Comprehensive Steering Information Thread

[YoitsTmac]

Not enough to not trip up DSC. It's very mild difference - M to non M (pivot point to steering tie rod leverage point. About 5-10% IIRC)

[maupineda]

Does the coupe have the M3 or non-m e46 steering ratio in the knuckles? M3 slower might be better in this case.

From the data on this thread, the M coupe has the same knuckle ratio. The distance between the CA ball joint to the tie rod is 130mm on both.

[Bry5on]

From the data on this thread, the M coupe has the same knuckle ratio. The distance between the CA ball joint to the tie rod is 130mm on both.

Yeah I’m confused as most literature seems to have the m coupe at 13.7:1 (same as non-m ratio with 150mm/rotation rack) which is 126mm ball joint to tie rod from my scans. M3 is 130 as you’ve posted above. About 3% quicker on center

[chris719]

I just bought the black tag for my coupe. It will be interesting to see how it fares for road use with a more normal stocking wheel & tire setup

Did your original rack have a problem, or you just wanted something quicker? I noticed my roadster has a silver tag rack vs green on the coupe, which I guess they all do? All the pics of the part number 32137836844 have a silver tag.

[maupineda]

Did your original rack have a problem, or you just wanted something quicker? I noticed my roadster has a silver tag rack vs green on the coupe, which I guess they all do? All the pics of the part number 32137836844 have a silver tag.

Hi Chris, nothing wrong with my rack at 53k miles, I just want the quicker rack. The MCoupe is not bad, but I have a Tesla Model 3 which has much faster steering and I find it better for my liking, the M requires way more lock in the winding roads I go to.

people say it can get twitchy, but I don’t buy it. I used to race karts with 1:1 ratio.

[maupineda]

I got my rack this weekend and started installing it. The rack seems to be a high quality item, the exterior housing is almost a 1:1 replica of the OE design. Fitment is perfect and all clearances are same as the OE item

the only negative I have with it is the pinion dust cap, which is a very flimsy item, but the vendor I got it from was very nice and sent me an OE hard plastic one for a factory like setup.

Now the bad, which is nothing to do with the rack but rather bad luck as the top of the pinion seemed to have been damaged causing the intermediate shaft yoke to not slide in, so I had to remove the rack and I am in contact with Lucas and the vendor to define the next steps.

i will post photos of it and will document the details of the Z4M rack vs the black tag.

[02'topaz]

I’ve been running the LSPR black tag rack since last season and initially had no major issues other than the pulsation described by other users at full lock. This honestly didn’t affect the function of the car for me, but given the fix was a custom PS line from Lucas, I went ahead and installed it.

Attended my first track day since the new line went in, and had major issues with presumably boiling the fluid. After 1.5 laps on a track with short straights and lots of corners, began losing power steering. As the car cooled, things returned back to normal. Tried to push another lap just in case the system had not been bled properly, but same issue, with whining from the PS pump and near total loss of power steering.

Street driving is absolutely normal and the pulsation of course is gone. But I have traded a problem that didn’t bother me for a car that is no longer usable on track. Running D3 atf per Lucas’ recommendation and not Chf-11s.

Naturally one would think it’s time for a cooler, but why was this issue not present before with the same rack/OEM line at the same track on two occasions and only now with the new custom line?

PS reservoir was replaced when lines were refreshed so a clogged filter cannot be the issue.

Anyone else having this issue and have any insight on how to rectify other than potentially going back to the OEM line and just dealing with the pulsation (as long as it longterm doesn’t fry my pump).

Shitty way to start the season today but thankfully didn’t bin the car when losing PS completely into a hot corner…

[maupineda]

Thanks for sharing! Interesting what you describe.

[maupineda]

You can see the OE rack and the BT rack together, on the outside they look very similar, the casting quality is rather good with some areas showing more rugged surfaces.

i am glad to report that I will get a warranty replacement rack, which should fix the issue with the splines on mine



this is when I installed it before I had to take it off.



the Z4M rack does have limiters built into it, I need to measure how thick they are as I will need limiters on the BT or the tire will hit the inside of the wheel well, this is in part why the Z has less lock to lock turns (~2.8), basically it just does not use the full 150mm of total displacement. Some basic math.

