PDA

View Full Version : Traction, the Limit



F5 Dave
27th July 2006, 11:47
A friend interested in vocalising opinions for the purposes of training etc asked me the question about the limit of traction & how to recognise it & teach it. He has a far better knowledge of this, but is always listening.

I am no expert (& am not pretending to be) but I figured if I wrote this spiel I might as well cut & paste it here as well.

Limit of traction
I used to think about this. On my ride to work when I lived in Karori I went the same way. I rode at what I thought was a safe & brisk pace. I came down this incline to meet up with the main road. It was coarse chip, lots of traction, but downhill & off camber to meet the main road which was also downhill. As I became familiar I used to brake fairly heavily to that intersection.

I then began to ask myself, what if I needed to stop faster than I was already braking? What if someone pulled out of a driveway or kid ran across the road? Could I brake harder? So I tried.

Front end lose, tyre went sideways, let off the brake, banged foot on ground & re braked. Made it, but wouldn’t want to ask to get off that a 2nd time. Learnt that what I had felt was the limit was actually the limit (bearing in mind I had a calibrated sense from practising braking). What I learnt was actually I was travelling too fast if something out of the norm occurred.

I later tried the same thing downhill (Raroa rd) in the wet. Again the good lord smiled on me again & I didn’t ditch it. Again I was travelling at a safe speed on a wet road – as long as I didn’t need to brake to avoid someone else turning across my path or stopped around a blind corner with someone coming he other way. Learn the feeling of traction from braking practise & believe in it. Ask yourself the question ‘What would happen if? Can you do anything about it?’

I have ridden with people that would come acroppa if, say up the Pie-cock hill they encountered a broken down car that had stopped around a tight corner.

‘Have to be able to stop within the visible distance’ means more than most people think.

Early on I had experience racing that I was on the limit & I knew I was ‘cause I would get slides & occasionally fall off in certain corners - you could feel it.
But someone would come sailing past me much faster in complete control. How did they do it? Better tyres? Better bike? Well in some cases yes.

But one of the main things is that you need a stable platform to enter into a corner. The traction you use up braking, then letting off the brake & turning in while the front end is still trying to work out if it is compressing or rebounding uses that front tyre to the limit. If it doesn’t have those confused demands then it has more traction to spare.

Trying to keep up with a mate is for many like a panic situation where you don’t have the time to think about your riding, you just end up arriving in corners faster than you want so you compensate with more braking, thus a less stable platform.

Technology:
Better bikes, suspension & obviously tyres help. But you only have to go on a group ride to see someone on a flash bike crash it. Kiwibiker always has stories of people binning bikes. They aren’t a group of crashers more than any other group, they are just a large amount of people on bikes.

So I don’t know that anything has actually changed with our better bikes. That doesn’t make sense, they are much safer performing. Maybe what has changed is it has just increased the speeds we have accidents at?
But gravel on the road while banked over will slide a modern tyre out as quickly as a 20yr old one. Can you change line at a faster pace

I would say that braking practise on all surfaces teaches you a lot of transferable skills when it comes to sensing traction limits.

Wasp
27th July 2006, 15:13
Interesting read and something I've been thinking about lately too.

Thanks for that! :rockon:

beyond
27th July 2006, 15:38
Traction limits is a real techie subject. You need a degree in physics to get right into it but so many factors come into play.

Weight of the bike and rider, type of tyre, speed and suspension, riding lines, road surface and so much more. So yeah, it's a good thing to practice your braking on different surfaces as it gives an idea of what you can get away with.

Having seen many riders going about their business, me included, I can say that very few of us leave much room for error when on a good blast through the twisties. Bikes have got a lot quicker, handle better, stop better but have you arriving at corners at far greater velocities than they did 20 years ago.

F5 Dave
27th July 2006, 15:57
What I didn’t put in the above drivel but eluded to was I was at the time (erm, like a lonnng time ago) involved in rider training so was constantly practicing my braking + in racing you often are too -more so for hairpins.

