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Decreasing radius corners

Discussion in 'New Riders and Riding Tips' started by ebf00, Jun 17, 2014.

  1. #1 ebf00, Jun 17, 2014
    Last edited by a moderator: Jul 13, 2015

    Wrote this up on my blog but wanted to share it with you all. Mods, if you think this should go in one of the existing cornering threads, feel free to move it, though I think decreasing radius corners deserve their own special attention :watching:


    Nothing gets a rider’s heart jumping into their mouth and their eyes opening out like saucers, then finding themselves in a decreasing radius corner going too fast. It can set off instincts like nothing else on a bike, with riders chopping the throttle and standing the bike up, causing more trouble than it fixes.

    A decreasing radius corner is essentially a corner that tightens up. That means that if you take a normal mid apex line into the corner as you might on a constant radius turn, you’re going to find yourself running wide unless you have enough in ‘reserve’ to really lean the bike over. That’s not a good place to be if you have oncoming traffic (or other things to crash into).

    So, how can you spot a decreasing radius corner? And what’s the best way to approach them? Well, read on (or watch on) to find out.

    Spotting a Decreasing Radius Corner

    It should go without saying that if you’re riding on unfamiliar roads, you should be going at 6/10ths of your limits to begin with. That way, if you do find yourself in a tightening corner, you’ll have the ability to keep rolling on the throttle and lean the bike over to exit the corner smoothly.

    That said, you can, with some practice learn to spot a decreasing radius corner on the road.

    In a decreasing radius corner, you’ll find that the further you go into the corner, the vanishing point will appear to be coming towards you. This effect is quite subtle compared to how a vanishing point moves away in an increasing radius corner, but with enough practice, you’ll begin to spot a tightening turn, allowing you to position the bike correctly for a later apex.

    Taking a Decreasing Radius Corner

    A decreasing radius corner requires two things – late turn in and late apex. Have a look at the diagram below.

    By turning in late, you cut down the lean angle required to make the turn. Same with the late apex. But putting theory into practice isn't always easy, so let’s break it down. We’ll cut the corner into three sections to help make it easier.


    The first part of the turn involves staying as wide as possible until you turn in. Some riders may find this difficult, as you’re well into the turn before you actually turn in and commit. The natural inclination is to look towards the inside of the corner straight away – but in this situation, it would mean you hit the apex around the midpoint, and as the corner tightens, it would throw you wide.

    The best way to overcome this is simple – look where you want to go. As you enter the corner, spot your turn in point and look towards it.

    Remember throttle control too. Again, a rider may be apprehensive about being wide so far into the corner and reduce throttle. That will lower speed and therefore the bike will move towards the inside of the corner. You’ll need neutral to slightly open throttle to maintain the wide line.

    Upon hitting the turn in point, you’re in the second part of the corner. Flick the bike over quickly and head for your apex. Immediately roll on the throttle (don’t chop it whatever you do) and put in enough lean so you don’t run wide. Rolling on at this point will unload the front end and put as much grip as possible into the rear tire. Because of taking such a late turn in, you won’t need to lean in nearly as much and that allows you plenty of reserve should you need it.

    Third, upon hitting the apex, continue to open the throttle and make a nice smooth exit.

    Following these steps will probably take some practice, as the approach to a decreasing radius corner can feel counter intuitive. If you have access at a local track that features such a corner, keep practicing by taking later and later turn-in points until you feel you've got it right. Alternatively, do the same on a quiet piece of road at lower speeds until you feel confident.
    • Informative Informative x 4
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  2. To me they are a very rare thing,I expect road builders would avoid them like the plague.I seriously think I have only ever struck one in the 30 plus years of riding.That was one of the southern corners in The Bulladeala Bends.Post up any others around would be good/
  3. You would think so but they are around, a decreasing from one side is increasing from the other.

    Equally a corner whose camber goes from positive to neutral, or neutral to negative, elevation change, or change in road surface from good->not so good will have the same net result as a decreasing radius - you will drift wide through it if no correction is made.

    To ride a decreasing radius corner properly its extremely beneficial to have identified it and have a plan beforehand, same goes for most corners but more so for these. Much easier to do on a track.

