subrame braces

[10thcb7]

I think cb7s can use both rear strut bars and xbars im not sure though. As far as the fender braces Im sure a custom set can be made by taking some micro measures and making a template for a machine/engineer shop to laser cut. I want to know more about those inner "skeletons" that EK chassis use.

[cp[mike]]

id love to have a rear x-brace like oneoff posted. my only thing is that for me to ever install it, the X part would need to be removable, with the strut bar being permanent.

[oneoffaccord]

id love to have a rear x-brace like oneoff posted. my only thing is that for me to ever install it, the X part would need to be removable, with the strut bar being permanent.

mike its removable

[slick]

the guy above that was talking about the x brace in the rear said his didn't go into the trunk space

[GreenMadness]

there is alot of information in this thread that seems dangerous and easily misinturpreted.

first, if you are serious about racing, the only goal for the rear end sway is a stiff enough sway bar to lift your inside tire going through turns.

if you are into hydrulics you are probably bouncing around... shear wont do shit, when you have a bending moment from the front of a car being in the air, or for that matter hitting the ground again, hence the brace right in the middle of the car where the bending moment will be the worst.

for cars the body roll is the suspension giving (its meant to) when you stiffen the car you reduce body roll.... a well known concept...BUT when the suspension/anti-roll subframe is too stiff it doesnt give, POSSIBLY a good thing, except you would find all 4 wheels on the ground in turns why? cause load travels to stiffness, meaning your suspension is now twisiting the frame enough to keep all 4 wheels on pavement (VERY BAD FOR THE CAR you are actually twisting the body in torsion )

you lift a wheel...to keep the body as straight as possible, this cant be done due to the weakness of your passenger compartment... the only way to acheive the body strength needed to stay straigh and lift a wheel is with a roll cage.

No 1 part of a race car is gonna work out like you think on your street car. all together as a package they do well.

Much of the information seems to be a mix of mechanics, and RWD race car setup... although there isn't alot of information in the US for FWD race setup there is some, and most of it only states that RWD setups dont work... and the set up/ technique for driving a FWD car varys with every modification/ driver/ Manufacture.

SO PLEASE in a quest for stiffness dont destroy your car... rear end roll in a FWD street car is favorable in comparison to a RWD RACE car.

i haven't seen any GT-Light 4th gens, so i dont think anyone here has a FWD RACE car accord, if you do... why the hell haven't you posted pics!


LASTLY... stiffness is good for racing, not gonna lie... i see RWD mustangs lifting the inside front tire on acceleration... and i see FWD civic hatches lifting the inside rear wheel on braking... but only on a race track!

honda's last cause they designed them well, meaing low stresses and high design factors. in impact loading (sudden loads) stiffness increases stress ALOT! so as you are stiffing your car you are in fact reducing its life...

Race cars dont last to 200,000 miles.....



JohnL: i am not attacking your information, as you mostlikely know the affects of stiffness, but i am trying to deliver both sides of the stiffness debate so that anyone that reads it may also know the downside to extreme rigididty.

[johnl]

post pics of your setup. I wanna see what type of x brace you have so i get a good idea

I would, but I'm not really set up with the correct gear, I'd have to borrow a camera, then learn how to get the shots into the computer and then how to upload to the site, and I'm too lazy!

My 'X' brace looks very similar to that beige coloured one that someone else posted, but instead of sitting flat in the boot space it sits more or less vertically behind the seat back. It attaches to the rear parcel shelf metal work with two bolts on each side (the same two bolts that attach the stock angled sheet metal braces on each side of the seat aperture, which are also retained in front of the X brace), and at the bottom is bolted to two 3mm thick plates (one each side) that are attached to the chassis behind the stock braces, again using the existing stock brace attachment bolts (two per side). These stock chassis bolts are not as large as I'd like, but fitting larger bolts would mean dropping the fuel tank, which isn't likely to happen!

The X brace is designed to prevent the section of chassis behind the seat back (including the area between the strut tops) from 'trapezoiding' (is that a word?!) under load, and generally stiffen the rear of the chassis where the loads are imparted into it. I also have a rear strut brace that is also bolted to the centre of the 'X' in the brace (using two short tubes). I noticed improvement in response and understeer (i.e. less understeer) with both the strut brace and the X brace, strut brace probably more so than the X brace, but it's hard to say which really has the most affect since I haven't had the X brace fitted without the strut brace. I have to say I noticed no improvement when I bolted the strut brace to the X brace.

