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      09-22-2010, 09:19 PM   #1
gboop
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335i Torque Steer

Well... not really torque steer.

I've recently traded my G35 M6 for a manual e90 335i. Nissan or not, the G35 definitely had some burly character and will be missed. Thrashed it almost daily and it just barked back for more.

I've noticed that the 335i sometimes gets "squirmy" on uneven pavement under all out acceleration. This is something that the G never exhibited under the same conditions.

Is this due to lack of LSD in 335, or just the extra power (not that much more) over the G35, or something else?
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      09-22-2010, 09:24 PM   #2
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Has more to do with the tires I believe, the runflats tend do that on uneven pavement. At least that's the case on my car.
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      09-22-2010, 09:34 PM   #3
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Open diff doesn't help, but the way that the torque is deployed is also a factor.
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      09-22-2010, 09:34 PM   #4
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I'm almost thinking it's the suspension setup as well. I'm in a 328i but I kind of understand what you mean. I've also driven my Aunt's M35 and I LOVED the power.
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      09-22-2010, 09:37 PM   #5
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Mine does the same and I think it's the single most annoying aspect of the car. It's so pronounced that it requires minor steering corrections. To me, it feels exactly like power is being distributed alternately between the rear wheels and the car is being "steered" by the difference in power going to each wheel.

BTW - I have 265 non run flats in the rear and it doesn't seem to make much difference whether DTC is enabled, partially or fully disabled. I honestly don't see how some of these guys running tunes, meth, full bolt ons, etc can stand to drive it this way.

From what I've read, it can be remedied with an LSD and an assortment of M3 suspension parts. I honestly don't think I have the resolve to sink another $3k-$4k into it at this point.
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      09-22-2010, 09:40 PM   #6
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Quote:
Originally Posted by gboop View Post
Well... not really torque steer.

I've recently traded my G35 M6 for a manual e90 335i. Nissan or not, the G35 definitely had some burly character and will be missed. Thrashed it almost daily and it just barked back for more.

I've noticed that the 335i sometimes gets "squirmy" on uneven pavement under all out acceleration. This is something that the G never exhibited under the same conditions.

Is this due to lack of LSD in 335, or just the extra power (not that much more) over the G35, or something else?
Well 335 is rated at 300 for tq and hp, but in reality it more like 320-330. Of course lack of LSD is probably a big factor too.
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      09-22-2010, 09:44 PM   #7
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Open differential + e-diff + a big buttload of torque + 2nd gen runflats + very stiff shocks.
It's a combination of things interacting with each other.
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      09-22-2010, 10:08 PM   #8
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Originally Posted by chumley View Post
Mine does the same and I think it's the single most annoying aspect of the car. It's so pronounced that it requires minor steering corrections. To me, it feels exactly like power is being distributed alternately between the rear wheels and the car is being "steered" by the difference in power going to each wheel.

BTW - I have 265 non run flats in the rear and it doesn't seem to make much difference whether DTC is enabled, partially or fully disabled. I honestly don't see how some of these guys running tunes, meth, full bolt ons, etc can stand to drive it this way.

From what I've read, it can be remedied with an LSD and an assortment of M3 suspension parts. I honestly don't think I have the resolve to sink another $3k-$4k into it at this point.
You've nailed it. That's exactly how it feels. Caught me off guard a few times, as if the car is rocking for side to side. Kind of like a lizard running on it's hind legs

Regardless, it's not really annoying enough for me to seek a rememdy. Under most other circumstances things are very smooth (8/10 or below).... Actually 1/10 is a bitch to drive smoothly too (after more than 10 years of driving manuals)
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      09-22-2010, 10:12 PM   #9
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Has more to do with the tires I believe, the runflats tend do that on uneven pavement. At least that's the case on my car.
run flats are stiff without sid wall give
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      09-24-2010, 11:06 AM   #10
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how are your alignment specs. if your toe is not in at the rear, you lose acceleration/higher speed stability.

1st step is to get it checked. does the rear shift when hitting bumps/potholes on one side of the axle?
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      09-24-2010, 11:39 AM   #11
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My guess would be the runflats and the fact that you have much more instantly available power on the 335. I've flogged both of these cars on uneven pavement...breaking the read end loose on both. The 335 always felt more controlled. Remember that on the 3...if you're in second gear and floor it you have all 300 ft-lbs of torque immediately. The G in the same conditions needs to build up to its 270 ft-lbs of torque much more gradually with its naturally aspirated engine.
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      09-25-2010, 01:21 AM   #12
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It is mainly the run flats switch to non run flat and you will not have that skipping over the pavement feeling. I was once driving a 645i with run flat 19" at close to 136 mph taking this kink and all of a sudden the car hit this bump in the road and the 6er nearly jumped above the pavement for a good second or two and landed in the middle of both lanes. Thank god it was an empty highway because it was scary. Unlike the normal tires the run flats do not soak in the bumps but rather just skip over them.

On the other side recently one of my friends was involved in a serious wreck with his E60 M5. He had replaced his run flats with non run flats. The car was doing over 150 mph plus when the rear tire busted and the car lost control went into a ditch and hit a small fence and flipped over multiple times. This resulting in serious injuries to all the occupants of the car. The run flats have a good and a bad side. If maybe he had his run flats they would not have just blown out and he would not have lost control.

Another thing is that 335i has lot more torque at a lot lower rpm with no LSD but from all accounts the non LSD 335i coupe ran faster in Car and driver on a race track compared to many LSD equipped sports cars including the in house BMW Z4 M roadster etc.

here is a pic of his beautiful M5 all torn to pieces.

