Mixing Tyres (and why you really shouldn't!)

[Ekona]

There's a lot of conflicting threads and posts on here with regards to the subject of tyres and in particular mixing them on the car, so I've been asked to write this which should hopefully clear a few things up as well as giving you something to think about and make your own mind up on.

 

 

I'll start with the very obvious: Tyres are the only thing keeping the car in contact with the road. As daft as it sounds it's always worth remembering, as whether you're chasing tenths of seconds on track or munching motorway miles you will always want tyres that give you full confidence that they are doing their job properly at all times and in all conditions. That's the really the key point I'm getting at through the whole of this post, confidence in your car and tyres. If you take nothing else away from this, just remember that stability will lead to confidence and you won't go far wrong.

 

 

I'll start with an oft-used example of tyres here, the RE040 (left pic) and RE050 (right pic). These are OEM fitment on the DE and HR engined cars respectively, and the latter on the 370Z as well.

 

 

 

They seem pretty similar at first glance: Five main bands over the tyre, slots all pointing the same way where appropriate, both made by Bridgestone and only one number apart... Now look closer. See the centre band? On the 40 it's split with a line down the centre, on the 50 it has no line and the cuts into it are much more pronounced. The next two bands out are completely different, look at the angle and sweep of the cuts. Finally look at the out bands, and see just how different the cuts in there are.

 

Two tyres, both by the same manufacturer, both fitted as standard to the Zed over the years, both just one number apart, both completely and utterly different. This is absolutely key in understanding why mixing tyres is a bad idea.

 

I've driven on both of these tyres in the dry, the wet and on track, and they are even further apart than they now look. The RE040s are noisy, uncomfortable, have good grip in the dry but atrocious grip in the wet; The RE050s have a very progressive feel, outstanding water displacement at high speed and excellent dry traction. They're the tyre equivalents of a Ford Escort and a Ferrari Enzo. That said, as long as you keep all four tyres on the car the same (be it all 040s, all 050s, or whatever you prefer) you'll find a car stable and predictable. Now what happens if you mix them...

 

 

 

 

Let's think about this logically. Let's picture the Top Gear test track at Dunsfold as it's a place just about everyone is familiar with, and let's say it's bone dry. Our test car is a stock 350Z naturally, and in the first instance is fitted with RE040s all round. Get in, drive, enjoy. No issues at all, car feels just like it should. After a few laps it starts raining, so you adjust your driving and speed to match. Car feels noticeably slower, tyres have nowhere near the grip you're used to, but nothing feels drastically out of place. Car goes back into the pits, time for a spot of lunch, and ZOMG! THE SUN'S OUT! YAY FOR A DRY TRACK IN THE AFTERNOON!

 

Now we leave the RE040s on the front but put RE050s on the rear. Jump in the car, off you go, giving it full beans. Will you notice any great issues? No, probably not. Remember, both tyres are good in the dry, so you'd expect the car to be fairly balanced. It handles just like it should, but you do notice a bit more traction from the back when coming out of the Hammerhead.

 

Soon the heavens open and the track is soaking wet. Same car, same setup (40s on the front, 50s on the rear), same driver. Once again, you go for a fast lap. First time round is slow as you get used to the wet surface again, then you start picking up the pace as you get used to the conditions again. You come round Chicago and brake hard for the Hammerhead, and start to turn in. The front washes ridiculously wide and you're in the gravel. Why? The RE040s have much less wet grip than the RE050s, and so you get chronic understeer despite the rear feeling very planted.

 

Now we change the tyres around, so that the 40s are on the back and the 50s on the front. Same wet conditions, same driver. Out of Chicago, onto the power, brake hard for Hammerhead, car turns in fantastically well to the left, same to the right, but the second you get onto the power coming out the arse end overtakes you and you're suddenly facing the wrong way. As you've put the grippier tyres on the front the car now wants to oversteer everywhere, and as you carry on round the track and all tyres get hotter the differences become more pronounced.