One thing that amazed me was how much better the students were at braking after the exercise. Where they had been afraid they were more confident (a mixed blessing but a useful tool in the right hands), but mainly they had pretty much ½ their braking distance. More in some cases!

Later on helping out running a bunch of more experienced riders through the braking test the same sort of improvement could be witnessed in many if not most. These were people who regularly ride at 100k (or more) but some were not prepared to test braking from there, others were just slow to pull up.


That feeling of braking on the maximum juddering front wheel struggling to retain grip & adjusting the braking force.
Once learnt that feeling can be practised in front of the TV or whatever. DIY Virtual Reality.

The same sort of traction loss feeling is experienced rear wheel through the seat & pegs. Different receptors but kinda the same sort of feeling. Sort of. . .

Freakshow
27th July 2006, 16:02
:yes: Thanks guys that is some interesting reading!:yes:

vtec
29th July 2006, 11:25
Yep, went out to test my rear slide throttle control yesterday in a carpark. Should have put my knee sliders and leather on, but couldn't be bothered. But I found that without the ability to put a knee on the ground, I was struggling to gauge my ground clearance when purposefully trying to slide the rear of my CBR. If you want to know the limits, you have to exceed them a few time before you know the feeling of where that limit is. I regularly practice hard braking, and throttle slides on my bikes, and that is why I've been able to get into racing and be successful immediately. Also, knowing the limits of your bike does let you know how much margin of error you need to leave for road riding.

Also, when testing the braking abilities of your bike. You are inevitably going to get a front end lock up. The more you do it, the quicker you are able to react, and get off the brakes and back on. The problem is, that when you are learning to control a front end lock, you have a very good chance of being unable to recover it at some stage, and causing yourself a lowside.

I have an average rear tyre on my CBR250, which makes for relatively easy slides in the dry. On my racebike CBR250 I have GPR70's, which is harder to slide, but if you hit a deviation on the road surface, it can very easily be put into a slide. Like when you are turning right at traffic lights, the cars wear grooves into the road surface, so it is easy to get rear end slide coming out from lights, but when you hit the other side of the curved groove, the tyre gets way more traction and can boot you out of the seat. Luckily, I've still never highsided.

Anyway, the only way to learn the limits of traction is to push those limits.

mikey
29th July 2006, 13:31
I have ridden with people that would come acroppa if, say up the Pie-cock hill they encountered a broken down car that had stopped around a tight corner.



probably jinxing myself, but thats not what ridigns about,

if your rodeeverywhere with chicken little mentalitly,
THE SKY IS FALLING THE SKY IS FALLING it would take hours to get anywhere, not be enjoyable and cops would pull you over for going to slow.

ride hard. ride fast. you'll pay the rent every now an then but you get palces quicker an have more fun doing so

thought at manfield i could only clock up a 2.09 last weekend so arent to be giving anyone lectures about riding hard...... did grind a hole through my leathers an knee cap doing so though.

Falconer
30th July 2006, 19:59
I almost got caught while cruising at 90 ks on a straight level road when the engine revs went up, I throttled of to a violent tank slapper. Tyres etc not at fault just an unpredictable road surface. When racing an oil flag would be out but on the road you must ride as if all surfaces are unproven.:shit:

trumpy
30th July 2006, 20:28
..... but thats not what ridigns about,.........ride hard. ride fast. you'll pay the rent every now an then but you get palces quicker an have more fun doing so.........

Crap. Each one of us must find their OWN biking Nirvana. To suggest that somehow my biking experience is limited because I ride a bit slower (...okay, okay, a LOT slower....) than you is arrogant as you place your own assumptions and presumptions on my experience of life.
At 53 I have done many high risk activities and successfully at that. In fact at times I wonder how I ever survived my "youth". As I have gotten older I have become rather attached to life and living and wish to continue to do so for a while yet. This doesn't mean developing "chicken little syndrome", but, FOR ME, means that I am somewhat circumspect about the decisions I make when on my bike. This is possibly also dictated by a certain lack of skill on my part although admittedly, as my skills improve the decisions I make do change.

Sorry no offence intended mate.......just the ramblings of an old fart....

