[jmwilson125]

Originally Posted by Viffermike

I do. Colder air is more dense, meaning the fuel/air mix will likely run more rich, heat soak is much less of an issue, and since the M240i is basically new the ECU hasn't 'learned' the driver's behavior well enough to adjust detrimentally to a launched run ...

... and these days, winter tires can be pretty darned grippy when warmed up and on dry pavement. They can be far better in those conditions than even the best A/S performance tire; that's been proven by independent testing. It's all about the ambient temp that the rubber performs best in.

I swear my winter sottozerro tires are almost as grippy as my mpss. Its rediculous, but they just grip and go.

I reccomened them to my buddy who runs mpss on his c7 stingray. He says the same thing

I'm fbo with meth too.

[aerobod]

Originally Posted by jmwilson125

I swear my winter sottozerro tires are almost as grippy as my mpss. Its rediculous, but they just grip and go.

I reccomened them to my buddy who runs mpss on his c7 stingray. He says the same thing

I'm fbo with meth too.

I agree, on dry roads the 225 wide Sottozero tyres at sub zero temperatures have grip levels as good as the 245 wide MPSSs until the ambient temperature climbs above 20°C.

[9t2hoo]

Originally Posted by aerobod

I agree, on dry roads the 225 wide Sottozero tyres at sub zero temperatures have grip levels as good as the 245 wide MPSSs until the ambient temperature climbs above 20°C.

I read somewhere that thinner tires provide more grip for launching a car, but less grip in the turns. Apparently, the contact patch on a thinner tire is longer than the contact patch on a wider tire. So perhaps the 225 rear Sottozeros that you run in the winter provide the same grip as the 245 MPSS do in the summer: the long contact patch on the 225 Sottozeros offsets the stickier rubber of the 245 MPSSs (in warmer temperatures).

[Mr Carrots]

no way is stock doing 3.8, even with LC

but I'll eat my words if there's a vbox reading to back it up


I'm hoping for @3.5 with meth (and no LC obviously)

[pikcachu]

Originally Posted by 9t2hoo

I read somewhere that thinner tires provide more grip for launching a car, but less grip in the turns. Apparently, the contact patch on a thinner tire is longer than the contact patch on a wider tire. So perhaps the 225 rear Sottozeros that you run in the winter provide the same grip as the 245 MPSS do in the summer: the long contact patch on the 225 Sottozeros offsets the stickier rubber of the 245 MPSSs (in warmer temperatures).

Sorry but this makes no sense at all....

Let's say you put 2 tires of the same size together, side by side, the tire would be twice as wide but the contact patch will not get any longer, it will be exactly the same cause it's the same tire.....

To increase the length of the contact patch you need to increase the diameter of the wheel... that's why dragsters use huge wheels on the rear

The only condition I know where you want thinner tires for traction is on snow...cause you want the tire to claw in... so the less surface, the more it sinks on it...

[9t2hoo]

Originally Posted by pikcachu

Sorry but this makes no sense at all....

Let's say you put 2 tires of the same size together, side by side, the tire would be twice as wide but the contact patch will not get any longer, it will be exactly the same cause it's the same tire.....

To increase the length of the contact patch you need to increase the diameter of the wheel... that's why dragsters use huge wheels on the rear

The only condition I know where you want thinner tires for traction is on snow...cause you want the tire to claw in... so the less surface, the more it sinks on it...

Read this article: http://www.roadandtrack.com/car-cult...-tire-patches/

I'm homing in on the part where it says "Installing fatter tires widens the patch, but it also shortens it front-to-back. Because of this, cornering gains can be offset by diminished straight-line traction, including braking and hydroplaning resistance."

[pikcachu]

Originally Posted by 9t2hoo

Read this article: http://www.roadandtrack.com/car-cult...-tire-patches/

I'm homing in on the part where it says "Installing fatter tires widens the patch, but it also shortens it front-to-back. Because of this, cornering gains can be offset by diminished straight-line traction, including braking and hydroplaning resistance."

Well... I just don't understand how what it says it's possible...

"Merely increasing the width of a tire doesn't increase the area touching the pavement"

If I double the width, then the area will double..

"Installing fatter tires widens the patch, but it also shortens it front-to-back."

How on earth does the patch shortens with a wider tire ?

[9t2hoo]

Originally Posted by pikcachu

Well... I just don't understand how what it says it's possible...

"Merely increasing the width of a tire doesn't increase the area touching the pavement"

If I double the width, then the area will double..

