wheels-inmotion

There could be an issue with the toe angle pre-loading the tyres sidewall, another common reason is a worn engine mount off-setting the drive train. What happened between the time everything was ok and the complaint?

The rubber gaiters on the steering rack eventually need changing, this is done without removing the rack, well the steering arm anchor point is under the gaiter. Alignment centres and technicians are totally unregulated, anyone can set the chassis. The people who install the machine only train them on the procedure not the theory of chassis dynamics, this was one of the reasons i built the wheels-inmotion webby years ago, just so the public can get a little "heads up" before letting fast fit loose on their car.

If the wear is in the steering arms knuckle then yes it needs to be replaced.... It's a non-mechanical part so i fail to justify the price quoted.... This sort of part normally sells for around £80+ each.

Historically to invite oversteer you would increase the torsional rate at the front and reduce it at the rear, it's not uncommon on various marques that they remove the rear arb, obviously i don't recommend this but it gives an idea of how the arb controls the roll centres during transition. If the cars lifting a paw on cornering it would be better to source a "anti-lift" kit?.... this allows the front castor angle to sweep further during cornering, belaying lateral rigidity to some extent.

Depending on the suspensions configuration lowering doesn't always deepen the camber at the rear, if you had "near" to positive positions before then it's probable you still have. As for the wear, there are two main reasons for this... 1: On a turn each wheel has a different radius, obviously the left turn encompasses the smallest radius impacting scrub on the NS tyres. This scrub would agitate the NSR because unlike the front there is no Ackermann angle to assist. 2: On a right turn/ bend the suspension is subjected to transitional loads, these loads produce roll front and rear and a roll couple, the rear outer wheels camber position should migrate under lateral compression forcing a more aggressive negative camber position and maintain the tyres saturation grip limits. This is all good and fine assuming the static camber position is correct, seemingly on your car it's not.

No.... the brakes cannot influence the wear.

Before you do anything else can you move the front wheels/tyres side-to-side then test again.

Good news the steering straight now, although the before/ after values seem very close. The explain the comment on the bottom of the printout... During the initial measurements the machine is disinterested in the steering wheels position, it's only after the chassis has been measured and the before positions locked that the technician can see the steering is offline, so he manually comments on the steering position to justify a correction at the chassis.

Yes they have, just be a little carefull with the price though.... Get a "worst case" figure up front.

Crown/ slope whatever, both offer the same pneumatic distortion, i fail to see your argument? Geometric stagger to belay the "slope" exists like it or not. If you have a car that rides the "slope" (opposite camber) then i advise some chassis attention.

Proving wrong reads harsh, that's not what i'm trying to do. Historically the target data insists on absolute symmetry from the Geometry calibration, the only time this will differ is on high end marques where a camber/ castor stagger is used to belay the road crown, all this does is extend the "eventual drift" all cars experience due to the crown.

Ken this is in no way demeaning, derogatory or trying to belittle you but that comment is absolutely incorrect, i have read it many times before and wonder how you came to this conclusion? If it were a design feature wouldn't this diversion take you into the nearest tree or bus stop instead.

That's what the tyre industry have lead you to believe, tracking or "wheel alignment" is a shared angle, both front wheels own the position so it cannot make the car pull.

It's probable you have a camber or castor issue "wheel alignment" will not see this... On your car these angles are fixed but it's possible to relocate the crossmember in order to optimise the positions.

Not for the modified chassis... don't forget you can afford a lower camber with uprated coils since there's less dynamic gains..... normally?

It's actually a good thing the tyres blew since this absorbed some of the energy. Having said that if the Tracking was a long way out it does suggest one of the secondary angles is wrong, namely castor, additionally it's wise to check the steering arm in case this is bent, obviously if it is this would explain the very wrong toe angle. You need to get an image of the current chassis position, this is done using a full Geometry machine, this will measure the chassis in all three axis X, Y, Z so with a little trigonometry identify any bent components. Also if needs be the sub-frame and rear beam can be optimised, their anchor points are not as surgical as we a led to believe.

Sorry my mistake, the front can definitely be optimized though.

