Lowside on a right turn

[tzrider]

The front has far more traction with a very small amount of brake squishing the tire than it does with throttle.

Well, yeah, but it's also demanding far more traction. If you had a front slide, what would you do with the throttle and/or brakes to try to save it?

 

[Gary856]

using the throttle to unweight the front tire does not decreases any cornering forces that are holding the tire in the turn. the rider must start to exit the corner for cornering forces to decrease.

Isn't using the throttle to unweight the front tire more about adjusting front/rear balance, i.e., shifting more of the cornering load to the rear to reduce the load at the front, a trade off between a front slide (harder to manage) vs. a rear slide (easier to manage)?

 

[stangmx13]

I rode two up withe Ken Hill last week. I was scared to death. I KNEW there was no way the front tire could endure the amount of braking and force on it, right up to the apex of the corner. At the end I was just enjoying the hell out of the ride.

That was with street tires, btw, Pirelli Corsa.

he did the same to me

Well, yeah, but it's also demanding far more traction. If you had a front slide, what would you do with the throttle and/or brakes to try to save it?

is it "far" more traction? my experience makes it feel like the proportion of used traction is actually smaller when squishing the tire. so ya, u are using more grip, but uve created more grip than u are using.

id reduce either throttle or brakes by a small amount to attempt to save a front slide. id also do other stuff w/ my body, but thats not what u were asking.

 

[stangmx13]

Isn't using the throttle to unweight the front tire more about adjusting front/rear balance, i.e., shifting more of the cornering load to the rear to reduce the load at the front, a trade off between a front slide (harder to manage) vs. a rear slide (easier to manage)?

how can the cornering load shift? this idea is making the assumption that a motorcycle can go from a 50/50 cornering force on both tires to 40/60 cornering force and somehow still make the corner. from a physics standpoint, some amount of force needs to be pushing the tire in the corner. otherwise the tire would just go straight, ie ud crash. for a given turn at a given speed, that force pushing either front or rear tire cant just disappear. IMO, 40/60 doesnt really make sense. the front tire would turn less and the rear tire would turn more. perhaps this is somewhat possible due to geometry changes from getting on the throttle, but i seriously doubt the effect would be that large.

spinning the rear tire does change the dynamics of turning a motorcycle a lot. if u are spinning the rear, ull need less lean angle and will have less load on the front tire for all corners. but up to the point of spinning the rear, it doesnt make sense to remove load from the front tire. the OP didnt spin the rear and most street riders wont ever, so this part doesnt apply that much.

 

[afm199]

Well, yeah, but it's also demanding far more traction. If you had a front slide, what would you do with the throttle and/or brakes to try to save it?

Depends. If there's room I'd let it run out.

 

[tzrider]

Depends. If there's room I'd let it run out.

I would too, but would you ever increase brake pressure?

 

[afm199]

I would too, but would you ever increase brake pressure?

I would not increase front brake pressure, the tire is already exceeding its traction limit. I would increase rear if I had time and remembered and didn't hit the telephone pole or the rider next to me.

On the other hand, if I had the front brake already on slightly, the front almost certainly would not have started sliding. That bit of brake pressure done early in the corner and held to apex absolutely increases traction.

 

[tzrider]

On the other hand, if I had the front brake already on slightly, the front almost certainly would not have started sliding.

I'm hearing that a lot these days, but most of the race crashes I'm seeing are on the brakes in corner entries. It's still true that riders almost never lose the front while on the throttle.

 

[Ahab]

I'm hearing that a lot these days, but most of the race crashes I'm seeing are on the brakes in corner entries. It's still true that riders almost never lose the front while on the throttle.

Sure? I think I have seen it twice.

 

[tzrider]

Sure? I think I have seen it twice.

Wouldn't say that if I wasn't sure. It's not to say it's impossible but it's rare and it's not the cause when it does happen.

How many times have you seen someone lose the front on the brakes?

The reason I bring this up isn't to invalidate the technique of entering a corner on the brakes, but to suggest this crash was caused by the rider being on the throttle is a big stretch. Nobody in this conversation is going to say that they would try to save a front slide by applying the brakes, but getting on the gas can save a front slide.

