mx5-kiwi

Had a race meeting in the wet on Saturday. Had just done a 949 style alignment of

Front
-3.5 Deg Camber
4 deg Caster
0 toe

Rear
-2 deg
1/8" total toe

Track was "quite" wet, some shallow puddles. Problem was turning the steerign wheel more than 1/4 turn the car would dive in to the turn, making for a very hard to drive and somewhat scary day.

I may be completely wrong but have a feeling it was the caster that was the biggest issue.

Probably not so relevant for you californi ites but i have a few questions if anyone has any experience or best guesses....

what do people run in the wet?

Is there a logical/easy way to farmyard mechanic, reduce camber / caster without special tools if it does change to wet?

Leafy

iTrader: (1)

Caster is fine, you probably want more than 4 in anycase. You'd basically just want to take out camber in the rain because the car wont be transferring as much weight and thus wont be rolling as much. And the less camber will help with braking. Easiest way to change camber is to get aftermarket control arms that let you adjust camber without greatly affecting the other alignment settings. You'll still have to change front toe after changing the camber with these arms, but it will be the same toe change either side. It shouldnt effect rear toe much at all.

mx5-kiwi

Thank you for the suggestions.

I thought somewhere in the alignment page it said that this was a race alignment only and resulted in a very darty car....and "I" thought Caster was the reason....I am not sure how camber can create that sensation.

I appreciate reduced camber will be an advantage due to less body roll in the wet....and one thing i did do was increase ride height about 5mm to try and improve roll/loading. plus soften off the xidas (was a skateboard prior to those changes)

But to clarify, ultimate grip wasn't the concern at that point, the dartyness was the biggest problem on the day.

So i'm wondering what causes that and how, if possible trackside to adjust that out if required.

Leafy

iTrader: (1)

3.5° camber would make it turn in somewhat aggressively, nothing crazy though. You dont even have any front toe out. The low caster also reduces the centering force, so with the high camber and low caster the road surface might be pulling the wheel more than you normally input steering. The rear toe is IN right?

mx5-kiwi

bloody hope so!

yes, it is.

is 4 deg caster low?

also, dont get me wrong (for the record) this setup in the dry has been MAGIC....just scary and hard to be fast in the wet.

d k

iTrader: (4)

I havent raced a Miata in the rain (yet), but every other car that I have raced in the wet has always suffered from understeer.

I think if you can make the front end turn, youre doing allright.

sixshooter

iTrader: (12)

Zero camber is better in the rain.


When a tire goes over water it pushes it out the front and both sides. With negative camber like you have the water is pushed much more toward the outside by each tire. but the water is seldom equal depth on both sides or only on one side then the other. This pushes the tires and the front of the car differently left to right as you are going along. Think of how a water skier uses the camber to generate a push against the water to turn. It's not the same but it helps to visualize some of the dynamic

mx5-kiwi

thats the annoying thing, it has great front end but seems to **** the rear (or at least instantly lose the rear) at about 1/4 turn on the wheel. this is why i feel its an alignment problem.

Watching the other guys mx5 in car video he didn't have the same problem at all (though he is on 205 and im 225), he could turn in as much as he liked without the instant transition to oversteer/ lose the rear I had....I say that because it feels like its the rear twisting or something rather than a "proper" oversteer transition.

With Leafy and sixshooter saying camber....i'll have to look at that.


but begs the same question, if the hot dry setup is -3.5 deg camber and 4 deg caster...how do you reduce that at the track (roughly) to at least stay in a decent handling window should it rain....

eg. wind back(inside) both front and rear front arm alignment cams 2 markers...?

or is it essentially impossible to to do roughly.....

We cant be the only place that can have multiple weather situations in one day? (crowded house song, 4 seasons in one day comes from NZ and maybe Melbourne )

d k

iTrader: (4)

I dont think you are going to be doing caster adjustments at the track, but camber is pretty easy.
You have to keep in mind that when you adjust camber, it affects toe as well.

Whats your toe setting in the rear?

maybe toe the rear in a little bit?

i have had to toe out the rear to get the car to turn before.

bengui

Did you try to disconnect the rear anti roll bar ?
Your racing line was out of the rubber ?

sixshooter

iTrader: (12)

https://v8roadsters.com/shop/suspens...-front-uppers/

Camber changes in the paddock

mx5-kiwi

So it turns out after a new wheel alignment pre last race weekend that my new method of strapping the car to the trailer may have altered the rear toe considerably. I suspect this was the main issue.

Thank you everyone for the feedback.

d k

iTrader: (4)

no problem

Leafy

iTrader: (1)

You don't strap it to the trailer with the hooks the Japanese nicely put on the car for the purpose of strapping it down?

mx5-kiwi

No, the new trailer is to short to use the rear ones.

I do have proper wheel ones but i was being silly and ran an extra one across and through the rear wheels as well.

Just a dumb *** thing to do.