Tire debate

Well, after spending much time going back and forth with another forum member elsewhere, i want to make sure i'm right.

http://www.polkaudio.com/forums/showthread.php?t=94644

Car in question is a 1999 Mustang GT with the optional 17x8 wheels.

He's on a budget, wants to replace the front two tires, got a good deal on a pair of 225/45-17s in place of the stock 245/45-17s.

Is this the end of the world? Street driven car, no competitions, nothing of the sort.

Concerns brought up were:

It'll blow a bead
It'll bend a rim
Massive bump steer
Speedo reading will be off
Handling with be impacted in a noticeable way
Ride quality will suck
ABS will be compromised
The apocalypse will occur (kidding. kindof.)

My thought is that in a street, DD application, none of those things will apply simply because of a 2.8% decrease in rolling diameter.

Am i the one that's way off base here? I don't want to give out dangerous information, but considering the non-stock combinations i've had on my cars with no ill effects, i can't imagine this being as bad as what's being said, and the numbers seem to be on my side.

not knowing anything about rim size or your friends ability to parallel park, i cant comment on the bead blowing or rim bending from the change, but the bump steer, speedo, and abs concerns should not be an issue. i doubt ride quality will change much. a little stiffer sidewall will make the bumps travel deeper, but less tread to hit oddball items in the road may mean you get less stuff to transfer.

it will however look kind of weenie-ish.

just make sure the other tires are not flawed somehow and it shouldnt matter much from a function point of view.

No ill effects, especially street driven. More understeer if anything.

I recently went from 185/65/14 to 195/65/15 to 175/65/14 (all seasons to crappy snows to good snows) on the ZX2 and in street driving barely notice the difference. Min to max, that's a 2" diameter difference.

I don't think his speedo will be off either being rwd unless it reads off a front wheel speed sensor.

The wheels are stock 17x8s.

cghstang wrote: No ill effects, especially street driven. More understeer if anything. I recently went from 185/65/14 to 195/65/15 to 175/65/14 (all seasons to crappy snows to good snows) on the ZX2 and in street driving barely notice the difference. Min to max, that's a 2" diameter difference. I don't think his speedo will be off either being rwd unless it reads off a front wheel speed sensor.

It doesn't read off a front wheel speed sensor as far as i know, unless it's a freak. I've driven a 99 GT, and when doing a smoky burnout, the speedometer was telling me that i was going somewhere pretty quickly.

Your concerns list is lol-full - makes me glad to see non-auto forums generate so much "useful" advice.

(air quotes added for extra sarcasm)

nderwater wrote: Your concerns list is lol-full - makes me glad to see non-auto forums generate so much useful advice.

I hope there's some sarcasm in there. That thread just makes me glad that this place is here. Read the thread if you want a laugh.

That concern list is certainly not my doing. I would have no concerns about it. According to them, my Celica should have flown out of control and destroyed a couple large cities on the way to a flaming death.

Actually.. all of my cars. Not ONE of them has a perfect OEM rolling diameter. Escort too big. Celica WAY too big. MX6 too small.

ABS is the only issue I see. There are ABS sensors on the rear axle and each front hub. You might ask Angry what the allowable deviation variance is between the two axles.

If it helps I ran 235/45/17's all around on my cobra for awhile (tires that were on it from the stealership I got it from) with no ill effect.

John Brown wrote: ABS is the only issue I see. There are ABS sensors on the rear axle and each front hub. You might ask Angry what the allowable deviation variance is between the two axles.

If he comes in here, then we'll address it. Homeboy in the other thread seems pretty sure that 5% is the acceptable tolerance.

As a rule I prefer to get my brake information from someone who might have worked on the project versus "Homeboy from PolkAudio thread". You have the option to choose otherwise.

John Brown wrote: As a rule I prefer to get my brake information from someone who might have worked on the project versus "Homeboy from PolkAudio thread". You have the option to choose otherwise.

LOL!!! I'm with you, i guess that was just one of the things that he said that sounded reasonable.

That said, i sent the OP in that thread a link to this thread so hopefully he'll get the info he needs without the hilarious E36 M3storm that ensued in there.

Here is the thing, if ALL FOUR tires are the same it doesn't matter one iota. Mixing tire diameters will start messing with things. I will put a narrow assed tire on a car when I am driving in Hawaii, but never in Michigan. It rains, snows and every thing elses way too much.

FYI, the stock front wheels on my 350Z were 225/45R18 on an 18x8 wheel. It is not exactly apples to apples, but that tread size for that wheel is not going to be a big problem.

If it's not being raced, it's just more likely to have curb rash with that setup.

