better front suspension?

[timtiminy]

okay so i looked fullrace's s14 awd car and they did the double wishbone front suspension conversion. I'm not at all a suspension engineer/guru, but i have heard that this type of front suspension is somewhat better than what we have in our s chassis cars. What advantages does this suspension linkage provide over our independent strut-type front suspension? Question being would it be possible (not too difficult) to swap in the z32 double wishbone front suspension linkage into the 240sx? Has anyone done this before? Sure it would be something different, but i'm not sure it would even be worth the conversion, but perhaps it would lead to an even better handling car? I'm not into drifting so loosing steering angle wouldn't be that big of a deal if it meant i would get better grip/rigidity up front since our cars are known to be a little loose up front. I know that this would mean changing out spindles, shocks, swaybar and adding a few parts, but i know the lca on our cars is the same as the z32 minus the ball joint connecting to the spindle, and tension rods should also be interchangeable. doesnt seem like it would be al that difficult but i dont have the 2 cars side by side to see every detail.

[Flybert]

m3's use mcpherson struts. Go buy another car if you want double wishbone. End of thread.

[bryce with a y]

mcpherson nuff said

[DriftSpecial180]

I'm not sure about swapping Z32 suspension, but Bill (Dent Sport Garage) has built an S13 racecar and is doing very well around the circuit. His User name is DriftsTyre, shoot him a PM maybe he can give you some advice.

Also, pick up the new SCC. It has the DSG S13 on the cover. Beat the ASM S2000 by 2 seconds. Woot Woot for Bill

[timtiminy]

I know that the mcpherson struts are adequate. just wondering if our front suspension could be made any better.

[EchoOfSilence]

McGayson type suspension was a cutback, as it costs less than double-wishbone setups. Doesn't allow for much travel, camber changes with travel (which isn't exactly a bad thing sometimes), lateral movement, etc. I'd go double-wishbone at the first chance i could.
however, it does alright. could be better.

anyway, here's an excerpt:
The whole assembly is very simple and can be preassembled into a unit; also by eliminating the upper control arm, it allows for more width in the engine bay, which is useful for smaller cars, particularly with transverse oriented engines such as most front wheel drive vehicles have. For those reasons, it has become almost ubiquitous with low cost manufacturers.
In addition to its simplicity and low manufacturing cost, it has few real vices, but is not best-of-breed either with respect to either ride quality or car handling. Geometric analysis shows that it cannot allow vertical movement of the wheel without some degree of either camber angle change, sideways movement, or both. It is not generally considered to give as good handling as double wishbone suspensions, because it allows the engineers less freedom to choose camber change and roll center. The wheel tends to lean with the body, leading to understeer. Another drawback is that it tends to transmit noise and vibration from the road directly into the body shell, giving higher noise levels and a "harsh" feeling to the ride compared with systems such as double wishbones, requiring manufacturers to add extra noise reduction or cancellation and isolation mechanisms. Also, because of its greater size and robustness and greater degree of attachment to the vehicle structure, when the internal seals of the shock absorber portion wear out replacement is relatively expensive compared to replacing a simple shock absorber. However, despite the stated drawbacks the strut setup is still used on high performance cars such as the Ford Mustang, Porsche 911, all BMWs except the 2007 X5 [2] and several Mercedes-Benz models.

[timtiminy]

yeah the dsg 240rs is an awesome car it really shows tha capabilities of the 240sx. I am pretty sure he is still using the mcpherson setup.

[EchoOfSilence]

they are. with different spring rates w/ adjustable links and arms, roll center, camber and caster can be adjusted to 'fix' the 'shortcomings' of the setup. Double wishbone is said to have 'better road holding capabilities' though... but i can't come up with math to prove either one over the other. that's someone else's job :)

[reflexdb]

Well, take a look at any "race car" - that is, a car specifically built for the track. You'll find double wishbone on any current car. If you want to read a little more in depth about different suspension setups, check out "Tune to Win" by Carrol Smith. Great intro suspension / everything else book.

[TforTits]

S chassis is a shit box. why would you waste that much money and time on a shit box? because you're a fucking toolbox.

[!Zar!]

You people expect WAY too much out of these cars.

[pablo180]

Echo of Silence hit the nail right on the head. The Macpherson suspension design is more cost effective than the double wishbone design. Whether Nissan took this into consideration or not, I dont know.

Some of the down falls of the strut design are that the vehicle looses negative camber (goes into positive camber) in bump. Double wishbones gain negative camber when the suspension is in bump which is desireable in the turns. The strut suspension design also puts the strut itself in bending. As a result the strut has to be stronger, hence heavier to avoid bending. Heavier weights at the corners increase your YAW moment affecting maneuverability. Bending loads on a strut create FRICTION which is the "absolute enemy of suspension function".

This is not to say that the Macpherson strut design is bad, it can be made to perform well as many tuners have shown.

[kdashy]

Spending money to make your car handle better with the Macpherson setup will be better than the same amount of money used to swap to double wishbone.

[EchoOfSilence]

if you wanna be cost-effective, yeah

but that was Full-Race. those dudes are crazy. If someone documented it, I'm sure some people would do it.

