BC Coils; 4k spring rate jump w/o revalve

[jumpman2334]

Quick background: Car is an 04 is300 with BC BR coils ('extreme low' installed) it is valved for 12/10k and has 12/10k standard springs on it. Here is what it looks like now:
https://c1.staticflickr.com/3/2894/33717864840_5def6476f2_b.jpg

I quickly realized that if I wanted to go any lower I need to up the spring rate. I emailed BC to see if I could do 2k safely. They got back to me and said I could do up to a 4k rate change, but not use the last two stiffest clicks on the shock adjustment (fine with me). That puts me at 16k/14k.

My question is, has anyone bought, say, PBM, BC, FA, or Megan coils and jumped up 2k or 4k spring rate? Did you notice immediate shortened shock life or diminished performance? This is my main concern (I realize this will shorten the life of the shock to some degree no matter what). the car is not my daily, but I would like to not turn this thing into a turd (anymore than I already have).

BC charges 95 bones a cartridge. I don't want to buy dampers if its not needed. with the cost of the swift springs, thrust sheets, and dampers I could just throw a couple more hundred bucks at it and bought another set of custom valved coilovers.

If anyone has had experience with stiffer rates (16k+), im curious to think if you think 16/14 will be stiff enough, or if I should just sell these and buy stiffer coils.

I realize this forum is for nissans and what not, but the lexus/IS forums are dead and a fair amount of the active memebers on those forums don't even have coils. Any helpful input is appreciated; TIA.

[!Zar!]

On my IS300 I had 12/10. Way too soft

Then I put on some 14/12 springs. Still too soft.

After that, I sold those coils and got some custom valved for 20/18. I was happy with this.

I suggest just selling your and buying some how you want them.

I also suggest getting swaybars if you don't have any. I ran the TRD Yellows front and rear. Loved them.

Also, Fuck MY.IS.

[Dirk Jan]

I've seen your car on MY.IS and I'm quite surprised you're only running 12/10k at that hight. I Never actually thought about this, but I'm kind of in the same situation. Running HSD coils on my Altezza (also valved for 12/10k springs) and bought SWIFT 18/16k springs for them. I thought I would be able to just adjust the dampening to compensate for the stiffer springs, kinda stupid now that I think about it.

I think most SXE/JCE coilovers are valved for 12/10 or 14/12 though, and I see loads of people putting stiffer springs on (some people as much as 30k up front). As said above, I think the main reason people go for springs that stiff is that they try to eliminate body roll. If you get uprated sways you might be able to get away with just a 4k jump. I've bought ARC sways which are quite stiff (+146% front, +216% rear) So i'm hoping 18/16k will be enough to keep it flat.

[ThePaddy]

Bc support said 1kg or 2kg is likely ok but recommend buying a mstching shock.

Get on to support they eere super helpfull.

Sent from my SM-G930F using Tapatalk

[jumpman2334]

zar, thank you. the 20/18 isn't too bad of a ride? im actually surprised how soft 12/10 is in these cars, it doesn't seem stiff or jarring at all like ive heard from some people who don't stray from 8/6. i do also eventually plan to get sways once i figure this spring rate issue out and get some fresh bushings/arms in the car. My.is is certainly an odd place; i am on zilvia far more than i am on my.is.


dirk, at 12/10 this is about as low as you can go without shortening the spindles, IMO (i can go lower in the rear, but i need to roll it more, its a PITA compared to the fronts). my fuca surprisingly only hits the fender well on bigger bumps, but id like for it to not do it at all. i have a spare set of spindles and some steel to make a jig for shortening them, i just need to make the time to get it done. i know someone who has a GS (which have the same spindle problem as us), he has 32/30 rates, the 10mm shorter s9 fuca and some thick RCAs, from what i understand it all helps, but he really needs shortened spindles as he is lower than i. i haven't heard of those sways so i will check them out. thanks.


