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Cornering speed - how fast?


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Hey everyone. After a lot of maths, some unhappy experiences, and even a few experiments I have come to the conclusion that, on an average piece of road, the approx maximum speed you can corner at is given by

Speed (km/hr) = square root ( 89 x corner radius ) where the radius is in metres.

in words, maximum speed is the square root of eighty nine times the radius of the corner in metres

so, obviously, the tighter the corner the slower you have to go. So your classic suburban roundabout (11 metres) is around 30 to 35. For Melbournians familiar with Kew Boulevard this means you should be able to take that left hander (Strava "Cornering Speed Test - 101") above 60km/hr even if it looks pretty scary as it has a radius of almost 50m.  And, obviously, if the surface is wet, loose or off camber you have to slow down.  Conversely if the camber is positive you can go much faster.

So plug a few numbers in and see what you reckon. I'd love to get some feedback. :) You can get the radius of your favourite corners using distance measurement in google maps

Edited by PeterW
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There might be a maximum theoretical speed, but so many other factors:

- centre of gravity (lower better than higher)

- weighting of rider (eg. MotoGP riders handing off the bike)

- tire grip and size of contact patch

- extra (unwanted) inputs from rider

- road surface

- corner entry and speed of dropping bike into lean

Two riders on the same bike, same corner.  More experienced rider corners safely at 50kph, Less experienced rider slides off road at 45kph.

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17 minutes ago, Rob said:

There might be a maximum theoretical speed, but so many other factors:

- centre of gravity (lower better than higher)

- weighting of rider (eg. MotoGP riders handing off the bike)

- tire grip and size of contact patch

- extra (unwanted) inputs from rider

- road surface

- corner entry and speed of dropping bike into lean

Two riders on the same bike, same corner.  More experienced rider corners safely at 50kph, Less experienced rider slides off road at 45kph.

Yes all good, but please add the classic "own goal" where an inexperienced rider shits themselves, hits the brakes, sits up and flies off the road without losing any traction at all.  For must of us, the biggest limiting factor is our fear and so it is good to know a target speed to get a handle on how our perception of limit cornering matches some real numbers.

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Think of cornering like descending. Another words.....if you come off you most likely put your training 2-3 weeks behind schedule. If preparing for an Ironman and you then need to cram (your training in to make up) thats a problem.

Stay safe out there folks.

 

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Do you actually have to have crashed to exceed the theoretical maximum speed? Back when I was younger and had had less broken bones I only considered myself near maximum corner speed if I could feel the tyres start slipping and then maximum was the point where the slipping was no longer controllable.

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This is cool. Unfortunately I suck so bad at cornering and descending I can't possibly add to this, or even take anything away for myself :(

I would have a factor of .3 applied to the end ha ha. 

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2 hours ago, PeterW said:

Hey everyone. After a lot of maths, some unhappy experiences, and even a few experiments I have come to the conclusion that, on an average piece of road, the approx maximum speed you can corner at is given by

Speed (km/hr) = square root ( 89 x corner radius ) where the radius is in metres.

in words, maximum speed is the square root of eighty nine times the radius of the corner in metres

so, obviously, the tighter the corner the slower you have to go. So your classic suburban roundabout (11 metres) is around 30 to 35. For Melbournians familiar with Kew Boulevard this means you should be able to take that left hander (Strava "Cornering Speed Test - 101") above 60km/hr even if it looks pretty scary as it has a radius of almost 50m.  And, obviously, if the surface is wet, loose or off camber you have to slow down.  Conversely if the camber is positive you can go much faster.

So plug a few numbers in and see what you reckon. I'd love to get some feedback. :) You can get the radius of your favourite corners using distance measurement in google maps

We had an OD last week in the wet and over 20 people came off, most on the same roundabout. There are actually 4 on the course. For some reason one of them is lethal and there is no apparent reason why, similar tarmac surface, same camber etc 

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Tyres would also make a huge difference, TT tyres would have much less grip. I think I raced on Conti Podium TTs a few years ago when i almost came off on that roundabout.

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2 hours ago, zed said:

Tyres would also make a huge difference, TT tyres would have much less grip. I think I raced on Conti Podium TTs a few years ago when i almost came off on that roundabout.

Yes, very much so.  If you plan to do any cornering always use high end tyres - I can tell you from personal experience that I have lost the tail on corners end a few times by using cheaper tyres, even if from a good manufacturer.  it's horses for courses - if you want to commute on Conti Gator Skins then that is a wise choice but don't expect them to hang on anything like GP5000s.

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On 10/11/2020 at 9:26 AM, IronmanFoz said:

Think of cornering like descending. Another words.....if you come off you most likely put your training 2-3 weeks behind schedule.

This. I love bombing down hills at 75+ as much as the next guy, but at the end of the day, it's a risk/reward thing. Can I afford a broken collarbone or a few weeks in hospital? How can I explain to my wife that I was taking unnecessary risks and now she's looking after the twins on her own for the next few weeks?

At the end of the day, 99.9% of cyclists are doing it for fun, fitness or some other reason that just doesn't justify pushing the limits through a sharp corner on an open road.

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7 hours ago, BNothling said:

This. I love bombing down hills at 75+ as much as the next guy, but at the end of the day, it's a risk/reward thing. Can I afford a broken collarbone or a few weeks in hospital? How can I explain to my wife that I was taking unnecessary risks and now she's looking after the twins on her own for the next few weeks?

At the end of the day, 99.9% of cyclists are doing it for fun, fitness or some other reason that just doesn't justify pushing the limits through a sharp corner on an open road.

Yep...."King of the mountain....Queen of the descent", is the way to go. Take it easy.

I live 1 k from the gates of Bobbin Head. You'll be amazed how many ambulances go down there to pick up cyclists. I hear them all the time and then normally hear the story a few days later. And its worse in the wet. Also the 1M rule for cars has increase the number of accidents. This is because cars coming out of Bobbin Head are giving bikes a stupidly wide birth.....and the speedy cyclist coming down the hill has no time to react = need an ambulance.

I go reasonably fast down there but I am always surprised by the number of people who really crank it........its so unnecessary in the whole scheme of things, Like BNothling says....work, hospital family and training are all comprimised.

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