Thread: Handling, Suspension and Brakes Thread - What is your chassis telling you?

Cross reference from @Shawn B to his thread B13-B14-B15-Suspension-Information

Twin-tube vs Monotube Dampers.

Disclaimer:
I am not responsible for what you choose to do with your car or how you wish to modify it. Take note when you lower the car, you are changing the geometry in the suspension from the OEM-level and all geometric angles should be considered when modifying a car.

Table of Contents:

I. B14, B15, B16, P11, A32 (and other beam-based chassis)

II. General Guidelines

III. Tire Pressure

IV. Camber

V. Toe

VI. Stabilizer bars or Anti-Sway Bars

VII. Bump Steer and Roll Steer

VIII. Brakes (under construction)

If you made this far, here is something very useful. Here is a wonderful file I discovered in my Dad's pile of racing archives. Many of these things are current and I find it highly informative and a great read. This should be a great read if you are having problems with your car and want to know why or if you wish to improve your chassis and want to formulate your own plan of attack. How to fix it is up to you, and I will not preach how to fix something that is very conditional.

Disclaimer:
Understand that these sheets are from a FR (front-engine, rear-drive car) therefore, the throttle applications do not apply. This is a guide to help you identify the problem in your chassis by various cause and effect examples. How you fix the problem is entirely up to you.

PDF Download: Suspension and Handling Tips

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TAGS: brakes handling chassis setup suspension pads wear worn struts shocks damper bump steer problems causes effects instability tires pedal stick stuck friction pads glazed surface rotors calipers brackets

B14, B15, P11, A32 (Rear Beam specific intel)

First, read this from Steve.

You need to be able to get the rear total toe to zero or slight toe-out.

Until this is done, you will be fighting the rear end the entire time. It is physics, sorry.

There is one thing you can do for free and that is disconnect and remove the front sway bar when you have a brand new, stock, un-modified rear beam on a new car.

I removed the one of the front end anti-sway bar links. The bar is still connected but I can remove it at any time. If I want to reconnect it, that is also easy. Have not done high speed work but for low speed, the car still understeers with my current suspension. (B14 Hyper co springs that are 300 lb/in Front and 250 lb/in Rear with KYB AGX set at 3 front and 6 rear and tire pressures at 34 PSI Front and 30 PSI rear)


It broke but it does not matter. The car handles better than ever and I should have done this years ago.

Try to gain negative camber for the front as much as possible. I do not know the P-series camber curve or B-series camber curve but the slightly gain negative camber and then the camber goes positive when being compressed. Use this knowledge to help setup your car.



*** Please do not get stiffer front end sway bars and front strut tower braces with the rear beam stock, you are stiffening the wrong end of the car and for handling purposes, increasing the effects of under steer. Focus your efforts on stiffening the rear or loosening the front ends.*** ***The above comment is for daily drivers, low-speed handling. High speed handling changes a lot of things and a larger front bar is often used to further stabilize the car in a high-speed corner.

You can stiffen and loosen an end with a virtual plethora of options via tire pressures, bushing change in material or just freshening a worn out OEM bushing with a new OEM bushing, springs, damper settings, braces, reinforcement bars etc...


Please Note:
When you loosen the front in the manner I did, by removing the sway-bar link, this does other things that negatively affect performance. Straight line accel is hurt because the tires contour to more road surfaces rather than held in a mostly solid place. Braking is negatively affected because, once again, the tires are contouring to the road rather than being held in place. Wet and snow weather becomes more annoying since the wheels are more likely to slip while accel and decel. But cornering is better. Just more proof to the whole "nothing is free" when it comes to cars.

General Guidelines

If the front end is pushing, aka under steer, here are some options you have.

--Stiffen the rear end by any means.**
--Loosen the front end (by any safe means)**

**This includes bushings, reinforcement bars connecting suspension parts to the chassis, anti-roll bars, shock and strut tower braces, stiffer springs, stiffer dampers and all converse parts being used to help tune the car chassis to whatever you want.



