Eatmydust

Hey guys,

Been a while since I did anything to my car but in need of tire change all around.

Did a search all over the place about putting a 255/55/17 tire all around on a 1.25" inch lowered car all around. (Found tires at that size that I like) Search came up only with information on 255/50/17 so I am wondering if there was a reason 255/55/17 was avoided?

Wasn't able to find out anything about fitment and looks.. does anyone have an idea?

Ministang

The biggest reasons I can think of for not going with a 255/55-17 is the overall height and sidewall height. Overall height will cause speedometer/odometer error as they are a good bit taller than stock (more than an inch taller), and the extra sidewall height vs stock will make the car handle even mushier than stock. What are the tires in question that you like so much? Most tires in that size are truck tires.

Eatmydust

A local shop here in the bay area offered me a set of Federal 595. Read some things online about them being not bad at all, plus they looked pretty nice.

My concerns were rubbing in the front, however another member had a lowered (-1.5") car with 20 inch wheels without rubbing so I figured it could be ok to run what I have.

Is there a way to find out how much the speedo will be off?

Ministang

Doing some quick math, it looks like the 255/55-17's will be 4-5% off, your speedometer will read 4-5% slower than you are actually going. In other words, if your speedometer says you are going 75 mph, you will likely be going 78-79 mph. Could mean a ticket if you usually go a few mph over the speed limit anyways and aren't always aware of the difference. If you have a tuner, I believe you can change the tire size parameters to correct the diameter difference though.

Eatmydust

Hmm that's definitely something I have to consider. I do have a tuner...

I guess tires are just confusing to me.. my stock tires are 235/55/17 and I thought since the "55" is the same that the diameter is the same. Obviously, , I don't know what I am doing.

Ministang

Yeah, tire sizes can be confusing, since each number in a tire size represents something different. The first is tire width in millimeters, the last is wheel height in inches, and the middle number is a ratio representing sidewall height, and since it is a ratio, the larger the 1st number (tire width), the taller the sidewall height would be.

To keep the same height while going wider with a 17" S197 Mustang wheel, you'd go from a 235/55 to a 255/50 size tire.

Agent MOO

I'm lazy so I like to use a tire size calculator from the internet. It will help you get an idea of the diameter differences for the options available without having to convert units and do percentages.

http://www.1010tires.com/tiresizecalculator.asp

muscledom

The first two numbers for tire size are measurements in mm... Spedo will be off a hair, you probably won't notice the difference. It's only gonna be like a half inch difference. I'd get whatevers cheaper

muscledom

Sorry for the multiple posts... There's a calculator from like discounttire or one of those. Just google it. It's only gonna be off like a couple mph at like 75 anyway. I had the same questions when I got a set of wheels for a Charger I had. You won't throw codes or anything. Youll just be going like 78 when you're spedo reads 75.