Hi Guys

Please help me out, I want to use 650 pounds spring rates at the rear of my Sentra B13 and 600 at the front with the Koni 8611. I will get a coilover made up with this setup. Just one question is this spring rate too stiff if the car is used on the street ? The car is presently not a daily drive.:)

That setup is "soft to medium" in terms of stiffness for a B13 race car but it would be very stiff and uncomfortable on the street.

Thanks,what would you suggest as a decent spring rate for my car. I will use it mainly for the street and sometimes for some track days.The car is making 221 whp at the moment but will be making 400whp ultimately. Most guys use 300F and 200r in the forum, i think but will this be okay for my setup.

Honestly, I don't know what you should use for "street" springs.

300/200 are fine for a DD, 350/300 would handle a little better, but be a lot more unsettled on the rough stuff.

Thanks alot guys for your input. I might go for the Eibach ERS 350 front and 300 rear. I don't might a slightly rough ride as long as she handles well with that power.:D

What are you going to be doing with the car?

The car will be used on the street and for some track use.

The car will be used on the street and for some track use.

I've used 350/250, 450/350, and 350/300 rates on two nearly identical B13's, for pretty similar use. The highest rate car sees more track use. I drive both on the road and personally I find the combo pretty much ok for DD use. Some people wouldn't like it. I don't do much hwy, just a lot of back roads ;)

I have one car with 350F/300R with Shigspeed CO's (DA Koni Inserts). That's a pretty good balance. I like the 450F/350R on my first B13 a lot better even as a DD, and my roads are not so great.

I found 350/250 to be the low end for "some track use" - I don't recommend it. Even with the GC plates etc. I'd run out of travel up front at times, esp if I had a second person in the car - which is a given for most HPDE or other track events if you're new to the track or even to the hosting club, etc. You will have an instructor in the other seat. I could have brought the car "up" a little but I like it where it sits now relative to the pavement.

You have to look closely in these pics to see the difference but #1 the tire would occasionally rub (350F/250R), #2 I never have that problem now with bumping up the springs another 100 lbs each end (450/350). Keep in mind the car at rest is fairly low, too.

#1 350/250 wasn't enough when you pushed the car with two people - not enough spring, this is turning into the oval at Pocono North Course, a reasonably fast turn with a little drop and rise. This is my nice pal Nick, trying to scare the crap out of me showing me how to run North course with minimal braking and probably 2 seconds faster a lap than I still can run it...there's a vid under user superblackser on youtube, "Nick...Pocono" something so you can get the idea :)

http://www.cartct.com/results/05-08-09/05080989.jpg

Same spot 3 months and #2, a new set of Progress CO's 450F/350R later:
http://www.cartct.com/results/08-28-09/082809333.jpg

#3 There's plenty of travel for a B13, but not a ton of clearance, but I don't rub tires with the newer higher rates. I run faster, too, or so the clock says. There's a little drop on my driveway pass side so this looks a little more than it really is:

http://www.sr20forum.com/gallery/data/1512/DSC00270CR.jpg

Crappy pic but best I have showing clearance while at rest on level ground.
http://www.sr20forum.com/gallery/data/1512/IMG00090-20090828-1551.jpg

The car with the 350/300 is noticeably higher off the ground, more of a "performance DD" setup although pretty good kit on it for street use - besides the shigs, progress bars, F&R STB's, GC plates, etc.

http://www.sr20forum.com/gallery/data/1507/DSC00232cr.jpg

My own limited experience I really like the GC plates for giving a little more front travel with the car lowered. Or maybe "better" travel. Both cars use them, both run zero toe rear and tiny amount or none in front, and ~-2 degs camber in front, -1.5 rear.

If you can tolerate a little stiffer ride, go 450/350. If not, drop to the 350/300, it's a good compromise for a car with occasional track outings. Don't go lower, or you may not like your track outings.

