Help on Tires

KrazyMofo24

My car has P245/45-17 tires, it's for a 99 mustang gt. A friend gave me two tires that are P225/45-17. I need to replace my front tires would they be ok to use for the fronts?

treitz3

Not recommended at all.

Serendipity

I wouldn't.

raidersrule76

nope!!

danger boy

just curious why? to small or what?

TNRabbit

Too small. You want to stay same diameter.

keith allen

I would,because 225 is the width of the tire,not the diameter.It will be just a bit narrower and it may look pretty good.I see older gt's that are hopped up around here with much narrower front tires.My neighbor runs 195's on the front of his,but its a true dragracer.But heres concrete proof that its ok,my wife has a s2000 honda,from the factory it has 215/45/17 frnts and 245/45/17 rears.215=w/45=sidewall height/17=inside diameter.Throw those puppys on,wont hurt a thing,may even handle better for some canyon carving!

mark090852

keith allen wrote: »

I would,because 225 is the width of the tire,not the diameter.It will be just a bit narrower and it may look pretty good.I see older gt's that are hopped up around here with much narrower front tires.My neighbor runs 195's on the front of his,but its a true dragracer.But heres concrete proof that its ok,my wife has a s2000 honda,from the factory it has 215/45/17 frnts and 245/45/17 rears.215=w/45=sidewall height/17=inside diameter.Throw those puppys on,wont hurt a thing,may even handle better for some canyon carving!

You could use them, but, in addition to the 225s being 20mm narrower, the diameter is slightly smaller. 225 is the width of the tire in millimeters and 45 is the sidewall height as a percentage of the width. So a 45 on a 225mm wide tire is a smaller diameter tire than a 45 on a 245 mm wide tire. Your car will sit a little lower in front and the handling will be slightly affected. I doubt you would notice the difference unless you tracked the car.

The Honda example sited above is not concrete proof at all. If those sizes were original equipment tire sizes all that means is the susension was set up to use that size on that model Honda. Your Mustang was designed by Ford to use the 245s front and back. A staggered setup is correct on some cars, and incorrect on some others. Can't compare apples to oranges.

tonyb

Another vote for...no, I wouldn't.

BaggedLancer

For front tires? I don't see why not, especially since the car is RWD. Plenty of racing guys go skinnier up front and fatter in the rear.

danger boy

in my day.. i ran (front) 70's and 60's (rear) series tires.. but that was on a 1972 Camaro.

messiah

The tires will be slightly smaller. 245 - 225 = 20. But the 45 in the equation is the aspect ratio. The tire is 45% as tall as the width. So if it's not as wide, It's not as tall. It won't hurt your car if you choose to run these though. It might skew your speedometer readings some, but not much I would guess. It isn't recommended, but really wont hurt your car.

concealer404

It won't matter. Go for it. Unless you're an active racer, you won't notice.

It won't mess up your speedo, (that's measured at the transmission, not the front tires) it won't noticeably screw up your handling, it won't matter.

The size difference is pretty small, you probably won't be able to tell.

Seriously. You're talking a 2.8% difference. On a street car, who cares?

Everyone saying that you want the same diameter... it's not an AWD car, guys.

treitz3

BaggedLancer wrote: »

For front tires? I don't see why not, especially since the car is RWD. Plenty of racing guys go skinnier up front and fatter in the rear.

While true, that is with different sized rims. The OP, I'm assuming, is staying with the same size rim. That is why it is not recommended.

concealer404

treitz3 wrote: »

While true, that is with different sized rims. The OP, I'm assuming, is staying with the same size rim. That is why it is not recommended.

The rim size doesn't have much to do with it though. If the tire safely fits on the rim, it's fine. I run staggered tire sizes on my car when i'm racing it, but my wheels are all 16x8 +38 offset. I cram 265 width tires on the front, and leave 245s on the back for slightly easier rotation.

I believe the OP is just talking about for a DD. If any of us can notice a big difference in day to day driving, or if the car is suddenly rendered unsafe with the installation of these tires, there's far bigger problems afoot.

treitz3

Oh, it will work alright but you are adding strain to the sidewalls if you mount them on a rim they are not designed to go on. Handling would be affected slightly and tire wear will increase. You would also be subject to greater tire/rim damage if you were to "pop" a curb by accident.

