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Thread: So I'm oficially in desperate need of some suspension advice.

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Posts: 11-20 of 44
2008-12-01 05:24:32
#11
Originally Posted by BenFenner
How bad is the understeer during transitions? You say it shows understeer during long sweepers for the most part?

During transitions, it's not all that bad. Although, I have no power steering, sometimes it's hard to get the car in the direction I want it to go. I'll put it this way. If I go to make a hard left or hard right, I feel like I have to turn the wheel more than I should have to turn it.

During long sweeps, it's almost scary. Imagine a sharp exit ramp. Most of us would do a typical exit ramp at about 80, before I could do that, too. If I did 80, now, you'd be seeing my car in the local paper.

Before I go on, just some more info. The handling changed drastically since the swap, but a lot of changes happened during the swap as well. I removed the strut bar, I removed the power steering, I removed a lot of weight from the front wheels. My wheels are bigger in diameter and I am running 10mm spacers in front (both wheel size and spacers were to clear the front brakes). I changed out all the bushings and wheel bearings. I raised the ride height to nearly stock because of the wheel size.

Originally Posted by wildmane
Since shocks and struts wear slowly overtime and not immediately/quickly then it's kinda hard to say if your ****ty k-sports are performing like new. I'd attribute at least a good bit of your issue with your coilovers. Also, how fresh and worn are your tires? You're not still using 15" wheels, correct? Tires with thin side walls won't be able to absorb as much of the road, I bet with your current tires, tire size, and ****ty (don't take it as an insult, K-sports really aren't that great at all) suspension, every little undulation in the road is going to be magnified, and your tires are fighting to keep what little grip they already had.

I know I'm probably going to get a lot of input on the K-sports. I won't argue, it could be partly to blame, but not to this extent. Wear seems very unlikely as well, I mean, this is night and day and it only started after the swap. There is no visible damage to the shocks and they're still practically new.

Tires. I bought the Azenis new. They're 225/50/17 and I'm running that size only because of my brakes, I seriously cannot go any smaller. I did choose tires with a lot of sidewall, I could've probably done 225/45 or 225/40, but I figured low-pros would handle and ride like sh{t.

Another thing you could take into consideration is the fact that the engine, while not necessarily heavier than any other comparative setup, may be placing more weight towards the front of the car. SR20DET and SR20VE engines were designed for mostly similar chassis to the B14, and if not for all intents and purposes, the same chassis.
Placement of weight is a huge factor in the way a car will handle.

I agree, and I thought of this many times, but you have to consider, the weight is no more forward the front axle than the SR, not to mention look where the turbo, IC, and pipes go, they're way out in front of the front axle.

Originally Posted by billc
Determining your corner weights might be a starting point for an objective discussion.

Is there any place I can go to get corner weights? I'm sure I can find a place that can do the entire car, or front to back. This is a good point and I'm not trying to nullify this argument, but I seriously can't imagine my F/R balance being more than a bone stock Sentra, if anything, I'd imagine it being less. Anyhow, I will try to get some figures.

Originally Posted by Shawn
Do you have an aftermarket Rear Sway Bar?
Is the Bolt-In-Bars RSTB the three-point version or two-point?
Do you have an IKEA brace?
I have an extremely limited veiwpoint on diagnosing an actual suspension problem. However, assuming everything else is in fact operating correctly, those items would all contribute to less understeer. And you do not appear to have them.
I have a Progressive Suspension Rear sway bar and it's set at the highest stiffness.
I wasn't aware of a 3-point Bolt-in-Bars rear brace for the B14, I have a 2 point.
I never did the IKEA brace, but I could possible fab something up, if I had to.

Originally Posted by Old
The most important thing that you can do to improve B14 handling is to get the rear axle bent to zero toe in.
I have a bottle jack . Naw, I want to do it bad, but I would need someone like Steve.
Originally Posted by Old
If you take the same amount of weight and move it further from the center of the car (towards the front, for example) you increase the polar moment of inertia and make it more difficult to rotate the mass of the car. If you move the weight toward the center, just the opposite occurs. That is the principle behind mid-engine cars.
Trust me, I know this better than most. I didn't get a degree in Mechanical Engineering for nothin'

Originally Posted by Old
Also, even though the V6 may weigh the same, chances are that the weight is more concentrated toward the top than in the SR engine. This will raise the center of gravity at the front of the car. This increases the weight transfer in the corners and puts more load on the outside tire. You might need to make your own rear sway bar, stiffer than the ones you can buy.
Very possible. I've been looking at this in terms of weight behind/in front of the front axle, but it is very possible the VQ is very top heavy, considering I have 2 heads and 2 sets of cams.

