[Mavus]

Originally Posted by VisualEcho

Depends on your driving style and the tires you choose. Some, like myself, like it playful and loose, I'm not competing on my commute. And with regards to tires, the MPSS runs wide, so if you're not careful you can get 255/275 that are no wider at all, and possibly skinnier.

I do think that playful character would be maintained with 255 275 since it's built in the chassis and shorter wheelbase while stability and grip would be improved. The car obviosly has a lot of tq so it's not an issue to get the rear end out even with sligtly wider tires. We are talking about mpss or 4s and not nt01 or r888.

[Karmic Man]

Originally Posted by cptobvious

Yes, that's a really good point. I'd thought of that, but the reason I went with 275 is according to Tirerack, the tread width of the General 275/35/19 is 9.5" while the tread width on the MPSS 265/35/19 is 9.4"

My understanding is that tread width is ultimately most important with regard to DSC? But, I could be totally talking out of my A** and happy to be corrected!

No...if the diameter of the tyres F & R is out of range the DSC gets confused BUT it is self learning and after a bit of mileage the sensitivity of the DSC will regress to normality

[CSBM5]

cptobvious - there's a term tire engineers refer to as "mixability." Every tire design obviously has its own range of performance metrics, and a few of those can be very important to the stability of the car such as ultimate grip (clearly) but also as important is the cornering force versus slip angle response of the tire. Without reasonable balance, front to rear, of that tire response equation, transient inputs (turning into curves, making quick corrections, etc) can seriously be degraded even to the point of serious instability.

Taken to an extreme to illustrate -- put a PS4S on the front and the cheapest possible all-season junk tire on the rear; you can fill in the blanks = massive oversteer at steady state limit, plus huge gooey oversteer response to transient steering inputs, etc, etc.

Anyway, just wanted to point out "mixability" -- tire engineers have a database for their company's tire's performance envelopes to be able to quickly tell if they can be "mixed" on the front and rear of a vehicle, reasonably. As to mixing brands of tires, they wouldn't yield an opinion as it would just be educated speculation, but the general reply would be to put the junk tire up front (just to keep the average person clearly in the understeering regime no matter what).

[cptobvious]

Originally Posted by Karmic Man

No...if the diameter of the tyres F & R is out of range the DSC gets confused BUT it is self learning and after a bit of mileage the sensitivity of the DSC will regress to normality

You guys rock! Seriously.

You know, this makes perfect sense, and seems to mirror my exact experience. Per omasou and VisualEcho, getting the larger rear tires resulted in rake, which then threw off the DSC. I mean, right out the gates, the car just felt totally off - weird jitteriness. And I realize it now, it's the exact same feeling as when the nannies kick in.

But, now, after several days of lots and lots of driving, the car seems to be back to totally normal. Now, I wouldn't be able to tell the difference if you had me drive the two "setups" back to back.

Learn something new everyday!

[omasou]

Originally Posted by Karmic Man

No...if the diameter of the tyres F & R is out of range the DSC gets confused BUT it is self learning and after a bit of mileage the sensitivity of the DSC will regress to normality

This is the first time I have heard about DCS adapting.

Which them confuses me as to why everyone get so stressed out about front to rear ratios every time there's a tire discussion?

Also do you know why this doesn't this help w/all-wheel drive systems?

I forget the situation but I needed some new tires on the E70. The rep told me for the all wheel drive (not the OPs situation) that I could only have a certain difference between front and rear or that I could break the drive train. Though he was BSing me until I researched it a bit.

https://www.tirerack.com/tires/tiret....jsp?techid=18

Which of course raises the question. How do high performance cars, Porsche and now BMW M cars w/all wheel drive not have problems? One would think the rears on these cars are worn significantly more than the fronts and exceeding the limits discussed in the article?

[VisualEcho]

Originally Posted by omasou

Which them confuses me as to why everyone get so stressed out about front to rear ratios every time there's a tire discussion?

I think every car is a bit different, some have more tolerance for such things, and others don't.

I know on the Lotus, if the OD of the rear is too big, or the rake is negated with a larger front OD, the car can go into limp mode pretty easily.

And as far as the ECU learning, that happens as well. Let's say you add a Cup car airbox and decat. Without a professional tune to tell it otherwise, the ECU will negate the hp gain. Crap, but true.

I think some guys have experienced issues and word gets around, and without proper knowledge of what caused those issues, many are left just guessing as to what caused them.

From what I've seen, the M2 is quite tolerant of width and OD differences.

[Tag]

Originally Posted by ///AVM

So, thinking of Cpt's statement and Tag's open invitation toward forum member feedback . . .

I know one thing a lot of people like about the M2C is it's loose rear end, or what we like to call 'playful.' I personally wish I could get a little more grip than slip. In this regard . . .

