Xoutpost.com - Strut tower brace question

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Quote:

Originally Posted by FSETH

StanF18, I think you may be talking about my post in a thread on options to increase the handling on a 4.8is. I may have made it sound worse than I originally meant to. I didn't mean to make anyone think that strapping in a strut brace would turn your X5 into a Ford Pinto death wagon. I think acitydweller did a better job of explaining what I was trying to say. A car is designed to crumple in an accident and tying both sides of the car together with a brace can alter how it absorbs the energy. I didn't mean to make it sound like you were going to die if you got into an accident with a strut brace.

Besides any structural safety issues, you would have to be pushin the X awefully hard to notice a difference. The X5 has a fairly rigid frame to begin with. I do not have a strut brace, but from what I have heard you really cant take full advantage of a strut brace unless you are tracking the car or driving really aggressivly on the open road. IMO it is engine jewelry for newer road cars and if there is any chance it can alter the way a car crumples and absorbs energy in an accident any slight performance benefits gained would not be worth it.

To give you an example of how far structural regidity has come in recent times read this.

On to the new E70 chassis. Chassis rigidity has been improved, it’s 15% higher now at 27,000Nm per degree. As a reference to show you how good this is, the old BMW M3 E30 race car fully equipped with a roll cage has 22,500Nm per degree chassis rigidity, that’s less than the new E70 2007 BMW X5!

According to this, if you subtract 15% off of the e70 the e53 chassis was still as strong, if not stronger, than the e30 M3 race car. I am not sure how much a strut brace would actually help.

OK, thanks for the insight. I'm obviously not going to track my E53, but I have quite a few "curvy" entrance and exit ramps on my daily commute, and I tend to take those fairly aggressively. I was thinking the strut brace might reduce my body lean? Maybe?:dunno:

Also, curious in which publication you saw the 15% chassis rigidity difference for the E53 vs. the E70. Thanks again.

Quote:

Originally Posted by StanF18

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Here is a link to one of the articles that compared the e70 chassis to the e30 M3.

http://paultan.org/archives/2006/11/...ive-in-athens/

If you Google/yahoo search BMW X5 15% more rigid or 15% stronger you will find more articles.

I am not sure how much a strut brace would help body roll in the first place. You would probably get better results with stiffer shocks/springs or stiffer sway bars, which I am not sure then even make for an X5.

I'll add my two cents to this discussion.

I doubt a single strut tower brace will do anything at all. A triangulate one might help at the extremes of how someone might drive an X5.

This topic has been extensively researched and argued about in the Porsche world. But the general concensus is that even on a street driven 911 coupe there is little value in a strut brace. On an open top Targa, there's some. It's on a modified 911 with R-compound tires and aggressive suspension that the right brace makes a difference. Research by several reputable shops has determined that a single brace across the top of the struts does virtually nothing. In fact it may actually hinder performance in certain instances. A triangulated brace works though. I've run my track 911 with and without the triangulated brace and can feel a difference in both the front end bite and the feedback in the steering wheel. I've taken out the triangulated pieces and just run the top brace across the top of the struts and frankly can't tell it's even there.

For a street driven X5 I think it's purely bling, unless you've gone the coilover suspension route or are driving your car at 10/10ths all the time.

Again, just my humble observations.

Quote:

Originally Posted by TowX

Research by several reputable shops has determined that a single brace across the top of the struts does virtually nothing.

That is a gross generalization remark. While it is probably true that a single brace across the top may do nothing to a specific car, but you can't say that it applies to all cars. Let's face it, the bean counters at all these manufacturers are not going to add anything to a car that does not need it, but yet you see more and more cars having a strut brace as standard equipment. Also, who's going to have the $$ to spend on research and development (proper measuring instruments, etc...)? The multi-billion dollars auto manufacturers, or the so call "reputable" shops?

Stan, I have Dinan struct tower brace on 2001 X5 4.4. I did not know whether it would make a difference before I put it on, for there were two groups of people as today. I can only tell you that I like mine. It seemed that the only way for you to find out is to give it a try like I did. Just my $.02

I have a Dinan Strut Brace and I have tracked my X5 a few times with the local BMW Car Club. The last time I tracked, I didn't go the second day due a mysterious "clunk" noise coming from the front when I loaded the front end in a turn. After much research, it turned out to be that the strut brace bolt holes became oval in shape and the "clunk" was the brace moving around in the tower brackets. So I would have to say it does have an effect if when driving agressively. I can also get it to pop on tightly curved on/off ramps.

Quote:

Originally Posted by dkl

I do agree that there are certain cars that adding a strut brace to may enhance performance. Especially older cars that don't have as stong of a chassis to begin with or track cars driven to the extreme. However, I think the main reason that there are some cars these days that come with the strut brace as standard equipment may be related more to a sales issue than a performance issue. If they can slap at low cost piece of metal across the engine to add some bling and it sells a few more cars because it makes their car look sportier than the competition then it was worth it. It does not cost much for the manufacturer to add their own strut brace to the car.

We have clearly hit a nerve with the strut brace issue. Strut braces, like drilled rotors, and other performance image accessories, may work at the limits of performance and otherwise are a visual indicator of an entheusiast owner. If a strut brace, CAI, bull bar, or other add on make you feel good, that's all that matters. If you can tell the difference in the performance of you car, even better. Enjoy it.

Just read this post when looking if anyone modified the Dinan brace to fit. Anyhow, there was an interesting question noted on whether or not it adversely might effect the car in the event of an accident. Good question. Since BMW never included one as OE it's fair to say that they didn't engineer it into a accident scenario. The only reason I say this is that the pull out load floor that is optional on X5's is quite heavy and rigid and WAS in fact specifically engineered by BMW to lift up in the event of a rear collision and not to go barreling into the backs of the rear seat passengers. Anyway, just food for thought.