Rake and Trail is Important

Back when Honda announced the coming of the XR400, I was so excited that I told the
sales manager at House of Motorcycles (619 229-7700) to please put me at the top of
the list. Although I didn’t like the XR400’s proposed rear suspension set-up (harsh ride)
or their radial valve head, I figured I could live with them after some modifications.

Before the XR400 was released I obtained the Honda specifications sheet and
immediately canceled my order. Why you ask? Well, in the early ’90’s, quick steering
supercross/motocross geometry began to appear on dirt bikes which was a huge
mistake. The problem is that supercross tracks are designed and constructed for the
event and although dirt, provide excellent traction unlike Baja and other places where all
kinds of surfaces from rocks to deep sand are common. Believe me you haven’t ¬†lived
until you’ve ridden a quick steering heavy weight MSM like the Honda XR650L through a
long deep sand wash.

But again I digress. The XR400 Honda steering numbers were more like a road racer;
something like 27 degrees rake and about 3.7 inches of trail if my memory serves me
correctly. I remember discussing the XR off-road steering problem with one of our local
top off-road riders. “Bob” bought one, took it on a couple of Baja rides and then sold it.
When asked to describe his XR400 riding experience, “Bob” replied, “I spent a lot of time
standing on the foot pegs in the rough stuff and every sand wash was a white knuckle
experience. Even on the high speed dirt roads the thing shook its head at 60mph.”

The KLR600/650s are good examples. Even though the KLR600 was 50+ pounds lighter
than the KLR650 it had looser steering numbers; 29.5 degrees rake, 4.8 inches of trail
versus 28 degrees rake and 4.4 inches of trail. Those differences (weight and steering)
made the KLR600 a much better dirt bike than the KLR650. At the same time it steered
much too slowly on pavement. The factory probably decided, and rightly so, that few
KLR’s were leaving the pavement so let’s give them quicker street steering. By adding
another 28 (mostly front end) pounds to the KLR in 2008 and making it more susceptible
to crash damage the factory has moved the venerable old bike even further away from
“dirtability” (excuse the term).

If your KLR miles include lots of off-road riding, do yourself a favor and find a 1996 to
2007 KLR650A ( the best years are 1996 – 2000).

We here at Top Gun ride only “A” model KLR’s and set up varies according to the job at
hand (no raising links thank you).

The principal is simple. Raise the front end or lower the rear and you slow the steering
(remember, more trail, less flail).

Suspension settings including spring sag, shock length, fork location, and link
dimensions are all used to adjust rake and trail. Often overlooked by many is tire
diameter. After careful study we are convinced the standard for the KLR650 should be
almost the same as the DR650; approximately 650mm rear and 705 front. Although all
120/90 X 17’s and 90/90 X 21’s are not equal. We like those sizes for the KLR due to the
limited space in the wheel well (less than the DR650 which has a 120/90 X17). Install a
tall wide 130/90 X 17 or 510 X17 on your KLR650 and you’ll not only quicken the
steering, but also in some cases bring the spinning tire into contact with parts on the
swing arm and in the wheel well. If you have 2 inch lowering links and have not restricted
travel, things could get worse. It’s touchy, dangerous stuff so be careful. Also, remember
tire diameter affects gearing but that’s a subject for another time.

I asked Todd Vosper to take a couple of minutes during a break from building U.S. of A’s.
new F-35 fighter plane, and figure the rake and trail I’m currently running in the dirt both
solo and 2 up with Pauline. I’m using tire diameters 695mm for the Metzeler 90/90
Unicross and approximately 650mm for the 460 X 17 King Unicross copy plus factoring in
a 1.2 inch drop at the rear for lowering links. Todd came up with 29.2 degrees rake and
121mm (4.76″) trail (remember, stock is 28 and 112mm (4.41″). Those numbers are very
close to the old KLR600 of 29.5 degrees and 122mm (4.8″) but I wish they were 30.5 and
5.2″ on a heavy bike like the KLR650A. (Todd’s Note: First of all, although I’m involved in
the F-35 program, I can’t take any credit for building it; though I’m not responsible for any
cost overruns either. Second, I did not account for change in wheelbase when figuring
the new rake and trail. However, I did check my calculations assuming a reasonable
amount of change to the wheelbase and the difference was insignificant. The results also
correspond to a frequently used rule of thumb of 1 degree of rake per 1 inch change in
ride height for bikes with similar wheelbase to the KLR and DR.)

Oh well, 29.2 degrees and 4.76″ trail has served Pauline and me very well for more than
15 crash free years riding two-up in the dirt.

Since we’ve decided to stay with the 21 X 17 semi knobby combination (MT90AT’s) it will
take Pauline and me less than an hour to change back to stock length links, her Ohlin’s
9kg shock and 15/46 gearing (chain adjusters are pre-set and attached to each
sprocket/carrier).

When we use a full on street set-up, the tire combination is 19″ front and 18″ rear. Since
the front 19″ tire is smaller in diameter and thus drops the front of the motorcycle
approximately one inch, we leave the 1″ lowering links in place (bingo, stock geometry).
The only downside of this set-up is the loss of 1 inch of ground clearance. On mountain
roads with lots of slower speed sharp curves, the above 21/17 MT 90AT combination
works great.

Remember, a well set-up bike is a safer bike. How’s that for some good advice?