is off the mark either way.

    It infers that even when leaned over, the tyre is being forced directly downward into the road, and that just isn't so.
  17. I use the rear brake or light application of both brakes to slow in a corner, not to tighten my line. The tightening happens as a side effect of braking in a corner. As I said, this happens when I have made a mistake and my speed in the corner exceeds my comfort level. I could almost certainly make it around by steering further, but since I have already exceeded my comfort level, I don't want to steer further, I just want to slow down a bit. This all happens when I've messed it up and I've entered the corner too fast, am not on a closed throttle and am getting a bit bothered. Mistakes happen.

    FWIW my bike (ST-1300) has linked brakes so application of the rear brake will give a small amount of front brake and vice-versa. But on this bike the combined braking is very unobtrusive, can hardly notice it.
  18. The purpose of the post wasn't nit pic numbers or which way the arrow should be pointing (Down and out would have been better but hard to depict on a 2D image despite the forces in play being described) the point was to show what is happening in the real world and help inspire confidence in others to trust their tyres

    For most people numbers and graphs are pointless - I would think a picture showing the forces in play, the tyre being deformed and pushed into the road and generating the grip that makes it all happen would be of more worth.

    You don't have to be a master of mathematics and physics to steer a bike.

    That's me riding in the pictures I haven't the foggiest how many G's I'm pulling nor did I have the time to run some calculations before I threw the bike in or braked up to the apex, nor did I have to.
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  19. So it's correct?
  20. Would the arrow in your picture not also point downward regardless of what correction you made to represent the Bike traveling in and arc and their being both a down and out force?

    In relation to the bike no matter which way you spin it the the is being pushed down