The dynamics and the point of fitting a strut brace?
Discussion
M3Gar said:
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.
z06tim said:
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.
Easily over 10kN, if only an 8.8. A lot of cap-heads are 12.9 and capable of 15kN on a standard thread (i.e. not even fine pitch).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.
Having said that, a lot are also made out of cheese with a stainless coating and quite a few of those will have just broken simply because I'm talking about them.
A strut-brace, in general, as others have said is intended to eliminate body-flex tending to do the job of the suspension. Assuming that manufacturers would 'fit them as standard, if they actually did anything' is assuming a great many things that individually require much greater scrutiny. Cost is usually a good place to start.
Cheers, Jim
TooMany2cvs said:
jimmy the hat said:
Easily over 10kN, if only an 8.8. A lot of cap-heads are 12.9 and capable of 15kN on a standard thread (i.e. not even fine pitch).
Isn't that along the bolt shank, though - pulling - rather than a sideways force?Evidently, one would be surprised what a pathetic little M8 is capable of.
Cheer, Jim
z06tim said:
Yes, that is the normal force. The force to over-come the friction in the clamped joint will be a percentage of this.
Excuse my ignorance and current foggy headedness if this is badly worded but.. if you are doing 5kN of lateral, putting the bolt in shear and the compression on the m8 cap head is only 10kN and the joint strength is mu*R or something but only if you assume no yield (i.e. scraping) of the bolt or mating surface is it not feasible that while the joint might be up to the job in the most simple no-bump, no-camber, no pitch, level cornering situation, when you're going in to a sharply banked turn hard on the brakes and hit a bump, it might wiggle a bit? Particularly if the bolts are monkey metal?Anyway I was thinking that on that Schnitzer thing the bar looks more bendy than the bolt, they've gone and made it bigger in the wrong direction, it's wafer thin in the d of the bd^3, or am I being dense thinking it'd be bending in that plane?
eta: engineering toolbox gives a mu for aluminium on aluminium of 1.05 - 1.35 for a clean surface, 0.3 if it's "lubricated", but who knows what it is with that anodised finish, I reckon that stuffs a bit slipperier.
Edited by scarble on Wednesday 1st April 16:47
doogz said:
Show your working!
I seriously doubt that with the sorts of loads it'd see, that there'd be any deflection worth talking about.
No you're right, apparently it's more of a brittle failure, which is arguably rather large deflection I seriously doubt that with the sorts of loads it'd see, that there'd be any deflection worth talking about.
I realise it's a busted OE item in the picture and a Schnitzer that I was trash talking but if one can fail so can the other, they're both badly shaped, undersized, made of the wrong material and probably badly cast.
I'm sure they do help, but if I'm going to spend money on a strut brace I'll go for good old tubular steel ta very much.
mwstewart said:
For those wonering about the effectiveness of a brace, this:
Is not uncommon on E46 M3's that are used in Autocross and other hard driving events. They definitely do make a difference.
Looks like a nice brittle cast alloy, not a great choice of material. It wouldn't need much movement at all to break that through fatigue.Is not uncommon on E46 M3's that are used in Autocross and other hard driving events. They definitely do make a difference.
scarble said:
I'm sure they do help, but if I'm going to spend money on a strut brace I'll go for good old tubular steel ta very much.
SkinnyPete said:
The E46 is quite a floppy chassis in fairness though, isn't it? Yes I know they are good handling but they have half the structural rigidity as the equivalent Mondeo for example.
Yeah - I think they are. The most rigid in the line up is the base model saloon without rear folding seats i.e. with a metal rear bulkhead. Mr2Mike said:
Looks like a nice brittle cast alloy, not a great choice of material. It wouldn't need much movement at all to break that through fatigue.
The cheapest lowest grade cast alloy imaginable but it illustrates the point. I think there is a design consideration here though: if the strut brace is too secure a knock to either wing is carried over to the opposite side and means a more expensive insurance repair. This was certainly what insurers cited as the reason for increasing premiums on modified cars with a front strut brace.TooMany2cvs said:
z06tim said:
The force to over-come the friction in the clamped joint will be a percentage of this.
