iBang Posted October 25, 2011 Share Posted October 25, 2011 I've recently been doing a lot of reading on suspension tech and trying to figure out how I want to set up my Z. I now know a little more about terminology and what to look out for, but it doesn't help me a lot as the average Joe. I may now know what to tweak to compensate for certain handling deficiencies, oversteer, understeer, bump steer, etc, but without the money to go through tons of components the information isn't much good. What I would like to figure out is a good set of basics that will get me fairly close to the ideal setup to start with. Then I can adjust a few things to tweak it to perfect. First let me give some specs on the car for reference: '72 240Z. Power will be a RB25 tuned to between 350-450hp on pump gas with a garret 3076R. I'll be tweaking to optimize the car for street driving and a smooth power band. Interior will be complete and if possible I'd like to avoid as much in car bracing as possible. I'm still considering a rear section roll bar but I don't want anything with door bars for sure. Suspension is where the largest amount of custom work will be done so there is lots of room for adjusting it for maximum efficiency. Before I get to that let me talk about the car's mission. I'm building this car as a weekend street car. Something to be driven purely for enjoyment. Something to take on road trips to out of town car shows and events, nice dinners, and weekend drives. That means that there is a large emphasis on day to day drivability in normal street conditions. At the same time, it is to be driven for fun in the twisties and I'm willing to sacrifice some ride quality in the quest for improved performance beyond that of an average street car. Now, so far as the technology that will be going into the suspension: For various reasons I have decided to use modern S-chassis components as the basis of my suspension work. The front subframe is a S12 piece that will be used with modified S12 arms to get back to stock S30 track width (more on that later). Front knuckles will be S14 with 5 lug hubs. Steering rack will be from the S12 as well and will be a power unit. The rear subframe is still somewhat in the air. My original plan was to use a stock S13 rear subframe in complete form. I have amended that however to either modifying the stock subframe to reduce the track width to match the original S30 components or alternately designing a tubular rear subframe that would utilize all of the S13's arms and hubs in order to retain access to the excellent S13 parts available from a million manufacturers. The decision to modify or fabricate fresh will be determined when I start mocking up parts and seeing which direction will be simpler to achieve. Irregardless, S13 arms and geometry will be retained. All four corners will use S13 based coilovers, though if it is necessary, I may adjust valving and spring rates in order to better suit the S30. Given the versitality I have seen from stock S13 suspension and its ability to handle everything from lightweight drift cars to heavy V8 builds I don't expect to go down that road, but I leave it as an option. Currently I'm considering tein and driftworks coils, however that may change with more information. With all of that information in mind, I see several elements that need to be addressed: Spring rates - what is the ideal spring rate for a lowered S30 that is close to stock weight for street performance driving. Valving - should I have my S13 coilovers custom valved for any reason? Track width - I currently plan to run stock fenders, no fender flares. For appearance reasons I would like to flush up my wheels to the fenders and ideally would love to have some lip to the wheels. I'm not sure if I should adjust the track width any either front or rear in order to avoid any scrub radius problems while doing this. Anything else I have not yet thought of! Any opinions anyone can offer would be appreciated. I want to avoid as much trial and error as possible when building my suspension. Fabrication takes time and parts are expensive so I only want to do this once if possible! Quote Link to comment Share on other sites More sharing options...
lowdown Posted October 25, 2011 Share Posted October 25, 2011 Sweet, another austin guy! Well what is the major plan with it, seems like a bunch of work to gain very little. (not knocking, just curious) There are better race setups that flow with the factory car geometry, Arizona Z, Techno Tuning or something like that, and Modern Motorsports. Quote Link to comment Share on other sites More sharing options...
rossman Posted October 25, 2011 Share Posted October 25, 2011 (edited) I'm with lowdown. Why? Why go thru all money, time and effort for a setup that *might* get you marginally better performance than a modified stock S30 suspension? I *only* had urethane suspension bushings, Tokico Illumina struts and Eibach springs on my 280z. The car handled like it was on rails yet it was compliant enough to drive across Houston every day for several years. Edited October 25, 2011 by rossman Quote Link to comment Share on other sites More sharing options...
