mx5-kiwi

righto...thank you all, will work on those issues raised.

In regards to the front camber, from talking to the alignment guy and "assisting" him do it the last few times, we are struggling to get any more camber with out blowing out the other settings...is this common or are we not on the right track?

Question about the sway bars, what is the preferred front and rear (in mm if you can...)...these are/were the only aftermarket items available locally at the time but I will try and see what I can get in the sizes suggested......freight is a killer to here, probably more so with sway bars being an odd shape.

Savington

iTrader: (31)

The ideal Miata setup, IMO:
700/400 or 800/500 springs (700/400 is more supple over rough tracks, 800/500 is ultimately faster on smooth tracks)
1.125" tubular (28 or 29mm) front sway or 1" (26mm) solid front sway (tubular peferred)
12-14mm rear sway to taste (OEM is 12mm, MSM is 14mm, nothing larger)

Street camber: 2.2F, 2.0R, 3.75 caster, 0 toe
Race camber: Start at 3.0F, 2.5R, 3.75 caster, 0 toe, tweak camber according to pyrometer data and/or tire wear needs.

In order to get 3.0 in front without offset upper bushings, you need to run the car low. 4.0-4.1" at the pinch weld. If you are only at 4.4-4.5", you'll only see ~2.5* on camber. Essentially, run the car as low as you can in the front without it constantly bottoming everywhere.

newold_m

iTrader: (2)

Is that caster recommendation due to the depowered rack or is there another reason for keeping it around 3.75 degrees?

Savington

iTrader: (31)

Depowered rack. I like a pretty light wheel, so I keep caster under 4 degrees and use a 340 or 350mm steering wheel.

robertcope

Would you say more caster is better if you can handle it? My very basic understand is that more caster will mean more dynamic camber, which 'generally' seems good?

robert

Savington

iTrader: (31)

Could be better, but unless you're winning races and looking for those last few tenths, I wouldn't bother.

emilio700

iTrader: (3)

I run max caster on all our cars. I have had team drivers complain about the steering effort so I switched from 320mm to 350mm wheels. I didn't reduce caster. I like the additional cross weight jacking effect that helps the car initiate rotation into turns.

mx5-kiwi

Emilio, this cross weight jacking is part of what i was trying to say/understand at the beginning.

Obviousley we have centred on some bigger issues for me to get sorted for now but in the mx5 / miata.. is cross weight jacking a progressive thing or does it happen/take effect at a certain point on the turn of the steering wheel...I mean in your actual practice/experience.

Becasue that is what it feels like...if my full turn in on the steering wheel was rated at 1-12 I would say it starts to have effect at around position 5 of the turn. Any corners with less turn in or more gentle turn in (1-4) it doesn't do it but from pos 5 onwards it does...

Does this make any sense?

I may have just entered the realms of La La Land... but in the interest of (hopefully) learning something new I am up to SOME ridicule...maybe not MT level burn but i'll try and tough it out....

Seefo

iTrader: (5)

^is it doing it more when turning one direction than the other?

mx5-kiwi

Dont think so, havn't noticed it as such, I can and do use it to advantage often. Just that at Taupo it is beyond the use as a tool and is more of a hinderence. At the Hampton Downs track I just went too it is actually a benefit on some of the corners (IF you are ready for it...) and doesn't come in to play on the rest as they are less hard turn ins (1-4).

Savington

iTrader: (31)

It has less to do with how much you turn the wheel and more to do with how fast the corner is. Slower corner = more wheel, faster corner = less wheel.

It's all irrelevant though, since you have too much rear sway, not enough front sway, too much rear camber, and not enough front camber. Nothing you do with the alignment is going to fix that

mx5-kiwi

Thanks Savington. Yeah I understand, have started looking for better sways and will reddress the alignment numbers. Looking forward to dropping times further when sorted.

Was just trying to understand how the caster/weight jacking works...or feels like.

Speed of turn makes sense.

My plan at this immediate stage is to set front bar to it's stiffest setting and get the camber figures closer to what has been suggested.....hopefully that will show improvement for the race meeting next week.

Then I can work on replacing the rear sway bar and finding a bigger front.

Thanks for all the insight guys, much appreciated.

emilio700

iTrader: (3)

Linear, progressive. It is not an on/off switch.

Post good in car video with the symptom. And fix what Andrew suggested you fix.

mx5-kiwi

okay, temp solution.

rear sway was on hardest setting have set it too softest setting (1/2 options)

front sway was on mid setting (2/3) will set too hardest.

Going to reduce the rear camber and try for more front camber, going to reduce the rear toe to 1mm. Will probably leave caster at 3.75 or more but try to get more even/balanced with me in the car.....

Race day on Sunday, will be interesting to feel any differences....will refit the OEM sway (12mm?) on the rear after this race during end/off season period.

thanks for all the advice in the meantime.

JasonC SBB

But why would his balance change with a wheel change? (Offset changed too?)

JasonC SBB

Doesn't more cross-jacking from caster produce a stronger wedge/dewedge in the direction of more understeer?

Do you find that adding caster requires other alignment changes to maintain balance?

emilio700

iTrader: (3)

No
No

mx5-kiwi

Okay, quick update.

After qualifying second.

Race 1. Started 2nd on grind (Standing start) raced with the two other top guys and came first of a field of 18.

Race 2 Handicap start. From Pit Lane over a lap behind 1st car. Got stuck in every one elses battles, went too slow on the first 2 laps (worried about cold tyres) and lost the draught of the guy who started 2 secs in front of me. 9th place (6th through 11th all bunched up).

Race 3. Same Handicap start. Focused on sticking with guy who started 2 seconds ahead of me and we both fought through to the front. He JUST got the last guy on line by .2 sec and i came home in third 2 secs back.

I can now turn in much later and harder than ever before. I do miss the rear swinging out on one of the sweepers (p;oitns me out better) but the trade off is worth it.

I believe this car is now the fastest track car Mx5 actively racing in New Zealand (Hampton Downs 1.15.511 and hopefully .5 - 1 sec more to come off with fine tuning).

I stand to be corrected though and I am really pleased to have a a car that is in for win contention now.

So thank you for the suggestions in this thread, as usual you guys were spot on.

Will continue working on the suspension setup and balance but it is getting there.

Now i just need to stop my turbo from falling off at every meeting, via studs/nuts coming loose (TSE kit has improved this, although 2 of the 4 WERE loose again) down pipe cracking or my new manifold cracking 200 degrees around the collector...the latest issue

But that is a whole new thread soon to be appearing..

emilio700

iTrader: (3)

In car video?

mx5-kiwi

Hopefully have the first race available in a few days...

this is the before and the reason for the original post...


The spin IS related but is also caused by cold rears and a heavy handed downchange, turn in and brake release.

If you go to high res you will see a couple of really fast corrections, usually on turn in or mid corner.