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[JN2009]

Hi ,

Maybe somebody can explain to me why my dealer told me you can't put 255 at the back because it will afect the traction control system.It is true ?
I place a order for Yoko S-drive.

[Feyd]

False...

[Feyd]

...and BTW, how is it that complete fucking moron's work at car dealerships?

This is accross the board, regardless of brand IMO.

[Smac355]

i put 255's on last nite.. no issue, guy was smoking something

[rsjean]

Originally Posted by Feyd

False...

I'm sorry to admit but this subject always puzzled me. I had assumed that traction control systems and braking cotrol systems assumed a set tire traction range for a predetermined set of tires that would be the oem sets and changing that would throw things off.

But I'm also confused by the fact that no matter how narrow or wide a tire is, the footprint patch hitting the pavement is always the same for a given lbs per sq inch inflation. A wider tires footprint is just wider and shorter front to back than a narrower tire's.

That's why I cant work at a dealership because I'd be one of those idiots.

Plus I know I'm overthinking all of this and giving myself a headache.

[1013mm]

wtf? if anything it helps. I have 255s

[Feyd]

I think that part of what you are saying does have merrit, but I also think that you are overthinking it a bit.


I am by no means a technician, so lets think about this pragmatically.

What about northern european climates where cars absolutly must run snow tires in the winter (usually a narrower square setup), or for that matter the people running the apex wheels with 275/285s on the back?

I think that the computer system measures accelleration vs. grip. Meaning that when you hit the gas the car has an idea what ammount of force/rotational acceleration you should be achieving on said parts, but when something doesn't add up it will trigger the traction control system. Like when your wheels slip on wet pavement, or you hit a bump and the weight on the rear tires is lessened (if only for an instant) thus triggering it.

I ran a 235 square setup all winter and I had traction control lights every day. But, IMO this was because of the power the car is capable of delivering trying to get to the ground with softer/narrower tires.



Also, it makes way more sense for a car company to develop a set of algorithms for their computers that takes wheel/tire combinations completely out of the equation because of the reasons mentioned above and for reasons I can't even think of

Not saying that putting a set of chromed 22s on your car won't mess with your ABS system, but when you are flossin' that hard, who cares about stopping distance.

[rsjean]

That makes complete sense. Once you introduce the universe of things that can change traction outside of tires themselves it makes the argument that tire traction is calculated and put into an algorithm seem totally unworkable.

Thanks. Now my headache is gone.

Originally Posted by Feyd

I think that part of what you are saying does have merrit, but I also think that you are overthinking it a bit.


I am by no means a technician, so lets think about this pragmatically.

What about northern european climates where cars absolutly must run snow tires in the winter (usually a narrower square setup), or for that matter the people running the apex wheels with 275/285s on the back?

I think that the computer system measures accelleration vs. grip. Meaning that when you hit the gas the car has an idea what ammount of force/rotational acceleration you should be achieving on said parts, but when something doesn't add up it will trigger the traction control system. Like when your wheels slip on wet pavement, or you hit a bump and the weight on the rear tires is lessened (if only for an instant) thus triggering it.

I ran a 235 square setup all winter and I had traction control lights every day. But, IMO this was because of the power the car is capable of delivering trying to get to the ground with softer/narrower tires.



Also, it makes way more sense for a car company to develop a set of algorithms for their computers that takes wheel/tire combinations completely out of the equation because of the reasons mentioned above and for reasons I can't even think of

Not saying that putting a set of chromed 22s on your car won't mess with your ABS system, but when you are flossin' that hard, who cares about stopping distance.

[komitao]

for best results of the traction control, put 215s on the rear and have 235 in the fronts

[tgxmike]

Ok I'm going to chime in here..... (I'm an engineer and a nerd...)

Traction/stability control systems can only measure certain things... in most cases they ONLY measure wheel speed. They way the traction control system works is by comparing the left and right wheel speed. When the system senses a difference it will either brake a single wheel (DTC) or if the rear wheels are moving faster than the front it will cut power (DSC).

The 1er being BMW, they may also have accelerometers which can measure how much force from cornering is being exerted on the vehicle. The can also measure the distance the wheels are turned. so add these together.... Let’s add lots of speed and wheel turn, you get lots of lateral acceleration. You increase speed and you would expect to see the lateral acceleration go up, but it does not, it actually drops. The computer recognizes this drop as a slide and will reduce power. (DSC)

Another method to accomplish this is only accelerometers. If you have one front and rear, and one measures more lateral force than the other, the car is over steering. and the brakes are applied to the rear (DTC).

Last one if you made it this far. The car measures the wheels are turned, but there is no lateral acceleration and no speed difference between the right and left rear tires. The car is under steering and DTC correction is applied.

No where is tire size/traction part of this system. You SA is a complete Moron.

[Eddy@ApexWheels]

Morons.

They're playing it extra safe, and feeding you BS so they can kill the topic all together.

Hell, we have people running around with 275/35's in the rear now

[JN2009]

That what I think .Tanks guy !
I switch for 225 front 255 back

[Eyeman]

You should try to keep the diameter of your front and rear tires similar if possible. So if you went up from 245s to 255s in the rear you should also try to go up from 215 to 225 fronts. However if you don't, for sure since many have proven it, the traction control is not designed to pick up what will be a very small difference in rotational speed. If it were that sensitive it also might have issues when tire wear is uneven.

[_dopehead_]

I was getting a little worried there, i am getting Toyo's mounted this week in a 225/255 size.

[FactoryFast]

I am running the 255/225 setup with the Dunlop Dirrezza Z1 Star Spec's and after 5000 miles and a few warm days I can tell you its way more inspiring than stock...esp with the traction control OFF.

THIS CAR NEEDS A DIFF!!!

[Cisitalia]

Originally Posted by FactoryFast

THIS CAR NEEDS A DIFF!!!

This car does have a differential! I think you mean limited slip differential (LSD).

Depending on the car's suspension and tire traction ability (i.e. use of racing slicks), not all cars will need a LSD. Keep in mind these devices also create more fiction, thus more drive train loss and reduction of power to the ground. It's a trade off to some extent and depends on what type of driving/racing one requires.