Critique this setup pls!

[Guest macks]

Howdy, I'm doing the research on a suspension setup for my car, and after getting some quotes I'm keen to get your opinions on it...

 

Front bumpsteer mod yet to be done (3/4" up, or 3/4" up and 3/4" out?)

 

Front:

Struts (yet to be) sectioned 23mm (slightly more than 15/16th of an inch)

300zx Koni Sport adjustable shocks

175lbs/inch 2.5"ID Eibach race springs on coilovers

 

Rear:

Struts (already) sectioned 37.5mm (1.5")

300zx Koni Sport adjustable shocks

225lbs/inch 2.5"ID Eibach race springs on coilovers

 

Bushings:

SuperPro polyurethane front lower control arm inner bushing kit

SuperPro polyurethane steering coupling

SuperPro polyurethane strut bar to chassis mount kit

SuperPro polyurethane diff to cross-member to chassis bush kit

Noltec rear lower control arm inner bush w/ toe adjustment

 

the only real query I have is whether the 23mm sectioning will be enough at the front - as the rear has had a 1.5" section. Will 23mm give enough bump travel? If not, I have to look at using different shocks which mean I can take up to 1.5" out of it, but these shocks will likely need revalving, which is an expense I'd like to avoid if its not necessary

 

Cheers!

[74_5.0L_Z]

So far your list looks pretty good.

 

The bump steer mod is 3/4" up, and 1/4" out(no more). If you go out too far out, then the sway bar ends will be misaligned with the hole in the lower control arm, and will cause binding. I modified mine as above, and love it. Bump steer has been virtually eliminated.

 

As far as the 300ZX struts, I don't know. Are they the same diameter/configuration. Most people here are using MR2 strut inserts in their sectioned front strut housings, and 240Z fron inserts in the rear. Ground Control sells Konis that are the correct length for sectioned struts.

 

Your spring rate selection looks good. I am using 250# rear and 200# front.

 

What are you using for sway bars? If you have a posi rear, then use a small rear bar. If you don't have a posi rear, then use no rear sway bar. A rear sway bar will cause oversteer, and reduce traction off corners.

[Guest macks]

The bump steer mod is 3/4" up, and 1/4" out(no more). If you go out too far out, then the sway bar ends will be misaligned with the hole in the lower control arm, and will cause binding. I modified mine as above, and love it. Bump steer has been virtually eliminated.

Cheers for that, I'll do the same

 

As far as the 300ZX struts, I don't know. Are they the same diameter/configuration. Most people here are using MR2 strut inserts in their sectioned front strut housings, and 240Z fron inserts in the rear. Ground Control sells Konis that are the correct length for sectioned struts.

Yeah, that's what I requested from all the shops I got quotes from. I was actually after tokiko illumina 5-ways, but in aus they're not readily available. Most shops put together quotes around the mr2 and 240z setups, but koni adjustables aren't available for 240z fronts any more

 

One shop suggested using 300zx inserts, as they're 23mm shorter in the front, and 40mm shorter in the rear, are in the right ballpark for valving, and are readily available. The only real drama I'm worried about having is whether a 23mm section in the front leaves enough bump travel - can anyone comment? The next shortest strut goes to 40-something mm shorter, from a holden calibra, but the valving will likely be wrong.

 

Your spring rate selection looks good. I am using 250# rear and 200# front.

How's the ride? I'm wary of the rumoured kidney injuries, but I haven't been in any zeds with uprated springs... what are the stock rates, anyhow?

 

What are you using for sway bars? If you have a posi rear, then use a small rear bar. If you don't have a posi rear, then use no rear sway bar. A rear sway bar will cause oversteer, and reduce traction off corners.

"posi rear" = ?

I'm assuming limited slip diff..?

Don't have one ... yet, but it's definately on the cards. Swaybars at the moment are the stock (260Z 2-seater) bars, I haven't looked into them yet... any suggestions?

 

cheers for your help!

[260DET]

Koni Sports are a good choice. Length would depend on your proposed ride height but perhaps a rule of thumb would be to use shocks shorter by the same amount as the ride height will be reduced.

 

King springs are good and come in a big range. May be cheaper than Eicbachs.

 

Agree that no rear sway bar with a big front bar is the way to go, particularly if you are going for more power.

 

Spring rates depend on what you are going to do and how much suspension travel you end up with. For my road/track car I use 250 fronts, 300 rears which gives a firm ride but not excessively so imho.

