Replacing 2 tyres only? - FYI

[rahul]

Hi all,

came across this. When replacing two tyes, Michelin recommends having the new tyres on the rear.

aplolgies if this has been posted before

Click on the last link and there's a video as well.

http://www.michelinman.com/tire-care/tire-saving-tips/replacement-questions/#install-tires

[spacepants_fb]

Dude, didn't even know that! Good find...does it apply for both fwd and rwd?

[beeza]

It makes sense...

[destrukshn]

lol, yeah, but what if you understeeer?

[beeza]

Hehe exactly,hello tree...
Need to replace all 4 :)

[VL_Commy]

that applies to RWD cars. FWD should always do the front.

[rahul]

that applies to RWD cars. FWD should always do the front.

that's what i thought.. the video is a bit ambigious whether it applies to FWD or RWD. It shows a cd5 at the start, then a 3 series and not sure if the test cars are FWD or RWD.

[JohnL]

They're assuming more grip from the new tyres, and recommending fitting the new tyres to the rear so as to avoid any tendency toward increased oversteer. This is the case for front or rear wheel drive, or four wheel drive for that matter.

It's assumed by car and tyre manufacturers that the average driver is likely to die in the event of oversteer because oversteer typically requires a higher level of skill to deal with appropriately than understeer. This is why car manufacturers go to great pains to ensure that 99% of their products are strong understeerers. The tyre manufacturer will give this advice with a driver of average skill (or lack therof) in mind, for the same reasons as the car manufacturers design their cars to understeer.

If you would prefer less understeer and are realistic about your skill levels then you could fit the new tyres to the front, keeping in mind that if you have an accident due to oversteer then it's your fault. While (all else being equal) the new tyres will tend to give more grip and more grip in the front if fitted on the front, they will tend to have less steering response, at least until the tread blocks have worn down to some degree.

When I was lot younger and used to drive way too fast, I had a flat rear tyre which I then replaced with the (new) spare. I then proceeded to continue my too fast fang along my favourite 'track', until I came to a very fast corner that I took as fast as I usually did, resulting in a very scary rear end slide that saw the car at a big angle to direction of travel for a very long distance. I was so lucky that I didn't spin it or hit any of the cars parked on the road side (I'd like to think skillful, but lucky is more accurate!). The cause? Apart form stupidity, it was the mould release agent on the new rubber. Brand new (like really new) tyres have very poor grip until this is scrubbed off.

[jdm_kid]

which cheapo would buy 2 tyres lol unless its semi slicks haha

[beeza]

I did.I skided too hard a few times on the front.Wore flat patches on my Nankangs.

[JohnL]

which cheapo would buy 2 tyres lol unless its semi slicks haha
Lots of people, many much less cheap than I am!

Front tyres wear about twice as fast as rears, I'm not throwing perfectly usable rubber away, are you mad?!

Anyway, what difference does it make if the tyres are semi slicks? If the tyres are for racing purposes (or even merely 'high performance' road use) you could make an argument that only replacing two semi slicks is sillier than replacing only two more ordinary road tyres.

Keeping in mind that racing rubber deteriorates significantly with every heat cycle the tyre is subjected to; Say you start off with a set of 4 new semi slicks and then wear the fronts out racing (or just hooning around like a maniac). You then buy only two new for the front, so now have new front tyres with good grip, but two old rear tyres that have seen quite a few heat cycles and are therefore not as soft and sticky as they once were.

You now have a mismatched set of tyres with poorer performing tyres on the rear. I'll bet the handling and grip balance is now worse than with the original 4 new tyres, and that lap times go up, unless that is the basic set up is unbalanced with too much understeer, but now more balanced with crap rear tyres.

[panda[cRx]]

all mechanics and tyre specialist i know put them to the front. they do all your steering and your fronts cover most of the braking (and for fwd all of the acceleration too)

[Limbo]

I agree with you panda. I've always been told the front also cos you need to steer (even in a rear wheel) and brake from the front more.

