Asking Alignment Mech about Toyota

[philip]

From a qualified automobile alignment, I would like some explain about why Toyota torsion-beam suspension is set the way it is. I might add some more questions.

[davehoos]

what is type of torsion bar are you asking about.

the hilux 4x4 /hi ace van conected to the top control arm. [physical fit]

or another type like the nissan on the lower arm.[much better in straight line].

[philip]

what is type of torsion bar are you asking about.

This .... the current model Toyota Corolla 2wd in USA.



WHY are these rear wheels unadjusted with 1/8" toe-in? (or if you prefer ... Lft 0.20 degree ... Rt 0.10 degree).

[davehoos]

This set up is not ridgid like a beam axle.the assembly distorts as a function of being semi independant.with body roll you get camber change.
the GM-J car sold here[CAMIRA] was the first i know of,called trailing compound crank axle,not sold like this in all markets,works like the austin 1800[land crab].

In my books i have no specs as when new if tyres are worn then you replaced the axle.it was common for people to tie down,jack up or tow of this roll bar bending it beond repair.i now know you buy wedges to adjust the stub axle.

the toe-in setting is similar to the adjustment of non live drive front end.normally FWD has wheels have lots of inset so i would have expected the tow too be close to neutral.unless the tyres are narrow.

there is also a description of angles added to allow for distortion under braking.N14 pulsar has passive steering under brakes,it toes in under hard braking.it also aids in steering when one brake circuit has failed[diaginal circuit].N15 and maxima changed back to a solid beam due to costs and tyre wear.

[asavage]

.i now know you buy wedges to adjust the stub axle.

I've used those. A PITA to use, but it does allow alignment without parts replacement. Our alignment setup printed out a page showing which wedges to use or remove from the wedge template, and just where to put them, which aided immensely. Hunter system, old and obsolete, but still as functional and accurate as the new setups. Still used strings between F/R sensors! And when the color guns on the display started wigging out (CRT, remember those?), I could repair it without resorting to the roving Hunter tech (large buckets of $$$).

[davehoos]

I live in the Hunter Valley.there are companies that use the "hunter" description in their trading name.for many years i assumed that the hunter aligner was locally made.until i repaired one and found it to have 110 volt system and parts not easy to get.

the last one i used had 4 lamps that gave out a cross beam on to a head board and toe was adjusted by the light reflecting in a mirror on the other side lamp.

the basic type i used a technical college had 2 arms and an adjustable bubble balance.

the holden dealer i worked for had a sun electronic unit that used elastic strings hrom the heads and need lots of love and care.

the local repairer i trust to do a 4 wheel aligner has mechanical equipment from 40-50's.the draw back is you get it right with out a print out of work done.

[philip]

This set up is not ridgid like a beam axle.the assembly distorts as a function of being semi independant.with body roll you get camber change.

Well Dave ... TOYOTA calls my 2003 Corolla as "torsion beam" for the rear so ... there ya go!

In my books i have no specs as when new if tyres are worn then you replaced the axle. it was common for people to tie down, jack up or tow of this roll bar bending it beond repair. i now know you buy wedges to adjust the stub axle.

TOYOTA calls this specifically:

The toe-in setting is similar to the adjustment of non live drive front end. normally FWD has wheels have lots of inset so i would have expected the tow too be close to neutral.unless the tyres are narrow.

There is also a description of angles added to allow for distortion under braking. N14 pulsar has passive steering under brakes,it toes in under hard braking. it also aids in steering when one brake circuit has failed[diaginal circuit].

Dave ... for a typical FWD cars, driving forward only increases front toe toward MORE "toe-in." This wears tire edges.

N15 and maxima changed back to a solid beam due to costs and tyre wear.

Getting back to my question about WHY does Toyota set the "torsion beam" wheel with toe-in ... instead of set at set at "zero". I can see the mechanical done ... but I want to understand why. So ... are you saying it during times of rear brake that the torsion beam flex will move wheels toe-in to zero ... momemtarily?