Zmanco Posted October 25, 2011 Share Posted October 25, 2011 I'm building this car as a weekend street car. Something to be driven purely for enjoyment. Something to take on road trips to out of town car shows and events, nice dinners, and weekend drives. That means that there is a large emphasis on day to day drivability in normal street conditions. At the same time, it is to be driven for fun in the twisties and I'm willing to sacrifice some ride quality in the quest for improved performance beyond that of an average street car. I'm with rossman, unless you plan to track it, there's no need to do all this, unless you want to Simple tried and true mods to the stock suspension will bring the performance envelope up to where you'll be at go-to-jail speeds by the time you exceed the car's limits. The biggest limitation I'm finding is getting enough camber recovery in the front. The unreinforced early Z has a soft chassis and hence doesn't do well with the stiff springs required and running enough static camber makes the car miserable on the street. Adding more caster helps, but the tires begin to hit the fenders in the front after about 3.5 degrees, which isn't enough. However, on the street, I don't notice a lack of front end grip - the overall cornering levels are already beyond what is safe to use on public roads. Again, unless you just want to do all this because you want to - a legitimate reason - go with Arizona Z cars springs, Tokico 5 way struts, MSA ARBs and a good set of summer tires and you'll have a blast carving canyons. If you want to go further, you can add coil overs and camber plates, but for the street that's not necessary. In fact, I'd argue that raising the cornering limit even further will probably have a sad ending when inevitably you overdrive the car on a public road and hit something, or worse. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 25, 2011 Share Posted October 25, 2011 I'll be tweaking to optimize the car for street driving Shocks are by far the most important thing in your suspension. You should spend 50% of you suspension budget on shocks along (not springs, not struts, not coil over kits, not camber plates - shocks). You will get more improvement for the suspension dollar spent from shocks then anything else you plan on doing. Tokico HTS/D-Spec or Bilstein P030 are probably the best for a street driven S30. Take the time and read the strut thread. Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted October 25, 2011 Share Posted October 25, 2011 (edited) With all due respect, I dont think s12 parts are that much more "modern" than s30 parts. The cars are still over 20 years old and utilize the same suspension design (mcpherson strut) as the Z cars, I dont feel you will find much of an improvement there. If youre indeed looking for "perfect" suspension, double control arm is what most people want up front. Only cars I know of that use those are the 3rd gen rx7 or the miatas. Perhaps looking at those is what you really want to be doing. If youre really interested in going with s14 hubs, s13 suspension, s12 subframe I have to ask.. why not just buy a 240sx parts car and go about swapping the whole suspension over to the Z car? The amount of work will be roughly the same since youre still going to have to modify pretty much everything to make it work. At least this way you will have a whole working car to start off of, you never know what other parts you may need. There is no "ideal" spring rate/shocks/alignment/etc, you chose that based on what kind of driving youre doing and how you would like the car to behave. If you search around you will find some good starting points for stock suspension Z cars. For your car it is unlikely those will work for you, I would expect several iterations of suspension tuning to get things where you want them. As the others have mentioned though, this is all theoretical, bench racing kind of talk. Fair enough, you might finish the car and it might handle great, but the actual improvement over a well setup s30 using the stock suspension might not really be as much as you would expect (or not at all). Going with "modern" s12/13/14 parts wont really save you money either. Z car parts are still plentiful and cheap. Z cars also have plenty of options for performance parts to suit almost any price range or application. Edited October 25, 2011 by h4nsm0l3m4n Quote Link to comment Share on other sites More sharing options...
johnc Posted October 25, 2011 Share Posted October 25, 2011 Please remember that this is HybridZ. We are all about heavily modifying the S30 so swapping in a suspension from a different car is fine as far as we are concerned. There may be some discussion about whether the swap is an improvement or not, but the swap itself is cool. Quote Link to comment Share on other sites More sharing options...
