Front suspension install question.....

Had a question on the front strut/mount install as I wanted to double check to be sure I did this correctly when I installed my Koni's, new springs and M3 offset strut mounts.

Between the spring perch and the strut mount itself there is a large washer. When you steer the spring perch rotates but the strut mount does not. The washer is the turning point along with the bearing inside of the strut mount for the struts rod itself.

On some BMWs it is just a plain flat washer on others it is flat on one side and convex on the other. On the cars with the convex washer which way is the convex half of the washer facing.... up or down? I couldn't tell from the ETK what its orientation was. From holding the parts it appeared to make the most sense with the convex half facing UP toward the strut mount. This would limit friction when you steer as the convex section of the washer would be resting on the strut mounts bearing itself and would pivot along with it.

However at the same time this means all the weight of the front of the car is resting on that bearing as the convex part fits inside the base of the strut mount. If the washer was installed with the convex half pointing down the flat side would rest against the bottom of the strut mount itself and that is what would support the cars weight. But steering here would have the friction of either the washer sliding against the bottom of the strut mount or at the convex part of the washer rubbing against the spring perch.

I didn't disassemble my cars stock strut/mounts so I couldn't go by that. But I swapped strut mounts on a 318ti (over to M3 type) a week or two ago and it had flat washers so I don't think my stock strut/mounts would tell me anything.

Thanks,

Shawn

Which parts in the following pics are you talking about?

Shawn,

Item 11 in Ron's lower picture was installed convex side down (flat side up) to mate with the angle on the top of the stock strut rod. This was discovered during the swap from oem struts to Koni d/a inserts for the 2001 M Rdstr.
The Konis I installed in their place did not have the matching angle but I still installed the original spacer convex side down.

Ron,

The washer I'm talking about in your middle picture is item # 7 shown as part# 31 33 2 227 342.

That part out of my brothers Ti was just a big flat washer. The part I received from Paul (with that part number) has the flat side, convex side washer. As shown on your diagram it goes right below the dust collar for the bearings which fit up into the bearing. That diagram doesn't show the orientation of #7 though.

I did some more searching online and this part is mentioned in the H&R Coilover install directions located here down at the bottom of the page:

http://bmw-m.net/TechProc/index.htm

Mentioned in step 6 of the front suspension install. He says concave but I think he really meant convex.

Thanks,

Shawn

Randy,

Thanks, the part you are talking about is below the spring perch though correct? That isn't the part I mean.

Shawn

Originally posted by Randy Forbes
Shawn,

Item 11 in Ron's lower picture was installed convex side down (flat side up) to mate with the angle on the top of the stock strut rod.

The one in my car is concave on the bottom, flat on the top.

Originally posted by Shawn Fogg
Ron,
The washer I'm talking about in your middle picture is item # 7 shown as part# 31 33 2 227 342.

On my car ('01 M coupe), item #7 convex side was and is facing up and the concave side was facing down.

Ron,

"On my car ('01 M coupe), item #7 convex side was and is facing up and the concave side was facing down."

Thank you. That is how I installed it as it looked to make the most sense that way but I wanted to double check that.

Thanks,

Shawn

Originally posted by Ron Stygar
The one in my car is concave on the bottom, flat on the top.

I always get those two mixed up!

Randy,

"I always get those two mixed up!"

Think of concave as conCAVE... and picture sort of what a mouth of a cave would look like from the side. Wider/taller at the edges and shrinking down to have the least width in the middle.

Shawn

Originally Posted by Shawn Fogg

Randy,

"I always get those two mixed up!"

Think of concave as conCAVE... and picture sort of what a mouth of a cave would look like from the side. Wider/taller at the edges and shrinking down to have the least width in the middle.

Shawn

Can I reopen this one? Ron seems to be saying that on his M Coupe, the washer in question (Item #7, Part# 31 33 2 227 342) is convex ( has a bump) on the top and is concave (has a dimple) on the bottom. I, and it seems Shawn did as well, recieved a BMW washer that is flat on one side and convex (has a bump) on the other. I used it with the bump up and can't see that it would or could make a difference that the bottom is flat. Opinions? Also, why would there have been a completely flat one and what would happen if you used it? I mean I'm all for percission but I did not see in this application the difference it would make?

Shawn,
The washer can't possibly move, rub or slide anywhere; when you tighten the upper shock bolt everything is clamped together and the whole assembly rotates on the bearing in the upper support.

Originally Posted by HaqDeluxe

Can I reopen this one? Ron seems to be saying that on his M Coupe, the washer in question (Item #7, Part# 31 33 2 227 342) is convex ( has a bump) on the top and is concave (has a dimple) on the bottom. I, and it seems Shawn did as well, recieved a BMW washer that is flat on one side and convex (has a bump) on the other. I used it with the bump up and can't see that it would or could make a difference that the bottom is flat. Opinions? Also, why would there have been a completely flat one and what would happen if you used it? I mean I'm all for percission but I did not see in this application the difference it would make?

Read again.

Part number 31 33 2 227 342, #7 in the middle diagram is Convex and flat. Goes in Convex up.