[davehoos]

set the "torsion beam" wheel with toe-in ... instead of set at set at "zero". I can see the mechanical done

the toe in setting is a preload.you are setting it at rest so on the road toyota is expecting the the beam to distort and straighten up to near zero due to the drag on the wheels.this is the same as a non driving independant axle.[front 810].

added toe-in on rear axle aids stability.especialy under brakes,but i dont think that toyota set the toe in for this reason.on the nissan N14 the rear link suspension toe in under braking due to movement in the rubber bushes.

in one of the diagrams it states toe correct function.so I guess that the bush distorts with the beam.

driving axles normally toe in with axceleration.so they are set to toe-out.
FWD wheels are normally inset ,so they naturally try to toe-out on acceleration.the 2 forces are are suposed o equal.the idea is if you have single brake curcuit failure then one front applies and the oposite rear.if you lock one front the car naturally pulls to that side.the inset of the wheel rim and steering axis inclanation[sp?] pulls in the opisite direction so you can stop the car in near straight line.

toe adjustment can have more to do with stability and road noise.if you have camber on a wheel it heats up the loaded side of the tyre,normally toe is added to correct this.if you lean a tyre in it will also pull that way.like a motor bike.if you toe out a tyre with - camber the tyre will get hot.

[philip]

SNIP- Added toe-in on rear axle aids stability. especialy under brakes, but i dont think that toyota set the toe in for this reason.

THEN ... what is the guess for your reason?

Driving axles normally toe in with axceleration.so they are set to toe-out. FWD wheels are normally inset ,so they naturally try to toe-out on acceleration.the 2 forces are are suposed o equal.

You mean to say your FWD front wheel is set at Toe-In when the vehicle is idle. You further say that while accelerating the vehicle that your front wheel Toe-In now rotates toward Toe-zero. That posit is incorrect.

Correctly Stated:

http://extremegarage.com/techtips/stechtip.htm

"Generally speaking, rear-drive vehicles usually require that front toe is set at a slight toe-in, usually 1/16 inch to 1/8 inch. This is done to anticipate the likely toe-out movement as the vehicle travels forward, due to imperfect tolerances in the front suspension bushings / bearings. Many front-drive vehicles often specify a toe-out setting on the front wheels, in anticipation of forward acceleration wherein the front tires may 'crawl' inboard."

[davehoos]

Driving axles normally toe in with axceleration.so they are set {AT REST}to toe-out.

they CRAWL back to near zero.

second part.

FWD wheels are normally inset [of the mounting flange] ,so they naturally try to toe-out on acceleration.

and toe-in on braking.

the front suspenson moves as they are soft mounted.performace cars are ridgid to reduce distortion.
the tortion beam is not RIGID.

the tyre tread moves independ[small amounts] of the road wheel.

NOTE:
There is a relationship between camber and toe needed to compensate[not in that artical] for normall running.if you have lots of toe in the car will wobble in a straight line.same deal with lots of camber.some tyres are designed to have lots of camber standard.

THEN ... what is the guess for your reason?

stability under serious performace needs.I dont have much faith in toyota design.personal thoughts.toyota target potential owners very well and then make the model cheeper over time.they seem to spend lots of money on fixings and not on performance.this is to suit-A to B commutors needing no fuss trouble free,quiet and safe.10 yr owners and retied couples that probably had a larger toyota before.
there are several other cars sold in australia with this type of rear end design and they are not marketed as performace models but as safe family sedans giving good ride quality.

[philip]

Driving axles normally toe in with axceleration.so they are set to toe-out.

they CRAWL back to near zero.

What you mean to say is:
1. A FWD begins at TOE-OUT.
2. Then, as the vehicle is accelerated, the toe-out is "crawled" toward "zero." We agree.

Second part. FWD wheels are normally inset,so they naturally try to toe-out on acceleration.
and toe-in on braking. .

I do not understand what you refer with "inset". TOE-IN? At any rate, you are misstated by saying "naturally try to toe-out on acceleration. " You are also misstated in saying braking causes toe toward (initial Toe-Out towards zero or at zero toward Toe-In) " REMEMBER again ... the discussing here is ONLY about FWD.