[evildky]

not the 300zx rears, the 300 zx uses shocks and not struts in the rear so that will not work, unless you plan on using 4 front strut inserts, just thought you might want to know before you order a pair of rear 300zx "struts" and can't figure why they sent you a pair of shocks that will not work

[Guest macks]

yep, should have added that, i'll be using 4x the same 300zx front shock all the way around

 

the spring rate issue is still up in the air. I'd really like a cheaper alternative to eibach springs, because at $A300 a pair it's going to be expensive to fiddle with the setup I'll see if I can find some king springs in Perth...

 

re: big front swaybar - can1 this only be bought aftermarket, or substituted from another model? (eg 2+2)

 

the 300zx shock setup with coilovers and sectioning was used on the 240Z that was in the london->sydney rally, set up by the same guy who suggested it for me.

 

What's the story with front camber/castor adjustability? Other non-zed people are looking at the setup and are wondering if it'll be an issue.

[Mudge]

Originally posted by macks:

yep, should have added that, i'll be using 4x the same 300zx front shock all the way around

Front STRUTS correct? I also see different part numbers for the 300ZX fronts, so I'm assuming this is a left/right thing, can you list the part numbers your using?

 

Since these are for a much heavier car, I am assuming/hoping that they will handle aggressive springs without issue

[260DET]

My last pair of linear type King springs cost around A$180 (US$95), progressives are more but imho are not required.

 

Whiteline for one make custom sway bars, my front is 28mm dia, but adjustable. You can get aftermarket brackets and poly bushes to suit. Super Pro brand? But you will have to make heavier mounts to suit the new bracket holes spacing. Stock mounts are weak anyway.

[Guest Anonymous]

On your bumpsteer modification "only add 1/4 inch out if you want to add MORE Negative Camber" Before we run this thread ad infintium what in the**** kind of Z are we talking about a 300 Zx or a morfidite early Z of unknown pedigree. Your rear strut tubes are already sectioned 1 1/2 inches to accept 300 ZX struts (?) which will automatically give you a 3 1/2 inch lowered rear.Your early stock early Z will not accept a shock absorber in their strut tubes..(but I have heard you aussies can cut VW motors in half and mate them to Russian motorcycles to run them coast to coast in the states). There is a big differences in 240 and 280 suspensions when it come to sectioning strut tubes and adding coilovers and cartridges. The 280 strut tubes are bigger in diameter and longer 2.185 diameter for a 280 as opposed to a 2.02 / 240 Z diameter.The front strut cartridges are shorter in all models than the rear strut cartridges by about 2 inches. We usually place the front z strut cartridges in the rear strut tubes and a BZ3099 Tokico adjustable Illumina from a MR2 in a sectioned 240 Z front or a KYB GR2 364014 VW Rabbit in a 2 inch sectioned 280 Z front strut tube. I assume you will have coil overs and adjusting sleeves and nuts. You can only section the front strut tubes as much as the length of the strut cartridge that you select will allow and get the strut tube gland nut threaded back on the strut tube.You can safely section a strut tube 2 inches and replace with a shorter strut cartridge Get the strut cartridges before any sectioning of the strut tubes. You could possibly adjust your ride height with the adusting nut to compensate for the difference in front and rear height but it would be more reasonable to equalize the sectioning in the front to match the rear.

[Guest macks]

oookay, time for a little clarification

 

the car is a 260Z 2-seater, and I'm converting to coilovers, sectioning all the struts and using shorter shock inserts all around.

 

the 300zx damper I'm referring to is the *front shock insert* for the 300zx, which is shorter than the stock 260Z insert by 23mm in the front, and 40mm in the back. I haven't made these measurements personally, they were provided by the suspension bloke who set up a road rally 240z with this gear - using the same *300zx front strut insert* in the front and rear for the 240z.

 

I've sectioned the rear struts of my car 1.5", which is fine because the 300zx front insert is 40mm shorter than the stock rear insert. I'll use a spacer to make up the difference.

 

I haven't sectioned the front struts yet, however if I reduce their length by 23mm, the 300zx front insert will fit and will have appropriate damping. Height issues can be solved by mounting the threaded coilover sleeve in the right spot - I'm not limited to using the old spring perch weld bead, because I'm welding on a new perch.

 

However, I'm wondering if the fronts need more length taken out to allow enough bump travel, given that I'm going to be lowering the car more than 23mm in the front. Some have suggested sectioning amount = desired ride height reduction. However, this necessitates the use of a shorter shock insert - found in the holden calibra. The difference is that this insert is valved too hard, and would need to be revalved, incurring an additional expense. Only sectioning the struts 23mm will mean I don't have this expense, but will 23mm be enough..?

