new tires but losing more grip than usual

[woobiee]

Hey all, just need a bit of assistance.

Just got new tires and got them mounted. Previously I replaced my control arms/bushings and made my alignment off so with the new tires on the car, I went to the shop today to get the car aligned.

Camber setting at -1.0 front and -2.0 rear. All else factory specs

Dropped with PSS9 coils at the lowest setting.

On the way to work, the car was more twitchy, which i understand. However during a few turns on the freeway, I lost grip; DSC came on to prevent the car from spinning. On the off ramp, again it lost grip.

This has not happened before the alignment w/ new tires.

Are my camber specs really off? Or could it be because the tires are new?...or both?

thanks!
Andy

[Chet Vlaun]

Can you give a little more background. What tires are you using? Are they scrubbed in? What pressure, what are the shocks set at in terms of stiffness? Do you have any wscrubbing on the outer shoulder blocks? How many miles do you have on the tires.
I had installed new tires on my 528 and nearly lost it in the turn a couple times until the tires were scrubbed in. After that, the worked great.

Let's see what we can figure out here...

Regards

[woobiee]

sorry to be a noob, but what is scrubbed?

the tires probably have about 75-100miles. they are michelin pilot sport PS2. 235/40/18 front and 255/35/18 rear.

the pss9 is set to its lowest, at setting 4 for damper (1 being stiffest, 9 being softest)

i have 12mm spacers front and 15mm spacers rear. i dont think they are the problem as ive had these for a few years without problem.

[black_box]

scrubbing them in just means breaking them in, like you would a new pair of shoes. The rubber has a coating put on it when it goes into the tire mold, which is what forms the tread. Sort of like spraying the frying pan with oil so your eggs don't stick, the coating helps remove the tire from the mold. Some of this coating may still be on the tire when you get it and it reduces the traction. I think the mileage guideline is a little higher for them to be broken in, something like 200-500 miles?

As Chet mentioned, check the tire pressures first.

were you accelerating when the DSC came on? maybe the rear toe-in isn't set right. Your camber is a little weird, usually the desired settings is with the front having more negative camber than the rear (i.e., -3 front, -2 rear). Your settings make me think it would understeer... but maybe its something else. Maybe its time for some new suspension bushings and the new tires are just pointing that out.

You could try softening up the rear, specifically the compression/bump, but i don't think pss9's are double adjustable.

[woobiee]

thanks for the help thus far.

i strongly believe that it is the alignment. ive mounted and drove on these new tires for a few days before the alignment and everything felt right. the only thing wrong was the alignment obviously but it did not lose grip at all.

on the highway today i believe i was accelerating just a bit when the back end started to come loose. i was going about 80mph. this is very odd as this has never happened before; even on close to bald tires.

again on the off ramp, i was going around 50mph when it came loose. again this has not happened before; ive gone through this off ramp well over 60mph many times and never had problems.

[elh0102]

Well, you probably need more front camber, but that will actually be counter to getting more grip in the rear. It's possible the rear toe is off enough to be causing a problem. It's also possible your rear damper setting is too stiff, but unless you noticed the loss of traction on uneven surfaces, I doubt that is the problem. I would have the alignment checked. Those are excellent tires, and I think you have enough miles on them for break in.

[woobiee]

ive been figuring the problem out for a few hours and it seems that ive eliminated all the factors but the alignment. it seems quite well that that is the problem.

i know this may sound like a bad idea, but can anyone share their alignment specs so i may compare. or does anyone have suggestions. most than likely i will need to visit the shop again to get it realigned.

[AlaskaBlue]

Have you taken into account the temperature?

[CirrusSR22]

I'd drive the tires a few hundred miles more before I did anything major.

[woobiee]

thanks for all the advice guys.

i will not do anything until the tires are broken in. it may be just im not used to summer tires (this is my first set)

[woobiee]

revisited.

so we've been troubleshooting for the past week and we have came up with this:

Pretty much, on very hard cornering, the front would start giving grinding noises, DSC+ABS kicks in and oversteer occurs. Our first thoughts were the tires were rubbing up front. However after inspecting tires, liners and such, no such evidence were displayed.

Our next step was to turn DSC off. This solved the problem; taking turns is much better.

Now question is, why would DSC all of a sudden start doing this and not before with my old set of crappy tires? The one thing I can think of is the front tires are not worn in yet?

[black_box]

can you describe the "grinding" noise? is it metal on metal?

Assuming you hold the steering wheel in one position for a constant radius turn and then accelerate mildly from a standstill, at some point you'll be going too fast for the front tires to be able to turn the car. They'll start to squeal a little bit at first (this is usually when they're "happy" and providing near max of their grip). Then they'll get pissed and start to really squeal loudly. and finally, they will give up and stop rotating normally. This is when they start skipping over the surface and making a much louder sound, with a lot of vibration. At this point, you're really into understeer, and turning the steering wheel into the turn will only make things worse. If this is what you're getting, then you're just pushing the tires too hard. obviously you'll need to be careful if the tires get to the point of squealing, they won't have much grip left at that point.

