accelerating during a turn for maximum stability - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 59 (permalink) Old 12-03-2012, 10:12 PM Thread Starter
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accelerating during a turn for maximum stability

So every source I've read or heard says to accelerate through the corner.
The reason is simple - the rear tire is wider and can handle more load. Therefore - you must accelerate to transfer some weight to the rear to give the rear tire it's fair share of load.

even in the riding school to get my motorcycle license they say to brake, and once leaned, crack the throttle open and accelerate.

My question is this:
Once you get into long turns - 180 degrees or even 270 degree turns, if you enter the turn and flick the bike quickly to an aggressive lean angle and you start accelerating, what would keep you in the turn exactly? The more you accelerate, the faster you go, and the more lean angle required to maintain your radius...

If we take this one step further - a 360 degree turn non stop round and round - how can we possibly accelerate at the recommended .1-.2 G's? Eventually, we will go too fast to stay in the turn...

Maybe this is one of those beginner B.S. techniques?
When I first started tracking cars - it was the same thing. Accelerate through the corner. When I started getting faster and faster and got into actual racing, it was obvious that technique would never work because on long turns you can't accelerate forever - you'll either start pushing the front or oversteering - simply put, you end up going too fast during the turn.
With cars, when you start really going fast, you trail brake carrying loads of speed all the way right before the apex. That point is your slowest point. By no means - SLOW. Because you are going in so hot into the corner under light braking that the back end is always just about to give up... Once at the apex (a bit before depending on the corner) you get on the throttle and accelerate. The acceleration plants the rear end, but also rotates the car since the rear tires are on the verge of being overloaded and slip a little bit. That slip (slight oversteer) points the front towards the inside of the turn. (THIS is not a drift, it's very subtle and probably only the driver is aware of it through steering wheel feel).

Anyway, if I would drive a car and get on the throttle right as I turn, and I can accelerate through-out the long 180 degree corner and stay on the road it only means one thing - I'm loosing time. I could have carried more speed into the corner.

I'm inclined to think the same applies for bikes, but I'm new to all this so I thought I would ask.

Please - if you are going to be a prick, move on to the next post. I've posted here and alot of times people get nasty just because they don't like my question. When I posted that my handlebars turned in on me during a turn - 2 people told me to sell my bike and quit! WTF?

Also - I'm new and I don't know ****. But probably 90% of you also don't know jack! Just because you have an S1000RR doesn't mean sqwat! If you don't blip the throttle during braking and downshifting and don't carry some braking into the corner - even on a motorcycle, don't respond to my post. I don't want to hear what you say.
For everyone else - I'm happy to hear your explanations and opinions. I'nm eager to learn and listen.
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post #2 of 59 (permalink) Old 12-03-2012, 10:22 PM
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This may be an elementary response in comparison to what you are looking for, but I feel that the answer to this is very circumstantial. Depending on how gradual a turn is, after a certain point I cease to process the condition as a "turn", and consider it to be a gradual occurrence, and my riding adjusts as such.

So much of riding is about an organic feel, understanding, and relationship with your bike, and therefore definitive rules are a bit difficult to etch in stone, as riding conditions vary. In turns with definitive beginnings and ends into straightaways, perhaps the traditional method described is best, but extensive gradual turns may be considered and approached differently.

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post #3 of 59 (permalink) Old 12-03-2012, 10:24 PM
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I think the key would be to accelerate as quickly as the turn will allow. Making minute adjustments while in the turn. It is a very good question with the 360 degree turn. Continuing to accelerate doesnt seem possible.
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post #4 of 59 (permalink) Old 12-03-2012, 10:41 PM

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Cracking the throttle and accelerating can be two different things. Cracking the throttle can mean just achieving maintenance throttle. No longer decelerating but not yet accelerating. There are generally two types of turns. Entry turns and exit turns. The type will dictate your application of throttle.

On a long sweeper, you would brake going in, then generally go to maintenance throttle, and then at some point (at/around the apex) you'd begin accelerating. There are no absolutes. So if someone says you should "always" do "X"... they're full of shitt.

Not sure if that helps any...

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Last edited by 1000RR; 12-25-2012 at 11:31 AM.
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post #5 of 59 (permalink) Old 12-03-2012, 11:07 PM Thread Starter
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All the replies all helped alot. Especially that there are no absolutes and it's all corner and situation dependent.

I'm at the point where I'm just starting to learn how to go faster and I really needed to know what is desired for real speed and was is just there to keep us out of trouble.

I remember my very first track day in a car taking the school. In class they say - a car will only do 1 thing. Accelerate, turn, or brake. So they teach you to brake in a straight line, finish your braking completely, then start turning.

I wish they would have just said - "fast drivers brake and turn simultaneously, and they also accelerate and turn at the same time, but since you guys are new and don't have the proper car control - please brake in a straight line, finish braking - then turn...

