johnc

I agree, the equal and opposite reaction thing. I'm not arguing otherwise. I agree. I just look at it the way I describe for suspension tuning reasons. You may not agree with how I look at it, so be it. Look at it your own way. Draw all the little pictures you need. I don't need them. And, back to the original point, a single bolted clevis is just fine for a TC rod attachment to the front LCA.

All of the TC rod failure that I have seen or heard about were the result of: 1) Bending loads on the arms caused by lack of articulation in the chassis mount. 2) Impact loads from a wheel hitting a curb or a big pothole. In scenario #2 above I agree 100% that the TC rod takes the vast majority of the load. But that is not the same as loads induced under braking.

I think we are all saying the same thing in different ways. The way I look at it is: the brake caliper is trying to rotate forward on the spindle as a torque load when the brakes are applied. This torque is resisted by the strut (shock, strut tube, top mounting), LCA, and TC rod. EDIT: Are some people thinking that braking loads are the same as if the front tire hits a curb while not under braking?

Not that much and there's no relationship between the two numbers. The TC rod is a suspension link and only sees loads from locating the spindle. If the TC rod is broken the LCA can still be reasonably located with the anti-roll bar end links or even poly LCA bushings. That shows that the fore/aft loads are fairly low. There are no vertical loads on the TC rod.

Braking force is only torque. Just like acceleration loads are only torque. Those loads are transferred to or from the chassis via the suspension links. And ALL of the weight of the sprung mass of the vehicle is supported by the springs. How could it be otherwise?

Correct. And that does show that the TC rod primarily performs a locating function and doesn't support a large braking load. If an anti-roll bar end link with a class 8.8 10mm bolt can keep the LCA located or poly LCA bushings can keep the LCA relatively in place under braking then then fore/aft loads must be low.

Good book and it will change your thinking.

Braking load on the suspension is a torque load, not a linear load - brake caliper clamping rotor. That torque load is spread through three mounting points (LCA, upper shock, TC rod mount). The TC rod is just one leg of a virtual A arm with the LCA the other leg. The chassis does not push against or lean on the TC rod under braking. All the TC rod does is stabilize the outer end of the LCA. I've driven a car on a race track with a broken TC rod and yes, the car pulled to that side because the rod was broken and that LCA moved rearward but the car still stopped reasonably well and let me get back to the pits. The front suspension didn't collapse, the car didn't explode.

In CA there are signs before the weigh stations that say rental trucks have to go through the station. Its been that way for at least 15 years that I can remember.

So... when was the last inspection done?

Not true. Vehicle weight and the weight transfer under braking is taken by the springs which is pretty obvious because they compress under braking. The loads the TC rod sees are minor compared to that. The single bolt clevis is fine.

There is a more 1 to 1 ratio when attaching the ARB to the strut tube. In essence the ARB is stiffer and its also more responsive to wheel movement.

I spray the back side of panels I'm welding with 3M High Zinc Weld Thru Primer and also spray Wurth Body Cavity Spray into body cavities through small holes I drill. Be sure to drill those holes on the bottom of the cavity so any water that might get in has a chance to drain.

Its a GTR with a Juke body on it.

That's a better way to do it Kazu.

My "No" was an answer to your caster goal and not having to cut the bodywork giving your wheel and tire combo. I had to cut my old car when running 225/50-15s once I got past +5 caster.

Guys, do the swap. Its cool.

I'm always surprised at how quickly folks new to the S30 world discount or ignore what the old hands have learned racing these cars for decades. And how quickly they toss aside the OEM parts figuring the aftermarket makes better. Well, that's not always true: http://forums.hybridz.org/index.php/topic/102968-aftermarket-control-arm-failure/ I don't want to sound like an old curmudgeon. Again, its cool if you want to replace the front and rear suspensions on the car. But that's primarily an emotional decision or something to do to see if it would work - and just plain fun to do. You don't need to rationalize it in any way by citing costs, better performance, etc. If its something you want to do, go for it. What I get grumpy with is when people try to assert that their mod is better then what originally came on the car, with their only proof being that their parts are a newer design.

The stock rear LCAs on a S30 have been race proven for 40+ years. You do not need to replace them to win road races even with power levels approaching 400hp. The folks running the current Easy African Safari Rally run stock 280Z rear LCAs with Energy Suspension bushings. I know, earlier this year I sent ten sets of the bushings and twelve LCAs to a six car S30 race team that's headed down there now. These are 300+ horsepower 240Zs racing across dirt paths in Kenyan and Tanzania. http://www.eastafricansafarirally.com/

No.

Regarding the gusset, there's nothing to weld the gusset to on the top and bottom of the LCA as designed. Are you thinking about a truss?

I just tried to come up with a solution that worked using his existing design. Without seeing the failure I'm assuming that the plate itself is strong enough to handle the loads. I'm assuming the failure was caused by a concentration of stresses that produced a crack(s) and then that crack(s) propagated out and reduced the yield point of the plate until it failed. This failure took time to occur and wasn't just an instant failure. By in essence making the tube a solid clevis and then welding the plate into the slot of the clevis you're eliminating the stress concentration and resulting crack propagation point. Again, I'm assuming that the builder wants to continue with the basic design. EDIT: "I think" this design is lighter then the TTT LCAs.

I was just questioning his claim about spending only $300 to get the whole rear subframe and suspension in while excluding the cost of new shocks, springs, bushings, etc. (the diff, halfshafts, etc. and not relevant to the discussion of suspension). You don't have that $300 expense if you use the stock S30 rear suspension. Are the shocks, springs, bushings, etc. cheaper for the 240SX multi-link rear? If we are going to do cost comparisons we have to compare apples to apples. Here is one way of doing the rear using stuff I sell: Tokico HTS102Fs are $180.22 each ($360.44) Coil over threaded collars - per pair ($88.00) Camber plates - per pair ($185.00) Rear LCA poly bushings ($45.00) Rear ST 19mm ARB ($189.33) Hypercoil springs - per pair ($147.00) Rear suspension part total is: $1014.77

This book is good: "Construction of Tubular Steel Fuselages" by Vex Aviation. You can get it from here: http://www.actechbooks.com. He can keep the same basic design but use a solid bar with a cut slot for the flat plate junction and then weld the solid bar into the hollow tube using a scarfed joint. The tip of the solid bar that's welded to the plate should be rounded and welded all around with no undercut.

I make a post here and then it goes away. Damn Admins! I agree that structural foam can help the stiffness of a chassis. But in the context of this site and this thread, its a losing proposition for a 40+ year old S30. I've cut open and repaired at least a fifteen S30 rocker panels. Every singe one had at least surface rust on the inside. Granted, that is a self selecting sample because those people brought me cars to fix rust issues, but you get my point. You can achieve better results for less money by installing Bad Dog subframe connectors and the car will remain repairable. Also, I disagree with this statement from SCC: "In any high-performance car, it is impossible to make the chassis too stiff." The Solo2 national championship FP E36 BMW is quicker without a front STB. Same is true for other cars, especially in the front. A too stiff front can overload the front tires on turn in and slow response. Sounds counter-intuitive...