tire size help

I've searched through the threads and cannot figure out how the equation works.

 

Here's what I'm currently working with:

F: P-zero - 235/35-19 - height of 25.4"

R: Nitto - 345/25-20 - height of 26.65"

 

 

How do I compare this with the stock tires to not fry a diff?

From an old post;

 

It is a little known fact that there is an optional front tire size on the Murcielago. You can verify this by looking at your VIN plate on the driver’s door (in the jamb area). That being said, Lamborghini has set now the over / under for rolling variances from front to rear (look at it as a ratio so to speak). Here are the overall diameters on the stock 18” tire sizes:

 

Pirelli P-Zero 235/35-18 Overall Diameter - in Inches (24.4764)

Pirelli P-Zero 245/35-18 Overall Diameter - in Inches (24.7520)

Pirelli P-Zero 335/30-18 Overall Diameter - in Inches (25.9134)

 

When installing aftermarket 19” front, 20” rear wheels on the Murcielago, the tire sizes being used are below.

 

Pirelli P-Zero 235/35-19 Overall Diameter - in Inches (25.4764)

Pirelli P-Zero 345/25-20 Overall Diameter - in Inches (26.7913)

 

Now here’s the good part. Below are the variances in height (front to rear) with the stock wheels and tires (also shown with the optional front 235/35-18 tire).

 

235/35-18 with 335/30-18 -1.437008 (this is how much smaller the front tire is vs. the rear – in Inches)

This is now our over figure.

 

245/35-18 with 335/30-18 -1.161417 (this is how much smaller the front tire is

vs. the rear – in Inches)

This is now our under figure.

 

Using these calculations we now know that as long as we stay within these over / under figures with the new aftermarket wheels / tires that we will stay within the factory specification to keep the viscous coupler happy. Here are the variances on the 19” / 20” wheel application.

 

235/35-19 with 345/25-20 -1.314961 (this is how much smaller the front tire is vs. the rear – in Inches)

Within the over / under ,described above!

 

245/35-19 with 345/25-20 -1.039370 (this is how much smaller the front tire is vs. the rear – in Inches)

Not within the over / under described above.

Damage will occur!

 

I hope this helps any of you that are on the fence about getting the 19” / 20” wheels for fear of damaging the viscous coupler on your Murci. I am aware of some Lambo dealers just voiding the warranty “period” because they do not understand this logic and it is easier for them to just say “void” rather than even try to understand this. On a side note, if you do install the incorrect tire size on the vehicle for any period of time, you will damage the coupler. I have seen people install the incorrect front tire size and roll the car for a little as 10 feet and guess what…..into the shop for a new viscous coupler. Be sure you have your calculations straight if you are going to attempt to install aftermarket wheels because it can get costly if the wrong choice of tire / wheel size is made.

 

Thanks!

Yes, 235s in the front will work perfectly, 245s require you to turn TCS off every time.

I've searched through the threads and cannot figure out how the equation works.

 

Here's what I'm currently working with:

F: P-zero - 235/35-19 - height of 25.4"

R: Nitto - 345/25-20 - height of 26.65"

 

 

How do I compare this with the stock tires to not fry a diff?

 

I thought you are running a 2WD setup? If so, you can't fry a diff right?

You going back to AWD for the winter?

 

Not for my car. I'm boring with stock '03 wheels anyways.

From an old post;

 

It is a little known fact that there is an optional front tire size on the Murcielago. You can verify this by looking at your VIN plate on the driver’s door (in the jamb area). That being said, Lamborghini has set now the over / under for rolling variances from front to rear (look at it as a ratio so to speak). Here are the overall diameters on the stock 18” tire sizes:

 

Pirelli P-Zero 235/35-18 Overall Diameter - in Inches (24.4764)

Pirelli P-Zero 245/35-18 Overall Diameter - in Inches (24.7520)

Pirelli P-Zero 335/30-18 Overall Diameter - in Inches (25.9134)

 

When installing aftermarket 19” front, 20” rear wheels on the Murcielago, the tire sizes being used are below.

 

Pirelli P-Zero 235/35-19 Overall Diameter - in Inches (25.4764)

Pirelli P-Zero 345/25-20 Overall Diameter - in Inches (26.7913)

 

Now here’s the good part. Below are the variances in height (front to rear) with the stock wheels and tires (also shown with the optional front 235/35-18 tire).

 

235/35-18 with 335/30-18 -1.437008 (this is how much smaller the front tire is vs. the rear – in Inches)

This is now our over figure.

 

245/35-18 with 335/30-18 -1.161417 (this is how much smaller the front tire is

vs. the rear – in Inches)

This is now our under figure.

