question on changing tire brand - wondering what you guys think?

This past week at GIRO I met a Lambo corporate guy who trains the Lambo techs. We got into a lengthy, detailed discussion on tires because last week we mounteed Michelin Pilot Super Sports on the Callistos. The PZeros were past 50% life but more important were getting old. We wanted good tread for our trip where we correctly anticipated some wet conditions. We love the MPSS that we have on the zeeeooooosixxxx - they are fantastic as DD, track, and in wet, and have worn like iron.

 

The tech said this is a bad move. He explained in detail the viscous coupler (essentially like a wet clutch) works on a signal from the computer (CAN) to put more torque to the front wheels. Lambo goes to great lengths to homologate the system with approved tires (Pirelli PZero & PZeroCorsa) on OEM wheels. The rolling circumference on tires can vary even if they are the same size and spec. It further varies depending on the rim to which it's mounted. And it varies even more under dynamic measure (which they don't really do). Plenty of things can change the rolling circumference including air pressure, rims, ambient temp not to mention distortion at highway speeds due to different compounds and maybe other factors not known or catalogued.

 

It may not be off much - but even a small difference in rolling circumference measurement will be multiplied exponentially at highway speeds and dramatically increase the signals received by the viscous coupler.

 

His point: if the CAN sends a signal to put torque to the front wheels at "X" times at "X" mph - if the rolling circumference is off (or out of measured tolerance for how the system was homologated) - it may send many more signals and prematurely burn out the viscous coupler. They have documented cases of problems that disappeared when tires were changed and they think it points to differences in rolling circumference.

 

This guy is passionate and extremely knowledgeable about Italian cars and has an obvious love for all thing automotive. He is hands on and learns by taking stuff apart (he is not just book smart but has tons or real world tech experience on lambos especially but other italian brands too). He has nothing to sell and could care less about the Pirelli brand. His main concern seemed to be for us not to screw up our car - and he recommended we ditch the MPSS and go back to Pirelli.

 

Maybe a car that won't rack up miles won't see a problem. As you guys know - we DRIVE our car - and I don't plan to stop. It's been relatively trouble free with only minor annoyances - all fixed under warranty (which has since expired). It seems pretty bullet proof - and I respect this guy's opinion. I know many who go with after market rims and different tires and I'm not reading about lots of problems - but maybe it's because most of those cars are very low usage (low miles).

 

I love the MPSS but don't want to create a mechanical problem. For those who don't know - it's a 2009 LP560. I bought it new in 2011 and it currently has 14,000 miles. It's stock.

 

Thought I'd put this question out here for the "devil's advocate" point of view and to see if anyone else with a "driven" car on "unapproved" tires has experienced issues with their viscous coupler or shifting or AWD issues.

 

I could have sworn that there is no electrical or computer input to the viscous coupler.

 

I'd really have to look at it, but I don't remember seeing any harness up there. The only thing that USED to be there was a temperature sensor for the front diff fluid, but they eliminated that in 09.

I think the guy is an idiot.

It sounds like he is talking about very, very small diameter and measurement changes. Of course it makes sense to check what a tires' overall diameter is instead of what the sidewall reads but in essence based on what he is saying you would run into issues just from the minor changes in tire wear. I'm sure there is at least a little truth to what he is saying but I don't you're going to be burning up the coupler anytime soon.

I can see some of his points being valid here.

 

It is a known fact that tire sizes vs the stated size vary, sometimes a considerable amount. One guys 315 could be wider than another 345. It's where and how they measure that comes into play.

 

Ultimately I don't think tire brand has much to do with it. The only concern I would have is maintaining an equal diameter front to rear. Beyond that, the tires (provided they are a matched set) should react somewhat equally to forces and won't change that much relative to one another.

 

Factory split is 25.47F, 25.96R diameters, that gives you a circumference of 80.00" Front, 81.55" Rear. They might not be perfectly accurate in diameter, but should be consistent to one another)

 

Keep it close to that and everything will be just fine.

 

Look at all the guys with TT cars that change wheels/tires, go to drag radials, run 250mph, and they seem to be holding up.

I think the guy is an idiot.

 

 

I know lots of people who run a 305 on the rear and non Pirelli rubber. I have never heard on an issue with a Gallardo. I highly doubt the minor variances between MPSS and Pirelli's would affect the system. Since it is an Audi system and they have building the variations of this system since the 80's I think they would have to build it to handle with these tolerances in mind. Obviously if you went with a bonkers size rim, you may have an issue.