[johnl]

there is alot of information in this thread that seems dangerous and easily misinturpreted.

Speaking of misinterpreting, I’ve found it quite hard to address the statements you’ve made (below) largely because I found it so hard to decipher what you’re saying. I’ve read what you wrote very carefully, and I’m still not sure I’ve understood exactly what you meant in every sentence.

first, if you are serious about racing, the only goal for the rear end sway is a stiff enough sway bar to lift your inside tire going through turns.

Be careful of blanket statements. IMO the goal is to increase rear roll stiffness to the point that the IR lifts under hard cornering, whether this is achieved solely by means of increasing ARB stiffness may be debatable, though I’m not saying you’re wrong, but it will depend on the specifics of the car, the set up and the usage. In some instances you might be better off gaining more of the rear roll stiffness from spring rate increase than from ARB rate increase, and in other instances the opposite may be true, and may well be true more often, but it depends on the starting point as well as all the other variables.

tif you are into hydrulics you are probably bouncing around... shear wont do shit, when you have a bending moment from the front of a car being in the air, or for that matter hitting the ground again, hence the brace right in the middle of the car where the bending moment will be the worst.

The sort of loads imposed by “bouncing” on the hydraulics are going to be fairly substantial. I think you’ll want as much stiffness as you can reasonably achieve just to avoid breakages. I do think hydraulic suspension set ups are a bit on the silly side though…

for cars the body roll is the suspension giving (its meant to) when you stiffen the car you reduce body roll.... a well known concept...BUT when the suspension/anti-roll subframe is too stiff it doesnt give, POSSIBLY a good thing,

Chassis stiffness is always a ‘good thing’, if for no other reason that if the chassis is stiff then changes to suspension set up actually have a significant affect, rather than being partially ‘lost’ in a floppy chassis. A car that has a floppy chassis may well require excessive changes to things like spring and damper and ARB rates to make significant changes to the handling etc, and these excessive rate increases may well have unwanted side affects, not the worst of which would be increasing the chassis flex.

Many years ago before these things were really understood, it was not uncommon practice for racing engineers to hack out some part of the chassis in an attempt to improve handling balance, and it often worked to a degree, but the reason why is that the suspension rates themselves were too high either at the front or the rear relative to each other, so softening some part of the chassis addressed this deficiency in a rather clumsy manner.

except you would find all 4 wheels on the ground in turns why?

If you stiffen the chassis at say the rear then you will get more weight transfer at the rear and less at the front. Same in principle if you stiffen the rear spring rates (this also the case in reverse, i.e. if you stiffen the front of the chassis etc…). In either case (rear suspension or chassis stiffness increase) you will be more likely to lift the IR. Note that neither softening nor stiffening the suspension, nor softening or stiffening the chassis will result in more or less total weight transfer if the lateral acceleration remains the same.

I suspect you are confusing body roll with weight transfer, they are not the same thing. The less roll stiffness there is the more the body will roll, but this only changes the speed with which weight transfer occurs (slowing it), not the degree to which it will ultimately transfer (assuming lateral acceleration remains the same, though it will probably lessen if roll is too great due to camber change affects). The affect of increasing or decreasing roll stiffness at one end of the car is to alter the distribution of a given weight transfer (i.e. the ‘roll couple’), though it won’t change the overall weight transfer all else being equal.

cause load travels to stiffness, meaning your suspension is now twisiting the frame enough to keep all 4 wheels on pavement (VERY BAD FOR THE CAR you are actually twisting the body in torsion )

You’re suggesting that stiffening the chassis causes increased chassis twist? I think you’d have little difficulty finding numerous professional chassis engineers who will strongly disagree with you.

I’ll agree that “load travels to stiffness”, but this means that more load transfers from the inside to the outside at the axle line with the greatest stiffness, being a combination of suspension rate and chassis stiffness at / near that axle line, and less so at the axle line with less stiffness. I suspect you are imagining more stress increase than actually exists. The load seen by the chassis as a whole is the difference in the rates at each axle line, not the total of the two loadings seen at both axle lines.

