I finally got around to installing my M3 Strut Tower Brace last week that I had sitting in my garage for quite a few weeks. As the kit doesn't come with installation instructions, I trawled the net for help. The only reviews or install DIYs I found were for E9x's but none for our E8x cars. Therefore, I thought that I would post up my feedback on the install for the M3 Strut Tower Brace kit for our 1 series cars.
I purchased the kit from HP Autowerkes and had it shipped to Australia.
For the install I referred to the following DIY guide and therefore all credit goes to Bill. For photos, refer to his DIY.
From my research, experience and comparison with Bill's DIY, there are 2 differences between the kits for the E9x and for the E8x.
1. The centre mount is modified to fit our E8x's. A standard mount will not fit.
2. For some reason not yet known to me, rather than being supplied with 8 x 13mm hex bolts (4 for each side) and 4 nuts to secure the aluminum struts to the centre mount and to the strut tower mounts, our kit from HPA is supplied with 4 x 13mm hex bolts and 4 x Allen bolts (presumably 2 for each side). There are no nuts in our kit.
The only reason I could come up with for why they might have done this is that the Allen bolt head is considerably more low profile then the standard 13mm hex bolt. When I installed the brace there was less than minimal clearance between the new brace bolts and the cowl/rear bulkhead cover. It is possible that in the E9x they have more room under the cowl and therefore don't need the smaller bolts.
I had 2 issues with the install.
1. The Allen bolts are considerably softer than the hex bolts and it is impossible to torque them to the specified 34nM without stripping the Allen hole. Ask me how I know... The hex bolts are fine however. I installed all bolts from the top. I put 1 Allen bolt right up close to the centre mount and 1 near the strut tower. This way, I had the "low" profile of the Allen bolt where the cowl would contact the strut whilst also having one of the properly torqued hex bolts at each end.
2. Even putting a smaller Allen bolt up near the centre mount did not give me enough clearance to re-install the cowl. In the process of attempting to re-install the cowl, the centre clip on the cowl snapped off. This allowed me to re-install the cowl. There do not appear to be any issues with the seal or anything else so I didn't worry too much. It just makes the future process of taking the cowl on and off much easier =P
At the time of this review, my E88, suspension-wise, was bone stock. If you have other suspension mods and/or an E82 instead of an E88 your experience may vary.
If it matters to you, the M3 strut brace, being made of aluminium is considerably lighter than the stock steel brace. If I had to guess, the stock brace weighs approximately 4-5kg and the M3 brace would come in under 2-2.5kg.
With the stock strut brace, each side is a separate brace and 'ties' only one of the strut towers to the firewall in the middle. The issue with this is that whilst they will reduce compression between one of the struts towers and the firewall, it doesn't protect from extension or twisting forces on that or the other strut. In addition to this, it bolts only to 1 of the 3 bolts on each strut tower. The M3 strut brace bolts onto all 3 struts (3 is better than 1, true story) and connects each side to the centre mount, thus tying both strut towers together. In theory, this should be much stiffer between the strut and the firewall, but also between each of the struts themselves. So how does this work in practice?
The answer is brilliantly. Right after installing the strut brace I took it for a short drive down to the shops and I could immediately feel the difference. The front end was much more sorted, feeling more planted to the ground. The steering is more direct and points right where you wanted to. This could be felt even with just changing lanes. There also feels to be significantly less body roll around corners.
Upon further testing on a spirited bay drive a couple days later, the brace really proved itself. Previously, the car was quite sloppy, especially on the limit during cornering. The feeling I would get when cornering hard is that the front end could break grip unexpectedly at any time and I'd go understeering into the nearest gutter, tree, pole, cliff, river etc. Since installing the brace I can now corner harder and with much more confidence due to the improved grip and handling. It also feels much easier to predict and control over and understeer much more easily.
This is an extremely worthwhile mod in my opinion and should be one of the first mods to consider when upgrading suspension on our non-M E8x models.
I hope that you guys find this review helpful and I am happy to take any feedback.