The many effects to suspension write-up

Discussion in 'XII Performance' started by BondXII, Aug 1, 2013.

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  1. BondXII

    BondXII Well-Known Member

    Feb 2, 2009
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    Suspension explained....

    There have been questions floating around based on what a suspension does and how it reacts to certain components installed. The simple explanation to a suspension is that it keeps your vehicle "suspended." It also controls handling, ride quality, and ride height.

    The main thing to know about the OEM suspension of an X-Runner is that it is all made of metal. Spring steel is a magical thing that compresses and rebounds time and time again as you drive down the road, drag race, autocross, road race, or anything along the way. Unfortunately, spring still just another steel. Over time, this steel becomes fatigued and does not perform as it once did when it was fresh off the shelf. This causes a number of issues. Most of which are minor in nature and are by no means "unsafe" but are still an issue if some kind. These consist of, but not limited to, decreased ride quality, decrease handling performance, and decreased ride height.

    When I speak of "fatigue," I am not referring to the fatigue or endurance limit. That type of fatigue is just before catastrophic failure. What I'm referring to is the time frame in a suspension's life when it is just worn out or not performing as it did off the show room floor. Commonly known among mechanics as the suspension getting "tired." A surprising number of people will get this confused for worn shocks. This may be part of the issue, but usually not the only issue. Generally, people will get all of their shocks changed and they feel as if it rides as good as new. This is true to a point. It is a lot better, but not "like new" since people are still riding on their tired springs.

    There are so many variables to list, we could be here for days discussing the reasoning for fatigue and/or changes in ride height. The most important thing to realize is that no two vehicles sit the same. No matter how many times it is manufactured, there is always something different from the rest. All manufactures have tolerances, but that's just what they are...tolerances. This allows for a fudge factor so that it will pass quality assurance inspections before being released for sale. Even Ferrari has a 3mm standard on the chassis. Of course, there entire suspension is completely adjustable, so any differences can be adjusted after assembly. Any aftermarket part that is placed on a vehicle will give a different result depending on the vehicle. In the best scenario a company can produce, they base their advertised results from that case. If you buy a speaker that is a 1000 watt subwoofer, it only had to produce that volume for a required amount of time to be considered. Usually less than a second. Even when you buy a matching amp (which you should anyway), it is advertised a a certain wattage, but the consumer will never see it that high. They would normally not realize as they are happy with the windows flexing, the mirrors shaking where you can see, and the sound ordnance tickets they get from the cops. Horsepower gains is another example of this. A product claims to gain "up to" a certain horsepower in your vehicle, but the chances of you seeing those results are slim. There are the rare occasions where they may even see higher numbers than advertised, but most will "almost" see the gains advertised. This is no exception when it comes to the suspension after market as well. No matter how well the product is manufactured, the results will vary on every vehicle. When you have an easy "part swap" product, no two vehicles will react the same. It may be close from one to the next, but still not exact. The only way to get repeated results that are the same, there needs to be adjustability. Coilovers are a great example of this. If you take a coilover and set it, put it on the vehicle, measure it, and put it on another vehicle that is the same...the results will be different. The benefit to the coilover is that this difference can be adjusted so that both vehicles are at the same height.

    Just to list a few reasons for ride height differences:

    - How the vehicles comes off the assembly line?
    * As mentioned already, manufacturing tolerances will have each vehicle a little different than the next. This is usually not noticed until you are looking for it, or are comparing it to another "identical" vehicle.

    - If still running stock wheels and tires, or have gone aftermarket?
    * Even wheel manufactures are different. Some wheels will have the tires seat differently than the next. This may make the tire wider or more narrow on the rim. This will cause the tire to change its diameter as well. If the tire sits wider on the wheel, the tire will have a shorter diameter, and vice versa.

    - If tires are what came on the vehicle, or if they are a different brand?
    * Every tire manufacture makes there measurements a little different than the next. A 255-45-R18 tire may be taller or shorter sitting next to another brand of the same size. This is usually in the millimeters of difference, but still makes a difference.

    - Are the tires new, or if the tread is worn down?
    * Some people may not consider this one, but it makes quite the difference, especially if you are running on homemade slicks. Tread depth on the stock Bridgestone tires that come on the X-Runner is 10/32". If you have worn them down to an unsafe condition (no tread)...that's 5/8" off of the stock diameter of your tire.

    - Did the vehicle just come off the delivery truck, or are there some miles on it?
    * As mentioned earlier, the more the suspension is used, the weaker the metal gets and "tires" the springs. This happens slowly over time, so you will not wake up one morning and wonder why your vehicle is "laying frame" all of the sudden. This can be as much as an inch in worse cases, if there are enough miles on the vehicle. In the older Vee-Dub world, the Beetles are known to have the ass dragging syndrome and look like they have been lowered only in the rear. This is such a common problem with these vehicles that companies sell just a front lowering kit to level it back out from the sagging rear. This happens to many different vehicles you often will see running around. When was the last time you have seen a stock CJ, YJ, or 4-Runner driving around that the rear was not sagging?

    - Have you replaced all of your old parts, or just some?
    * With the aged parts I have just mentioned from milage, this makes sense as well. For example, if you buy an "entry level" drop kit such as our Street Drop Kit, you are replacing the tired coils in the front with some new ones. What are you doing in the rear though? You are putting drop blocks on tired leaf springs. You may be getting the drop that you are supposed to be in the front, but are lower in the rear than you should be as you are 2" lower from the blocks followed by further "drop" from your leaf springs sagging.