A stiffer chassis is better able to resist the difference in loadings seen at each axle line, and as such more effectively isolates the weight transfer occurring at the rear from the weight transfer occurring at the rear.

This means that stiffening the rear of the chassis as well as stiffening the rear suspension will cause an increased weight transfer at the rear end of the car (with a resulting lesser transfer at the front, assuming lateral acceleration remains constant). In both cases this will result in more IR unloading, not a reduction in one case and an increase in another.

Try thinking of localised chassis softness as part of the suspension rate, e.g. if the rear of the chassis is soft then this adds to the overall softness at the rear of the car, being a sum of the suspension rate and the rear chassis stiffness.

you lift a wheel...to keep the body as straight as possible,

What does this mean??

this cant be done due to the weakness of your passenger compartment... the only way to acheive the body strength needed to stay straigh and lift a wheel is with a roll cage.

I think you are envisaging more twisting of the chassis than actually exists on any reasonably stiff chassis. Even relatively soft chassis don’t actually twist all that much, but the affect of the twisting is quite significant, more than you’d intuitively expect from amount of twisting that occurs, which is certainly a lot less than the movement provided by the suspension.

It’s not the twist itself that limits the ability of a softer chassis to lift an inside wheel, but the affect on relative front / rear roll stiffness of the softer chassis, i.e. a softer chassis can’t as effectively isolate the front roll stiffness from the rear roll stiffness, so even if the ARB and spring rates are relatively high at one compared to the other some of this relative difference in roll stiffness is ‘lost’ in the soft chassis, so the car is less able to effectively unload a particular inside wheel.

The passenger compartment will typically be the stiffest part of the total structure, simply due to it’s girth (i.e. it’s analogous to a large diameter square tube, being more rigid than a smaller diameter tube). Some of course aren’t very stiff, less stiff with longer wheelbase, more door apertures and with poorer design. The front of the chassis tends to be less stiff because it’s smaller and usually missing structural parts required to ‘close the box’, i.e. the lack of a structural member between the strut towers deducts a lot of stiffness, and ideally there should also be a diagonal brace here as well, but the engine tends to be problematic in this regard. The rear of the chassis suffers similarly, i.e. lack of bracing between the struts, and a lack of diagonal bracing. These are things that something can be done about. This does mean more of the loading will be ‘seen’ in the central section of the chassis, but most can cope quite easily even if this means a slight increase in flex in the central part. Keep in mind that any increased flex in the central part of the chassis won’t be the same degree of flex that would have occurred in the softer section before it was stiffened simply moved into the central section, it will be less.

Note that chassis stiffness is cumulative, each bit adding stiffness to the chassis as a whole.

I agree that the best way to increase body rigidity is to use a properly engineered cage that will include bracing between the strut towers, or be used in addition to such braces, but anything you do to increase stiffness will beneficial. You don’t need to actually lift the IR off the deck for there to be an advantageous increase in rear weight transfer, anything you do to increase rear weight transfer (whether or not this actually results in daylight under the IR) will decrease understeer tendencies and probably sharpen responsiveness.

===========

Seems I've done it again, exceeded the limit on verbose responses that is!
Part two below;

[johnl]

Part two (sigh);

No 1 part of a race car is gonna work out like you think on your street car. all together as a package they do well.

Anything done to a race car to improve handling etc will in principle be beneficial on a ‘performance’ street car, but it would be unwise to go to the same extremes as you would for a racer as the compromises can be pretty major. With chassis stiffening this tends to be limited by cost and practicality rather than any dynamic considerations.

Everything that I’ve done to increase the chassis stiffness on my car has been noticeably beneficial to handling, responsiveness, and a general feeling of the car being ‘connected’ to the road. I’d fit a roll cage too if I could afford it and live with it (and if a ‘proper’ cage were legal).

Much of the information seems to be a mix of mechanics, and RWD race car setup... although there isn't alot of information in the US for FWD race setup there is some, and most of it only states that RWD setups dont work...

