Chassis Bracing Components

[Scooby]

Just saw an article on Whiteline's kit for the Dugong ie latest model WRX, including fairly straightforward underbody chassis bracing. Despite the fact that there's probably a good market, I suspect it will be quite some time before they produce similar for Skylines, if ever, unless Sydneykid can convince them otherwise.

The R32 GTR could do with a bit of stiffening and most of us are using front and rear strut braces. The only other thing I've seen around is the Do Luck brace that goes across the tunnel and bolts to the inner sills but I'm not sure it does much. Of course a cage would do the trick but it's illegal for road use. The R33 GTR has a big panel between the rear shock towers that seems to keep both of them moving in the same direction quite well, and the R34 GTR improves on this again.

There is a lot of stuff in Japan - various brackets etc but I'm not sure of their effectiveness. Last thing I want to do is add 10 kg of weight for no improvement in rigidity.

Has anyone got experience with Japanese stuff or their own, that actually works?

Cheers

Edited March 25, 2008 by Scooby

[farch]

B pillar brace tried it in 180 sx and R32GTR, no noticable difference.

Front and rear strut braces are most effective though.

[STRYKR 33]

Toda Racing are distributers of 'Ultra Racing Performance Bars'

Heres a link to the components:

http://www.ultraracing.com.my/ultraracing/ProductData.asp

[Beer Baron]

Kansai service centre sell a whole packaged of underbody braces/brackets for the R32 GTR. I have no idea if they work or not though.

http://www.hkskansai.co.jp/html/parts/roa/roa.htm

[Sydneykid]

Unlike the Wrecks, Skylines have good suspension pick up point rigidity, which should not be confused with general chassis rigidity. Obviously in the areas of general chassis rigidity R33's are an improvement over R32's and R34's are even more rigid. What is perhaps not so obvious is that series within those model changes have chassis rigidity improvements. Mostly as a result of mandated improvements in occupant safety. Hence an R32 S2 (post 1990) is more rigid than an R32 S1 (1989/90).

I can say without exception that I have yet to see any bracing that I would consider worthwhile. Simply put, they all fail the triangulation test.

Cheers

Gary

[Rinse It]

I've got a Nismo (at least I thought it was Nismo) full underbody brace kit installed on my R32 GTR... freakin' solid and massive amounts of "feeling" through the wheel with exactly what the car is doing...

[GTR-32U]

I've got a Nismo (at least I thought it was Nismo) full underbody brace kit installed on my R32 GTR... freakin' solid and massive amounts of "feeling" through the wheel with exactly what the car is doing...

I know I am asking a lot here...but any chance you could post up a pic of the one you got fitted ??...

[Scooby]

Unlike the Wrecks, Skylines have good suspension pick up point rigidity, which should not be confused with general chassis rigidity. Obviously in the areas of general chassis rigidity R33's are an improvement over R32's and R34's are even more rigid. What is perhaps not so obvious is that series within those model changes have chassis rigidity improvements. Mostly as a result of mandated improvements in occupant safety. Hence an R32 S2 (post 1990) is more rigid than an R32 S1 (1989/90).

I can say without exception that I have yet to see any bracing that I would consider worthwhile. Simply put, they all fail the triangulation test.

Cheers

Gary

Hi Gary

so...you're going to start making the good stuff for us? or are there reasons why it's simply not production feasible? also is it feasible at all or are there fitment / design issues that make it impractical to pursue rigidity improvements unless it's a full cage ?

Cheers

Edited March 26, 2008 by Scooby

[Sydneykid]

I've got a Nismo (at least I thought it was Nismo) full underbody brace kit installed on my R32 GTR... freakin' solid and massive amounts of "feeling" through the wheel with exactly what the car is doing...

I am not a big fan of seat of the pants judgement, the placebo effect is strong in car modifications. In a pure technical sense I have yet to see a value for money result as far as improving torsional rigidity goes. The testing is actually quite simple, a basic home garage test of rigidity. Stick the car on 4 stands, under the sills is OK. Then jack one corner of the car up 100 mm and see how much the other corners move. I do that 4 times, once for each corner. Now bolt on any number of underfloor, in cabin, under bonnet and in boot braces. Then repeat the test. Note any differences. An example, my own R32GTST before and after the 6 point roll cage fitment across the chassis.

LHR 100 mm - RHR 87 mm before, 93 mm after

RHR 100 mm - LHR 86 mm before, 92 mm after

LHF 100 mm - RHF 91 mm before, 95 mm after

RHF 100 mm - RHF 90 mm before, 94 mm after

That's obviously the across, you can also do along, put the jack in the middle, again under the sill and measure;

Centre LH 100 mm - LHF 90 mm before, 95 mm after

Centre RH 100 mm - RHF 91 mm before, 96 mm after

Centre LH 100 mm - LHR 90 mm before, 94 mm after

Centre RH 100 mm - RHR 91 mm before, 97 mm after

This is not an absolute test as the chassis walks on the stands, it is a comparison test only. So when you do it yourself don't get hung up on the numbers themselves, the difference (improvement) is all that matters.