    Lastly I'd say use your brain and apply some caution when applying track riding techniques on the road, esp ones where your line becomes at odds with how the road engineers planned it and what the environmental factors might be. Running hard up against the outside, braking late and turning in late is potentially a recipe for disaster. Racetracks are geared up for that with well calculated runoff areas for inevitable mis-timings, roads are not as forgiving.
    • Agree Agree x 2
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  4. Good information for a track day but if you are on a public road and this causes you a problem then you are a hoon and an accident waiting to happen. The road is shared with other users who could be coming the other way. You are not only putting your self at risk but everyone else.
    • Agree Agree x 2
  5. Good point - they're unlikely to exist in modern road design, but there's probably a few around for yesteryear.
  6. With respect, I think you've taken the wrong message away from the video. While the initial part was about creating higher exit speed on track, there's is no part of the advice that actually puts you at higher risk on the road.
    Staying wide (albeit with the proviso relating to roadside debris) gives you better vision, and rolling on stabilises the bike. That doesn't equate to hooning, it's simply good technique.

    The vid is about what to do when you've misjudged a corner, so that you don't become a hazard. It's going to happen to you one day no matter how you ride.
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  7. I agree that it is good practice but on a shared road you don't have all that much room to use. You should not be at a speed that you require the whole of your lane as the other driver may be on your side already and you room is limited. You should never require more than your own lane in any case and should consider that the other driver/rider will be doing the wrong thing and be at a speed to deal with anything they may throw at you. I feel that a large number of accidents, whilst maybe the other parties fault, could have been avoided if the victim had not expected the other party to do the right thing in the first place. Defensive driving/riding.
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  8. OK. In principle I can agree with a lot of that.
    Totally agree that in general it's better that you not exceed your own lane (with some exceptions). Also agree that you need to accommodate others who might create a threat.
    And also agree with keeping enough in reserve to deal with an emergency.
    But the story is about reacting to particular situation
    I'll try and be clear - I don't think it's about how to go into a corner harder or faster, I think it's purely about how to react when you find that you have misjudged the corner. Being conservative isn't always going to save you from that IMO.
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  9. If you've been around long enough, then you have misjudged a corner at some time in your life and this is excellent techinque for dealing with an error of judgement. There is a corner called Lemming Corner on the Wollombi road that is a perfect example of this. I was fortunate enough to be with an experienced rider who warned me about it and pointed it out to me.

    I can also see the need for this technique in situations of unfamiliar road where you can't see the exit of even the apex due to a cliff face or overgrown vegetation. There are all sorts of distractions that can effect your entry speed. An example would be a tail gating car or truck. Sometimes you can't ride as slow as you wish due to conditions beyond your control.
    • Funny Funny x 1
  10. Excellent info
  11. Yeah, perhaps a good addition is -

    Use this technique on any unfamiliar road, that is: wide entry, late turn in and late apex. In effect, treat every corner like a potential decreasing radius corner.
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  12. Excellent post. I've always thought a different sign post is needed for the decreasing radius corner. Shaped like a fish hook. It would be better than the usual curved arrow, I think.
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  13. @pod@pod because you were not specific I am not sure exactly what issues you had with the advice. It may be like a lot of Netrider debates there is basic agreement and quiblbing only over minor differences.

    But although the advice in the video was framed for the track and speed, the advice still holds for road use.

    Staying wide provides maximum vision vision around the corner and therefore gives earlier warning of oncoming traffic and other obstacles. Late turn and late apex tends to point you much more in line with the exit rather than running wide.

    In my view the advice is sound.
    • Like Like x 4
  14. You may come across a situation where you need to do this even in a regular, or consistent corner. Most hairpins I come across for one. Cars and especially trucks chew up the inside of the corner. Not their fault either, their diffs are locked so the inside tyre is always going to spin up and hop. Better for mine to ride around it or set up so your riding a pretty strait line without much lean through them bumps, and dogs find the damnedest places to die... you get where I'm coming from.
    And as for track only... that's not the line I would take at the track. My braking section is through the first apex to the part 2 sign and I'm going to block pass noddy there spin it, sit it up and get out of there.... well that would be the fastest way through there on anything over and including a 600.
  15. I like the technique show hear, it agrees with my cornering bible.
  16. This is fair advice for a reducing radius corner that you're aware off. But what happens when one springs up on you because you cocked up your visual cues?
  17. Thanks ebf00. That was good info.
  18. Well, the rule of 6/10ths should apply - always ride slow enough for your skill level to ensure if you don't correctly identify the corner, you've got plenty in reserve to save your skin.
  19. Where's the fun in that?
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  20. BS, go hard, tip that biatch in, if its not enough give it some more. Get on the gas hard, job done