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

[andlid]

Just admit it... you're getting confused

This thread is now going to be so confusing for a newbie looking for a simple answer to a common question. Can we just move the discussion elsewhere and sticky the original post on its own locked? Maybe with a link to the discussion?

 

Just i see this going on for 10's of pages

[Husky]

not at all but its becoming an epic yawnfest no one will ever read and the really valuable info will be watered down by all the debate. not saying we shouldnt have the debate just not on the sticky thread.

[andlid]

not at all but its becoming an epic yawnfest no one will ever read and the really valuable info will be watered down by all the debate. not saying we shouldnt have the debate just not on the sticky thread.

think you're correct in that, take off all the commentary and put a link to it on the first thread for discussion just like was done with the dyno sheets...

[Scottie]

he's only giving free advice to keep you on the road....and full marks to Dan Thank you.

 

I'm happy to see their is a good debate, but...I'd still like the fundamental flaw in the original post to be answered...

 

"Does uprating the rear tyres from 040's to 050's whilst leaving your fronts at 040's mean you are suddenly more likely to crash or have an unstable car?"

 

How...you have not affected the front, it still has the same lateral grip as before...still the same braking grip...in fact all you've done is make the car more stable in the wet as the rear is less likely to let go because it will clear standing water quicker and will have slightly better lateral grip as a result.

 

Perhaps somebody could ask Bridgestone this question...I think I know what the answer would be. Before posting this free advice up I think it really had to stand up to some scrutiny. I'm open minded on car issues, and would love to be convinced I'm wrong here because then I'd have learned somethien that may help me :-)

[Husky]

Right give me a couple of hours i will contact someone in the handling dept at work. Will sort this out.

[andlid]

he's only giving free advice to keep you on the road....and full marks to Dan Thank you.

 

I'm happy to see their is a good debate, but...I'd still like the fundamental flaw in the original post to be answered...

 

"Does uprating the rear tyres from 040's to 050's whilst leaving your fronts at 040's mean you are suddenly more likely to crash or have an unstable car?"

 

How...you have not affected the front, it still has the same lateral grip as before...still the same braking grip...in fact all you've done is make the car more stable in the wet as the rear is less likely to let go because it will clear standing water quicker and will have slightly better lateral grip as a result.

 

Perhaps somebody could ask Bridgestone this question...I think I know what the answer would be. Before posting this free advice up I think it really had to stand up to some scrutiny. I'm open minded on car issues, and would love to be convinced I'm wrong here because then I'd have learned somethien that may help me :-)

Eh would be pretty interesting to see what Bridgestone says.. think I know what they'll say = DONT MIX tyres use the same on all four corners.

[andlid]

Right give me a couple of hours i will contact someone in the handling dept at work. Will sort this out.

[Chris`I]

he's only giving free advice to keep you on the road....and full marks to Dan Thank you.

 

I'm happy to see their is a good debate, but...I'd still like the fundamental flaw in the original post to be answered...

 

"Does uprating the rear tyres from 040's to 050's whilst leaving your fronts at 040's mean you are suddenly more likely to crash or have an unstable car?"

 

How...you have not affected the front, it still has the same lateral grip as before...still the same braking grip...in fact all you've done is make the car more stable in the wet as the rear is less likely to let go because it will clear standing water quicker and will have slightly better lateral grip as a result.

 

Perhaps somebody could ask Bridgestone this question...I think I know what the answer would be. Before posting this free advice up I think it really had to stand up to some scrutiny. I'm open minded on car issues, and would love to be convinced I'm wrong here because then I'd have learned somethien that may help me :-)

Uprating the rears to 050's from 040's, while leaving 040's on the front will make the car inherintly have more understeer. Car manufacturers believe this to be the better combo, as this is what they dial into cars as standard. In the dry you will likely not notice, in the wet however, the front end could wash out much more easily, which is dangerous, but not as bad as the opposite and having oversteer.

 

Good work John, look forward to seeing what they say

[Scottie]

Uprating the rears to 050's from 040's, while leaving 040's on the front will make the car inherintly have more understeer. Car manufacturers believe this to be the better combo, as this is what they dial into cars as standard. In the dry you will likely not notice, in the wet however, the front end could wash out much more easily, which is dangerous, but not as bad as the opposite and having oversteer.