RE: stiff springs; its funny you mention that. i saw a guy on IG who is running 326 coilovers with a crazy spring/damper rate pairing. i looked earlier and couldn't find it, but it was something like 44/40k for the springs, and the valving was low 30s. it was weird. i googled 326 coilovers and found that stance nation can get them. check out the crazy gap in spring rate between the front and rear:
https://parts.stancenation.com/products/lexus-is-300-coilovers
(100k/45k... LOL)


paddy, ive contacted them a couple of times. i was originally told 4k, then they jumped back to 2k, so i called them and confirmed its 4k on the 'extreme low' models; not sure if its the same for their standard coils.


thanks again all.

[!Zar!]

I shortened the spindles 30mm on my IS, and my GS. Then went with 30mm RCA's to bring the arms back to the same level.

8k/6k coils were made with the Altezza in mind which had the lighter 3sge powering it.

Since the IS got a 2j, most coils aimed for that setup came with 12/10.

I also suggest shortening your spindles if you're having upper ball joint hitting. Otherwise you're going to accelerate ball joint failure, wheel bearing failure, and bend/crack wheels.

You could try cutting out the shock towers, but I'm not a huge fan of that.

20/18 felt Totally fine on the softest setting.


Sway bars make a huge difference. You won't regret it.

[jumpman2334]

thanks for the info Zar, it certainly looks like ive got some parts to order and some shit to cut up!


Have a great weekend!

[Dirk Jan]

Yep, due to the way the shocks are mounted further down the FLCA on these cars (at about 2/3 from the pivot point) the "effective spring rate" is way lower. I've heard people say a 18/16k setup feels like a 10/8k or 12/10k setup on a S chassis car.

At the height you're running I assumed you already had your spindles cut. I had mine shortened about 30mm, but welded back in offset. If you don't do this your static camber will decrease. I can post pics if you want to show you wat I mean.

Also, 100k springs... I feel like you might as well fit solid metal bars as coilovers at that point. Lol.

[jumpman2334]

At the height you're running I assumed you already had your spindles cut. I had mine shortened about 30mm, but welded back in offset. If you don't do this your static camber will decrease. I can post pics if you want to show you wat I mean.

Also, 100k springs... I feel like you might as well fit solid metal bars as coilovers at that point. Lol.
I wish, ive been slacking. i am aware of the offset issue, just not sure how much i need to offset it. how much did you offset it? how much camber did it give you?

100k is definitely metal bar territory.

[1on1]

For the record, I am currently running PBM 20kg springs in the front (8kg in the rear with front shocks) with PBM's version 1.2 coilovers (printed box with black shocks; not silver) and the ride quality is fine for me. However, my car tends to understeer a lot more due to stiffer front setup with crappy tires (ns-20), but I have yet to test my car with yokohoma s-drives in the front.

[Dirk Jan]

I wish, ive been slacking. i am aware of the offset issue, just not sure how much i need to offset it. how much did you offset it? how much camber did it give you?

100k is definitely metal bar territory.

I'm at work atm and it's kind of hard to explain what we did without showing pics.

I've not fitted the cut spindles yet as I had every bit of my suspension sandblasted and repainted. Will start fitting everything next weekend, so I'll let you know how it turns out if you want :).

[Ratpack_Chad]

For the record, I am currently running PBM 20kg springs in the front (8kg in the rear with front shocks) with PBM's version 1.2 coilovers (printed box with black shocks; not silver) and the ride quality is fine for me. However, my car tends to understeer a lot more due to stiffer front setup with crappy tires (ns-20), but I have yet to test my car with yokohoma s-drives in the front.

I'm running 16k/14k SWIFT on my PBM gen 1's on my s14 without re-valving and the ride quality is arguably better than before. Probably just due to having Swift springs Vs the stock garbage. I haven't had any issues with them so far.

