Soft Or Hard Springs, Tech Heads Plz Read

[ELI]

hi,

first off i know nothing about suspension. im looking to get some coil overs. i found some that i think are alright but just wondering if these spring rates will be to stiff. are 10kg front and 8kg rear springs considered stiff or comfortable. if you can give me an answer based on personal experience that would be great. also if any tech heads are reading this would you be able to explain to me a little bit about the relationship between spring rates and ride quality, stiffness etc. i really would like to learn a lil bit more bout this kind of thing.

any help you can give will be great

thanks so much, Elli

[Busky2k]

Basically the higher the number, the stiffer it is. 8/6 will be fairly stiff and the stock springs are probably less than 1/3rd of those values. However the valving in the shocks will also determine the ride quality too which people tend to forget. Put a rock hard shock with a soft spring and it'll still break bones. And remember stiff does not mean you got a good handling ride.

[n15m0]

Correct me if I'm wrong but I've read from one of SK's threads that factory suspension spring rates are around the 3k mark for Skylines. I've got Tein Super Streets which are 5k front and 4k rears. They are definately firmer than stock but still comfortable. 10k/8k I would assume be very much stiffer compared to stock suspension. You would feel every pebble on the road.

[salad]

Stock rates are something like 125lb/in (2.2kg/mm) in the front of R32 gts-t. 10/8 is very stiff, you will lose compliance, so handling will be sacrificed and you will lose comfort. It's lose lose, so dont bother

[YLD-180]

i got 8/6 spring rate with my ISC's and i think they're perfect for the street and sliding, pretty sure they'll work great on track but ill find that out in a couple of weeks

[Hardman69]

I've got HKS Hiper D' Coilovers, and I THINK they're 9 or 10kg front, 6 or 7kg rear.

They're WAY too stiff to be comfortable, or even practical on the street! They're not oven helpful on the track - at Winton I was running the shocks at 2 or 3 clicks on the front, 5 clicks on the rear (out of 12), on the street it's 1 click front, 2 clicks rear.

I'm ditching the spherical-bearing shock mounts, putting conventional rubber-bushed mounts on the strut-tops soon, to try and get SOME small-bump compliance.

[RellikZephyr]

my suspension is 12kg front and 9kg rear and they are WAY too stiff

no comfort level at all

and lose out in handling because they soo stiff the car "bounces" round corners NOT COOL

am changing to Tein Super Streets soon 5kg front 4kg rear

i wouldnt go for that setup personally, unless its a dedicated track/drift car (even then you prob be better with 8/6)

RellikZephyr

[Mr. Keets]

10/8 would be hard work, even 8 and 6 ...but thats for sliding so its a different trip. I agree with Rellik, 5 and 4 Kg/mm springs are the go will still give you a firm ride, good for the odd track day but youd still be able to drive it on the street without pain. In the end you need to be honest and really look at what your going to do with the car. I bought the GB stuff from SK with some harder srpings and adjustable rear arms and it transformed my R.

[Beer Baron]

I'm running 10/8 on my GTR, but I have the dampers (good ones) to control such a stupidly stiff spring. my GTR I only drive at the most 100km a week so it's not a concern for me, but if I drove it every day that set-up would get old fast. I would say unless you have some fancy pants mono-tube dampers with remote canisters and seperate bump and rebound adjustment then you are just asking for trouble with springs that hard, especially if you do a lot of street driving. in fact if you drive it more than 3 times a week I wouldn't consider anything harder than about 6/4 or 7/5.

actually I just realised you have a GTST not a GTR. in that case you could go a little softer even. 10/8 springs will give a poor ride and on the whole poor handling too.

[tjandriesen]

It is interesting to note that Nismo, who we might agree knows something about Skylines, has spring rates of 6.0(f) & 6.7® on their S-Tune (sport) suspension and 9.0(f) and 8.0® on their R-Tune (Race) suspension.