How would I go about making my own sway bar? Just weld a thick steel bar to the swing arms? I'm not an expert on suspension design, But my worst fear would be me making things worse, my second fear is that steel rod buckling.
2008-12-01 06:04:48
#12
suspension recap:
Major front weight reduction. Still got dash, no airbags, no AC, no PS:


Ksport coilovers:


Spacers all around, BABK all around:


Lots of Polyurethane:


225/50-17:


Progressive Sway Bar:


rear strut bar (PS, I REMOVED ALL THAT DYNAMAT):


no IKEA brace:


rear Battery:
2008-12-01 07:32:46
#13
Try lowering the front a little bit, or adding more negative camber. You might have shifted/lost so much weight up front that you might have lost some negative camber.

What is your suspension aligned to?
2008-12-02 00:12:07
#14
Originally Posted by mafoose
Try lowering the front a little bit, or adding more negative camber. You might have shifted/lost so much weight up front that you might have lost some negative camber.

What is your suspension aligned to?


If I lower the front any more, I will be rubbing the fenders. The only way I could is if I move to a skinnier tire, such as 215/40.


I might try the neg camber (poor tires)

A few other things I want to try is softening the struts just a touch and possibly a FSTB, Although the last thing I need is stiffening the front, it might help with my sloppy steering response), and of course, bend the rear axle to 0 toe. I'm starting to really believe, now, that we've nailed the bigger issue: the front end is too top heavy.

Oh, PS: The suspension was aligned to near stock specs. I'll have to get an alignment kit myself, if I move the camber in, I'm going to also get toe-in, which will make the situation worse.
2008-12-02 01:53:24
#15
Originally Posted by Shawn
I'm just looking at your suspension modifications alone.

Do you have an aftermarket Rear Sway Bar?

Is the Bolt-In-Bars RSTB the three-point version or two-point?

Do you have an IKEA brace?

I have an extremely limited veiwpoint on diagnosing an actual suspension problem. However, assuming everything else is in fact operating correctly, those items would all contribute to less understeer. And you do not appear to have them.

Now I shall sit back, read, and listen. I like suspension-savvy dudes discussing suspension issues and problems. Go figure.


Get out the Shawn B suspension flow chart. Consult Mike Kojima suspension flow chart as needed.
2008-12-02 17:17:45
#16
Originally Posted by Ninety-9
Is there any place I can go to get corner weights? I'm sure I can find a place that can do the entire car, or front to back. This is a good point and I'm not trying to nullify this argument, but I seriously can't imagine my F/R balance being more than a bone stock Sentra, if anything, I'd imagine it being less. Anyhow, I will try to get some figures


Second the corner weighting. In fact, I would do this first before you bolt anything else to the car. Between the drastic ride height change and weight relocation you've shifted the weight distribution of the car all over the place. No amount of band-aid fixes will fix that.

Any shop that does racecar prep will have corner weighting scales. Whereabouts are you?
2008-12-02 17:39:34
#17
There's a million things we could discuss about making the car handle better. First off would be the rear beam bend. But the fact is you said the car handled terrific before the swap, and now it's not good anymore. You said you changed some suspension stuff, but nothing really important and mainly we're talking about the engine swap and other weight related things.

I'm going to go out on a limb here and say you've lightened the front too much, and while I think it's possible the higher (assumed) center of gravity on the V6 might be playing a role, I think it's the weight in general that's playing the biggest part. All things being equal, if you remove weight on a front tire during a corner it will tend to "push" and push a lot. A lot of the time the best thing you can do for this is to add weight to the front of the car. I won't get into the details of examples, but I think by removing a lot of weight from the front of the car, and moving some of it to the back (battery) you've given the front tires nothing to work with in a corner.

I think packing the engine bay with jugs and bottles of water might be a good test.

Once again I guess we're back to corner weighting...
2008-12-02 18:03:23
#18
Originally Posted by BenFenner


I'm going to go out on a limb here and say you've lightened the front too much
, and while I think it's possible the higher (assumed) center of gravity on the V6 might be playing a role, I think it's the weight in general that's playing the biggest part. All things being equal, if you remove weight on a front tire during a corner it will tend to "push" and push a lot. A lot of the time the best thing you can do for this is to add weight to the front of the car. I won't get into the details of examples, but I think by removing a lot of weight from the front of the car, and moving some of it to the back (battery) you've given the front tires nothing to work with in a corner.

I think packing the engine bay with jugs and bottles of water might be a good test.

Once again I guess we're back to corner weighting...


I have to agree with this. this is the only thing I can think of too.
2008-12-02 22:54:39
#19
One thing that i noticed that made a decent difference was lowering the rear just a tad bit. Measure from the rockers to the ground just behind the front tire and just in front of the rear tire and make sure they are within a 1/2" or so. My rear was about 1-1-1/4" higher and after lowering it to 1/4-1/2" it really made a big difference.

Also try some more negative camber about 1 to 1.5* and 0 toe in front. You could also try getting some caster bushings for the front control arms.

Have you tried adjusting the rear sway? that might help a little too.
2008-12-02 23:23:22
#20
I forgot to mention that quick transitions will put weight on the front tires which will allow them to grip. While long, sweeping corners will really show the lack of weight on the front as the car settles in.
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