[Mk2] [Generic] Rev2+ caster adjustment

[Peterwolf]

Long to short: In Rev1 is possible to adjust caster whithout modifications, but in Rev2 don't.

In a Rev2 is cost efective/better install the Rev1 tension rods with polybushes, or go all the way to Tein/Cusco pillowball tension rods?
What's are the differences?

If I use the Rev1 parts, how much adjustment can I have?

What should you do if you want to adjust caster?

[Peter Gidden]

In a Rev2 is cost efective/better install the Rev1 tension rods with polybushes, or go all the way to Tein/Cusco pillowball tension rods?
What's are the differences?

Neither solution is "better". Depends what you want to do with the car. Spherical bearings wear out quickly on public roads, so polybushes would be best for road use.

For a race car, use spherical bearings. Less "sticktion" and zero deflection.

If I use the Rev1 parts, how much adjustment can I have?

More than you will ever need.

What should you do if you want to adjust caster?

Lengthen/shorten the bar using the castor adjusting nuts on the end of the rod. But surely you know that already?

[Peterwolf]

What should you do if you want to adjust caster?

Lengthen/shorten the bar using the castor adjusting nuts on the end of the rod. But surely you know that already?

I wrote that phrase with a meaning of: What path would you take if it's with you?
I'm sorry for the misunderstanding, but English isn't my native language

I use my car both in tracks and roads, so by what you told is better go with Rev1 parts and polybushes.

I already have the polybushes, but can't find the base part where the tension rod is fixes to the chassis. What's the part number?

Thanks for the reply!

[Peterwolf]

Just found!

Rev1
57107 BRACKET SUB-ASSY, STRUT BAR, RH
57107‑17040

57108 BRACKET SUB-ASSY, STRUT BAR, LH
57108‑17040

Rev2+
57107 BRACKET SUB-ASSY, STRUT BAR, RH
57107‑17050

57108 BRACKET SUB-ASSY, STRUT BAR, LH
57108‑17050

[Peter Gidden]

I use my car both in tracks and roads, so by what you told is better go with Rev1 parts and polybushes.

I already have the polybushes, but can't find the base part where the tension rod is fixes to the chassis. What's the part number?

Thanks for the reply!

I think for low cost, low maintenance and comfort go with Rev1 parts and polybushes.

I'll see if i can find part numbers for strut bar mountings.

You could put post in items wanted forum?

[Peterwolf]

You could put post in items wanted forum?

Posted @ wanted forum.

It's not even for the comfort, but more for low cost and maintenance.

Regarding the suspension I already have the following parts:
- BC Racing Coilovers, pillowball top mounts, front camber;
- Rear camber bolts;
- Whiteline F/R ARBs;
- Full Prothane polyurethane kit;
- Full geometry alignment with -2.5º camber with slight toe-out at front, -2.2º camber with slight toe-in at rear;
- 205/45r16 front and 225/45r16 rear Kumhos V70A (to be installed).

And more things that I can't remember
Front caster adjustment is the only thing that currently I can't have.

[shinny]

Front caster adjustment is the only thing that currently I can't have.

Your setup and geometry sounds pretty much identical to mine, although you're running a smidge more camber and I have phoenix power roll centre adjusters too.

My question is, how does adjusting the caster help? AFAIK it's mostly to do with steering effort, no?

[bobhatton]

Yes

[Peterwolf]

I want to try
Is the only thing that I can't adjust, so why not?

Also I have a slight difference between left and right wheel, so with adjustable caster I can fix that.

[GreddyMR2]

As I understand, the bigger caster you have, the more camber you get in turn.

[bobhatton]

As I understand, the bigger caster you have, the more camber you get in turn.

Yes up to a point but that is not the way to set camber

[kingsley]

I've no idea about this so just asking - would reducing the castor increase steering responsiveness?

I drove a friend's MX-5 once and was surprised at how quickly the car started to steer the moment you turned the steering wheel. Was really fun. My MR2 seems to have a bit of a delay before it starts to steer. There's nothing wrong with it as far as I can make out, no play or anything. Is that called turn in understeer? Fairly new to all this ...

The *most* responsive steering I've ever encountered was on a Westfield. That thing was in a different league!

Cheers,
Kingsley.

[shinny]

A little toe out will help initial steering response

[kingsley]

A little toe out will help initial steering response

Is there a somewhat less scary way of sharpening the response?

Cheers,
Kingsley.