'http://translate.google.com/translate?u=http%3A%2F%2Fwww.nismo.co.jp%2Fproducts%2Fproductguide%2Fbcnr33%2Fpartslist.html&langpair=ja%7Cen&hl=en&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools

[Mr. Keets]

I'm pretty sure BB runs R tune Ohlins which are nice ("fancy pants mono-tube dampers with remote canisters and seperate bump and rebound adjustment "). But BB does alot more track work than mine whereas my R is primarily a street car. I would probably go to 6kg/mm fronts as a max on roads around Perth. For other places it might be different but changes in surface heights and quality on our roads would make driving really uncomfortable... not to mention pot holes and traffic calming devices. Also Japanese roads are alledgedly alot smoother so the effect of stiffer springs is less pronounced and therefore acceptable. The Japanese, from what I've read, tend to control body roll more often with stiffer springs rather than stabilser/sway bars like Austarlians do. Horses for courses

[Beer Baron]

I'm pretty sure BB runs R tune Ohlins which are nice. But BB does alot more track work than mine whereas my R is primarily a street car. I would probably go to 6kg/mm fronts as a max on roads around Perth. For other places it might be different but changes in surface heights and quality on our roads would make driving really uncomfortable... not to mention pot holes and traffic calming devices. Also Japanese roads are alledgedly alot smoother so the effect of stiffer springs is less pronounced and therefore acceptable. The Japanese, from what I've read, tend to control body roll more often with stiffer springs rather than stabilser/sway bars like Austarlians do. Horses for courses

yes, I have the nismo R-tune Ohlins. lol don't know about more track work, but definately less street so I guess the ratio of track - street is higher! I agree 6kg fronts is plenty stiff enough for a road GTR, and I think would even be too stiff for a road GTST.

I've been in a mates 34 GTR in japan with 12kg front and 10 or 11kg rear and even though their roads are mostly smoother there are still lots of crap ones too. it was very, very hard!

[tjandriesen]

The Japanese, from what I've read, tend to control body roll more often with stiffer springs rather than stabilser/sway bars like Austarlians do. Horses for courses

Not to sidetrack this thread, but what kind of stabilizer do most people run? From looking around at the part sites there seems to be 3 choices - whiteline, cusco, and nismo. I think your point above is there is more than one element to a good performing suspension and you need to have synergy among the components, so less stiff spring can be offset by stronger bars.

[scathing]

10/8 is very stiff for a GTS-t, but with the right spring rates you'll be OK.

My Z33 runs 12/12, but since they came in a coilover kit the ride is actually quite good. I get quite a few compliments from people who say my coilovers ride remarkably well on the road.

What sized rims are you running? Bear in mind that the job of the suspension is to control the movement of the wheel, so the weight of the wheel you're running is also a consideration when it comes to optimal spring rates.

I'm running 17" rims at the moment, and I found it a little bumpier than stock (but well within the bounds of acceptability for my intended purpose). But when I borrowed a mate's 18" rims with semi slicks, the ride actually smoothed out over corrugations contrary to the accepted rule that bigger rims and ultra-stiff R-Comp sidewalls decrease ride comfort.

I remember reading somewhere that you can have wheels to big and heavy for your suspension, since your springs and dampers weren't engineered for that much unsprung weight and so its too slow to react. By the same token, having too little unsprung weight means your suspension will react too quickly as there's less inertia from the wheel, and your car ends up feeling oversprung and underdamped.

Which is why my current rims are for sale, pending my 18's arriving.

Its possible that 10/8 will be passable on 18-19" rims, as long as the dampers are well matched. I'm no suspension expert though, so this is all hearsay and personal experience.

Edited February 19, 2007 by scathing

[Sydneykid]

The spring's job is to hold the car up and absorb suspension movements to keep the tyres in contact with the road surface. The shock absorber’s job is to control the spring and the chassis (both the sprung and unsprung portions of the chassis). So the shocks control the movement of wheels and tyres. Keep in mind that tyres themselves are springs and they have no damper to control them.

Just like any other form of unsprung weight, lighter wheels (and tyres) are easier for the shock to control. Shock absorber valving is not black and white, right or wrong. They operate in a window, so if you change the wheel weight (lighter or heavier) only a little bit (within the shock window) that should mean you will feel very little difference. But if you change the wheel weight a lot, then the shock may be operating outside its window. This is of course mostly noticeable with heavy wheels, the shock simply can't control them and traction is lost as a result.

Adjustable shocks are only worthwhile if you know what you are doing with the adjustments. Most of the time shocks have adjustment to cover up for their unsophisticated valving. This means they only work in a small range of conditions and so they have to have the adjustment. Bilsteins have very sophisticated valving and consequently have a large window that they operate well in. Simply put, they don't need adjusting.

So if you do change the weight of your wheels and don't have decent shock absorbers (with a large operating window) then you will have to compromise the rest of the set up by adjusting the shock to suite those wheels. If you don't have adjustment or good shocks, then the best tip is to keep any changes in wheel weight to a minimum.

cheers