 

 

 

Yes, very huge and over-complicated scenario perhaps, but it illustrates the basics very well. There's a million and one things you can do to adjust grip balance between front and rear (suspension settings, weight balance, tyre pressures etc) but all those things will give you a subtle difference you can learn: Completely different tyres will always behave at such extremes you'll always struggle to cope, and that's on track when you've got the space to get it a bit wrong. Tracks are made of one material and all laid at the same time (for the most part, airfields are a different kettle of fish), and as such you can almost cope with different tyres as the road surface doesn't change. I can't think of too many roads in the UK that are the same!

 

Imagine you're driving on a motorway at 70mph in our mixed-tyre Zed in the rain. You're in a straight line, in all honesty very little is going to go wrong. Suddenly there's a car in front you of that you need to overtake, so you indicate and pull out to the right. At the same time you happen to cross a section of road that has been repaired and replaced so has different grip to the rest. Your axle with 050s on takes it fine but a combination of surface, temperature, camber, suspension travel and steering angle combine to make the 040s aquaplane and you suddenly find yourself in a spin at 70mph in the middle of the M6. Your odds of walking away are pretty slim at this point.

 

If you were on 040s all round you'd know how crap they are in the wet and drive appropriately, but on mixed tyres you don't get that kind of warning as you're getting such mixed signals. It's not a scenario that would happen often, but given the nature of driving would you really want to take that chance? There are so many different variables on a car and we take them all into account when driving, most of them subconsciously, and I simply can't understand why people would want to add another one in there just for the sake of a couple of quid. Let's make no mistake here: Mixing tyres is done 99% of the time because people are too tight to buy the correct tyre. That goes for all other cars as much as it does for the Zed. You need a new set of rears a couple of thousand miles before the fronts, but instead of replacing them all with something different people tend to take the cheap option, and then wonder why the car feels horrible to drive.

 

 

Driving isn't cheap, I appreciate that, and sports car driving even more so, but is it worth risking your £10,000 car for the sake of a couple of hundred quid? No, of course it isn't and anyone who does so knowingly is an utter fool. If you can't afford to swap tyre brands for something different then don't! Some tyres are better than others but ALL tyres have been through EU type approval, which makes them all perfectly safe to use on the road. A set of Michelin Pilot Sport 2s will be infinitely better than a set of Nankang Ditchfinders, but a car with four Nankangs will be more controllable, more predictable and safer than a car running two of each. There's so much more to it, not least of all different compounds, different thermal expansion points at set temperatures, amount of water dispersed at set speeds... So much detail that you need a degree in physics to understand it all properly. Thing is, common sense is more than enough once you know the basics. I appreciate that there are people out there running mixed tyres who say that it's perfectly safe and they've never had an accident, and good luck to them in that, but I maintain it's always just a matter of time and the wrong circumstances that is going to lead to tears. It might not even be their fault: It might be the idiot that pulls out without looking causing them to swerve and end up in an emergency situation that they have no control over due to mixed tyres. Hell, that could happen even on matched tyres, but I know which is going to give you a more predictable and balanced car to give you the best chance of getting yourself out of any trouble.

 

 

 

 

I'll leave you with a thought: There's not a car manufacturer in the entire world who supplies their cars with different tyres on. Their combined research budget is billions of billions of pounds. There isn't a single professional race series that would ever consider running mixed tyres, and they're aiming for hundredths of seconds so surely if it gave them an advantage, they'd do it. It won't, and they don't.

[martinmac]

Great post Dan, that explains the issue very clearly.

[tmJak]

So am I ok to mix falcons on the front with toyos on the rear?

 

 

 

 

 

 

Very informative write up, thanks. I never properly understood why you shouldn't mix, but makes sense when you say it like that

[rtbiscuit]

well said Dan, a top right up and worded so much better than i ever could.

 

this man knows his cars, his tyres and his race tracks, this is not the ramblings of a car geek but the wise words of someone who knows more than most.

[kevlo]

good right up. very clear.