1. Has anyone switched from PSS to PS4S and feel the dry pavement grip was noticeably improved? Overall ride quality noticeably different, better or worse? I have experience with both tires, but not on the same vehicle so my bias toward the PS4S is not more opinion than validated.

2. I have never looked up the recommended PSS psi for the M2C. I am assuming my psi are set at recommended. Has anyone dropped the psi 2 or 3 below recommended on stock (PSS) tires? My suspicion is this might give a little more road grip I am after, as well as less firm ride quality.

3. I assume the tire pressure 'alert' does not go off until the reading is +/-4 from recommended? Can anyone verify the 'alert' range?

Thank you

///AVM

1. I know Artemis made the switch on his OG M2 prior to getting an M2C. Perhaps he could chime in?

2. I've played with dropping PSI, never increasing it. Depending on how low you go you can get ever so slightly more comfort, but it's not day and night. With lower pressure you will lose some handling.

3. I think it's more or less how quickly it looses pressure rather than just +/- a few PSI. You can easily go +5 PSi or more just from warmer temps and aggressive driving.

[omasou]

Originally Posted by VisualEcho

I think every car is a bit different, some have more tolerance for such things, and others don't.

I know on the Lotus, if the OD of the rear is too big, or the rake is negated with a larger front OD, the car can go into limp mode pretty easily.

And as far as the ECU learning, that happens as well. Let's say you add a Cup car airbox and decat. Without a professional tune to tell it otherwise, the ECU will negate the hp gain. Crap, but true.

I think some guys have experienced issues and word gets around, and without proper knowledge of what caused those issues, many are left just guessing as to what caused them.

From what I've seen, the M2 is quite tolerant of width and OD differences.

I've heard of ECU/engine adaptation but not the DCS.

[Tag]

Made this post a while back, but think it's worth repeating in this thread. It was part of another thread cptobvious made. He also made the mistake of referring to us as "Esteemed colleagues" in that thread instead of just opening with, "Hey, aholes".

Originally Posted by Tag

If you go with wider tires you want to keep the same F/R ratio to maintain the cars handling characteristics. For example, if stock is 245 F and 265 R you'll want to have the same ratio with wider aftermarket tires such as 265 F and 285 R.

Great, you're thinking this is doable... not so fast, Cochise. We're just getting started.

Go with a 265/30/19 up front and the overall diameter is 12mm less or 6mm less sidewall. Go with a 265/35/19 and its diameter is 14mm or 7mm taller sidewall. Both sizes mess with your spedo and ride height. But, the taller diameter tire can also induce rubbing not to mention it weighs more and needs more torque to rotate its mass. That said you could run the same setup as the F80/2 and should be OK. That would be a 255/35/19 F and 275/35/19 R. The front and rears would both come in at 7mm taller or 3.5mm taller sidewall so they'd not only be even, but also within tolerances.

Here's an awesome wheel and tire calc.

When installing wider tires you'll also need to take into account wheel poke and/or potential rubbing, if any. In my experience wider tires tend to improve the ride quality, although they are more prone to tramlining.

Here's an awesome video that I think will help clarify the pros/cons of wider tires and making sure you get the ratio right.

Source: https://f87.bimmerpost.com/forums/sh...7#post25344557

[jdubm2c]

Originally Posted by cptobvious

You guys rock! Seriously.

You know, this makes perfect sense, and seems to mirror my exact experience. Per omasou and VisualEcho, getting the larger rear tires resulted in rake, which then threw off the DSC. I mean, right out the gates, the car just felt totally off - weird jitteriness. And I realize it now, it's the exact same feeling as when the nannies kick in.

But, now, after several days of lots and lots of driving, the car seems to be back to totally normal. Now, I wouldn't be able to tell the difference if you had me drive the two "setups" back to back.

Learn something new everyday!

I burnt through the OEM rears in 11k miles, and the dealer said no problem when I asked them to put on 275/35 PSS's as the replacements. I was not happy on the drive home, and seemed similar to your initial feelings that the car was just off a bit. It also seemed to be tram-lining more. They had pressures up around 36psi cold, but I like them at about 32psi cold in the summer, so they warm up to about 36psi. I reset the pressures down to where I like them after a couple of days, and then the car was back to how I remembered it. Now I am not sure if it was the psi or the car getting used to the new size rear tires. I don't think I can tell any difference in traction with the whopping .190" tread width I gained though!
I'm going to try to have coilovers, camber and track wheel/tires done over the winter. I am hoping to move up to 265f/285r with that set up on some stickier tires. I think this car is under-tired stock, so I am anxious to try this setup.
Does anyone's PSS's squeal when they lose traction? Mine are silent when the rear end steps out.