Body stiffening braces- sorting the good from the crap

[Ben Wilson]

but seriously, it should be easy to rig up a few little tools to measure the amount of flex between the positions these braces bolt on....

How a laser pointer and a video camera? That way you could take it to the track and measure 'real world' conditions...

[Billzilla]

How a laser pointer and a video camera? That way you could take it to the track and measure 'real world' conditions...

Good idea ... + rep
(if it'll let me)

[MZ20_drifter]

the front strut brace i put on my s13 made abit of a difference the car felt alot more predictable. i still have to install the rear ill see how i go

[The Real Roadrunner]

i put a set of under guard braces on an s13 that came in to my shop and the driver noticed the difference.
strutbrace back to the firewall once again a difference.
next a brace like an x from rear strut tops to the belt mounts on the pillars and better again .
brace to each caster rod mount better again.
the car got more predictable with each of these mods.

the hump braces across the floor do nothing unless you have a rear halfcage then it might make it stiffer.

with road cars most people wont feel a difference and just want rice.

when working with spring rate over 8kg/mm you would be surprised how much the fifth spring will move.

pissed me off when i built a full cage for the car that was tied in to everything and we had to spend 3 days at the track to set all the susp back up as the car was so much stronger.
but once this was done the car was alot quicker (ie laptimes) and much more predictable.

[JustenGT8]

Wanna clue me in to why a rear strut tower brace is useless ballast? Very obvious gains in chassis stiffness in both cars i have built them for...pretty standard component of rollcage design as well. Can't see much difference (except it would be better) than the seat latch mount brace?

Any large empty rectangular frame will benefit from a cross brace. Diagonal would be better but rear struts towers are dead convenient and also make a great harness mount...well they do in the GT8 anyways.

[Billzilla]

Wanna clue me in to why a rear strut tower brace is useless ballast? Very obvious gains in chassis stiffness in both cars i have built them for...pretty standard component of rollcage design as well. Can't see much difference (except it would be better) than the seat latch mount brace?.

It's because you put very large engines into little cars and so have to cut big holes into the body to make them fit, thus giving them the rigidity of wet toilet paper.
So anything you can add to them will help.

[WDE_BDY]

Wanna clue me in to why a rear strut tower brace is useless ballast? Very obvious gains in chassis stiffness in both cars i have built them for...pretty standard component of rollcage design as well. Can't see much difference (except it would be better) than the seat latch mount brace?

Any large empty rectangular frame will benefit from a cross brace. Diagonal would be better but rear struts towers are dead convenient and also make a great harness mount...well they do in the GT8 anyways.

Depends on the car. AE86 you have the brace running between shock mounts, so the brace isn't even supporting in the direction of possible deflection and has bugger all load on it anyway. MA61 is similar, there is a massive subframe bolted under the floor and people are concerned about flex between the shock mounts????
However if you have a coilover setup the loads will actually be on those points, of course you might want to brace in the actual direction of the force to have a decent effect. With the shock towers almost vertical any load is pushing up not across to to the shock on the opposite side of the car. Cages will run a brace from the rear hoop down to the top of the wheel arches/shock mount area, this is far more important for flex prevention than the cross bar is. Cross bar is obviously important for crash forces though.

Callum

Callum

[WDE_BDY]

To quote me from an old thread -

Further to that example Old Corollas posted, this is the front tower of my Starlet. There is usually a plate spot welded across the area, you can see where the spot welds have been drilled out and the rust that formed to the front between the two layers.
Normally you would patch the rust and replace the plate, but in my case we are unable to do this as I need to move the strut tops outwards and there won’t be enough room for the spring to move in the tower. We are looking at a setup similar to the one above but using round tubing, not sure yet if we will bolt to the hinge points or weld it on, most likely bolted though. This will be in addition to the full cage tying through to the front and rear towers, and bolt in bars from the front of the towers to the front castor arm mounts. There are also 3mm plate triangles at the base of the firewall where it meets the chassis rails.



Some of these ideas can be incorporated fairly cheaply, the firewall bracing for example is not hard to do if you have the engine out anyway. All we did was make templates with carbboard and then get them cut out.

Callum

[JustenGT8]

Depends on the car.

Callum

Exactly even in my old TA22 it wasn't so much bracing the towers because of suspension loads as just bracing a flimsy chassis as pragmatically as possible for a daily. So, not uselass ballast afterall

[JustenGT8]

It's because you put very large engines into little cars and so have to cut big holes into the body to make them fit, thus giving them the rigidity of wet toilet paper.
So anything you can add to them will help.

LOL ba$tard.....and this from the giant trying to build up a Starlet he never actually fit in

[Moppitt]

I cant speak for all cars however I have noticed 2 things...

1) I fitted a factory front (3 point, two piece) and then later a whiteline rear strutbrace to my ae82 and both made an appreciable difference to the handling. The front allowed for a more predicatble shift into understeer and less plow understeer.

