Motorkhana Set up

[Callumgw]

Hi guys,
We have a 1990 Na that the kids are using for moyoekhana and khanacross. The car is lowered (green japanese coils) and has KYB dial adjustable dampers. Its running on 15 inch rims (but i also have a set of daisys). It had a bent kframe and passengers side lower a-arm bolt which I fixed before it was aligned.

So the question is, is it normal for the wheels feel like the go "overcentre" when approaching full lock?

Is understeer at high steering angles normal?

Is push understeer common?

We're having a bit of trouble getting consistent behaviour, and provoking oversteer seems hit and miss. The handbrake isnt strong enough to get consistent locks on tarmac. Next time i'll probably use daisys with hard old rubber on the rear to help. But was hoping to get a better setup to help understeer.

[I'll look up the alignment settings for later discussions]

Thx
C

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[NitroDann]

So the question is, is it normal for the wheels feel like the go "overcentre" when approaching full lock?

Yes, due to castor.

Is understeer at high steering angles normal?

The castor leans the tyre over, you're on ly the edge unless you set the car up with a little body roll entering the turn.

Is push understeer common?

I'd say it's the driving style.

We're having a bit of trouble getting consistent behaviour, and provoking oversteer seems hit and miss. The handbrake isnt strong enough to get consistent locks on tarmac. Next time i'll probably use daisys with hard old rubber on the rear to help. But was hoping to get a better setup to help understeer.

[I'll look up the alignment settings for later discussions]

Thx
C

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[Callumgw]

Thx Dann,
So that over-centred feeling is normal for an NA and not due to a bad set up (alignment)?

Just hunting alignment data now...

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[Callumgw]

Front
Total toe: 0.8mm (0.5L, 0.3R)
Camber: -0.95deg L, -0.85deg R
Castor: 4.85deg L, 4.45deg R
King Pin 12.9 L, 12.45 R
Incl Ang: 11.95 L, 11.6 R

Rear
Total Toe: 0.7mm (0.3L, 0.4 R)
Camber: -1.15 deg L, -0.95deg R


So my thoughts are more front camber (not sure if theres adjustment left) and maybe liven the back with a toe adjustment... ?

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[NitroDann]

It's just castor, your family wagon feels the same way when it's sliding.

Dann

[Callumgw]

It's just castor, your family wagon feels the same way when it's sliding.

Dann

The overcentre feeling happens even when not sliding or going hard. Its much more pronounced than in any of my other vehicles, which is why I asked about it in the Mx5. I was thinking that maybe the steering end stops might be missing or the 'stance' set up the previous owner had may be playing a part.

Thx
C



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[NitroDann]

It's just because you can feel it in an MX5 but not a commodore. It's a driver-connected-with-car thing.

Dann

[Locutus]

Everything you've described is normal. Adjust your rear calipers to improve your handbrake.

[project.r.racing]

put a bigger rear sway bar on it. then try again.

[Callumgw]

Thanks all,
Rear sway bar with adjustable links sounds like a good option. Current rear bar is stock, any recommendations?

Handbrake adjustment might be worth considering, but it is stock calipers with QFM pads (HP-X). They might be getting hot enought to really work well.

C

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[The American]

For motorkhana, you want rear to be somewhat stiff, and an LSD really helps to get it to rotate. The timing of the handbrake application when throwing it into a turn makes a big difference - and takes practice.

Understeer in such tight corners is to be expected if you don’t get the rear loose when beginning a turn.

[Callumgw]

Yep thx. It has a viscous lsd, so better than open diff

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[hks_kansei]

When I did the Vic Motorkhana series I found the biggest help for me was:

decent handbrake.
#1 thing you need, ideally you should be able to lock the wheels in an instant.

Most of it is down to practice, and in a RWD you need some decent coordination for handbrake turns etc.
Understeer is usually a result of coming into a turn too fast, or with a bit too much lock, ideally you'll have the back starting to slide before the cone, meaning less steering lock is needed.

power steering is a MASSIVE help, as it leaves a hand free to pull the handbrake without breaking a wrist (word of warning, esp for the kids. a non Power steer MX5 will have HUGE steering kickback on reverse throws etc, if you're not expecting it and have a finger in a spoke it'll likely break it)


Anyway, the setup I found worked best for me on a bitumen course was the day I tried a staggered wheel/tyre setup.
I had 15x8+25 wheels on the front, with 205 tyres (so a wide track, wider tyres too)
and had the rears fitted with a pair of daisys (so 14x5.5 with 185 tyres)
Also up the pressure in the rear tyres, compared to the fronts.

I found that this really helped with getting the bum around cones easily.




If you want more/better tips though, have a chat with DeBounce on the forum.
Nice guy, and he's been doing motorkhana for years in his NB (and now his NC i believe)

His skills at this sh*t all over mine.

[Callumgw]

Thanks!
Kids are just starting out, so havent got into reverse flicks yet, but will watch for that (no power steering). My motorkhana experience has previously been with fwd, so more forgiving on handbrake use, and kids arent using it yet. But I'll give it a service to try and get more consistent results.
I nearly took a staggered set up, but the kids flat spotted a tyre at Riccardos Racer, so had them on the back to make them round again!

C

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[Callumgw]

Guys, thanks for feedback.
Thought I'd give you a summary of the plan, I'll redo alignment to DeBounces settings, upgrade tyres to cheap semi-slicks for tarmac events (possibly Federal 595), run staggered wheels (Daisys on rear), service handbrake.
I'll hold off on swaybars (but if someone has a complete adjustable set cheap in Melbourne I may be interested for later)
Also interested in a cheap set of 15x6 upto 15x7 for an extra set of tyres for dirt.

C