wheels-inmotion

You say you have a full report, does this include the front camber and castor, if yes what are the final positions?

The reason it should be measured is to ensure the problem is not the castor! As for the question "what is" the castor position, i'm not sure if you want the actual value or an explanation of castor? Ken gave a good example but in essence the castor has many duties, do you want me to explain them?

All new tyres have visible coloured markings forming a radial band on the tyre. Several of these markings represent destination between the manufacture and the recipient.... Cars like Lexus require specific compounds so the radial markings do indeed allow the process to become visible and act like a bar code. But there is also important information held within those lines that most consumers and tyre centres are not aware of, in particular the position of the outer line (colour does vary)..... Depending on how the belts are positioned during construction imperfections will allow the casing and the tyre tread to 'run out'. This disparity allows the compression to steer the tyre laterally regardless of any actions taken by the driver thus generate a pull. The manufacture measures the degree of run out and marks the severity onto the tyre by the position of the outer band, typically the colour is Red or Blue, if the colour band is central then the run out is considered 0, if the band is toward the outer edge the tyre will need a 'reactive' partner to belay any pull. So the positions are vital to you and your car.... Realising this problem then it's easy to conclude if the tyres are symmetrical in tread construction, if the tyres are asymmetrical or directional then the centre will need to find a suitable match with an opposite reactive lateral partner....... Their problem not yours...... So next time you buy tyres have a look for the banding and decide what match you want..... remember most centres will have no idea of your request due to misunderstanding and lack of knowledge so you need to be wise.

Be sure they measure the castor position!!... It's not adjustable on the car but it's a vital part of the overall diagnostics. Since it's not adjustable many centres don't bother to measure it despite the fact it's part of the image you pay for within a geometry.

No.... Front "toe/ alignment/ tracking" is the only angle on a car that's shared. If let's say you hit the kerb and displace the front near side toe by 10mm then as soon as you steer ahead the toe angle will be shared between each wheel 5mm/ 5mm. The reason for this is the fact the toe angle is linked via the steering rack, the only evidence there's a problem would be an off-set steering wheel.

No modification is without consequence, evermore so when you go low.... I recommend the same as the post above, up the pressure and move the toe angle.

Up the tyre pressure by one or two psi and have the toe position moved toward positive.... This will minimize the damage.

If the wear is around 10% of the tyres total width and smooth then the problem is camber, no amount of toe manipulation will help resolve this. A move in the camber to around -45' to -1degree is a sound platform assuming you have adjustment available?

Camber and toe is by using a shim plate.

The camber positions are consistent with the lowering and will generate tyre wear..... Why didn't they correct the toe angles?

At 19mm it's hardly worth the expense of further measurements since this was clearly the problem..... Makes you wonder though, how the hell can they get it 19mm wrong?

Odd one.... Unless the new coil had the wrong rate i:e to low compared to the OSF then it shouldn't pull left, if anything a "new-V-old" would pull right. Can we clarify things * When driving straight the steering position is left hand down * If you relax the steering does the car drift left? * If it's a pull do you have to resist the pull * Did the dealer align the car after the coil install.... this is common practice.

I would go for the full image, that way if there's any camber issues you have the option to deal with that before the tyres wear out.

If the wear is on the outside then reluctantly i say yes to basic laser alignment.

Since the trigger was the tyre fitment then it's wise to assume this is the reason the cars handling badly... Sorry to say sometimes the tyre and the car sometimes just don't work together.

Have you fitted Goodyear Assaymetrics?

I know, oh boy do i know...... Obviously these topics are dependant on the type of car and club but chassis dynamics, suspension dynamics and aerodynamics's apply to all cars with varying attentiveness. I think you will agree most literature is relevant to the 70's, 80's and falls into insignificance by comparison to the modern car. I feel an "overview" in chassis dynamics alone would be impossible today.

An industry wide confusion is the ranges.... we have 1: Checking range 2: Tolerance range 3: Disparity range 4: Dynamic range OEM lowering coils should fall within the checking range but not neccacarily the dynamic range... Oh dear so how do we math this? It's very easy to simulate dynamics static by adding compression (pull down) then lifting (droop) the suspension, allowing the operator to visualise the dynamic tendency's of the suspensions articulation, then adjust accordingly.

You are absolutely correct... The lowering has generated more compression on the tyres inner edge, plus you probably have some toe issues as well. Normally OEM lowering coils allow the Geometric change to fall within the OEM Geometric checking range? if this were the case then there shouldn't be any wear? it might be wise to contact your installer on this topic. If the chassis is adjustable then this should have been dealt with after the coils were installed.... once again the installer needs to address this.

Technical backup helps in these situations, i argue these topics quite successfully for my customers..... thing is it's not up to you to explain why it's wrong now, it's up to them to prove it was right before?

No.... Even marques like Porsche only give a 1000 mile warranty on the chassis Geometry.... There is an argument to be had though?... since they don't give you a chassis report when you buy the car, then how do you know it was correct in the first place!!

Here you go> ........................................ I will summarize the two papers, if you overlap your car and problem we can mediate between the two most likely possibility's. 1: P1:Compression: Tread pattern: The tyre tread in essence is without structure and subject to compression between the road and the constructive casing, the "rolling" influence concludes that the tyre tread will have an "compression" on and "release" off, so in effect "pinch" the rubber, the ratio is higher on the back edge of the tread bar since this will be the initial point that receives the vehicles weight and subject to a higher wear ratio. 1.2: All tyres are subjected to the same force but show different levels of resistance, so an habitual trait between tyre tread pattern can be assumed, study shows. 1: Directional tyres low resistance 2: asymmetrical tyres moderate resistance 3: symmetrical tyres high resistance 1.3: explanation: Taken that the pattern of wear is due to "compression" and "release" then the tyre be it front or rear is also subject to the point of load "camber" this will conclude that the "heel and toe" pattern will not cover the whole tyre width. 2:P2: Suspension:Drive: The relationship between the vehicles parallelograms is through the suspension, on cornering the weight transfer will unload the inner transverse wheels and is subject to "Damper" over coil control, if this relationship is unbalanced then the coil spring will unload and generate a "driver" area pattern of wear, this "pulse" will favour certain areas of the tyre tread since no part of any tyre is symmetrical. 2.2: Study has shown that the "damper" theory is consistent with the countries road lay out, passenger side wear/ drivers side wear, suggesting that the lack of damper control and "heel and toe" is global 2.3: Type of drive: resistance to "heel and toe" has an evident scale over drive. 1: Front wheel drive: under braking has a low resistance on the rear dampers 2: Rear wheel drive ( UK ) has a low resistance on the front inner tyre on a turn 3: 4WD: assuming independent suspension has high resistance due to the uniform thrust. ................................................ There is some technical stuff as well but it's a nose bleed of a read....

That pattern of wear is common on directional tyres, the actual reason for it is open to debate between the car manufacturer and the tyre manufacturer. I wrote a white paper on this topic in an arbitrary position for a conflict over the pond... if anyone is interested i'll post the paper?

The wear is lateral, look at the tread blocks you can see a feathered pattern of wear, camber's unable to do that. If your running stock positions then these need to be changed to suit your driving style/ area.... Point to remember the positions offered by the manufacture are "suggestions" not law.

Very unlikely the camber position is to blame... Is it possible you can display an image of the wear or email it to me [email protected] , i'll be able to tell at a glance what's causing this.