Yet another alignment thread. [Pics of steering rack]
edit: Update in fifth post
I apologize for starting yet another alignment thread. But I have a small problem.
Before the alignment, my specs were this:
Front: camber -1°10' per side. 0°08' total toe in, caster: 4°55'
rear: camber -1°30' per side. 0°14' total toe in
The problem was that the car was really twitchy at highway speeds. Driving 75mph in a straight line was already a serious job. The car simply didn't drive nice.
What I thought was: I need more camber, and slightly more toe in. The camber was way too low imo.
So I decided to buy a pair of eccentric Z4M FCAB's to get more positive caster. So I went for a new alignment and the results were like this:
Front: Camber LEFT: -1°15' RIGHT: -0°49'. 0°14 Total toe in, caster: 6°
camber left was at his minimum and right at his max, so I cannot get both at the same values. Apparently the eccentric bushings made a greater impact on the camber than I thought. Is this a huge deal? Because the right camber looks kinda low. It's still within OEM specs, but OEM specs are **** imo.
Rear: same, but the alignment tech made a mistake. He also took the values when my ass was sitting in the car, so the computer could calculate how much more camber it was gonna get with my weight inside the car, but he confused the 2 values (with/without my ass), so instead of -1°30', the rear left now has -1°50'. Not a huge difference, but getting close to -2°, isn't that bad for the rear tires?
To the point
After these new specs, the car tracks more confident at higher speeds. Its still slightly twitchy, but lets say that driving 95mph feels about the same as 75mph felt before. So I see this as a win. But I do feel that there is still something off. When I drive high speeds and want to manouver or change lanes, it still feels like something is off, but I cannot say what (front/rear). Maybe anyone can chip in and advice on these specs?
Oh, right, my car has following mods
- Bilstein B12 (with Eibach pro kit springs)
- H&R sways, both on soft
- Z4M FCAB (powerflex 80A before, but is now irrelevant)
- Strongflex 80A RTAB and subframe bushings
- All other rear bushings recently replaced with Lemförder OEM-style rubber
- 4x Michelin PS4. 225 45 17 front, 245 40 17 rear
ALL suspension and steering parts have been replaced over the past 3 years. Steering rack, steering guibo, FCA's, steering rods, ... The only thing which MIGHT have some slight slack, is the rear sway bar endlinks, which I intend to replace in the future to adjustables.
Kind regards, and thank you (once again :) )
Take the car to a reputable alignment shop.
If you've read my posts on other threads, you know I'm going to say-
the improvement in handling was due to the increase in front toe in.
Below is all predicated that we're talking about an E46.
Camber has very little effect on straight- line handling, especially on smooth roads.
As it goes up, the car's tendency to follow pavement grooves increases, and its ultimate
cornering grip goes up, but it is otherwise pretty transparent.
And tire wear is affected only slightly. In fact, if you like some toe- in for stability
then a little negative camber can actually balance that out.
Toe has a big effect, especially when your tires are all almost at zero toe.
Increasing toe- in in the range of 0 to .25 degrees you'll feel as increasing stability,
resistance to side winds, and predictiability.
The trade off will be that you start to lose responsiveness- it'll take an increasing amount of
wheel movement to get the car to turn 'right now'.
Depending on your tires, toe over about .25 degrees will increase wear at an exponential rate, AND
the car will feel 'numb'
Caster also has a big role in feel, and also in cornering grip, but with fewer tire costs.
The more caster, the more stable the car feels, the higher steering effort there is, and often,
the more cornering grip the front has, from the camber gain that you ... gain.
It is also very hard to adjust on the front of a stock BMW without plates, bending things, or moving suspension points.
Most of this is based on tires being compliant- 'rubbery', if you will. They distort significantly in outside diameter
with the car's weight, and also laterally when you corner. Since they are really very dynamic springs as you are driving,
a small amount of 'non parallel' movement from toe- in is absorbed by 'springing' the sidewall of the tire.
So wear, at first, doesn't go up, as the tire deflects slightly. It also pre- loads against the other tire, so that as weight
transfers from side to side, the car tends to 'self correct' against outside loads.
Heat DOES go up, as does rolling resistance, but not enough to matter for our purposes.
The other upshot of all this is, that since the tire's a conforming spring, precise alignment becomes less and less important
as you approach exact accuracy- that last tenth of a degree of camber might only be felt on a racetrack at full cornering load,
and then ONLY as a 'the front goes away first' sensation.
