[chris330D]

Read this with interest. I suppose half the problem is knowing what normal is like for the car. I have a touring with standard M Sport suspension and don't recognise any of the traits described here. It handles really well, corners flat and has huge amounts of front grip. The only downside is mid-corner bumps. If you head north up the M23 to where it joins the M25 there is a fast long corner as the slip road turns up, round and down to the M25. there is a bump mid corner and the car will jump sideways. This is a change from the e46 which was fine. Not sure if it is tyres or suspension.

[NFS]

Originally Posted by ss134

My car now feels rock solid on the Autobahn at 150+ speeds, i can change lanes at very high speed with total contol and precision whereas before it felt very loose/not confidence inspiring............ When my car came from the factory it had a faulty steering pump which really affected the feel and control at high speeds (took 6 months to diagnose!)......as your car is also an LCI 335 built around the same time as mine it might be worth checking out the thread i started regarding the problem.

http://www.e90post.com/forums/showth...steering+fixed

Thanks for this. Your description seems VERY similar to my experience.

When I first drove the car on the motorway (immediately after collecting it) I felt that it was wandering slightly around the 'straight ahead' point. At the time I put this down to new tyres etc, but it's still there. It feels slightly 'floaty' when turning at speed.

Will ask the dealer to check it out.

[ss134]

Originally Posted by NFS

Thanks for this. Your description seems VERY similar to my experience.

When I first drove the car on the motorway (immediately after collecting it) I felt that it was wandering slightly around the 'straight ahead' point. At the time I put this down to new tyres etc, but it's still there. It feels slightly 'floaty' when turning at speed.

Will ask the dealer to check it out.

The first time i took it in they said there was nothing wrong with the car so make sure they physically check the steering pump......the car is MUCH better now, i hope that this is your problem. Let us know how you get on.

[F31-340i]

I have an E91 330d Touring - it has the electric towbar option so I think (not sure) the springs are slightly uprated over stock.

It has never understeered - it is now on 225M 19" wheels and feels more planted than on 18"s, but basically handles the same. Turn in very sharp.

It actually oversteered on a slippery road the other week - DSC was on and the car got into a proper sideways 20-30 deg slide requiring deliberate opposite lock - plus a full on very quick reversal required once I took the power off. It was quite surprising - I didn't think DSC would have let it get that far out of shape, but it was very slippery (I was going about 20 mph out of a left hander). Certainly no understeer anywhere to be seen!

[doughboy]

Originally Posted by NFS

Just want to resurrect this thread.

I've also noticed some undesireable handling characteristics on my e90 335i msport.

The main issue is the way the chassis responds to rapid steering input at higher speeds. If I turn the steering wheel sharply at motorway speeds, the car turns in rapidly, but there is then distinct feeling of weight shifting and then re-settling a moment later.

I'm guessing this is something to do with damper settings and rebound rates?

That was the high speed issue I had originally, the car doesn't turn initially it just 'yaws' around pivot point roughly where the armrest is and then 'yaws' back again as the suspension tries to return the body to its original position. If you gently wiggle the wheel left/right the car yaws like a pendulum with the front/rear going in opposite directions. TBH most cars do this and this high speed loss of control is one of the main things that ESP system are designed to prevent getting out of control, if you overdo it.

This is classic under damping where it cannot control the sudden vehicle movement at speed at the springs are too soft to minimise the roll in the first place, at low speeds this is not so apparent due to the much lower momentum involved.

But my 06 330i never did it and I don't expect that from a car with upgraded suspension.

Its fairly well known now I'd say that LCI cars are softened up to pander to the motoring press that said old M sports were too firm, and large numbers of corporate customers who want m sport looks but SE motorway munching comfort.

That's why we now have the BMW Performance suspension kits instead, but not available for the tourer.

The ARBs I fitted stabilised this quite significantly and the M3 bushes removed that 'dead' squidgy centre part of the steering.

Ultimately though it needs stiffer damping to really sort it out.

[doughboy]

Originally Posted by ///ajd

I have an E91 330d Touring - it has the electric towbar option so I think (not sure) the springs are slightly uprated over stock.

It has never understeered - it is now on 225M 19" wheels and feels more planted than on 18"s, but basically handles the same. Turn in very sharp.

It actually oversteered on a slippery road the other week - DSC was on and the car got into a proper sideways 20-30 deg slide requiring deliberate opposite lock - plus a full on very quick reversal required once I took the power off. It was quite surprising - I didn't think DSC would have let it get that far out of shape, but it was very slippery (I was going about 20 mph out of a left hander). Certainly no understeer anywhere to be seen!

Of course a RWD car in slippy conditions will oversteer!! Thats not really the point. It's about dry weather under power performance.

