The dynamics and the point of fitting a strut brace?
Discussion
kambites said:
It's not the fact that it's bolted, it's the fact that the bolt goes through a slot which is clearly designed to allow the thing to be adjusted in the direction that it's meant to be rigid.
Which, of course, it has to in order to fit across a range of dimensions within production tolerances. If it's using the strut upper mounts, then they need to be movable relative to the shell, too, to allow adjustment of the geometry.TooMany2cvs said:
Which, of course, it has to in order to fit across a range of dimensions within production tolerances. If it's using the strut upper mounts, then they need to be movable relative to the shell, too, to allow adjustment of the geometry.
True, although I suppose you could do that with some kind of screw based adjustment. I've no idea whether camber is adjustable on an M3 but it looks like the bar bolts to the shell to me. It'd be fascinating to take some of these things and actually apply a controlled tension to them to see how they behave.
Edited by kambites on Tuesday 31st March 09:19
Hoofy said:
That strut brace is a work of art!
I have one in the Volvo as standard. I can't decide if it's because it improves the handling above that of a normal saloon car or because Volvo thought the handling was s
t on the S60 that they had to throw one in. I suppose I could remove it to see what would happen.
Haha, aparently that is there to stop the engine taking off somewhere uptowards the pax compartment during a crash.I have one in the Volvo as standard. I can't decide if it's because it improves the handling above that of a normal saloon car or because Volvo thought the handling was s
t on the S60 that they had to throw one in. I suppose I could remove it to see what would happen.On that basis I decided to put some washers over the rubber bushes and bolt that solid fu***er down. Placebo effect I'm sure, and on the road didn't notice much difference; but under heavy lateral load with the sticky AD08s on I'm sure there was an actual difference. As said, all placebo probably! But for the cost of some washers the placebo effect alone was worth it!
Btw, a well sorted S60 can harrass far more capable machinery
(but agreed, it's a bit like a wounded elephant chasing a balerina; sure the elephant can keep up but the balerina looks much more elegant doing it! Have I won a prise for worst metaphor ever?)kambites said:
The OEM one appears to look like this:
I've no idea if there's adjustment slots under there (I'd guess there is) but those two large headed luck nuts look able to provide a rather higher clamping load than a single small allen bolt.
I don't recall them being slotted, however there was a good amount freedom in the fit of the nuts and bolts. This was purely to allow for some natural variation in the manufacturing process, and not intended as adjustment, or to be able to preload the turrets.I've no idea if there's adjustment slots under there (I'd guess there is) but those two large headed luck nuts look able to provide a rather higher clamping load than a single small allen bolt.
Likewise, the only reason for the bolts (I forget if there were nuts underneath, however I think there weren't) is to allow the brace bar to be removed for servicing ..... the bar needs to be removed to remove the cover to access the coil packs and plugs for example.
kambites said:
I rather suspect that the bolt would sheer before you could actually get it to apply enough pressure, those little Allen bolts are pretty pathetic; you are of course right though, if it was moving you'd be able to see it.
Looking at that bar I suspect the bar flexes before the bolt sheers 
graham22 said:
I've heard stories before of insurance companies not liking strut braces for reasons of transferring impact/impact damage to the other side of the car too.
Funny, I've struggled to explain it to most insurers, you tell them you have a strut brace and they're like "er.. whats that?" and you tell them it goes between the suspension towers and they're like "oh so a suspension modification" and then you're like "well technically it's a chassis modification" *sigh*.I got one of these free with the car, do we reckon it's man enough?
Has to be removed to get the plenum off which has to be got off to get at the plugs but it's not hard to take off
Edited by scarble on Tuesday 31st March 09:55
VonSenger said:
wow, lots of information here! Thanks. I think the consensus is fit a good one and it cant do any harm.
I had an mx5 and considered what you are considering. But talking to a chap at a track day he mentioned that if you have a minor off and sustain damage, a strut bar linking your towers increases the opportunity to bugger up more areas of your car due to the loads and stresses being shared around. Make sense I suppose.
Just a thought really.
I've often wondered how much movement there actually is between the unbraced strut towers. Imagined a brace attached loosely so that any movement along the brace makes a record. Maybe a piece of paper stuck to one surface and a pencil glued to the brace (or something less Heath-Robinson). Hard to do in practice but it would be interesting to see whether we are talking about less than one or more than ten millimetres.
karma mechanic said:
I've often wondered how much movement there actually is between the unbraced strut towers. Imagined a brace attached loosely so that any movement along the brace makes a record. Maybe a piece of paper stuck to one surface and a pencil glued to the brace (or something less Heath-Robinson). Hard to do in practice but it would be interesting to see whether we are talking about less than one or more than ten millimetres.
Dial gauge should do the trick. Surely there must be some that are able to record the maximum value they measure.Conscript said:
karma mechanic said:
I've often wondered how much movement there actually is between the unbraced strut towers. Imagined a brace attached loosely so that any movement along the brace makes a record. Maybe a piece of paper stuck to one surface and a pencil glued to the brace (or something less Heath-Robinson). Hard to do in practice but it would be interesting to see whether we are talking about less than one or more than ten millimetres.
