Rake confusion

[OldNick]

Here is what I do know. I have Roadsmith 6 deg raked forks on my Valk trike.I have no comparison, but the Valk takes moderately strong force to take round a turn if I push it.

OK. SO here is what I think I know.

Trikes need to be steered, not leaned, so there is effort to push the bars that is not there on a bike.
A rake kit lays the forks down flatter by 4-6 deg.

Now, according to me this should increase the trail/caster. This makes the trike steadier on the highway, but harder to turn on corners..... TANSTAAFL.

AFAIK there is one exception to this and that is the TBR kits that moved the fork legs forward of the steering head shaft and _decreased_ the trail. This makes turning easier...but I would assume straight riding less steady. I gather that _rake_ is actuall unchanged.

Here is where I am confused. People get rake kits and say that turning is easier, less force from the bars. Not much mention of steadiness, but certainly no complaints. People talk of being like power steering. As far as I can see, you get one or the other and an oincreased fork rake should not make steering easier.


What happens on a real chopper where the forks are out the front by what must be 20 deg over normal?

I checked Bazooka's rake kit discussion, but there was a lot of comments but no summary of why.

Can somebody point me here, either by description or to a site that lays this out?

 

[Gold Rush]

Nick I'm not where I can give you exact web addresses but I can tell you that when I was researching rake kits I discovered the kits in fact reduce trail not increase it. Depending on original geometry, different forks will accept different maximum rake kits before correcting that trail figure too far.

I can't explain why your six degree kit is not giving you the easy steering most of us have but I'm sure there is a logical answer.

 

[CrystalPistol]

Nick, are you sure your Valk has a "6 degree rake kit"? Hard to believe it's got 6 degrees on the tubes and is still hard to steer?

When building "choppers" they stretch forks and change steering stem angles and the guys who know their art will engineer sufficient trail to make the chopper stable as a motorcycle at speed.

A rake increase in the pure sense typically would increase trail and increase effort to steer a trike all else being the same but the term "rake increase" includes steering stem modifications. A little extra trail only slows the steering response of a bike, and choppers are not great road racers.

Those are "oranges" .... the subject at hand is "apples".

These rake kits we are talking about are not "true" rake kits. There is no change in steering stem axis, that imaginary line drawn down through the stem still hits the road in the same spot.

On a stock front end, this is about 4-1/2" in front of or ahead of the tire contact point directly under the center of front axle.

What these trike intended "rake kits" do is change the angle of the fork tubes only by laying them down 4.5 or 6 degrees.

The effect this has is pushing that front tire out forwards a couple, maybe 2-1/2 inches closer to where that imaginary line through the steering stem hits the road, hence .... reducing trail.

Below is a crude drawing .... stock motorcycle is solid lines, broken lines show what a "rake kit" like for trikes does. Whatever effort is required to steer your Valk with a 6 degree kit .... it would be higher with a stock front end.
Likewise .... when you are on uneven ground that rocks from side to side you feel that in the steering of a Trike as the front is still a "caster" and is being pulled to either side at low speeds .... this too is felt even more so with a stock front end.

 

[OldNick]

Thanks for the reply, but I am still confused.

If you increase rake (flatten the forks out toward the horizontal) you increase trail.The only way to stop this is to increase the distance between the axis of the fork legs and the axis of the steering stem (offset). But if rake makes steering harder, but straight line more stable and you then use offset to overcome that, what is the gain of increasing the rake in the first place? Or, why use offset to overcome the straight line gain of rake?

Also, it feels to me that increasing offset would actually make steering harder, as you effectively increase the radius of the fork's distance from the centre of pivot...the stem. Ther further you go, the less lever advantage you have to any length of handlebar.

I do not know if my trike is hard to steer compared to others. I don't have access to the standard triples to try changing it and see what happens (well for many hundreds of $$ I could, I guess)

 

[OldNick]

Sorry.I cross-posted with CrystalPistol and that explanation does make sense. I found out that increasing the offset on the lower tree only _does_ decrease rake, while effectively increasing fork rake angle! It sounds crazy, but a diagram does sort it out.

Thanks for the help and trouble of posting the drawing! That clears it up for me. The light had started to dawn for me, but that confirms it.

I just looked at my Valk and yeah the rake kit has pushed the lower clamp out from the stem. I, like many others gnawing at this, just assumed it was like raking the stem itself, which as you say is how choppers work and makes very stiff steering

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BTW, now I think I get why leading link suspension can be so good. Because there is no fork angle change due to dive under heavy braking or over big bumps, they can get trail down to tiny distances, without the danger of the cycle becoming completely unstable.

