Thread: Setting up your B14 for track day duty

Through the past year, I've been doing a lot of experimentation with various suspension settings on my B14 track day car. Now that the season's over and I have nothing interesting to do, I thought I'd share some of my findings with you guys. It's a bit of a rough overview, but here goes:

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Ride Height

Finding a good workable ride height is annoying on a B14, so I'll tackle that first. If your car will never see a race track, your best bet is to keep your ride height as close to stock as you can. If not, you're in for a bit of fun. As inconvenient as it is with our limited damper travel and everything, the stock ride height is a bit too high for regular track use. The car is just too slow to react, and the amount of body roll and load transfer really throws you off.

In order to make the car really responsive on the track, you do need to lower the front end between 1.5” to 2”, and the rear by about 1”. This means you will need shortened dampers (Konis, Teins, etc) and polycellular bump stops. If your bump stops are longer than 40 mm, cut down the stiffer end. For those of you who may be setting up their cars for the lower end of the range, consider getting an adjustable bump steer kit for your car. Bolt in Bars sells a kit that doesn't require you to machine the hubs and has a wide range of adjustability.

This ride height setting is a bit more aggressive than what is traditionally recommended for our cars, and you will tap the bump stops over big bumps on the street. This is nowhere near bad enough to damage the suspension system though, and it will provide you with a bit of forward rake to help the car rotate through slower turns.

Springs and Antiroll Bars

The traditional recommendation for spring rates is to go with around 300 lbs-f/in for the front springs, and 15% to 20% less in the rear. In this range, I've found though that you can run band-aid some of the inherent handling of the cars by running rear springs that are just as stiff or even stiffer than the fronts. Running stiff rears makes the rear end take more of the roll force, which does three things:

1. The front end rolls less, so the outside front tyre experiences less camber loss during hard cornering
2. The front end rolls less, so the “falling over” sensation you get from the B14’s steep roll axis is lessened
3. The outside rear takes more of the cornering force as well, so the car is more willing to turn in
   

If you live near smooth roads, I wouldn't be adverse to running around 400 lb-f/in up front, and 425 lb-f/in rear. For those of you who are less lucky, I would still say at least 325 lb-f/in front, 325 lb-f/in rear.

I tend to use the antiroll bars to trim the car more than anything else, so I don't really run with big aftermarket bars. This is especially true up front, where I usually run either the stock 200sx front bar or no front bar at all. The rear end on the other hand is fairly forgiving of a big rear bar. A nice 20 mm bar may help the car rotate on a slow track or an autocross course.

Dampers

Shortened dampers, preferably with camber-adjustable top mounts are key. AGX’s can't really damp springs over 300lb-f/in, so again, it's Konis, Teins, or something of the similar. Surprisingly, Tein BASICs provide good bang for the buck here. Not only do they have pretty decent damping curves, they also share the same internals as the more expensive SS and FLEX (regular FLEX, not the Mono-FLEX), and are both rebuildable and revalvable.

Alignment

The first thing I recommend you do is to start doing your own alignments. Buy or build your own toe plate, camber plate, and go find a nice level surface to work on. Get yourself a good probe pyrometer as well. You'll need it to fine tune your alignment settings once you get out there.

If you're running street tyres on the track, I recommend starting with 0.2 deg toe in,2 deg negative camber, and as much caster as you can get (if you can get 4~5 degrees, you're pretty well off) up front. If you're on R compounds, try 0 deg toe-in, and closer to 2.5 deg negative camber up front.

Once you're out and running on the blacktop, use the pyrometer to fine tune your camber settings. Your tyres should show a nice even gradient, with the insides slightly hotter than the outsides by the time you get back to the paddock.

You can’t really do too much on the rear end of a B14. Just make sure your camber is within factory spec, and have the rear beam bent back for 0 deg toe-in.

These alignment settings are fairly streetable, but the negative camber will wear out the insides of your front tyres fairly quickly. I would recommend that you mark your camber plates at 1.25 deg negative camber, and set your car back to that mark when you get home from the track.

Bracing

I subscribe to the philosophy that you cannot have too stiff a chassis. At minimum, I would get both front and rear tower bars and a front lower tie bar. If you aren't planning to go wheel to go wheel to wheel with your car, filling your side rails with polyurethane foam will make a world of a difference - Just keep in mind that it isn't allowed in some race series, and that it can't be undone. A four point roll bar will also help stiffen the rear end substantially, even if it's just a bolt-in piece.

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That's the gist of it. The above setup should sort out some of the odd handling characteristics of the B14 chassis while still keeping it relatively streetable.

Questions, comments, and complaints are appreciated.

A very interesting and fun read. I would suggest contacting Shawn B and shoot him a link to this thread, as he might find it to be a good addition to his Suspension FAQ.

