Rear End Squat

[Edub1]

One of the first things I noticed after going turbo is that my rear end squats quite a bit when launching. Is there some type of traction bar that helps decrease this?

[yokota180sx]

coilovers will help of course. or really anything with a higher spring rate and dampning

[superDorifto]

like he said, some higher spring rates and better shocks will help, but the "squat" will never go away. The rear independant suspension has the unfortunate side effect of deflecting under a hard launch( thats why almost all drag cars use a live axle 4 link rear suspension). You could also try SPL for some anti squat bushings. Theyre made of urethaneand install almost like a set of collars to allow you to slightly adjust the rear anti squat geometry by changing the angle of the entire rear subframe by a few degrees. Ive also got a couple books lying around on chassis engineering i could dig up if you need any more info. Hope that helps.

[yokota180sx]

also called Pineapple poly bushings

[superDorifto]

what he said....oh, get better tires and the squat wont have as much an effect.

[nismofly]

you could also relocate your rear LCA mounts, but we wont go there cause its an interesting process

[Edub1]

Thanks guys. Can you tell me more about these bushings? Like where do they go?

I don't really want stiffer springs. Is it feasible to make a bar of some sort that can limit wheel travel or would that ruin the suspension functionality?

[superDorifto]

no....the squat is caused by a shift of wieght, and the complex way that all the components of your rear suspension interact together....there is no bar that you can make that will both make it stiff, and not ruin the harmony of the rear suspension. By using stiffer shocks, and stronger springs, you help to lessen the squat, but it will always be there. the bushings are installed like a set of subframe collars. look up "anti squat geometry" in google, an you should get an idea of why they work.

[nismofly]

would that ruin the suspension functionality?

it would

unless you never plan on turning, then youd be ok

but that might prove difficult

also it would give you basically infinite spring rates, so you might as well get coilovers, theyre worth it anyway

no....the squat is caused by a shift of wieght, and the complex way that all the components of your rear suspension interact together....there is no bar that you can make that will both make it stiff, and not ruin the harmony of the rear suspension. By using stiffer shocks, and stronger springs, you help to lessen the squat, but it will always be there. the bushings are installed like a set of subframe collars. look up "anti squat geometry" in google, an you should get an idea of why they work.

this is what i was talking about, theres a way to basically eliminate it by relocating LCA mounts, but im not going there because i havent read enough about it yet

ill probably be doing it to my car at some point, and thats when ill start to share info about how it works

[superDorifto]

I think, (key word here is think) that when moving the rear LCA, youre still just affecting the anti squat angle and scrub radius, but i cant remember right now...and it is officially time to start drinking on this most holy of holidays...Plus, im too lazy to go look up the answer in my books. I say that if you wanna build a 240 drag car, a swap to a ford 9" is mandatory, but that involves even more modification then just moving the LCA....

[nismofly]

nope, i hate drag racing with a passion, but putting together info for a road racer, i read something about moving the LCA

ill see if i can find it

[superDorifto]

id be interested...but even if you hate drag racing (I dont care for it much either) , you cant argue with a 4 link rear suspension. It works amazingly well if all you want to do is go in straight line.

[yokota180sx]

you gotta be kidding me let me fix your post

Thanks guys. Can you tell me more about these bushings? Like where do they go?

I don't really want stiffer springs, becuase i dont want to spend the money becuase im cheap and want to make things myself that will hinder my cars performance instead of buying something that will increase my cars performance in more than one area. Is it feasible to make a bar of some sort that can limit wheel travel or would that ruin the suspension functionality becuase i dont want to spend money the right way?

[Edub1]

Does any of this stuff help? Anybody have a good illustration of our rear suspension handy?

http://storesense.megawebserve...s.bok

[yokota180sx]

Does any of this stuff help? Anybody have a good illustration of our rear suspension handy?

http://storesense.megawebserve...s.bok

ok at this point im going to be a d!ck

Use the search button, not only on here, but on google, on yahoo, aol, altavista, whatever you can find.

Noone is going to spoon feed you pages of information, i know DA MN sure that i wont. I look hard for the information i post, and when people show that they have tried im more than happy to help. But obviously you spent more time making this post than you did typing 240sx anti squat in google.

if you did you would KNOW about hte subframe spacers, plus there is a tech article about them for gods sake.

you have 1500 posts and your asking dumb questions like this?

adn just becuase i can say itif you look above adn actually TRIED to find **** out for yourself. wow there is a suspension faq....who woulda thought

[Edub1]

Actually I spent a good amount of time searching & reading. What I found is that the system is complicated, I don't really have a complete picture of how it works and I didn't find much that offered a concise explaination. I certainly can't see how subframe bushings would make a big difference.