 

Good work John, look forward to seeing what they say

 

The bit I don't understand though is that if for example the front will not understeer in a wet corner till 50mph on RE040's all round, then if you uprate the rears only to RE050's are you saying that this causes the front to understeer at less than 50mph now even though it's still on the same tyres?

[H5]

he's only giving free advice to keep you on the road....and full marks to Dan Thank you.

 

I'm happy to see their is a good debate, but...I'd still like the fundamental flaw in the original post to be answered...

 

"Does uprating the rear tyres from 040's to 050's whilst leaving your fronts at 040's mean you are suddenly more likely to crash or have an unstable car?"

 

How...you have not affected the front, it still has the same lateral grip as before...still the same braking grip...in fact all you've done is make the car more stable in the wet as the rear is less likely to let go because it will clear standing water quicker and will have slightly better lateral grip as a result.

 

Perhaps somebody could ask Bridgestone this question...I think I know what the answer would be. Before posting this free advice up I think it really had to stand up to some scrutiny. I'm open minded on car issues, and would love to be convinced I'm wrong here because then I'd have learned somethien that may help me :-)

Uprating the rears to 050's from 040's, while leaving 040's on the front will make the car inherintly have more understeer in the wet. Car manufacturers believe this to be the better combo, as this is what they dial into cars as standard. In the dry you will likely not notice, in the wet however, the front end could wash out much more easily, which is dangerous, but not as bad as the opposite and having oversteer.

 

Good work John, look forward to seeing what they say

 

Amended to what I think you meant Chris?

 

As another example of what I think Dan is trying to say....

 

I had an old show car that was lowered to within an inch of it's life, had a boot full of ICE etc. and I used to have quite a bit of involvement with Yokohama. So it was running on Yoko A539s all round. This was fine, the car still had the manufacturer level of understeer (proportionally) when pushed and in the wet it was a little bit of a handful with the suspension being so firm. But I knew that it would always understeer.

It got to the point I needed to replace the fronts and Yokohama didn't have any stock of the A539s. So I looked around and ended up getting some BF Goodrich tyres that were noted for their wet weather performance. While in the summer I didn't notice too much difference. The first burst of rain came and something started coming out..... While doubling back around a roundabout that I know very well from my years of living down the road from it, I noticed the front end gripped a bit more than I expected. A nudge of the throttle and a lift off and waheeyy! Steering from the rear in a Volvo! If it had been with A539s on the front (which I had had for the previous 3 yrs on the same car) then it would have just pushed the nose wide and then gathered back in. So much so that in my FWD car I could practically get the rear end to step out on demand in the wet! Up until this point I was really skeptical about all this stuff about mixing tyres. It wasn't a large speed but it was definitely noticeable and caught me out. So if you're not expecting it, you would be more likely to crash I would say!

 

So if you wanted it to handle like that in the wet, then fine. But keeping the tyres the same all round will keep the handling in both wet and dry conditions pretty much as the manufacturer intended. I think that's what you're saying Dan?

[Chris`I]

Uprating the rears to 050's from 040's, while leaving 040's on the front will make the car inherintly have more understeer. Car manufacturers believe this to be the better combo, as this is what they dial into cars as standard. In the dry you will likely not notice, in the wet however, the front end could wash out much more easily, which is dangerous, but not as bad as the opposite and having oversteer.

 

Good work John, look forward to seeing what they say

 

The bit I don't understand though is that if for example the front will not understeer in a wet corner till 50mph on RE040's all round, then if you uprate the rears only to RE050's are you saying that this causes the front to understeer at less than 50mph now even though it's still on the same tyres?

Logically no, but if the limit if grip for a given corner in the wet for the 040's is say 50MPH and the 050's is 60MPH, whereas at 55MPH before, you would first get understeer, followed by a slide as all 4 tyres lost adhesion, with a combo of 040/050 F/R, the rears would still grip at 55MPH, so rather than inducing a slide of all 4 tyres, you would get pure understeer, which is different handling to what you would expect. That is what will catch you out, not that it will or wont understeer, but that it will do something different to before

 

And yes Rob thats what I meant to say, thx for the correction

[Husky]

Ok so i gave him the original post:

 

That post is well written and fairly complete, all i could add is more info which could explain some of the stuff he describes. It could work but not worth it in my book unless you spend a day at a test track doing back to back comparisons. It's not the best plan from anything but a financial point of view.

