240SX IRS Swap

[260DET]

Anyone tried fitting a Supra double A arm front suspension setup into a S30, S130, Z31?

 

With the Z31, replacing the semi trailing arm cradle assembly with a later multi link cradle assembly makes a lot of sense. But thats quite a different proposition to doing the same with a S30 and lets face it, anything would be better as far as the Z31 goes

[maichor]

I was asked to chime in here so I will do the best I can. First of all, my reasons for doing the swap are posted in my initial writeup here: http://forums.hybridz.org/showthrea...0&highlight=s14

 

So, on to the questions. Ed260Z asked:

 

1)What insulators are you using to mount the new Sub frame to the Chassis?

**I bought a complete Rear IRS Z32 bushing set for a Z32, Solid mounted the front and used the extra front pieces as spacers for the rear to correct my driveline angles.

2)Will I have drive shaft problems since the Diff will be mounted in the center, instead of offset by 3/4"?

**That depends, short answer, no. Your driveshaft will be longer and slightly more forgiving since the angles created will be less and they tranny output and diff will both still be parallel to each other. Since I did a motor swap as well, it was better that it was not offset as much. Mine is still 1/2 offset because I took 1" out of one side of the subframe. (won't change any of the arm geometry)

3)Can I bolt on the S30 Shock "Hat" to mount the 240SX Strut to the stock location on the Chassis?

**Yes, I used S14 coilovers and the S30 upper insulator.

 

4)Why use the S14 over the S13 sub-frame?

**I think the S13 sub-frame will work just fine, but you definitely want to use other arms. To quote myself-"S14, however, all of the arms are swappable except the lower control arms. For example, if you wanted to run the aluminum hub housing from a 300ZX (Z32), you could, but you would also have to have the lower control arms from the Z because the ball joints on the LCA are different. Also, I believe the S13 hub assembly is different than the S14 so you would have to use S13 axles with the hubs (Smaller than Q45 and 300ZX). With the S14 there are four bolts holding the hub on and one giant nut holding the whole assembly together. Maybe when I get home I can post a pic of the hub assembly. I would go S14, just so you have more options later." This means that if you use S13 lower arms, you cannot swap hubs with Q45 and Z32 unless you buy a different hub carrier from one of those cars and the corresponding lower control arm with it.

 

5)Do you need a spacer in between the rear mount and the frame?

Most likely yes, unless your motor is mounted lower than stock. That is to keep your driveline angles correct. You can use the rear spacer height to get it the vertical angles right. Or, you can do it at the front diff mount, but I wanted that to stay stock or it might put pressure on the studs coming out of the rear of the diff cover.

 

Now for everyone for or against:

 

There are no upper arm mounting point issues with my swap and I didn't move the arm. You can get the axles made any width custom from Moser for $375 for the pair. I used the larger Q45/Z32 size. S14 hubs will use a smaller axle.

PERFORMANCE: I have had this in running in my car for some time now and I love it. I am NOT however, a racer. I drive on the street. I feel it is more predictable and forgiving than the Z was in stock trim. Straight line stripes are awesome. The car settles very nicely in the corners and I only get in trouble when I stand on the gas and give the wheel a little jerk, but that is usually on purpose to slide the rear around. In fairness the tire size surely changes everything, but that was one of the reasons for the swap. I can now buy off the rack 10.5" wide mustang rims and run 12" Z32 rear brakes. I have 335/35/17s in the rear but will swap to 315's when these are toast. Also, there is rear tow adjustment, and some camber adjustment built right in. No aftermarket arms required. However, there are fully ajustable arms available if desired. My car is nearly 10" wider than stock. My guess is that you could run 275's on all for corners if you wanted a really balanced handler without the big butt. Then again, I like big buts and I cannot lie! No matter what you do, you probably won't outperform a C6 with either setup. I am not sorry at all that I did the swap. I love the way the car behaves. I now have upgraded brakes diff, axles etc. and it was cheaper for me. Easier to find the parts too. Take it for what it is worth. Ed I wish you luck whatever you decide. I know what I would do.

[Ed260Z]

4)Why use the S14 over the S13 sub-frame?

**I think the S13 sub-frame will work just fine' date=' but you definitely want to use other arms. To quote myself-"S14, however, all of the arms are swappable except the lower control arms. For example, if you wanted to run the aluminum hub housing from a 300ZX (Z32), you could, but you would also have to have the lower control arms from the Z because the ball joints on the LCA are different................................

I would go S14, just so you have more options later." This means that if you use S13 lower arms, you cannot swap hubs with Q45 and Z32 unless you buy a different hub carrier from one of those cars and the corresponding lower control arm with it.................................