[Kiz_EG6]

MICHELIN: When new tires are installed on the rear, it helps reduce the potential for your vehicle to fishtail or hydroplane in wet conditions.


Wikipedia: Hydroplaning or aquaplaning by a road vehicle occurs when a layer of water builds between the rubber tires of the vehicle and the road surface, leading to the loss of traction and thus preventing the vehicle from responding to control inputs such as steering, braking or accelerating. It becomes, in effect, an unpowered and unsteered sled.

So the three main dangers of hydroplaning are:
1: Poor acceleration
2: Poor breakng
3: Understeering

1. We know that a FWD drives with the front wheels, so in this case the drive wheels should have the new tyres, also, if a RWD has trouble taking off in the wet, then those tyres need to be replaced, not just dumped on the back!

2.Considering that a car's breaking system is front bias, whether FWD, RWD or AWD, it would be safer to have the new tyres on the front in wet conditions, to help stop quicker!

3. All, ALL cars steer with their front wheels other than maybe some pakistani car i've maybe never heard of (or preludes at low speed :p) so there is no defence there, they will all understeer as easily in the wet as each other!

I think michellin need to do some research and specify FWD, RWD a little clearer and maybe offer a different point of view, i would never have inferior tyres on the front of my car!

[Kiz_EG6]

One solution to the problem of replacing only two tires at a time is to prevent premature wear to the tires in the first place by a proper rotation schdule of your tires so they all wear the same.;)

Beeeengooo... totally agree!!
It's not that hard to jack ur car up every 5-10 000 k's and swap front and rear!
Gets a bit harder if you only have one drive wheel and directional tyres though :)

[JohnL]

Beeeengooo... totally agree!!
It's not that hard to jack ur car up every 5-10 000 k's and swap front and rear!
Gets a bit harder if you only have one drive wheel and directional tyres though :)

One drive wheel? Get your differential fixed!

An argument can be made that rotating tyres actually increases overall tyre wear. It goes like this; As a new tyre wears when fitted to a particular corner of the car, it wears according to the particular characteristics of the suspension on that corner. This includes static camber angle and the degree to which that suspenion gains camber with suspension defelection. When new the tyre's tread will not match the characteristics of the wear that will occur on the suspension to which it's fitted, it will have areas where the contact patch loading is more heavily loaded and areas where less heavily loaded (typically more loaded on the inner part of the contact patch due to neg camber).

The new tyre will be 'flat' across the tread, but is likely to wear more on one side of the tread than the other according to static and dynamic camber angles seen in service. When new the contact patch will be more heavily loaded on one side than the other, and will tend to wear more on the more heavily loaded side.

As it wears in to the suspension this difference in loading in different areas of the contact patch will even out as rubber wears away until the loading is more equal across the contact patch, but the tyre will go through an initial period of 'accelerated' wear until this state is acheived.

If we now move that 'worn in' tyre to a different corner with a different suspension characteristic it will go through another period of 'wearing in' where the wear rate in some part of the tread will be faster than it will be once the tyre has worn in to the characteristics of the 'new' suspension.

So, when we rotate tyres we may spread the totality of wear more evenly over all of the four tyres, but each individual tyre will tend to wear more quickly. This may not be a big difference, but in principle it exists.

[Kiz_EG6]

One drive wheel? Get your differential fixed!

An argument can be made that rotating tyres actually increases overall tyre wear. It goes like this; As a new tyre wears when fitted to a particular corner of the car, it wears according to the particular characteristics of the suspension on that corner. This includes static camber angle and the degree to which that suspenion gains camber with suspension defelection. When new the tyre's tread will not match the characteristics of the wear that will occur on the suspension to which it's fitted, it will have areas where the contact patch loading is more heavily loaded and areas where less heavily loaded (typically more loaded on the inner part of the contact patch due to neg camber).

The new tyre will be 'flat' across the tread, but is likely to wear more on one side of the tread than the other according to static and dynamic camber angles seen in service. When new the contact patch will be more heavily loaded on one side than the other, and will tend to wear more on the more heavily loaded side.

