Replacing 2 tyres only? - FYI

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Originally Posted by Kiz_EG6

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!!!

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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!

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.

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Originally Posted by 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.

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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!

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.

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Originally Posted by 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.

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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.

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?

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Originally Posted by 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?

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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.

should of gotten adrenalins gab!!!