 

My car is nearly 10" wider than stock. ...........................I love the way the car behaves. I now have upgraded brakes diff, axles etc. and it was cheaper for me. Easier to find the parts too. Take it for what it is worth. Ed I wish you luck whatever you decide. I know what I would do.[/quote']

 

Thanks for chimeing in, your input is greatly appreciated. I am a bit bummed out that you can't use the S13 LCA with the Q45 or Z Carrier. I'm not looking to make as wide a Z as you have. At most I was looking at may be some ZG flares. I thought the the S13's arms would keep my wheels under the fenders W/O exssesive Back Spacing.

 

Are there any arms that will fit the S14 sub frame, and keep the width as close to 55" as possiable?

 

Or is it that the width of the sub frame is wider, and not the Arms?

[maichor]

All of the arms are the same length (infiniti and nissan.) The subframe is different in each car. It is not very hard to narrow the subfame, put the diff where you want it, centered or not to achieve what you want. If you go narrower than I did, you will have to cut more clearance for the front upper arms.

 

EDIT

P.S. Remember how wide my tires are. If you used my setup and ran 295's you would be 4" narrower than me and 275's would make you roughly 6" narrower. That should easily fit under ZG flares.

[Ed260Z]

All of the arms are the same length (infiniti and nissan.) The subframe is different in each car. It is not very hard to narrow the subfame' date=' put the diff where you want it, centered or not to achieve what you want. If you go narrower than I did, you will have to cut more clearance for the front upper arms.

[/quote']

 

I understand how to norrow the rear of the sub frame. But how do you narrow the front without killing the geometry of the suspension?

 

Do you need to section it at the front diff support?

 

Could I use the S13 sub frame, since it's already more narrow than the S14, with the Z32 arm LCA?

[87Kevin]

Well, why narrow the subframe? Just use the S13 subframe. I used it because it is exactly the right width for me. Not sure where maichor got his info from, but Z32 uprights bolt right to the s13 LCA and other links. That's how mine is setup. And I dont see any advantage of the s14/z32 arms over the S13, if anything the S13's stock RUCA is stronger because it goes around both sides of the shock vs the S14 which goes around one side.

Other than that, the arms are identical, and the designs of the cradles are all the same, with slight width and mounting location differences.

Especially since the A/M arms are so cheap, most will be upgraded anyways.

I did have to put a small notch in my unibody to make the forward mount fit, and as far as other mods, that's just too much to talk about, but lets say that I just ditched my high hp/no torque sr20 setup and am almost done my new vg33e/t setup.

[Ed260Z]

What do you need to do to mount the Z32 or Q45 LSD diff into the S13 Sub frame?

Is it as simple as just useing the 2 upper holes, and notching the bottom? Keep in mind that I want to keep the 2 bolt vented diff cover from those diffs.

[Hypertek]

just change the diff cover..

[Ed260Z]

If I change it to the S13 diff cover I lose the finned LSD cover. Or did the S13 have an LSD available for it?

[Hypertek]

s13s has finned rear diff cover. I know there is slight difference between 89-90 model and 91-94.. mine is a 92, only difference I recall is the oil fill hole is in a easyier to access location on the 89-90. Oh yah, my diff is a open differential housing, but I had installed a Nismo 2way clutch type lsd internals

 

I have a friend with a base model S14 (open diff), and I remember thier diff cover did not have fins, it was smooth. I cant recall if the SE model with vlsd had it.

 

Nissan offered a VLSD from the factory which has a different housing and different output/drive shafts, but thats going to be only in the SE hicas model subframe. But it will fit the standard subframe.

[twistex]

not to change subject but i was going to attempt a 240sx full suspension swap all the way around on my 240z. i was going to measure the width on the framrails from both cars to see if i could actually get a 240sx xmember to bolt it and place a rb motor in the car and modify my steeing shaft with u joints to get the 240sx power steering and everything to bre funtional. also wanted to do the 240sx rear subframe. well ok .. i know you could make a 240z have nice big brakes and all but i figured getting coilovers all the way around for 240sx suspension would be easier .. also 5 lug conversions. z32 brakes and so on. well anyone ever attempted the front suspension conversion ?

[RB26powered74zcar]

I was asked to chime in here so I will do the best I can. First of all' date=' my reasons for doing the swap are posted in my initial writeup here: http://forums.hybridz.org/showthrea...0&highlight=s14

 

Link no workie....

[karay240]

since there seems to be a little confusion over the Nissan multilinks, so here’s a quick breakdown.

 

S13: The most narrow one of them all. Which is why many Z owners consider it the choice for their swaps. You get decent traction w/ a lot of antisquat built-in w/ the front of the lower control arm tilted up. This makes for a stable feeling when accelerating, but in reality, you’re not getting the desired weight transfer (traction.) That’s one of the reasons why the S13 tends to break loose w/o much notice compared to the S14, and have limited traction out of the hole @ the strip. (this is true w/ the S13, R32, and Z32) . We’ve modified a subframe for an R32 we have here to eliminate this problem, and if you’re interested in similar things, you’re more than welcome to come & check it out.

 

R32: Everything from the S13 applies here, except the GTR subframe is substantially stiffer, and in theory, will handle better. But instead of the toe control arms it has HICAS, so you’ll need the HICAS eliminator bar for things to work properly.