[docwra]

Ive just nicked a couple of quotes:

 

So if you wanted it to handle like that in the wet, then fine. But keeping the tyres the same all round will keep the handling in both wet and dry conditions pretty much as the manufacturer intended. I think that's what you're saying Dan?

 

That is what will catch you out, not that it will or wont understeer, but that it will do something different to before

 

 

And I dont think anyone could disagree with them - obviously the car will behave differently to before if something as intrsic as the tyres have been changed. However, one could probably argue it would behave a lot more differently from the manufacturers intention with uprated suspension, wider wheels or even after a 4 wheel alignment, but I bet most of the people on this thread havent worried about that when they have upgraded. It comes back to my original post - you drive to the conditions, be that trolley castors or slicks off an F1 car.

 

Scottie seems to see my point - if a car understeers at 45mph on RE040's, but only at 55mph on RE050's then thats an improvement, isnt it?? What you are running on your rears doesnt have any bearing on that, matched or otherwise.

[Husky]

another few quotes from the convo about this with a couple of guys in handling.

 

Since tyre characteristcs are nonlinear as you push hard you are much more likely to mess with the under/oversteer characteristics as the two curves are not similar

Bear in mind tyres DOMINATE how your car handles, maybe mixed tyres would be awesome and add to the cars behaviour but without loads of information i'm not sure why you would try

Fair enough go ahead and do it if the relevant test work has been done and the result is what you want to achieve with the handling of the car. Otherwise you are just blindly taking guesses based on what you've learned on forza motorsport, something that could potentially end your life.

[docwra]

something that could potentially end your life.

 

Sorry, driving like an idiot will potentially end your life.

 

To suggest that running mismatched tyres front and back, something I and most of the people I know have been doing for years is just total scaremongering. They arent suddenly going to steer you in a ditch unless you are driving too fast and that could happen on a matched set of the best tyres in the world.

 

Like I said, I dont disagree with the principle, but dont you think thats a bit much?

 

Anyway, Ive sent the information over to the OP but there are at least two cars that have mismatched tyres fitted as standard. Obviously the manufacturers are keen for their customers to "end their life"

[rtbiscuit]

 

Sorry, driving like an idiot will potentially end your life.

 

 

just getting in a car has the same potential, regardless of how good your driving is, there are several million other people out there who arent always as careful.

 

the argument over how severe it could/couldn't be is a bit pointless, all thats happened is the info has been watered down.

 

i've been on forums for years, with different cars, and on several of them when ever someone had an off or an accident and you asked them what tyres they were running 99.9% had mixed tyres on.

 

you may well be a competant drifter and have good balance in your car, but most of the drivers on here aren't; there is only a small group of track day people on here. who to be honest this info is minimal. but for the joe bloggs out there it puts it in simple terms and makes something that not everyone gets a bit more understandable.

[Husky]

something that could potentially end your life.

 

Sorry, driving like an idiot will potentially end your life.

 

To suggest that running mismatched tyres front and back, something I and most of the people I know have been doing for years is just total scaremongering. They arent suddenly going to steer you in a ditch unless you are driving too fast and that could happen on a matched set of the best tyres in the world.

 

Like I said, I dont disagree with the principle, but dont you think thats a bit much?

 

Anyway, Ive sent the information over to the OP but there are at least two cars that have mismatched tyres fitted as standard. Obviously the manufacturers are keen for their customers to "end their life"

 

 

incorrect, the manufaturer will have done the required testing to prove that, that particular combination of tyres achieves what they want from the set up.

 

Do the testing to prove the set up you choose produces your desired effect in various conditions, log the data, post the results. The data that does exist is that 9X% of manufacturers use all matched tyres and reccomend replacing with all matched and in some cases (eg porsche) will void your warranty for not doing so. The data for using mismatched tyres is where?

 

This discussion is just full of assumptions. Have data to back it up or dont post it, graphs, tables, diagrams, numbers, statistics, charts.

[Ekona]

I'm happy to see their is a good debate, but...I'd still like the fundamental flaw in the original post to be answered...

 

"Does uprating the rear tyres from 040's to 050's whilst leaving your fronts at 040's mean you are suddenly more likely to crash or have an unstable car?"

Yes. Yes it does.

 

How...you have not affected the front, it still has the same lateral grip as before...still the same braking grip...in fact all you've done is make the car more stable in the wet as the rear is less likely to let go because it will clear standing water quicker and will have slightly better lateral grip as a result.

