Need Education: Tire Aspect Ratio & Choices
01-02-2007 | 08:42 PM
#1
Thread Starter
Race Director
Joined: Jun 2003
Posts: 15,121
Likes: 334
From: Los Altos, CA
Need Education: Tire Aspect Ratio & Choices
Hi,
I need some education on tires.
I am looking at a base Cayman and the OEM front is 205/55/17.
Tire Rack shows 3 different tires for summer (I live in the SF area so winter tire is not in consideration).
Searching 205/50/17, the choices rise to 44 (summer tires only). Searching 205/45/17, the choices show 15 (again summer tires only).
I know the aspect ratio denotes the height of the sidewall (for a given tire width). Using a shorter tire (say 50 or 45) will yield slightly inaccurate speedo and odo readings (tire circumference not true to meter calibrations), and also slight increase in chances of wheel damage (wheel is closer to pavement in case I hit a pot hole).
But in reality, will using a 50 aspect ratio versus 55 OEM make that much of a difference, and or screw up alignmnet/performance aspects that I had not thought about? Obviously if the difference is insignificant, I would always opt for more choices.
Thanks again for the education.
CP
I need some education on tires.
I am looking at a base Cayman and the OEM front is 205/55/17.
Tire Rack shows 3 different tires for summer (I live in the SF area so winter tire is not in consideration).
Searching 205/50/17, the choices rise to 44 (summer tires only). Searching 205/45/17, the choices show 15 (again summer tires only).
I know the aspect ratio denotes the height of the sidewall (for a given tire width). Using a shorter tire (say 50 or 45) will yield slightly inaccurate speedo and odo readings (tire circumference not true to meter calibrations), and also slight increase in chances of wheel damage (wheel is closer to pavement in case I hit a pot hole).
But in reality, will using a 50 aspect ratio versus 55 OEM make that much of a difference, and or screw up alignmnet/performance aspects that I had not thought about? Obviously if the difference is insignificant, I would always opt for more choices.
Thanks again for the education.
CP
01-03-2007 | 01:16 PM
#2
Former Vendor
Joined: Mar 2006
Posts: 2,787
Likes: 12
From: South Bend, IN
If the car in question is not all wheel drive the biggest differences are usually seen at the speedo if the overall diameter differnce is below about 5%. If the car is AWD, your f/r tires need to match.
One thing you are missing as well is load capacity, which is a big deal to us here. Reducing the tire size also reduces the air chamber size unless you go wider to compensate. Reducing air chamber size reduces the tire's ability to hold the car and contents up without having to add more air to make up the difference. That may be more dangerous as your tires won't withstand potholes as well.
Maybe some of your questions can be answered in our tech section:
http://www.tirerack.com/about/techcenter.jsp
Yo of course are always welcome to call me to discuss.
One thing you are missing as well is load capacity, which is a big deal to us here. Reducing the tire size also reduces the air chamber size unless you go wider to compensate. Reducing air chamber size reduces the tire's ability to hold the car and contents up without having to add more air to make up the difference. That may be more dangerous as your tires won't withstand potholes as well.
Maybe some of your questions can be answered in our tech section:
http://www.tirerack.com/about/techcenter.jsp
Yo of course are always welcome to call me to discuss.
01-03-2007 | 01:34 PM
#3
Thread Starter
Race Director
Joined: Jun 2003
Posts: 15,121
Likes: 334
From: Los Altos, CA
Damon,
Car is 2WD. The base Cayman is 2,850 or so lbs with no big cargo capacity, so total gross weight should not be much of an issue.
Good stuff. I will call you later when I have a little more time. I need all the education I can get.
CP
Car is 2WD. The base Cayman is 2,850 or so lbs with no big cargo capacity, so total gross weight should not be much of an issue.
Good stuff. I will call you later when I have a little more time. I need all the education I can get.
CP
01-03-2007 | 01:47 PM
#4
Racer
Joined: Oct 2004
Posts: 499
Likes: 1