KrazyMofo24

Thanks for the responses, I think I'm leaning towards using them for the fronts. My dad said they should be fine, and my gf's dad also said they'd be ok and they are usually the ones who help me fix the car. I called firestone and the guy said it would be fine also. I found a local place that will replace the other for 80 each which includes installation and everything. So I'll have them replace the back two, and install these two.

concealer404

treitz3 wrote: »

Oh, it will work alright but you are adding strain to the sidewalls if you mount them on a rim they are not designed to go on. Handling would be affected slightly and tire wear will increase. You would also be subject to greater tire/rim damage if you were to "pop" a curb by accident.

True, but that's in extreme circumstances. I can safely mount anything from a 215 to a 265 width on my rims.

I believe the stock width of those rims are either 7.5" or 8". Either of which is perfectly fine with a 225 width tire.

It's not like 225 width tire on those rims is going to give you this ridiculous and dangerous scenario:

Jstas

What's not fine is that the different diameter tire might affect your anti-lock brakes.

concealer404

Jstas wrote: »

What's not fine is that the different diameter tire might affect your anti-lock brakes.

Ah yes, it might kick in 2.8% earlier than before. What a catastrophe. Oh the humanity.

Jstas

concealer404 wrote: »

Ah yes, it might kick in 2.8% earlier than before. What a catastrophe. Oh the humanity.

No smartass, with a shorter tire, the wheel speed changes and the cog that times the sensor for the anti-lock brakes may not be in an acceptable range. The anti-lock computer goes in to a fault mode and puts brake pressure on the by-pass valve and over-boosts the vacuum pressure. Not only can it get harder to stop the car due to a spongy pedal but the anti-lock brakes will not function properly and they can actually perform worse than non-anti-lock brakes. Since 75% of your braking power comes from the front brakes, that wouldn't be an ideal situation. It's not just about when the anti-lock system starts pulsing. And honestly, it wouldn't be "2.8% sooner", it'd be "2.8%" later.

But, you're an expert so you knew that already, didn't you? :rolleyes:

concealer404

Jstas wrote: »

No smartass, with a shorter tire, the wheel speed changes and the cog that times the sensor for the anti-lock brakes may not be in an acceptable range. The anti-lock computer goes in to a fault mode and puts brake pressure on the by-pass valve and over-boosts the vacuum pressure. Not only can it get harder to stop the car due to a spongy pedal but the anti-lock brakes will not function properly and they can actually perform worse than non-anti-lock brakes. Since 75% of your braking power comes from the front brakes, that wouldn't be an ideal situation. It's not just about when the anti-lock system starts pulsing. And honestly, it wouldn't be "2.8% sooner", it'd be "2.8%" later.

But, you're an expert so you knew that already, didn't you? :rolleyes:

You're incorrect. It would be sooner rather than later. A smaller diameter tire is easier and quicker to lock up than a larger diameter tire. Anti-lock systems intrude into the braking process when lockup is sensed.

I'm not real sure where you're getting that the same braking system will lock a larger diameter package faster than a smaller diameter package, that's defying basic laws of physics.



Look. What you're all saying is that it's a terrible idea to put any non-stock size tire on a car, or alter the rolling diameter in any way. If you truly believe that, then i suggest that none of you ever put aftermarket wheels on your cars. A half inch wider wheel, even with the same size tire on it, will have a different diameter. For that matter, the rolling diameter and contact patch will be different between different brands and models of tire, even if it's on the same wheel. (On a 16x8 Enkei RP01, Falken Azeni RT615s had a smaller contact patch and a larger rolling diameter than Hankook Ventus RS2s in 245/45-16 size on my car.)

Interesting bit of trivia: There was over a 2% variance in rolling diameter on the 99 Mustang GT from factory, depending on whether or not you got it with 16" wheels or 17" wheels. I'm pretty sure that they didn't design or calibrate the ABS system differently depending on what wheels it was going to have from factory.

It could be had with 245/45-17s or 225/55-16s.

Jstas

It's not about tire weight. It's about the ABS sensor sensing the speed of the tire.

But, you're the "expert" so go ahead and do what you like.

BTW, it's not about wheel size, it's about overall wheel diameter. Including the tire. The OP is not changing wheels size, he's changing overall tire diameter. That will change many thing in how the ABS responds as well as braking and steering responsiveness.