The other test is corner weights, how many mm of adjustment of the spring seat on one corner alters how much weight on that corner. A soft (flexible) chassis means more turns to achieve the same weight transfer as a rigid (inflexible) chassis. That is a more reliable real world test as it is the wheels that move up and down and that is what is passed though the chassis. That's how we tell when a V8Supercar chassis is due for replacement, it gets lazy in its response to changes, hence why a new chassis is built each season. Usually around Bathurst time as long distance events show up any lack of rigidity.

Cheers

Gary

[bnr#@]

Unlike the Wrecks, Skylines have good suspension pick up point rigidity, which should not be confused with general chassis rigidity. Obviously in the areas of general chassis rigidity R33's are an improvement over R32's and R34's are even more rigid. What is perhaps not so obvious is that series within those model changes have chassis rigidity improvements. Mostly as a result of mandated improvements in occupant safety. Hence an R32 S2 (post 1990) is more rigid than an R32 S1 (1989/90).

I can say without exception that I have yet to see any bracing that I would consider worthwhile. Simply put, they all fail the triangulation test.

Cheers

Gary

I would have to argue that... true that it is ideal to have a 3 point brace for that brace to be as rigid as possible however you are not after multi directional rigidity in a lot of situations. For instance the plain old strut brace works wonders and is a 2 point brace (in most cases anyway). It works fine because its job is to tie 2 points together and stop the distances between those two points getting greater or smaller hence preventing suspension geometry change through chassis flex...

same would apply underneath the car for chassis flex as I would imagine that when the car goes over a ripple strip or just leans hard under heavy cornering on one side that the chassis would have a tendency to flex in the middle. By tying the 2 chassis rails together with a brace (or 3) you would help prevent this flex...

[Scooby]

In a pure technical sense I have yet to see a value for money result as far as improving torsional rigidity goes.

so all up there's not much that can be done to improve torsional rigidity at reasonable cost? we pretty much have to do with what we've got?

[Swiper the Fox]

i have some AutoSelect A-pillar braces fitted to our racecar. When combined with a tower brace gives an ultra stiff front end. They tie the strut tower to the door a pillar...every little bit helps!

[BHDave]

I would have to argue that... true that it is ideal to have a 3 point brace for that brace to be as rigid as possible however you are not after multi directional rigidity in a lot of situations. For instance the plain old strut brace works wonders and is a 2 point brace (in most cases anyway). It works fine because its job is to tie 2 points together and stop the distances between those two points getting greater or smaller hence preventing suspension geometry change through chassis flex...

same would apply underneath the car for chassis flex as I would imagine that when the car goes over a ripple strip or just leans hard under heavy cornering on one side that the chassis would have a tendency to flex in the middle. By tying the 2 chassis rails together with a brace (or 3) you would help prevent this flex...

Not really. the car can still twist the same as ever.

Front strut braces are ok as it ties a point thats close to the inner upper control arm to another point close to the inner of the other upper control arm. so yes, they are good at effectively boxing that section of the car and yes, it improves it. The same can be said for the rear to a lesser extent, as the upper contol arm mounts to the subframe so bracing the strut tops has less effect. The load of the rear struts is almost all vertical, only minimal horizontal. They don't move towards each other or away from each other to any great extent anyway, the main concern is the vertical loading. Whats bracing against that if you have a strut brace running horizontally?

And again, whats stopping the front end of the car twisting one way while the back twists the other? It's effectively a torsional force so bracing two rails together to form a ladder is doing 2/5ths of f*&k all to brace against it.

[Scooby]

And again, whats stopping the front end of the car twisting one way while the back twists the other? It's effectively a torsional force so bracing two rails together to form a ladder is doing 2/5ths of f*&k all to brace against it.

that seems to be the downfall with underbody braces - they don't have anything that braces across the chassis effectively in the direction of the force. i'm not sure how you could achieve that without having height in at least one domension of the brace with the other dimension being across the chassis, such as the panel at the rear of the R33 GTR. the underbody stuff would help if the problem was with the front meeting the rear in a horizontal plane, but its not.

[Duncan]

pics please paul! I need ideas for how to get the cage to the strut towers while still keeping the booster

[Swiper the Fox]

pics please paul! I need ideas for how to get the cage to the strut towers while still keeping the booster

ill duck up to the shed and snap a few pics.

[Swiper the Fox]

pics please paul! I need ideas for how to get the cage to the strut towers while still keeping the booster

bit hard to get a decent pic...but these will give you an idea.

NOTE...these are nothing like the AutoSelect ones...the jap ones are much beefier with cross bracing as well. But display's the general idea.

[godzl1975]

Would pop riveting inside the engine bay to the door sills be any good? i know disadvantage is the little extra weight of the rivets. Thats how my car came from japan and it also have similar to what dirtgarage but does extend as far, by AS.

Probably getting more spot welds would be better than riveting.

[Sydneykid]

bit hard to get a decent pic...but these will give you an idea.

NOTE...these are nothing like the AutoSelect ones...the jap ones are much beefier with cross bracing as well. But display's the general idea.

I have seen that bracket used as the mount for the front on board jacking system.

Cheers

Gary

[Sydneykid]

Would pop riveting inside the engine bay to the door sills be any good? i know disadvantage is the little extra weight of the rivets. Thats how my car came from japan and it also have similar to what dirtgarage but does extend as far, by AS.

Probably getting more spot welds would be better than riveting.

Rivets work loose, not a good idea. Extra spot welds or stitch MIG/TIG welding is a far superior solution.

Cheers

Gary