Dial gauge should do the trick. Surely there must be some that are able to record the maximum value they measure.My first practical experience of chassis flex!!!
kambites said:
those little Allen bolts are pretty pathetic;
Those bolts are 8mm, so hardly tiny. They are done up as tight as I can get them with a standard size 8mm allen key using both hands.No signs of movement either btw.
This is the same design as used by the AC Schnitzer brace, not the kind of company that would design and sell something for over £500 that didn't actually work.
I was going to say they look like M8 fixings.
The preload on these can easily be over 10kN, depending on the strength grade of the fixing.
You will not over-come the clamp loads of these fixings through normal driving. Let's say one corner of your car weighs 500kg. The lateral load your tyres can generate is only about 1G, so this is a side load of about 5kN. It's not quite as simple as that and you could be hitting a 4G bump at the same time, which would make things more interesting, but i would be certain, even the aftermarket would have done some development on fixing size for a strut brace.
I definitely prefer the OEM one with the two fixings though!
This sort of strut brace does make a difference. As a body engineer I have simulated this many times through FInite Element Analysis, and the straight ones, perfectly aligned through the shock tower centre are the most effective.
The preload on these can easily be over 10kN, depending on the strength grade of the fixing.
You will not over-come the clamp loads of these fixings through normal driving. Let's say one corner of your car weighs 500kg. The lateral load your tyres can generate is only about 1G, so this is a side load of about 5kN. It's not quite as simple as that and you could be hitting a 4G bump at the same time, which would make things more interesting, but i would be certain, even the aftermarket would have done some development on fixing size for a strut brace.
I definitely prefer the OEM one with the two fixings though!
This sort of strut brace does make a difference. As a body engineer I have simulated this many times through FInite Element Analysis, and the straight ones, perfectly aligned through the shock tower centre are the most effective.
kambites said:
Is the camber adjustable on the M3 at all?
Your line of thinking is correct kambites.The camber is adjustable, and for that reason the strut brace is indeed slotted.
When I set my old M3 to maximum negative camber and then refitted the strut brace you could how far along the bolts had moved by the old scratch marks.
mat205125 said:
I don't recall them being slotted, however there was a good amount freedom in the fit of the nuts and bolts. This was purely to allow for some natural variation in the manufacturing process, and not intended as adjustment, or to be able to preload the turrets.
They are slotted. The bolts are slackened off during a KDS to allow the turrets to relax before the alignment starts. Bolted up again at the end. They must be slotted to allow for movement.The M8 bolts are more than up to the job.
zeppelin101 said:
Old cars with the chassis stiffness of a lump of Brie benefit from them quite nicely. My 180SX is keener to push on at the front without the brace on at lower speeds.
Increasing the stiffness of the chassis allows the suspension components to do their job better. If the chassis is moving around then the suspension is playing second fiddle to the chassis twisting and rotating during corner loading and over bumps etc.
As an example, an F-Type has some additional bracing around the turrets going forward to the slam panel and back towards the firewall. I would imagine it's to bulk up the stiffness and crash performance without adding additional aluminium or an alternative.
Presumably its an alloy shell? BMW have used the similar style on their cars for a few years. It's to maintain the strength of a steel turret with a minimum level of weight gain.Increasing the stiffness of the chassis allows the suspension components to do their job better. If the chassis is moving around then the suspension is playing second fiddle to the chassis twisting and rotating during corner loading and over bumps etc.
As an example, an F-Type has some additional bracing around the turrets going forward to the slam panel and back towards the firewall. I would imagine it's to bulk up the stiffness and crash performance without adding additional aluminium or an alternative.
Edited by zeppelin101 on Monday 30th March 15:44
jimbobsimmonds said:
Hoofy said:
That strut brace is a work of art!
I have one in the Volvo as standard. I can't decide if it's because it improves the handling above that of a normal saloon car or because Volvo thought the handling was st on the S60 that they had to throw one in. I suppose I could remove it to see what would happen.
Haha, aparently that is there to stop the engine taking off somewhere uptowards the pax compartment during a crash.I have one in the Volvo as standard. I can't decide if it's because it improves the handling above that of a normal saloon car or because Volvo thought the handling was s
t on the S60 that they had to throw one in. I suppose I could remove it to see what would happen.On that basis I decided to put some washers over the rubber bushes and bolt that solid fu***er down. Placebo effect I'm sure, and on the road didn't notice much difference; but under heavy lateral load with the sticky AD08s on I'm sure there was an actual difference. As said, all placebo probably! But for the cost of some washers the placebo effect alone was worth it!
Btw, a well sorted S60 can harrass far more capable machinery
(but agreed, it's a bit like a wounded elephant chasing a balerina; sure the elephant can keep up but the balerina looks much more elegant doing it! Have I won a prise for worst metaphor ever?)
My 2.4T isn't too bad at keeping up with nicer-looking cars. Still getting used to manual shifting the Geartronic system.
VonSenger said:
Not as far as I'm aware apart from the bonnet.
Just had a look and "The F-Type uses an all-aluminium chassis".http://en.wikipedia.org/wiki/Jaguar_F-Type
mwstewart said:
VonSenger said:
Not as far as I'm aware apart from the bonnet.
Just had a look and "The F-Type uses an all-aluminium chassis".http://en.wikipedia.org/wiki/Jaguar_F-Type
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