[shinny]

A little toe out will help initial steering response

Is there a somewhat less scary way of sharpening the response?

Cheers,
Kingsley.

lol - it's not scary!

[bobhatton]

I've no idea about this so just asking - would reducing the castor increase steering responsiveness?

I drove a friend's MX-5 once and was surprised at how quickly the car started to steer the moment you turned the steering wheel. Was really fun. My MR2 seems to have a bit of a delay before it starts to steer. There's nothing wrong with it as far as I can make out, no play or anything. Is that called turn in understeer? Fairly new to all this ...

The *most* responsive steering I've ever encountered was on a Westfield. That thing was in a different league!

Cheers,
Kingsley.

Fit a 280mm wheel. Steering is very responsive then

[kingsley]

A little toe out will help initial steering response

Is there a somewhat less scary way of sharpening the response?

Cheers,
Kingsley.

lol - it's not scary!

Oh really, I thought your initial suggestion was tongue in cheek! I had a car that accidentally had a bit of toe out on the rear once and high speed hard braking was very vague - very brown trouser moment a few times. Once the geometry was fixed it was fine.

I thought front toe out made the steering wonder about and feeling vague. Not that I have any direct experience of it.

Cheers,
Kingsley.

[shinny]

Oh really, I thought your initial suggestion was tongue in cheek! I had a car that accidentally had a bit of toe out on the rear once and high speed hard braking was very vague - very brown trouser moment a few times. Once the geometry was fixed it was fine.

I thought front toe out made the steering wonder about and feeling vague. Not that I have any direct experience of it.

Cheers,
Kingsley.

All things in moderation. A little front toe in OR toe out are nice stable setups - toe out is better at initiating the turn but then washes slightly. Just think about the weight transfer and you'll see it makes sense. Too much toe out feels very vague, just as too much toe-in will feel pretty odd too.

The rear should pretty much always be toe'd in AFAIK. I did once end up with a parallel setup which was ok but a bit twitchy.

[kingsley]

A little front toe in OR toe out are nice stable setups - toe out is better at initiating the turn but then washes slightly.

Hi,

What do you mean by "washes slightly" ?

BTW, can't help thinking we've hijacked this thread a bit

Cheers,
Kingsley.

[shinny]

A little front toe in OR toe out are nice stable setups - toe out is better at initiating the turn but then washes slightly.

Hi,

What do you mean by "washes slightly" ?

BTW, can't help thinking we've hijacked this thread a bit

Cheers,
Kingsley.

Taken from here: http://www.ozebiz.com.au/racetech/theory/align.html

When the wheel on one side of the car encounters a disturbance, that wheel is pulled rearward about its steering axis. This action also pulls the other wheel in the same steering direction. If it's a minor disturbance, the disturbed wheel will steer only a small amount, perhaps so that it's rolling straight ahead instead of toed-in slightly. But note that with this slight steering input, the rolling paths of the wheels still don't describe a turn. The wheels have absorbed the irregularity without significantly changing the direction of the vehicle. In this way, toe-in enhances straight-line stability.

If the car is set up with toe-out, however, the front wheels are aligned so that slight disturbances cause the wheel pair to assume rolling directions that do describe a turn. Any minute steering angle beyond the perfectly centered position will cause the inner wheel to steer in a tighter turn radius than the outer wheel. Thus, the car will always be trying to enter a turn, rather than maintaining a straight line of travel. So it's clear that toe-out encourages the initiation of a turn, while toe-in discourages it.

The racecar engineer who corner weighted and aligned my car the (old fashioned way) explained it to me like this:

With front toe out, as you turn the steering wheel the inside wheel, which is pointing slightly more into the turn, gives you the initial response. However the weight then moves to the outside wheel which isn't pointed so much into the corner, causing your turning radius to widen. Conversely with toe-in, the initial turn in isn't as good but as the weight transfers to the outside wheel the turn radius gets tighter as the outside wheel is pointed more into the corner.

Regarding rear toe:

Toe settings at the rear have essentially the same effect on wear, directional stability and turn-in as they do on the front. However, it is rare to set up a rear-drive race car toed out in the rear, since doing so causes excessive oversteer, particularly when power is applied.

I must admit, I love having gentle front toe-out as it brings the car alive - but combined with camber, it does make it wander a little over uneven roads and the tramlines on motorway slow lanes. I'd never even consider as aggressive a setup on my BMW daily drive!! I guess you pay your money and take your choice really