The Octavia has less natural adjusters than the 5 but.....? The rear beam and front cross-member can be moved to optimize incorrect angles, in particular the castor angle which causes much distress to the Octavia.

I wrote a check list some years ago for a national fast-fit chain, it was adopted as an s.o.p but i bet few really used it. ....................................... Sequential Alignment Fault Diagnostics Condition: Premature tyre wear Possible cause: Incorrect tyre inflation Wheel alignment out of tolerance Suspension components worn Incorrect ride height (1) Distorted wheel Incorrect torsion bar adjustment Loose or worn wheel bearings Worn shock absorbers Tyres out of balance Pulls to one side Possible cause: Incorrect tyre inflation Brakes binding (2) Mismatched tyres (3) Broken coil spring (1) Power steering valve not centred (4) Wheel alignment out of tolerance (5) Defective wheel bearings (6) Damaged anti roll bar drop links Incorrect castor angle (7) Wear on nsf tyre (8) Heavy steering Possible cause: Drag link seized Ball joint seized Steering linkage seized (9) Power steering fluid low (10) Power steering belt loose Power steering pump defective (11) Incorrect wheel alignment (12) Damaged steering rack Damaged suspension components (13) Vehicle wandering Possible cause: Worn or damaged suspension Worn track control arm or tie rod (14) Loose or worn wheel bearings (6) Incorrect tyre inflation Anti-roll bar drop link defective Wheel alignment out of tolerance (5) Broken coil or sagging coil spring (1) Method of Testing (1) Measure ride height from mid wheel arch to the centre of the hub, except no more than 10 mm difference across any given axle, a broken or sagging coil spring can cause a pull even from the rear (2) If checking when cold, look for hot spots or blued discs, (3) Rotational/ directional/ asymmetrical/ mismatch bias, (4) Check track rod threads are even, ignore the position of the steering wheel, may prove steering wheel has been re-set, (5) Will need to be in excess of 1 degree/ 6 mm normally negative/ toe out, (6) Worn tapered rear wheel bearings will change the camber angle and cause a pull/ front wheel bearings are harder to test cold/ hold the coil spring and spin the wheel, if you feel a rumble then the bearing is worn, (7) In most cases will only go wrong by an impact, tell tale sign, the wheel alignment will be a long way out, if a full wheel geometry is not available, check to see if the wheels have excessive set back, measure mid-wheel to mid-wheel, front to rear, ns and os, if the lowest is the direction the vehicle is pulling,then the castor is probably wrong, avoid setting just the wheel alignment as this will not resolve the pull and probably generate a complaint, (8) Due to the road layout (UK) the nsf tyre has a smaller turning radius than the osf, this will cause the outside of the nsf tyre to wear more than the osf, this pattern of wear is unavoidable, if the vehicle is pulling left and the nsf is showing signs of wear, move the front wheels side to side, or front to rear, then test and adjust wheel alignment, non compliance is a common reason for an after adjustment complaint, (9) Common on Fiesta/ Escorts, jack up front wheels and turn steering, if (terminology differs) the steering column/ linkage/ coupling/ joint, is seized it will go tight 180 degrees, � turn, (10) The more the steering is turned, the more the pump will scream, (11) Jack up front wheels, start engine and rev to about 2500 rpm observe if the steering wheel moves, also manually check the steering's resistance by moving the steering wheel from left to right, (12) Will need to be in excess of 1 degree/ 6 mm positive/ toe in, (13) Disconnect track rod from strut, turn strut from side to side, and feel if metalastic bush Is seized---- (14) If front wheel drive the wander will deviate left/ right under acceleration/ deceleration, beware a worn engine mount on a front wheel drive vehicle can also cause this, by off setting the drive shafts, rear wheel drive will deviate mainly under braking, or coming of bumps,