So since toe is such a powerful tuning tool, if everything else is within the BMW spec, it's quick and easy to adjust the car
In fact, I keep less toe on for commuting, and will toe the car in a little bit more when I know we'll be on long freeway trips, when there's very little
actual driving to be done, just so it's easier to be lazy....
way more words than you needed,
TobyB, thanks for the reply. Good post, but about the toe, I'm not 100% sure. When I put in the Z4M bushings, my front toe-in had a total of somewhere around 0°30' - 40'. So lots of toe in, but it didn't feel stable. It felt like garbage. The only thing that isn't 100% cleat to me is the thing you said about tires. I might run it into google translate, as I'm sure its because of my English that I don't understand it completely :P
So, as a matter of fact, all of this "unstable handling/steering" geometry issues started AFTER I replaced my steering rack. When I bought the car, it drove just fine, but after experiencing some play on my steering rack, I bought a new aftermarket TRW. TRW was a good choice I thought. After the first alignment it didn't feel alright, then someone recommended me to use slightly more agressive alignment specs, also drove like poop. Then we're where we are now. So there are 3 people in this entire country which actually have experience with alignments on E46's, 2 of them build cars for the track and even have customers coming from foreign countries just to get their alignments and performance mods done. I explained my situation and one of them said he had an E46 with a similar problem, only worse. Despite having "good" alignment specs, and done a complete suspension (bushings) overhaul, his car still drove like ****. As a last resort he replaced the steering rack, and all problems were solved.
I have no idea what could go wrong with a steering rack other than play or leaks. But then again: my issues DID start after replacing my rack, but it's a brand new one. Could it be that TRW's have maybe a slightly different "setting"? I still have a spare one from a 330iA I stripped about a year ago, but that's a lot of work, just to see if the problem is resolved afterwards, and having to pay for yet another alignment.
This morning I drove 1 hour to a BMW specialist. A guy who owns a shop that is focussed mainly on BMW performance upgrades. Most of his customers drive track on a competitive level. He has done hundreds of E46's.
I explained to him my problem, that after replacing the steering rack 3 years ago, all the troubles began. Regardless what alignment specs I used, something was off. I thought it was just bad specs, but I'm starting to think it's something else now. He said he had a similar problem with his wife's E46. Complete suspension overhaul, and the steering still felt really weird. He replaced the steering rack ***61664; problem solved.
I told him what alignment specs I used the last alignment, and when he test drove my car, he said that the car felt waaay to twitchy and unstable for those specific specs. It was driveable, but it didn't drive like and E46 is supposed to drive. He also suggested I swapped out the steering rack. I told him mine was only 3 years old, but when I said that it started afterwards, he definitely thought that is the problem. But it's a new one, I said. He replied that it was a rebuilt one, as I had to turn in my old one. And that there could be a slight chance that it was not rebuilt correctly, maybe because it was a Monday morning and the tech was still drunk or something, and that the teeth from the middle position had too much wear but that it was neglected. Just an example of what could be.
I find this hard to believe, as there are (almost) no steering rack issues known for the E46, but he claimed that he had few customers who requested a new steering rack, while he test drove the car before, and found nothing odd about it. Yet he replaced the steering rack and said that it drove like a completely different (new) car. Also, his E46 track car has toe OUT in front, and 0 toe in the rear, and it drives as stable as an E46 can drive. I said that my E46 with these specs drove even worse than it does now, on which he said that this is normal. If there is a problem somewhere, and you use more toe in, you are camouflage the problem, the more toe out, the more the problem gets "exposed".
The issue I have now is: I still have a steering rack from a 330iA with 300k km lying around. Should I swap that and try it, or should I just go for a new one? Save money but having the risk of having to do it twice, or spend money and do it right?
Dumb question. Is there any chance the RTAB's are bad and your car is dog legging under driving and not on the alignment machine?
What’s the condition of the tie rods and front roll bar links? If the problem started when you installed a “new” rack, then I think the problem is likely the rack. The tech is correct when he stated you installed a rebuilt rack. From what company did you buy the rack?
It's a TRW rack, and I thought TRW was somewhat quality. Tie rods and anti roll bar links are both new, and have 0 play on them.
Yet another alignment thread. [update: Steering rack issue?]
ZF bought TRW’s rack business. I’d contact the company and see if they’ll ship you a replacement.
Having taken apart a few (non e46) racks, there IS at least one way to get a rack wrong.