Now, with everything on a car, we can overdo things. It is possible. In fact, it is more likely to happen on the B13 and P10 because they are graced with IRS (Independent Rear Suspension) and they were created back in a day where Nissan cared somewhat about what cars they produced. Point being, if you throw a big bar on one of these chassis and get the perfect storm of over-stiffening the rear end, you will create a snappy, un-fun, and downright dangerous drift-mobile out of your FF Nissan. Something, I try to avoid at all costs since that just means I am going slower than possible.


To combat this terminal under steer characteristic, you can use a larger rear anti-sway bar, stiffer damper, stiffer springs, stiffer or refreshed new OEM bushings, etc... to stiffen the rear end which will help the chassis rotate better.

Tire Pressures
This is important because it influences the characteristics of the tires during heat cycling and also what parts of the tire are going to be in contact with the road. Pressure also will influence the shape of the tire and you can enhance or reduce your grip on whatever end you want by adjusting the tire pressure. Check your OEM tire pressure via the Field Service Manual or the little sticker in your door or coin box area by your elbow on some cars and adjust from there.

For my B14, I can cause the rear end to be more likely to break loose by increasing the tire pressures and making them higher or equal with the front tires. Although it can make the car rotate better, it is not a good option because I am reducing my possible tire grip. I am making something better at the cost of something else.

Camber
The higher the negative camber, the more firmly the car will be in contact with the road when cornering, but tire contact will be reduced when traveling in a straight line, which will reduce the car's ability to accelerate and brake.

Try to gain negative camber for the front as much as possible. I do not know the P-series camber curve or B-series camber curve but the struts in a B13/B14/B15 slightly gain negative camber and then the camber goes positive when being compressed. That is the downside of a strut-based suspension. Use this knowledge to help setup your car. (P-series suspension cannot utilize camber plates, please see strut vs shock based suspension technologies)

Camber plates can allow increase in camber in most strut-based suspensions. Camber bolts or crash bolts can be used as well.

For the P10 and P11 front, the Upper Control Arms or the UCA bearings are the focus point to achieve more negative camber.

Toe
Control your toe-angles! Toe will eat a brand new tire very quickly when it is out of spec. Toe-angles change in the suspension curve depending upon what type of suspension is being used. A slightly increasing toe-out angle will help the FF chassis rotate better while providing good in-line stability. Toe-in will cause under steer and make the FF rotate poorly. (this is why OEM chooses to install more toe-in on your FF cars from the factory, because accident protection is better than accident avoidance for some odd reason the Federal Government decided)

Toe-in is when the leading edge of the tires is closer to the center of the car in comparison the the trailing edge of the tire. Visualize this, take your hand and point your fingers away form you in such a way that a foot in front of you the lines from your hands would intersect ahead of you. That is toe-in. The opposite for toe-out. If you wish to use my visual experience again, make the palm of your hands closer together in such a way that they would intersect behind you.

Stock, your car all have toe-in front and rear to promote under steer. The front is easy to adjust via tie rods. The rear is specific for each platform, IRS vs Beam. Beam is set as it lies unless it is a modified beam with shims to adjust for camber and toe or a bent beam that has the toe modified, but no camber control.

Stabilizer bars or anti-sway bars

B13 FRONT stabilizer bar diameter = 28.6mm (GA16DE powered Sentra) and 28mm (SE-R model)
B13 REAR stab. bar diameter = 10mm (almost all Sentras) and 15mm (SE-R)

B14 FRONT stabilizer bar diameter = 25.4mm Front (Optional on 200SX SE and standard on 200SX SE-R, Sentra SE and SE-L)

P10 FRONT stabilizer bar diameter = 19mm on all USDM models
P10 REAR stab. bar diameter = 16.5mm, 17mm and 18mm. The changed it throughout the years.

For P11 and B15, Nissan chose to not list the diameter but if anyone knows they have an OEM bar, please measure it a few times to check for consistency and let me know.

