Rider Inputs + Fast Corners (Track)

[rikker]

Hi there.

So, I'm struggling to accomplish every fast 90 degree (L) corners and looong ones as well, which doesn't need any braking inputs, but you still can drag your knee because steep lean angles must be reached.

So here we go: when I get to the corner on WOT what should I do with the throttle?

A ) chop the throttle and coast thru the corner using engine braking till apex and then follow throttle rule?
B ) close 1/2 throttle (imagine a Motogp green throttle graph at half) and attack the corner?
C ) keep it WOT and countersteer?
D ) another alternative...

And how should I lean into ir?

A ) quick flick?
B ) sorta lazy steer?
C ) body steer?
D ) ?

Thank you.

[YellowDuck]

This is going to be fun....

 

From my (amateurish) perspective, the answer is probably most often B, but sometimes A, depending on the corner. It is fairly uncommon to have a corner where you need to go to zero throttle, but still don't need any brakes. Corners that you just need to roll off a bit to set entry speed but then get back on the throttle pretty quickly are way more common. I wonder if some of the corners that you think require zero throttle before entry are actually ones where you could be going deeper, using the brakes for a bit then turning harder. I know I have done the chop, coast, turn thing in a few corners when learning a layout, but as I pushed my times down I got to be WOT longer and then on the brakes before turn in.

 

C - WOT and countersteer....I'm gonna say no to that.

 

As for the steering input, personally I pretty much always steer it hard. There aren't that many corners (slow ones anyway) where quick flick doesn't work for me. The exception would be long, slower corners at the ends of high speed straights, where I tend towards a slightly slower turn in with a lot of trail braking.

 

Okay, now I will shut up and let someone who actually knows something chime in.

[Hotfoot]

Have you tried going through the whole corner at WOT? If so, were you able to get the bike turned, and get to and stay on your desired line?

 

Is there a particular problem you are trying to solve in these corners? Is your bike not going where you want it to go or is there a handling problem?

 

The reasons for rolling off the throttle on entry include setting your entry speed and getting the weight on the front end to quicken the steering. The reasons for good throttle control are many but they include maximizing traction and getting the suspension in the ideal range.

 

If the corners are such that you can enter WOT and get the bike turned successfully and it holds your desired line, then there is no real necessity to roll off - this is a fairly common scenario on lightweight bikes on big tracks. However, if entering at WOT causes you to run wide, or triggers SRs causing errors like tightening on the bars, etc., it may not be practical and you need to look at using your roll-off to set a proper entry speed that is manageable for you.

 

Quick flick versus a slower turn will depend on the corner - is it more of a priority in THAT corner to go IN fast or come OUT fast? If the corner has a wide, high speed entry after a straightaway it might be useful to use a slower turn in and trail brake (or just roll-off and let the slow turn in scrub speed) to preserve your straightaway speed as long as possible and prevent being passed on entry. But if the corner is tight and leads ONTO a straightaway, quick turn may be better so you can get on the gas as early as possible for your drive. Every corner is a little different so it is best to ride to your own strengths and use a laptimer to actually measure which works better for you in a given turn.

 

If there is a specific problem you are experiencing in a turn, post that up and maybe we can help figure out the cause and some solutions.

[rchase]

I don't have anything useful to add but this is a good topic. Owning a rather underpowered bike myself I'm looking forward to the answer here.

[rikker]

Right now I'm trying to solve my BALLS problem! It's almost automactic: I'm hitting the brakes on every fast corner but then I see guys passing thru me like a rocket (and knee dragging).

 

So, getting my theoretical knowledge sharpen maybe can solve my fast corners issues.

I know every corner is a different history, but let's start with the basics, baby steps:

 

1) on a 90 degree 100 kmh corner how should I approach? Roll off the throttle, keep it, quick turn, and then throttle controle rule?

[YellowDuck]

Again I will jump in with amateur advice.

 

I don't think there is one answer to your 90-degree 100-kph corner question, because it depends if you are approaching the corner at 110 kph or 200 kph!

 

But yes the basic sequence you describe seems right. Just be sure that you are not adding throttle again until you reach your final (i.e. greatest) lean angle for the turn. Adding throttle + lean = bad juju.

 

Personally most (all?) of my turning is done on fully closed throttle, even if it is closed only for a brief instant. I guess if you have room to be on partial throttle for any distance, then you could have held WOT longer, then closed the throttle before turning. I am sure there are exceptions to this (e.g., quick chicanes) but it seems pretty logical. Also I think it might be easier to get used to the consistent way the bike works while turning on closed throttle. Also, myself, I am probably too much of a spaz to maintain a consistent throttle application (other than zero or WOT) while turning the bike.

[Hotfoot]

I agree with all of what YellowDuck said above. If you've taken Level 1, check your Two-Step timing to make sure your eyes aren't stuck on your turn point - that can mess up your sense of speed.

 

There is a section in A Twist of the Wrist II called "Discharging" that gives a useful procedure for gradually increasing entry speed without overwhelming yourself.

[rikker]

Thanks guys. Great advice YD.

[csmith12]

I only got one piece of advice for you. Ask yourself, does the corner look pinched? ie, the corner look closed up without enough room to run wide during entry. On my many of my local tracks, some corners look pinched as the true width of the exit is sorta blind. I kick myself every time I go through and say... wtf, I could have went faster. Do you have a good exit reference point for these corners? Trust... it does wonders!

