Understeer issues

[Boags]

Ok guys,

My 90 MX5 has kings on the back, something stupidly low (black, not sure of brand, but i scrape on everything, even on lumps in the road, and when i put on stock NB8B wheels they scrub at 3/4 lock through corners) at the front with what i think are stock shockies(most likely done the 200K the car has done. I run 36 PSI cold in Yoko A539s.

I'm getting a bit of understeer when coming out of tight corners, tracks are usually fine, but roundabouts and u-turns, if i give it any power (not spinning the rear of course) i'm understeering. Should I:

A: Get KYB AGX adjustables to firm the ride...
or
B: Get 2 Kings and throw them in the front
or
C: Sway bar, engine bay strut support(not sure of actual name) anything else to work on stiffness.

I find handling on the track is quite good, i have very respectable times for an NA6, so i'm not sure $500 for KYBs from the US is needed...

Really, i have no idea though... That is where you lot come in

Thanks in advance,

Boags

[PT]

I'd take a closer look at your shocks, are they standard, or aftermarket and how old are they? I know that it is how you bought the car but a closer inspection might reveal some things.

Have you recently had a wheel allignment done by someone who really knows there stuff (ie, not a bob jane).

Hows the bushes looking?

Two new springs in the front certainly wouldn't hurt.

I think it needs an italian tune in any case and you should let me thrash it though the twisties this weekend.

[Matty]

springs known to be matched would most certainly help. handling should be neutral even with knackered shocks.

I'd drop your tyre pressures to ~30-32 psi.

[Boags]

I'd take a closer look at your shocks, are they standard, or aftermarket and how old are they? I know that it is how you bought the car but a closer inspection might reveal some things.

Have you recently had a wheel allignment done by someone who really knows there stuff (ie, not a bob jane).

Hows the bushes looking?

Two new springs in the front certainly wouldn't hurt.

I think it needs an italian tune in any case and you should let me thrash it though the twisties this weekend.

Such a good friend you are, offering to help like that, and i suppose you ask for nothing in return...

Hmmm, i have the settings for the alignment around somewhere... i'll post them. No idea how to look at the condition of them, but last service i asked how the shocks were and "couldn't see much cause it's so low, but they seemed ok" was the response....

Eventually kings and KYBs are going to happen, but $1000 of damage cause of some a$$hole in a drift car means that is't for a while. I'll get the most pressing done first.

Fancy a dawn patrol this week?

Cheers PT

Boags

[Babalouie]

Could be that the fronts are bottoming out if it's as low as it sounds....in other words, running out of travel and when that happens the spring rate goes from whatever-it-is to infinity and you get understeer. If your shocks are knackered then it wouldn't help things either as the shocks would allow the springs to bottom out more often...

What ride height you got at the front? (centre of wheel to wheelarch?)

[Boags]

Hmmm, Thanks Matty. Will try lower PSI, and start fishing for some kings.



Here is my allignment settings, organised by the panel shop after the you know what at QR... No, not Bob Jane, Bridgestone tyre centre... Perhaps time for a visit to Fulcrum... Anyone one know of someone good for allignments on the northside?

Thanks for the help guys.

Boags

PS. Babalouie, that is possible, but i can't measure at the moment, the car is at my uncle's house while i sell a Mazda Premacy. Anyone looking for a Premacy, i'm selling one CHEAP!

[JBT]

IMHO Boags, the front suspension is in need of rejuvenation but it will need to be done so that it all stays \"in phase\" with the rear suspension.

Try and get the car to Fulcrum Moorooka some time if you can and get them to give it a good check-over. They'll tell you the what, why, where and how much of it all.

[Fra66L]

You could also try Fulcrum at Stafford...

Cheers,
T

[Ted]

Boags - You are running a fair bit of toe in at the front. If you are finding it OK at the track, then realistically its not all that bad. I think the biggest technical problem is that the front is too low, and as Babs said you just aren't getting the travel you need making the front hop around a bit on the road. On the track, it shows up less due to smaller steering angles and higher grip surfaces with fewer bumps/camber.

If you want to fix it for cheap, then I would try what Matty suggested with tyre pressure for a start, and try both ends. Then I would change your driving style a bit. Any car will understeer if you make it change direction too quickly. You either overcome that with grunt (unlikely to happen) or weight transfer (lots of ways to do this). Being a front engine car, you already have some weight on the nose, if you allow it to use it. So just wait a fraction of a second more before opening that throttle, or use a touch less throttle or less steering angle, or simply turn the wheel a bit slower so that you don't overcome the grip you have at the front.

[Boags]

Then I would change your driving style a bit.

Sounds like i need to go on a skid pan day with instructors...

Know anyone who could organise that Ted?

Thanks for the tips guys, i'll start with tyre pressure, and reduce right foot pressure while looking for some kings.

Boags

[OMY005]

Sounds like i need to go on a skid pan day with instructors

I learnt heaps about my car and driving style at the last day I went to. Its all to do with weight transfer. Well worth it.

Andrew.

[phatMX]

hey Boags, how is your car coming along from that incident?
I have the same problem on the road but track seems to be good. I've found that when i understeer on a round about its because i'm going too fast/turning the steering too fast. I wouldnt have a clue what my alignment settings are (for comparison) but i know it pulls to the left, i've meant to get that fix the last two track days.. maybe it'll happen next time.

[Boags]

The car is going well, i realised though that i haven't been on the track with my current settings, they were only done after the prang, so i'm not sure how it would handle on track.

The only thing i was really annoyed about from the panel beater is now my central locking doesn't work It is a total pain in the arse. Alarm still works off the remote, but no locks.

Boags

[Charlie Brown]

Wow Boags, I'm with Ted on this one.
That's a lot of toe in on both the front and rear setting.
The rear would stick like s**t to a blanket and the front would tend to plough away.

Drop the front to about 1mm TOTAL toe in and the rear to about 1.5mm TOTAL toe in. For camber run about 1 degree negative on the front and 1.5 negative on the rear. You can go wrong with these setting for the road.

The other comments from Matty, Ted and phatMX are applicable too.

[trader]

Hi Guys

I recently had my alignment done and asked for a bit more camber. I ended up with -1.0 all round which I'm happy with for street use but toe ended up 0.00 mm front and rear. This is making the car a bit twichy and also tramline.

My question is can I just give it a bit of toe in by adjusting the tie rods to my liking and if so by how much would I have to rotate the tie rods to bring it in say .5 mm each side?

Seems like an easy fixit than back to the shop.