 

S14: The theory of “newer = better†does apply here, in that Nissan took the good parts of the S13 subframe, and improved on it. Some of the differences are that they are a little wider, the upper control arm is more service friendly (anyone that’s changed the suspension on both of these cars know what I’m talking about. lol), addition of braces underneath the lower control arm, and the mounting points for the lower control arm are more parallel w/ the ground (less antisquat.) This lower control arm mounting has helped out w/ the traction issues of the previous model.

 

R33: Everything from the S14 applies here, except the GTR subframe is, again, substantially stiffer, and in theory, will handle better. But instead of the toe control arms it has HICAS, so you’ll need the HICAS eliminator bar for things to work properly. This improvement in traction is why you’ll notice that every S30 w/ a multilink setup has the R33.

 

S15: Pretty much it’s the same as the S14 subframe, but the lower control arms and the frame itself got more bracing. Stiffer = more traction. The subframe bushings (isolators) are different also, but not really applicable for this crowd. You’ll see several shop demo cars/drift cars from JP w/ this subframe on their S13/14. one final difference, though, is that the higher model S15 (turbo and other limited versions) came w/ a helical/torsen LSD instead of the VLSD like the previous S chassis cars.

 

R34: blah blah, stiffer than the s15, blah blah, HICAS, blah blah.

 

Z32: Wider than any of the above, but very similar to the S13, R32, and the G50. Many might suggest to go w/ this subframe for high HP cars due to the bigger R230 diff. It’s true that the TT model has a bigger R230 diff (non-turbo version has an R200); however, the stub axles are pieces of crap, and tend to break. Even high HP Z32 like the Escort Z has the GTR R200 diff. Another advantage to the R200 diff has more gearing options than any other Japanese cars.

 

Mazda Double Wishbone setups: since some of you guys were talking about the Mazda double wishbone setup (miata or FD.) Unfortunately, Mazda uses a PPF (power plant frame) that connects the tranny to the front of the diff. You would need to figure out a way to allocate a mounting point for the front of the diff. Besides, the differentials on those things are crap. They may survive high HP, but not high torque.

 

Other setups: I’m tired of typing, so you’re on you’re on your own.

[260DET]

Toyota double wishbone?

[karay240]

yes, supra.

[260DET]

Supra is good? Cressida and other similar sedans?

[karay240]

I'm talking about the JZA80 ('93~). We're mainly a nissan shop, so I'm not an expert in toyotas. what i do know; however, is that the older supras (jza70) had a double wishbone setup, but that's what the design is--old. the newer models (jza80) utilizes a newer design w/ cast aluminum pieces, and will allow for the HUGE 13inch rotors.

[Ed260Z]

Link no workie....

 

The link was in my first post. http://forums.hybridz.org/showthread.php?t=96050

 

He did a good write up on his swap.

 

I see that this post has turned into a IRS suggestion box for some reason. But many have said that the S13/S14 IRS is a compromise, of ride comfort and performance, so are these others. And I would assume that the level of fabrication required to make these other systems work maybe more inlvolved that the Nissan. True a Double Wishbone IRS would be ideal, but this was not indended to be a suggestion box. I wanted to discuss the merrits, and drawbacks of doing this type of swap.

 

Since I'm about a year or so away before I start to actually modify my IRS I could allways open up another thread on doing a Toyota, Corvette, Mazda, Jag, ect...................... The possiabilities are almost endless, with enogh imagination.

 

With that said I realy appreciate everyones comments and suggestions, but can we keep it on the subject.

 

Thanks,

Ed:twisted:

[karay240]

But many have said that the S13/S14 IRS is a compromise, of ride comfort and performance, so are these others.

 

what do you mean by this? the main reason for multilink/doublewishbone is to get the best of both worlds. w/ the conventional strut design, you need to run stiffer suspension to maintain the ideal alignment in a turn. the problem w/ this is that if you make the handling too stiff, then you run into problems like bouncing around and not getting any traction around bumpy surfaces. The goal of these complicated designs are to allow the contact patch to be ideal throughout the travel, thus being able to run softer suspension that is more compliant on rough surfaces (less spinning out on rough track surfaces).

 

the only compromise these complicated suspension geometries have are cost and weight.

 

if your Z is going to be a strictly a track car, i don't really see IRS having that big of an advantage, since weight is a big key of getting good times.

 

 

advantages:

-better ride quality

-less hopping over imperfections of the road

-relatively inexpensive bigger brakes

-better diff/axles

-requires less static camber (longer tire life)

-and of course, it's pretty sexy

 

disadvantages:

-cost

-weight

-finding a shock/spring setup that will work

-major problems if not done right

 

 

I think that about sums it up.

[johnc]

A simple question:

 

Does anyone know where the roll and instant centers are on the 240SX rear suspension?

 

A simple suggestion:

 

Until these two items are known, I would wait to do the swap.