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Thread: B13, B14, B15 Suspension Information...

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Posts: 71-80 of 162
2010-10-02 05:39:50
#71
Thought I'd recently seen this elsewhere -

The Ultimate Handling Guide Part V: The One Unforgivable Sin, Overlowering Your Car

Originally Posted by MikeK
A Sentra SE-R is a typical example of a car that should not be lowered more than an inch. It can be lowered more than that but its suspension design isn't happy about it. This situation is common on many cars and not just indicative of the SE-R’s design, we have just thoroughly studied this car's geometry because we race one.

The first problem with lowering the SE-R (and most McPherson strut equipped cars) is that it only has about 2” of jounce travel at stock ride height in the front suspension. Let's say you lower the car the typical 1.5”, you are left with only about .5” before you hit the bump stops. Your typical aftermarket lowering springs only up the spring rate a paltry 20% or so, not enough to keep the car off the bumpstops with only 0.50” of travel.

Not only does this ride poorly, bottoming out frequently and all the time if carrying passengers, but in a corner, when the car leans over, the suspension will quickly settle on the bump stop causing the spring rate to rapidly ramp up approaching infinity quickly as the bump stop smushes down. This causes huge amounts of weight transfer and a build up of slip angle in the outside front tire suddenly resulting in relentless understeer. When the car initially hits the bumpstop, the perceived increase in stiffness makes the car feel responsive, sort of like a go kart but this snappyness in steering response turns into inescapable understeer in a few milliseconds after turn in is initiated.


Mike nailed that one, as usual. Virtually all my front suspension changes are aimed squarely at avoiding these issues. Dave C did a nice writeup when he first went to CO's on the car back in July 2000:

SCC July 2000 Suspension Magic



Not to say we don't have some options today that he didn't have and may have used at the time, but based on the car's handling today he hit most of the issues dead-on. Since that article the CO's went to Progress, w/350F/250R, I found that a little soft for my use, bumped up to new Progress CO's set up with the right damping for 450/350 springs. Also the rear sway is 3-hole adj Progress, not ST. I've added more chassis reinforcements, dialed in a zero toe rear + minimal toe front performance alignment*, but that's about it.

* Note I do NOT recommend this alignment for general street use unless you are really comfortable with how the B13 reacts at or slightly over its limits, it removes most of the safety margin for avoiding snap oversteer - but the gain in control is worth it for braking-induced oversteer. It will make the car fairly sensitive to road imperfections, easier to spin in the wet, and definitely is a "two-hand" driven car
2010-10-02 05:45:53
#72
Originally Posted by vqman
where do you buy your koni yellows??

I went to Summit racing and they had koni yellows listed for B15's as if there was no difference between Spec V housing/insert compared to an LE B15..

I always thought you HAD to specify B15 Spec V yellow insert to get the right ones.. ugh I can't believe how many write ups there are on this and how unclear it still is.


Check with Wes D - he did an excellent write-up on this recently and I think MotoIQ posted it. If not, I believe it can be found on the "other" forum, too.

HTH - I agree it's pretty unclear, you'd think someone would have listed the Koni part #'s exactly and made it easier. Essentially that's what SHig did when building my CO's on my second B13, put Koni DA fronts (8211/8212?), SA rears into a CO body of his own design. Those are some exceptional CO's...but not available, and when they were, 3x the cost of inserts in stock bodies. They cost as much new as I paid for that entire car.
2010-10-02 06:05:36
#73
Wes with the turbo ga16 200SX?

it may have just been that website that had me for a loop..
2010-10-03 18:58:32
#74
I have begun looking at rear sway bars to combat the massive understeer of the B14. I have been around here for a while. I have seen parts come and go. I need you guys to help me find more choices for a rear sway bar with PICTURES. (Key is PICTURES of them installed on the car or how they connect the bar to the beam to the chassis itself)

Everyone swears by Progress. I found install instructions for the Progress and for the Whiteline Automotive rear sway bars so far with good pictures to help me identify where/how these bars connect the rear. This is important in reducing the amount of roll.

From the instructions, the Whiteline unit appears better and it accomplishes the task of an anti-roll bar much better than the Progress unit.

Progress on a rear B14 connects at the trailing arm at two spots on each of the trailing arms of the rear beam. It reinforces the rear beam utilizing the stock mounting points for the rear trailing arms to the chassis. Maybe they designed it this way because the beam itself, is fairly rigid. I want a proper sway bar that connect the suspension components to the chassis.

The Whiteline unit includes new brackets to mount onto your car that actually connect the sway bar to the beam and then to the chassis. It connects the suspension parts to the chassis.

Whiteline unit is 20mm and Progress is 27mm. These are more factors that change dynamics of how the bar handle roll. If the car still understeers, than I will try to bend the beam.

EDIT: I am trying to find installed pics or install instructions of the Suspension Techniques bar. I know they still make this unit, I just cannot find pics of them.

Also, I just discovered that Progress, has, at one point or another TWO different rear bars for the B14 chassis. One of them is the one you find everywhere. Another one, however, actually looks proper and has mounting locations to the body and not just stiffening the beam itself. The models are 62.1510 for the current sway bar that has oddly-chosen mounting location. The one that I want more information on is 61.1510. It claims to be "for track use only, the kit uses Delrin pivot bushings and requires regular maintenance". Both are 27mm

Doing a Google search "progress 61.1510" yielded 9 results.

EDIT TWO: I decided after long discussion that I would shoot for the Progress bar. Anyone with a whiteline let me know your thoughts are about it.
2010-10-03 19:15:14
#75
Who cares how it looks, function over form!!
2010-10-03 19:19:26
#76
How it connects is what matters and what I mean by how it looks. Not, I like the pretty baby blue color over the green color, smart ass

Always function over form!
2010-10-03 21:10:50
#77


i know, reading the rest of your statement it's obvious you are concerned about function.

thicker is usually better unless the thicker one is made of inferior materials..
2010-10-04 02:17:37
#78
I decided to get the Progress rear bar, Bolt In Bars rear strut tower bar, and relocate the battery to the trunk. hahahahahha.
2010-10-04 05:25:46
#79
you should put the front springs in the rear brah!!!
2010-10-04 22:53:24
#80
Hey guys.... i wanna drop my NX, What all should i replace for stable support and everything? Ive read about the strut bars, and them not being able to handle the different angles and whatever... should i consider upgrading them?
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