 

 

Murci's yes, they have an issue with this but even then I think it is when people go up in rim size, not changing to non OEM rubber.

We discussed the measurement differences based on all the variables (static and dynamic) that could be present. He allows that the correct rolling circumference must be a range which would include tire wear - but his point was that they only homologate with the recommended tire - and that if one puts on a different tire (even though correctly sized) the variation in measurements could exceed the acceptable range and if so could cause problems. It's also possible different tires may not exceed the acceptable range but they have no way of knowing without testing. It's possible the MPSS would not be a problem - but he could not say because they haven't tested them.

 

Since we log on the miles (even though we no longer track the car) - the issue would be exaggerated at higher speeds for extended periods. I agree Chip that we won't burn up the coupler quickly - but it would be good to know if we are asking for a problem.

 

I'm not mechanical enough to know whether it's worth rolling the dice on this or whether to say screw it and keep my preferred tire choice.

We discussed the measurement differences based on all the variables (static and dynamic) that could be present. He allows that the correct rolling circumference must be a range which would include tire wear - but his point was that they only homologate with the recommended tire - and that if one puts on a different tire (even though correctly sized) the variation in measurements could exceed the acceptable range and if so could cause problems. It's also possible different tires may not exceed the acceptable range but they have no way of knowing without testing. It's possible the MPSS would not be a problem - but he could not say because they haven't tested them.

 

Since we log on the miles (even though we no longer track the car) - the issue would be exaggerated at higher speeds for extended periods. I agree Chip that we won't burn up the coupler quickly - but it would be good to know if we are asking for a problem.

 

I'm not mechanical enough to know whether it's worth rolling the dice on this or whether to say screw it and keep my preferred tire choice.

 

 

How about this, go to a Pirelli dealer and measure the diameter and circumference for a new tire. Locate a well worn Pirelli and do the same. Then compare to your Michelins, If the Michelins fall within the 2 sets of measurements for the Pirellis you should be fine.

If he's a Lambo corporate guy he has no other choice but to recommend OEM tires. Lambo has a relationship with Pirelli so that's what he has to justify.

Thanks for the info!

 

I have some trust in TireRack.com and when you put in the Gallardo, they give a wide variety of tires in factory sizes. I don't think they would want to recommend tires that would burn up the AWD.

 

Tirerack lists the Corsa diameters as: 25.2f and 26.1r on 8.5/11 wheels - difference of 0.9"

MPSS: 25.5f and 26.0r on 8.5/10.5 wheels - difference of 0.5" which may go down with an 11" rear wheel

Pirelli PZero: 25.4f and 26.1r on 8.5/10.5 - difference of 0.5" and again may go down with 11" rear wheel

 

So even the different tire options that come on the car from the factory have variances. I highly doubt any hardware or software changed between the Superleggera and the regular Gallardo for the tire size difference.

 

I'm going to run the Pilot SS.

We've been dealing with Tire Rack for years. We like them too - they offer a lot of tech support - but they also want to sell product. They did recommend the MPSS for the LP560.

 

I agree - the sizes are so close that common sense would dictate that the MPSS should work.

 

I think the corporate "line" has to be that if they haven't tested it they can't recommend it. I understand that. Having worked in the manufacturing world for 25+ years - the company I worked for would NEVER endorse something that wasn't tested in house because there were too many risks and of course in our litigious society no one wants to open themselves to a lawsuit. Sometimes common sense must prevail. I'm thinking we'll stay with the MPSS but I happen to have a set of PZeroCorsas in the garage (mounted). We will measure the rolling circumference of the fronts v rears and see how different they are. Although they are mounted on Apollos so maybe that negates the test -although the Apollos and Callistos should be the same size.

I had the MPSS on my viper and loved them. I doubt there is any real concern

Thanks Chip. The concern only is around the effect on the viscous coupler (only applicable in AWD).

 

After taking in the comments and applying common sense I'm not sure there's a big risk. Maybe some risk - but it seems minor in the grand scheme. Once we figure out exactly what we're gonna do I'll post.

 

I figure I also need to understand what type of AWD is in my BMW (just bought a 2012 3 series xdrive wagon - love it). We got a set of Michelin Alpin A3s to mount for winter on the 17" OEM rims. My plan was to buy 18" OEM rims and put MPSS on for summer (for handling/looks) but I want to know more about the AWD system before making the jump to 18". I'm pretty sure it's an OEM option in which case it should be fine - but the BMW will become the daily driver especially for my monthly trip to Buffalo so I want to be sure I'm not screwing up my warranty by changing things around.