HTH :biggthump

Hi Guys

Please help me out, I want to use 650 pounds spring rates at the rear of my Sentra B13 and 600 at the front with the Koni 8611. I will get a coilover made up with this setup. Just one question is this spring rate too stiff if the car is used on the street ? The car is presently not a daily drive.:)

Yes that would be too stiff on the street, you'd hate it. You need to come down at least 100 lbs/in. I'd also consider more front than rear spring, as in higher up front than rear, opposite of what you see on a lot of B14's set up for track.

SuperblackZ, That was a great post, very detailed! Not to get too far off topic, and it might be helpful for the OP; where did the idea of going softer up front on the B13 come from? I've noticed a couple of posts of folks doing it, and it seemed counter-intuitive (more weight bias in the front, wouldn't you want stiffer springs in front to lessen pitch moment in the front?).

For the OP, I have been running 350F/250R during the last season, and I am going considerably stiffer for next year (this is for a SMF AutoX car that sees occasional DD and Track duty), as I found it good for the street (including the occasional railway crossing), but too soft for competition.

Darrin

I agree with Darrin although the front spring stiffness might go up/down depending on front sway bar (if you are using it or not) which adds a little stiffness in the front. Without the front bar I would run considerably more stiffer springs in the front. The rear stiffness will depend on lift-off oversteer that the driver desires (and can handle as I have noticed that the racers actually prefer the back to be stiffer by about 100lbs/in or so if they are in the 600lbs/in range).

I am currently running RM (325/250) and my last track day on a medium speed track was not very enjoyable (way too soft), although I did enjoy my ride to and fron the track on the highway (very soft with AGX's on setting #1).
Next year I am switching to 600/500 for my car as the car will become primarly a track car with little daily driving.
Depends what you are using your car for and how you want your car to behave on the track.

Hope it helps.

Just remember you need some serious dampers to run 600 lbs/in spring rates. My Progress CO's are valved for the springs I run, if I was putting another 150-200 lbs/in of spring I'd have to send them back for a rebuild. I might instead use the Shigspeed's from my other B13 with the Koni Yellow 8611 Race Double Adjustable inserts. Hard to beat and even with the 350/300 springs on the road the car rides very nice adjusted down quite a bit. Downside is they cost almost as much as I paid for that car, hard to justify for a dual use car. Good description of these here, scroll down to Shigspeed. Getting a new set, that's another story. I had to find a car with them already on it to get a set - barely used :)

http://www.sr20forum.com/driveline-transmission/170794-b13-b14-b15-suspension-information.html#post1651580

One thing I like about the Progress CO's is despite lack of adjustment they are tuned really well to the B13 and the spring rates out of the box. That's hard to beat for I think ~$1500 full MSRP. The Hyperco + AGX is more impressive than I expected for a strut-based setup, too, it's pretty good.

As for the 350/250 or similar, check the rear sway bar on any car running that low in the rear, you will see the rear sway set on max stiff if its adjustable. Besides obvious issues like tripod at autocross, you turn your ISR into a beam suspension. On the track you really screw the pooch doing this, because you have too soft front springs causing massive frontal weight transfer under braking and even turning, then you lift the rear wheel(s) reducing their traction and even causing a "skip-lock brake-skip" as the rears gain and lose traction. I've been able to back off my rear sway, keep the rear flatter since I bumped up +100. I'm glad Progress talked me into raising the rear higher than I originally asked them.

The idea of going softer up front comes also from the typical B14 race setup, it's pretty common. Most of what I have to say and some good comments from Mike K here:

http://www.sr20forum.com/driveline-transmission/170794-b13-b14-b15-suspension-information-13.html#post2350459

At rates under ~500 I don't see people running softer up front. Or I haven't seen anyone yet. I think the B13 needs at bare minimum 350F for mixed use, and the 450F works a lot better for me. If the ride is rough it's probably also the dampers used and chassis stiffness, not just spring rate.

You simply cannot do enough to make the B13 chassis "too-stiff". Besides the IKEA brace that came with the car, I added octotat's tubular steel RSTB and triangulated trunk braces. Before that I just felt like the rear suspension was attached to flimsy pieces of sheet metal vaguely associated with my car. With triangulated FSTB and Progress LCA, now what I notice is I have a car that is stiff in the rear and the front, but a noodle in the middle. Only a cage is really going to address that, but I'd like to look into foam-filling the side rockers, too. That stuff works well if you do it right.