 

Using these calculations we now know that as long as we stay within these over / under figures with the new aftermarket wheels / tires that we will stay within the factory specification to keep the viscous coupler happy. Here are the variances on the 19” / 20” wheel application.

 

235/35-19 with 345/25-20 -1.314961 (this is how much smaller the front tire is vs. the rear – in Inches)

Within the over / under ,described above!

 

245/35-19 with 345/25-20 -1.039370 (this is how much smaller the front tire is vs. the rear – in Inches)

Not within the over / under described above.

Damage will occur!

 

I hope this helps any of you that are on the fence about getting the 19” / 20” wheels for fear of damaging the viscous coupler on your Murci. I am aware of some Lambo dealers just voiding the warranty “period” because they do not understand this logic and it is easier for them to just say “void” rather than even try to understand this. On a side note, if you do install the incorrect tire size on the vehicle for any period of time, you will damage the coupler. I have seen people install the incorrect front tire size and roll the car for a little as 10 feet and guess what…..into the shop for a new viscous coupler. Be sure you have your calculations straight if you are going to attempt to install aftermarket wheels because it can get costly if the wrong choice of tire / wheel size is made.

 

Thanks for the great info. I was always under the impression that it's the ratio between the diamters of the front tires vs. the rear tires that we need to pay attention to as opposed to the absolute difference in height.

 

For me I've gone 19" front & rear such that I can go to the extent of matching the original stock diameters:

 

245/30/19: 24.79" in diameters vs 24.75" stock

355/25/19: 25.99" in diameters vs 25.91" stock

Height difference would be 1.20" vs 1.16" stock (under figure)

Ratio rear/front would be 104.84% vs 104.69" stock

 

Trouble is finding that 245/30/19 front is nearly impossible!

 

 

Not for my car. I'm boring with stock '03 wheels anyways.

 

I have new replica Hermera wheels. PM me if-interested.

From an old post;

 

It is a little known fact that there is an optional front tire size on the Murcielago. You can verify this by looking at your VIN plate on the driver’s door (in the jamb area). That being said, Lamborghini has set now the over / under for rolling variances from front to rear (look at it as a ratio so to speak). Here are the overall diameters on the stock 18” tire sizes:

 

Pirelli P-Zero 235/35-18 Overall Diameter - in Inches (24.4764)

Pirelli P-Zero 245/35-18 Overall Diameter - in Inches (24.7520)

Pirelli P-Zero 335/30-18 Overall Diameter - in Inches (25.9134)

 

When installing aftermarket 19” front, 20” rear wheels on the Murcielago, the tire sizes being used are below.

 

Pirelli P-Zero 235/35-19 Overall Diameter - in Inches (25.4764)

Pirelli P-Zero 345/25-20 Overall Diameter - in Inches (26.7913)

 

Now here’s the good part. Below are the variances in height (front to rear) with the stock wheels and tires (also shown with the optional front 235/35-18 tire).

 

235/35-18 with 335/30-18 -1.437008 (this is how much smaller the front tire is vs. the rear – in Inches)

This is now our over figure.

 

245/35-18 with 335/30-18 -1.161417 (this is how much smaller the front tire is

vs. the rear – in Inches)

This is now our under figure.

 

Using these calculations we now know that as long as we stay within these over / under figures with the new aftermarket wheels / tires that we will stay within the factory specification to keep the viscous coupler happy. Here are the variances on the 19” / 20” wheel application.

 

235/35-19 with 345/25-20 -1.314961 (this is how much smaller the front tire is vs. the rear – in Inches)

Within the over / under ,described above!

 

245/35-19 with 345/25-20 -1.039370 (this is how much smaller the front tire is vs. the rear – in Inches)

Not within the over / under described above.

Damage will occur!

 

I hope this helps any of you that are on the fence about getting the 19” / 20” wheels for fear of damaging the viscous coupler on your Murci. I am aware of some Lambo dealers just voiding the warranty “period” because they do not understand this logic and it is easier for them to just say “void” rather than even try to understand this. On a side note, if you do install the incorrect tire size on the vehicle for any period of time, you will damage the coupler. I have seen people install the incorrect front tire size and roll the car for a little as 10 feet and guess what…..into the shop for a new viscous coupler. Be sure you have your calculations straight if you are going to attempt to install aftermarket wheels because it can get costly if the wrong choice of tire / wheel size is made.

 

Just read from the other thread that there are variances between tires from different manufacturers? How do we account for these difference then?

Actually measure the size of the tire. Tire Rack has the true dimensions on their site.

Looking at the rationale above 235/30 20 and 345/35/20 would be under the range that would be safe. Its Nitto's on their website state 25.71 and 26.65= -.94 . But owner says never had TCS problems.

hmm what to do.

I would change the tires or go 2WD.

Sorry to bring this from the dead.

But I've just ordered a set of 19/20 wheels.