[s13silvia123]

For the record, I am currently running PBM 20kg springs in the front (8kg in the rear with front shocks) with PBM's version 1.2 coilovers (printed box with black shocks; not silver) and the ride quality is fine for me. However, my car tends to understeer a lot more due to stiffer front setup with crappy tires (ns-20), but I have yet to test my car with yokohoma s-drives in the front.

adjust your dampening to reduce the understeer. you have to play with your settings in small increments to figure out what works best with you.

[1on1]

I'm running 16k/14k SWIFT on my PBM gen 1's on my s14 without re-valving and the ride quality is arguably better than before. Probably just due to having Swift springs Vs the stock garbage. I haven't had any issues with them so far.

This is good to know. My ideal setup i wanted to try is 18k/16k but my buddy had 20k springs sitting. So far, I like the quality of the ride and I definitely need to tune it.

adjust your dampening to reduce the understeer. you have to play with your settings in small increments to figure out what works best with you.

I haven't been able to fine tune my settings (currently it's set to 5 clicks) because I just slapped on the springs and left the settings. Once I am able to attend a test day at Balcony, I will be fine tuning it by starting with the softest dampener and then raise 2 clicks after a few runs.

Thank you both for your feedback. I've been itching to go drifting and my current fix is playing assetto corsa, lol!

[jumpman2334]

For the record, I am currently running PBM 20kg springs in the front (8kg in the rear with front shocks) with PBM's version 1.2 coilovers (printed box with black shocks; not silver) and the ride quality is fine for me. However, my car tends to understeer a lot more due to stiffer front setup with crappy tires (ns-20), but I have yet to test my car with yokohoma s-drives in the front.
I don't own a 240, so I am not familiar with the S14 PBM spring rates. Are they 8/6? No revalve on the front? No issues with dampening or ride quality?

That was another big question I had on post #5. The 326 power coilovers I saw had 40k springs and the cartridge was rated for low 30s. Maybe you can get away with jumping more than 2-4k without a revalve? Maybe im overthinking this? If I don't have to buy 400+ dollars of dampers if I don't need to (at that point it would be easier to just sell then buy new dampers).

I'm at work atm and it's kind of hard to explain what we did without showing pics.

I've not fitted the cut spindles yet as I had every bit of my suspension sandblasted and repainted. Will start fitting everything next weekend, so I'll let you know how it turns out if you want .

Basically like this, right?

http://a.driftworks.com/blog/wp-content/uploads/2012/07/JZX110Mark2i-666x399.jpg

source: https://www.driftworks.com/blog/2012/07/jzx110-mark2-build-part-1-welding-and-bashing/

[Dirk Jan]

Basically like that yeah. The thing is though, the more you weld them back in offset the less tire you can run. I wanted to retain the possibility to run decently sized tires when I want to (trackdays, etc.). So what we did is cut the top part off, then slice a 30mm long chunk off the remaining arm (at about half the thickness of the arm), and then weld the part we cut off back to the cut side.

Can only find this pic atm, but I think you should be able to see what I mean:

http://i.imgur.com/5TIXA2l.jpg

[1on1]

I don't own a 240, so I am not familiar with the S14 PBM spring rates. Are they 8/6? No revalve on the front? No issues with dampening or ride quality?

That was another big question I had on post #5. The 326 power coilovers I saw had 40k springs and the cartridge was rated for low 30s. Maybe you can get away with jumping more than 2-4k without a revalve? Maybe im overthinking this? If I don't have to buy 400+ dollars of dampers if I don't need to (at that point it would be easier to just sell then buy new dampers).


I know PBM's competition line-up are 10k/8k for spring rates and stiffer dampening compared to their PRO Coilovers (8k/6k with softer dampening with additional stuff to it).

I can see your dilemma and I don't know the quality of BC Coilovers since I never owned a set. If you're going from 12k/10k to 16k/14k, I think you should be fine and would consider BC's recommendation of not using the last 2 clicks.

Otherwise, if you plan on using higher spring rates, I would definitely get custom dampeners done with the new set of springs.