Cornering Confusion

[AQAJR]

Greetings,

 

Can someone please shed some light on a cornering question, specifically the weighting of the front end in the corner? The issue has been pretty popular this racing season as Casey Stoner has blamed his two crashes in MotoGP as possibly being caused by the thought that he isn’t getting enough weight onto the front tire when cornering thus he is losing the front end.

 

I’m a bit confused by that as my thought was that one of the reasons for rolling on in the corner was shift the weight from the front back onto the rear and NOT to overweight the front. Granted those guys are dealing with different types of forces and equipment, I would think the physics of it would remain.

 

Thanks.

Albert

 

 

[khp]

Hi Albert,

 

Yes, confusing indeed! I'll try to explain it to the best of my limited understanding and ability:

 

I think we can intuitively understand that OVER-weighting the front tire can make you crash: the weight + cornering forces are simply bigger that the friction available - poof, and you're down the road.

 

Now, the observation here is that Force(used) must always be lower than the Force(friction, available). For the sake of the discussion, let's assume we the available friction is 100%. In the case of over-weighting/braking/leaning/turning, the used forces is larger than 100%.

 

But the available friction is dependent on how much weight you apply from the tire to the tarmac. If you lift the front wheel (ie: do a wheelie), you have 0% friction available on the front tire. A less drastic situation is that you're riding over a crest or accelerating hard - here less than 100% friction is available, so applying the front brake may lock up the wheel and a very fast turn-in could require more friction than available, and thus causing a crash.

 

I have seen at least two people crash from failing to letting the front tire settle before applying the front brake

One of the turns on Ring Knutstorp is located on a crest (and is blind). Going over that one at high speed is ... entertaining ... and has definitely had it's share of crashes over the years!

 

Hope this helps understanding why too little weight can also be a bad thing!

 

 

Kai

[AQAJR]

Thanks Kai. I do see your reasoning. It now seems we work quite the balancing act when trying to determine and feel the appropriate amount of pressure to negotiate a corner.

[Fajita Dave]

Comparing any equipment that we can get our hands on can't really compare to what the Moto GP guys have. Their tires are completely different from what we can get our hands on.

 

Most of the tires that we can buy heat up quickly without even being ridden hard or loaded much. Thats what they are designed to do so you almost always have good grip from the very start. Moto GP tires are made to handle enormous loads and only build enough heat to get traction when heavily loaded. They also run very low tire pressures so the more they load a tire the larger the contact patch gets (which happens with our tires too but not to the same extent).

 

I'm not a tire engineer so I can't really tell you why they need to load the tires so much to get any grip out of them and I could also be completely wrong. Still comparing their equipment to ours is like comparing apples to oranges. Paying more attention to how the AMA Superstock racers use their tires would be much more use full if your trying to learn more about it.

[fossilfuel]

Greetings,

 

Can someone please shed some light on a cornering question, specifically the weighting of the front end in the corner? The issue has been pretty popular this racing season as Casey Stoner has blamed his two crashes in MotoGP as possibly being caused by the thought that he isn’t getting enough weight onto the front tire when cornering thus he is losing the front end.

 

I’m a bit confused by that as my thought was that one of the reasons for rolling on in the corner was shift the weight from the front back onto the rear and NOT to overweight the front. Granted those guys are dealing with different types of forces and equipment, I would think the physics of it would remain.

 

Thanks.

Albert

Hi Albert,

I am in no way qualified to answer your question...but I can't help myself. The important thing to remember is that when you are in the corner the rule of thumb is balancing the weight of the bike's suspension 40% front and 60% rear. And you shouldn't be rolling on the throttle but applying maintenance throttle to balance the suspension where it can work the best. Good body position and throttle control are important.

Something else to consider is rider inputs that are acceptable at different parts of the corner at entry and exit. You start the corner perpendicular to the track and increase your angle to maximum then gradually back to perpendicular on exit. Gradually as you enter the corner the braking becomes more and more of a risk because it upsets the balance of load and suspension and the same on exit as applying the throttle becomes less of a risk at less lean angle on exit. So there is and area of the corner that is a sort of danger zone for applying to much brake and applying to much throttle.

My motorcycle is for racing and tracks only and it is set up very stiff. Do I worry about loading the front under normal racing conditions? No. It never enters my mind because I practice the tenants that were taught to me. Now, if I am racing at Barber going into turn one at 100mph, get bumped off my line and have to apply brakes to keep from going in the gravel then yes, I do worry about the front.

I have had a few crashes that I have experience that were self inflicted...and I can think back and say that I was going against what I was taught, against the basic rules that I was taught at CSS. Nothing can replace instruction and practice and nothing can replace the experience of finding your limits on the track.

[Fajita Dave]

Well it seems like Casey Stoner and the Ducati team don't understand how MotoGP tires worth either .

 

http://www.motorcyclenews.com/MCN/sport/sportresults/MotoGP/2010/June/jun0310-mugello-motogp-stoner-to-test-old-forks/

[faffi]

Another weird front end issue, about Simoncelli in today's race:

 

He was pushing de Puniet when he let off the

brakes too early and the front end washed away on

the 14th lap.

 

Can you let off the brakes too early? Or do they mean too quickly?

[khp]

Another weird front end issue, about Simoncelli in today's race:

 

He was pushing de Puniet when he let off the

brakes too early and the front end washed away on

the 14th lap.

Can you let off the brakes too early? Or do they mean too quickly?

The only explanation I can imagine is that they've set up the front end to rebound very quickly, and that would take the weight off the front end, causing the wash-out.

 

Kai