 

could the same not be said for different levels of tyre wear though which is completely unavoidable.

 

i.e my old company car was a vauxhall astra vxr and that would go through 2 sets of front tyres before the rears needed replacing. i think the combination of my spirited driving and too much power in a fwd car had a lot to do with it.

 

anyway the point is whilst my front ones are wearing out and the back ones are fine then surely these would react the same way as having two different brands of tyres on front and back. grippy on the back and not so much on the front.

 

i dont believe however that people would go about replacing half worn tyres just to match them up every time you get unbalanced levels of tread.

 

not arguing with what you have said but i just dont believe its as scary a situation as you make out. (just my two pence worth).

 

as long as you learn the tolerences of your car and drive to its limits

[andlid]

 

Sweet reading, make it stick!

[ATTAK Z]

 

...............i dont believe however that people would go about replacing half worn tyres just to match them up every time you get unbalanced levels of tread ..........

 

The Germans do ... they have done it for years ..... where do you think the part worn tyres sales places get their tyres from ?

 

Oh and 'cellent explanation Ekona

[Chris`I]

Great write up Dan

 

good right up. very clear.

 

could the same not be said for different levels of tyre wear though which is completely unavoidable.

 

i.e my old company car was a vauxhall astra vxr and that would go through 2 sets of front tyres before the rears needed replacing. i think the combination of my spirited driving and too much power in a fwd car had a lot to do with it.

 

anyway the point is whilst my front ones are wearing out and the back ones are fine then surely these would react the same way as having two different brands of tyres on front and back. grippy on the back and not so much on the front.

 

i dont believe however that people would go about replacing half worn tyres just to match them up every time you get unbalanced levels of tread.

 

not arguing with what you have said but i just dont believe its as scary a situation as you make out. (just my two pence worth).

 

as long as you learn the tolerences of your car and drive to its limits

Not quite the same I'm afraid. Different treat depths are not the same as different tyre compounds. Different tread depths will largely react the same, apart from at the very beginning (as it has tyre release agent on them which is slippy) and towards the end when they become slippy again as you loose tread. The tyres for the most part will react exactly the same, or at least so close you will never notice, apart from in the wet when the lower ones will not be able to clear as much water and will slip sooner.

 

So while I appreciate your logic, its not the same, and Dan is spot on with his write up, and no matter how many people try to argue it, he is right

[andlid]

 

...............i dont believe however that people would go about replacing half worn tyres just to match them up every time you get unbalanced levels of tread ..........

ly.

The Germans do ... they have done it for years ..... where do you think the part worn tyres sales places get their tyres from ?

 

Oh and 'cellent explanation Ekona

just imagine if their was a law in whole of europe to use winter spec tyres... I know that the Swedes normally change their wheels around during thread wear. /back fronts lefts rights etc... Some rubber u cant do that with obviously

[rtbiscuit]

could the same not be said for different levels of tyre wear though which is completely unavoidable.

the legal limit in the UK is asomething like 1.3-1.6 mm; its the legal limit not the target for change. in places like germany the limit is something like 3mm. form 3mm and down the effectiveness of the tyre to disperse water is not as good and so its grip is not as effective in the wet.

 

anyway the point is whilst my front ones are wearing out and the back ones are fine then surely these would react the same way as having two different brands of tyres on front and back. grippy on the back and not so much on the front.

 

regardless of tread depth your still running the same compound; compounds react differently in different conditions. running the same compound with less tread is still better than running to different tyres with different tread patterns and compounds; which both disperse water differently at different temperatures

 

i dont believe however that people would go about replacing half worn tyres just to match them up every time you get unbalanced levels of tread.

 

they won't but they should; our road laws are alot more lax than places like germany who have a higher minimum tread depth and who also don't repair tyres. if you get a puncture its usually a new tyre. hence the roaring trade in selling german part worns and repaired tyres. what is unacceptable for one country is a cheap alternative for another.

not arguing with what you have said but i just dont believe its as scary a situation as you make out. (just my two pence worth).

