Mixing Tyres

[Notamech]

So recently I noticed that i have mixed tyres on the front. Not sure how i failed to notice this before buying the car but probably due to the tread pattern being similar (both were all season tyres 1 michelin and 1 dunlop) and my brain just assumed they were the same brand as the rear had the same brand both sides. 

Since then everytime i have been to lexus this has been called out as not being ideal. I have since then researched quite a bit on this online but couldn't find anything conclusively proving this is a bad. Just that it is not recommended as it can cause a blowout or can cause some or the other type of damage. None of the articles were clear on the why. I finally went ahead and changed them as i didn't need all season tyres on the front anyway and got some decent GY asymmetric 6s. But the question remains is it really that bad having tyres from 2 different brands on the same axle? When i was none the wiser i drove it in heavy rain in the cold on the motorway and it was absolutely fine. No issues with braking or anything. Is it just because they were good quality branded tyres? Or is there any genuine rationale and i just got lucky? Also not once have i heard any anecdotal stories about someone having issues with different tyres. I have heard stories about people with cheap tyres from china and have had bad experiences myself so am convinced that its worth investing in a known brand. But not yet convinced that having 2 tyres from different good brands on the front can cause issues. What do you guys think? 

[matt8]

I think there's two issues.

The minor: two different tyres can perform slightly differently so may not be balanced in terms of performance. One could have a longer stopping distance than the other.

The major: two different brands will often mean tyres changed at different times, therefore one being older than the other, and almost certainly having a variation in performance.

[Notamech]

1 minute ago, matt8 said:

I think there's two issues.

The minor: two different tyres can perform slightly differently so may not be balanced in terms of performance. One could have a longer stopping distance than the other.

The major: two different brands will often mean tyres changed at different times, therefore one being older than the other, and almost certainly having a variation in performance.

Yes indeed. Infact mine were exactly like that the michelin had plenty of life at 6mm the dunlop was older and had 3.5mm. I sometimes feel like I could have squeezed a year at least out of them and saved some money. But I like pampering my car 😋

[Spock66]

3 hours ago, Notamech said:

When i was none the wiser i drove it in heavy rain in the cold on the motorway and it was absolutely fine. No issues with braking or anything. Is it just because they were good quality branded tyres?

Having mixed tyres will likely reduce the performance envelope of the vehicle, you stayed within the envelope so were ok.  But say you had to make an emergency stop or swerve out of the way of debris on the motorway, then it may have been a different story.

[MattDH]

Yes it's not ideal to have two different brands let alone tread depth. 

AWD cars will especially have problems with different tyres and tread depth/pattern as it can damage the drivetrain  

[Digifant]

it's not even good when you have 4 the same but different in age tyres. But to wear different tyres...... are you sleep well?)))))

[PCM]

For me... the only thing between me and the road are the tyres, so they better be good, the same type, brand, condition and a brand I feel I can trust.

[Notamech]

2 hours ago, Digifant said:

it's not even good when you have 4 the same but different in age tyres. But to wear different tyres...... are you sleep well?)))))

Well I've changed it now. But even when i had different tyres (i ran it for a good 3 months) it made no difference at all. At least for my regular use in the city and on motorways.

Also why is it not good to have tyres of different ages if all 4 are the same? For example i have good years on all 4 wheels now and the 2 fronts are new but the 2 rears are from 2020 but still have ~4.5 mm left on them. I see absolutely no reason why this can be an issue. 

[Notamech]

2 hours ago, PCM said:

For me... the only thing between me and the road are the tyres, so they better be good, the same type, brand, condition and a brand I feel I can trust.

I understand that. And its a valid reason. But was wondering if there is a reason not based on feelings. Like some test results that prove this notion that having 2 odd tyres which are good quality is still a bad idea. 

For example there are tests that conclusively prove that most cheap chinese tyres are not as good as known brands. 

[Las Palmas]

15 minutes ago, Notamech said:

For example there are tests that conclusively prove that most cheap chinese tyres are not as good as known brands. 

It is not often you get more than you paid for.

Some think a tyre is a tyre.

I am one thinking that only the best are good enough.

[Digifant]

15 minutes ago, Notamech said:

Well I've changed it now. But even when i had different tyres (i ran it for a good 3 months) it made no difference at all. At least for my regular use in the city and on motorways.

Also why is it not good to have tyres of different ages if all 4 are the same? For example i have good years on all 4 wheels now and the 2 fronts are new but the 2 rears are from 2020 but still have ~4.5 mm left on them. I see absolutely no reason why this can be an issue. 

Because of the difference in performance. Off course it's a matter of preference and for most of people it's not an issue. But after I had complicated situation on a road because of that, for me it's an issue. And for me, my high brand Dunlops 2019 by now are not tyres anymore, but just piece of black round hard rubber, even with it's 5.5mm. 

[Bluemarlin]

3 hours ago, Notamech said:

Well I've changed it now. But even when i had different tyres (i ran it for a good 3 months) it made no difference at all. At least for my regular use in the city and on motorways.

Also why is it not good to have tyres of different ages if all 4 are the same? For example i have good years on all 4 wheels now and the 2 fronts are new but the 2 rears are from 2020 but still have ~4.5 mm left on them. I see absolutely no reason why this can be an issue. 

Because if they're of different ages then the tyres aren't the same anymore. How different they are will be dependent upon the tread depth of each, but essentially they will clear water at differing rates, potentially causing handling diifficulties.

It matters less if the difference is between front and rear axles, but on the same axle it's best to have the same (or similar) tread depth.

If they are different front to back then it's also advised to have the better/newer tyres on the rear axle, rather than the front.