As it wears in to the suspension this difference in loading in different areas of the contact patch will even out as rubber wears away until the loading is more equal across the contact patch, but the tyre will go through an initial period of 'accelerated' wear until this state is acheived.

If we now move that 'worn in' tyre to a different corner with a different suspension characteristic it will go through another period of 'wearing in' where the wear rate in some part of the tread will be faster than it will be once the tyre has worn in to the characteristics of the 'new' suspension.

So, when we rotate tyres we may spread the totality of wear more evenly over all of the four tyres, but each individual tyre will tend to wear more quickly. This may not be a big difference, but in principle it exists.

A non LSD FWD or RWD (unless you are a grandma driver) will always wear out the drive wheel quicker than the other, whereas, an LSD equipped vehicle wears far more evenly!! Burnouts cause this problem even worse!!

I understand what you are saying about the camber wear, but if you have a correct suspension/camber setup and correct PSI in ur tyres for your driving style, then the camber wear should not generally be noticeable (I had 1.5 degree to the negative on the back of my EG and 1.75 to the negative on the front, and the tyre wear was even across the tread) so though this is a factor, i would be more concerned with uneven wear front:rear.

[mrwillz]

i would of istantly put new tyres in the front
logicially

[JohnL]

A non LSD FWD or RWD (unless you are a grandma driver) will always wear out the drive wheel quicker than the other, whereas, an LSD equipped vehicle wears far more evenly!! Burnouts cause this problem even worse!!

I've outgrown doing burnouts! Having said that, when on the rare occasion I unintentionally do one, or succumb to temptation and sneakily do one (just a small one, not great clouds of smoke!), both front wheels tend to spin more or less equally, so long as I'm not attempting to steer at the same time. This is more or less typical for front drivers (even with open differentials) because the torque reactions are longitudinal not lateral. So, respectfully I have to disagree.

For a typical front engined rear driver with a live rear axle; if the engine rotates clockwise as viewed from the front (typical), then the engine's torque attempts to lift the chassis on the left side and lower it on the right (i.e the engine torque attempts to rotate the whole chassis around the crank axis in the opposite direction to crank rotation), but at the differential the crown wheel will try to 'climb' the pinion and lift the right side of the axle in the same direction to drive shaft rotation (same as crank rotation).

This is why you so often see rear drivers 'light up' the right rear. The right rear spring loads up and the left rear spring unloads, but, the right rear wheel gets light, left wheel gets heavy and the right wheel spins easily. This is a function of engine torque, and it overcomes any weight induced loadings, i.e. force (from torque) is transferred laterally along the axle housing from one side to the other, so even though the right rear spring becomes a bit more compressed and the left rear a bit more uncompressed, the right rear contact patch lightens and the left rear patch loads up.

A rear driver with an independant rear end is different; there is no lateral torque reaction at the rear wheels that is is independant of torque reaction into the chassis. There is a torque reaction into the chassis that lifts the chassis on the left side and lowers it on the right as above, and this loads up the right rear spring while unloading the left rear spring, but because the differential is solidly attached to the chassis and not the suspension this results in the left rear becoming lighter and being more likely to lose traction than the right rear.

This effect is not nearly as strong as the opposite effect with a live rear axle. A live rear axle suffers a lot more from torque reaction and lightening of one drive wheel than an independant rear, at least one of the several reasons why independant rear suspension is superior to a live axle.

On the other hand, a front driver reacts torque equally in a lateral orientation, while reacting it differently longitudinally, so each front wheel remains equally loaded. The longitudinal torque reaction will attempt to rotate the chassis backward (like a bike doing a wheelie), lightening the front wheels and loading up the rear wheels, which is unfortunate but there is nothing we can do about it, physics is physics! This problem is greater the more front traction we have, the more torque to the front wheels, and the shorter the wheelbase.