My point is that the car is set up with a large understeer tendancy under power, not coasting round corners, or on slippy rounadabouts where even my gran could get the back end out!!

Accelerating fairly briskly in say second out of a corner, in the dry, the front wheels just run wide of the steered direction, requiring more lock to stay on online. This is even more apparent on a track where under full throttle in second with half a turn of lock (arms crossed up!) the car still goes in a straight line!!

This is built in by BMW to stop people spinning the cars and is set by the ARB ratios.

Even the M3 is understeer biased as 99% of road cars are.

The Hartge ARBs transfom the car and make it beautifully balanced under power exiting corners, with just a hint of direction added from the front, the rear will help out and come round very slightly as if by magic, no drama, no scares.

The more throttle you add the more the car steers in the turned direction, very progressively and smoothly.

Of course this only happens when you are pressing on and wanting this to happen. Day to day the ARBs just make it an all round better car, the reduced roll reduces the sense of 'mass' and make the car feel a lot more nimble without affecting shock or bump damping.

[m1bjr]

Did it also relieve the loose feeling at high speeds on the motorway?
I find mine very very light, may just be a simple toe out issue to be honest but the tyres dont indicate anything odd and they string out pretty much zero.
So my guess is the extra compliance in the bushes isnt helping?

Is the bush swap a usual arm off-press out type job or will they require machining to take poly or the oem M3 items?

Cheers,
Steve

[zltm089]

I'm on standard RFTs bridget stones.....

Definitely, I've experienced oversteer with and without DSC....when pushing it...

but so far haven't really experienced any "major" understeer (maybe i'm not going fast enuff?)

But apparently, the 335i does understeer a lot! (coming from a BMW tuning specialist)

[SteveC]

Originally Posted by doughboy

Found an old thread on this is the old general section, no answers though, but wanted to raise it in the new tech section.

My new E91 335i m sport handles like a dog and understeers like mad. One's I test drove seemd very similar to my 330i E90 (short drives of course)

I know the tourers are slightly softer sprung and damped than the saloons (i think) and the rear ARB is 1mm less than the equivalent E90, so a possibly a bit more rear grip.

The body roll is pronouced, and the understeer under medium acceleration is frankly scary.

Travelling from Leek to Macclesfield on Friday (sunny and dry) coming round a left hand second gear bend, bit of gas on the exit and it just crossed the white line heading for the far curb, 1/4 a turn more lock did very little, cars coming the other way, off the gas then sudden grip and lurch back into my own lane....

Yesterday on a A road in between Stafford and Newport I've known for 20 years, sweeping left hander about 80 mph, I really felt like I had no control of the car at all, felt like it was floating round the bend, a mix of undulating body roll and what felt like varying front/rear grip, i felt sick after that. Looking in the eyes of drivers flashing by the other way thinking I (and them) could die here.....

My E90 was a gem compared to this, sharp turn in loads of front grip and the car felt like it turned under your owm backside.

I thought it was bad when brand new, but now after 500 miles its no better.

BUT - I did clobber a speed bump realy hard after 250 miles, but nothing seemed to change after that?

Any other ideas?

The E90 is an interesting chassis. Even with M-Sport suspension, which is quite firm, there's a fair degree of body roll when taking corners off throttle. Push that same chassis hard around the same bend and it has far greater composure and less roll. At the limit in the dry the car starts to lose grip about equally at both ends, so the line tends to widen, while the car remains neutral. Well past the limit and the car will oversteer. Unlike an M3. which transitions from neutral to oversteer quite gradually, the M Sport suspension tends to 'snap' into oversteer, so you need to catch the car, rather than simply rolling off lock in an M3. At this point you're going fast enough for the BMW salesman to involuntarily grab both seat bolsters and comment afterwards on the great roadholding!

RFTs are extemely sensitive to pressure changes. Add a couple of pounds too much and the car feels 'floaty' and unplanted, especially in high speed bends.

From your description, your car sounds quite extreme. The e90 (with properly adjusted RFTs) is a chassis you can lean on pretty hard, as long as there's power on. Your car seems to discourage any use of throttle through the bends so the car will tend to wallow more, exacerbating the situation

Before taking your car to BMW, make sure that your normal electronic driver aids are all engaged and that cold tyre pressures are exactly on the button for a lightly loaded car (you need to check this at home and use a foot pump to adjust). Then make sure your tyres are warm before evaluating its cornering ability. If the car still feels like you describe above then there's something clearly awry and the car needs to visit the dealership.

[doughboy]

Originally Posted by m1bjr

Did it also relieve the loose feeling at high speeds on the motorway?
I find mine very very light, may just be a simple toe out issue to be honest but the tyres dont indicate anything odd and they string out pretty much zero.
So my guess is the extra compliance in the bushes isnt helping?

