View Full Version : Spring Rates

10-19-2012, 04:46 AM
Hi guys,

So I have some KYB GR2 shocks sitting at home, and a full compliment of polyurethane bushings on the way. I'm looking at the 90 - 97 Accord Ground Control coil-overs to replace my current lowered springs. I've just emailed ground control asking for the default spring rates. This has been kind of touched on a bunch of times over at pp.com but never concisely. I am hoping there might be some discussion here on recommended spring rates for a high performance street car (may possibly see occasional track days) with this type of setup and/or in other applications.

Also, when ordering the coil-overs, ground control asks you to specify the shock type you are using - is this for the internal diameter fitment or spring rate? To those of you using the ground controls, what setup did you choose?

10-19-2012, 02:16 PM
Out of interest, ground control replied and said they ship by default 400lbs front and 300lbs rear for the 90 - 97Accord. No extra cost for any custom spring rates.

10-19-2012, 05:35 PM
welcome buddy! those spring rates wouldnt be bad, however, moving the 400lbs to the rear and the 300lbs for the front would be pretty damn good! With our cars the tendency is to understeer. Even with a larger rear sway you'd still notice some understeer. I guess the question to ask is if those spring are the same length that is? My guess is that they are both more than likely 8 inch long springs. Which would be fine... that will get you about this low...
If you wanted to go lower i'd suggest shorter springs... So if you were willing to spend the extra coin on custom rates, see if you can get custom lengths. I'd go with either 7" springs all around or 6" fronts and 7"rears... That will get you more in the uber low territory. Its what I'm currently running on my red lude but I will say that the rears are at max low but my fronts still have about another 3/4 low... Here is an example of that.

Which brings me to another question... I'm on 500lbs front and 600lbs rear and with softer springs i'd bet the rear would sit lower. So how low do you wanna go?

Outside of that I'll let you know how I see a set of spring rates for our cars...

450f-450r, feel pretty good on the street without being to harsh and when used with a upgraded rear swaybar (addco, koni) you'll have good highspeed stability (aggressive fast cornering) with a touch of under steer if even noticeable. Street tire friendly even with performance all seasons.

450f-550r, feel good on the street and with out the use of a upgraded rear sway, you'll get about the same feel as the above setup, however, this is going to tax your rear struts quite a bit more... This is where I'd HIGHLY recommend something more than the GR2s... This is going to push them quite a bit. *If running with a upgraded rear sway bar your going to notice a much better feel at lower cornering speeds however high speed (excess of 70mph) is going to be a bit twitchier... Street tire friendly but consider max summer here...

550f-650r awesome handling car that will require upgraded shocks front and rear. GR2s are going to struggle with this spring rate in the front and really my OTS konis last about 1.5 years of racing with this spring rate in the rear. OTS koni yellows are going to be perfect for this front spring rate. When paired with a meaty rear sway bar expect off throttle oversteer with ease at speeds as low as 35-40mph. Pushing street tire friendliness and to be honest, might be a little to much for most... I've almost wrecked my car on several occasions because of the off throttle oversteer. With adjustable rear konis running on a softer setting will calm this down quiet a bit and make street driving safer. Pushing soft street tire friendliness... works great with top of the line competition street tires and great for entry level R-compound driving/racing.

Moral of the story, if they are selling you 400/300lbs springs that are 8"inches long and you feel that my first picture is plenty low, I'd go for them. If you want lower consider getting shorter springs... if you want insane 1+g handling, look towards the higher springs rates and shorter springs, although the drawback is shock life unless you have konis... The GR2s should do a decent job at handling the 400/300lbs spring combo, so you'd be ok for a couple of years like that. And your car would be a blast to drive out there with that spring rate... Hope this was helpful...

btw, my next set of springs are going to 6" long 600f/750r springs... yummy!!!

10-19-2012, 05:40 PM
oh yes, and to answer your question, its the diameter of the shocks that requires them to ask. the Konis are a little bit thicker i think... either way what you can do is measure your shocks right now and be prepared for there answer when you ask the the ID is of the two options. you might be able to get a snug fit or perhaps avoid buying the one that is TOO small!

10-20-2012, 03:45 AM
Thanks mate, those are very helpful replies. The most important thing for me is that the car is street and street-tyre friendly. I enjoy driving the mountain roads around my home but the roads although interesting are not necessarily in very good condition. Performance is more important than ride height. I want it as low as I can while enduring the car is at least 100mm from the ground at the lowest point (legality), which for me is the bottom of the extractors - this will be only slightly lower than it currently is but I think the coil-overs will benefit in terms of quality, durability, and adjustability. I'd prefer to use the GR2 shocks I currently have sitting around.