I think it all starts to fall into line.

 

[CrystalPistol]

Well, "Bikes" work good with 4-5" trail and 27-30 degree steering stem axis angles. Trail is always a measurement of how far behind that imaginary line drawn through a steering stem axis intersection with ground .... the tire's contact patch is.

Here's something I wrote years ago ... shortened some ..... maybe it helps?

Stock, our Gold Wings have near 4.5 to 5 inches trail, the wheel touches the road that far behind where a line drawn through the steering stem axis strikes the road. The front fork tubes and steering stem are right about 30 degrees from verticle.

A rake kit adds 4.5 or 6 degrees to that through offset machining of the triple trees, so that instead of the steering stem and tubes being parallel, the tubes are 4.5 or 6 degrees skewed forwards. This additional rake of just the tubes swings the tube lower ends and front axle forwards toward the front, towards the steering stem axis where it intersects the ground, and it reduces trail to nearer 2 - 2.5 inches, still leaving some trail.

This swinging of the tubes in an arc also will lower the front of the trike as they are swinging through an arc from 30 degrees to more like 34.5 or 36 degrees from verticle. This is why Champion includes fork extensions (they did with my 6 degree kit in 2004), why CSC includes longer tubes, and why Bud Redmon had custom extensions machined for his 1200 trike.

You do not want "0" trail, you want the front to want to straighten up somewhat, you just want to lessen effort required to point it the way you want it to go. Grandpa's old Model MT John Deere had "0" trail, it would stay in circles across corn rows if left alone. That's OK on a slow farm tractor but it sucks on a high speed road vehicle.

You do not want it to go past "0" trail and into a lead condition, as then the front wheel will want to either fall off to left or right side full lock .... just like your trike does now if you let it roll backwards with any speed. Very dangerous at 10+ mph.

All trike kits for the Gold Wing will derive the same benefit from a "rake kit", a much lighter steering effort and greater control of where the trike goes under road conditions, acceleration and cornering.

 

[Lee H. Mann]

Another Rake Article

This is another version of what CristolPistol is explaining. Below is a picture of how it relates to a TRIKE with EXTENDED FORKS or FORK SPACERS.


http://www.chopperhandbook.com/rake.htm

 

[Dude]

This has been very good info. Thanks for asking the question and the great replies

 

[larryh0841]

Rake kits for Valkyrie/Roadsmith trikes

Here is what I do know. I have Roadsmith 6 deg raked forks on my Valk trike.I have no comparison, but the Valk takes moderately strong force to take round a turn if I push it.

OK. SO here is what I think I know.

Trikes need to be steered, not leaned, so there is effort to push the bars that is not there on a bike.
A rake kit lays the forks down flatter by 4-6 deg.

Now, according to me this should increase the trail/caster. This makes the trike steadier on the highway, but harder to turn on corners..... TANSTAAFL.

AFAIK there is one exception to this and that is the TBR kits that moved the fork legs forward of the steering head shaft and decreased the trail. This makes turning easier...but I would assume straight riding less steady. I gather that rake is actuall unchanged.

Here is where I am confused. People get rake kits and say that turning is easier, less force from the bars. Not much mention of steadiness, but certainly no complaints. People talk of being like power steering. As far as I can see, you get one or the other and an oincreased fork rake should not make steering easier.


What happens on a real chopper where the forks are out the front by what must be 20 deg over normal?

I checked Bazooka's rake kit discussion, but there was a lot of comments but no summary of why.

Can somebody point me here, either by description or to a site that lays this out?

I can not explain how all or why all of this works, but I have two Valkyrie Interstate/Roadsmith trikes and I can tell you what works. The first one I built using Roadsmith's 6 degree rake kit. I rode it for a few years and decided to convert my other Valkyrie to a trike. This is also using a Roadsmith kit, but after talking to Daryl at VTXtreme I used his 8 degree kit on the second one. The difference was amazing.

