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[Randomizer2]

Curious if anyone has a setup with offsets and rim sizes for a tire this size. I'd like to run this size to maximize grip and reduce wheelspin. Also thinking 255's in the front. Is this all possible? What size rim and offset should I use for this, if I can even fit these. Most I see is 255 and 265.

[SKI-R]

https://support.apexraceparts.com/hc...-Fitment-Guide

It’ll require you to read.

[Randomizer2]

Originally Posted by SKI-R

https://support.apexraceparts.com/hc...-Fitment-Guide

It’ll require you to read.

Thank you

[MightyMouseTech]

A stickier 255 will give more grip than a less aggressive 275. The contact patch will be the exact same size if you are running a 225, 245 or 275, if used at the same pressure.

I do wish Michelin made a 275/30/18 MPS4S though.

[tracer bullet]

Originally Posted by MightyMouseTech

The contact patch will be the exact same size if you are running a 225, 245 or 275, if used at the same pressure.

Just agreeing with this fact in case anyone finds it hard to believe. The contact patch will change shape, but generally speaking be the same overall size in square inches. (Wider tire stretches it out, of course, but because the overall size stays the same that patch gets slightly shorter front - rear. Wider tires would be beneficial for sideways motions i.e. hard cornering, skinnier tires are better for gripping during acceleration & braking, i.e. winter).

[Randomizer2]

Originally Posted by MightyMouseTech

A stickier 255 will give more grip than a less aggressive 275. The contact patch will be the exact same size if you are running a 225, 245 or 275, if used at the same pressure.

I do wish Michelin made a 275/30/18 MPS4S though.

Sorry, ya lost me there. Could you explain why the contact patch is the same with all of those sizes? I will be putting it on a 9.5" rim. You say if they are ran at the same pressure, I ask what pressure should those sizes be ran at?

[tracer bullet]

psi = pounds per square inch

Let's say a tire is carrying an 800 pound load, and running at 40 psi...800 / 40 = 20

So you have a 20 square inch contact patch

Make the tire wider, the patch stays the same, and so it gets a little smaller in the front / rear direction

Size to run at = start w/ manufacturer's recommendations and go up or down from there depending on what you want to do and how you want to change how things handle - no 1 size fits all "should" run at

[MightyMouseTech]

Originally Posted by tracer bullet

Just agreeing with this fact in case anyone finds it hard to believe. The contact patch will change shape, but generally speaking be the same overall size in square inches. (Wider tire stretches it out, of course, but because the overall size stays the same that patch gets slightly shorter front - rear. Wider tires would be beneficial for sideways motions i.e. hard cornering, skinnier tires are better for gripping during acceleration & braking, i.e. winter).

Yup. Best acceleration traction on my car was with the 205 winter tires. Could launch it so hard, much better than my summer tires. Scary as fuck going around a corner though.

[PcarDefector]

Originally Posted by MightyMouseTech

A stickier 255 will give more grip than a less aggressive 275. The contact patch will be the exact same size if you are running a 225, 245 or 275, if used at the same pressure.

I do wish Michelin made a 275/30/18 MPS4S though.

I'm curious as to why you like the MPS4S?

Coming from the Porsche world, I'm a little tired of overpriced Michelins Pilots. Used to devour the rears in 10-12k kilometres due to trackdays and too much rear camber. Moved to Kumho PS92 and my pocketbook is much happier.

Probably lost a little time on the track but then I'm not racing my street car. That's what my 135i will be build for if I don't trade the DCT for a stick.

[MightyMouseTech]

Originally Posted by PcarDefector

I'm curious as to why you like the MPS4S?

Coming from the Porsche world, I'm a little tired of overpriced Michelins Pilots. Used to devour the rears in 10-12k kilometres due to trackdays and too much rear camber. Moved to Kumho PS92 and my pocketbook is much happier.

Probably lost a little time on the track but then I'm not racing my street car. That's what my 135i will be build for if I don't trade the DCT for a stick.

My 1er is strictly a weekend travel/road trip, bombing down the B roads, car, no more track days for her. The MP4S is the absolutely perfect tire for it. Perfect combination of performance, grip, handling, noise, longevity and comfort. If it was also a track car, I would be using RE-71R.

[TboneS54]

PS4S is life

[Thunderguts]

Originally Posted by MightyMouseTech

The contact patch will be the exact same size if you are running a 225, 245 or 275, if used at the same pressure.

Originally Posted by tracer bullet

Just agreeing with this fact in case anyone finds it hard to believe. The contact patch will change shape, but generally speaking be the same overall size in square inches. (Wider tire stretches it out, of course, but because the overall size stays the same that patch gets slightly shorter front - rear. Wider tires would be beneficial for sideways motions i.e. hard cornering, skinnier tires are better for gripping during acceleration & braking, i.e. winter).

