[Dan Bilzerian]

People should have stopped commenting after the first post...

[nozydog]

Originally Posted by BEM-S4

Bad bad bad. You're looking to save what a few hundred and driving a car that costs close to 50k?

I'm the OP and no I don't particularly need to save the money, just don't want to waste money if different tyres on different axles would cause no issues! But I also want my car to handle as well as it possibly can so, not being an expert or an engineer I asked a simple (or apparently not so simple looking at the replies) question. I also was NOT referring to winter tyres as I never drive in snow or ice so do not use them! I will almost certainly replace like for like as recommended by BMW, but in reality I don't believe most drivers necessarily do. They turn up at their local tyre depot on a Saturday morning, want a tyre there and then and go with whatever is recommended. The chances of the exact size and brand for a direct replacement being in stock is fairly slim I'd say, but then most people don't drive top end cars so maybe it's not so much of an issue!

[nozydog]

Originally Posted by Dan Bilzerian

People should have stopped commenting after the first post...

I disagree, isn't this exactly what these threads are for, advice and opinions from other drivers. Call me stupid for even asking the question but looking at some of the replies, I'm glad I did (plus my original question made no reference to winter tyres as I never use them)

[Wires]

Mixing tires does have one benefit. It allows you to confirm your tail-lights are working, since you'll see them in the really cool flat spin that follows.

[HighlandPete]

Originally Posted by nozydog

I disagree, isn't this exactly what these threads are for, advice and opinions from other drivers. Call me stupid for even asking the question but looking at some of the replies, I'm glad I did (plus my original question made no reference to winter tyres as I never use them)

I hold the view there isn't such a thing as a stupid question. Answers... that is a different matter.

Problem with opinion like, "I've changed tires on one axle and it didn't make any difference", we don't have the full context. Not always very scientific. How do we know how the car is driven? Is it ever put near the limits?

I've known folks say how good their car drives, (was in the trade) only to drive the car myself and feel all sorts wrong with it. Individual opinion can be so flawed. Ever seen the car driven along with a tire (or tires) that are nearly flat? Have a word and the driver has no idea! Really?

Advice really needs to be tempered with appropriate testing methods and accepted wisdom. Hence best to heed what the car and tire makers along with related safety organisations recommend.

[nozydog]

Originally Posted by HighlandPete

I hold the view there isn't such a thing as a stupid question. Answers... that is a different matter.

Problem with opinion like, "I've changed tires on one axle and it didn't make any difference", we don't have the full context. Not always very scientific. How do we know how the car is driven? Is it ever put near the limits?

I've known folks say how good their car drives, (was in the trade) only to drive the car myself and feel all sorts wrong with it. Individual opinion can be so flawed. Ever seen the car driven along with a tire (or tires) that are nearly flat? Have a word and the driver has no idea! Really?

Advice really needs to be tempered with appropriate testing methods and accepted wisdom. Hence best to heed what the car and tire makers along with related safety organisations recommend.

Very good advice. What I observe from this thread is that it's clear the term 'mixing tyres' means different things to different people! I would NEVER even consider mixing a different 'type' of tyres (e.g. Winter & summer) but different brands of the same tyre type is a different thing altogether and I've never heard 'experts' say you shouldn't do that! A fair few have said it here, but how many of them are experts!? I always put identical tyres on the same axle but have (in the past, not since I've driven high end cars) used different brands on different axles! Do 'experts' actually consider the mixing of tyre brands to be mixing tyres? I'm not convinced they do!

In fact BMW state that my car comes with 'mixed' performance tyres!!! This clearly refers to the fact that the rear tyres are a different size to the front tyres!

[HighlandPete]

Originally Posted by nozydog

Very good advice. What I observe from this thread is that it's clear the term 'mixing tyres' means different things to different people! I would NEVER even consider mixing a different 'type' of tyres (e.g. Winter & summer) but different brands of the same tyre type is a different thing altogether and I've never heard 'experts' say you shouldn't do that! A fair few have said it here, but how many of them are experts!? I always put identical tyres on the same axle but have (in the past, not since I've driven high end cars) used different brands on different axles! Do 'experts' actually consider the mixing of tyre brands to be mixing tyres? I'm not convinced they do!

In fact BMW state that my car comes with 'mixed' performance tyres!!! This clearly refers to the fact that the rear tyres are a different size to the front tyres!

You'll find, if you look at the technical data for virtually all tyre manufactures and car makers, that the recommendation is fit four tyres of the same type and specification. Fitting tyres with the same tread pattern is also set out in most tyre data.

The "mixed performance tyres" statement is not intended to mean mixing different tyre brands. Simply the wheel set up for a particular vehicle, 'staggered' or 'square' as we call it. Doesn't mean a vehicle can't have either option, but characteristics change with say the staggered 'mixed' set. Deliberately so, builds in more understeer for the sport setups. If you have driven the same chassis on the different wheel set types, you'll know how a 'square' setup is a more neutral balance, (better in many cases) and requires more skill to control as you reach the limits. The staggered setup allows more 'give' in car control.

But that is different to mixing tyres. There are specific guidelines and recommendations from the tyre manufacturers and organisations like TyreSafe, BTMA (British Tyre Manufacturers’ Association). For example, on using and mixing run-flats.

Typical BTMA statement:

Mixing SSTs with standard tyres

The handling and performance characteristics of SSTs are different to those of standard radial tyres, and so they should not be intermixed on a vehicle, i.e. all four tyres should be similar in structure.