I'll run 345/25 Pirelli rears but the front should I run 245/30 or 255/30 on 8.5" rim.

 

Thanks LP

Sorry to bring this from the dead.

But I've just ordered a set of 19/20 wheels.

I'll run 345/25 Pirelli rears but the front should I run 245/30 or 255/30 on 8.5" rim.

 

Thanks LP

 

I believe the front should be 235/35/19?

I believe the front should be 235/35/19?

 

You're right, that is the correct size.

 

 

I'm waiting for my 19/20 wheels to arrive and have to buy a set of tires. Are there any other brands that offer those sizes (235/35/19 & 345/25/20) besides Pirelli?

Thanks guys it seems strange to have 35 profile in front and then a 25 rear. Stock is 245/35 18 so naturally going up a size the profile goes down a size .Also isn't 235 skinny on a 8.5" rim. So the 245/30 or 255/30 would play up with the awd system ?

Here in Australia the rears only choices are nittos or Pirelli.

 

Thanks

Read all the posts again and going on tire rack I'll get 235/35 19 they saying can fit 8.5" rim.

 

Thanks again.

You're right, that is the correct size.

 

 

I'm waiting for my 19/20 wheels to arrive and have to buy a set of tires. Are there any other brands that offer those sizes (235/35/19 & 345/25/20) besides Pirelli?

 

This is the exact problem I am currently facing. For 19/20 those sizes from Pirelli are as close as you can get to being AWD safe.

 

Michelin PSS

245/40ZR19

345/30ZR20

 

That combination I believe is also AWD safe... however. The tires are about 2 inches taller than stock (in the rear). Therefore, 8% difference in the speedo.

This is the exact problem I am currently facing. For 19/20 those sizes from Pirelli are as close as you can get to being AWD safe.

 

Michelin PSS

245/40ZR19

345/30ZR20

 

That combination I believe is also AWD safe... however. The tires are about 2 inches taller than stock (in the rear). Therefore, 8% difference in the speedo.

 

245/40 will rub in the front against the bumper... I had 245/35/19 PSS tires and had to swap them out for 235/30 (Michelin doesn't carry a 235/35/19... Also I've heard 345/30/20 will rub in the back. Has anyone been successful with 345/30/20 PSS in the rear?

what brand tires are you running?

245/40 will rub in the front against the bumper... I had 245/35/19 PSS tires and had to swap them out for 235/30 (Michelin doesn't carry a 235/35/19... Also I've heard 345/30/20 will rub in the back. Has anyone been successful with 345/30/20 PSS in the rear?

 

 

345/30/20 will NOTTTTTTT WORK boys

 

Ask me how I know

 

Physically they fit (barely, in STATIC FORM), but Jesus you literally have to remove fender screws on the rear half of the inner fender well to avoid rubbing, I got them to 'roll' on the car but only about 10 feet from my garage and then had to back it in (I never got to check with active suspension if they would fit (bottoming out in the fender stuff). The MAJOR issue, is to get a MATCHING set of front tires that WONT fry the AWD, physically cannot fit in the fenders IF you plan to ever TURN. (But again, even RWD only guys are LIKELY going to have fitment issues if you ever hit a bump and the wheel/tire package move further up into the rear fender well)

 

Been there, done that. I did come up with a set ass setup eventually to get 'as much tire' under the car as possible, but it required staying with Pirelli's 345 and 265 fronts (which required front a 9.5 inch front rim modification, so again not recommended). I LOVE my handling and driveability now, its night and day from what it was, BUT it came at the expense of a lot of trial and error and lots of $$$$ lost in testing scenarios. lol.

 

Jon

OK found a new combo for PSS!

 

Michelin PSS 225/35ZR19

Michelin PSS ZP 335/25ZR20

 

Pros:

-dead on perfect AWD ratio

-near perfect speedo ratio (102.65mph = 2.65% over)

 

Cons:

-missmatch front and rear

-rear is made for corvette PSS run flats

 

Comments?

 

OK found a new combo for PSS!

 

Michelin PSS 225/35ZR19

Michelin PSS ZP 335/25ZR20

 

Pros:

-dead on perfect AWD ratio

-near perfect speedo ratio (102.65mph = 2.65% over)

 

Cons:

-missmatch front and rear

-rear is made for corvette PSS run flats

 

Comments?

 

Every car I have every bought that has run flats, my first mod is to remove them. So unless they have gotten better in terms of harshness, road noise, and grip, I wouldn't keep looking for other options.

 

 

 

No one wants to listen to me on this, I swear this is the first murcielago to ever run these and it blows my mind why. It works perfect!

 

235/35/19

345/30/19

 

You can't run anything bigger in the back for the awd and up front you will rub if you run anything bigger.