I'm not forcing you to answer my thread so you don't have anything constructive to add don't please don't feel obligated to do so.

[yokota180sx]

hey dumbassI said "Look above there is a suspension FAQ"

and guess what, it explains what all the **** you just asked abou does, and has a picture for your retarded ***.

I hate being a d!ck, but help yourself before askign for it

[AmoebAssassin]

like he said, some higher spring rates and better shocks will help, but the "squat" will never go away. The rear independant suspension has the unfortunate side effect of deflecting under a hard launch( thats why almost all drag cars use a live axle 4 link rear suspension). You could also try SPL for some anti squat bushings. Theyre made of urethaneand install almost like a set of collars to allow you to slightly adjust the rear anti squat geometry by changing the angle of the entire rear subframe by a few degrees. Ive also got a couple books lying around on chassis engineering i could dig up if you need any more info. Hope that helps.

Any sprung suspension without 100% geometric anti-squat will squat under acceleration. The advantage of live axle is not that it will squat less, but that it will not camber gain significantly in bump, and this will maximize contact patch area for more launch traction.

you could also relocate your rear LCA mounts, but we wont go there cause its an interesting process

****ty advice, this is way overkill for a street car, and most people don't know what they're doing well enough to set a proper anti-squat or anti-dive angle. His best bet if he wants to be super anal would be coilovers. His 2nd best bet would be the SPL anti-squat spacers mentioned earlier in this thread.

Thanks guys. Can you tell me more about these bushings? Like where do they go?

I don't really want stiffer springs. Is it feasible to make a bar of some sort that can limit wheel travel or would that ruin the suspension functionality?

Any sort of bar limiting your stroke will ruin your suspension functionality. Bars that limit your stroke essentially produce infinite spring rates and while this is a great design for karts running on perfectly paved courses, you will suffer greatly on any sort of real world road surface.

this is what i was talking about, theres a way to basically eliminate it by relocating LCA mounts, but im not going there because i havent read enough about it yet

ill probably be doing it to my car at some point, and thats when ill start to share info about how it works

Raising the front of your rear LCA will give you more anti dive, but changing your a-arm angularity is a retarded idea when you can do it much more quickly with the SPL spacers. Also, there's no way to completely prevent squat without running 100% anti-squat geometry, and nobody does that because it's retarded. 100% anti-squat geometry will mean that 1) the angle between your suspension arms will be so great that your suspension will bind every time you load it, or 2) both of your a-arms will be perpendicular to the ground. Essentially, anti-squat is a way of adjusting the the ratio of geometric (through suspension members) to elastic (through the springs and dampers) front-rear load transfer. Some is a good thing for track cars, too much is catastrophic and either leaves you with binding suspension or a car with infinite rear spring rates and no damping.

I think, (key word here is think) that when moving the rear LCA, youre still just affecting the anti squat angle and scrub radius, but i cant remember right now...and it is officially time to start drinking on this most holy of holidays...Plus, im too lazy to go look up the answer in my books. I say that if you wanna build a 240 drag car, a swap to a ford 9" is mandatory, but that involves even more modification then just moving the LCA....

Changing your anti-squat percentage does not effect your scrub radius. Changing your offset and camber effects your rear scrub radius more than changing your anti-squat. Not to mention that rear scrub radius is a worthless measure unless you're calculating stresses in your rear suspension. Front scrub radius, however, is an indicator of self-centering torque on the steering wheel and steering effort, among other things.

you gotta be kidding me let me fix your post

Fabricating parts to alter your suspension is perfectly fine and legit if you know what you're doing. I plan on doing so in the future so that i can dump my car without ****ing up my roll centers, etc.

Actually I spent a good amount of time searching & reading. What I found is that the system is complicated, I don't really have a complete picture of how it works and I didn't find much that offered a concise explaination. I certainly can't see how subframe bushings would make a big difference.

I'm not forcing you to answer my thread so you don't have anything constructive to add don't please don't feel obligated to do so.

As suggested, please read up on anti-dive and anti-squat geometry on google, or read "Tune to Win" by Carol Smith.