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Last edited by Kayani_1; 09-25-2010 at 01:27 AM.
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      09-25-2010, 06:21 AM   #13
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Tires, for sure. Runflats are great for steering response but they track horribly, following every grove or joint in the road (no sidewall give). I had non runflats on my E46 M with 245/35/19 on 8.5" rims on the front and it did not do this. I'm sure the open diff plays a role under acceleration but I notice this problem all the time so I think the root cause of the problem are tires. But I don't find it that bad. Also check your tires pressure.
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      09-25-2010, 07:16 AM   #14
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I think what is perceieved as crisp steering response on RFTs is primarily due to the reduced slip angle because of the lack of compliance of the side wall. Lack of slip angle and reduced side wall compliance is not necessarily a good thing.

I found a number of issues with the RFTs in addition to the jarring ride. They do not keep the contact patch on the road over rough surfaces and this can cause the rear end to step out on a bumpy curve. They also tend to not give as much warning as non RFTs when they are about to loose grip. In the hands of a driver who is not used to driving at the cars limits (i.e. almost everyone) this can be treacherous.



=====================

Slip Angle

A tire can only sustain a certain amount of force(s) until it loses traction; it starts to slip (Hence the term slip angle). And when it starts to slip speed is lost.

Slip angle is a term that tells you how much a tire is skidding (sliding/slipping). A bigger slip angle (measured in degrees of course) means that the tire starts to slide more...


Letís define what slip angle is:

When a tire is cornering the contact patch has to resist the forces of friction between the rubber and the road surface. Due to the elastic nature of the tire the tread is distorted in the way that forces are working at that particular time. Itís resisting the turning action, thus pointing a different way than the actual desired path.

This angular difference is called slip angle.



When a car enters a corner, all the tyres are turned with respect to the ground. Due to the elasticity of the pneumatic tyre, the tread in the contact patch will resist the turning action because there is friction generated between the rubber and the road surface. As a result, the treads on the contact patch will be distorted, whose direction always lags behind the direction of the wheel ( See figure in below ). We call the angular difference between the treads and the wheel's direction as Slip Angle.
Note : the car is turning left






Tires seem to operate at their peak performance when they are under a few degrees of slip angle, they generate the most grip at that particular slip angle. For race and high performance tires this optimum slip angle is around 6 to 10 degrees while this number is a little lower for street tires.

Due to low traction surfaces rally drivers reach even bigger angles. In drifting you probably see the biggest slip angle of all motorsports, sometimes as high as 40 degrees!

If you are cornering and the slip angle is below its optimum range the tire is considered to be under-used. If itís above this range the tire is being over-used. The trick is to stay within this optimum range so you use the tires to their fullest potential

I
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      09-25-2010, 10:15 AM   #15
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Quote:
Originally Posted by gboop View Post
Well... not really torque steer.

I've recently traded my G35 M6 for a manual e90 335i. Nissan or not, the G35 definitely had some burly character and will be missed. Thrashed it almost daily and it just barked back for more.

I've noticed that the 335i sometimes gets "squirmy" on uneven pavement under all out acceleration. This is something that the G never exhibited under the same conditions.

Is this due to lack of LSD in 335, or just the extra power (not that much more) over the G35, or something else?
Its in the tires. I bought a set of Vredestein tires. They are from Europe. Totally changed the way my car drove.
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      02-04-2013, 12:43 PM   #16
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i would like to re-open this thread.

I don't think it's the tires, as I'm having the same problem when I accelerate hard with my PS2 tires.

This morning I decided to accelerate hard and when i went from first to second gear the car shook left and right. I had to correct it with steering.
The road was wet.

I read that this was called Torque Steer and it is normal... this will bug me

Is this due to not having an LSD?

can anyone shed some light, thanks.
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      02-04-2013, 12:46 PM   #17
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Is this due to not having an LSD?
Yes.

/thread
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      02-04-2013, 12:48 PM   #18
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You need to make sure that your rear alignment is bang on and that you don't have any play developing in bushings or balljoints back there.

Those are the #1 factors I've observed contributing to the rear end not behaving itself under power (or rough roads, or crowned roads, or heavy side winds, or.....)
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      02-04-2013, 12:52 PM   #19
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Quote:
Originally Posted by CS View Post
i would like to re-open this thread.

I don't think it's the tires, as I'm having the same problem when I accelerate hard with my PS2 tires.

This morning I decided to accelerate hard and when i went from first to second gear the car shook left and right. I had to correct it with steering.
The road was wet.

I read that this was called Torque Steer and it is normal... this will bug me

Is this due to not having an LSD?

can anyone shed some light, thanks.
Torque steer is a front wheel drive (only) issue. When accelerating around a corner the steering is affected by the torque from the front wheels.
RWD 335s are essentially 1 wheel drive cars so you are probably feeling the torque being applied to one wheel and then the other as car struggles for traction.
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      02-04-2013, 01:33 PM   #20
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The 335i with RFTs and the stock shocks does not handle rough surfaces well. The car tends to bounce around and the contact patches do not stay in contact (they are called contact patches for a reason ) with the road surface.
This can make the car feel very skittish.

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      02-04-2013, 02:33 PM   #21
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Yes the RFT suck, the open LSD sucks but it's the the massive difference in torque that's to blame mostly. Cars like G35/G37 have way less TQ compared to the 335. All that TQ avalable down low means rear tires overpowered.

Look at this chart and that's with the G37 (328hp 270tq) not G35

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      02-04-2013, 06:34 PM   #22
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This issue is covered extensively elsewhere in the forum - it is more likely due to the soft rubber rear subframe bushings. Many people change over to M3 bushings, or you may wish to try inserts from Powerflex.
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