So with your red lude, you say the rear is at max low and front at 3/4 of max low - you are referring to the perch position on the coil-over, right? How about on the white/green lude? How high roughly is the undercarriage of the red lude from the ground? Seems like maybe the shorter springs are the way to go, given the ability to wind the perches up if needed.

cygnus x-1
10-20-2012, 09:27 AM
FWIW, my Leda coilovers are 400F 600R, both sway bars stock. It's pretty stiff but still quite manageable on the street with 15" wheels. With 17" wheels it would rattle your teeth out. I can't say I've noticed any understeer or oversteer, but then I don't race so I'm sure I've never really pushed it to the limit.


10-23-2012, 03:48 AM
Just got a reply from ground control. Apparently the coilover inner diameter is made "much" smaller for Koni shocks but is the same for all other shocks (at least all those listed).

10-25-2012, 01:08 AM
So if I use extended top hats, will this ameliorate the extent to which 450/550 spring rates would badly effect the GR2 shocks?

When you do extended top hats, do you just pull the top hat from under the shock tower and re-position it on all-thread/bolts at the appropriate height above? Or is it better to retain the top hat under the shock tower and use additional top hats above the shock tower for extra rigidity?

It is a toss up between 450/450 and 450/550 for me but I'll probably stick to 8 inch length. With all the engine modifications, I don't want the car to have any obvious visible defects (too low).

Thanks for the help guys.

10-25-2012, 03:49 AM
The top hats really help with the shock travel. It will help the gr2s last longer under extreme lowering. Really i would recommend using them with anything lower than 1 3\4" or 45mm. The trick is to not make the top hats too tall, hence why the carriage bolt style is preferred, they are adjustable. With this setup you use two pairs per side and use 1/2" carriage bolts that are stainless. Id get the seven inch, cause you can go higher but you can't go lower

10-25-2012, 08:39 AM
Yeah I made mine too tall and it preloaded the spring so much it was like a pogo stick! Really pulled the car down though lol
I wound up using oem tophats, my springs are just not typical lowering springs, the coils have different spacing on top than the bottom.

So, yeah they can be too tall and cause problems. If you're having to compress the begeezus out of the spring to even get the shock nut on it's probably a little too much.

If you used the top hat under the shock tower that would cancel out any benefit of having any extensions above it, in other words extended top hats are part of the coil and shock assembly. Nothing else is needed above the tower but the original nuts.


10-26-2012, 06:35 AM
Okay that just confused the hell out of me. You modded yours differently to how I have seen. I'm talking about the mod where the top hat is moved to above the shock tower and is held higher by three carriage bolts. The shock piston bolts to this - in which case, do you need to use two top hats per shock tower and keep one underneath the tower and one extended one above?

I just found a thread for this by the way... took a while cos the search engine wouldn't accept "top hat mod" since all the words are less than three letters long. http://www.3geez.com/forum/showthread.php?t=61806&highlight=tophat I think this basically clears it up for me mate but I'm still not sure how exactly you accomplished your mod 2oodoor? is it some kind of tube welded to the top hat? Looks good but I think I prefer the carriage bolt style for adjustability like hondalude86 said. Cheers

10-26-2012, 11:15 AM
Yes I would say you would need extra hats to make a sturdy spring seat. You'd have to cut the centers out of the ones under the tower so the shock body could travel through the tower. I feel the style I have is much easier to make , thats just pipe. This is how the aftermarket extentions are made for other cars.
A calculation needs to be made of how much you need before hand, mine were too big. I think 1 to 1.5 inches would be enough normally..why be normal right lol
I do see the benefit of adjustability though and this can get very confusing indeed.

10-28-2012, 07:47 PM
So in Australia, there is a replacement rear sway bar available from fulcrum suspension (took over selby sway bars) for AU$370 made to order with an 8 week lead time. It is an 18mm bar described as 'heavy duty'.

What do people think? Compared to the conventional solid sway bar modification (replacing bushings with washers etc.), does this seem worth while?

I'm thinking spring rates of 450 / 450 (or maybe 550 rear) with the Koni GR2 shocks, and this rear sway bar would be a good setup in terms of performance, without significantly increased wear on the shocks, especially with top hat mods. I don't think any higher spring rates are needed considering the car is a street car.

10-29-2012, 04:45 AM
I think that would be nice! My sway is only a 19mm setup, so this isn't much smaller at all! The stock si sway bar is 13mm, so this would be a good step up! I think your setup will be nice and leave you shine room to grow to (like better shocks in a couple of years). I will say that you won't need extended r top hats in the rear as they have 5" of travel in the rear! Just the fronts.