MA71 handling and wheel alignment settings Q's

[boxh34d]

Hi guys.

I'm wanting to improve the handling of my MA71 supra. I drive semi regularly on normal roads, along with a fair bit of work through the twisties in the hills, and a couple of track days a year. The current setup is Lovells sports lowered springs, Koni adjustable shocks and a full alignment suitable for 'spirited street driving and a bit of track work'. I don't know the exact specs, I lost them ages ago after I had the alignment done.

I'm very happy with the general ride qualities, with the spring / shock combo being quite firm and stable without being harsh, allowing it to soak up a bit and not get upset by the frequent mid corner bumps / potholes etc found on country roads.

However, when at the track, I seem to have a few problems:
Upon corner entry, it seems the front wheels are actually rolling under a bit, with the tyres showing signs of wear on the outside edge. This is in addition to the fairly big amount of body roll and boat like behaviour in the front end when pushed hard. All in all, it is very prone to understeering when being pushed and quite slow to transition between direction or from braking to initial turn in.

I'm thinking that this could be due to a couple of things:
The fairly tired control arm bushes letting the whole assembly tuck in when loaded;
The factory sway bar under the front being too thin / soft;
The wheel alignment not really being aggressive enough in one or all the qualities;
Other or all of the above?

At this stage I'm thinking of getting some new urethane control arm bushes, and a thicker sway bar to stiffen it up in the front end. I can get a 30mm bar from Whiteline, (Don't know how that compares with the stock size?), but I'm not sure on the bushes, I'll have to do some searching. Is it worth getting offset ones to allow some more adjustability if available?
Have people found the Whiteline bars for the A70 any good?
Has anyone had a good play with different alignment settings (both front and rear) and found some numbers that work really well, and would you care to share them?

Thanks for any help in advance, it's much appreciated.

[codez]

I'm also in need of front and rear control arm bushes for my Z20 Soarer.
I have tried contacting Suprasport but have had no reply.
So, if anybody knows where I can get some (*A70, *Z20 all the same) that would be great

Thanks

[ecko]

coffee has some bc coilovers for sale cheap buy those

superpro make bushes, available from ajps or burson's

swaybars from either whiteline or if you have the cash cusco etc

[mullett]

Front tyre edge wear is totally normal for a track day on street Tyres unless you're running upwards of 5degrees of camber...if you find it too understeery on the track, it's probably a combination of your driving style and the way it's setup. By track do you mean circuit or gymkhana?

[midnight_purple_GA70]

ide suggest making sure front upper and lower control arms are done... Ball joints... That should help with improving the response of the steering...

I have tien ha coilovers and the above bushes replaced and that made a big improvement...

Have yet tried to stiffen things up with sway bars and strut braces...

[boxh34d]

Front tyre edge wear is totally normal for a track day on street Tyres unless you're running upwards of 5degrees of camber...if you find it too understeery on the track, it's probably a combination of your driving style and the way it's setup. By track do you mean circuit or gymkhana?

Circuit - Winton raceway.
Have tried a number of different entry styles, and have given my mechanic a crack at it as well (15 years of hillclimbs and sprint racing), and still have the same problem. If I'm quite slow on entry, and allow plenty of time for settling after braking, it steers quite nicely, as soon as any real corner speed is tried, it is prone to understeer.

[LeaThaL]

I'm about to do front control arms with superpro Polly bushes and balljoints on my ga70 as their all really tired so ill let you know the results but after driving my vr with superpros I doubt anything under spectacular handling afterwards

[trdee]

what tyres are you using and what kinds of pressures do you put into em?

[boxh34d]

what tyres are you using and what kinds of pressures do you put into em?

Toyo T1R's in 235.40.18 and 265.35.18. Nice and grippy both wet and dry, though obviously not ideal for track work. Have tried pressures ranging from 30 to about 40, and have settled on 36PSI hot on the track, about 34 cold for the road.

[boxh34d]

I'm about to do front control arms with superpro Polly bushes and balljoints on my ga70 as their all really tired so ill let you know the results but after driving my vr with superpros I doubt anything under spectacular handling afterwards

Great to hear an update when your done, what kind of time frame were you looking at?

Also, thanks for everyone who has had input - + rep were due.

Nothing else to add?

[codez]

I couldnt find anything for the rears locally, so I''ve ordered Energy Suspension bushes through Suprasport and I'll be using Superpros in the front.
Now im also considering new balljoints too while im at it.

[jazz9]

I found this helpfull from another thread

http://www.toymods.org.au/forums/sho...on-for-dummies

This is somthing I came across on another site and found it interesting for those contemplating playing with suspension setups.

Quite obviously there are a number of things that effect suspension but I look at this as somewhat of a trouble shooting guide as to what planned changes may create, or why problems you have and how/why they can be solved.

Front spring rate increase:
More under steer; increase in proportional weight transfer to the front when rear wheel rate is not increased; reduces front traction when rear rate is not changed.
Usable adjustment: 150-600 lbs/in
Symptoms of too much adjustment: terminal under steer; front of car hops in corners; excessive wheel spin on inside front tire on FF cars.

Front spring rate decrease:
Less under steer; decreases proportional weight transfer to the front when rear wheel rate is not increased; increases front traction when rear rate is not changed.
Usable adjustment: 150-600 lbs/in
Symptoms of to much adjustment: Too much over steer; over steer then under steer if spring is so soft that the car bottoms out on lean, car bottoms out excessively with a jolting ride.

