Can These Coilovers Be Damper-Adjusted/softened? Pics Supplied

[rondofj]

Hi Guys,

Please see pics - first one is of front coilover tops, last two are of rear right wheel coilovers, R34GT-T.

Coilovers = Cusco older model something Japanese yada yada

Problem = Too bloody stiff / no traction for a 290rwkw car / can these be softened? Rears ONLY.

I can rotate the coilover tops with an allen key or spanner and it rotates in the casing which is stationary. Is this the damper settings and is anti-clockwise = soft?? And clockwise = hard. Theres no marks whatsoever.

Or should I change to softer springs? Im not sure but it looks like its got two springs per coilover, not sure how this works. I'm intending to lower the rears a bit as well to match the front and soften it up as much as possible.

Please fire suggestions if you can - thanks Ron

[GTSBoy]

It is quite likely that the hex socket is the adjuster, and it is quite likely that anti-clockwise is "soft".

Having said that....the adjustment is quite possibly ONLY on the rebound damping. What this would mean is that you would want to wind the rear ones to fully "stiff" and leave the front ones softer. This may sound crazy, but I have reason for saying so.

If the springs are very stiff (and they probably are) then there's a few problems with backing off rebound damping at the rear. These are that if the bump damping is fixed then as you launch the rear suspension will squat at a rate determined by the springs and the bump damping. If you have softened up rebound damping then the springs are free to try to push the car body back up (because there is little damping to resist the rebound force). The result is poor traction. If you soften off the rebound damping then the suspension will squat down more effectively.

Conversely, you kind of want the front to lift, so you have to leave that softer (on rebound).

The trouble with all that is that then you will have dampnig set up for traction and not at all for balanced grip in corners. You would probably introduce some nasty understeer. I would prefer balanced grip in corners.

Now, we talk about your "second springs". These are called helper springs or tender springs. They short but very low rate springs that are added on top of the short and very stiff coils on coilovers when there is a danger that the main spring will not be held captive under suspension droop conditions. This is usually only necessary when the main coils are short and very stiff. Note the "very stiff" part.

So here's the rub. You probably have rather stiff springs. When you have stiff springs you need to have very strong damping, both in bump and rebound. If you don't then you get a nasty jiggly uncontrolled ride. You cannot have your cake and eat it too. But stiff springs are the root cause of no launch traction, not stiff damping. You probably need to look into getting less stiff springs. If you do, then a) you need to find out what rate springs you have now before choosing a new rate, and b) you need to find out if the dampers you have will work with the (probably) somewhat softer springs that you will want. Or, failing that, you need to find out if they can be opened up and revalved (unlikely).

There is one last thing......it is possible that the dampers adjust both bump and rebound at the same time when you turn the adjuster. Typical KYB adjustable dampers are like this (and typical Koni adjustables only offer adjustment on rebound). If they do adjust both bump and rebound at the same time then my advice at the top of the post needs some alteration. What you would do is back off both front and rear a bit, to try to keep balance but also to allow both the rear to squat and the front to rise. But I wouldn't expect it to gain you a lot. As I said, the springs control the real stiffness.

[rondofj]

Thanks mate for the really thorough explanation. I don't launch my car, at the moment its a 100% streeter, where I have trouble is rolling bursts in 1st and 2nd gear and to an extent third as well, coming suddenly onto full boost at 3800-4000 it starts spinning n skating, first gear takeoffs are virtually useless even when not launching hard but going from a slow roll. Foot control being reasonable.

Now I did read on the net that the Cusco Zero 1 and Comp S coilovers dont have damper adjust, mine is either of the two or an older one but definitely not the newer Zero 2 or 3 which do have this feature. I read the allen key is to hold the thread while you undo and redo the centre nut, not for adjustment of damping. But I can turn the shock body with either without jacking up the car- reasonable force required though.

So the stiff springs are the problem, I am goin to try to measure them today with the wheels off and try to get a spring rate based on SydKid's thread. What I dont know is how to work out how much softer springs my dampers will take- ie 1-2 kgs down?

[GTSBoy]

You might be able to get away with 1-2 kg. I would definitely prefer overdamped suspension than underdamped. Worst case you blow some money on some springs, then you can try to sell them on to minimise your expense.

[rondofj]

Well I put the rear up on jackstands and took some pics - see attached. Stupid me forgot to measure spring sizes and work out a rate (SydKid), but at least I can sort of figure out 'which' Cuscos they might be. Went to ebay US to have a look, they could be similar to these:

http://www.ebay.com/itm/JDM-93-98-Nissan-Skyline-R33-GTS-RB25-Turbo-CUSCO-Racing-Coilovers-Springs-/200840029302?pt=Motors_Car_Truck_Parts_Accessories&hash=item2ec2ffa476&vxp=mtr

http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313&_nkw=cusco+coilover&_sacat=0&_from=R40

Most of these Cuscos don't have the 'helper' springs, dont know why mine does. I can squeeze these helpers a wee bit with my hand but the main coil is too hard to compress by hand, I can only just about move the whole assembly up manually and my guess is I'm only compressing the helpers not the main coils which suck.

