Horrible woobles after swapping rake from positive to negative

So I’ve been riding Surfrodz RKP 200mm with a baseplate angle of 50 degrees on the front and 45 degrees on the rear, positive rake rear and negative front.

As I’m begining to ride faster these on empty streets because of the pandemic, I decided to switch the the rear truck rake from positive to negative in hopes I could archieve more stability at high speeds:

This was the old setup (positive rake at the rear)

This is the new setup (negative rake at the rear)

Nevertheless, after a test ride I almost fell 3 times because horrible woobles at only 20mph, woobles happened to me before only art very high speeds with uneven pavement.

To the truck experts, am I missing something here?

@RipTideSports would you suggest a good set of bushings for my setup?, I’m 71kg (156lb)

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Try changing he front to positive to see the effect and let me know what bushings you are using front and back. Also, if you are using the surf keys, remove them

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This boggles my mind a bit why this would happen…

Looking forward to reading what you figure out Alan.

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I do know that by flipping the hanger you’re reducing the trail.
I wouldn’t suspect that to have a very large effect, but I’ve not explored trail too much.
If somehow that was enough to flip it from negative trail to positive trail then that would certainly make things wobble a lot more, but I don’t know if that’s even possible in real world setup.

What negative rake should be doing is giving you a slight raising center of gravity, so it should be more stable. However that effect is very weak at center, and with the few mm or rake typical of RKPs, the effect would be tiny to begin with. With such high angles that raising center may just be essentially a non-factor.

Here’s my list of questions.
What size wheels do you have, how much drop is in the deck, what is the wheel base axle to axle, and how much rake do these surfrodz have?

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Positive rake makes the center less twitchy and the lean more divey. So negative would make the truck more twitchy (at center) which you don’t want

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I found several issues after I posted this:

  1. The rear trucks were too lose. I tighted it in and it feels way better now, however they are tighter than before the rake switch, so it’s difficult to compare both setups

  2. The front truck was vibrating like mad, I took a close look and found a deformed Bergmeister tire, probably due some pothole hit

At high speed this tire was causing harmonic vibration thoughout the whole esk8, probably transfing it into the rear truck which yielded to uncontrollable woobles.

This could also contribute to the instability when riding forward, but I don’t understand how positive rake could yield to a more twitchy behavior on straight line riding

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Here is how I always thought of rake

After doing some reading people don’t agree. Imo it makes straight line riding more stable, maybe I’m wrong. (If you’re getting wobbles you’re trucks are turning, so twitch is a factor.) I would make both front and rear positive

Also with pneumatics it’s a must that you balance your tires. Can’t tell if you’ve done so

The chart is pretty much, well, not accurate at all.

Here’s a calculator where you can actually see the lean to steer ratio.
https://www.desmos.com/calculator/3yfrtskuh6

Rake doesn’t actually have an effect at all on turning angle.

However, if you’re merely looking at the graph as a riders interpretation of the sensation from each, that’s a bit different. Because rake does have an impact on resistance progression.

Interesting, from riding trucks with lots of rake I would have thought turning angle was affected. So it’s only resistance that changes??

So you could replace “increasing turn” with “resistance” in the chart?

That would help, but I think its more important to convey that its not a data driven graph.
Its an approximation rather than an actual representation.

The real question is how do you do that without dirtying the presentation?
The nice presentation is half the reason why that graphic gets shared.

Well I just came back from my last test ride, I kept negative rake at the rear and tighted it a bit more, then I swapped the hangers from negative to positive rake at the front and loosed them even more than before. The result was an extremely stable board at high speeds, I got even 30mph without any dust of wobble this time.

The tires are brand new on the front so vibration is 95% gone

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After a bit more testing the board is not carving as much as before, I’d say 15% less, you need lean more to turn on some roads than before. Negative rake is clearly noticeable

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back in the day we used to run Randals flipped (negative rake) rear and positive rake in the front for a stable setup. seeing negative rake front and neutral or positive rear has made me scratch my head a bit more than I usually do. sounds like you’ve got your setup mostly ironed out now :ok_hand:

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it sounds like you’ve invented the shopping cart