iBang Posted October 25, 2011 Author Share Posted October 25, 2011 (edited) Great points guys. Some of the reason is actually cost related. I parted out my drift S13 a couple years back leaving me with a beautiful set of SPL rear arms for S13, a complete rear subframe and differential, 5 lug hubs, etc. I also have the complete front end with the 5 lug S14 setup, tension rods, etc. I happened on a S12 subframe for some other cheap parts I wasn't going to use so I have that already. I have a complete set up mock up tein coilovers which depending on their performance might be ideal to send off for a rebuild and just use. In fact the only parts I'm missing for the complete swap are a set of camber plates to allow me to use the pillow ball mount coilovers, and a set of custom axles for the reduced track width of the S30. Other reasons are performance or advantage related. The front end of the S30 seems to be its weak point and it also lacks power steering. I had already planned on using S13 coilovers to take advantage of the wide range of parts out there, so going ahead and using the S12 rack and subframe with the S14 knuckles gains me power steering, a more solid front end, and I can just bolt up the bottom side of the coils instead of having to customize them. Another added bonus is the ability to use a set of Z32 front brakes I already have and the option to upgrade to any of the many big brake kits made for the S13/14. On the back side there's a few performance reasons as well. You can argue the advantages of multi-link vs. the original Z setup but I'm not going to get into that. I like the ability to use a easy to find shortnose diff (which I already have) for starters. I also like the fact that I'll be able to bolt up Z32 rear brakes (or any of the other big brake kits) and keep a hand brake without having to resort to a lot of custom work. The 5 lug hubs are also a bonus to expand my wheel selection. Frankly most of the rest of it is cost related. By my estimation it would cost me between $2-4k to buy all of the various bars, arms and what not to go through the entire rear end. Then I'd have to add on some more budget for a decent diff. Now all of this aside, the back end is still something I could be convinced to go ahead and use the S30 setup on since there's not a big performance advantage, but I would have to be convinced it could be done without blowing the cost through the roof. Its also worth mentioning that I am a fabricator and have access to all of the tools necessary to modify the front and rear subframes as well as mount them up to the car in house. There isn't a cost component there for labor to have that done. The only costs for all of that will be the raw materials and gas for the welder and what not. One thing I notice a lot of emphasis on is the bilstien/tociko shocks as opposed to a typical S13 type coilover system. Any reason behind that? (I'll be reading the shock thread in a minute, thanks for the heads-up on it) I've had great experiences with my various S13's on a quality set of coils which inspired me to go that direction with my S30. Of course on the S13's I was simply buying known quality components and bolting them up to the car. With the Z I'm taking a lot more pains to understand what each modification will do to the suspension and have a reason for each one. Adjustable arms are easy enough to understand - adjustability is always a good thing, but I'm less certain as to what shock will offer the best behavior and valving. Edited October 25, 2011 by iBang Quote Link to comment Share on other sites More sharing options...