 

[afm199]

I'm hearing that a lot these days, but most of the race crashes I'm seeing are on the brakes in corner entries. It's still true that riders almost never lose the front while on the throttle.

I'm not sure how you draw that conclusion. Most crashes are corner crashes, no doubt. Entry? Ehhh, The last two I remember were exit, my last three have been exit. I don't think there's any statistic to support that. Max lean and throttle is still the worst combination.

Nor is it true most riders never lose the front while on the throttle. That's how Marquez crashed last race at Silverstone. That is a saying I consider and adage, not true.

 

[stangmx13]

The reason I bring this up isn't to invalidate the technique of entering a corner on the brakes, but to suggest this crash was caused by the rider being on the throttle is a big stretch. Nobody in this conversation is going to say that they would try to save a front slide by applying the brakes, but getting on the gas can save a front slide.

are u sure? if a rider chooses to throttle out of a front slide, you are sure that the largest contributing factor to saving it is the fact that the rider accelerated?

what if the rider only increases throttle by 5%, instead of a spin-inducing handful? what if their bike is setup so that the rear suspension squats a ton on the throttle instead of staying neutral or even extending like a well-setup sportbike?

IMO, there are more than a few circumstances that would make getting on the gas to save a front slide a really bad idea.

 

[latindane]

Depends. If there's room I'd let it run out.

Sorry for the ignorance; what do you mean by letting it run out?

 

[tzrider]

Nor is it true most riders never lose the front while on the throttle. That's how Marquez crashed last race at Silverstone.

Do you mean this crash?

[youtube]MfBkI8iUIYE[/youtube]

If so, he crashed before the apex and the throttle is closed, engine note falling.

are u sure? if a rider chooses to throttle out of a front slide, you are sure that the largest contributing factor to saving it is the fact that the rider accelerated?

what if the rider only increases throttle by 5%, instead of a spin-inducing handful? what if their bike is setup so that the rear suspension squats a ton on the throttle instead of staying neutral or even extending like a well-setup sportbike?

IMO, there are more than a few circumstances that would make getting on the gas to save a front slide a really bad idea.

I can't account for every what-if you can think of, but you haven't said anything above that illustrates how rolling on would make a front slide worse. It is possible for a rider to carry a hopeless amount of speed into a turn and push the front by over accelerating. You just about never see people do this.

You've said earlier that rolling on doesn't reduce cornering load at the front, but that's not really true. If the bike is leaned over, when you screw on the gas the torque at the rear is not only pulling the front wheel upward, but inward too. The amount of "up" vs. "in" is a function of lean angle.

This doesn't get us any closer to helping the OP understand how he may have crashed, but I very much doubt his being on the gas was the cause. And once the slide starts, rolling off or braking is a good way to make it worse, almost every time.

 

[Ahab]

^^^
Looks more like the rear came around and then high side?

 

[stangmx13]

You've said earlier that rolling on doesn't reduce cornering load at the front, but that's not really true. If the bike is leaned over, when you screw on the gas the torque at the rear is not only pulling the front wheel upward, but inward too. The amount of "up" vs. "in" is a function of lean angle.

i was waiting for u to chime in on that paragraph. i totally missed that part of the vector. that changes things some.

at 45deg assuming a coefficient of friction == 1, cornering force is equal to normal force. if one was able to wheelie at that lean angle, the wheelie vector's vertical and horizontal components would also equal the other two forces. however, at any smaller lean angle, the reduction in normal force and friction will be greater than the extra cornering force u get from the wheelie. so ull lose grip more than u gain cornering force.

so how does that apply to actual riding... it seems like it affects avg riders more than skilled riders. if u apply moderate throttle on corner exit, not enough to spin or fully wheelie, and still ask the front tire to turn the bike, u are only adding more risk.