"Installing fatter tires widens the patch, but it also shortens it front-to-back."

How on earth does the patch shortens with a wider tire ?

Doubling the width of the tire does not increase the size of the contact patch, which depends almost entirely on the weight of the vehicle and the air pressure in the tire. Doubling the width of the tire just changes the shape of the contact patch. Wider tires resist lateral movement better than skinnier tires because the contact patch on wider tires runs from side to side. Skinnier tires are better for straight line acceleration because the contact patch runs from front to back.

The only way to have a wider tire with a longer contact patch than a skinnier tire is either to increase the weight of the vehicle or to reduce the air pressure in the tire.

The reason that BMW uses staggered wheels and tires on RWD cars is to reduce oversteer because the contact patch on the wider rear tires will resist lateral movement more so than a square tire set up would. At the track, where you want rotation, a square set up will improve handling, but it will also create the risk of unintended oversteer. I actually use the 225 Sottozeros in a square set up for my winter tires. They handle pretty well, but I have to remind myself that they are more prone to oversteer because the rear tires are skinnier than stock and the rubber compound is not as sticky as the MPSSs.

[pikcachu]

Originally Posted by 9t2hoo

Doubling the width of the tire does not increase the size of the contact patch, which depends almost entirely on the weight of the vehicle and the air pressure in the tire. Doubling the width of the tire just changes the shape of the contact patch.

So if you keep weight and tire pressure the same, how doubling the width, doesn't double the contact patch?

Don't get me wrong... I'm not saying your are right or wrong... I just can't understand the logic....

[TajoMan]

Originally Posted by pikcachu

So if you keep weight and tire pressure the same, how doubling the width, doesn't double the contact patch?

Don't get me wrong... I'm not saying your are right or wrong... I just can't understand the logic....

Pressure = Force/Area

Pressure = tire pressure
Force = Mass of the car (times gravity)
Area = Tire contact patch

As long as tire pressure and mass of the car stays the same, contact patch area will stay the same.

[jmwilson125]

Originally Posted by pikcachu

So if you keep weight and tire pressure the same, how doubling the width, doesn't double the contact patch?

Don't get me wrong... I'm not saying your are right or wrong... I just can't understand the logic....

I was in the same boat as you, but they way it's being described does make sense.

What this doesn't take into account is the tread block squish and the additional force from weight transfer accelerating, and the fact that the contact patch gained by dropping psi or adding weight is not linear.

You can keep adding weight to a car or taking psi out of the tire, but at a certain point the car would be resting on the rim. If that were the case, then doubling the tire width would be doubling the contact patch. That's an extreme example though.


So I guess the article is right in saying that wider is not always better, but I do think they over simplify the topic. I'm just half talking out my ass though, so who knows

[ianp622]

Originally Posted by pikcachu

So if you keep weight and tire pressure the same, how doubling the width, doesn't double the contact patch?

Don't get me wrong... I'm not saying your are right or wrong... I just can't understand the logic....

You're thinking of the tire as a solid object, but remember that it's squishy with the air. So if you make it wider, it's not going to deform as much in the forward-backward direction.

[XutvJet]

If you think winter performance tires are providing the same level of lateral and transitional grip as the MPSS tires, then you're not driving the car hard enough in the cold LOL

I can attest to the fact that narrower winter performance tires do indeed improve straight line acceleration grip. I have far more acceleration traction in 1st and 2nd with my 75% worn 225/40R18 Michelin Alpin PA4 compared my half worn MPSS 245/35R18s. I attribute the grip increase to the PA4's soft winter rubber compound, soft sidewalls, and the tall, siped tread blocking that brushes and displaces itself against the pavement under hard load compared to the stiff, unsiped tread block and sidewalls of the MPSS which can't bit downwards nearly has hard.

With that said, in the dry and at their ideal operating temps and ambient conditions, the PA4s DO NOT have the same threshold braking abilities. I can get my PA4s to lock up much quicker than my MPSS tires. I'd venture to say that from 60mph, the PA4s take 20+ more feet to stop. It's a trade off with winter tires.

[jmwilson125]

Originally Posted by XutvJet

If you think winter performance tires are providing the same level of lateral and transitional grip as the MPSS tires, then you're not driving the car hard enough in the cold LOL

I can attest to the fact that narrower winter performance tires do indeed improve straight line acceleration grip. I have far more acceleration traction in 1st and 2nd with my 75% worn 225/40R18 Michelin Alpin PA4 compared my half worn MPSS 245/35R18s. I attribute the grip increase to the PA4's soft winter rubber compound, soft sidewalls, and the tall, siped tread blocking that brushes and displaces itself against the pavement under hard load compared to the stiff, unsiped tread block and sidewalls of the MPSS which can't bit downwards nearly has hard.