Note that this effect is not the same as weight transfer from front to rear caused by acceleration (mass, inertia, 'pitch centre' height relative to CG height), it is divorced from this source of weight transfer, being purely to do with the reaction of torque forces. If we hypothetically could lower the CG to ground level (I wish!), we would have zero weight transfer from acceleration, but we would still have some weight transfer from the torque reaction.

With front drive, any difference in side to side loading (and thus any tendency to spin one wheel before the other) will reflect static weight distribution and any irregularities in ground level, but the tendency to spin one wheel will be way less than with a live rear axle on a rear drive car, and somewhat less than with a rear driver with independant rear suspension.


I understand what you are saying about the camber wear, but if you have a correct suspension/camber setup and correct PSI in ur tyres for your driving style, then the camber wear should not generally be noticeable (I had 1.5 degree to the negative on the back of my EG and 1.75 to the negative on the front, and the tyre wear was even across the tread) so though this is a factor, i would be more concerned with uneven wear front:rear.

The more equal the front / rear static camber, and the more similar the camber curves of the front and rear suspensions (camber curve being the camber changes with bump and rebound), the more similar the front and rear tyre wear will be (in nature if not degree), so tyre rotation will have little affect on overall tyre wear. On a Honda (or similar) with double wishbones front and rear, and if the static camber is close to the same front / rear (as your's is) the more similar the tyre wear will be.

On the other hand, if you have say Mac stuts up front (which have a very poor camber curve, gaining a lot of pos camber with roll) with substantial static neg camber, and say a live rear axle or a 'dead' beam axle (which both have camber curves at zero camber gain, meaning no camber is gained with body roll) with zero static camber, then the tyre wear will be very different front to rear, and tyre rotation may have quite a substantial affect on overall tyre wear.

There's not much we can do to equalise front / rear tyre wear short of rotation (at the possible expense of increased overall wear). It is of course a function of weight distribution, and the fact that we are using the fronts to propel the car as well as steer it (a lot of work to do!). About the only thing we can do within the parameters at our disposal is to reduce understeer, because understeer wears front tyres. Unfortunately, I doubt this will make much difference, even if it makes some.

[JohnL]

i would of istantly put new tyres in the front
logicially

So would I. All I was saying is that the tyre companies recommendation will be for the purpose of reducing the possibilty of oversteer in extremis. If the rear tyres are quite worn then they will most probably also be somewhat hardened by oxygen, heat and sunlight, and be less grippy than the softer new rubber as a result.

If you put the new tyres on the front you will lessen the possibility of understeering in the wet, but you will also increase the possibilty of oversteering, in the wet or the dry. An average driver will have a much better chance of dealing with understeer than with oversteer. Lifting off is the instinctive reaction to the handling going pear shaped, and this is generally the correct thing to do with understeer, but generally the wrong thing with oversteer. Locking up the front brakes is of course a different story, the average driver will just push harder, probably removing themselves from the gene pool. The tyre company's recommendation can't cover every eventuality.

Another thing occurs to me; asuming the driver doesn't cope with understeer there is a 50/50 chance of going either into the ditch or into oncoming traffic (I know where I'd rather go if I had to make the choice!). If the driver doesn't cope with oversteer then he / she may go into the ditch, or into oncoming traffic, but there's probably more than a 50/50 chance that at least some part of the car will cross over the centre line, either directly onto the wrong side of the road (far side) or on the way to the ditch on the near side. The average driver, on average, is probably better off with understeer than oversteer, so probably better off with the newer tyres on the rear (IMNSHO).

[rahul]

i think JohnL put it summed it up well by saying it's aimed at the average driver who is better capable of controlling understeer than oversteer.

i'm sure Michelin knows what they're talking about and most of their customer base is the average Joe rather than buyers from this forum and others alike. Hence that advise is aimed at the average driver to have the new tyres on the rears.