1.5 turns or 75mm of track travel equals to 540degrees or 37.24 degrees at the wheels assuming a 14.5 steering ratio

According to BMW, the ratio of the Z4M coupe is 12.8:1, so at 1.5 turns the wheels are at 42.2 degrees, which is a lot more. Plus the Z has less space as it uses the smaller control arms from the 330 ZHP.

[maupineda]

I measured the distance from the outer most edge of the rack housing to the inner face at which the inner tie rod bottoms out, the black tag measures 24mm and the OE rack 19. Is tough to say the exact measurements as is impossible to line up the caliper perfectly every time, so let’s say is 5-6mm more on the BT, which means the limiters on the Z4M rack are between 5 to 6mm

i suppose the BT rack is the same as any other E46 as the Z4M’s 2.8 turns lock to lock must come from these built in limiters.

the rack displacement per turn is 50mm, the value below is 70 and change when centered. So, the Z4M rack itself is not faster than the CSL



The below image shows the depth to the surface that stops the inner tie rod



The same measurement on the Z4M rack is 19mm

[maupineda]

Received the replacement rack and finished the install. I took her out for a spin and impressions are good!

the steering feel is slightly clearer with some extra road texture coming through the wheel. The lack of spacers make the Z to have a much tighter turn circle (obviously) and I did not see any contact at full lock, but will still add the limiters when I get them next Monday.

out on the road it does take some time to adjust as at highway speeds very minor input on the wheel steers the car; on highway 17 to Santa Cruz she felt really alive and the whole car is very alert. I am liking it, the quick steering and the shorter drive ratio have transformed the car.

[maupineda]

I have added the SLR limiters, they are plastic and although I thought about aluminum limiters, I don’t want a metal part rubbing on the rack’s shaft as it may scratch it over time. Ideally you would want a slight press fit so they stay at the end of the shaft next to the tie rods, but for street application plastic will do, plus I never force the steering on lock. With the limiters I have 1.1 turns to either side which give the perception of a much quicker system, but I still have the OE turn radius as I keep the system same as OE with a total of 138-140mm of rack travel.

[moproblems]

I have added the SLR limiters, they are plastic and although I thought about aluminum limiters, I don’t want a metal part rubbing on the rack’s shaft as it may scratch it over time. Ideally you would want a slight press fit so they stay at the end of the shaft next to the tie rods, but for street application plastic will do, plus I never force the steering on lock. With the limiters I have 1.1 turns to either side which give the perception of a much quicker system, but I still have the OE turn radius as I keep the system same as OE with a total of 138-140mm of rack travel.

Just know the SLR limiters are generally a maintenance item for some. My buddy has had to replace them every season on his drift car as they come apart.

Unrelated, but does anyone still have shims on hand?

[maupineda]

Yes, I am aware of that and I can see it on drift cars where you jam the system lock to lock, but I am sure street or even track car won’t be an issue.

[maupineda]

Car is now aligned and everything is bottomed up. overall it is a nice upgrade, however, I had spoken to soon and there are some pulsations when you are close to 70% of the track travel to either side.

In the M3cutters forum there are some details about the fix LPSR came up with, it explains why 02'topaz is having heating issues. They are adding a secondary restrictor within the high pressure line, not sure where, but this would limit oil flow which will create extra heat and slow down cool down in heavy duty such as track or auto-x.

The pulsations are not bad, but are noticeable to any enthusiast, that said, the feel of it is so nice, that right now it is not enough of an issue to put me off. I still have my OE rack and can go back to it at anytime.

Maybe in my case the modified line is ok as I don't track the car, and the fix maybe ok for street and even canyon road usage (question mark on that one), however, I am not convinced the pulsations are a problem perse.

From what it was stated on the other forum, the pulsations come from swealing and contracting of the hose, I would need to look into this from a fluid dynamics point of view, and rather than a restrictor, a slight different diameter, or even a braided line design may also solve the issue, even a different length and routing can be alternatives to explore.

Since the pulsation does not happen during normal driving, I don't think this is an issue, however, I can see this being a problem if you auto-x the car as the rapid wheel movement will result in flow disturbance.