You are right though, a lighter tire will lock up faster. It's not about wheel weight though. It's about ABS sensors. The ABS doesn't necessarily engage when a shorter tire changes the wheel speed which in turn changes the sensor ring speed.

As far as your 2% variance, that is within allowable specs. It's +/- 5%. Then again, 5% in a 30" tall tire is an inch and a half. In a 25" tall tire, an inch and a quarter is 5%.

Here, some math (with work shown!) for the stupid kid in the corner with the cocky attitude and big mouth.

Overall Tire Diameter for a 245/45R17 tire: 25.68"

OTD = {(2 x 245 x 45) / 2540} + 17

Overall Tire Diameter for a 225/45R17 tire: 24.97"

OTD = {(2 x 225 x 45) / 2540} + 17

Difference between the two diameters: .71"

That is within spec and shouldn't cause much of a problem. However, cornering and braking will suffer because not only is the 225/45R17 shorter, it is narrower with a narrower section width as well. The sidewalls on the stock wheel will be smaller and stiffer. The ride will be more harsh and more susceptible to bump steer. You also run a greater risk of popping the bead over just a simple pothole or when tagging a curb in something as simple as parking. It's all gonna look pretty stupid too. You can do it if you want to save a buck but I'd sooner put the tires up on cragslist than throw them on the Mustang but that's me.

concealer404

Jstas wrote: »

It's not about tire weight. It's about the ABS sensor sensing the speed of the tire.

Ok....? No argument there, that's exactly what i said.

BTW, it's not about wheel size, it's about overall wheel diameter. Including the tire. The OP is not changing wheels size, he's changing overall tire diameter. That will change many thing in how the ABS responds as well as braking and steering responsiveness.

Ok? Again, exactly what i've said.

You are right though, a lighter tire will lock up faster. It's not about wheel weight though. It's about ABS sensors. The ABS doesn't necessarily engage when a shorter tire changes the wheel speed which in turn changes the sensor ring speed.

You just said it's not about weight. I'm talking about a shorter tire locking up faster, regardless of ABS kicks in. It's simple simple physics.

As far as your 2% variance, that is within allowable specs. It's +/- 5%. Then again, 5% in a 30" tall tire is an inch and a half. In a 25" tall tire, an inch and a quarter is 5%.

Then why are you arguing, since that's exactly what i pointed out?

Here, some math (with work shown!) for the stupid kid in the corner with the cocky attitude and big mouth.

Overall Tire Diameter for a 245/45R17 tire: 25.68"

OTD = {(2 x 245 x 45) / 2540} + 17

Overall Tire Diameter for a 225/45R17 tire: 24.97"

OTD = {(2 x 225 x 45) / 2540} + 17

Difference between the two diameters: .71"

Congratulations! You just redid my work. Did you think i just pulled the 2.8% different out of my ****? Sorry Charlie, not the case.

That is within spec and shouldn't cause much of a problem.

So what exactly are you arguing again, since that's exactly what i said, as well.

However, cornering and braking will suffer because not only is the 225/45R17 shorter, it is narrower with a narrower section width as well. The sidewalls on the stock wheel will be smaller and stiffer. The ride will be more harsh and more susceptible to bump steer. You also run a greater risk of popping the bead over just a simple pothole or when tagging a curb in something as simple as parking. It's all gonna look pretty stupid too. You can do it if you want to save a buck but I'd sooner put the tires up on cragslist than throw them on the Mustang but that's me.

Seriously? He's not tracking the car. Again, we're talking a 2.8% reduction in rolling diameter. On a street driven, therefor probably pretty stock and squishy-cushy suspension, is your **** going to notice that half inch shorter sidewall? Absolutely not. Popping a bead? Give me a break. It's a 45 series tire. It's not like it's a rubberband on a 22 inch rim. If you want to get technical, it's 2.8% more susceptible to popping a bead. If it's gonna pop, it's pretty likely it would have popped with the stock tire size on there, anyways.



John, really. You're so caught up in trying to argue and to "prove the punk kid wrong" that you didn't even read what i said, and ended up just reiterating everything i've said, as a rebuttal? What is wrong with you?

