Dirt Riding Vs. Pavement Riding

[chris modiano]

This question has been bugging me for so long...

 

How come dirt bike riders lean outside of the turn, pushing their bike down, while sport bike riders lean under their bikes, pushing it up, and dropping their weight low? I know dirt and pavement are much different, but this also comes into play with super moto racing, where you see people riding their bike motocross style, but on pavement.

 

Please enlighten me!!

[2bigalow]

Counter leaning a bike at slower speeds creates a tighter arc. At slower speeds, riders do not have the luxury of centrifugal force holding the bike up, so your weight needs to be over the bike's center of gravity to get it leaned over.

[2bigalow]

Not 100 percent sure, but I think fast dirt riders also use it for traction. Any fast dirt riders here that can confirm that?

[chris modiano]

This is the greatest forum on the internet... between this thread and the trail braking thread, I now know everything there is to know about racing a motorcycle

[Carl_T]

Not 100 percent sure, but I think fast dirt riders also use it for traction. Any fast dirt riders here that can confirm that?

 

I'm too old a fart nowadays at 62, but back in the day I rode smooth dirt track, then advanced to semi pro motocross when it was very light two stroke bikes, family stuff stopped further progression. Yes it is for traction. It is also very largely for something else that has not been mentioned as of yet.

 

When you get the bike sliding sideways as much as you can in the dirt, sitting on the high side of the bike lets the bike move a very long ways sideways underneath you before your chest/shoulder weight drags it down into a steeper lean from hanging to far off the inside (thus sliding out). That's WHEN you are planning on sliding good.

 

That's not so clear is it, so maybe approach it another way.

 

If you go in sitting up on the high side (outside corner of the seat), you push down with your knee on the tank (and countersteering in) leaning the bike under you (leaned more than your body). You've already got it sliding (brakes, then rear brake) and it will slide sideways a good bit now. If the bike slides a lot the bike moves SIDEWAYS under you as it slides, so maybe your shoulders are now lined up centered in line with the bike's lean (kind of like cops and road riders who don't like to hang off ride the street, in line with the lean). the bike is no longer pushed down under you but most of the pivot is done. You've pivoted in a short space, so you are now exiting. The front tire may or may not be on the ground much on exit as you pin the throttle and clutch heavy acceleration. You need more traction on heavy acceleration, so to help with that you shove the bars (not turn them, lift them up and shove them away from you) towards the outside of the turn to help stand the bike up a lot more for traction (you've also countersteered the bike to stand it up by aggressively turning the front wheel INSIDE more sharply during a part of the pivot). The bike stands up so much your shoulders are likely hanging inside the center line (like road racing hang off minus the arse) as you come out of the turn, most likely at full throttle or at the least on very heavy gas.

 

That's a sharp square off style turn, not using a berm or a long sweeper.

 

A motocross bike (especially when I raced) is very light and does respond to a rider's weight inputs more than a supersport would. If you rode the dirt bike into a sweeper where you planned on a rather large slip angle of sliding, and you started out hanging way off the inside road race style, you'd get the following. When you got your slide and the bike moved toward the outside of the turn on you a long ways, your contact with the bike would begin to pull on the bike trying to lean it further down into the turn because you were hanging off to begin with, so now you're hanging of a LOT more and pulling the bike down. That would be opposite of what's needed at that point. Especially at lower speeds, your body weight off to the inside pulling for a steeper lean as the bike moved away from you, would succeed in leaning the bike more, and result in a lowside. I've both watched and experienced this.

 

By sitting towards the outside and pushing the bike down under you, you create a situation where the bike can move a relatively long ways to the outside before your chest/shoulders (where a man's center of gravity is) are hanging off the inside, and you aren't likely to hang to the inside enough to pull the bike down. You probably will only be centered and be able to use hanging to the inside to straighten the lean of the bike up even more yet for exit, when combined with countersteering.

 

It gives you a lot more slide control. Even in big sweepers, you will notice, whether it be flat tracking or speedway, the fast guys usually end up hanging chest and shoulders to the inside on exit as they stand the bike up more for traction. That traction gain to be used for extra throttle.

 

One of the negatives of hanging off on the inside on a supersport road bike, is less slide control, the positives outweigh it and you aren't looking to slide big on the blacktop mid turn, at high speeds anyway.

 

In the dirt for square off turns though, mostly I used the front brake hard coming in straight, kept it on leaning a small amount on a slight or big radius curve coming in, and let it off as I entered close to the pivot area, while staying on the back brake to keep the rear sliding good before the pivot point. I'd be way up front, slide into the pivot on the rear brake, countersteer and throw (knee) it down, clutch it out on full throttle while turning into the turn real hard (which would help with standing the bike back up to catch the acceleration sliding) and exit. That was two stroke type power though and the progressive traction on dirt let you get away with it all.

 

With that skinny little knobby up front you weighted the ###### out of it to dig the knobs down in and you were either on the brake or a reasonable helping of gas for most things. If you tried coasting at all you lost the front and ate it unless you were actually going too slow (and you still might lose the front going slow). Rule was brake or gas to keep the front. An unweighted rear tire spun up easier and you could straighten the lean up more without highsiding by having it spin heavily reducing ultimatel traction for just a bit as things progressively grabbed. Also that spinning rear added some gyroscopic stability at lower speeds. You could shift body weight rear when you stood the bike up and had it moving forward on exit and things were already beginning to hook up good sideways.

 

Essentially you gave away ultimate mid corner speed to gain the advantage of better slide control and less time spent at risk at heavy lean (traction can go away fast at big lean on the dirt over rocks and bumps big enough for the back tire to lose contact with the ground). For the most part you were on a berm using it like a banked turn, or you ran a line that kept the turning part of the turn real tight and of very short duration minimizing what you gave away. The line in and out you straightened up more on larger radius to maximize traction for braking and gassing it out.

 

The little bikes had to run more sweeping lines to some degree, but they used holding it wide open and clutching the bike in a higher gear to try and minimize needing wider radius mid corner lines.

 

I've never run the new 4 stroke dirt bikes, so there will be some differences to a point. I did ride the bejeebus out of a friends old British Ariel 500 single (not a lot of power). The extra tractability of that motor let you hang the rear out speedway style in a farmers meadow like I couldn't believe, and still maintain control. I need another go round at life, sigh. The new bikes look like a blast.

 

So supermoto, some guys seem to be going for the dirt bike body position style to utilize sliding it in like on dirt, while some others are going for less lean angle and less sliding to gain more mid turn speed like in supersport.

[racer]

This is the greatest forum on the internet...

 

isn't it tho?

 

when i think about most of the other forums out there (motorcycle or otherwise)... i'm really proud of what we're doing here.

 

i give the website to every new rider i meet (about 2-3 everyday) and tell them they must buy the books and check out the really cool forum and then sign up for the school as soon as they can.