Scottie

I think some of us are going to have to agree to disagree on this unless we can get some definite proof. I'm a technical professional, and I am completely open to any data somebody wants to present to me, in fact I'm sad enough to enjoy interpreting it :-) I do like to analyse the source and reliability of any given information though. What I am interested to know is whether anybody claiming running 050's at one end and 040's at the other end results in an unstable car and crash waiting to happen is actually running this setup. Because I am and it's superb. Generally I do try and match all four tyres to the same brand, but when buying a car with 040's all round, the rears went and IMO it's better to replace these with 050A's and then when the front go put 050A's on them. There's a good chance I'll be using my car to compete in TOTB this year, so hopefully we'll get to see just how stable it is on the handling circuit with this mix of tyres...if we get some rain we should even get some good lap times :-) I think there is far more we agree on here than disagree on, and really the difference between what we are saying will in real live be minimal effect.

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 :-)

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?

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 :-)

I can't make sense of this. What you're are saying is : Scenario 1 : Car has 4 RE040's and is lapping in the wet. Scenario 2 : Car has front RE040's and rear RE050's lapping in the dry. Scenario 3 : Car has front RE040's and rear RE050's lapping in the wet, as scenario 1. Scenario 4 : Car has front RE050's and rear RE040's lapping in the wet. You seem to suggest that it's better to have a car with the four worst tyres, and somehow uprating the rear tyres will cause the car to crash in scenario 3. How is this? The front tyres are the same and conditions being the same will offer the same leve of lateral grip and braking grip. Just changing the rear tyres won't cause the car to understeer, it will be the driver deciding to take the corner at a higher speed. Again upgrading the front to 050's whilst leaving the back the same 040's will also offer a better scenario from all beign 040's, because the front will have more lateral grip, and better braking in the wet as well, whereas you have no less traction or grip from the rear so should have no less grip unless you choose to accelerate harder than before. I have had a succession of different cars with a mix of 040's and 050's on the front and rear. Two weeks I came back from the Ring which has some very wet days, and upgraded the rear from 040's to 050's with the front still on 040's and all I got was extra traction. I didn't suddenly maek the car understeer or have less grip at the front because I still had the same lateral grip as before. My track car is sending 400bhp to the rear wheels, and upgrading the fronts to 050's before I have just upgraded the backs didn't make it any more unstable in dry or wet. In fact it gave me extra grip on the front in the wet, and the back still had the same as you would expect on the same tyres. Through both theory and many years experience I thoroughly agree with Docwra on this, it's more important to have matched tyres on the same axle and good pairs than it is jsut to match all four. Very interesting topic though :-)