I freely admit that i've probably been wrong about many things in my life, i'm sure more things than you, since you seem to have a wealth of knowledge about everything. But just because you know everything, doesn't mean that i don't have some knowledge in SOME field in this world. This happens to be one of them. I race my car legally. I run a VERY non-stock tire size, and my wheel/tire package was put together after months of research to figure out how to get the most tire under the car while maintaining a safe clearance from my very non-stock suspension components. I'm well aware of every effect non-stock tires sizes have, and to what extents the changes will happen.

KrazyMofo24

Well I am getting second thoughts about it now. I have 3 bad tires, and the other one will be worn out pretty soon. As long as this place still has those two tires, I'll get two for replaced tomorrow. I can see if they'll buy the tires from me. $160 for two new tires including installation and balancing is by far the cheapest. Discount tires charges $252 to install two of their cheapest tires. I did a search on craigslist yesterday and didn't find any my size. I'll keep a look out, but will probably will have to wait a couple weeks to replace the other if I don't use the P225s.


Edit: I just read concealer's response and he sounds like he has knowledge in tires. I'll decide tomorrow...I'll probably go ahead and install and use them, and replace them with P245's in about a month.

mhmacw

hey krazy....in no way shape or form am i going to get into this discussion haha. i spent 10 yrs in the tire and underbody/ exhaust field. if i were you and im not of course but if i were id look for two more of the 225s and put on 4 of the same size. it wont hurt a thing and everybody can calm down as im sure they would agree its the easiest solution to a rather simple problem haha.

concealer404

For the record, i am under no circumstances saying that running mismatched tires on this car is IDEAL. I'm simply saying that in normal street-driven use, you'll be hard pressed to notice any difference. At all. That's it.

KrazyMofo24

mhmacw wrote: »

hey krazy....in no way shape or form am i going to get into this discussion haha. i spent 10 yrs in the tire and underbody/ exhaust field. if i were you and im not of course but if i were id look for two more of the 225s and put on 4 of the same size. it wont hurt a thing and everybody can calm down as im sure they would agree its the easiest solution to a rather simple problem haha.

I could do that, I can check that place to see if they have two of those. I was going to buy two tires anyways.

concealer404

Check Tire Rack for tires, and then have the tires installed at a Tires Plus or something. Tires Plus usually charges about $10 per corner to mount and balance a tire. I think DiscountTire is **** you.

Jstas

concealer404 wrote: »

I freely admit that i've probably been wrong about many things in my life, i'm sure more things than you, since you seem to have a wealth of knowledge about everything. But just because you know everything, doesn't mean that i don't have some knowledge in SOME field in this world. This happens to be one of them. I race my car legally. I run a VERY non-stock tire size, and my wheel/tire package was put together after months of research to figure out how to get the most tire under the car while maintaining a safe clearance from my very non-stock suspension components. I'm well aware of every effect non-stock tires sizes have, and to what extents the changes will happen.

Junior, listen up. I'm not hell bent on proving you wrong. You ARE wrong. I know tires. I sold them for 6 years. I know ABS braking systems. I've been servicing cars for about a decade. I just recently gave up being an automotive technician. I have 10 years under my belt of professional experience. On top of that I have ooodles of actual racing experience with actual race cars. Not street cars with "legal racing" whatever that is. I know what wheel weight does to the unsprung weight, steering response and braking performance. I know what the difference between standard, non-ABS braking systems and ABS braking systems are. I've serviced brakes on more vehicles than I can remember. That's more than I can say for you judging by your responses.

I already gave reasons why you were wrong. We did not say the same things. But obviously, you are an "expert" so I'll let you go along believing you have some kind of knowledge that you didn't get from tirerack.com and keep **** up people's cars with bad advice.



KrazyMofo24, you want to put those tires on, go ahead. There have been multiple reasons in this thread stating why it's a bad idea. Some good, some very good and still some with real world experience (not just mine) and actual mathematics to back up why it's not the best idea. But it's your car, your money and your safety. Do with it as you wish. You obviously only want to hear what you want to hear, not what is true. Evidence by the fact that you believe a kid in Indiana cut and pasting from tirerack.com has "some knowledge of tires".

I'm done here. I thought there was enough evidence presented on why to not do it without having to chime in. But, guess not.

mhmacw

mismatched tires are in my opinion special application only i.e. thaa all abudget will allow or you want different ratios for off road performance... the list is endless. also if you are buying two new ones as well be sure the aggression is similar so the car doesnt push in corners. very dangerous on icy roads. good luck and drive safe ok. all the best ,dan