Just from raiding OEM parts, a B13 owner can improve his car by using a B14 bar since it is smaller. This enables a small adjustment to be made and would promote a correct handling outcome for the B13 owner and the B14 owner benefits because his car no longer has a bar to stifle the handling.

Now, removing a bar on the front of a strut-based, FF chassis can cause harm. Wheel hop will be increased but since the whole idea is to gain more grip out of the car, simply let off the throttle and problem is solved. Technically, the owner's manual also states do not spin the tires for excessive periods of time over 35 MPH but none of us listen to that silly clause!

It is inherit of most modern FF (front-engine front-wheel drive) chassis' to under steer. The front end plows forward with great persuasion and when you try to turn the wheel tighter or accelerate quicker through a turn, it exaggerates the problem. Over steer is when the read end of the car rotates faster than the front and begins to slide. A nice audio indication of what tire/s are slipping is to tactfully listen while in a corner in a "faster than normal" speed.

These bars are a torsional spring that is used to attach the suspension component to the chassis. To increase the rigidity you can increase bar diameter, replace bushings with stiffer ones, stiffen the end-links or shorten the length of bar attached at its end links while maintaining proper angles. Reduce rigidity with converse conditions.

The anti-sway bar is to reduce the amount of body roll during suspension compression. You can easily over-bar or under-bar your vehicle and it will harm how it handles if a balance is not struck between the two bars.

A stock B14 will handle better with the front bar removed and running with no bars makes the chassis handle better. If I take this same attack and remove the front bar on a B13 or P10 with the Independent Rear Suspension, they will probably spin circles and over steer heavily since they are relatively close to neutral handling anyway! The largest problem with removing these bars is that Nissan stopped placing traction bars on cars and began to use the sway bar as a traction bar and the sway bars now perform two functions regardless of the detriment on each (with removal or installation).

Bump steer
Bump steer is very present on the Sentras. I have not encounter much on a P-series but I have little time in that chassis. The second you begin to lower a car bump steer increases a lot. Bump steer can be removed by relocating the steering tie rods location to where they would mount on the knuckle. They are mounted on the top of the eye-let @ factory position. When you lower the chassis, take the tie rods lower as well to counter the effects of bump steer.

The whole point to reduce bump steer is try to maintain proper geometry throughout the entire swing of the suspension during travel arc. Keep the tie-rod parallel to the LCA and reduce bump steer.

Some have made bump-steer kits but those are for very serious lowering of a vehicle. Use at your own caution.

Roll steer
Roll steer is another effect from when the two wheels are traveling in opposite motions of suspension travel. (Opposite of bump steer, when both left and right sides are compressed and the suspension begins to toe in other directions than when on level un-loaded ground) In other words, when one side is compressing, the other is rebounding. This will usually create a "toe-in" and "toe-out" scenario which when the two angles become enough, roll steer is felt.

So in a nutshell when lowering the car one should place the outter tie rod from bottom to top with the nut and pin facing up? I ask cause now my car has play in the steering and gets road feedback to the steering wheel like if the road had deep channels. it feels as if the outer rods are shifting

Brakes

Here is a great article on brake fade, properties of it, various ways to fix it, etc....

http://www.longacreracing.com/articles/text/Brake_Fade.pdf
***courtesy of Wilwood Engineering, a leader in high performance disc brake technology. Interested parties can obtain more information at the company's website. [url]www.wilwood.com[/url] ***

Pad material choice is important. Too soft, it will not bite, too hard and it will make murderous noises when you are daily-driving say a race pad that will never get up to its key operating temperature.

Brake fluid is an important choice as well. Fluid is meant to avoid moisture to be able to effectively conduct heat out of the system while maintaining proper pressure in the system. Once fluid boils, that fluid is done and should be discarded and replaced.

Rotor size impacts the amount of torque applied to stop the car and as well as cooling abilities. Larger ones more efficiently take on thermal transfer, give a larger sweep area for the pad to both grip onto and give a larger amount of time for the rotor surface to cool before rotating back around to the pad again.