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Discussion Starter #1
Can someone (or Knightshade, please?) give me some insight to this.


Ok, we know our standard Sport package springs are linear rate. We know the F-Sport Spring from the accessory is progressive rate which we know is inferior (or unpredictable).

So my question is, why is Lexus making F-Sport spring progressive??? Are they trying to decrease the performance? Isn't it to increase performance though? I'm lost.

Or does it need to be paired with F-Sport Shock Absorber set in order to work better? Well, will it then surpass the performance of a car with linear rate springs?


Please give me insight, as I'm planning to lower my car later in the future. Thanks.
 

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Honestly I've no idea why anyone buys progressive springs. I suspect not knowing any better plays a role.


As to why they exist, I suspect it's a bit like why all season tires exist, despite them delivering inferior results to the alternative.


They're a compromise that aren't great at anything they try to do, but they kinda give you some of both worlds.... just like All season tires work "ok" in the summer and winter, but come in 2nd or 3rd place compared to tires dedicated to working in those conditions.


Progressive springs are softer under light load, and firmer under hard load.

In theory this means a comfortable right when just cruising around, and enhanced performance when pushed.


And for folks who when you're honest about it spend 99.9 of their driving on smooth highways and smooth paved roads, and don't really push the car very hard, they seem to be fine and hey, "slammed" is sexy right? So for these people who just want a "drop" they can buy the springs and until they're on a bad road won't notice there's anything wrong at all.


But for folks who go over more significant bumps or poor roads, they suddenly notice progressive springs kinda suck because it impossible to properly match a shock to them since their rate changes.... so suddenly their F-sport springs with stock shocks are unpleasant over big bumps... and those stock shocks were out a bit sooner than they otherwise would too.

And if they take it to a track they notice the spring rate changes halfway through a turn, which can be an unpleasant surprise.



Mostly I think the F-sport springs (which are really just rebranded aftermarket lowering springs after all) exist because it was cheap/easy for Lexus to slap their name on em and offer a way to lower the car inexpensively.

I suspect if you actually ran a stock sport-suspension car at the track versus one with F-sport springs on it, the stock sport suspension car would turn in better times. And the stock one will certainly do better over larger road imperfections.

If I were ever looking to lower my car I'd do it with coilovers- even if I had no intention of changing heights on a regular basis- because I could get linear springs with custom rates and a shock designed to match it.

With progressive springs your shock will always be either overdamping or underdamping for one end of the spring rate or the other.


But again, all that said, on smooth roads, the progressive springs will give a softer ride than the stock sport springs will, because they spring rate is lower... probably not as soft as the stock non-sport springs though.

When pushed the F-sport springs won't be as predictable as the Sport springs, but they will be firmer than the stock non-sport ones.

Linear firm or linear soft will always be better at one of the two tasks, but progressive springs are "ok" at both. Linear either will be better on big bumps because of being able to dampen properly.

So, prog springs are a compromise to let you lower the car and usually be ok at most tasks. Not a compromise I want, but many others either do want it, or don't realize what the drawbacks are, or don't realize there's other (possibly better) options.
 

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Discussion Starter #3
Thanks for the awesome info, knightshade. I get it now.

I also heard from a few users that their ride got "floaty" or "springy" since the install of F-Sport springs.

Uhh.... I can't stand floaty ride. I hate soft ride. I am a fan of firm ride. And yes I want predictability. So I'm going to stay away from F-Sport springs. I'm glad I got the info now cause I was thinking about getting them and get em installed at the dealership.

thanks again. :)
 

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Discussion Starter #4
Knightshade, if I go with the coilovers will the Lexus dealership able to install them? Will they know how to set spring rates and damping rate? I'm newb to this. :blush: I want same spring rate, damping rate, and camber setting as the stock F-Sport packaged IS350.
 

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Knightshade, if I go with the coilovers will the Lexus dealership able to install them? Will they know how to set spring rates and damping rate? I'm newb to this. :blush: I want same spring rate, damping rate, and camber setting as the stock F-Sport packaged IS350.
The spring rate is a physical property of the spring, it's not adjustable once the spring is made (other than physically altering the spring).... when you order the coilover (from most makers anyway) you can specify the spring rate you want, and they'll match the dampener to it.... I know BCR is pretty popular on the 2IS and does custom spring rates.

What's adjustable on the coilovers by you (or anyone) will be the height of the car to whatever you want.

A dealer probably could install it (though they won't offer any warranty since it's not lexus parts) but they'll charge you $110/hr to do it... you can almost certainly find a good suspension shop that'll do the labor for 1/2-2/3 what the dealer wants and do at least as good a job if not better.
 

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Discussion Starter #6
Thanks Knightshade. Looks like I got some thinking to do about the spring rate. I guess I would need to find out what spring rate, dampening rate, and camber angles it comes with the stock sport pkg IS350 first...


thanks
 

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+1 for everything Knightshade explained.

Now my 2 cents:

Do not have a dealership install them for you. It will cost you an arm and a leg. I made this mistake not long ago when I had the dealership install F-Sport springs/shocks on my car. I ordered my parts online and brought them in to the dealership. I paid nearly a grand for labor, it was over $150 more than the estimate. I talked to a reputable independent shop afterwards and I could of had it done there for $250.

If I did it again I probably would have gone for H&R springs or coils, but I needed a very conservative drop or else I would not be able to get up my driveway. Even on F-Sports I have to attack my driveway at a certain angle or I scrape.

As for ride. I had the non-sport package springs before and I think there is a large improvement after moving to the F-Sport springs. The ride is much firmer (my preference) compared to stock. I have noticed that sometimes they will be a little bouncy though.
 

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Discussion Starter #8
^ Thanks for the heads up on the dealer's labor cost... a grand is a lot of money. Is that for just installing springs or springs and shocks?


Too bad Lexus doesn't carry linear rate springs as F-sport accessory. :( I might forget about this project as I am hesitant on getting the coilovers as I would like to stay with F-sport Lexus approved parts and retain warranty through Lexus.
 

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It was for installing the springs and the shocks, as well an alignment (which I could have done anywhere else for half of what the dealership charges...or less).

I'd say continue with your project but use H&R springs instead. I've heard pretty good things about them, especially when paired with the F-Sport shocks.
 

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Discussion Starter #10
^ Good to know that F-sport shocks can take HR springs... but those springs are a little too low for my liking. I want 1" drop front and .9 or something inch on back just like F-sport springs... I need to find me a nice set of linear springs.
 

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I think the Tanabe springs offer a drop similar to F-Sport. I have no idea if they are linear or progressive though. You may want to look into those.
 

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Discussion Starter #12
^ Wow, interesting. I went to tanabe site and the manufacturer is Japanese. I love Japanese stuff. I also heard good things about tanabe parts from few fellow members that I know of. In the site I searched the dealer locator for my area and what do you know, my local Lexus dealership carries this. :jawDrop: Never thought dealerships carry such import parts.

thanks
 

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Dear KnightShade.

Good info but please watch this video which timewise and track comparison wise tells a different story. I agree with what you say on spring types but probably there are more factors or just the track F-Sport engages better.

See - https://www.youtube.com/watch?v=ls2vkQlVNmU
 
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