Any thoughts on what %age, especially where painted metal is one of the surfaces?The 5kN lateral load I estimated does not all go through the strut brace though, as remember the input is at tyre contact patch. Most will probably go through the lower control arm and sub-frame, dependent on suspension design. Have a look at how the forged upper wishbone is so slender on a C4 Corvette for instance, and most cars these days have a pretty robust looking lower control arm.
Also, my experience of BMW saloon car torsional stiffness is that they were always competitive, if not class leading. So I very much doubt E46 will be considerably less than a contemporary Mondeo. However, all the other E46 derivatives which delete the sheet metal behind the rear seat will be less stiff than the saloon they are based on, and the convertible the least stiff.
z06tim said:
Also, my experience of BMW saloon car torsional stiffness is that they were always competitive, if not class leading. So I very much doubt E46 will be considerably less than a contemporary Mondeo. However, all the other E46 derivatives which delete the sheet metal behind the rear seat will be less stiff than the saloon they are based on, and the convertible the least stiff.
Compare the stiffest E46 with the X-Type (old Mk3 Mondeo) - the Mondeo is stiffer.Alfa 159 - 31.400Nm/degree
Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg
Aston Martin Vanquish 28,500 Nm/deg
Audi TT Coupe 19,000 Nm/deg
Bugatti EB110 - 19,000 Nm/degree
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
BMW X5 (2004) - 23,100 Nm/degree
BMW E90: 22,500 Nm/deg
BMW Z4 Coupe, 32,000Nm/degree
BMW Z4 Roadster: 14,500 Nm/deg
Bugatti Veyron - 60,000 Nm/degree
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Chevrolet Corvette C5 9,100 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 360 Spider 8,500 Nm/deg
Ford GT: 27,100 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Koenigsegg - 28.100 Nm/degree
Lambo Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
Maserati QP - 18.000 nm/degree
McLaren F1 13,500 Nm/deg
Mercedes SL - With top down 17,000 Nm/deg, with top up 21,000 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Pagani Zonda F - 27,000 Nm/degree
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 959 12,900 Nm/deg
Porsche Carrera GT - 26,000Nm/degree
Rolls-Royce Phantom - 40,500 Nm/degree
Volvo S60 20,000 Nm/deg
Audi A2: 11,900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT: 10,000 Nm/deg (22Hz)
Golf V GTI: 25,000 Nm/deg
Chevrolet Cobalt: 28 Hz
Ferrari 360: 1,474 kgm/degree (bending: 1,032 kg/mm)
Ferrari 355: 1,024 kgm/degree (bending: 727 kg/mm)
Ferrari 430: supposedly 20% higher than 360
Renault Sport Spider: 10,000 Nm/degree
Volvo S80: 18,600 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Porsche 911 Carrera Type 997: 33,000 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
VW Phaeton - 37,000 Nm/degree
VW Passat (2006) - 32,400 Nm/degree
Ferrari F50: 34,600 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg
Mazda RX8 - 30,000 Nm/degree
Saab 9-3 Sportcombi - 21,000 Nm/degree
Opel Astra - 12,000 Nm/degree
Land rover Freelander 2 - 28,000 Nm/degree
Lamborghini Countach 2,600 Nm/deg
Ford Focus 3d 19.600 Nm/deg
Ford Focus 5d 17.900 Nm/deg
I think following the drive for safety starting with the '90's airbag era most things now have a shell stiff enough to facilitate decent suspension operation on UK roads.
Hmmmn. I'd forgotten how the X-type had actually claimed to better most German contemporaries in terms of body stiffness.
However, I don't think it is quite fair to quote that as the torsional stiffness of the Mondeo of the time. Jag did quite a lot of re-engineering of that platform. It was after all a different wheelbase, an AWD installation, and I'm sure a heavier car, at least as its fully optioned derivative.
This is quite an interesting read: http://www.aronline.co.uk/blogs/cars/jaguar/x-type...
Shame it didn't do very well against the Germans. Hopefully XE will do better.
However, I don't think it is quite fair to quote that as the torsional stiffness of the Mondeo of the time. Jag did quite a lot of re-engineering of that platform. It was after all a different wheelbase, an AWD installation, and I'm sure a heavier car, at least as its fully optioned derivative.
This is quite an interesting read: http://www.aronline.co.uk/blogs/cars/jaguar/x-type...