Good stuff man! Appreciate the info and the time to type it out and share it on the forum. I just got my first B14, went with tein coilovers with camber plates and will be getting the bolt-in-bars RSTB and have a Stillen FSTB. I will likely run a progress rear sway bar and stock front sway bar with poly bushings.

Can't wait to get out there! I gotta get the alignment set to, lifetime free alignments at firestone and the guys are really cool, they will set it where I want it.

Brent

"I usually run either the stock 200sx front bar or no front bar at all"

This isn't the first time I've heard someone talk about removing that bar but i was wondering how it changed the handling of the car and if this is a streetable option or just for the track.

There are a lot of people out there who think that removing the front bar is somehow going to turn our cars into undriveable oversteering monsters. Don't worry, this isn't the case. In fact, the base model Sentra and 200sx never came with a front antiroll bar.

That being said, if you're on stock springs don't bother taking the front bar off. The B14's sprung like a Citroen 2CV anyway, so if anything it may even help to leave it on there. It's really the people who are running 300 lb-f/in + front springs that could see a benefit from running without a front bar.

Why would you want to remove the front sway bar at all? I don't get that, the whole purpose of a sway bar is to raise spring rate in turns reducing body roll. unless your saying that the front springs are to stiff? But that doesn't make any sense.

Seems counter-intuitive, doesn't it?

The first thing you have to remember is that eliminating body roll is not the be all and and end all of suspension tuning. Reducing body roll is nice, but it always comes at a price.

EDIT: It seems I confused myself while I was writing this last night. I'm going to fix the terminology before someone else reads this and gets the wrong idea. Changes are in green. Ignore what was there before, cause it was wrong. Sorry guys.

An important property of anti-roll bars is that they increase the rate of weight transfer to the outside tyre under cornering. That is, you will be transferring weight on the outside wheel more quickly than if you didn't have an anti-roll bar. Basically, this means that you will be asking the outside tyres to respond to a more sudden change in load.

On a car with soft springs (like a B14 with factory springs), this isn't a bad thing. Body roll causes camber loss on the outside wheels, which reduces the contact patch, and therefore, traction. By installing anti-roll bars, you can reduce that body roll and keep the outside tyres flatter under hard cornering. Yes, even in this case, you will be asking the outside tyres to do more work than usual. But thanks to the fact that they are flatter to the ground (and therefore have a bigger contact patch), that isn't much of an issue (in fact, you may even gain some traction overall).

On a car with stiffer springs, however (like a B14 with Road Magnet springs), it's a slightly different story. The 325 lb-f/in front springs will resist body roll on its own, so the anti-roll characteristic of the anti-roll bars will contribute less to the reduction of camber loss. Despite this, they will still load up the outside tyres like they did on the stock springs. The end result is that you could transfer weight too quickly to the outside tyres and cause them to lose traction.

This second characteristic of anti-roll bars is not necessarily a bad thing. By varying the side of the front or rear anti-roll bars, you can determine which end of your car will reach its traction limit first and thereby tune the understeer / oversteer balance of your car. However, putting a big front bar on a car that has inherent understeer problems (like many stiffly sprung B14 street cars) will only make things worse. By reducing the rate of (softening) or even completely removing the front anti-roll bar, you can make the weight transfer to the outside front tyre more gradual. By doing so, you don't make the tyre do as much work, which means it gives your car the front end traction to turn in properly.

That's the basic logic behind my recommendations. I hope I haven't confused you with my somewhat oversimplified explanation. And sorry about the edit. My bad.

I guess that makes sense, but seems like the stiffer it is the more it won't go to the outside of the tires.

Er... Hold on. I just read what I typed up there and noticed that I screwed up majorly in explaining what an anti-roll bar does. Let me fix that real quick.

Ok, sorry about that. Anyway, that isn't the case because stiffer springs and anti-roll bars do not reduce the amount of total weight transfer that occurs when you take a corner at a certain speed*.

The reason for that is that "weight transfer" isn't actually caused by the weight of the car shifting around. It's actually from the inertia of the car trying to go straight when you're asking it to turn. It's basically the amount of centripetal force the car needs to keep it on the road, by a factor of the CG location, and the track width. We just call it "weight transfer" because it's easier to think of it that way.

Say, for example, you have two identical Sentras, fit one of them with 500 lb-f/in springs (of the same length), and take the same corner at 25 mph. The car with the stiffer springs will exhibit less body roll than the one with the stock springs. However, both cars will actually experience the same amount of lateral weight transfer because the inertial forces are the same, they still weigh the same, have their same center of gravity in the same spot, and have the same track width.

Body roll and weight transfer aren't completely unrelated, but they don't always go hand in hand either. That's why a stiffer anti-roll bar makes the outside tyre work more, not less.

*I may have implied the exact opposite of this in my last post. That was a mistake on my part. Please see the corrections above.