This doesn't get us any closer to helping the OP understand how he may have crashed, but I very much doubt his being on the gas was the cause. And once the slide starts, rolling off or braking is a good way to make it worse, almost every time.

what do u propose as the largest contributing factor for the OP losing the front right at the apex while off the brakes and on the throttle?

 

[tzrider]

i was waiting for u to chime in on that paragraph. i totally missed that part of the vector. that changes things some.

at 45deg assuming a coefficient of friction == 1, cornering force is equal to normal force. if one was able to wheelie at that lean angle, the wheelie vector's vertical and horizontal components would also equal the other two forces. however, at any smaller lean angle, the reduction in normal force and friction will be greater than the extra cornering force u get from the wheelie. so ull lose grip more than u gain cornering force.

so how does that apply to actual riding... it seems like it affects avg riders more than skilled riders. if u apply moderate throttle on corner exit, not enough to spin or fully wheelie, and still ask the front tire to turn the bike, u are only adding more risk.

The amount of throttle roll-on should depend on where you are in the turn and what you're trying to do. The portion of a turn where riders speak of 'maintenance throttle" is a place where you're trying to preserve the speed you have, stabilize the bike and achieve weight distribution appropriate for each tire. The acceleration is slight, like a top gear roll-on on the freeway.

In this part of the turn, you'll be carrying the most lean angle and the effect we're talking about of positive throttle reducing the cornering load (in addition to weight) on the front will be most pronounced. Once the rider sees the corner exit, begins to stand the bike up and start the real drive, you're right that the throttle provides less relief on cornering load because the bike is more upright, but at the same time there are far lower demands on traction at the front anyway because the line is straightening out. People sometimes run wide by overdoing exit acceleration, but I can't think of a time where I've seen someone lose the front this way.

what do u propose as the largest contributing factor for the OP losing the front right at the apex while off the brakes and on the throttle?

At this point I don't know. From the OP's description, I have a picture in mind of some of the things he was doing, but don't feel like there is enough information. He stated that he'd begun the roll-on, but it's not clear whether the bike was actually accelerating. He hasn't mentioned the surface, so unclear whether that was a factor in starting the slide.

There are several possibilities but I can't say that one is more likely than another yet.

 

[dammyneckhurts]

Regarding the comments about crashes while on the throttle, a big contributing factor is that when people get on the throttle too soon the bike wants to increase it's turning radius. People compensate for this by adding more lean to keep the bike turning.

Saying that the addition of throttle does not reduce the size of the contact patch enough to cause a crash can be true..... IF we can assume that the rider is NOT adding more lean as they add throttle.

 

[stangmx13]

The amount of throttle roll-on should depend on where you are in the turn and what you're trying to do. The portion of a turn where riders speak of 'maintenance throttle" is a place where you're trying to preserve the speed you have, stabilize the bike and achieve weight distribution appropriate for each tire. The acceleration is slight, like a top gear roll-on on the freeway.

In this part of the turn, you'll be carrying the most lean angle and the effect we're talking about of positive throttle reducing the cornering load (in addition to weight) on the front will be most pronounced. Once the rider sees the corner exit, begins to stand the bike up and start the real drive, you're right that the throttle provides less relief on cornering load because the bike is more upright, but at the same time there are far lower demands on traction at the front anyway because the line is straightening out. People sometimes run wide by overdoing exit acceleration, but I can't think of a time where I've seen someone lose the front this way.

most the "shoulds" that u gave in this post are parts that we are unclear on from the OP. great riders accomplish all the "shoulds" and dont go down. great riders get themselves into stable situations or at least situations w/ good feedback where unwanted results are controllable. but this is a crash thread, so obviously something that should have happened to prevent a crash didnt.

At this point I don't know. From the OP's description, I have a picture in mind of some of the things he was doing, but don't feel like there is enough information. He stated that he'd begun the roll-on, but it's not clear whether the bike was actually accelerating. He hasn't mentioned the surface, so unclear whether that was a factor in starting the slide.

There are several possibilities but I can't say that one is more likely than another yet.

all this uncertainty is why we can still have fun discussing it

 

[tzrider]

all this uncertainty is why we can still have fun discussing it

True.