Technical Discussion: Strut Tower Cracking/Mushrooming [Archive] - BMW E46 330 ZHP For Sale Forum

slater

02-01-2016, 01:39 PM

i thought this was worth pursuing in the 'mechanical' forum... strut tower cracking/mushrooming seems to be happening, albeit randomly, on cars with aftermarket suspension and no reinforcement plates. the below is lifted from charlie's thread (i didn't want to clutter up said thread :) )... please discuss!

Been thinking of this for a while. If a strut bar provides rigidity and transfers weight/load from one strut tower to the other, I think the Engineers must be design the strut bars to fail at some point before the strut tower fails. I think that's why the BMWP strut bar fails in some cases. It fails to protect the strut tower.

In my case, the UUC Strut Barbarian (not properly designed) never failed, but my strut tower did (by cracking).

Food for thought.

good points, Dane.

i think the BMW reinforcement plates are a good idea as they distribute the load over a wide area. conversely, most strut tower bases concentrate the load right around the three mounting points. also, a bar that has a very flat/low attachment point would be best - the higher the attachment point, the higher the risk of cracking the strut tower at the inboard mounting point bolt. the mason engineering bars are a good example - look at these designs:

24127

24128

i think, though, that suspension choices have something to do with this as well. if your car is lowered, and especially if it's really low - i.e., very little suspension travel - your front suspension is going to be bottoming out much more often, and this kind of shock (ha) is going to be especially damaging to the strut towers... moreso if you don't have the reinforcement plates.

thoughts? do folks think the reinforcement plates are enough? are strut tower bars going to prevent cracking?

discuss! :party

Just_George

02-01-2016, 02:10 PM

I think we're over-thinking this - just my humble opinions:

1. The strut towers are "under engineered" on the E46 chassis, an obvious weak point. The reinforcement plates are a cheap, effective way to prevent (or remedy) the cracking problem and are a "must do" upgrade in my mind.

2. Strut bars aren't designed or intended to prevent the cracking or mushrooming of strut towers, nor do I believe they are designed to fail to protect the strut towers. Strut bars are intended to stiffen the front of the car where it is weakest, all to improve handling...it's filtered down from racing like so many other things. I'd be shocked if anyone engineering a strut bar gave a moments thought to how it would affect the strut tower cracking/mushrooming issue....

Food for thought (slightly off-topic): I read, from a respected and well-known BMW Tech Advisor, that strut bars may actually have a detrimental effect in an accident by transferring forces to the opposite side of the car (from point of impact), thus causing damage to the side of the vehicle that might otherwise have been unaffected. I can see where in theory that could happen - can't say I've actually heard of it happening, however.

slater

02-01-2016, 02:37 PM

I think we're over-thinking this - just my humble opinions:

1. The strut towers are "under engineered" on the E46 chassis, an obvious weak point. The reinforcement plates are a cheap, effective way to prevent (or remedy) the cracking problem and are a "must do" upgrade in my mind.

2. Strut bars aren't designed or intended to prevent the cracking or mushrooming of strut towers, nor do I believe they are designed to fail to protect the strut towers. Strut bars are intended to stiffen the front of the car where it is weakest, all to improve handling...it's filtered down from racing like so many other things. I'd be shocked if anyone engineering a strut bar gave a moments thought to how it would affect the strut tower cracking/mushrooming issue....

Food for thought (slightly off-topic): I read, from a respected and well-known BMW Tech Advisor, that strut bars may actually have a detrimental effect in an accident by transferring forces to the opposite side of the car (from point of impact), thus causing damage to the side of the vehicle that might otherwise have been unaffected. I can see where in theory that could happen - can't say I've actually heard of it happening, however.

rule #1 for me - i often over-think stuff. ;) when it comes to car problem solution engineering, i can't help but think and think and think about it.

1. agreed!

2. of course, i'm not saying they are. could they help? possibly, but the reinforcement plates are the right solution for that. my point was that it's entirely possible that the correct design of strut tower bar could aid in strengthening the top of the tower, whether it is a design goal of the manufacturer or not.

interesting about the crash aspect. hmmm.

danewilson77

02-01-2016, 02:41 PM

My statement was merely geared toward proving the BMWP strut bar engineering failure point.

Which makes me think the only way to safely use a manly strut bar (Mason Eng, UUC, etc...) is to pair it with the rough road kit.

Sent from an S6 Edge

slater

02-01-2016, 05:02 PM

My statement was merely geared toward proving the BMWP strut bar engineering failure point.

Which makes me think the only way to safely use a manly strut bar (Mason Eng, UUC, etc...) is to pair it with the rough road kit.

Sent from an S6 Edge

couldn't agree more. Rough Road Kit (RRK? :) i love acronyms) makes sense no matter how ya slice it.

ELCID86

02-01-2016, 05:16 PM

So I'll play. What's an RRK?

---
"ZHP is a garbage option anyway- just some cosmetic upgrades with a different cam and diff to claw back some of the performance lost fitting those hideous and heavy wheels. Any 330 with a 3.46 diff will smoke a ZHP every time. The whole Mafia thing reeks of childish behavior." - an e46fanatic

danewilson77

02-01-2016, 05:26 PM

So I'll play. What's an RRK?

Rough Road Kit.

---
"ZHP is a garbage option anyway- just some cosmetic upgrades with a different cam and diff to claw back some of the performance lost fitting those hideous and heavy wheels. Any 330 with a 3.46 diff will smoke a ZHP every time. The whole Mafia thing reeks of childish behavior." - an e46fanatic

couldn't agree more. Rough Road Kit (RRK? :) i love acronyms) makes sense no matter how ya slice it.

Sent from an S6 Edge

ELCID86

02-01-2016, 05:29 PM

I meant what is the rough road kit (but I'm lazy and used the acronym...)

---
"ZHP is a garbage option anyway- just some cosmetic upgrades with a different cam and diff to claw back some of the performance lost fitting those hideous and heavy wheels. Any 330 with a 3.46 diff will smoke a ZHP every time. The whole Mafia thing reeks of childish behavior." - an e46fanatic

BMWCurves

02-01-2016, 05:42 PM

I assume Peter means the reinforcement plates.

I was really surprised when I did my suspension refresh that the strut mounts aren't wider at the top to distribute load over a wider area. It really isn't surprising that the towers mushroom with the mount's design, especially since the tower's metal isn't very thick.

Pressure = force/area. Increasing surface area helps reduce pressure. Every E46 should get reinforcement plates to effectively thicken the metal of the tower and distribute force (note: I know that isn't exactly what's happening, but close enough).

slater

02-02-2016, 05:02 AM

I assume Peter means the reinforcement plates.

I was really surprised when I did my suspension refresh that the strut mounts aren't wider at the top to distribute load over a wider area. It really isn't surprising that the towers mushroom with the mount's design, especially since the tower's metal isn't very thick.

Pressure = force/area. Increasing surface area helps reduce pressure. Every E46 should get reinforcement plates to effectively thicken the metal of the tower and distribute force (note: I know that isn't exactly what's happening, but close enough).

yep, and... yep. :)

i think some of the aftermarket camber/caster plates (thinking of the BC ones that i've seen pics of) have even smaller diameter upper plates than the stock ones!

ELCID86

02-02-2016, 10:34 AM

slater

02-02-2016, 11:11 AM

Sockethead

02-02-2016, 11:51 AM

postingLink to this thread. A lot of good discussion on the same topic.

http://www.zhpmafia.com/forums/showthread.php?17346-This-is-why-shock-tower-reinforcement-plates-are-a-must