Leon Posted October 25, 2011 Share Posted October 25, 2011 Judging by your stated needs, there is no reason to go so custom on the suspension. Sure, it would be cool but not cost, nor time-effective. I would sell all that stuff you have and get S30 parts as others have suggested. You want something fun to drive around on the street, and for that I think you will be satisfied with stiffer springs, matching shocks (as John points out, this is key), poly bushings, and maybe larger ARBs. This will be much less time and energy intensive and definitely cheaper than going a fully custom route. If you feel like building something, take a look at all the threads on building control arms and coil-overs. This will give your suspension some adjustability, but I just don't see a reason for it from the intended use of the car. There is absolutely no need to get 300ZX brakes and an R230 rear end for what you're doing. Again, it would be cool but not necessary. Stick with a simpler plan and you'll have the car on the road much quicker so that you can enjoy it! As Stepan also pointed out, there is no such thing as a "perfect" suspension. Suspension design always involves compromises. Ride quality and road handling have an inverse relationship, mostly dictated by the dampers. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 25, 2011 Share Posted October 25, 2011 One thing I notice a lot of emphasis on is the bilstien/tociko shocks as opposed to a typical S13 type coilover system. Any reason behind that? EDIT: Actually, the main reason for the emphasis on Tokico, Koni, and Bilstein is those are the shocks we've been using for 40+ year racing the S30. They work, they work well, are available for reasonable prices, and, in the case of Bilstien and Koni, are rebuildable and revalvable for around $100 a shock. The second main reason is: Compression damping rates and shock-to-shock quailty. In general (and I know that's a pretty broad statement) the aftermarket coil over JDM setups have too much compression damping (same with the Tokico Illumina) for good handling. There is also large variations from shock to shock in damping. You buy a $1,200 coil over kit for your S12 and the damping variation is such that shock 1 on setting 5 is the same as shock 2 on setting 8. Now, 99% of the drivers out there won't notice that difference except that the car might feel better on left turns then on rights. Quote Link to comment Share on other sites More sharing options...
iBang Posted October 25, 2011 Author Share Posted October 25, 2011 (edited) Judging by your stated needs, there is no reason to go so custom on the suspension. Sure, it would be cool but not cost, nor time-effective. I would sell all that stuff you have and get S30 parts as others have suggested. You want something fun to drive around on the street, and for that I think you will be satisfied with stiffer springs, matching shocks (as John points out, this is key), poly bushings, and maybe larger ARBs. This will be much less time and energy intensive and definitely cheaper than going a fully custom route. If you feel like building something, take a look at all the threads on building control arms and coil-overs. This will give your suspension some adjustability, but I just don't see a reason for it from the intended use of the car. There is absolutely no need to get 300ZX brakes and an R230 rear end for what you're doing. Again, it would be cool but not necessary. Stick with a simpler plan and you'll have the car on the road much quicker so that you can enjoy it! As Stepan also pointed out, there is no such thing as a "perfect" suspension. Suspension design always involves compromises. Ride quality and road handling have an inverse relationship, mostly dictated by the dampers. I'll take a look at the cost of parts for the rear suspension and do the math on it. If I can make the numbers stay at least close to black by selling off the S13 parts I'll consider it. Time effective is less important here than cost to me... at least for the moment! As for the brakes and rear end, remember, this car is going to put 400hp to the ground and I'd like to have the brakes to match that. Honestly 300ZX brakes are the minimum I would want. I'm also pretty sure that the stock diff for the S13 is a shornose R200 not a 230. That is a smaller concern though - I can always track down a longnose R200 and get the strength I need and retain stock mounting. EDIT: Actually, the main reason for the emphasis on Tokico, Koni, and Bilstein is those are the shocks we've been using for 40+ year racing the S30. They work, they work well, are available for reasonable prices, and, in the case of Bilstien and Koni, are rebuildable and revalvable for around $100 a shock. The second main reason is: Compression damping rates and shock-to-shock quailty. In general (and I know that's a pretty broad statement) the aftermarket coil over JDM setups have too much compression damping (same with the Tokico Illumina) for good handling. There is also large variations from shock to shock in damping. You buy a $1,200 coil over kit for your S12 and the damping variation is such that shock 1 on setting 5 is the same as shock 2 on setting 8. Now, 99% of the drivers out there won't notice that difference except that the car might feel better on left turns then on rights. Interesting... I'll have to do some more research and see if I can't find out some more information there. I've had my best luck with S13's using the higher end tein stuff, but as I've mentioned before, I've never gone into detail with the tech on it. Maybe a set of bilstien's will do what I want. Do they make a short body shock that will allow me to get a reasonable ride height without losing all of my travel? Keep up the info guys! This is the information I was looking for! Edited October 25, 2011 by iBang Quote Link to comment Share on other sites More sharing options...