[Edub1]

hey dumbassI said "Look above there is a suspension FAQ"

and guess what, it explains what all the **** you just asked abou does, and has a picture for your retarded ***.

I hate being a d!ck, but help yourself before askign for it

Moderator, please do something about this.

[yokota180sx]

im trying to help you, and your not listening.

Look im sorry, i got a little worked up for no reason

if you check the very top of the forum under the stickies, there is a suspension faq. It has diagrams, explanation of all the terms, and a HUGE amount of other information, i should have just spoon fed it to you instead of getting man.

my bad
Modified by yokota180sx at 9:26 PM 2/5/2007

[Edub1]

im trying to help you, and your not listening.

Look im sorry, i got a little worked up for no reason

if you check the very top of the forum under the stickies, there is a suspension faq. It has diagrams, explanation of all the terms, and a HUGE amount of other information, i should have just spoon fed it to you instead of getting man.

my bad

Modified by yokota180sx at 9:26 PM 2/5/2007

I appreciate the apology and I assure you I have poked around a bit. Unfortunatly I have not yet found many answers other than replacing subframe bushings or using stiffer springs. Our cars seem to have quite a complicated suspension and I'm sure it takes quite a bit of reading to fully understand the dynamics. I was hoping someone would know of a specific mod that might solve the proble. If there isn't one, I have no intention of trying to invent one so there isn't too much point in becoming a suspension expert.

That being said, I'd like to point out that I have contributed two articles to this forum including one on ECU tuning and I have helped numerous people with a variety of issues. I think my question is a valid one and I do not deserve to be spoken to in such a manner.

If you have a problem with my question, you don't need to respond to it. But, you certainly have no standing on which to lecture me, so I ask that you stop doing it and I am letting you know now that I will consider it harrassment should you chose to continue. I started this thread, if you don't like it don't post.

[yokota180sx]

i do not have a problem wiht your question, but your lack of self help

I call BS on the fact that you searchedOr even stray looked around

If you did, 60% of the questions you had asked, were located in the SUspension FAQ.

Dont try to bull**** a bull****ter

Just becuase you contributed two articles doesnt mean you dont have to search now, ive put in two articles as well. but it doesnt mean anything. That just means you should know that there is a wealth of information, and i know you didnt use it!

[SPIRONIUM]

Any sprung suspension without 100% geometric anti-squat will squat under acceleration. The advantage of live axle is not that it will squat less, but that it will not camber gain significantly in bump, and this will maximize contact patch area for more launch traction.

live axle CAN be setup for 100% anti squat, while the IRS can have a maximum of around ~20% of the anti squat characteristic that can be produced by a solid rear. This is the main benefit of a solid rear amongst the drawback of an insane amount of unsprung weight.

anyway back to non solid axle talk so we can relate to more people here:

It is my understanding that on our IRS setup, the most effective way to increase anti-squat would be to tilt the LCA mounting so that the rear mount on the subframe is lower and the front bolt location is higher. This would be IN ADDITION TO moving the traction link mount lower on the subframe (traction link right? the shorter one that is closer to the front of the car..)

can anyone else comment on this?

please no more pineapple bushing talk, i would like to find a way to create the most amount of antisquat while utilizing the stock setup.. The pineapple bushing is a solution for most, but since we have already covered this, i would like to go one step beyond before this thread is trashed.

[AmoebAssassin]

live axle CAN be setup for 100% anti squat, while the IRS can have a maximum of around ~20% of the anti squat characteristic that can be produced by a solid rear. This is the main benefit of a solid rear amongst the drawback of an insane amount of unsprung weight.

anyway back to non solid axle talk so we can relate to more people here:

It is my understanding that on our IRS setup, the most effective way to increase anti-squat would be to tilt the LCA mounting so that the rear mount on the subframe is lower and the front bolt location is higher. This would be IN ADDITION TO moving the traction link mount lower on the subframe (traction link right? the shorter one that is closer to the front of the car..)

can anyone else comment on this?

please no more pineapple bushing talk, i would like to find a way to create the most amount of antisquat while utilizing the stock setup.. The pineapple bushing is a solution for most, but since we have already covered this, i would like to go one step beyond before this thread is trashed.

