Angle on PK steering column's lever

[keuk]

Hello,

I'm about to shorten my PK XL steering column.

Could anyone give me the original angle of the lever ? (wheel in the air)

Right now the lever is too horizontal, so the wheel is about 1cm backwards.

[keuk]

I have the S&S part (-18mm) and a own plate (-18mm) so -36mm on the RS24.

Here are few tests to see what the angles would look like.

Steering column 19mm shorter:

Steering column 30mm shorter:

Steering column 35mm shorter:

Bearbeitet 16. November 2012 von keuk

[Tim Ey]

Hi Keuk!

I think, that the angle to the street is more important!

While damping, the wheel is rotating around the fork. When you are shortening the damper to much (so that the lever is parallel to the street) you will get in trouble because your getting less castor while breaking.

This will cause a very nervous braking behaviour.

In your position, i would check for the angle of the lever to the ground, not to the fork.

Tim

P.S. (measured on my shortened PK fork with shortened damper ~110°)

Bearbeitet 17. November 2012 von Tim Ey

[keuk]

Thank you for the answer Tim,

Now, with the wheel on the ground and me on the scooter, the angle is almost 90°.

Bearbeitet 17. November 2012 von keuk

[Tim Ey]

Have a seat on your handlebar

When the lever is allmost parallel to the ground - I would take 1-1.5cm out of the fork. I dont with how much g you can brake, and how the force on your frontwheel behaves, but i think it must be round about the weight you get while sitting on the handlebar.

Any other opinions?

[amazombi]

Yes. What's "castor"? Or are you talking about trail?

[Tim Ey]

Ah, ok. Wrong translation. Yes, I am talking about trail.

When you have an other point of view on this, please let us know. Whats wrong about my thoughts?

Bearbeitet 17. November 2012 von Tim Ey

[amazombi]

I think the points you made are perfectly valid, I just couldn't makes sense of "castor". Plus I think it possible to decelerate with more than one G.

Maybe it would be possible to do a dummy setup to check which starting angle would be the best for the full suspension travel to chance trail the least? I mean with the trailing link in a line with the fork leg the wheel elevation curve is likely to change trail quite a bit, whereas with the link starting around 90° or thereabout it would have comparatively little effect in that respect. I'm to thick to check that without resorting to the dummy setup solution. Does that make sense?

[skoot]

Question is how much effect you really notice in practical track use. This summer I mounted a SIP damper for PK to a std PX fork. It looks almost like your fork now. About parallel to street level when driving - trail is biggest possible, running very stable. When braking or having bumps trail gets smaller but steering is getting not nervous (at least i don't notice). I guess the shorter you make the column, less directional stability you get. I wouldn't expect too much effect on damping behaviour.

[keuk]

Well I'll try the 30mm first as a dummy. The 35mm looks a bit too much.

I have the S&S part (-18mm) and a own plate (-18mm) so -36mm on the RS24.

Here are few tests to see what the angles would look like.

Steering column 19mm shorter:

Steering column 30mm shorter:

Steering column 35mm shorter:

[keuk]

Perfect, I have just cut the column, now I need to make machine a part to put inside, what thickness are you guys usually using ? 2mm? 3mm? More ? There was a thread talking about that but I'can find it...

Bearbeitet 19. November 2012 von keuk

[amazombi]

It's only there to centre the whole thing, so 2mm is plenty, I'd say. Best chamfer the cut ends so that you end up with a V-groove which is easy to fill with weld then.

[keuk]

[gertax]

Hello,

I'm about to shorten my PK XL steering column.

Could anyone give me the original angle of the lever ? (wheel in the air)

Right now the lever is too horizontal, so the wheel is about 1cm backwards.

I think you're asking for the wrong angle in this context. The more interesting position is the angle with zero travel of the shock left. After your modification, that angle should be about the same as stock, or at least not that far from it. If you should happen to overdo things, your lever might get pulled to horizontal when braking thus pulling on the shock, and you don't want that as it diminishes braking efficiency.

[keuk]

Interesting point of view. So I should compress the shock at the maximum, and ensure that the lever is just before horizontal position (arround almost90°/column) to have a good breaking effixiency right ?

[gertax]

I think you can go a little beyond this point without running into negative effects. Unfortunately I lost my notes from when I shortened my fork and shock a couple of years ago. In most of these cases, the shock travel will be reduced a little if the shock is shortened.

I did the following:

• stock fork and shock, shock mounted in stock position, compressed to maximum, took a picture of the angle, took a test ride (brake)
  
• stock fork and shock, shock mounted in the above position, again compressed to maximum, took a picture of the angle, took a test ride (brake)
  

this setup showed to be less likely to dive when hitting the brakes hard without negative effects that I could feel. It became the setup of my race scooter (and many others are driving like that as well)

• stock fork and shortened shock, shock mounted in the above position, again compressed to maximum, took a picture of the angle, took a test ride (brake)
  

that was too much, felt like you're on a ship in stormy weather when braking. also, braking performance suffered quite a lot.

So, for my shortened fork, which was to be run with a shortened shock with shorter travel than stock, i calculated how much the fork had to be shortened to end up in the position I liked when the shortened shock was fully compressed. If you lose shock travel by shortening it, it is never the same amount that you have to shorten your fork if you want to end up in the same position.

[Tim Ey]

To compress the shock without stress and heavy tools - simply remove the spring from the shock.

Just my 5 pence.