Mixing of different brands of SSTs

As with standard tyres, different brands of SSTs may have different characteristics. It is therefore advisable to consult the tyre manufacturer regarding mixing of different makes of SSTs. It is recommended that the same make and type of SST tyre is fitted across the axle. In most European countries it is not allowed to mix different brands or structures of tyres on the same axle.

An example from Continental:

An SSR/standard tyre mix should not be fitted on a vehicle – not even axlewise. (In isolated cases a standard tyre can be temporarily mounted on a vehicle otherwise equipped with SSR tyres. It must be pointed out to the driver, however, that the standard tyre has no runflat properties.)

The general sort of comment on mixing tyres, this from Semperit:

Mixing tyres should be avoided

Tyre size, Load Index (LI) and Speed Index (SI) at all wheel positions should be in accordance with the vehicle manufacturer’s specification. In many countries, this is a legal requirement. Driving with a non recommended
mix of tyre sizes, designs and Speed Indices can be dangerous. In the event that tyres of different sizes, designs, Load or Speed Index are to be fitted
on a vehicle, the vehicle manufacturer’s recommendations should be heeded and/or the advice of a qualified tyre specialist sought.

Some vehicles leave the factory with different tyre sizes on the front and rear
axles. This configuration must not be changed unless approved by the vehicle manufacturer.

[BEM-S4]

Originally Posted by nozydog

I'm the OP and no I don't particularly need to save the money, just don't want to waste money if different tyres on different axles would cause no issues! But I also want my car to handle as well as it possibly can so, not being an expert or an engineer I asked a simple (or apparently not so simple looking at the replies) question. I also was NOT referring to winter tyres as I never drive in snow or ice so do not use them! I will almost certainly replace like for like as recommended by BMW, but in reality I don't believe most drivers necessarily do. They turn up at their local tyre depot on a Saturday morning, want a tyre there and then and go with whatever is recommended. The chances of the exact size and brand for a direct replacement being in stock is fairly slim I'd say, but then most people don't drive top end cars so maybe it's not so much of an issue!

Most drivers don't spend their time reading forums and learning about their cars either. You don't need exactly OEM tires but you definitely need all 4 to match.

For instance I ditched my 18" wheels w PSS tires in favor of 17" w DWS06 knowing what compromises and advantages I was gaining.

[Wires]

I don't think it was a bad question to ask either. The real issue is not many people in the world actually know what makes up a tire. You just assume it's black, it's rubber, and it's round. Comes in different brands and sizes.

The real deal is there is hardly any rubber in it. It's a hybrid of materials and compounds, and is quite frankly, a marvel of the modern world.

Here is great example if you run Michelin Pilot Sports. When you look at the tread, there is a center rib that has no siping (slits in the tire that allow it to contour to unstable road conditions). That rib is made from a compound that repels water so that the tire will have a solid contact patch in wet weather.

The inner 1/2 of the tread (closest to the car) is made from materials that deal with everyday driving (rain, rocks, etc). The outer 1/2 of the tire have different compounds that allow it give high traction during cornering (since the car will lean and the weight is transferred to the outer 1/2 of the tire).

For winter tires, the compounds are designed to stay softer at cold temperatures, and have a lot of blocky patterns to eject snow from the tread. You'll find that they have a lot of siping (slits) as well that works like little fingers trying to grab whatever it can on ice for traction. Try taking summer sport tires out on 1/4" of melting slush, or a gravel road if you really want to respect life!

Since the tires aren't just black circles of rubber, and every manufacturer ahs their own secret recipe of compounds and designs, you have no idea how they will react differently. If you miss-match brands/styles, you can run into a situation where the fronts have amazing grip during a corner, whereas the rears drift more. In this situation, the rear of the car will spin out, causing an unpredictable and dangerous situation.

[nozydog]

Thank you all... I will NEVER mix tyres!!

[BEM-S4]

Originally Posted by nozydog

Thank you all... I will NEVER mix tyres!!

One exception. Say you have summer wheels / tires and a winter set. If you get a flat you can throw one of the other set on to use as a spare in a pinch until you get the other tire fixed. I wouldn't drive too much like that but for a short trip to the tire shop or whatever you'd be fine.

[cmplaya]

i'm not sure if this is a serious post or not....

Originally Posted by Polo08816

I think you bring up a very valid point. Sometimes there's great benefit to mixing tires.

For example, my mechanic once told me that all-seasons are really no-seasons. He recommended that I have one summer tire and one winter tire on each axle and to alternate the sides for summer/winter tires. For example:

Front left - summer
Front right - winter
Back left - winter
Back right - summer

OR

Front left - winter
Front right - summer
Back left - summer
Back right - winter

It was explained to me that if you arrange your tires in this fashion, you would always have some traction on either axle/side no matter the season.

[CalCarNut]

2+2 handled as expected..which ever end is going to washout on maneuvers....

NEVER skimp on tires. Period. Your only road contact are those 4 patches of rubber, no matter if you have ceramic, Carbon metallic etc pads. I prefer the ability of short stopping distances and handling/emergency maneuver capabilities for a couple of years over a c-note or 2 in my wallet.

[Wires]

Originally Posted by CalCarNut

2+2 handled as expected..which ever end is going to washout on maneuvers....

NEVER skimp on tires. Period. Your only road contact are those 4 patches of rubber, no matter if you have ceramic, Carbon metallic etc pads. I prefer the ability of short stopping distances and handling/emergency maneuver capabilities for a couple of years over a c-note or 2 in my wallet.

Great advice. If you want a real reality check, jack you car up, wet the tires, set it back down and see how small the spot of tire contact is.

And then think about 4 of those little hand prints when pulling 1-G on a cloverleaf!