Is the bush swap a usual arm off-press out type job or will they require machining to take poly or the oem M3 items?

Cheers,
Steve

Yep, the ARBs have all but removed the loose feeling at motorway speed, along with the M3 bushes have removed the 'yaw' you get with slight steering inputs from straight ahead.

Rear subframe bushes are push out items (by hand) (with the subframe dropped however)

Front bushes are factory pressed into the control arms and tension struts, so M3 arms are fitted whole. (4 arms = 2 per side = 8 bushes). There are 4 more rear arms to change to M3 items soon (2 each side) to get further slop out.

I've had 2 full alignments and was suprised to find that toe out is a standard setting on the E9x. I would have though this on a Front wheel drive but would expect zero or toe-in for a RWD.... any experts?

Originally Posted by SteveC

The E90 is an interesting chassis. Even with M-Sport suspension, which is quite firm, there's a fair degree of body roll when taking corners off throttle. Push that same chassis hard around the same bend and it has far greater composure and less roll.

From your description, your car sounds quite extreme. The e90 (with properly adjusted RFTs) is a chassis you can lean on pretty hard, as long as there's power on. Your car seems to discourage any use of throttle through the bends so the car will tend to wallow more, exacerbating the situation

My post was from March 09, but yes you're right with power-on, composure / roll are much better, this must be down to the rear suspension design. But the problem to me was the much greater increase in understeer tendency under power compared to my 06 pre LCI 330i, this caused the sudden power-off's need to avoid a collision which of course, mid corner, are never going to feel great in any car.

After 12 months with the car, I still find the high speed damping is too hard (sharp bumps etc) and the low speed damping is too soft (undulations, direction changes). Both these combine to make an overly harsh yet under controlled chassis. By under controlled, I mean the damping cannot control the mass of the vehicle over consecutive undulations or in sudden direction changes.

It just wasn't possible to get the rear into play to assist steering under power in the way that my old 330i would happily do. My 330i was a early saloon (06) and the 335i a 09 LCI tourer. Despite the tourers 75kg+ additional weight being nearly all bodyweight at the rear, BMW see fit to use a 1mm thinner ARB on the rear of tourers compared to the saloons whilst maintaining the same front ARB on both cars, thus putting more front bias in and increasing understeer on the tourer and being further exacerbated by the extra rear weight.

The Hartge ARBs, with much greater rear bias, have gone way over what the 330i offered and give (IMO) a beautifully sensitive rear bias that even under medium acceleration in second allows almost all lock to be wound off but maintain a gently curved trajectory using just the throttle and only a tiny tug on the wheel.

TBH after a KDS alignment the last place I want to take the car is to a bunch of technician box-tickers at a dealers. It was checked and I got the usual dopey answer - 'they all do that sir / we can't find anything wrong' etc etc

So I decided to fix it myself, and I have and then some. - with more to go on the springs damper front soon...

[zltm089]

Originally Posted by SteveC

The E90 is an interesting chassis. Even with M-Sport suspension, which is quite firm, there's a fair degree of body roll when taking corners off throttle. Push that same chassis hard around the same bend and it has far greater composure and less roll. At the limit in the dry the car starts to lose grip about equally at both ends, so the line tends to widen, while the car remains neutral. Well past the limit and the car will oversteer. Unlike an M3. which transitions from neutral to oversteer quite gradually, the M Sport suspension tends to 'snap' into oversteer, so you need to catch the car, rather than simply rolling off lock in an M3. At this point you're going fast enough for the BMW salesman to involuntarily grab both seat bolsters and comment afterwards on the great roadholding!

RFTs are extemely sensitive to pressure changes. Add a couple of pounds too much and the car feels 'floaty' and unplanted, especially in high speed bends.

absolutely spot on mate....d

Definitely, the word i was looking for...."snap" into oversteer.....

[m1bjr]

Originally Posted by doughboy

I've had 2 full alignments and was suprised to find that toe out is a standard setting on the E9x. I would have though this on a Front wheel drive but would expect zero or toe-in for a RWD.... any experts?

Thanks for the info, one more mod for the future.

Im no chassis expert, and this car is new to me, but I did a lot of work on my S2000 for track day play.
I took a small front toe out on that of about five min a side.
Helped the turn in and tyre life, as any toe in with the > -2deg camber will knock the edges off the tyres pretty fast.

Incidentally, I have used Chris Franklin at 'Centre Gravity Ltd' extensively.
Chris is a chassis expert, not the cheapest, but definately the best.

Also hear great things of 'Wheels In Motion' too.