Body stiffening braces- sorting the good from the crap

[WDE_BDY]

Cant find the pics at the moment, but one idea I have seen was a brace from the top of the rear shock up to the seatbelt mount in a RWD starlet. Effectively tied the shock mounts to the roof structure, I believe the car was running coilovers to the standard shock mounts though to gain any real benefit. Comes back to triangulation, and bracing in the direction of the force applied.

Callum

[JustenGT8]

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.

Most?? i don't think so. 99% of rear strut braces brace to the strut tower NOT the shock. I'm not say bracing the strut towers is the best place but it DOES make a difference and even on an AE86 would help enough to be worth the weight. For most, it's an easy and practical place to stick a brace. On the 22 it made a HUGE difference and even on the GT8, which is a very stiff body shell to start with and way stiffer with all the other bracing i have added, you could pick it. How much you benefit depends on the type of car but sorry, a strut tower brace is far from useless ballast. 'O' will always be stronger than 'U'

[RAd28]

impressive thread... quite a read, my head hurts trying to take everything in...

i'm planning on attacking my '28 with some bracing as soon as i can afford anything, my plans were a 3pt strut brace, a rear tower brace that goes from around the shock bush, to the upper seat belt mount, left to right side, (now being re-considered ). other then that, was more concerned with putting in some nolathane radius rod bushes, and other things like that to try and stop unwanted suspension movement...

i'm struggling to see how a rear strut brace is any different to a seat mount brace, and how those "room braces" the ones that got B-pillar to B-pillar have ANY effect at all, even though i've spoken to a few people who have them, and they seem convinced it has an effect.

as for putting strain gauges all over your car and going for a thrash, sounds great, strain gauges are cheap as!, laptops aren't hard to get ahold of... oscilloscopes on the other hand... $$$$$
i think a laser pointer and a video camera would be near impossible to see... the camera mount would be vibrating around, you'd be after a pretty huge deflection to notice any movement...

cheers

[Ben Wilson]

the camera mount would be vibrating around, you'd be after a pretty huge deflection to notice any movement...

Place the camera near the spot from the laser and put a 'target' grid out so you can tell exactly how much deflection you're getting.

You'd also want to find as long a shot as you can to maximise the effect.

[clubagreenie]

edit: to make bills point, put one jackstand on the far rear corner suspension mount.. then jack up from the diagonally opposite corner.....

JZA80. Jack Front corner towpoint, will lift front of car off the ground, still able to open and close doors without any deflection. Try the same thing in Joorsh's skyline, open doors wouldn't close again .

Supra ront chassis rails = huge boxes and even with coilovers the double wishbones handle movement. There would be no way to really relieve vertical loading on the spring/shock tower top.

[Sam_Q]

Most?? i don't think so. 99% of rear strut braces brace to the strut tower NOT the shock. I'm not say bracing the strut towers is the best place but it DOES make a difference and even on an AE86 would help enough to be worth the weight. For most, it's an easy and practical place to stick a brace. On the 22 it made a HUGE difference and even on the GT8, which is a very stiff body shell to start with and way stiffer with all the other bracing i have added, you could pick it. How much you benefit depends on the type of car but sorry, a strut tower brace is far from useless ballast. 'O' will always be stronger than 'U'

sorry Justin I should of been more specific, I meant to say this: most rear braces available for sprinters just go between the two shocker pins. Any car that has a macpherson rear should benifit from a brace much unlike a sprinter. With the spritner braces how could it help when it attaches to something that has a bush between it and the body?



RAd28: the difference between the rear braces for sprinters/ra28s is that they join onto a low part of the body which has no sideways load. The seat latches on the other hand are part of the car where the whole side deflects with it, well that and they are actually on a solid anchor point.

[JustenGT8]

With the spritner braces how could it help when it attaches to something that has a bush between it and the body?

Yup in this instance it's pure bling.....have never seen one and can't believe someone would even buy such a brace, right up there with fake disc brakes

[Moppitt]

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.

I recall reading a while ago about the BA XR6T that ran in targa tasmania beofre the official release, the drivers kept saing that they were hitting the bump stops, to check they put a cable tie around each shock to see where they ended up, thus telling them what the maximum compression was... So...

For a quick and dirty way of measuring maximum deflection using that method, put a cable tie around the inner pipe, so that it will get pushed by the outer pipe, the loading of the cable tie wont stop any flex, and the displacement from the outer pipe will show what the maximum deflection. Unfortunately it wont show how or when the flex is happening but will show the magnitude of the flex.

I has anyone had a look inside the boot of a Evo ?8, or there abouts 7, 9?? I think its 8.. anyway, IIRC, they have a big brace that looks like a box with a X through the middle of it sitting flat against the back seats between the strut towers. I would like to see a photo of one as I only half saw in a while ago bit thats the general shape of it. I think it was mostly, kinda corrigated sheet metal (like a lot of car floors) as well, not pipes.

The great thing with that brace was that it barely reduces boot space at all (although you cant fold the seats down with it in, im not sure if you can in an ordinary lancer..) and it has triangulation up the wahzoo.

[Mr Revhead]

some damn good points in here.

as wde_bdy says.... think if the direction of the forces.


as per jacking cars up on one corner....
just be careful.... one certain model of ford is well known for cracking the screen if jacked on one corner and a door opened..... 92 telstar i think?
iv had echos on a 2 post hoist and you can feel the resistance when you open and shut a door

[TERRA Operative]

Ok, so regarding rear bracing, would the following be worth while? The brace will be custom made, and attached to the strut tower tops (not the strut itself), then bolted to the floor on a welded on plate (to prevent lateral movement like a parallelogram).

It'll also help with the mounting of harnesses I guess.

[WDE_BDY]

That will definitely help, due to the height of the towers above the floor there is more room for deflection. For ultimate bracing you would also brace from the top bar to the top rear belt mounts, usually not very practical for a daily car though.

Callum

[Sam_Q]

yeah that looks good, like you said you would want a plate welded though.

[Sam_Q]

oh and i recommend using 1.25 x 0.035 cro-mo pipe for that, or 32 x 0.9mm when you convert it

[TERRA Operative]

That will definitely help, due to the height of the towers above the floor there is more room for deflection. For ultimate bracing you would also brace from the top bar to the top rear belt mounts, usually not very practical for a daily car though.

Callum

The car is being engineered as a two seater, so the bars to the rear seatbelt mounts are a possibility. (you mean on the D-pillars or whatever they're called?)
I guess a bar from the top of the strut towers to the belt mounts wouldn't be hard to fabricate.

Where is the best place to get the cro-mo pipe from?

[Sam_Q]

getting cro-mo pipe in your state? I have no idea, I get mine from an aircraft supplier called airport metal. The code is 4130 if that helps at all.

So sorry all I can recommend is looking up specialized steel suppliers or aircraft material suppliers.