[JohnL]

It's not so much the average driver's 'capability' to better control understeer better than oversteer. I don't think 'skill' comes into it all with an average driver. It's just that the untrained reaction is to lift off if the driver gets a fright, which will get them into less trouble (or less worse trouble, if you'll excuse the appalling sentence structure!) if the car is understeering rather than oversteering. On the other hand they may completely panic and slam on the brakes which is less than good on a slippery road...oh well!

[preludacris]

Beeeengooo... totally agree!!
It's not that hard to jack ur car up every 5-10 000 k's and swap front and rear!
Gets a bit harder if you only have one drive wheel and directional tyres though :)

it is if you have rays nuts, and don't wanna scratch them!!! Lol..

such a pain to take of my wheels these days.

[Kiz_EG6]

I've outgrown doing burnouts! Having said that, when on the rare occasion I unintentionally do one, or succumb to temptation and sneakily do one (just a small one, not great clouds of smoke!), both front wheels tend to spin more or less equally, so long as I'm not attempting to steer at the same time. This is more or less typical for front drivers (even with open differentials) because the torque reactions are longitudinal not lateral. So, respectfully I have to disagree.

For a typical front engined rear driver with a live rear axle; if the engine rotates clockwise as viewed from the front (typical), then the engine's torque attempts to lift the chassis on the left side and lower it on the right (i.e the engine torque attempts to rotate the whole chassis around the crank axis in the opposite direction to crank rotation), but at the differential the crown wheel will try to 'climb' the pinion and lift the right side of the axle in the same direction to drive shaft rotation (same as crank rotation).

This is why you so often see rear drivers 'light up' the right rear. The right rear spring loads up and the left rear spring unloads, but, the right rear wheel gets light, left wheel gets heavy and the right wheel spins easily. This is a function of engine torque, and it overcomes any weight induced loadings, i.e. force (from torque) is transferred laterally along the axle housing from one side to the other, so even though the right rear spring becomes a bit more compressed and the left rear a bit more uncompressed, the right rear contact patch lightens and the left rear patch loads up.

A rear driver with an independant rear end is different; there is no lateral torque reaction at the rear wheels that is is independant of torque reaction into the chassis. There is a torque reaction into the chassis that lifts the chassis on the left side and lowers it on the right as above, and this loads up the right rear spring while unloading the left rear spring, but because the differential is solidly attached to the chassis and not the suspension this results in the left rear becoming lighter and being more likely to lose traction than the right rear.

This effect is not nearly as strong as the opposite effect with a live rear axle. A live rear axle suffers a lot more from torque reaction and lightening of one drive wheel than an independant rear, at least one of the several reasons why independant rear suspension is superior to a live axle.

On the other hand, a front driver reacts torque equally in a lateral orientation, while reacting it differently longitudinally, so each front wheel remains equally loaded. The longitudinal torque reaction will attempt to rotate the chassis backward (like a bike doing a wheelie), lightening the front wheels and loading up the rear wheels, which is unfortunate but there is nothing we can do about it, physics is physics! This problem is greater the more front traction we have, the more torque to the front wheels, and the shorter the wheelbase.

Note that this effect is not the same as weight transfer from front to rear caused by acceleration (mass, inertia, 'pitch centre' height relative to CG height), it is divorced from this source of weight transfer, being purely to do with the reaction of torque forces. If we hypothetically could lower the CG to ground level (I wish!), we would have zero weight transfer from acceleration, but we would still have some weight transfer from the torque reaction.

With front drive, any difference in side to side loading (and thus any tendency to spin one wheel before the other) will reflect static weight distribution and any irregularities in ground level, but the tendency to spin one wheel will be way less than with a live rear axle on a rear drive car, and somewhat less than with a rear driver with independant rear suspension.



The more equal the front / rear static camber, and the more similar the camber curves of the front and rear suspensions (camber curve being the camber changes with bump and rebound), the more similar the front and rear tyre wear will be (in nature if not degree), so tyre rotation will have little affect on overall tyre wear. On a Honda (or similar) with double wishbones front and rear, and if the static camber is close to the same front / rear (as your's is) the more similar the tyre wear will be.