I lowered the rear 25mm or 1 inch by releasing the lower lock nut and winding the coilover body down by hand, using a measuring tape to keep it in check both sides. No difference to stiffness (thought it would go stiffer but realize thats only if I change the spring preload which I didnt). Good thing, is the car looks a lot better with this stance, just hope that my camber hasnt gone in so much that it will wear out my inner tyre treads.

Now those main springs, do they look familiar to you, any guesses onto their rating? I want to change them and get rid of the helpers, this ok?

thanks for the help mate

[GTSBoy]

Not possible to guess the spring rates. Small changes in wire diameter have big effects on rate. But they do look pretty stiff. Thick wire, not many active coils. There was a thread from a US forum where a guy had some BC coilovers with 12/10 rates and yours don't look a lot different to his springs. But again - do not take that to mean yours are that stiff - simply too hard to compare. But I woul dnot be surprised if yours are at least 8/6, which I consider to be too stiff. Stock Skyline springs are about half that, or less.

[rondofj]

Okies thanks man, I think I will jack it up again, wheel off then measure the coil wire width and length, no. of coils etc. I assume the I dont need to measure the 'helper' coils? The net pulls up various spring rates of Cuscos, generally the fronts being in the vicinity of 8-10kg and the rears 6-8kgs..

[GTSBoy]

You really need to be able to measure the free length of the main springs. (You're right, ignore the helper springs' contribution). If those helper springs are expanded, then in theory there's very little force applied to the main springs and you should be able to consider the length you measure as being the "free length". Or close enough that it won't make any difference anyway.

if you're 8/6 or 10/8 (especially 10/8) then you're in the fairly bloody stiff range.....6/4 would be more comfortable and should offer better hookup.

[djr81]

The adjuster doesnt adjust anything. It is there to allow you to hold the shaft of the shock stationary while you do up the nyloc nut that holds it to the top plate.

[rondofj]

Thanks guys havent had a chance to pull it apart to measure spring sizes yet due to work constraints but will be putting it up soon..Those springs are really rock hard...

[rondofj]

Hey guys, managed to get a few numbers up which I posted on Sydneykid's pinned thread on spring rates - hope to get a reply soon:

Spring outer dia : about 90mm

Spring coil dia: 15mm

No. of coils: about 7.8? (the bottom of the last coil is sort of a 'split half diameter coil' - see pic)

Please disregard the lower 'helper springs'.

Thanks Ron

[GTSBoy]

There are online spring calcs you can use. I wouldn't be expecting a reply in SK's thread....he hasn't been active lately, has he?

Oh, and you need the free length.

[rondofj]

Free length is about 205mm, will see if I can find anything online- I expect these springs to be bloody hard- maybe 8kg/mm? You did say I can go a couple kgs down for my shocks to cope with?

[rondofj]

Online calcs came to around 15.2-15.6kg/mm from two sources- thats impossibly hard lol

[rondofj]

8 coils, 90mm OD, and 14mm wire dia gets me about 11kg/mm just going down a mm in wire thickness, sounds more realistic..

[rondofj]

I measured with a tape measure in-car not venier calipers so bound for errors give n take 1-3mm

[GTSBoy]

Don't waste your time without verniers.

11 sounds ball park correct. These are the front ones yes? The rears would probably come out at about 8 then.

Horrible. Simply horrible. Track spec only. If you got springs a bit softer, they'd still be too hard for the street. Migth feel better enough for you to be happy though. Worth the investment? Or sell these to a track fiend and buy some BCs to replace them?

[rondofj]

Hey there these are rears, so even more horrible lol,- you can add a couple KGs on the front ones.. Ima be off to super cheap to get some verniers soon, and Im intending to just change the rears for grip, maybe a pair of rear BCs is what I need as a final reaort..

[rondofj]

The helper springs are helping absorb the shocks, if they werent there, then these springs are impossible to compress by hand

[GTSBoy]

No, when the vehicle is on the road, the helper springs should be squashed to binding.

I wouldn't put softer coilovers on teh rear only. If your fronts are like 12 or 13 kg/mm, then the BC rears at (say) 8kg/mm will be too soft (by comparison) and the car will understeer like a bitch. You might make it work if you pulled the front ARB off it and ran a fairly thick (like 22 or 24mm) rear bar.