[rikker]

No, it is not pinched... well, I think I'll give a shot on rolloff till half throttle + quickflick next trackday. Let's see how it handles.

 

My biggest fear is---like our mate said---to run wide/out of track or washout the front tire due lack of load.

[rchase]

So. A question. When you are WOT heading into a corner do you have revs left to make it through the corner?

[YellowDuck]

WOT means wide open throttle, not redline. So yes you might well have revs left depending on how close to redline you were entering the corner.

[rchase]

WOT means wide open throttle, not redline. So yes you might well have revs left depending on how close to redline you were entering the corner.

 

Appreciate the helpful explanation. I was actually asking the original poster how many revs they had left. I guess I could have worded my question a bit better to prevent confusion.

 

Mostly just curious. As well what kind of bike is this? What works on a 250 would probably not work well on a big 1L monster.

[Hotfoot]

 

WOT means wide open throttle, not redline. So yes you might well have revs left depending on how close to redline you were entering the corner.

 

Appreciate the helpful explanation. I was actually asking the original poster how many revs they had left. I guess I could have worded my question a bit better to prevent confusion.

 

Mostly just curious. As well what kind of bike is this? What works on a 250 would probably not work well on a big 1L monster.

 

 

Absolutely true (that WOT on a 250 would be considerably different than WOT on an S1000)! Also, a fine point but sometimes becomes important - your revs will be different leaned over than straight up and down due to the difference in the circumference of the tire.

[rchase]

Hotfoot. Hate to put you on the spot but could you elaborate a little on the RPM variation that you get leaned over? I read in one of Keith's books the finer points of gearing for a WOT turn at a specific track. I understood the concept but it still seemed like some kind of dark magic he was explaining.

 

I have run into this "gearing change" myself due to some visual issues I had with corner entry. I solved the visual issues but experienced that "wait a minute why the heck am I going so darn slow" because of that gearing change due to the lean. Understanding this a bit better would be quite helpful.

 

External links are MORE than acceptable if you have them.

[YellowDuck]

(Hopefully this is not another Captain Obvious post...)

 

If you are leaned over right at the edge of the rim, the effective tire diameter would be 17 inches (i.e., the rim diameter). Of course you can't be there because the tire has some sidewall height, plus you need some contact patch beyond the sidewall, so let's say 20 inches. In other words, on a 17-inch rim, leaned right over, the part of the tire you are using has a diameter of about 20 inches. Its diameter determines how quickly it must turn at any given bike speed (actually, its circumference, but circumference is directly proportional to diameter so same thing).

 

Straight up and down the effective tire diameter is a lot bigger. For example, for a 190-section 55-profile tire on a 17-inch rim, the center of the tire is about 4 inches proud of the rim so that is 8 inches more diameter. So, neglecting tire flex, straight up an down you have a 25-inch tire diameter (17+ 8), but leaned over it is only 20 inches. So at any given rate of wheel rotation, straight up and down the wheel travels 25/20 = 1.25 times as far as when you are leaned over. That's a big difference. If you were turning 10,000 rpm when you turned in and didn't change your speed at all as you approached full lean (?!?) you would be turning 12,500 rpm by the time you were at full lean. The bike is covering the same distance in the same time, but because the diameter of the part of the tire in contact with the road is smaller, the wheel has to turn faster to cover that distance. Since the gearing hasn't changed, that means engine speed has to increase to compensate.

 

Hopefully I got the math and geometry right. But that's just theory. In practice it almost never works like this because you are usually turning in on zero throttle, and just the act of turning the bike slows you down considerably. So even though rpms might rise it won't be as extreme as what I just calculated.

[rchase]

Yellowduck. Thanks for taking the time to explain that a bit more. Not "Captain Obvious" at all.

 

Some extremely helpful information there that made me think about some of the other "wrinkles" of gearing. One of the reasons we do the "pick up" for our drive is not only is to get us better traction but also better gearing for acceleration on the straight. I never really thought of that before now.

[FieryRobot]

Wow. I never thought about that. Super interesting!

[Hotfoot]

Great job explaining that, Yellow Duck!

[tmckeen]

One of the reasons we do the "pick up" for our drive is not only is to get us better traction but also better gearing for acceleration on the straight. I never really thought of that before now.

 

 

I'm not really sure I get what you mean here, generally speaking lower gearing results in better acceleration, but standing the bike up effectively raises the gearing doesn't it? I know a larger sprocket in the rear lowers your final drive gearing, but increasing the diameter of the drive wheel would result in greater distance being covered per RPM which would be taller gearing would it not ?

[YellowDuck]

That's what the physics say. Larger effective tire circumference = less rear wheel torque = less acceleration.

[rchase]

Hmmm. I always seem to screw up the minor details. It sounds like I have that reversed. You would loose acceleration but gain the ability to reach the bikes top speed. Of course all dependent on the way the bike was geared.

[tmckeen]

everyone gets things bassackwards from time to time

[rchase]

Ain't that the truth.

[ScrmnDuc]

That's what the physics say. Larger effective tire circumference = less rear wheel torque = less acceleration.

= less of a chance for the rear tire to "spin up" = less chance for a high side.

 

If you enter a long high speed turn that requires wot and your at max rpm/rev limit in top gear which throttle rule have you just violated as soon as you lean the bike over, and why?

How would you correct this?

Bonus question: Which book and what scenario covers this?