iBang Posted October 26, 2011 Author Share Posted October 26, 2011 (edited) Ok, I did a little more research and this is what I turned up: AZC setup for all the rear stuff I would want would set me back $1620 with no brakes or coils. The full race setup ready to go would be over $7k for all four corners with brakes and coils The rear end setup isn't actually that bad - I'll have to do some serious thinking about what I want to achieve before I start hacking on the S13 stuff. I can probably only get $5-600 for my existing parts so I'd be out another thousand or so, but I would save myself an awful lot of work. I also went and read the shock thread... my head is officially spinning. What emerged from all of that information is that the accepted tried and true setups are for the "build your own coilover" type shocks including bilstein and koni. That does make me a little sad as I was hoping to purchase a ready to go coilover system and install it. I figured there had to be something acceptable for street use that could be purchased as a complete package. The reason I would prefer to avoid the stand along shock setups is that as I suspected, I saw a lot of information in the thread to the effect of ...tweak in your spring rates and valving to get to how you want the car. That's all well and fine for an car that will see track duty but certainly there is an off the shelf setup for the street that will not require me to go through multiple springs and valving adjustments to get right. One thing of note is that I see that AZC actually offers a complete set of coilovers for the S13 chassis. There was not a lot of information on the AZC stuff in the shock thread, but it certainly seems to have a following here. Perhaps their offerings in the S13 market would be the way to go in order to get a complete package coilover since I plan on using the S13 parts anyway. I did do some searching for test results on the various coilovers that I am aware of and found mixed results on most of them. I did get fairly positive results for BC racing and tein, but both were qualified as "not ideal but acceptable for the street". BC is a bit tempting as I actually have a good friend that is employed by them as well as being one of their sponsored drivers, so I would likely be able to get a lot of support for choosing the best possible unit for my application... and maybe a few bucks off the list price if I'm lucky. I'm starting to move away from tein since all I could find were a few "its acceptable" comments and my own experiences in S13's. I'm beginning to see that an awful lot of the information I was searching for is a matter of opinion. One thing however that doesn't seem to be that way is spring rates. From what I can gather, a good place to start building a setup is to choose rates and then decide on the rest of the components to match. Any suggestions on that front? Edited October 26, 2011 by iBang Quote Link to comment Share on other sites More sharing options...
Snailed Posted October 26, 2011 Share Posted October 26, 2011 My $.02 on the rear suspension idea - I am doing almost the same thing for my rear suspension and I think it makes a lot of sense. It's a fraction of the cost to adapt a skyline/q45/240sx rear subframe rather than build up the s30 rear suspension. I'm using a narrowed q45 so I end up with aluminum uprights and bigger output shafts on the R200 (same as skyline) and it has a VLSD already also. Adapting it to the car means you can mount it so the suspension geometry is good at whatever ride height you choose. that is not an option with stock S30 LCA pickups. It's nice to not have to use the weak s30 hubs too with a powerful engine too. Anyway, I have $300 in the setup so far and I plan to add is a set of r33 rear calipers and a couple of shortened halfshafts which will be another $300 or so. So $600 for 5lug, lsd, 2 piston calipers, strong halfshafts, light hubs and good geometry? Sounds good to me. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 26, 2011 Share Posted October 26, 2011 And how much are you paying for shocks, springs, bushings, etc? Quote Link to comment Share on other sites More sharing options...