As a Mustang owner with 17x8" rims, I'm actually considering going down to 225s instead of the stock 245s. An 8 inch rim is 203mm wide. "Right" width is usually 120% of the rim width, and 100% is still acceptable. 225s are right at about 111%, which makes them perfectly within the normal range for that width.

I run 225/45/17 tires with my 17x8 wheels on my E46 with no problems at all. Its actually the OEM wheel & tire size.

So no safety issues, just make sure the ABS will be happy.

John Brown wrote: Here is the thing, if ALL FOUR tires are the same it doesn't matter one iota. Mixing tire diameters will start messing with things. I will put a narrow assed tire on a car when I am driving in Hawaii, but never in Michigan. It rains, snows and every thing elses way too much.

OK here I go commenting using only "old wives tales" as my guide.... But isn't that backwards? I have always thought that wider tires perform worse in rain and snow, and are better for dry traction!? Narrower tires cut more through the crap and give better traction in the junk.

scardeal wrote: FYI, the stock front wheels on my 350Z were 225/45R18 on an 18x8 wheel. It is not exactly apples to apples, but that tread size for that wheel is not going to be a big problem. If it's not being raced, it's just more likely to have curb rash with that setup.

Well, the issue is that it'll be 225/45-17 in front, and 245/45-17 in back, and that everyone is telling him that he's going to die or destroy his car.

93celicaGT2 wrote: Well, the issue is that it'll be 225/45-17 in front, and 245/45-17 in back, and that everyone is telling him that he's going to die or destroy his car.

Not in the least. Look at all the guys that are running stagger setups on Mustangs. They're usually running something like a 275/40 out back and a 245/45 up front. They don't die...

ReverendDexter wrote:

93celicaGT2 wrote: Well, the issue is that it'll be 225/45-17 in front, and 245/45-17 in back, and that everyone is telling him that he's going to die or destroy his car.

Not in the least. Look at all the guys that are running stagger setups on Mustangs. They're usually running something like a 275/40 out back and a 245/45 up front. They don't die...

Yeah, that was my thought. Apparently my thought didn't go over too well, though.

Sofa King wrote:

John Brown wrote: Here is the thing, if ALL FOUR tires are the same it doesn't matter one iota. Mixing tire diameters will start messing with things. I will put a narrow assed tire on a car when I am driving in Hawaii, but never in Michigan. It rains, snows and every thing elses way too much.

OK here I go commenting using only "old wives tales" as my guide.... But isn't that backwards? I have always thought that wider tires perform worse in rain and snow, and are better for dry traction!? Narrower tires cut more through the crap and give better traction in the junk.

I believe he is referring to ABS function re: tire diameters...

Sofa King wrote:

John Brown wrote: Here is the thing, if ALL FOUR tires are the same it doesn't matter one iota. Mixing tire diameters will start messing with things. I will put a narrow assed tire on a car when I am driving in Hawaii, but never in Michigan. It rains, snows and every thing elses way too much.

OK here I go commenting using only "old wives tales" as my guide.... But isn't that backwards? I have always thought that wider tires perform worse in rain and snow, and are better for dry traction!? Narrower tires cut more through the crap and give better traction in the junk.

SofaKing, Im with you, studded tires work because they have less area (studs) with same force (weight of car) which increases pressure for each contact point. I use narrower tires on rallycross than autocross. This is why my BFG TA's were spinning to high heavens when they lack tread as opposed to when they have nice new tread blocks in the rain (not to mention siping of water due to tread design)

On topic, 225's will fit and work just fine on 8 inch rims. My staggered setup on the 350Z isnt an issue, with three different sizes 'tested' over the years. ABS won't be a problem. Besides if it does act up, wouldn't this be a good lesson in how too much frugality can be a liability.

Enjoy, Eric G

Whether or not they fit isn't the question.

They might not die, but this could happen.

Sofa King wrote:

John Brown wrote: Here is the thing, if ALL FOUR tires are the same it doesn't matter one iota. Mixing tire diameters will start messing with things. I will put a narrow assed tire on a car when I am driving in Hawaii, but never in Michigan. It rains, snows and every thing elses way too much.

OK here I go commenting using only "old wives tales" as my guide.... But isn't that backwards? I have always thought that wider tires perform worse in rain and snow, and are better for dry traction!? Narrower tires cut more through the crap and give better traction in the junk.

I am not worried about width, I am concerned about the ABS reading X-revolutions on the front wheels and X-5% on the rear wheels and screwing with my bias or braking action when I actually need or do not need it.

And again I am only concerned if that number is outside of an acceptable range for the ABS system.