Lean angles; Dirt vs Road

[Lowe119]

Why do dirt trackers and ice racers lean the bike down and keep the riders upright - where road racers (excluding motard) lean over to help the bike stay more upright?

Why do the ice racers and motards use riser bars? Aren't those better suited for control on jumps and bumps? Could an ice racer benefit from lower clipons?

Basically - why is there such a difference in style between an ice racer going around a corner and a road racer?

[SVbadguy]

Haven't ever you tried riding a street bike off-road and with a few jumps?    ;D

It's far easier to use my DR650 for that.

A lot of has to do with leverage.  It's also a lot easier to deal with the inevitable sliding.

This year I've done a few roadraces on my DR650.  Up to now I've have been using the OEM Bridgestone Trailwings which are fairly knobby.  I consistently went 4 seconds per lap faster when I rode it like a dirtbike.  I will be trying out some BT45s next and will re-evalute how I ride it.

[tzracer]

First, dirt bikes and motard bikes have more ground clearance than do street/roadrace bikes. By leaning the bike and the rider more upright requires more clearance. By the rider moving to the inside, the bike has to be leaned less than if the rider didn't.

The biggest differences between dirt and road is traction and the size of the bumps. Offroad it is much easier to control the bike by staying upright and leaning the bike. In higher speed offroad cornering, the rider tends to lean with the bike or actually move their upper body towards the inside of the corner (especially if there is a fairly large berm). In dirt track and ice riding (flat, slick corners), it is easier to control the sliding of the bike by sitting more vertical.

As far as the bars, in off road riding, the rider needs to be able to move forward and backward more than a roadracer. Higher bars make this far easier than would clipons.

I have seen motard riders do it like dirt trackers or roadracers (I have seen pictures of Nicky Haden dragging his knee on a motard bike). It may be more of a function of what the rider is used to, especially dirt trackers.

[CCSRacer114]

Road Race and Off Road tracks have very different properties from a physics point of view, so tire manufacturers make different tires for dirt and for road.

With Road Racing, the track is a solid, immovable object that the tires work with...

With Motocross/Supercross etc. the track is a fluid, moveable object that the tires work with...

That said, the tire manufacturers have designed tires to take advantage of the surface...

Dirt tires (mx/sx) have larger knobbies on the sides to take advantage of the more fluid/moveable track... i.e.  digging the bike in results in MORE traction as the knobbies can be larger and pull the bike more...

For Road Race tires traction is rubber vs asphalt.... and knobbies wouldn't help because they provide a smaller surface contact area (if you road raced knobbies you'd low side out sooner than DOT's... and that's why slicks have more traction than DOT's... more SURFACE contact area).... on the track traction is a funtion of chemistry rather than physical shape (rubber bonding to the track rather than a knob moving dirt).

Dirt and track are very different beasts... but riding in the dirt sure seems to help riding on the track.

The upshot is that in the dirt... digging the bike in (with knobbies) results in MORE traction... and on the road race track.... hanging off and keeping the bike more upright results in MORE traction (and less tire wear).

 8)

[Super Dave]

With Road Racing, the track is a solid, immovable object that the tires work with...

With Motocross/Supercross etc. the track is a fluid, moveable object that the tires work with...

That doesn't explain why motard racers, with a whole lot of asphalt that is solid and immovable, aren't riding like road racers.

[grasshopper]

I've been doing a little dirt track racing lately and it's alot easier to slid the back end of the bike around sitting on the opposite side of the seat than the way you are turning.

Example: Going around the dirt track (You know, go straight, turn left) turning left your butt is on the right side of the seat.

This was hard to figure out at first because I'm more used to road racing.


It's a wonderful feeling sliding the a$$ end of a motorcycle around a race track. I love it!

TT racing is fun to, you actually get to turn right!

STEVENACERACING.COM (AMA Sanctioned Events)

Brian is the Physics proffesor, so take his explanation of why you do what to make the bike do this and why why why why....

Crap I don't know, I just do this and the bike does that. That's good enough for me!

[Rhun]

Dirt track (not MX or SX I suck at those two) is different. You steer with the throttle and counter steer with the bars. Want to turn more..give it more gas. You need leverage for this, not a selling point for clip ons Also your pegs need to be low and centered again so you can adjust traction between the front and the rear wheel making clipons uncomforatable. Since most dirt trackers don't have front brakes (at one time no brakes were allowed) if you nail the rear brake you just go straight on dirt so you have to wiggle the front bars to get the back to pitch out or use body english or engine pull to get the back to go out thus being set up for the corners. This helps you deselerate into the corner and puts you in a position to accerate hard out of the corner. Folding the inside peg is very common.  

[CCSRacer114]

That doesn't explain why motard racers, with a whole lot of asphalt that is solid and immovable, aren't riding like road racers.

Original question was...

 Why do dirt trackers and ice racers lean the bike down and keep the riders upright - where road racers (excluding motard) lean over to help the bike stay more upright?

Excluding motards...

And my answer was from Gaetano Cocco.

(hey, I'm not smart, I just know who to ask).

[andy342]

That doesn't explain why motard racers, with a whole lot of asphalt that is solid and immovable, aren't riding like road racers.

My understanding is they are sliding the bike to preserve the suspension geometry.  When you lower a bike too far (like going from a 21" wheel to a 17") you lose a ton of trail.  

If the rear is sliding the front isn't compressing so much, preserving trail.

Of course, we are working on a solution for this.  

I'm learnin'  ;D

Dave, call the shop sometime.  x133

[Super Dave]

Hey, Andy...

Yeah, I've always thought of that.

Some people seem to like 19's at some local stuff...so I've heard.  But it's not common in top level motard for anyone to have 19's.  

Slowing down a bike in motard with the back hung out would allow the chassis to maintain an amount of trail that it would otherwise not have when leaned over lined up.

[andy342]

Probably so they can run motard and dirttrack with the same bike.

Although the record up Pikes Peak this year (all dirt) was set on a KTM motard with 17" rains.

[Super Dave]

Now was that a motard bike that came with 17" tires OEM?

In 1987, we raced a GSXR1100 Superbike in endurance.  We thought we'd be cool and get a 17" front PM wheel to reduce mass etc.

Really turned very, very different from a regular GSXR with 18's front and rear, obviously.  But we could get better slicks for endurance racing.