I don't know who told you IRS can only achieve 20% anti-squat, because every vehicle dynamics text I've read has shown (and shown calculations) how to achieve 100% anti-squat on double wishbone and multi-link rear ends, and it is very achievable, although 100% anti-squat is COMPLETELY UNDESIRABLE as excess anti-squat leads to violent power-oversteer.

100% anti-squat means that NONE of the weight transfer rearward occurs elastically (through the springs), and ALL of the weight transfer rearward occurs geometrically (through suspension members), meaning you'd probably deflect stock RLCAs and RUCAs. Not only that, but once you start jacking up your anti-squat, you start running into binding and bearing misalignment issues.

To properly calculate the angles you need for proper anti-squat (about 10-15% on a 240sx), you need to know the exact location of your center of gravity. Since I'm guessing you don't know this, you'll probably have to cut and weld your RLCA mount points a number of times before you find the proper amount of anti-squat for your particular setup, but by the time you're done with all your cutting and welding, you've probably weakened your RLCA mount points significantly.

The pineapple busings allow the user to dial in anti-squat without compromising the strength of the subframe or RLCA mount points, and without cutting and welding -- and they do a damn fine job of it.

[SPIRONIUM]

I don't know who told you IRS can only achieve 20% anti-squat, because ...........

.......To properly calculate the angles you need for proper anti-squat (about 10-15% on a 240sx), you need to know the exact location of your center of gravity. Since I'm guessing you don't know this, you'll probably have to cut and weld your RLCA mount points a number of times before you find the proper amount of anti-squat for your particular setup, but by the time you're done with all your cutting and welding, you've probably weakened your RLCA mount points significantly.

The popular book Chassis Engineering by Herb something or other has this info, he stresses that 100% antisquat is impossible with IRS, it is more like ~20 COMPARED TO a good solid rear setup. The 100% of antisquat that is achievable on an IRS is the equivalent of ~20% of the antisquat achievable on a solid rear according to Herb..

I havnt heard anything about proper antisquat described as being undesireable because of violent oversteer.. Can you point me in the right direction for this info?

I am very comfortable fabricating, i have no problem making LCA brackets with multiple adjustment holes (if need be for testing) that will be significantly stronger than stock.

So does anybody have any comments on improving anti-squat on out IRS setup, a step beyond the pineapple bushings? Could moving the traction arm mount lower potentially also aid in positive anti-squat?

[Edub1]

I don't know that much about our rear suspension. By "pineapple bushings" are you reffering to the subframe bushings / spacers?

What exactely produces the squat other than flexing of the subframe? I'm wondering if there isn't some sort of brace that can be made.

I apologize if this sounds like a dumb idea and I remind those that have a problem with it that they are not required to reply.

[SPIRONIUM]

the pineapple bushings are the yellow guys that are used to tilt the subframe, spl parts has them for 50 bucks.

Squat is simply weight transfering to the back of the car on acceleration.. is this what u are asking? Now that your car is turbo, and u can accelerate faster, the weight transfer to the rear on a launch is greater

If you tilt the subframe with the bushings, it slightly changes the way the rear of the car deals with weight transfer, it will add a bit of anti-squat.

I would imagine that these bushings are not a night and day difference to most drivers.. does anyone have a tilted subframe?

[Edub1]

I bought some of those Peak Performance urethane inserts. Wouldn't the spacers lift the rear end a little?

Does squat come from the subframe or the pumpkin dipping down in relation to the wheels? To me it sounds like the latter. I guess if there was an easy solution someone would have thought of it.

What about some type of helper spring that would add some stiffness but still allow for the full range of spring motion. I wouldn't want coils set stiff/low on the roads I drive.
Modified by Edub1 at 2:55 PM 2/12/2007

[Fenvy]

you guys whine too much.

if you see something you don't like, just walk away and don't whine about it. Now if only I can listen to my own advice...

anyways, I have had aluminum subframe bushing inserts and honestly, they made too much noise to the point that I can't take them anymore. I took them out and sold them. I am one of the few people who wouldn't recommend them. Honestly, they didnt' feel like "night and day" either, I don't think it is worth it.

consider getting some coilovers and tires then call it a day. Squat can be reduced but not eliminated. Some people WANT squat and can't get it with their sub 150hp cars.

[94_240sx]

anyways, I have had aluminum subframe bushing inserts and honestly, they made too much noise to the point that I can't take them anymore.

Were your bushings totally shot or still in decent shape? I'm curious about this. As far as I know, you shouldn't hear noise if bushings are in okay shape.