I have another car (Lexus) and, Im looking for information about some coilovers. Mainly Concering spring rates.
I asked this question on Clublexus.com but i didnt really get the answer i was looking for..

I've been doing some research to decide which coilover will be best for me and my 96' LS400.

Im looking for a coilover with a spring rate that will help me gain a Sporty
feel without loosing comfort. Im hoping to retain a somewhat smooth ride. I understand that anything i buy wont be as smooth as factory.. Thats fine.

Now, i found some coilovers that have different spring rates at random places online..
Id like to know how these different spring rates i have found will change the feel of the vehicle:

-Megan Street LP (12k Front / 10k Rear)
-Megan Street LP (10k Front / 8k Rear)

-Megan Luxury Series (16k Front 12k Rear)

-Ksport Coilover (18k Front / 7k Rear)
-Ksport Coilover (18k Front / 9k Rear)

-JIC FLT-TAR (12k Front / 9k Rear)

-JIC FLT-TAR VIP (14k Front / 7k Rear)

Im sure there are custom springs available at different rates.

What i would like a better understanding of is... How will the changes in these spring rates change the ride of the vehicle.

Thanks guys.

 

Wow, some of those spring rates seem AMAZINGLY high. Now I know that more weight on a stiff spring will not feel as harsh as lighter weight on that same stiff spring. But still, that 18 kg/mm spring is over 1000 lb/in!

I think first, though, you need to find out what the spring rates are for the factory suspension, as most of us around here probably don't know squat about Lexus LS400's.

 

Keep in mind that motion ratios will play just as large of a role as weight in determining proper spring rates. I'm betting that this Lexus has an odd motion ratio requiring some rather stiff springs.

Bingo. All I could tell you is that it's a 3700lb RWD luxury vehicle with double wishbones up front and a multi-link setup in the rear. That's not much to go by.

 

yeah yeah, that damn wheel motion ratio gets me every time I always forget about that.

A car like that could very well have 1000 lbs. or more on each front wheel, and if by chance it had something around a 2:1 motion ratio, that could be over 2000 lbs of load on each front spring. I guess those 10k springs are starting to look pretty soft now, as they would get compressed nearly 4 inches with a load like that. Hopefully the springs are long enough to keep them away from coil bind.

All just guesses of course. Without measurements or at least pictures of the suspension I don't know anything for sure.

 

Actually, here's a page about converting the stock air suspension on an LS400 to conventional coilover-type springs and shocks.

http://www.lextreme.com/ascon.htm

From this diagram, it looks like it very well may be a near 2:1 wheel motion ratio:

http://www.lextreme.com/PDF/suspfrontaxial.pdf

But again, without having some idea of the stock car's spring rates, there's really no way to say how those spring rates listed above will affect the ride and handling. Although that's hard to say, too, since the original suspension is actually air bags. www.strutmasters.com offers a conventional spring/shock kit for LS400's that is supposed to maintain the factory luxury ride, but it doesn't say what the spring rates are for the springs that come with the kit.

 

Get a set of Bilstein HD dampers and convert them to coilover use as this thread on supraforums demonstrates. You can then have your choice in spring rates. Bilsteins are better than all of the dampers mentioned in the original post. HD valving is exactly what you are looking for -- improved handling and stability without sacrificing ride comfort.

 

x2.

 

My car isnt equipped with Air suspension. I have a standard coilspring over shock design just like and honda/acura would have.

The problem with using a generic coilover with a Bilstein shock is.. i wouldnt be able to lower my car significantly which is something im looking forward to. Im not looking to turn it into a race car by any means.
I just want it to be height adjustable with a sporty feel. I dont want to loose the lexus comfort.

Many lexus owners have used the Megan, Tien & JIC coilovers. The Megans are more in my price range at just under 1,000 bucks.
They say that the ride is nice, not bouncy and still rides smooth. Also, they lower the car several inches.

Thats basically what im looking for and im most likely to get the Megans.

I would just like a better understanding of how the different rates will affect the way the car feels.

As an example:

Which is Stiffer, Which is Softer...

12k Front / 9k Rear
or
14k Front / 7k Rear


Thanks for the help guys..

 

Don't forget 18k springs will act differently depending on how aggressive the strut is valved.
Valving has a lot to do with it too. For example, I'm running 14k in the front and they're not "stiff" what so ever.

 

I'm amused that someone would even consider Megan coilovers for a Lexus. I wouldn't install them on a shitbox Kia let alone a luxury flagship. As for JICs, I wouldn't even give them the privilege of lining my garbage can.

Without having any firsthand experience with the car in question, my best guess is that the 14 kg-mm front/7 kg-mm rear setup would feel less harsh in general - but you need to also factor in how the dampers are valved/set because dampers can play a greater role in ride quality than the spring rates.

 

No wonder you said that you didn't get the answer that you are looking for on club lexus. You want two mutually exclusive things - a ride height barely off the ground and some semblance of comfort. You aren't going to get what you want without significantly revising the suspension beyond adding coilovers. How much suspension travel do you think you are going to have if you are planning on lowering your car significantly as you said above? If you don't want to be riding on your bump stops and risk ruining your dampers while lowered, you will have to have use a higher spring rate. That isn't going to do anything for comfort.