With that said, in the dry and at their ideal operating temps and ambient conditions, the PA4s DO NOT have the same threshold braking abilities. I can get my PA4s to lock up much quicker than my MPSS tires. I'd venture to say that from 60mph, the PA4s take 20+ more feet to stop. It's a trade off with winter tires.

Personally I was saying that I was impressed with straight line acceleration. I do not ever push my winter tires, I do drive them quickly though. I just always think of burning marshmallows in my head anytime I think of driving the winters hard.

One those things get about 50 F they feel pretty squirmy.

Also on a side note I did an hpde event in NH at Cannan speedway at the end of October. I ended up running a 1:11:xx for my best lap with a maximum of 1.24 g on mpss. It was dry and about 38F. It took about 8 laps to get tires up to temps the first session.

[XutvJet]

Originally Posted by jmwilson125

I do not ever push my winter tires, I do drive them quickly though. I just always think of burning marshmallows in my head anytime I think of driving the winters hard.

So true. I think about it every time I throw my car into a corner or hammer it in a straight line. My rears are certainly more worn than the fronts

[jmwilson125]

Originally Posted by XutvJet

So true. I think about it every time I throw my car into a corner or hammer it in a straight line. My rears are certainly more worn than the fronts

Bmw tech after changing my oil "everything checks out perfect, but the rear tires show some wear!"

Me - (holding breath, one eye open) "really!?....great!"

Car in background fbo, catless, meth, gold intake, hre wheels, carbon everything, tint. Jb4 tuckup up away from obd2 port hahahahah.

Also apologies for aiding in this thread derailment. I did learn something new about tire width and lateral grip though so that's good.

[coskibumz]

Originally Posted by Viffermike

I do. Colder air is more dense, meaning the fuel/air mix will likely run more rich, heat soak is much less of an issue, and since the M240i is basically new the ECU hasn't 'learned' the driver's behavior well enough to adjust detrimentally to a launched run ...

... and these days, winter tires can be pretty darned grippy when warmed up and on dry pavement. They can be far better in those conditions than even the best A/S performance tire; that's been proven by independent testing. It's all about the ambient temp that the rubber performs best in.

Test run came in at 4.25 0-60
Stage 1 Dinan plus Dinan cold air induction.
Problem 4,970 altitude
The app on my phone recorded 0-60 in 3.0
So I spent $100 and got a Matrix Kat so it could tell me I am slow. Had my doubts about the 3.0 in the first place, but I really felt good while it lasted

[dradernh]

Originally Posted by coskibumz

The app on my phone recorded 0-60 in 3.0

Well, at least it was in the ballpark, though, right?

[B58togo]

You guys need to pick up a Dragy if you're hell bent on recording accurate times. I have real world track time slips and the Dragy is very, very close.

http://www.burgertuning.com/dragy_gp...nce_meter.html

[DaleHeinz]

Originally Posted by B58togo

You guys need to pick up a Dragy if you're hell bent on recording accurate times. I have real world track time slips and the Dragy is very, very close.

http://www.burgertuning.com/dragy_gp...nce_meter.html

Seems quite good compared to the much more expensive Vbox. Gonna have to check this out. Phone apps are fun, but horribly inaccurate.

[tennisfreak]

Originally Posted by B58togo

You guys need to pick up a Dragy if you're hell bent on recording accurate times. I have real world track time slips and the Dragy is very, very close.

http://www.burgertuning.com/dragy_gp...nce_meter.html

In the Google play store the required app gets horrible reviews.

Makes me hesitant to spend $150 on it.

[DaleHeinz]

Originally Posted by tennisfreak

In the Google play store the required app gets horrible reviews.

Makes me hesitant to spend $150 on it.

I wonder if that's just merely a software issue of Apple vs Android. Dragtimes on YouTube does a very well done review of the Dragy and comparison of the Dragy vs Vbox. He used the Apple app for his Dragy. Time comparisons were almost dead on between the two. Within a half mile per hour and hundredths of seconds in all categories. Dragy seems to use the very same high speed GPS data that the Vbox does for a much lower cost.

I think I'm going to be ordering the Dragy this weekend.