Shame it didn't do very well against the Germans. Hopefully XE will do better.
mwstewart said:
z06tim said:
Also, my experience of BMW saloon car torsional stiffness is that they were always competitive, if not class leading. So I very much doubt E46 will be considerably less than a contemporary Mondeo. However, all the other E46 derivatives which delete the sheet metal behind the rear seat will be less stiff than the saloon they are based on, and the convertible the least stiff.
Compare the stiffest E46 with the X-Type (old Mk3 Mondeo) - the Mondeo is stiffer.Alfa 159 - 31.400Nm/degree
Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg
Aston Martin Vanquish 28,500 Nm/deg
Audi TT Coupe 19,000 Nm/deg
Bugatti EB110 - 19,000 Nm/degree
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
BMW X5 (2004) - 23,100 Nm/degree
BMW E90: 22,500 Nm/deg
BMW Z4 Coupe, 32,000Nm/degree
BMW Z4 Roadster: 14,500 Nm/deg
Bugatti Veyron - 60,000 Nm/degree
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Chevrolet Corvette C5 9,100 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 360 Spider 8,500 Nm/deg
Ford GT: 27,100 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Koenigsegg - 28.100 Nm/degree
Lambo Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
Maserati QP - 18.000 nm/degree
McLaren F1 13,500 Nm/deg
Mercedes SL - With top down 17,000 Nm/deg, with top up 21,000 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Pagani Zonda F - 27,000 Nm/degree
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 959 12,900 Nm/deg
Porsche Carrera GT - 26,000Nm/degree
Rolls-Royce Phantom - 40,500 Nm/degree
Volvo S60 20,000 Nm/deg
Audi A2: 11,900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT: 10,000 Nm/deg (22Hz)
Golf V GTI: 25,000 Nm/deg
Chevrolet Cobalt: 28 Hz
Ferrari 360: 1,474 kgm/degree (bending: 1,032 kg/mm)
Ferrari 355: 1,024 kgm/degree (bending: 727 kg/mm)
Ferrari 430: supposedly 20% higher than 360
Renault Sport Spider: 10,000 Nm/degree
Volvo S80: 18,600 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Porsche 911 Carrera Type 997: 33,000 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
VW Phaeton - 37,000 Nm/degree
VW Passat (2006) - 32,400 Nm/degree
Ferrari F50: 34,600 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg
Mazda RX8 - 30,000 Nm/degree
Saab 9-3 Sportcombi - 21,000 Nm/degree
Opel Astra - 12,000 Nm/degree
Land rover Freelander 2 - 28,000 Nm/degree
Lamborghini Countach 2,600 Nm/deg
Ford Focus 3d 19.600 Nm/deg
Ford Focus 5d 17.900 Nm/deg
I think following the drive for safety starting with the '90's airbag era most things now have a shell stiff enough to facilitate decent suspension operation on UK roads.
What's the source of this data, and any idea how the comparisons were made for each vehicle to be compared fairly with one another. I understand how a vehicle could be measured in isolation, by jigging at it's suspension pick ups, however not sure how a comparison could be made from the top mounts of a MacPherson front end of a 3 series, to a double wishbone sports car.
z06tim said:
However, I don't think it is quite fair to quote that as the torsional stiffness of the Mondeo of the time. Jag did quite a lot of re-engineering of that platform. It was after all a different wheelbase, an AWD installation, and I'm sure a heavier car, at least as its fully optioned derivative.
The 2wd X-types were FWD, just as the 2wd Mondeos, and the AWD X-types were just as AWD as the AWD Mondeos were...That's an interesting list. I've just been chatting to a friend about Z4s, as he's after one and I owned a Z4 Coupé for a while, although he's considering a Roadster. I said the Z4C was probably stiffer, but I had no idea that it was comfortably more than double the stiffness of the Roadster!! 
Lighter too...
Lighter too...TooMany2cvs said:
z06tim said:
However, I don't think it is quite fair to quote that as the torsional stiffness of the Mondeo of the time. Jag did quite a lot of re-engineering of that platform. It was after all a different wheelbase, an AWD installation, and I'm sure a heavier car, at least as its fully optioned derivative.
The 2wd X-types were FWD, just as the 2wd Mondeos, and the AWD X-types were just as AWD as the AWD Mondeos were...Gassing Station | General Gassing | Top of Page | What's New | My Stuff