Rake and trail

Could someone explain these terms to me? I think I understand "rake", but I'd like some clarification on "trail" and how those figure together. I did a search, but what I found had to do with trail riding and trail-er/ing.:laugh:
Thanks.

"Rake" is the angle the steering head is tipped from vertical.
"Trail" is the distance the axle is behind the intersection of the steering head centerline and the ground.
See This

Can anyone explain what effect changes to rake & trail have on handling?

Thanks, Bruce. That will help me understand it better. It doesn't mean I'll need to use it, but, at least I'll know what they're talking about.

Hi Steve,

I think Bruce's link pretty much covered the handling aspects of rake and trail, but I thought I might tell you about my experience with adding an aftermarket triple clamp to my Valkyrie and how it affected the bike's handling. I know it's not a KZ but then KZ's have very neutral steering and don't need the help my Valk did.

Valkyries come with 32 degrees of rake (Caster angle) and 6 inches of trail. This setup handles fine at any speed above 10 MPH but at parking lot speeds steering a Valk is a bit like coaxing an 800 lb. pig into a parking stall with your knees.

Pretty soon after buying my Valk my wife and I were invited to dinner at a friend's house. He has a mile long dirt rut driveway. By the time I wrestled the bike to his home I had wrenched my back and was really wondering if the Valk was right for me.

Oh Well my back healed and I soon learned that Two Brother's Racing makes an aftermarket triple clamp for the Valk that reduces the trail from 6 inches to 4.5 inches. It does this by increasing the offset by about an inch. The change was dramatic, I often let other Valk owners try out mine just to see their expressions when they realize how much less steering effort is required.

One way to appreciate the geometric effects of trail is to sit on a bike and turn the bars from lock to lock. While you're turning the bars you will notice that the steering head moves left and right. I call this movement the "tiller effect". More trail will give more tiller. Every bit of additional tiller will require more effort to move the mass of the bike side to side as you ride the bike while changing directions.

Bikes with a lot of rake and trail also suffer from a tendency for their front ends to dump into low speed turns. If you've ever ridden a Honda Shadow you'll know what I mean.

Oh Well I apologize for dipping into Hondas for my examples but then KZ's have such superior geometry I couldn't have made my point with a Kaw.

KZCSI

Thanks, Bill. Very good description--especially the "tiller" analogy. Makes sense.

Fascinating stuff, thankyou all Gentlemen.
Does this mean that this will handle like a drunken pig?:woohoo:

Actually, rake is almost completely meaningless to how a bike handles at any speed over walking pace. At really slow speeds, when the front wheel is not spinning fast enough to provide gyroscopic stability, the weight of the bike makes the wheel want to flop from one side to another, but at normal operating speed, rake makes no difference to handling. Really. Trail is the only thing that makes a difference.
The contact patch of the tire behind the pivot point of the tire gives the front suspension a tendency to stay centered. To test this, go grab your kid's bike. Ride it with the front wheel and handlebars oriented normally, and do it no hands. OK, don't, but you know you could. Then turn the handlebars 180 degrees. All of a sudden the bike won't go straight unless you specifically hold the bars straight. The rake is the same, but you changes the trail. So it's the trail.
So why rake? Because of the telescoping fork suspension. When you sit on a bike at rest, the force on the axle is straight up. This means that there's a slight torque moment at the steering head bearings. But when the bike is moving, the force isn't straight up, but up and to the rear. So when you're in motion the force of bumps or braking (which is when you hope the suspension moves!) should be more closely aligned in a direction parallel to the fork tubes, therefore not trying to bend them. Rule of thumb is that somewhere between 25 and 30 degrees is a good compromise.
The new trend in cruisers to go to a greater rake is strictly aesthetic - to give it a more "chopper" look. They can do this because of improvements in the strength of suspension components, which can now take the torque forces without bending. But the engineers are only giving in to the stylists.
The only front suspension dimension that when changed effects the stability vs. turnability of a bike is trail. Everything else is just cosmetics.

Incidentally, here is the Tony Foale article that explains how I know what I know.
www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

This also explains why I ended up in my friends lawn when I tried to ride his Heritage Softail on his widing drive while going at a "walking" pace.:laugh: :laugh: :laugh:
I still can't see myself riding a cruiser. Peg-under, standard setup feels more comfortable to me. I guess it's got a lot to do with what you're used to.
I really appreciate the info.