I subsequently replaced the Roadsmith triple clamps on the first one with Daryl's 8 degree triple clamps. There is no effort required to corner these trikes with the 8 degree triple clamps. I can easily do figure eights in the driveway. There is no low speed wobble and bump/torque steer is reduced. I have not ridden a trike conversion with stock triple clamps so I don't know how hard they are to steer. I only know what works on my Valkyries.
If you want more information on how the triple clamps work, and why, I suggest that you give Daryl a call at VTXtreme. You can find him on the internet. I have no affiliation with him other than being an extremely satisfied customer.
Larry

 

[Hocky]

Rake Kit

Not the engineering type like some of your replies suggest but all I know that my 2003GW/2004Roadsmith kit "steers" much easier since I added a 6 degree rake kit on it. I had a 1500GW/Hannigan with a 4 1/2 degree kit and it was more stable at speed. But comparing a 1500 to an 1800 probably causes a difference also.
Good luck, let us know your results.........

 

[JohnCockburn]

More confusion regarding rake

I have learned a lot about rake......"the hard way". I bought a "6 degree rake kit" for my converted 2000 Harley Ultra from American Classic Motors. I was going to install it myself. But while talking to my Harley dealer, he asked me how long I expected to work on it. I told him I'd probably kill a full weekend since I'd have the "learning curve" to deal with. He said, "You're right. I bill that job out at a flat three hours. You just bought the bike here. So you get a discount on my labor rate. Three hours @$65 is less than $200."

So I gave him the job. A few days later, he called and said he thought I had the wrong rake kit. I called American Classic Motors and was told that the kit they sold me was correct. They lied because they didn't want to be bothered with a return.

Here is the catch: The Harley stock triple tree has 4.5 degrees of rake built into it. A "six degree rake kit" only adds 1 1/2 degrees of rake (which does almost nothing for handling). What you need is a "+ 6 degree rake kit" which adds an ADDITIONAL six degrees, not only 1 1/2 deg.

The moral of the story is twofold:
1) Make sure you are buying the right stuff before you do the work.
2) Steer clear of American Classic Motors. They are lying scammers that don't give a damn about how much of the customers' money is wasted because of their lies.

I am out the cost of the wrong rake kit AND the labor to install it.....about $500. Of course, after following their advice and installing their junk, they wouldn't take it back.

So if you THINK you bought the wrong stuff, IMMEDIATELY return it regardless of what the supplier says. Because once you install it...YOU BOUGHT IT.

Better yet, just don't deal with the likes of American Classic Motors. BUYER BEWARE !!!

 

[Gorilla]

John why was the rake kit wrong? If it fit your Harley and it was 6 degrees it is what you ordered per your posting. No one lists their Triple trees by what it would add to what you have, they list it by what the rake will be with their trees installed. Your 2000 Ultra conversion did not have 4.5 degree trees on it unless you purchased TRI Glide trees separate.

Only Tri-Glides starting in 2009 and later had those trees from the factory and no conversion kit that I am aware of puts the TRI trees on with their conversion. They either don't change the trees or they sell a Triple Tree themselves. So the first question is what tress did you have on your trike after the conversion? Also most of the experts do not recommend more than 6 degrees total for the HD conversion or TRI if someone was changing their 4.5 trees. It sounds like to me you got what you ask for unless I am reading something wrong. I do not know of anyone who runs 10.5 degrees of rake on their HD. Did I miss something as to why what you purchased was wrong?

 

[CrystalPistol]

Well .... get up in morning and post as drink first cup ..... then see you've already posted ...... my bad!

Below is a drawing I added some color changes to in an attempt to show it better .... using Paint. I'll just leave it since it's "here now".

 

[OldNick]

I can not explain how all or why all of this works, but I have two Valkyrie Interstate/Roadsmith trikes and I can tell you what works. The first one I built using Roadsmith's 6 degree rake kit. I rode it for a few years and decided to convert my other Valkyrie to a trike. This is also using a Roadsmith kit, but after talking to Daryl at VTXtreme I used his 8 degree kit on the second one. The difference was amazing. I subsequently replaced the Roadsmith triple clamps on the first one with Daryl's 8 degree triple clamps. There is no effort required to corner these trikes with the 8 degree triple clamps. I can easily do figure eights in the driveway. There is no low speed wobble and bump/torque steer is reduced. I have not ridden a trike conversion with stock triple clamps so I don't know how hard they are to steer. I only know what works on my Valkyries.
If you want more information on how the triple clamps work, and why, I suggest that you give Daryl a call at VTXtreme. You can find him on the internet. I have no affiliation with him other than being an extremely satisfied customer.
Larry

Sorry. Been ouit of the loop for a while. Interesting that that extra 2 deg made so much difference. Useful info. Now all I have to do is find the maybe $1000 AuD to get one to Oz .

Nick

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I can't thank you guys enough for all the really useful input here. I learned a lot and have some food for thought.

Nick