F5 Dave
31st July 2006, 10:32
VTEC. I am not advocating deliberately finding the edge of traction on the road, that is what the carpark, or better yet the grass or dirt is for. For road riders I wouldn’t advocating deliberately finding the edge of traction by inducing rear wheel slides either, well not on tarmac. Gravel roads are good for getting the start of the feeling & how to correct, but you are upright.
-Buy a dirtbike, shit we had an awesome ride yesterday. With the rear brake you can control how much wheelspin you get exiting corners. Maybe a thumb brake for Right handers would be cool.

Just a point on practising braking. The number one thing is not to look down. To have your eyes focused pretty much on the horizon your brain & balance can correct the bike a lot easier. This is a task to practise. You will also be scanning for an escape route. -You WILL NOT be target fixating. Right? Good.

You should be able to get to the point of locking by progressively squeezing & as it happens reducing & reapplying. I’ve seen hundreds of people do this on practise runs & never seen anyone drop their bike doing it.


Mikey, I’m glad that like all 16yr olds you are immortal & thrills are only achieved by risk taking in an uncontrolled environment. However Natural Selection is a harsh mistress. The sanctity of the human gene pool depends on it.

vtec
31st July 2006, 17:07
By all means dave, advocate what you like. I was just letting you know how I work it out, but as you have put, it's not for everyone testing the traction limits by powersliding. But it is important to test traction limits by going hard on the brakes, but you have to know when to let off. Not everyone knows when their bike locks up the front wheel, and thus they don't back off the brake, and thus they bin it.

F5 Dave
31st July 2006, 17:35
Your method is valid, I just don't want to scare people off trying.

I think if you practise braking from a low speed & then work your way up you will learn the feeling of the brake locking up & how to release/reapply. Many people are scared of emergency braking, esp if you ask them to do it from a high speed, but will ride at the open road speed limit.

mikey
31st July 2006, 18:51
Mikey, I’m glad that like all 16yr olds you are immortal & thrills are only achieved by risk taking in an uncontrolled environment. However Natural Selection is a harsh mistress. The sanctity of the human gene pool depends on it.......
THE SKY IS FALLIGN THE SKY IS FALLING


HMM KFC ANYONE?

Motu
31st July 2006, 20:05
I'm not sure brake testing the limit of traction is a valid test for traction limits in cornering and power application - do you.....why?

vtec
31st July 2006, 22:03
I'm not sure brake testing the limit of traction is a valid test for traction limits in cornering and power application - do you.....why?

It's not, but most people are better off not going near the edge of their cornering traction limit, cause they will crap their panties, and possibly drop it due to exceeding the comfort zone. So they are just better off sticking to making sure they know how to haul their bikes to a halt pretty quick. Although, me personally, I like to use my small size and relative nimbleness to avoid dodgy situations as opposed to jumping on the brakes.

F5 Dave
1st August 2006, 11:02
HMM KFC ANYONE?
That greasy shit will kill you too.

Rossi Gal
1st August 2006, 18:08
eww KFC is yucky!!!

Rossi Gal
1st August 2006, 18:22
...... did grind a hole through my leathers an knee cap doing so though.


Yeah ya fucking twit!! get some sliders if ya gonna keep doing that shit!!..and please tell me you got that thingy changed on ya knee??!! eww :sick: lol

mikey
1st August 2006, 22:10
That greasy shit will kill you too.

tastes good though.

more weight i got the more stable my bike will be, less risk etc

see i like to minimise risks when i can

oh an yeh i sraped off all the globs of puss an sprayed fly spray on it cause i couldnt find any meths. stung a bit but hopefully got the infection.

Rossi Gal
1st August 2006, 23:13
tastes good though.

more weight i got the more stable my bike will be, less risk etc

see i like to minimise risks when i can

oh an yeh i sraped off all the globs of puss an sprayed fly spray on it cause i couldnt find any meths. stung a bit but hopefully got the infection.
you're a strange boy you are.....flyspray..?!

Zapf
1st August 2006, 23:32
flyspray..?! think insect replent might be tasty.... for him.