Ehhhh, this is really only true in theory, but theory goes out the window in practice with differences in sidewall construction and tire design. Obviously a 225 track tire may have wider tread than a 255 all-season tire due to its profile. The narrower track tire may have an even larger contact because it flattens out more, but this is not always going to be true. Weight transfer under heavy braking, cornering, or acceleration will dynamically change the contact patch, which only amplifies differences in sidewall height and construction. Even in the same size and using the same pressure, two different tires can have different size contact patches. Thermal capacity is another reason to choose a wider tire. I completely understand what you're saying, but there's a lot more affecting the size of the contact patch than just the width of the tire.

Either Road & Track or Car and Driver did a really good article about 5 years ago on a BRZ riding on different size tires. There is definitely a sweet spot when it comes to track times as well as acceleration and braking and the widest tire is not always the best.

[tracer bullet]

Oh for sure, there are 100 other variables that affect things. There's always more to it.

It's a good theory to know though, to provide a basic idea of how things work. Lots of people think a wider tire automatically means more contact area, and don't understand that it's mostly just changing the shape.

[ShocknAwe]

Best thing to do is buy a good tire such as the MPS4S or RE71R. And make sure it doesn't rub anywhere. Rest is gravy tbh.

[Driven5]

Originally Posted by MightyMouseTech

The contact patch will be the exact same size if you are running a 225, 245 or 275, if used at the same pressure.

However, all else being equal, the 'optimal' pressure will typically be lower on the 275 than the 245, and lower on the 245 than the 225. Thus when set up properly, the wider tire would have a larger contact patch, and ultimately more grip than the same compound, construction, and diameter of narrower tire.

[MightyMouseTech]

Originally Posted by Driven5

However, all else being equal, the 'optimal' pressure will typically be lower on the 275 than the 245, and lower on the 245 than the 225. Thus when set up properly, the wider tire would have a larger contact patch, and ultimately more grip than the same compound, construction, and diameter of narrower tire.

Exactly. Which is why I run 265's at 33#.

[Eyeman]

Michelin PSS now PS4S is my favorite tire ever, use them on my Porsche also. I don't track my cars so I'm talking for daily driving.

[ShocknAwe]

Originally Posted by Driven5

However, all else being equal, the 'optimal' pressure will typically be lower on the 275 than the 245, and lower on the 245 than the 225. Thus when set up properly, the wider tire would have a larger contact patch, and ultimately more grip than the same compound, construction, and diameter of narrower tire.

Originally Posted by MightyMouseTech

Exactly. Which is why I run 265's at 33#.

Interestingly Apex countered and said stick with standard pressures when I asked them. I've been curious for a while what the optimal pressure for contact patch for my 275/35 tires would be. Figure it's somewhat tire type dependent.

[Driven5]

Originally Posted by ShocknAwe

Interestingly Apex countered and said stick with standard pressures when I asked them. I've been curious for a while what the optimal pressure for contact patch for my 275/35 tires would be. Figure it's somewhat tire type dependent.

That's the legal CYA response, and is an entirely reasonable initial recommendation. It's also going to be more than adequate for the vast majority of non-competition consumers. The true optimal performance pressure will depend on a combination of many factors though, consisting of the entirety of your car setup, venue, and weather, and going well beyond what the supplier could account for... Which is why I referenced 'all else being equal'. The only way to truly find the optimal pressure for your particular car and setup, is through objective testing. Change anything in your setup (weight, spring rates, sway bars, alignment, wheel size, tire size, tire compound, tire construction, etc.), venue, or weather, and that optimal pressure might also change.

[MightyMouseTech]

Originally Posted by ShocknAwe

Interestingly Apex countered and said stick with standard pressures when I asked them. I've been curious for a while what the optimal pressure for contact patch for my 275/35 tires would be. Figure it's somewhat tire type dependent.

Well, the 1M with 245/265 non run flats specs 35/35 for tire pressure.

[Expert@ApexWheels]

We tend to stick with stock pressures as a blanket recommendation to keep folks safe on the street. If you are tracking the car and really trying to optimize pressures you can bring the car in after a session and use a pyrometer to optimize pressures based on where the tires are warmer or cooler across the contact patch. The cold tire pressure will generally be lower than the street recommendation but they will come up to their working temp when on track. Ideal pressures will vary from day to day and even session to session depending on a host of factors like ambient temp, track surface temp and the tire compound/construction.

Generally speaking though once you've gotten to the point of optimizing your tire performance this finely you aren't even running street tires at all so it's rarely relevant for our street customers. If you are running the wheels and tires as a dual-duty setup and are tracking occasionally, you can check your pressures after the first session when the tires are still hot and air down a bit to get back to a more reasonable pressure range as pressures will likely increase on track. Remember to air the tires back up once the track day has ended though.

Hope this helps!

-Tom