 

as long as you learn the tolerences of your car and drive to its limits

 

all well and good till you get the one situation you cant control

[andlid]

Should we not also be talking about age of tyres and not only wear?

[rtbiscuit]

Should we not also be talking about age of tyres and not only wear?

 

in germany the tyre life span is 3 years. again they get replaced and then sold over here. i replace mine at 3mm or 3 years which ever comes up first

[Chris`I]

Should we not also be talking about age of tyres and not only wear?

 

in germany the tyre life span is 3 years. again they get replaced and then sold over here. i replace mine at 3mm or 3 years which ever comes up first

And make sure you use places that get through tyres quite a lot so they are always new. Camskill for example go through loads, and IIRC dont they state they will never give you tyres produced more than 2 years ago?

[Ekona]

Thanks for the kind words chaps, much appreciated

 

 

Tbh I could write for hours on the subject of tyres and there was so much more I wanted to write but had to leave out to save it becoming an utter bore to read, and everyone who has mentioned that there are other factors involved in tyre decisions (especially but not limited to wear) is bang on the money. That's partly why choosing tyres should be about common sense as much as knowing the exact details, and basically if you think that there might be an issue mixing old and new then there probably is, and you should seriously consider spending that little bit more to get a good match all round. This applies to every car really, but given that sports cars are usually driven a bit more enthusiastically than shopping carts it's worth being a but more cautious than you might be otherwise.

 

As a general rule I'll run my tyres down to about 3mm and then spend a trackday or two killing them off completely, the one exception being the trackday special R888/A048 as they only come with 4.5mm (ish) anyway so you'd constantly be changing tyres if you swapped at 3mm.

[andlid]

you guys buy old rubber from germany?

[magic84]

really good write up there. you have me thinking now on what to do about my tyres. ive currently got bridgestone re040 which i hate due to road noise, and wet weather handling.

 

the front tyres have 6mm left, and the rears have 1mm left in the center. if the fronts had 3mm or less i wouldnt think twice about changeing all 4.

 

so heres were i need your help do i.....

 

buy new rears for £288 and so on untill the fronts are dead.

buy 4 new falken 452's for £401.16 and sell the fronts.

[rtbiscuit]

option 2

[GT4 Zed]

Nice write up Dan and overtly simplified to cater for varying depth of knowledge within the forum. I had covered this and actively discouraged people mixing tyres on each axle when i supplied part worns here. Worse still to mix on the SAME axle which is cardinal sin and asking for trouble People need to inform themselves period: before buying tyres especially and if they decide not to keep the OEM tyre rather than just do so on hear say or unfound recommendation or anecdotal evidence!

 

There are other areas to I'm sure you left out for sake of not sounding to techie or boring such as thread depth difference, speed rating, load index etc which are also important to keep to OEM requirements. I have seen people with 4 cheap chinese stuff and with wrong ratings which is bad Anders also nicely pointed out tyre age being important too

 

The only part i donot totally agree is your last statement about racing . YES sometimes it is an advantage to use mixed componds on different axles to achieve certain handling characteristics and is common practice in professional racing

But at the end of the day one cannot transpose this into road cars so it really does not matter for our purposes

[Ekona]

so heres were i need your help do i.....

 

buy new rears for £288 and so on untill the fronts are dead.

buy 4 new falken 452's for £401.16 and sell the fronts.

How much do you hate the RE040s? If you really hate them then yes I'd change, but if money is a big issue then no harm in getting a fresh set of rears which should hopefully die by the time you need new fronts.

 

 

 

 

 

The only part i donot totally agree is your last statement about racing . YES sometimes it is an advantage to use mixed componds on different axles to achieve certain handling characteristics and is common practice in professional racing

But at the end of the day one cannot transpose this into road cars so it really does not matter for our purposes

Very much depends on the race series and what cars are being run, but you are of course correct. I should have made my last sentence clearer really, I was referring more that race cars don't run mixed tyres rather than they don't run mixed compounds.

