Strut Tower Woes
How about two posts in one day? After installing my front coilovers and swaybar today, I came across this:
Shame on me for not thinking about this in advance but now the problem is immediately obvious... my rebound adjustment is literally inaccessible with the OEM strut tower brace - an unacceptable outcome moving forward. As some of you know, I am preparing my 1 series to SCCA's STX class so while I know I will be replacing or modifying this brace, there are some rules to consider.
Quote:
SCCA Solo Rule 12.18: Strut Bar Definition
A transverse member connecting the upper or lower suspension mounting points at the front or rear of the car. Strut bars may be mounted only transversely across the car from upper left to upper right suspension mounting point and from lower left to lower right suspension mounting point. A two-point strut bar fastens only at the left and right suspension pointing points. A triangulated strut bar has a third area of attachment at the chassis (e.g., at the firewall/bulkhead). All connections to the vehicle must be bolted. No connection point to the chassis can be welded.
SCCA Solo Rule 14.2 G: Street Touring Strut Bar Rules
Strut bars per Section 12.18 are permitted with all types of suspension, subject to the following constraints:
1. A 2-point strut bar may be added, removed, modified, or substituted,
but only with another 2-point strut bar.
2. A triangulated (3-point) strut bar may be removed, modified, or substituted; substitution may be with either a triangulated or a 2-point strut bar. The connection to the chassis (e.g., firewall, bulkhead) must be in the standard location.
3. Lower suspension braces must be attached to the lower suspension
pickup point locations on the chassis within 2” (50.8mm) in any direction of the actual suspension attachment to the chassis.
4. Except for standard parts, no connections to other components are permitted. Additional holes may be drilled for mounting bolts. Only “bolt-on” attachment is permitted.
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After reading the rules, it was apparent that my options are wide open within class rules to either modify this bar or replace it with a new bar, either a traditional tower to tower "2 point" style bar that is typical on an E36/E46 or another "3 point" bar that triangulates with the firewall. After doing some reading, anecdotally it appears that most people believe there is a real advantage to maintaining the triangulation and intuitively this makes sense, so I will restrict my options to that.
My requirements for a strut tower brace:
1) 3-point style
2) 3-bolt/full circle mounting to each strut tower
3) Complete access to the top of the shock
Options I identified:
1)
Mason Engineering (Steel $550, Aluminum $600)
2)
HPA Custom / M3 Based ($452)
3)
OEM BMW 1M ($248)
The Mason engineering option looks to be a robust and well engineered solution and is a contender, but at $600 for the aluminum version I think that's well above what I am prepared to spend for somewhat of a trivial upgrade.
As far as I can tell, the HPA solution was introduced before the 1M part was available off the shelf, but now that it has, I have a hard time seeing the value in paying $452. It uses the same strut tower mounts and caps that are used in the 1M package for about $125, so the remaining $327 is for the two "arms" and the attachment point to the firewall.
I notice that the HPA solution has slots in the arms which is somewhat similar to the slots in the end of the 1M arms, I’d really prefer if both options had drilled holes. I am not sure this is an issue, but from a design perspective I would prefer to have fixed holes even if only for "theoretical" purposes. On the other hand - the firewall mount looks to be quite a bit more robust on the HPA/E9X M3 than the 1M OEM option, but I am not sure that this is necessary, and in addition it may require cutting some plastic, etc for installation per their website.
On that basis, I am going to proceed with the 1M solution for my car for the combination of OEM fit/finish and price effectiveness.
1M Strut Tower Brace Complete Part list:
Strut Tower Bar Driver’s Side - 51618055091
Strut Tower Bar Passenger’s Side - 51618055092
Strut Bar Driver’s Side - 51618051973
Strut Bar Passenger Side - 51618051974
Firewall Bolt - 07146954965
Mounting Stud (Qty 4) - 51717898374
Locknut (Qty 4) - 31316769731
I priced the whole kit at ECS tuning at $175.59 excluding the caps to cover the strut towers which are just extra weight and something I have to remove if I want to adjust my shocks. They are however super inexpensive if you would prefer to have them.
Ordering parts this week, keep everybody tuned!
Cheers,
Mark