Comments on: how does changing the trail on a 2004 sporster custom affect the handling?

By: Live to Ski

Live to Ski — Sat, 17 Oct 2009 04:52:00 +0000

As others mentioned…18 degrees rake, the fork would appear to be almost vertical. Not a good set-up. No stability at speed.

Adding 18 degrees to make it 46 - 48 degrees rake, not very practical. So unless you’re building a show bike, not recommended either. Nearly impossible to make a turn and stay on the pavement and you’d need the area of a Walmart parking lot to make a U-turn.

Of course if you plan on riding only in a straight line, go for it.

By: Larry G

Larry G — Tue, 13 Oct 2009 22:28:38 +0000

since a sporty is modeled after a flat track bike to start out with and has about 28 degree of rake and if you add 18 to it that would be 46 degree rake ..i figure anything over 40 degrees seems to be real sorry in a parking lot or close quarters at low speed.. Look at a top fuel harley dragster and that rake is for going straight and at 200mph without going into a tank slapper … personally i don’t like raked trees they mess up a lot of things …If you do this mod the bike will be hard to handle in a parking lot but on the freeway a dream to ride .. Nothing is free ..if you get more of one thing then you loose someplace else

By: no_bloody_ids_available

no_bloody_ids_available — Sat, 10 Oct 2009 23:05:46 +0000

take a poor handler and make it worse? - why not!

while you’re at it you could weld up the rear suspension & buckle a wheel rim or two - it’d be a complete pig then.

By: vtwin_doc

vtwin_doc — Wed, 07 Oct 2009 16:10:36 +0000

I DO NOT RECOMMEND IT!!!!
You said the kit changes the rake to 18, I looked at the kit, it actually increases the stock rake of 30 by 18 making it a total of 48.
The bike will NOT handle well at all at low speed, turning, cornering, etc will be DRAMATICALLY harder. Moving the bike around by hand, as in moving around the garge, will be hard, as you turn the bars, the front wheel will not TURN, it will FLOP AND LEAN. Not to mention the added length of the forks will cause constant flexing and bounce…. and twisting under braking.
I have alot of experience with “choppers”, the only way I would recommend that kind of rake, is to buy a new frame, one ENGINEERED specifically for this type of front end, even then, some of the handling characteristics I mentioned come into play, but not quite as severe. When frame designers do this…they incorporate the main rake into the frame neck and use raked triple trees to correct the trail, along with the proper amount of stretch in the frame downtubes and backbone for optimum handling…….this kit you are looking at uses the triple tree to do nothing except severly rake the forks for a stretched front end. (example…your frame is 30 with 0 in the trees, GREAT handling - - add the kit, 18 trees to a 30 frame, an overall total of 48, POOR handling …….a Big Dog K-9 has a 38 frame with 4 in the trees to correct the trail for an overall total of 42, GOOD handling…..for a 9ft long bike)

By: MotoMan

MotoMan — Tue, 06 Oct 2009 06:27:55 +0000

I’ve done some front end mods and they can significantly change the handling of a bike. If you increase the rake you will also increase the trail (see previous answer), if you you increase the trail the bike will want to to go straight more easily but will not turn as easily. One of the common myths are that stretched front ends handle better, yes if want to go in a straight line.

So if you make this mod you will loose low speed stability and the ability to easily turn and make the bike go where you want to go (turning off the street into a parking lot is an example).

Personally I would not change any bike to make it look better if it did not work better. I’ve always admired what Peter Fonda said about his Captain America bike from the movie Easy Rider, “that bike was hard to ride.” He was telling the truth. Where as if you listen to the Teutuls “this bike handles sweeeeet.” LOL

By: Firestormer

Firestormer — Sun, 04 Oct 2009 02:10:17 +0000

Are you sure its 18 degrees? Thats incredibly steep to the point where the bike would nearly be unridable. There would be no high speed stability at all. Most sports bikes are in the region of 22-23 degrees.

By: easygoing157

easygoing157 — Sat, 03 Oct 2009 08:08:37 +0000

Rake and Trail:

We know you were day dreaming about *** when the triangles were floating about the blackboard, or for those of you who were already warped, you were doodling motorcycles while the teacher droned on about sines, cosines, tangents. Now all these years later when you finally got the money to build your dream bike, all you can do is thumb through pictures of other people’s projects, searching for that “look” blissfully unaware of what all that trigonometry was for. We’re going to show you how to do the calculations. We’re going to present some data for you to study, and leave the decisions up to you. It might explain why shopping carts weren’t meant to go 200 mph.

Your front suspension geometry is defined by the following six variables which are defined as:

OFFSET: Centerline of the top steering neck to the centerline of the top of the fork tubes.

RAKE: The angle in degrees of the steering neck from the vertical cord.

FORK LENGTH: The distance between the top of the fork tubes to the centerline of the axle.

DIAMETER: The diameter of the front tire.

TRAIL: The distance defined by the vertical line from axle to ground and the intersection of centerline of the steering neck and ground.

RAKED TRIPLE TREES: In order to bring trail figures back into line, triple trees with raked steering stems can be used. Usually adjustable in 3, 5, 7 degrees of rake.

HOW TO MEASURE CORRECT TRAIL

Raise the bike to an upright position, using a tape measure, hold the tape straight down from the front axle to the floor. Put a mark on the floor at that point. Then place the tape parallel to the steering neck, following the angle of the steering neck all the way up to the floor. Put a mark here also. Now measure the distance between the two marks and you have your trail measurement. It should read between 2 and 4 inches. Note: If your bike is equipped with a rear suspension, have someone sit on the seat when you make the measurements to simulate your actual riding condition.

TOO LITTLE OR NEGATIVE TRAIL

With too little or negative trail (steering axle mark behind the front axle mark), the bike will handle with unbelievable ease at low speeds, but will be completely out of balance at high speed. It will easily develop a fatal high-speed wobble. EXTREMELY DANGEROUS!

NORMAL TRAIL

Normal trail is somewhere between 2 and 4 inches. The bike will handle easily at both high and low speeds. Flowing smoothly through curves without swaying or wobbling. If you use a very fat rear tire, you should keep the trail as close to 4 inches as possible.

TOO MUCH TRAIL

If the trail is more than 4 inches the bike will handle sluggishly at high speeds. It will seem almost too steady. You will have trouble balancing the bike at lower speeds or on winding roads. It will feel generally sluggish and clumsy.