The reat strut brace made the back end much more stable predictable, particularly through changes in direction, but also it became more settled as I would tip it in to a corner. I can occasionally hear it creaking a little, ive checked that everythings tight but its not coming loose... Shrugs..

Now of course these are both going into an AE82 Corolla hatch, which is your basic light weight, box shape chassis with a great big hole cut out of the back for a boot, thrus allowing all kinds of movement in the chassis.

2) The other thing is that I helped a mate refit the bolt in cage to his Pug 205 gti club racer. The most noticeable thing I found that was with the cage in, suddenly just about all the creaks and rattles stopped when I drove it with the cage in . I wont comment on the handlling or chassis stiffness as I wasnt pushing the car through corners (cold semi slicks :S )

One thing im thinking of doing is just loosening the bolts on the firewall for the front strut brace (the ones that hold the two halves together and to the firewall) and painting all the edges with whiteout, around the bolts, the ends of the strut brace ect ect. Then driving for a little while and seeing if any of the white out gets removed or chipped off due to the different pieces moving relative to each other. It wont exactly be scientific but might give some idea of the flexing between the two strut towers and the firewall.

Finally, that same friend of mine now has a shell from one of the old Peugeot 405 super tourers with the complete cage still in. The cage is a work of art (as are the carbon fiber door trims and rear parcel shelf and panel below it right to the floor) but that also goes to all strut towers and beyond.

[EVOSTi]

moppit, you will notice marks on your firewall if you try that. my mate used to have a AE112 sportivo rolla and he put the strut brace from an AE101 levin in it, but didnt bolt it to the firewall and the paint around this point was all rubbed off after a little while.

[Sam_Q]

sorry guys been busy away from home.



oldcorollas: front fender braces sopposedly are meant to stop flexing of the whole front upper area, one source says though the weakness caused by the crumple zone which sounds like rubish. Looking it it though theoreticly the front end could move and twist and be supported by a good brace. Would it help having it braced? its anyones guess. Also yes those braces you have a picture of are just dead metal, I mean using plate for something thats meant to be rigid? thats just stupid.

I think your idea of using a way to actually measure the twisting of the body is a great idea. What I was thinking is different that what ben said and that is as so:

two tubes so one slides inside the other in the middle, Mounted to a plate is a dial indicator with a flat plate that the dial indicator presses against. For example one end of the pole could be mounted to each of the ends of the seat latch mounts. My idea would only work under compression though.



RobertoX: Interestingly enough I didnt notice a difference when I installed my rear seat latch brace, however I have to say at the time I did have a poor setup and I probably wouldnt of been able to tell. Once my cars more sorted I will do some back to back testing. I do plan on doing some bracing directly to the body under the trim later on to hopefully negate the need for a rear brace because I cant afford to have lost space back there. Either that or make some sort of quick release which I cant say I like much.

I am keeping my mind open to those fender braces, they atleast have a very solid set of mounting points which is more than many braces could claim.



Ben Wilson: great idea, which would measure bending of the mount rather than compression like my idea. I think i might try it and try jacking up the car and seeing what happens. Good thing too is that its easy to take photos of a bright red spot if the cars stationary.


MZ20_drifter: silvias have a Macpherson rear end so therfore there are strut towers at the rear and some side loading on them. So in thoery atleast a brace should help.



JustenGT8: most rear braces have just a loop that go from betwen the two shocker pins at the top. As WDE_BDY said theres no side loading there. Also what no-one else has mentioned is that theres also a bush in the top of that shocker and if there somehow was a force going through it then it the bush would just deflect. The other thing is that even if the top position would deflect I cant see it making a difference, I mean the shocker doesnt control any suspension angle if the length doesnt change.

The other mount goes on the thin sheet metal of next to the shocker top, and just 150mm of so down just under the floor is a very solid subframe running across the width of the car.

The rear brace that goes between the seat latch mounts is different, no only does it go between two tottaly solid mounting points it braces the body itself.

[Sam_Q]

WDE_BDY: well said I agree tottaly with all your comments.



Moppitt: The ae82 corolla if my memory serves me right has a macpherson rear suspension design and therfore in theory atleast can benefit from a rear brace.

With the tri brace I remember on the strut brace thread that someone said the bolts for the firewall mount of the tri-brace was left loose and when he went around the corner he would hear a knock as the brace moved and the hole tapped against the side of the bolt, and again against the other side of the bolt going the other way. Hard to explain for me

[30psi 4agte]

Exactly even in my old TA22 it wasn't so much bracing the towers because of suspension loads as just bracing a flimsy chassis as pragmatically as possible for a daily. So, not uselass ballast afterall

Hell it sounds like you are talking about my little cortina here !! A plank of wood nailed down would do a world of good to the tin can that it is


Interresting thread though!!