There's a preload spring and slider (or other arrangement to provide a controlled pressure) to keep the pinion
and rack tight. If that's way wrong, I could see it making a mess of handling, as the rack will deflect at the
driver's side, change the effective toe, and off you go.
I'd trust your expert- try ZF to see if they'll give you help, and then swap the rack for the used one.
It's easy to inspect the rack itself (pull the driver's boot, turn full left) and if it looks ok, try it.
I hadn't heard of this either, but it's certainly possible.
Although the rack is 3 years old and has 50k km on it, I doubt they will send me a replacement, but I'll try and contact them anyways and see what they say. If I pull the boot and turn left, what is it I should look for?
Thanks for your replies guys :)
The rack gears come out of the rack- if anything is seriously wrong (like it's full of water and rusty, etc) you'll catch that.
What you want to see is relatively clean (hopefully, greased) gear teeth with little wear, and no ugly wear or galling on the side opposite the teeth that slides against the 'pretensioner'
Beyond that, if it feels good, it's probably good. They really don't go bad very often if the boots are intact.
hth, and good luck,
About the steering rack: I don't think I have the experience to tell what is normal wear and what is not, but I'll give it a visual inspection :)
Agreed, they rarely go bad, but then again, mine is :( And what I noticed over the years is that an E46 don't need much play to create unstable handling and vibrations, compared to any other car
Well ZF isn't really helping me out here, as they are pointing the issue towards the suspension of my car ...
I'm baffled as to why you're still having issues. Would love to say it's the steering rack, albeit just about all of the issues we've had with those usually is a leak. I have yet to see one with a mechanical issue after a rebuild. But it's possible.
There are additional alignment measurements that are not normally performed, but most alignment machines have the capability to do so.
1) Toe angle difference: (Toe out on turns)
2) Geometrical axis deviation: (Setback)
#1 is accomplished by turning the front wheels 20° to each side and measure the difference displayed on the screen.
#2 Is a value read out after the alignment is complete. It measures the theoretical centerline of the front axle and the rear axle. Then if the center to center (C/C ) has a vast difference the car can pull to one side.
Rather that type your alignment results, can I ask that you scan the printout and post it here? Perhaps I can see something??
If you care to get another alignment check, I would be very curious as to what the two areas (additional measurements) come about as.
Is the shop thats performing the wheel alignment weighting the car down and measuring the ride heights and making any corrections BEFORE turning any wrenches?
I've posted an image and a link to what I mention. This is only for a plain 325 sedan. (Saloon) You will need to pick your exact car to get accurate data.
I'll see if I still have the printouts of the alignments. IIRC the setback was as close to 0 as it could be. The measurement at 20° was not done.
I put my ass in the driver seat before making adjustments, so the computer could calculate how much of a difference there is in camber with my weight in it. I dunno how to properly explain it in English, but I think you know what I mean.
I do agree that E46 with steering rack issues are never heard of, but it all started after replacing the rack, and when someone else told me that his E46 drove 100 times better after replacing the rack, then indeed it could be that this is the issue.
What if those measurements at 20° are off? What could that be or what handling issues would that cause?
One step at a time...
If your car is very modified and the suspension is lowered of track duty, we do alignments with the drivers weight in the seat and a 1/2 a tank of fuel.
"Normal" BMW alignments do not need the driver in the seat. The engineers know this and the specification is designed to allow for the alignment being done with the car with no driver/passengers.
If the toe angle difference is out of specification, this can point to many things, unfortunately.
Such as one tie rod run all the way in and the other side all the way out. The steering rack not being center. The control arm rear mount points (FCAB) not straight and/or bent control arms. There's more but if..... the measurement is no good, I'd start there.
You still haven't answered my question; Is the car lowered?
If not, is the alignment shop weighting the car and measuring the ride height?
Sounds harsh but all but the very newest BMW dealer KDS machines cannot perform a correct alignment without first putting weight into the car and then measuring/correcting the ride height BEFORE any wrench is turned.
I can't emphasize this enough. Can a wheel alignment be done by just pulling the car onto the rack, setting the tire pressure and making adjustments, why yes. It's not correct, BMW has an insane way of doing a wheel alignment and we adhere to it.
Take your case; If it were here in my shop, how can I properly measure setback & toe out on turns if the car is lower or higher that the specification data? I'd be working with false data.
(Tantamount to using engine measurements for a M54B25 when I'm working on a M54B30)
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