On the other hand, if you have say Mac stuts up front (which have a very poor camber curve, gaining a lot of pos camber with roll) with substantial static neg camber, and say a live rear axle or a 'dead' beam axle (which both have camber curves at zero camber gain, meaning no camber is gained with body roll) with zero static camber, then the tyre wear will be very different front to rear, and tyre rotation may have quite a substantial affect on overall tyre wear.

There's not much we can do to equalise front / rear tyre wear short of rotation (at the possible expense of increased overall wear). It is of course a function of weight distribution, and the fact that we are using the fronts to propel the car as well as steer it (a lot of work to do!). About the only thing we can do within the parameters at our disposal is to reduce understeer, because understeer wears front tyres. Unfortunately, I doubt this will make much difference, even if it makes some.


Dude do you just cut and paste this shit off some gay ass technical site?!?
You know no one is impressed that you can take two pages to write what only needed two sentences, i can't even be bothered reaqding it!!!

[JohnL]

Dude do you just cut and paste this shit off some gay ass technical site?!?
You know no one is impressed that you can take two pages to write what only needed two sentences, i can't even be bothered reaqding it!!!

No, I didn't cut and paste anything from any site. Everything I write is from my own background knowledge and understanding. I've been interested in chassis dynamics for many years, and have read extensively on the subject as well as having discussed such things with proffesional suspension enginneers and designers. My main technical interest in racing karts, but the physics that apply to cars and karts are the same, just applied in different ways. In order to better understand kart dynamics its very helpful to study car dynamics, though car dynamics are just as interesting in their own right.

I may make long posts, but in reality I'm only briefly explaining some complex dynamics (only just skimming the surface on some of it really), but it could easily take a fair bit more explanation to more fully explore, and definitely not less, that is unless you don't actually want to understand the fundamentals of what might be going on. Choose ignorance if you like.

Some people may actually find some of my writing of interest (maybe!), and might actually gain something from it if they take it on board. It's perfectly OK if you don't, you don't have to read it I'm not forcing you to. If you disagree with me then fine, argue your case or just don't bother.

You seem to be peeved that I politely pointed out (in some detail) a very basic error in your understanding of traction as it relates to front wheel drive cars, and responded in an extermely childish manner. You don't enhance your credibility by being rude and abusive, but since you decided to lower the standard I'll ask; If you can't be bothered reading it then how the hell do you know that what I said could be explained in two sentences? If you're too lazy or not intelligent enough to understand it then that's not my problem!

[string]

Don't worry JohnL, i've experienced the same thing. Ignore those that critisize your answers. They are idiots who can't think for themselves and need simplified short answers to satisfy their simple needs. Some people enjoy technical posts - unfortunately on this forum, they are in the supreme minority.

New tyres to the front. My reasoning is as follows.

The majority of incidents and surprises that occur to a non-idiot(tm) driver are things out of their control. It's someone slamming on the brakes in front of you, someone cutting you off - who knows. From my own experience, most of these things require hard braking. I want to have my tyres setup for maximum braking and front grip. Most incidents where oversteer could occur from miss-matched front rear tyre grip, are in situations I could conciously avoid (i.e. going around sweepers fast in the rain). Driving quickly in the rain is a disaster waiting to happen, anyone who causes an over-steer situation should seriously reconsider their abilities behind hte wheel.

For the average idiot with no concept of load transfer, it really doesn't matter where your tyres go because it's a game of luck what your next accident is going to be caused by.

[JohnL]

Don't worry JohnL, i've experienced the same thing. Ignore those that critisize your answers. They are idiots who can't think for themselves and need simplified short answers to satisfy their simple needs. Some people enjoy technical posts - unfortunately on this forum, they are in the supreme minority.

Do I look worried?!

There does seem to be a bit of anti-intellectualism on this forum, unfortunately it's not the only one. What is mildly annoying is when you point out (politely) somebody's fundamental misconception about whatever, rather than being mildly thankful (not that I really need or want thanks) for improving their understanding they get aggressive and attack you. Too much ego / too little intellect / too bloody common!