It really makes me wonder on a slightly different topic - why is the front tire on a bike smaller than the rear. They obviously do this so that the rear can handle more of the traction, so under acceleration - the bike is 50/50. The front gets 150lbs, the rear gets 250 lbs. But since the rear is wider than the front - it equates to 50/50. So under acceleration - the bike handles beautifully.

In a car - this would be called a staggered setup. Most BMW's would have skinnier tires in the front than the rear. For practical track purposes - it's not a good thing. It's a formula for understeer (front end pushing). BMW has spent so much energy making a 50/50 weight distribution car, and ruin it by running skinnier tires in the front. The reason is simple - insurance. When a car starts sliding - most drivers automatically lift off the gas, and get on the brakes. During oversteer situation - this will cause a spin 100% of the time. During understeer - brakes are not as catastrophic - so BMW decides their cars to lean towards understeer. Get rid of the staggered setup on your BMW - and the car handles like a dream!

What would happen if a bike - which is 50/50 in weight distribution, would also have a square setup. 190 front and rear? Then you can go in very hot trail braking into corners without understeering, have amazing traction during maintenance throttle in the mid corner phase, and good acceleration because when accelerating - the front wheel is almost off the ground anyway - so who cares???

Just asking - i'm sure there is a reason well paid engineers at Honda, Kawi, Suzuki, BMW are all down with the staggered setups on the bikes - and my thinking about it is all wrong. I'd just like to find out why
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post #6 of 59 (permalink) Old 12-04-2012, 12:02 AM
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You have really thought alot about this...
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post #7 of 59 (permalink) Old 12-04-2012, 01:00 AM
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Naomkreif, you are correct about how modern cars are setup to understeer at the limit for safetl purposes.

Similar to cars though, on a bike if you're on a track and looking for quick laptimes, you'll find that you trail brake and corner at the same time up to the apex, and then let the throttle in as you're coming off the corner.
There's no magic formula though, and all corners are different but the basic principal applies regardless of the type of machine.

As for staggered setup, you need to remember that bikes and cars corner in an inherently different manner.
In an ideal car with 50/50 weight distribution, you want it to corner flat and the tyres should be as low profile as possible to avoid deflection to keep as much surface area flat on the track as possible.
With a bike however, you lean it into the corner. Therefore the tyres are relatively high profile and are designed to deflect while leaned over to create a contact patch.
The main reason that a thinner front tyre is used is to make the bike turn lightly into the corners. A fat front tyre would increase the roll radius and make the bike turn slower.
The main reason that a fat rear tyre is used (even though in general the fatter the slower the flop into the corner) is so that when the bike is leaned over that there is enough contact patch to be able to keep grip while under acceleration.

Last edited by Piper; 12-04-2012 at 01:04 AM.
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post #8 of 59 (permalink) Old 12-04-2012, 01:15 AM Thread Starter
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makes sense. So a the skinny front tire allows for a quick flick turn in, and then the wider rear tire actually handles the cornering forces.

Thanks for the reply!
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post #9 of 59 (permalink) Old 12-04-2012, 07:50 AM
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My thoughts:

rear tyre is fat so as to have a bigger contact patch for traction whilst upright - think that's right. On the front its a trade off for steering response.

bear in mind that the rolling radius of a bike tyre reduces went lent over, so some upwards adjustment in revs are possible due to this.

Cornering requires energy (some is lost due to wheel slip and deformation of the tyres and suspension) so extra fuel is required to maintain the same forward speed. Try going through a corner with the clutch pulled in, you will slow down a lot.

I suspect that most people say 'drive through the turn with the gas' for stability. Most newbies find cornering difficult, and this reduces the inputs to just one control. Most newbies are better on the gas then the brakes! Also, you are feeling for traction which should be done with the gas.

My old bike had a lot of drive chain lash and the off on throttle transition was jerky. This was bad for mid corner confidence. When I reduced to a slower entry speed and then drive it out with a positive throttle, it was much easier and therefore confidence grew a lot. I was able to keep a more constant radius and therefore judge the required entry speed much better. This created a positive spiral of improvement.

I would also say, that driving through the turn is useful when you on the corner exit. You are increasing the cornering radius as the turn opens into the straight, until the radius is infinite (ie, you are going straight). So for a 360 deg corner/circle, this doesn't apply and you reach maximum corner speed that the situation allows.
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post #10 of 59 (permalink) Old 12-04-2012, 08:01 AM
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u maintain throttle in a corner. or slightly increase it commin out of it. if u have that much room to increase ure throtthle ure either goig way to slow in the corner or u will lowside. the reason to maintain throthle is to not wash out the front in a corner.

edit: sorry for the typos cant work with touchscreen
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