iBang Posted October 26, 2011 Author Share Posted October 26, 2011 My $.02 on the rear suspension idea - I am doing almost the same thing for my rear suspension and I think it makes a lot of sense. It's a fraction of the cost to adapt a skyline/q45/240sx rear subframe rather than build up the s30 rear suspension. I'm using a narrowed q45 so I end up with aluminum uprights and bigger output shafts on the R200 (same as skyline) and it has a VLSD already also. Adapting it to the car means you can mount it so the suspension geometry is good at whatever ride height you choose. that is not an option with stock S30 LCA pickups. It's nice to not have to use the weak s30 hubs too with a powerful engine too. Anyway, I have $300 in the setup so far and I plan to add is a set of r33 rear calipers and a couple of shortened halfshafts which will be another $300 or so. So $600 for 5lug, lsd, 2 piston calipers, strong halfshafts, light hubs and good geometry? Sounds good to me. Much the same idea I had. I may use the Z32 aluminum uprights for less unsprung weight, but frankly if I do, I'll likely do it down the road since the 240SX stuff is proven to work fine on LS6 powered drift cars under huge abuse on the track. And how much are you paying for shocks, springs, bushings, etc? Wouldn't you have the same problem with the S30 stuff as well though? Irregardless of what setup you go with you are going to want to freshen up the bushings and replace the shocks and springs with something aftermarket. Is there a significant price difference for the S30 parts? Honestly curious there since I know I'm going to be spending quite a bit in poly bushings on the 240SX stuff. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 26, 2011 Share Posted October 26, 2011 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 Quote Link to comment Share on other sites More sharing options...
iBang Posted October 26, 2011 Author Share Posted October 26, 2011 $300 is about right for a complete rear subframe with a differential, at least in the 240SX community for something in decent shape. I bet the numbers come in pretty close for the S13 stuff. Assuming a decent set of coilovers is acceptable for your purposes, half a set would be $600 and that would include the spring, collars and plates. Really the different is going to come down to busings since technically you could get the S13 equivalents to all of the parts you sell for the same price and have the same setup. Where the question is going to come in is aftermarket parts. This is comparing a completely stock S13 rear end to a completely stock S30 rear end. I would consider the proper setup for a S13 with performance parts to be Rear upper control arms ($350) and toe rods ($280). That's $630 in aftermarket parts. Likewise I would want to have rear lower control arms ($425) and a fresh mustache bar ($230) which is $655 in parts. It would be more if you added on the billet diff brace and less if you ditched the bar. Looking at it that way its pretty darn close between the two, both using quality race proven parts (SPL, AZC and techno toy tuning). Heck the more I look at it, the more of a toss up it becomes. You could go either way and by the time you get done putting it all together it will probably be a wash. For me I already have the parts, so it makes it a lot cheaper to go that way, but then again it is more work. I'll cross that bridge when I get done with the front end. In the mean time, I am still focused on determining the easiest way to get a quality shock/spring package for the road that comes as one package. I didn't know you had something you were selling though John, would that make for a decent road package for my Z or is it more race focused? Quote Link to comment Share on other sites More sharing options...
Zmanco Posted October 26, 2011 Share Posted October 26, 2011 Is the weight the same? I haven't seen a 240sx subframe, but seems like that would add weight assuming the other parts have comparable weights. Quote Link to comment Share on other sites More sharing options...
iBang Posted October 26, 2011 Author Share Posted October 26, 2011 (edited) Good question, I don't have the figures on that. There certainly seems to be a lot less to the Z's rear suspension which would suggest that it is probably a lot lighter. The arms are a lot larger however so there may be more unsprung weight, but that is just conjecture on my part. Good point nonetheless - a hundred pounds would be a hundred good reasons to stick with the original setup. Of course if I do go with a completely custom subrame that uses the S13 arms and geometry then everyhing is out the window. Edited October 26, 2011 by iBang Quote Link to comment Share on other sites More sharing options...
iBang Posted October 26, 2011 Author Share Posted October 26, 2011 (edited) The 240SX unit is going to be heavier for sure... here's a comple of pictures for comparison: There's definitely more steel in the S13 subframe to account for all of the mounting points for the various arms. The arms are a lot smaller however so I may or may not be right on my unsprung weight conjecture. There's certainly a lot more arms on the S13 which may compensate for the longer ones on the S30. Edited October 26, 2011 by iBang Quote Link to comment Share on other sites More sharing options...
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