Rear tyre size

[max76]

Hi guys,
Here in Italy we (zr1 owners) have a problem with the rear size tyre.
We have an only brand who produce the 315/35/17 tyre.
Me and some other guys, zr1owners, want put on the rear the 335/35/17, it's a less rare tyre and wr can choose Michelin or Pirelli.
But we have an other problem, we need a "paper" where GM tell us that there are not technical problem using the bigger tyre (always on the original rim).
Someone of you know how I can contact GM for have this documents?
Thanks to everyone
Max

[ssrszz4]

Amazon don't ship to Italy?

Sent from my XT1585 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[XfireZ51]

Max,

I'm not sure an OEM would produce documentation on mounting anything but their recommended size tire.

[Kevin]

especially for a car that hasn't been produced since 95 and that gm seems to want to forget exists.

[max76]

Hi guys,
Is not a problem of shipment...the problem is that here in Italy we cannot put on the car a different tyre misure if it's not written on the car technical paper named "libretto". But for this modify we need a technical relation by Gm...I hope that I explain correctly the problem...

[efnfast]

I would think getting that document from GM would be harder than getting our dyno sheets. GM won't put their name on it, unless it's been engineered and tested.

[PhillipsLT5]

Tire rack or discount tire websites would show fitments

[XfireZ51]

What Max is saying is that in Italy, no one will sell or mount tire sizes on his wheels that do not conform w OEM spec. So in order to do so, he needs the owners manual or some other official GM document showing that the 335s can be fitted to the OEM wheel and are sanctioned by GM.
I would be very surprised if anything like that exists.

[G-Sting]

I would think getting that document from GM would be harder than getting our dyno sheets. GM won't put their name on it, unless it's been engineered and tested.

Someone here could make something up for our friends in Italy? :-D

We've got talent, I'm sure.

cheers,
G

[Ccmano]

Agreed, no manufacturer will produce a "one off" letter like this. Not for a current production car let alone one that has been out of production for 22 yrs. Believe me I know. I've worked corporately for Mercedes, Hyundai and Mitsubishi.

If the OP wanted to sidestep the law in Italy, I offer this convoluted solution. Have the tires removed from the wheels in Italy, ship the wheels to a country where this is not an issue. Have tires mounted there and ship back. Or just buy wheels and tires elsewhere and ship in.

Of course this doesn't save any money as the OP wanted.

Isn't socialism a wonderful thing! You need government approval for everything. It's for your own protection.
H

[ssrszz4]

I guess you could could mount them yourself and take the chance you would ever get caught.

Sent from my XT1585 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[XfireZ51]

Hans,

U bring up a good point.

Max,

Is this an EU requirement or just one of those "wonderfully characteristic" Italian
Quirks?

[S.hafsmo]

It's much the same in Norway. Can't run any other tire option then what the car manufacturer will certify for the car. Never been pulled over for it though.

[ssrszz4]

I wondered which is worse those kind of regulations or dealing with Trump

Sent from my XT1585 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[S.hafsmo]

It's not really that much of an issue. A rigid system is necessary to avoid people driving around with home-made unsafe crap. They rarely care about minor deviations from stock.

[efnfast]

The new thing around here is tires that are far too small for the rims. Looks stupid and looks unsafe.

[Kevin]

let's keep politics out of this. edit posts as needed or I'm going to do it.

[efnfast]

Done Kevin, sorry. I debated, but couldn't resist.

[Ronstar]

Shouldn't a company that manufactures the tires or one that specializes in tire and wheel installations be qualified to determine if a certain tire is acceptable with a certain rim??

[S.hafsmo]

Shouldn't a company that manufactures the tires or one that specializes in tire and wheel installations be qualified to determine if a certain tire is acceptable with a certain rim??

What fits on a rim does not necessary fit inside a wheel well.
https://www.2carpros.com/images/question_images/182953/large.jpg

[Ronstar]

What fits on a rim does not necessary fit inside a wheel well.
https://www.2carpros.com/images/question_images/182953/large.jpg

The same principal should hold true for vehicle application. I have somehow man aged to put non-oem size tires on several cars and I'm no rocket scientist. Certainty a company that specializes in wheels and tires should be qualified to make that determination.

[S.hafsmo]

Certain approved independent laboratories (i.e. Tüv in Germany) can confirm fitment of a set of rims/tires for specific car models. Some wheel manufacturers does go through with these certifications, and those wheels can then be approved on your car.

Fitting non-oem sizes on cars and observing that they'll rotate isn't hard, no. But confirming that they still keep their distance to surrounding parts while at full opposite lock around the track (or evading a donkey crossing the street) is not as easy.

It might seem odd to have such rules to protect the driver. Just like it's odd that there has to be a law against driving without your seat belt, as one would imagine using such a safety feature would be obvious, but it's not.

If all stuck to minor changes it probably wouldn't be an issue, but there's always that one guy.
https://i.ytimg.com/vi/QsvXX218gbk/maxresdefault.jpg

Are there really no restrictions in the US?

[BigJohn]

I wondered which is worse those kind of regulations or dealing with Trump

Sent from my XT1585 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)


So what kind of deals are you making with President Trump!!!

[XfireZ51]

So what kind of deals are you making with President Trump!!!

Only the greatest and best deals ever. And so easily done. You'll get sick from all these great deals!