 

cheers

[Guest Anonymous]

As I said before the coilovers without any sectioning will give you an automatic 2 inches lower. Be sure to use some polyurethane bump stops on the struts. You should not have much problems with your set up. Just section for a precise front fit with the 300 ZX strut cartridges. On 10 inch coilovers you will want to stay in the same area as the original spring perch weld bead but with 12 inch coilovers you could go lower than the original bead .For Example: In other words on 10 inch coilovers with a 2 inch section you would cut out an inch on each side of the weld bead. On 12 inch coilovers you could cut out the 2 inch section below the Original weld bead. Without any wheel clearance problems you may want to go to the 12 inch coilovers in the front and possibly bump your front spring weight up to 185 pounds for the 10 or 12 inch coilovers to prevent bottoming out.

[260DET]

If you want adjustable camber on the front, consider using weld in eccentric adjusters, particularly if you are going to relocate the pivot points anyway. Fortuna make such adjusters specifically for your car, they weld into the Xmember, cost around A$80 pair.

 

On suspension travel as dictated by the length of the strut inserts, your proposed setup sound OK to me, although once again it depends on proposed use. I guess if the inserts are too short you may end up with insufficient droop, causing the inserts to top out when the wheel drops into a hole, etc. Loss of some bump travel can be compensated for by using firmer springs, which you apparently intend to do.

[Guest macks]

Originally posted by 260DET:

If you want adjustable camber on the front, consider using weld in eccentric adjusters, particularly if you are going to relocate the pivot points anyway. Fortuna make such adjusters specifically for your car, they weld into the Xmember, cost around A$80 pair.

I tried looking for these in a google search, but no luck - have you got any info/websites/suppliers..?

 

Cheers!

[TimZ]

On the subject of how much to section the struts - you are leaving out the one essential piece of information. How much are you lowering the car? Until you supply that piece of information, you can pretty much disregard any suggestions that you have received so far.

 

Also, as has already been mentioned, depending on which suspension pieces you are using, adding camber plates alone can drop your ride height by as much as 2", without sectioning the struts, or losing bump travel.

 

There is no exact amount to tell you to section your struts by. You want to end up with the strut being as close to the middle of its travel as possible at your static ride height. This is the only thing you should be worrying about.

 

My best advice to you would be to assemble your suspension (before sectioning) without the springs, and use a jack to bring the suspension to the middle of it's travel. From there, you should be able to see how much you still need to lower each end (you might be fine as it is, BTW). If you still want it lower, then you need to section the strut by the amount that you want to lower it by. Bear in mind that you will still be limited by the length of the insert that you plan to use.

 

On the bump steer issue (I cringe every time this comes up, BTW), I've said this several times before and it never seems to sink in: the "bump steer mod" as outlined in JTR almost certainly will not "fix" your bump steer characteristics. It will definitley change it, but it won't necessarily make it better. If you've ever tried to actually dial out bump steer, you'd realize that this is a much finer adjustment than could ever be covered by a rule of thumb, such as "up 3/4", out 1/4", or not".

 

The mod is still worthwhile, because it yields a better camber gain characteristic, but don't expect it to zero out your bump steer.

 

If you really want to get rid of bump steer, you will need to slot the mounting holes, and move the pickup point around until you get the right characteristic, then weld the washers in place. To measure this, you will need to (again) assemble the suspension without the springs, move the suspension through it's travel, and graph the change in toe-in, say, every half inch or so. It's pretty tedious, but not rocket science.

 

Finally, the eccentric bushings for adjusting camber will blow any bump steer adjustment that you have done out of the water. Better to change camber at the top of the strut, where it has a minimal effect on bump steer.

[Modern Motorsports Ltd]

I was actually after tokiko illumina 5-ways, but in aus they're not readily available.

Too bad, a friends niece is flying back to Oz today and I have a set of 240 Illumina's on the shelf..oh well!

[260DET]

Fortuna Engineering Works P/L, 859 Beaudesert Road, Coopers Plains, Q. Phone 3277 5699.

[Guest macks]

Originally posted by TimZ:

On the subject of how much to section the struts - you are leaving out the one essential piece of information. How much are you lowering the car? Until you supply that piece of information, you can pretty much disregard any suggestions that you have received so far.

Good point The car is going to be lowered between 1.5"-2" depending on what I can do about ground clearance. I completely understand the importance of the shock being in the middle of its travel in loaded configuration, and not topping or bottoming out. In this regard, through doing eleventy billion searches I'm led to believe that struts have been sectioned 2" and still retained more than enough shock travel. My rear struts have only been sectioned 1.5," and using the 300zx front shock in the rear maximises the travel available, given a 1.5"-2" lowering. In any case, higher spring rates reduce the travel in use

 

Also, as has already been mentioned, depending on which suspension pieces you are using, adding camber plates alone can drop your ride height by as much as 2", without sectioning the struts, or losing bump travel.