The major difference between RWD and FWD set ups is to do with the fact that with a RWD you need most of the weight transfer to occur at the front end in order to keep the rear wheels as equally loaded as reasonably possible in order to get drive traction. With FWD you need most of the weight transfer to occur at the rear in order to keep the front wheels as equally loaded as reasonably possible in order to get drive traction. This is the only reason you see many RWD racing sedans lift the IF, and so many FWD racing sedans lift the IR. The major difference between FWD and RWD is that the roll couple is set up in an opposite manner.

and the set up/ technique for driving a FWD car varys with every modification/ driver/ Manufacture.

The details of set up will vary with each and every different racing or modified road car, whether FWD or RWD. The driving technique does vary considerably between FWD and RWD, but I don’t know what the relevance of this is to this discussion of chassis stiffness?

SO PLEASE in a quest for stiffness dont destroy your car... rear end roll in a FWD street car is favorable in comparison to a RWD RACE car.

Absolutely incorrect! For starters, if you increase roll stiffness at only one end of the car (by means of a stiffer ARB or stiffer springs) you will not just lessen roll at that end, you will lessen roll at both ends equally (though you will alter the weight transfer front vs. rear). Any difference in front and rear roll can only be allowed by the chassis twisting, and the degree of twist will be minute as far as any difference in front / rear roll angle is concerned.

If you have low roll stiffness in the rear end of any FWD car you will have substantial understeer because the IR won’t unload enough, and the IF will unload too much (also causing traction issues on acceleration out of corners). If you want an understeering road car then your comment is correct, and is why the car manufacturers almost universally set up their road cars with too little rear roll stiffness, i.e. so inexpert drivers don’t get themselves into trouble with oversteer.

LASTLY... stiffness is good for racing, not gonna lie... i see RWD mustangs lifting the inside front tire on acceleration... and i see FWD civic hatches lifting the inside rear wheel on braking... but only on a race track!

Sorry but this is just wrong. The best handling road cars, whether FWD or RWD or 4WD, have substantially stiffer chassis than run of the mill shopping trolleys. Again I’ll say that the IR (or IF front for a RWD) doesn’t actually have to lift for there to be a benefit to handling balance, all that’s required is for the roll couple to be moved nearer toward what may be the absolute ideal for whatever kind of car it is (i.e. FWD or RWD), it doesn’t have to go all the way as it would for a pure racer. Chassis stiffness is an important part of achieving this.

honda's last cause they designed them well, meaing low stresses and high design factors. in impact loading (sudden loads) stiffness increases stress ALOT! so as you are stiffing your car you are in fact reducing its life... Race cars dont last to 200,000 miles.....

Further up the page you say ; “(VERY BAD FOR THE CAR you are actually twisting the body in torsion’. Now you’re suggesting that NOT allowing the chassis to flex is increasing stress on the chassis? You can’t have this both ways!

I don’t dispute that increasing a localised stiffness in the chassis will to some degree transfer more load to some other part of the chassis and in theory could find a weak point that suffers as a result, but equally that part of the chassis that was previously flexing could fail as a result of the continued flexing.

In reality nearly all chassis are going to be able to cope with localised structural improvements without adversely affecting any other part of the structure, like you said they are well designed to cope with stresses without breaking. This will especially be the case if the car isn’t habitually driven at speed over rough roads. I have to say my CB7 has been driven over rough roads for the last few years with no noticeable increase in the number of rattles etc and still handles as well as it did since any modification to it’s structure, and I’m on Koni yellows at near full stiff front and rear.

Stiffening the suspension substantially is likely to impose far more stress on a chassis than stiffening the chassis itself. Porsches are well designed and far stiffer than the average Honda, they last a long long time.

[oneoffaccord]

I would, but I'm not really set up with the correct gear, I'd have to borrow a camera, then learn how to get the shots into the computer and then how to upload to the site, and I'm too lazy!

My 'X' brace looks very similar to that beige coloured one that someone else posted, but instead of sitting flat in the boot space it sits more or less vertically behind the seat back. It attaches to the rear parcel shelf metal work with two bolts on each side (the same two bolts that attach the stock angled sheet metal braces on each side of the seat aperture, which are also retained in front of the X brace), and at the bottom is bolted to two 3mm thick plates (one each side) that are attached to the chassis behind the stock braces, again using the existing stock brace attachment bolts (two per side). These stock chassis bolts are not as large as I'd like, but fitting larger bolts would mean dropping the fuel tank, which isn't likely to happen!