[teh_mechanic]

nice post johnL.Interesting read.Good to get your head around some theory like that sometimes,but I agree with string as to putting the new tyres to the front for braking reasons,just dont push the car hard until you can afford good tyres all round,simple,and until then,braking is where the grip needs to be and we all know that with weight transfer the majority of braking grip needs to be at the front.

[JohnL]

nice post johnL.Interesting read.Good to get your head around some theory like that sometimes,but I agree with string as to putting the new tyres to the front for braking reasons,just dont push the car hard until you can afford good tyres all round,simple,and until then,braking is where the grip needs to be and we all know that with weight transfer the majority of braking grip needs to be at the front.

Thanks, glad a few people find my stuff worth reading.

Personally I would rather put the new tyres on the front all else being equal. I was just trying to explain why a tyre company might recommend the opposite. A credible argument can be made either way. Less grippy tyres on the rear will tend to allow rear wheel lock up more easily and this can get punters into a lot of trouble as the car tries to swap ends.

At the moment I have newer tyres on the rear of my CB7, but this is because the front tyres are a different brand and work better on the front than the newer ones on the rear do. In this instance all else isn't equal.

[FallenAngel]

Good stuff there John, quite liked reading it and insightful also.

Well regarding the 2 tyres only, my left rear tire has worn to the thread without me knowing until abs kept kicking in then i checked it. My alignment was totally off... Camber of the left rear was significantly off in such a way u can actually see it from under behind the car. My right rear has worn out to just 1mm from the indicator and my parents (they bought the car for me) told me to go back to honda to get them to replace them (its been about 2 weeks since service) and i kinda knew that this wasn't a good idea since my car has been lowered with the added mugen kit and manufacturers don't like this.

Anyways off to the dealer this morning and had a long discussion about it for about an hr. The main point that they said was that i altered my suspension therefore honda isn't obliged to pay for it. It came to an end and i had to buy new tires off them. They told me to buy new tires for the front and use the existing fronts for the rears. Then i remembered about this post.

So is it best that i change only two or may as well change all four since the front two are on its way?

[JohnL]

Good stuff there John, quite liked reading it and insightful also.

Well regarding the 2 tyres only, my left rear tire has worn to the thread without me knowing until abs kept kicking in then i checked it. My alignment was totally off... Camber of the left rear was significantly off in such a way u can actually see it from under behind the car. My right rear has worn out to just 1mm from the indicator and my parents (they bought the car for me) told me to go back to honda to get them to replace them (its been about 2 weeks since service) and i kinda knew that this wasn't a good idea since my car has been lowered with the added mugen kit and manufacturers don't like this.

Anyways off to the dealer this morning and had a long discussion about it for about an hr. The main point that they said was that i altered my suspension therefore honda isn't obliged to pay for it. It came to an end and i had to buy new tires off them. They told me to buy new tires for the front and use the existing fronts for the rears. Then i remembered about this post.

So is it best that i change only two or may as well change all four since the front two are on its way?
Ideally the car should have reasonably equal wear on all four tyres, but if you have two tyres with decent tread left on them there's no real need to replace all four, unless money isn't an issue for you. What is important is that each pair of tyres on each axle line should match quite closely in the amount and type (pattern) of wear.

If the spare is new or near new, then you can fit that as one of the new tyres meaning you only have to buy one new tyre in order to have two 'new' on the same axle line, then use the best of the two you are replacing as the spare, so long as it has legal tread.

Whatever you do it does sound like you probably need a wheel alignment and the suspension checked out. Camber will increase wear, but not by much on it's own (unless fairly dramatic camber angles). Toe is the biggest contributor to tyre wear, and you shouldn't have more than a few mm (say 3mm at most) at each axle line. I align my toe to zero front and rear. If you combine excessive toe with excessive camber then your car will just eat tyres.

[dc2vtir]

should of gotten adrenalins gab!!!