is this a correct 19/20 setup for a 2009 LP640?

There is a Murci LP640 that I am interested in but I am trying to avoid the damage that wrong size/ratio can cause. This is a 2009 lp640 with CCB and has the following set up (AWD)

 

Front : 235/35/zr19 P Zeros

Rear: 325/25/zr20 P zeros

 

He has been running those for the last 1500 miles (2-3 years). Are these tires/wheels combo with in specs? Or am I possibly looking at diff/coupler issues?

 

I think couple of the tires were manufactured back in 2012 so it is time for them to be changed.

 

I am on the tirerack website and it only shows tire size with one decimal number (not sure if it is even rounded up or down). When I ran 235/35/19, it was 25.4 and 325/25/20 is 26.5. Based on another post (which I will copy and paste) I just need to be over 1.161417 but based on tirerack limited number I am at 1.1 which I am not sure if it is 1.11xx or 1.19xx etc. My guess is that is less than 1.15 but I just want to be sure. Is there another website that will give me the exact number for these tires? Lets say if it is between 1.10 and 1.14, will it be considered "close enough" to 1.16xx to where it will not really cause any damage? based on the search with in these forums, it seems that most people are using 235/35/19 with 345/25/20.

 

Thanks for your help

 

 

*******************************************************

 

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!

There is a Murci LP640 that I am interested in but I am trying to avoid the damage that wrong size/ratio can cause. This is a 2009 lp640 with CCB and has the following set up (AWD)

 

Front : 235/35/zr19 P Zeros

Rear: 325/25/zr20 P zeros

 

He has been running those for the last 1500 miles (2-3 years). Are these tires/wheels combo with in specs? Or am I possibly looking at diff/coupler issues?

 

I think couple of the tires were manufactured back in 2012 so it is time for them to be changed.

 

I am on the tirerack website and it only shows tire size with one decimal number (not sure if it is even rounded up or down). When I ran 235/35/19, it was 25.4 and 325/25/20 is 26.5. Based on another post (which I will copy and paste) I just need to be over 1.161417 but based on tirerack limited number I am at 1.1 which I am not sure if it is 1.11xx or 1.19xx etc. My guess is that is less than 1.15 but I just want to be sure. Is there another website that will give me the exact number for these tires? Lets say if it is between 1.10 and 1.14, will it be considered "close enough" to 1.16xx to where it will not really cause any damage? based on the search with in these forums, it seems that most people are using 235/35/19 with 345/25/20.

 

Thanks for your help

 

 

*******************************************************

 

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!

 

Indeed based on the 'conventional' wisdom 235/35/19 + 345/25/20 seems to be the right combo but of course, you'll have to pay attention to the actual tire dimension.

 

Having said that, I've heard various people on this forum, running tires combo OUTSIDE these tolerance boundary and they seem ok. Coupled w/ the fact that tire aging will lead to overall diameter shrinking, I do think the tolerance level is probably wider than we think. It's a real shame that we never got any official word on this.

 

But then again, since you're thinking of getting new tires anyway, why not go for the popular combo of 235/35/19 + 345/25/20? Afterall the original width of the rear tires was 335 (335/30/18)...

 

I have 19/20 HRE's and we found a 255/30 didn't rub but a 235/35 did. Not sure if that fits within the stock specs but I'm rwd so it didn't really matter for me.

 

 

Any update in regards to this top as i am running different sizes. 

 

 

Any update in regards to this topic as i am running different sizes. 

225/30/R19 - Front 

325/25/R20 - Rear 

If the tires don't work, you can always go 2WD. 

Find the actual size of the tire diameter and use this equation to see if it falls within the stock parameters

http://lambodiy.blogspot.com/p/correct-tire-size.html