Rear spring rate increase:
More over steer; increase in proportional weight transfer to the rear when front wheel rate is not increased; increases rear traction when front rate is not changed.
Usable range: 100-600 lbs/in
Symptoms of too much adjustment: too much over steer; sidestep hop in corners; twitchy; pretty scary.

Rear spring rate decrease:
Less over steer: decreases proportional weight transfer to the rear when front wheel rate is not changed; increases rear traction when front rate is not changed
Usable range: 100-600 lbs/in
Symptoms of too much adjustment: car under steers; if way to soft car under steers then over steers as car bottoms out on lean; car bottoms out excessively with a jolting ride.

Front anti-roll bar stiffer:
more under steer
Usable range: none to 1.25 inches in diameter
Symptoms of to much adjustment: terminal under steer; lifts inside front tire off the ground witch can cause massive wheel spin on FF cars; also not good for most effective tire usage as inside tire is now doing nothing.

Front anti-roll bar softer:
less under steer
Usable range: none to 1.25 inches in diameter
Symptoms of to much adjustment: overstate scary; more like fun

Rear anti-roll bar stiffer:
more over steer
Usable range: none to 1 inch in diameter
Symptoms of too much adjustment: Big-time over steer. Can cause inside rear tire to lift off the ground.

Rear anti-roll bar softer:
less over steer
Usable range: none to 1 inch in diameter
Symptoms of to much adjustment: under steer; slow and boring

Front tire pressure higher:
less under steer by reducing slip angels on most tires
Usable adjustment: up to 55psi hot
Symptoms of too much adjustment: no traction- tire crowned so more under steer; adds wheel spin in FF cars; jarring ride; center of tire wears out

Front tire pressure lower:
more under steer by increasing slip angles on most tires
Usable adjustment: not less then 20psi
Symptoms of too much adjustment: edges of tire wear quickly because tire is folding over; feels mushy; tires chunk because low pressure means heat build up.

Rear tire pressure higher:
less over steer by reducing slip angles on most tires
Usable range: up to 45psi hot
Symptoms of too much adjustment: no traction—tire is crowned so more over steer; bad wheel spin on FR cars; jarring ride; center of tire wears out.

Rear tire pressure lower:
more over steer by incresing slip angles on most tires.
Usable range: not less then 20psi
Symptoms of too much adjustment: edges of tire wear quickly because tire is folding over; feels mushy; tires chunk because low pressure means heat build up

More negative camber front:
less under steer because of better lateral traction as tread is flatter on the ground under side load.
Usable range: up to 3.5 degrees negative
Symptoms of too much adjustment: poor braking; car is road crown sensitive; twitchy; front tires wear on inside edge

More negative camber rear:
less over steer because of better lateral traction as tread is flatter on the ground under side load. More rear grip
Usable range: up to 2.5 degrees negative
Symptoms of too much adjustment: more over steer; car feels twitchy in back; tires wear out on inside edge; less breakaway warning when limit is exceeded.

Ride height to low (typical beginner mistake):
car is twitchy with unpredictable dynamics. Bump steer make you life miserable.
Usable range: usually 1.5-2.0 inches lower then stock unless car has been modified to go lower.

Symptoms of too much adjustment:
everything that could possibly go wrong: sudden over/under steer; twitchy due to bump steer; very harsh ride; premature tire wear.

Toe in – front:
car is stable going straight. Turn in is average
Usable range: 0-1/8th inch
Symptoms of too much adjustment: car has slow twitchiness under braking; feels odd; kills outside edge of tires

Toe out – front:
Car turns in well; works pretty well on FF car as they tend to toe-in under load.
Usable range: 0-1/4 inch
Symptoms of too much adjustment: Car is really twitchy under braking; car wanders on straight road; kills inside edge of tire

Toe in – rear:
car is less likely to over steer when the throttle is lifted
Usable range: 0-1/8th inch
Symptoms of too much adjustment: weird, slow, rocking movement in back; feels slow but still unstable; wears outside edge of tires.

Toe out – rear:
Helps car rotate useful in low speed and slalom courses; very common on FF pro rally cars.
Usable range: 0-1/8th inch
Symptoms of too much adjustment: not to good for street driving; causes lift throttle over steer; makes violent side to side rocking motions in the rear; tie wears on inside more.

Positive front caster:
helps stability; suspension will get more negative camber when turning; reducing positive caster reduces steering effort. (Negative caster is not usable)
Usable range: 4-9 degrees positive
Symptoms of too much adjustment: can increase under steer especially in cars with wide low-profile tires. Can increase steering effort.

Single adjustable shock stiffer:
Better turn in; better transient response; causes slower onset of over/under steer by slowing weight transfer depending on what end of the car is adjusted.
Symptoms of too much adjustment: suspension becomes unresponsive; ride gets harsh; car skips over bumps, loosing traction; Causes a big delay in weight transfer resulting in strange handling like under steer then late corner stage over steer.

Single adjustable shock softer:
slower transient response; quicker onset of over/under steer
Symptoms of too much adjustment: car oscillates due to under dampened spring motion, like a boat. Car gets twitchy in turns. Feels unstable.

Taken from www.AE86drivingclub.com.au