I wrote a check list some years ago for a national fast-fit chain, it was adopted as an s.o.p but i bet few really used it. ....................................... Sequential Alignment Fault Diagnostics Condition Premature tyre wear Possible cause Incorrect tyre inflation Wheel alignment out of tolerance Suspension components worn Incorrect ride height (1) Distorted wheel Incorrect torsion bar adjustment Loose or worn wheel bearings Worn shock absorbers Tyres out of balance Pulls to one side Possible cause Incorrect tyre inflation Brakes binding (2) Mismatched tyres (3) Broken coil spring (1) Power steering valve not centred (4) Wheel alignment out of tolerance (5) Defective wheel bearings (6) Damaged anti roll bar drop links Incorrect castor angle (7) Wear on nsf tyre (8) Heavy steering Possible cause Drag link seized Ball joint seized Steering linkage seized (9) Power steering fluid low (10) Power steering belt loose Power steering pump defective (11) Incorrect wheel alignment (12) Damaged steering rack Damaged suspension components (13) Vehicle wandering Possible cause Worn or damaged suspension Worn track control arm or tie rod (14) Loose or worn wheel bearings (6) Incorrect tyre inflation Anti-roll bar drop link defective Wheel alignment out of tolerance (5) Broken coil or sagging coil spring (1) Method of Testing (1) Measure ride height from mid wheel arch to the centre of the hub, except no more than 10 mm difference across any given axle, a broken or sagging coil spring can cause a pull even from the rear (2) If checking when cold, look for hot spots or blued discs, (3) Rotational/ directional/ asymmetrical/ mismatch bias, (4) Check track rod threads are even, ignore the position of the steering wheel, may prove steering wheel has been re-set, (5) Will need to be in excess of 1 degree/ 6 mm normally negative/ toe out, (6) Worn tapered rear wheel bearings will change the camber angle and cause a pull/ front wheel bearings are harder to test cold/ hold the coil spring and spin the wheel, if you feel a rumble then the bearing is worn, (7) In most cases will only go wrong by an impact, tell tale sign, the wheel alignment will be a long way out, if a full wheel geometry is not available, check to see if the wheels have excessive set back, measure mid-wheel to mid-wheel, front to rear, ns and os, if the lowest is the direction the vehicle is pulling,then the castor is probably wrong, avoid setting just the wheel alignment as this will not resolve the pull and probably generate a complaint, (8) Due to the road layout (UK) the nsf tyre has a smaller turning radius than the osf, this will cause the outside of the nsf tyre to wear more than the osf, this pattern of wear is unavoidable, if the vehicle is pulling left and the nsf is showing signs of wear, move the front wheels side to side, or front to rear, then test and adjust wheel alignment, non compliance is a common reason for an after adjustment complaint, (9) Common on Fiesta/ Escorts, jack up front wheels and turn steering, if (terminology differs) the steering column/ linkage/ coupling/ joint, is seized it will go tight 180 degrees, ½ turn, (10) The more the steering is turned, the more the pump will scream, (11) Jack up front wheels, start engine and rev to about 2500 rpm observe if the steering wheel moves, also manually check the steering's resistance by moving the steering wheel from left to right, (12) Will need to be in excess of 1 degree/ 6 mm positive/ toe in, (13) Disconnect track rod from strut, turn strut from side to side, and feel if metalastic bush Is seized---- (14) If front wheel drive the wander will deviate left/ right under acceleration/ deceleration, beware a worn engine mount on a front wheel drive vehicle can also cause this, by off setting the drive shafts, rear wheel drive will deviate mainly under braking, or coming of bumps,

Tram-lining is a topic i covered in wim-web, maybe this brief explanation will help? ................................................... This distressing condition is when the driver needs to make involuntary corrections to the steering in order to maintain directional control. Tram-lining complaints have a wider audience due to the advent of the RFT (Run-Flat-Tyre) the "extra load sidewall" and the ever lower tyre aspect ratio (sidewall). The physics of Tram-lining is the communication between the tyres contact patch, the rigidity of the tyres sidewall and the wheel rim, in the advent of any road imperfection the tyre can no longer suppress lateral displacement allowing the sidewall to pass energy to the wheel and then the steering, this energy requires the driver to counteract with a correction to the steering wheel. Tram-lining can be controlled by the manipulating tyre pressure and the front Toe angle, although the correct Toe angle would need to be found.