 

We also have Blizzaks for our CL550 4matic but those stay on the OEM rims. That car gets so few miles (hubby loves it but prefers it stays clean which means it doesn't get driven much) it may not make much of a difference - but still I plan to ask about the AWD system so I understand it better.

 

I enjoy learning about the technical aspects of decisions like tires - but geez this seems more compicated than it should be.

 

She talks cars and has a gun

 

No wonder Cappy is all

Whoever you talked to is correct... there are a few Gallardo owners on the very forum that have had problems caused by non-pirelli tires. (some all wheel drive systems are sensitive.. most lambo techs are the dealers will tell you the same thing)

 

With that said, just replace the tires with Pirellis and move on with your time and energy... to say an exhaust system or something fun for the car!

Whoever you talked to is correct... there are a few Gallardo owners on the very forum that have had problems caused by non-pirelli tires. (some all wheel drive systems are sensitive.. most lambo techs are the dealers will tell you the same thing)

 

With that said, just replace the tires with Pirellis and move on with your time and energy... to say an exhaust system or something fun for the car!

Thanks Andrew. OK - we'll look into this. I wish Pirelli would get off their butts and innovate. The MPSS multi compound is such a superior tire that it's difficult to give up - but I don't want to screw up my AWD. I guess another option is to make it a RWD lambo but I don't really want that.

 

She talks cars and has a gun guns

 

No wonder Cappy is all

corrected ^^

Thanks John - funny

 

She talks cars and has a gun

 

No wonder Cappy is all

The restraining order I have says it is the other way round.

The restraining order I have confirms this

fixed it ^

 

Hi Cappy

 

I've missed you

 

I did some researching today.

 

It looks like most AWD systems want the tires to be the same diameter. I believe we have a viscous setup.

 

In this case the MPSS are actually closer front to rear than the OEM corsas.

 

I think the MPSS are actually better for the car. 98.1% vs. 96.6% differences front to back.

I did some researching today.

 

It looks like most AWD systems want the tires to be the same diameter. I believe we have a viscous setup.

 

In this case the MPSS are actually closer front to rear than the OEM corsas.

 

I think the MPSS are actually better for the car. 98.1% vs. 96.6% differences front to back.

We do have a viscous set up (viscous coupler)

 

The issue is that they (Lambo) have not tested other tires, and the concern was that Lambo does not know how the MPSS will affect the viscous coupler.

 

I see your point - so in theory the MPSS should be fine, but without empirical data I suspect Lambo's official position is that you MUST stay with Pirelli

 

If the AWD system really does like same diameter, the 245 tire would be an even better choice.

 

I'm guessing it is Lambo CYA.

ps. how was the GIRO? Sucks I had to miss it... I always have a great time on them.

ps. how was the GIRO? Sucks I had to miss it... I always have a great time on them.

We'll talk.

Had a good time.

It could use some tweaking.

If you believe this, then you must also believe:

1. This AWD system was designed around these tires (if it is indeed that sensitive)

2. This is the most sensitive system ever installed on a modern production vehicle.

3. Lambo made the risk that this tire would be produced identically and without interruption for 10 years.

 

 

Rediculous.

I am not sure under Euro competition rules that you can insist on one tyre brand.

Now I am no lawyer and I would hope that the Audi lawyers have this covered from my few minutes of tenuous googling but... look at this snapshot.

 

http://www.out-law.com/page-5811

Anti-competitive agreements (Chapter I / Article 101)

 

Both UK and EU competition law prohibit agreements, arrangements and concerted business practices which appreciably prevent, restrict or distort competition (or have the intention of so doing) and which affect trade in the UK or the EU respectively.

Consequences of breach

 

Contravention of Chapter I or Article 101 can have serious consequences for a company:

 

firms engaged in activities which breach these provisions can face fines of up to 10% of group global turnover;

 

So if I use any other brand my warranty is binned because Lambo's agreement with one brand.

But EU law would look at that and could say that the agreement is a concerted business practice and therefore illegal. Now I know there are pitfalls and caveats galore here along with (to my limited knowledge) no actual cases of this being tested against in the automotive arena it is still a grey area.

 

And if we can do it in the UK/EU then you can apply it to the Americas.