    - Are you completely stock, or do you have a lot of parts added to weight it down?
    * There are a number of aftermarket parts out there that are additional and not just replacement parts. With additional parts, there is additional weight. With additional weight, there is additional payload. This causes the vehicle to sit lower in either the front or rear. Stereo systems, tonneau covers, supercharges, turbochargers, carbon fiber accessories, changes to interior...and so on. Even the difference in an empty to a full tank of gas makes a considerable difference in ride height.

    - Is it a new vehicle or is it older?
    * With high mileage, there is also just plain age. You may baby your vehicle and not put miles in it. Over time, even if the suspension is not being exercised, the coils and leaf springs are still doing work. The metal is constantly in a strain supporting the weight of the vehicle. Over time this will weaken these parts as well and cause the vehicle to lower. Not exercising the suspension can also cause "memory." If it stays in one position for too long, when it comes time to do its intended purpose, it will have lost its memory and not function the same. One way to visualize this is for the fishermen (and fisherwomen) out there. If you have a reel of monofilament line and have not used it in some time, it has memory now. When you cast, it looks like a slinky coming out of the reel and does not perform like it did fresh out of box.

    - What is the climate like where you live?
    * It's amazing where dirt is found over the years that has slowly begun to weight your vehicle down.

    - How has the vehicle been treated over the years?
    * Even if you do not drive your vehicle that often, if you are abusive to it when you do drive it, it will shorten the life of the suspension and cause it to lower itself over time...along with the rest of the vehicle prematurely breaking down.

    - Has it been in an accident?
    * This may be a more obvious reason, but if your vehicle ha been in an accident, it will not sit properly and ride height will be affected. Even if it is fixed professionally, it will not be 100% ever again and ride height will be different.

    - Is the vehicle raced often, or is it daily driven, or is it a Sunday cruiser?
    * This kinda coincides with the abusive driving. If your vehicle is raced often or is a daily driver for you, it will sit lower than one with less miles like the Sunday cruiser. This is relative to the age of the vehicle though, as I have mentioned that over time the suspension will begin to sag whether it is driven or not...just possibly not as much.


    For a little visual assistance, this ruff diagram shows the relation between the front and rear of the vehicle. The comparisons are slightly exaggerated for a better visual. The first (1) is the ideal situation where front and rear are sitting level. Next (2), is from sagging leaf springs or added weight in the rear. If you look at the arrowed line, you will see that the front is pointing up higher than in (1). In situation (3) you see the front sitting lower than in (1). This would be from sagging coils or added weight in the front (supercharger, turbocharger, push bar, winch, etc.). As you can see in these situations, that front (2) or rear (3) tires are a pivot point if the opposing end is the issue. This is why you may have the distance from the ground to the top of the wheel well, but the bumper sits higher. This is from the pivot affect in the front or rear.

    There are a few methods to correct situation (2). The least expensive method is by purchasing a shorter drop block. This will level the vehicle back from having a negative "rake". This may not be ideal as most people that are lowering their vehicle do not want to raise it back up to fix an issue. Another way is to purchase new OEM leaf springs. Another method is to purchase an upgrade to the suspension and get the drop leaf springs that compliment the front suspension upgrade. With all of these remedies, the bottom line is to raise the rear to "lower" the front.

    All of these situations are possible, no matter what company you get a drop kit from. The reasons still apply whether you are dropped with coils, spring perches, or control arms. Age, mileage, parts, and everything else mentioned in this write-up play in the way your vehicle will.

    With all of this being said, there has been a small debate on how an X-Runner should sit with a XII Performance L.L.C. Drop kit. Going back to the "ideal" situation I mentioned early on, when the drop coils were originally designed, it was based on 31" from the ground to the center of the front fender. This would make a goal height of approximately 29 1/4" from the ground to center if the front fender. Due to the numerous things that has been discussed in this write-up, we have seen this dimension at 29 1/4" as well as down to 29" and up to 29 1/2" (even one that was 29 9/16 on one side). Unfortunately, this R&D was done on the "1st Gen" X-Runner. This isn't official on the generation thing. Just consider the 1st Gen being '05-'08, then '09-'12 the next after the motor and ECU changed making URD sad that they have not had a plug-n-play harness yet, to now the latest version where they changed the front end completely. Why is this unfortunate? There were not pictures taken back then for the height, and the new front end may cause a different height in the front and would not be a valid measurement. The OEM suspension has been exactly the same for the entire time that the X-Runner has been produced though from 2005 all the way to the present version of the X-Runner. The bottom line to this, is if you are sitting approximately 29 1/4" inches, you have achieved the "advertised" drop in the front based on a brand new, zero miles, 2005-2008 Toyota Tacoma X-Runner originally sitting at 31".

    We hope this clarifies any questions that you may have, and we do apologize if there is anything that you feel you did not achieve.

    Stay tuned for new a improved products from XII Performance L.L.C., as we are always researching, developing, and producing products to make your X-Runner handle as good and better than the team at TRD originally intended.

    Track Inspired...
    Track Developed...
    Track Proven...
    XII Performance L.L.C.
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