This is true, however my car has been a farmer's weekend driver for 3 years, after sitting in a barn for 5 - the suspension is all but shot and nobody's thought to do anything about it

 

On the bump steer issue (I cringe every time this comes up, BTW), I've said this several times before and it never seems to sink in: the "bump steer mod" as outlined in JTR almost certainly will not "fix" your bump steer characteristics. It will definitley change it, but it won't necessarily make it better. If you've ever tried to actually dial out bump steer, you'd realize that this is a much finer adjustment than could ever be covered by a rule of thumb, such as "up 3/4", out 1/4", or not".

 

The mod is still worthwhile, because it yields a better camber gain characteristic, but don't expect it to zero out your bump steer.

 

If you really want to get rid of bump steer, you will need to slot the mounting holes, and move the pickup point around until you get the right characteristic, then weld the washers in place. To measure this, you will need to (again) assemble the suspension without the springs, move the suspension through it's travel, and graph the change in toe-in, say, every half inch or so. It's pretty tedious, but not rocket science.

 

Finally, the eccentric bushings for adjusting camber will blow any bump steer adjustment that you have done out of the water. Better to change camber at the top of the strut, where it has a minimal effect on bump steer.

Good advice, I'm keen on trying this.. What toe-in change characteristics (and thus what resulting graph) are ideal for minimal bump steer? (common sense suggests minimal change through desired range of motion, but i'm just guessing )

[Guest macks]

Originally posted by 260DET:

Fortuna Engineering Works P/L, 859 Beaudesert Road, Coopers Plains, Q. Phone 3277 5699.

thankyou

[TimZ]

Originally posted by macks:

The car is going to be lowered between 1.5"-2" depending on what I can do about ground clearance. I completely understand the importance of the shock being in the middle of its travel in loaded configuration, and not topping or bottoming out. In this regard, through doing eleventy billion searches I'm led to believe that struts have been sectioned 2" and still retained more than enough shock travel. My rear struts have only been sectioned 1.5," and using the 300zx front shock in the rear maximises the travel available, given a 1.5"-2" lowering. In any case, higher spring rates reduce the travel in use

Yes, I do know of struts being sectioned that much and still having enough travel. However, these were most likely on applications where the car was lowered about 2", so the 2" section made sense. Just remember that sectioning the strut does not add or subtract the amount of travel available (assuming you didn't have to change to another strut with more or less travel) - it merely changes the ride height at which you are in the middle of the available travel.

 

For instance, if you are only going to lower the car 1", it doesn't make sense to section the strut 2". You will gain bump travel, but you will lose rebound travel, which can result in literally pulling the wheel off the ground when the shock tops out. Do your best to keep the suspension withing 0.5" of the middle at your static ride height.

 

Stiffer springs will limit the travel as well. If you are lowering more than 2", you probably would want stiffer springs, just to keep from bottoming the chassis out. In this case, however, you won't need as much bump travel, either. For the street, I think the spring rates that you have chosen will work very well. I wouldn't go much stiffer, unless this is a track only car, or unless the streets in Australia are much smoother than they are here in the states.

 

What toe-in change characteristics (and thus what resulting graph) are ideal for minimal bump steer? (common sense suggests minimal change through desired range of motion, but i'm just guessing )

Yes, that's right - I would just shoot for minimizing the change in toe through the suspension's travel. You might be shocked when you see what the characteristic looks like before you change it - my car had over 1" of toe change (this was measured at one wheel only, so double that for a traditional toe measurement )

 

I origninally tried using the 'bump steer spacers', (very similar in principle to the JTR mod, BTW) and found that these actually made the problem WORSE.

 

That said, it should be possible to come up with a bump steer curve that is very near zero. It sounds like you are clear on how to measure this - if not, let me know, and I'll explain it.

[pparaska]

Tim, glad to hear someone else say the bumpsteer spacers don't help with bumpsteer. I've been saying that for years!

 

I'd love to get comments on how to make a cheap but good bumpsteer gage. I have one dial indicator, and was thinking about using some plywood, some tight hinges (piano hinge), a weight to hold it steady, and have the dial indicator hit the rim edge at spindle height infront of the spinde, and a bolt through the vertical plywood piece hit the rim behind the spindle at the same height. Saw this somewhere. Any comments appreciated.