I drive many cars, from donkey's to supercars "so what?"..... The objective of the post was to enlighten anyone that's interested how we (humans) perceive the challenge of driving, our advantages and disadvantages. The construction came from Prodrive, TDiplc and wheels-inmotion and is nothing more than a "oh really" post members can make of what they will?

The topic is constructed by wim (wheels-inmotion) TDiplc (Torque Developments International plc) with a Pro-drive accreditation. Before we can consider chassis dynamics, first we need to understand "US". The demands on manufacturer's to deliver faster, better handling cars has been surpassed by our inability to drive them. The evolution of systems like ABS and interactive suspension, to mention a few allows the cars intelligence to replace our miss givings.... "Why" Part 1 Humans The driving process: • Step one: A driver looks at the oncoming road and estimates the required inputs to complete the task at hand, we make this estimate based on a model of the car held in our memory, the more accurate this model the more accurate our initial guess. • Step two: An “Open Loop” input is made according to our guess • Step 3: Then “Closed Loop” trimming modifies these inputs to take account of emerging conditions or errors in the initial guess There are 3 main channels of feed back used for “Closed Loop” driving 1. Visual feedback 2. Inner ear (yaw rate, lateral acceleration etc) feedback 3. Muscle tension or Steering wheel torque feedback It is through these communication channels that a car can speak to a driver. Ok firstly, the drivers eyes…. Processing visual stimuli is actually quite a complex procedure and incurs a delay of around 600msec in most people between seeing and understanding, so that’s a maximum update rate of around 1.8Hz Driving by your eyes alone is only possible if no quick action is required. • If the roads and bend radius's are known and learned • And of course as long as no chassis control task’s are required The inner ear…. Processing the yaw and latt acc information from the inner ear is a far simpler process and is therefore faster but even so this feed-back process still suffers a delay of around 300msec so this loop can actually update at around 3.2Hz which is pretty fast. Muscle tension in the drivers body…. The task of moving the steering wheel is a function carried out by the brain stem, the brain stem works automatically to maintain the correct steering angle by varying your arms muscle tension. Changes in the steering resistance cause the brain stem to get confused and flag up the problem to a higher part of the brain that is responsible for processing the overall task of driving the car. This form of feedback is extremely fast at around 100msec so this can provide you feedback at 10Hz (ten times per second). Some interesting points to note: • A driver’s in-head car model is almost exclusively linear • Excessive anxiety in a driver can easily cause the steer torque mechanism to be completely “swamped” by muscle tension and therefore useless. • Inexperienced drivers are frequently unable to interpret inner ear signals or are too confused to act on them so they are discarded by the brains automatic information filters in the brain stem • A surprising level of confusion exists in the inner ear between yaw and chassis roll, this lead some drivers to “dislike” body roll • Many drivers are found to revert back to an entirely visual driving strategy in emergency circumstances • Many drivers are overwhelmed and lose control even though the car was capable of completing the maneuver • A maximum practicable hand steering wheel rate is around 1100 degrees / second –but not for long • Typical hand wheel rates are much slower - < 100 degrees / second in “Sensible” driving. As you can read our abilities are somewhat primitive compared to our manufacturing requests.....

Yep i remember that well..... I should think the Toyota dealers are still blushing about that to this day... To your question... The rear thrust angle is nothing more than the chassis reference point..... without over complicating things the chassis forward direction doesn't know where forward is, so if the rear wheels are centred the "thrust angle" can be used to tell the front wheels where forward is. Example: these front wheels are parallel \ \ or | | or / / .... parallel to what? if you say each other you would be correct assuming the rear wheels follow the same parallel path.

Tyre life has very different objectives nowadays.... Can i ask how well did your tyres perform during the 24k?... The requests at the tyre manufacturer is to keep the modern car with all it's power and suspension technology "on the road"... Tyre preservation has become secondary factor since both requests cannot be answered. An extreme example..... I have an owner of a Ferrari F430 which runs 335/30-19 Michelin Club Sport tyres on the rear. This car went to Germany to have two superchargers fitted/ tested then back to the UK..... It's rear tyres lasted one week/ 1040 miles.