No, you've changed the entire balance of the car. You've given the rears better grip so you've shifted the bias for both braking and grip backwards, which creates an inherent instability. If your rears have more grip than the front you will experience understeer. You can do that with mixed tyres, tyre pressures or altering the width of the tyres, but the end result is exactly the same. I'm struggling to put it in simpler terms for people to understand, I really don't think it's that hard to comprehend.

 

 

 

As far as Docwra and the manufacturers with mixed tyres go, I'm investigating that as we speak. It is true that Pirelli make some tyres that are completely different externally that they claim are safe to work together, and I was unaware of this when writing the original post. I've e-mailed them directly for clarification, and have recieved the most generic response back you can possibly imagine: As such, I intend to push them for details and will post up the results here. All I will say at this point is that at least Pirelli have designed these tyres to work together, despite their apparent mismatch, and so that could explain why they feel happy to recommend this. I have my doubts as to any cars that come with the mixed setup from Pirelli as OEM, however Docwra has first-hand evidence that they do and unless I can prove otherwise I bow to his knowledge on that. That said, as far as I am concerned with my own experiences and research I am still very comfortable saying that putting mismatched tyres onto your car is something only a fool would do.

[Chris`I]

OK, just had this from the horses mouth - Nissan GB Sports Car Product Manager - I hope this is the end of the matter as he knows how these systems work in fairly minute detail.

 

Mixing of tyres / compounds should never take place unless they have been thoroughly tested together for quite basic reasons –

 

Different compounds / patterns will operate differently in different conditions – wet / dry, hot / cold, fast / slow corners, braking and at high speeds. ESP / ABS systems are designed around the grip conditions of the chosen tyre compounds. Even the rotational size can be different with different makes and this can upset not only speed readings but also traction control systems (especially on GT-R).

 

Should the tyres be different either front to rear or side to side then not only will each tyre lose grip at different times to each other the systems controlling the vehicle could also get confused and not work to manufacturers tested settings. Main point to remember is …..when would you find out it does not work properly….oopps too late! Insurance…hmmm maybe.

[Husky]

ok seems all the experts we have sourced agree with this 100%, its not been tested, its a bad idea.

[Scottie]

This discussion is just full of assumptions. Have data to back it up or dont post it, graphs, tables, diagrams, numbers, statistics, charts.

 

ok seems all the experts we have sourced agree with this 100%, its not been tested, its a bad idea.

 

Is this contradicting yourself? You state you want data to back this up in the form of graphs, tables, diagrams etc, yet none is posted for the statement you agree with.

 

I'd love to see the data that the "product manager" uses to back this up. Being a Nissan product manager does not make you a tyre expert...I don't even trust Nissan to service my car correctly :-) I'm sure Nissans official advice is not to change the exhaust or pads for different etc...but doing so can have benefits not make it unsafe. What do you expect the Nissan manager to say? He's unlikely to say "yes different sets are ok" in case you crash and sue him - much easier just to stick to the line that can't get you blamed.

 

At the moment I have 040's on the front and 050A's on the rear of one car, (changed from 040's all round) that has been pushed hard in dry and wet around the Ring, and my other car has had a mix of tyres as well.

 

In fact, if 20 years of driving some very fast cars I've never had an issue with different tyres front and rear (always matched on the same axle though) which is until I see why some definite proof to the contrary I am very sceptical. I've not pusst footed around in my cars either...my tyre bill can testify to that lol :-)

[martinmac]

Try a 350z with mixed tyres and you may see that there are issues. There are plenty of threads on here about it so I wont bother repeating them.

[andlid]

Try a 350z with mixed tyres and you may see that there are issues. There are plenty of threads on here about it so I wont bother repeating them.

that fine I see where Scottie is pointing and he does have a point... even though what you say is true... and we all know better, suprised how many people still go on and get uneven pairs and complain afterwards...

[martinmac]

I agree Anders bit the OPs post was after many discussions on the subject and was intended to help owners to balance the cost/safety issues on their zeds. I would imagine books have been written on the subject but as a short, to the point guide I cant fault it.

[andlid]

I agree Anders bit the OPs post was after many discussions on the subject and was intended to help owners to balance the cost/safety issues on their zeds. I would imagine books have been written on the subject but as a short, to the point guide I cant fault it.

Completely agreed on that, I would be interested in getting to some sort of bottom to the subject but think that Husky was correct in asking for a seperate thecie thread. hoepfully the first thread will help new people to make the correct decision.