Probably be starting next season with a cage, besides the handling benefits, I'm already way outside the safety envelope for some of the things I did this season to not be using at least an Autopower-type bar with rear support and diagonal cross bar. I never use the rear seat anymore for more than carrying wheels anyway :D

Some nice information there guys, thanks. At this moment i am thinking of either getting the Bits and Pieces setup with the 8611 or the Progess coilovers , with the appropriate spring rates.

My track car is currently on 500/600lbs with 8611's. It's really too much for the street. It works fairly well on track but it really needs even higher rates to be at it's best. SuperblkZ is right about the dampers too. Also when going beyond 500lbs the car really needs a good cage. The shells of our cars are not strong enough to handle such rates and will flex. Alot. I ran 450/500 for awhile and it was tolerable on the street. However my car only sees street duty to and from trackdays.

im not sure about pounds but 8kgmm F and 6kgmm R should be tolerable on the daily drive and enjoyable on the track

im not sure about pounds but 8kgmm F and 6kgmm R should be tolerable on the daily drive and enjoyable on the track

Edit: for close conversion just multiply by 56

For my B13 it works pretty well (447 lbs/in and 335 lb/in is close to my 450/350). Just so long as you have reasonably matched dampers and enough chassis rigidity to handle the springs. Just for the chassis I have -

Progress LCA Brace
FSTB integrated to the GC Camber plates, -2.2 deg front camber, -1.5 rear
Triangulated FW Brace
Chuck's RSTB with Triangulated Trunk Bracing
IKEA Brace welded into the back seat trunk opening

plus much stiffer front mounting points with GC plates and pillow mounts, full ES bushings including LCA's, and corner weight balancing. As I probably said before I need to address the car's middle with a cage and/or some other things.

My caution is if someone doesn't have some additional measures in place in their B13 and puts even this level of spring they may find w/o the camber changes and stiffening reinforcements they will degrade rather than improve the handling. But those are pretty reasonable rates, yes.

SuperblackZ, That was a great post, very detailed! Not to get too far off topic, and it might be helpful for the OP; where did the idea of going softer up front on the B13 come from? I've noticed a couple of posts of folks doing it, and it seemed counter-intuitive (more weight bias in the front, wouldn't you want stiffer springs in front to lessen pitch moment in the front?).

For the OP, I have been running 350F/250R during the last season, and I am going considerably stiffer for next year (this is for a SMF AutoX car that sees occasional DD and Track duty), as I found it good for the street (including the occasional railway crossing), but too soft for competition.

Darrin

IDK where that comes from unless it's a B14 setup where I see that fairly often more rear spring than front. Apples/Oranges comparing across the two cars, with a completely different chassis and rear suspension.

I also found 350/250 too soft for autox, I had dialed up my sways in a vain attempt to control roll and dive and just tripod'd instead. The 450F/350R is a much better combo all-around. Not track racing rates but very good for autocross and HPDE's, TT's.

My track car is currently on 500/600lbs with 8611's. It's really too much for the street. It works fairly well on track but it really needs even higher rates to be at it's best. SuperblkZ is right about the dampers too. Also when going beyond 500lbs the car really needs a good cage. The shells of our cars are not strong enough to handle such rates and will flex. Alot. I ran 450/500 for awhile and it was tolerable on the street. However my car only sees street duty to and from trackdays.

Good info, that's kind of where I can see capping my dual use car with time. My second car has Shigs/Koni 8611's DA with 350/300 F/R, which is kind of overkill dampers for those rates even with the adjustable compression and rebound. Thinking maybe put my second set of Progress CO's on that car when I have them rebuilt, dampers on those are matched to a 350/250 set. Good enough for a primarily street use car with backup if my other car is down for some reason.

im not sure about pounds but 8kgmm F and 6kgmm R should be tolerable on the daily drive and enjoyable on the track

Close to 450 lbs/in and 350 lbs/in.

1 kg/mm = 55.88 lb/in is close enough to compare rates.