[GT4 Zed]

Dan, since you have good experience with the R888 and A048 which is better and has longevity? (asumming you are using medium compounds whcih is what i plan tp get)

 

I am fed up with cleaning my 19" which i refurbished and PC'ed 3months ago and looks sorry for itself The brake dust from my race pads(PF01) is just murder

 

I want to get OEM Rays just for trackday which will be lighter and should save a bit on smaller 18" trackspec tyres

[Husky]

having run a car with mixed nankangs and re040's i can absolutely confirm everything you have written, the nankangs being on the front made the car wildly understeer in the dry and then the bridgestones being on the back made it wildly oversteer in the wet.

 

utterly ruins the car, glad i finally got rid.

 

great write up, hope people use some common sense now.

[Millzzz]

Ive got to say, excellent thread. Idiots guide's are exactly what I need! Bit pi**ed off with the previous owner of my z now. Git put 4 different tyre makes on all corners! I've have spun it once too. Really hot then suddenly rained. Just turned into a junction & ended up 90 degrees to the road!

Nice shiny new yokohama's all round now though

[Ekona]

Dan, since you have good experience with the R888 and A048 which is better and has longevity? (asumming you are using medium compounds whcih is what i plan tp get)

 

I want to get OEM Rays just for trackday which will be lighter and should save a bit on smaller 18" trackspec tyres

Exactly why I got a spare set of Rays, really can't beat them for trackday wheels

 

I'm currently using the R888 in GG (med) compound and used to run the A048s on the VXR in LTS spec which is somewhere between M and MH IIRC. I've never run the two on the same car and realistically never will seeing as how Yoko don't make the sizes I want in the 048, but I can go on what I do know which is that I'd pick the R888s any day. I've yet to track the R888s (next month at the 'Ring will see them get their outing) but on the road there is 95% of the grip of the 48s but with 105% of the feel: They're slightly more progressive than the Yokos which tend to give less warning when they're about to go. I think the Toyos also have better wet traction than the 048s, but that's like saying I'd rather bang Nadine from Girls Aloud than Kelly Brook: Technically true, but you'd be really happy riding on either

[GT4 Zed]

Thanks Dan, I thought it will be the R888 and you have confirmed it. I have only used MPS cups with 3.5mm left on the zed and was disapointed. Was crap to start with, then once the old sheen had come off and was up to temp it gripped for about a lap and then just gave up suddenly But it will be unfair to rate it since i did not try them from new

 

If for any reason you need tyres when you are there i will pm you a contact to help out. He actually runs the Nissan in Adenau and can get you the ultra performance MPS, Continentals road/track at trade price He quoted full 245/35/19 and 275/35/19 for MPS cups @ Eur800- including fitting. Can also rent lightweight wheels FOC if you by his tyres and has a facility where you can store your wheels/tyres ad lib and use them on subsequent visits.

 

Cheap service and geo too. He ran a GT4 spec 350z on the ring for a while so has good advice on settings but Porsche is his first love like all germans.

[D4XNY]

Really good writeup, makes perfect sense to me.

 

Its just financially, its not always the practical thing to do thats all.

 

When i bought my car last year, it had good front tyres, good years I think, but bad rear ones, so before I took delivery, I made sure he replced them, which he did.

 

However he fitted an avon to one side and a yokohama to the other.... (both had very similar tread pattern so I thought fine)

 

After 7 months, I damaged one of the fronts, so decided to replace the both as a pair, and got a brand new set of kumho ecstas (which i always found very good on previous cars) However I wasnt getting the grip i was expecting, (maybe now realising i had 3 different makes of tyre) I also lowered the car, and fitted 20mm spacer and had a full laser allignment done.

 

Having taken the wheels off last week to sell, i noticed the yokohama tyre has worn significantly more than the avon tyre (now i first thought, maybe i need allignment done again) now i realise its having different tyres...

 

Anyway, I have bought a new set of wheels and reassured (after reading this) that I have bought falkens for all 4 corners! hopefully I will notice the difference in handling now!