The front suspenson moves as they are soft mounted.performace cars are ridgid to reduce distortion.
the tortion beam is not RIGID.

Dave ... that name "RIGID" is your own special or unique name that neither I not Toyota has even stated "rigid" here. Go look.

NOTE:
There is a relationship between camber and toe needed to compensate[not in that artical] for normall running.if you have lots of toe in the car will wobble in a straight line.same deal with lots of camber.some tyres are designed to have lots of camber standard.

Dave ... you say in general. You do no specific about vehicle FWD vs RWD, nor RWD rear axle AMOUNT of TOE (IN or OUT) that "wobbles".

This discussion is about a FWD's rear torsion beam ONLY.

[davehoos]

Inset is the measurement of the of the mounting flange to the center line of the road wheel. a large inset/offset measurment will cause the roadwheel and tyre to distort due to drag.an alowance must be engineered in depending on the speeds the car will be used.

fwd and 4wd to allow for the CV joint to be close to the

Steering axis inclination (SAI)

King pin inclination,and have wheel bearings,brakes need road wheel inset.

older RWD 2WD have Offset.dished out.my japanese skyline has 25-35 mm offset and australian built model has 35-50 mm.it runs different tyres and more negative camber,rear axle is ridgid .in australia it was expected that the car will average higher speeds.my 910 manual shows positive camber setting,ive never seen one that was adjusted that way.

Scrub radius.this is measurement at the tread contact beteen the SAI and the center line of the tyre.increasing srub radius efects the load on the steering.ideal is zero.on the rear axle there is no measure for for srub radius but as the suspension moves giving it a steering effect so it will have a theretical number.more important to you in this discusion is the inset measurement needed on the front axle.the friction drag of the rear tyres will naturally bend the tortion beam reducing the track.this changes the toe setting the road wheels.

today i worked on a 90's mazda 121 BUBBLE.it had an near identical rear axle setup.it was sold as a dependable shopping trolley.it had feathered rear tyres.no obvious camber angle.

WOBBLE.
there are a few technical terms for this depending on the compliant.tram track is a common one.cars with positive camber will be sensitive to road camber changes.making them feel unstable.i heard of cars crashing over due to dropping into the depresions of heavy vehicles in the tar.or dried earth roads.

RIDGID.my mitubishi lancer has a tortion beam,unlike your toyota the beam is a rigid like axle with 2 arms weilded to it and a panhard rod.with simple up/down movement there is no toe or camber change,but with body roll there is.
the GM car has the coil spring forward near the joint on the beam,so when the car is loaded you get camber and toe changes.
ridgid is a term for a non independant axle live or trailing.my truck liecence is for a heavy ridgid vehicle.
a tortion beam is a ridgid axle but its not ridgid.

I dont have any dealer training manuals for this.the coment i got was that this model has more cup holders than the old one and its not japanese.

[philip]

Hunter system, old and obsolete, but still as functional and accurate as the new setups. Still used strings between F/R sensors! And when the color guns on the display started wigging out (CRT, remember those?), I could repair it without resorting to the roving Hunter tech (large buckets of $$$).

People in Australia and Mexico still have...

[asavage]

Uh, ours was not quite that old.

[davehoos]

the hunter alighner i used had for a projector a round cylinder with the bulb in the bottom.to focus the beam you moved the bulb holder and clamped it in place it had a smaller cylinder on top.with the mirrors.the hassel was that it moved after initial setup calibration freely and got knocked when adjusting suspension.

it was fixed onto the wheel rim then you set the bubble and a SAI reading to zero.then you undone to clamp on the bearing and rotated the tyre.and reset the bubble this aligned the projector with the wheel.then you read off the head board camber.you then adjusted toe with a beam shining on 2 mirrors.you then checked toe-out on turns i think from memory the outside wheel was 20 deg in.you clamped the the projector and turned it to oposite tyres 20 deg in and read off caster and toe on turn.

ive been into a few workshops that had these visualiners headboards in there pit.the aligning tools had long gone.