A general tire size question - 986 Forum - The Community for Porsche Boxster & Cayman Owners

ekam · 08-08-2013, 04:24 AM

imsjack · 08-08-2013, 05:29 AM

Quote:

Originally Posted by ekam

ekam, I'm not looking for a tire size calculator, either you didn't read the question, or didn't understand it. I searched tire rack and google last night trying to find out if the difference in size will allow me to mount these tires safely before I posted. Some say it can be done, other say it can't.

Has anyone here changed the aspect ratio of their tire? I'm not looking for a tire size calculator, I'm looking for someone who has done it, and their experience with changing it. I realize OEM size would be best, but these tires are 730bucks - if it's safe to change the ratio by 5 (or not) I'd like to hear from you.

stephen wilson · 08-08-2013, 08:20 AM

With that size, I assume it's not for a Boxster? They will be 1" smaller in diameter, which is a fairly large change, especially if the car has stability control. It may be within the safe range for ABS function though? I thought up to 5% Dia. change was OK for ABS, and you would be at around 3.2% change in diameter? Don't take that as Gospel though!

The 55 is the aspect ratio is explained in spinnaker's link. ( the tires section height is 55% of the section width of 225mm )

I installed a slightly wider, and taller tire on the front of my '06 ( 235 to 245 ), and it is right on the edge for my PSM. If I increase the front tire pressure a few Psi, the "traction control" starts kicking in.

imsjack · 08-08-2013, 08:50 AM

Quote:

Originally Posted by stephen wilson

With that size, I assume it's not for a Boxster? They will be 1" smaller in diameter, which is a fairly large change, especially if the car has stability control. It may be within the safe range for ABS function though? I thought up to 5% Dia. change was OK for ABS, and you would be at around 3.2% change in diameter? Don't take that as Gospel though!

The 55 is the aspect ratio explained in spinnaker's link. ( the tires section height is 55% of the section width of 225mm )

I installed a slightly wider, and taller tire on the front of my '06 ( 235 to 245 ), and it is right on the sdge for my PSM. If I increase the front tire pressure a few Psi, the "traction control" starts kicking in.

thanks, stephen. that was one of my biggest concerns the stability control. I've driven a car with the wrong tire sizes (wrong diameter) and the abs was setting itself off at random (very unsafe). Seems like such a small number, but I'd hate to mess with being safe.