The X brace is designed to prevent the section of chassis behind the seat back (including the area between the strut tops) from 'trapezoiding' (is that a word?!) under load, and generally stiffen the rear of the chassis where the loads are imparted into it. I also have a rear strut brace that is also bolted to the centre of the 'X' in the brace (using two short tubes). I noticed improvement in response and understeer (i.e. less understeer) with both the strut brace and the X brace, strut brace probably more so than the X brace, but it's hard to say which really has the most affect since I haven't had the X brace fitted without the strut brace. I have to say I noticed no improvement when I bolted the strut brace to the X brace.

you got any pics of the x-brace?

[10thcb7]

I just want a list of the things we should do to improve the chassis and suspension

[oneoffaccord]

I just want a list of the things we should do to improve the chassis and suspension

if u are looking for things, u are better off using the search button for ur pleasure

[oneoffaccord]

would something like this would work? They dont make shit for a CB/CD chassis but anything is better than nothing.

http://www.emracing.com/products.html

TRIANGULATED TRUNK BAR





TRUNK WALL BRACE


TRUNK FLOOR BRACE

[10thcb7]

Front to back. ESP traction system, fender braces, 3-4 point Upper Strut, Floor Bar, Seat Harness bar, Under Carriage Brace "double-X", Trunk X bar, Rear Strut Tower, Rear V brace, does that sum up everything we know ?

[GreenMadness]

ok ... first off... what you responded with was what i was trying to say in the first place... but far to busy to actually take the time to type out which i thank you for.

Second, as a person that understands what you said, and already knew it, i know that there are some fundamentals behind your logic, that if others did not have, could cause a good amount of MISUNDERSTANDING... to others

I understood what you wrote although from the books i have, about half of it is from my RWD racing book, and the other half is from my FWD racing book.



In reference to you attacking my stiffness claims...
i was copy pasting to make this statment and fucked it up good

for cars the body roll is the suspension giving (its meant to) when you stiffen the car you reduce body roll

Should read

for cars the body roll is the suspension giving (its meant to) when you stiffen the suspension you reduce body roll

FWD racing is NEW only around 20 years and only the last 5 has it really taken off, because until the 80's Mcpherson Strut design used on the Honda Civic Manufactures couldn't turn and pull out of turns at the same time. Most though like you that FWD was just the opposite of RWD, unfortunatly those companys had there asses handed to them by garage mechanics just feeling the car and setting it to themselves.

the 2 brothers that raced a Mugen Acura Integra in the early 80's had two vey diffrent setups but could run the same times... it was found that the rear set was the big diffrence in how they drove the car, the conclusion was that unlike RWD where the rear set up is more important than front, because front only needed to turn... now almost all the importance was in front set up and little more than stability control for each individual driver was needed in the rear as long as the car/suspension was correct for the track and able to lift the inside tire, why the rear end is just along for the ride.

To clarify, i work at a race track, and see people that read info likethis, put braces and thick ass roll bars on there car... or evo IIIV's with huge roll bars and spherical bushings that are getting passed by a stock 90's audi quattro... with full leather interior and no mods and tons of body roll.

they hit the track and get horrible traction and when they turn it looks like the body wants to kill itself, because the chassis stiffness has not been brough up to par. thats the point i wanted to make that you tore up, all theses things are only effective if the car as a WHOLE is set up to take advantage of it....

NO OFF THE SHELF GROCERY GETTER IS... you said it yourself. so why are you giving out information on race car chassis set up and stiffining and racing suspension.

I was trying to say that race cars take a heavy amount of abuse because of the stiffness... if you are familar with the calculations in stress analysis for impact loading do them, the stiffer something is the more the equivilant static force is.

[lokuputha]

there is alot of information in this thread that seems dangerous and easily misinturpreted.

first, if you are serious about racing, the only goal for the rear end sway is a stiff enough sway bar to lift your inside tire going through turns.

I am designing the suspension system for my school Formula SAE car, and I have never heard of intentionally lifting the rear wheel to offer better turn in. If anything, a lifted rear wheel means the rear sway resistance is too high for the application and should be lowered.

correct me if I'm wrong.