Part number 31 33 2 129 977, #11 in the lower diagram is CONCAVE and flat. Concave goes down.

Two different parts.

Originally Posted by Pinecone

Read again.

Part number 31 33 2 227 342, #7 in the middle diagram is Convex and flat. Goes in Convex up.

Part number 31 33 2 129 977, #11 in the lower diagram is CONCAVE and flat. Concave goes down.

Two different parts.

Originally Posted by Ron Stygar Post #7

On my car ('01 M coupe), item #7 convex side was and is facing up and the concave side was facing down.

Uh Pinecone.. I did read Ron's post again and it still seems to say that his washer is concave on the bottom! While the washer Shawn and I recieved as BMW parts (31 33 2 227 342) are flat on the bottom!

So,is it safe to say that when I replace my struts, and I want all new suspension bits (just for precaution), I can just use Ron's guide and buy items 1-12 in the first pic or 1-16 in the second pic (which one)? It looks that way. And if that's the case, does someone (ahem: Ron) have a exploded view of the rear? Thanks in advance!

Originally Posted by HaqDeluxe

Can I reopen this one? Ron seems to be saying that on his M Coupe, the washer in question (Item #7, Part# 31 33 2 227 342) is convex ( has a bump) on the top and is concave (has a dimple) on the bottom. I, and it seems Shawn did as well, recieved a BMW washer that is flat on one side and convex (has a bump) on the other. I used it with the bump up and can't see that it would or could make a difference that the bottom is flat. Opinions? Also, why would there have been a completely flat one and what would happen if you used it? I mean I'm all for percission but I did not see in this application the difference it would make?

The convex concave washer is shown in the pic.
Since they were $10.00 each I didn't replace them like I normally would. I ordered one today to see what I get.

Originally Posted by Ldogdotcom

And if that's the case, does someone (ahem: Ron) have a exploded view of the rear? Thanks in advance!

Not yet.

Originally Posted by Ron Stygar

The convex concave washer is shown in the pic.
Since they were $10.00 each I didn't replace them like I normally would. I ordered one today to see what I get.

Please Lord.. Let Ron recieve the same part I did.. I really don't want to have to take those things apart!

Since the center of the bearing in the guide support protrudes or extends down a fraction more than the outside and the dust cover seems to mainly rest on that point, which in turn sits on the washer in question.. other than a fraction more clearance, it seems that a flat washer would work here (flat side to the dust cover). I also feel that a flat bottom will make no difference.

Originally Posted by HaqDeluxe

Please Lord.. Let Ron recieve the same part I did.. I really don't want to have to take those things apart!

Since the center of the bearing in the guide support protrudes or extends down a fraction more than the outside and the dust cover seems to mainly rest on that point, which in turn sits on the washer in question.. other than a fraction more clearance, it seems that a flat washer would work here (flat side to the dust cover). I also feel that a flat bottom will make no difference.

The ti along with the non M E36's use the flat washer.
I assume that you didn't take a picture of your flat washer.
I'll order a flat one tomorrow. 31 33 1 116 983 $0.64 retail.

Originally Posted by HaqDeluxe

Uh Pinecone.. I did read Ron's post again and it still seems to say that his washer is concave on the bottom! While the washer Shawn and I recieved as BMW parts (31 33 2 227 342) are flat on the bottom!

OK, I see what you are saying. The install the convex side the same way as Ron did.

Originally Posted by Pinecone

OK, I see what you are saying. The install the convex side the same way as Ron did.

I installed this part with the convex side up and the flat side down. It was a new washer and other than the original being.. well.. original, it looked the same. Ron's (from his picture) sure looks different. In fact his looks like it should cost ten bucks!

I have had no issues with my front suspension using the washer supplied. I can tell you that 16lb is just a bit beyond snug if you are tightning the strut nut with a shade tree set-up. the old deep socket and vice grips! I recently replaced my transmission mounts and was quickly reminded of this when I torqued those to the recommended 16lb with a proper wrench.

Originally Posted by HaqDeluxe

I have had no issues with my front suspension using the washer supplied. I can tell you that 16lb is just a bit beyond snug if you are tightning the strut nut with a shade tree set-up. the old deep socket and vice grips! I recently replaced my transmission mounts and was quickly reminded of this when I torqued those to the recommended 16lb with a proper wrench.

Where did you get the 16lb spec. from?
For the top M14 nut, BMW recommends 64Nm and Koni recommends 80Nm for their nut.
Didn't a couple of these come apart for some while driving?

Originally Posted by Ron Stygar

Where did you get the 16lb spec. from?
For the top M14 nut, BMW recommends 64Nm and Koni recommends 80Nm for their nut.
Didn't a couple of these come apart for some while driving?

My mistake Ron.. 22Nm (16lb) for the three (3) nuts that attach the strut hat to the strut tower. I used 45Nm (33lb) for the strut nut (the one that holds the strut hat on) as per my Bentley manual. Being a self locking nut, it shouldn't back off regardless of the torque, I would thing. Might lead to some rattle and premature wear of the strut hat bearings though.