Check your tire pressures. Then, check the sidewall of the tire and look to see how far the tires is rolling over. There should be little triangles or arrows on the sidewall, pointing towards the tread. If the arrows are starting to get worn, then the tire may need more air.

AlaskaBlue made a good point, whats the weather like there? I don't think summer tires like to be much below 40F ambient temperatures. It could be a combination of new tires that aren't quite broken in and cold ambient temperatures. I'm not sure how sensitive the DSC system is for your car. I'd find an empty parking lot and do a small skidpad exercise. Try it with and without your DSC (watch out for lightpoles :)) Gradually increase your speed until you get the vibration. If the same thing happens with DSC off, just at a higher speed, i'd guess that its just an understeer issue and you'll need to slow down for turns more than you're used to.

[woobiee]

black_box - great info. the grinding noise is the DSC and ABS kicking in, pretty much interfering. I think it is being premature and detecting wheel spin at which it tries to correct itself. When the DSC is turned off, everything seems fine and I am getting loads of grip.

The tires have NEVER squealed yet so I believe the tires are out performing my car.

Yesturday was probably around mid to low 50s so it is not 'hot'.

It is funny that as of now, it is safer for me to have DSC off than on.

[sd203]

The DSC shouldn't be switched off to cure your problem.

Have the suspension and settings ( control arms, bushings checked )

MAKE SURE the ALIGNMENT IS CORRECT.

Have the tires inspected for any defects.

The tires outperforming the car ?

No way. Have a BMW tech take a look at it first.

New tires should not give you this kind of response from your DSC.

[M3@Apex]

Doesn't DSC take into account how fast each wheel is spinning? I've heard of some people running incorrect tire sizes and DSC or ASC just kicks in for no reason becaues they think you're losing traction. Most the time it happens at higher speeds........perhaps your cornering is making the system think that.

Your PS2's should be no problem though, I love those tires.

[woobiee]

after two sessions, this was the best we could do without camber plates

Camber front: -1.22 | -1.24
Toe Front: 0 | 0
Caster: 4.74 | 4.94

Camber rear: -1.76 | -1.57
Toe rear: 0.11 | 0.13

the numbers are not outrageous; i think its acceptable.

from the feel and such, the front is where it is doing all the wrong stuff. its almost the same feel as if you were to slip in the snow, while you try to steer to the right direction the DSC and ABS comes on to compensate for the slip. The noises it makes are quite similar if not the same; groaning and grinding. It might be the sound from the ABS pumping.

One time during this strange situation on a hard turn, i tried tapping the brakes and strangely, the brake pedal exhibited the ABS being used; stiff brake pedal, lots of vibrations, and obviously the noise. Perhaps DSC did not engage and that when ABS is in use, the DSC light comes on as well?

I guess the car 'thinks' it is losing grip/control, ABS and/or DSC comes on to correct it. But to contradict that, turning off DSC, the car handles superbly...probably average 10-30mph faster on corners without any issues. (no ABS or anything else intervening)

The only thing that has been changed is A) new high performance AND much better tires at 235/40/18F and 255/35/18R vs the original all season high performance 235/40/18 all around and B) the alignment. Everything else did not change.

[sd203]

Did you finally bring the car into the BMW shop, and have them check it ?

I had a friend have the same problem with his car. The Alignment was done by some back street shop. They screwed it up pretty bad.

The wrong tire/ suspension set up will do it. You mentioned you had the car lowered ? Have you taken all of this into account ?

By driving the car this way, you may be adding stress to the suspension.

Could it be your new control arm or bushings are defective, or not installed properly ? I doubt if that's it, but HAVE THE CAR LOOKED AT.

Unless there is something seriously wrong with your new tires, you have a big problem.

Defective tires are possible, but unlikely........you never know though.

[woobiee]

all the alignment work was at a bmw shop.

this problem started only 2 weeks ago when new tires were put on after the alignment. ive had the new control arms/bushings for a good 2 months with no problems. coilovers were on the car for about 1-2 years which has never faulted.

why would this happen when DSC is on; and when its off it is perfect. its very odd.

[Hathaway]

The only thing I can think is that your DSC thinks your tires are slipping now because the wheels are different sizes front to back, so they are spinning at different speeds (slipping). I know Ive seen better calulators, but heres one I just found quick on a google search.

http://www.miata.net/garage/tirecalc.html

[woobiee]

wow ive never thought of that; and it makes sense!

factory specs for option 18 wheels for my car is 225/40/18 | 255/35/18 .... perhaps the car doesnt like the 235/40 | 255/35 combination?

interesting

[sd203]

Think you hit the nail on the head. Tires are the problem

[Hathaway]

Im just rocking this wheel and tire forum today.

[Antithesis]

I know running the wrong size tires will upset ABS on occasion, I had this issue on my rex. I don't think it's too much of a stretch that it would mess up your traction control. I'd sell those tires and go as close to stock sizing as possible. Keep in mind that sometimes tire sizes can vary between companies. I know it is supposed to be measured in millimeters, but for example, if you hold a potenza next to an azenis rt-615 of the same size, the potenza has a physically wider track. Just something to take into account.