[Taniguchi_Is_#1]

i dunno. if you really want it, i'd imagine that r32 suspension would be the closest fit. but why? you drive a street 240sx.

[timtiminy]

yeah i read the wikipedia thing, i figure it may be pretty cheap to get all the z32 front suspension links one would need for the swap. only differece i can visually see is that the z32 is 2 bolts on the strut towers where 240's are 3...i may just end up playing with this for fun. if it works out i'll do a write up.

[Wiisass]

Struts have a lot of design constraints. Just because of the way they are packaged. They aren't ideal for awesome handling, but they can be dealt with. As someone said above, the camber curves aren't great. But this is more so on a lowered car. Once you lower a strut car too much, the point the wheel rotates around moves outside of the wheel and the wheel follows an arc opposite of what it should be. But if you adjust the pivot points of the lower control arm or strut, you can get rid of this effect. Granted even when it is following an arc that it should be, it's still not the best.

Compared to an SLA suspension in this regard, an SLA is much easier to get the desired wheel behavior. But unfortunately, there would be a ton of work involved in putting an Z32 suspension on an S13. You are going to have to do something about how the loads come into the chassis because it is greatly different than how an strut suspension loads that chassis. So that will be a lot of fabrication and design. It's not as easy as welding on a mounting bracket and bolting it up, if you think it is, then you should not even be considering this project.

I really don't think this is a good idea for most people to try. The amount of design that needs to go into it to do it right, is a lot more than people think. So, no offense, but if you don't even know why you would want a Z32 suspension besides you heard it was better, then this is out of your league.

So listen to Flybert, if you want SLA, get another car. If you're that serious about making your car handle, you can do it with the struts, there are many successful race cars using a MacP setup.

[McRussellPants]

Some of the down falls of the strut design are that the vehicle looses negative camber (goes into positive camber) in bump.


What? maybe if your car is lowered to the point where the LCA is 90 with the SAI.

The strut suspension design also puts the strut itself in bending. As a result the strut has to be stronger, hence heavier to avoid bending. Heavier weights at the corners increase your YAW moment affecting maneuverability. Bending loads on a strut create FRICTION which is the "absolute enemy of suspension function".

Don't buy non inverted coilovers, their valving generally sucks anyway. bam, done.


Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX? Who cares its a 240SX? who cares its a 240SX?


Just run 1.5 more degrees of static camber compared to what you'd want with double wish and put the fucking books down.

done.

[Wiisass]

If the strut axis and the LCA form greater than a 90* angle then you will have positive camber gain in jounce, not the steering axis.

And struts have bending no matter what, it's due to the design. It doesn't matter if they're inverted or not.

[KA24DESOneThree]

You people expect WAY too much out of these cars.

Or maybe you expect too little?

Despite the fact that the cars aren't Corvettes (which Viceroy consistently makes sure to remind us about... thanks guys!), they have the capability to handle with the big dogs. It might take a little development time and quite a bit of money but something that will bring the heat isn't out of the question for someone who watches their spending on frivolous stuff like partying and girlfriends.

Fact of the matter is that a properly caged car with a lot of front bracing (not necessarily integrated into the cage) and proper suspension setup will be able to pull enough gs to make you complain of neck fatigue, and that's without time developing aerodynamics.

Anyone who says "who cares, it's a 240SX" has already set themselves up for failure. Texas is the new Florida. Take your opinion and shove it.

Tim, if you want to experience what a non-caged, street-tired S13 with a lot of suspension work can do, show up at Horsethief Mile on March 3 and then tell me if you think Z32 suspension would be worth it.

[!Zar!]

KA24DESOneThree: I didn't make any statements on a 240 not being able to handle.

If that was the case I wouldn't have invested as much money as I did in my s14's suspension.

What I am stating is that people need to be happy with what they have.

People need to invest in regular suspension parts, tires, geometry and, skill before bashing what they know little to nothing about.

So I expect everything I need from my car. I'm realistic.

And in the end is it not just a 240?

[Team Rootbeer]

there are probably a select few on Zilvia that could actually even NOTICE the fucking difference between the two setups in an actual driving experience.

everyone stop whining and drive

[McRussellPants]

Why don't any of you Track Clowns just roll 450HP 3071 and 275/305 Stagger and beat vettes instead of womping about how if you adjusted your roll center enough and scraped the paint off your wheels to save 5 ounces your busty ass KA could maybe keep up?


Big Power(band) wins races, not just in drag racing.

DSG car beat N/A S2K by 2 seconds. how much of that is accounted for by a 150whp difference? maybe all of it :shrug:

[McRussellPants]

lolchmercerlol: nobody had 400 hp in initial d russell

oh fuck, charlie keeps me in check.

lol at KADEs sig. I don't know about everyone else but My parents are about ready to throw a cinder block through my windsheild.

[KA24DESOneThree]

Big Power(band) wins races, not just in drag racing.

DSG car beat N/A S2K by 2 seconds. how much of that is accounted for by a 150whp difference? maybe all of it :shrug:

Power does win races, that much we agree on. However, I find more skill development comes from being limited in power and having to conserve momentum and brake late. I can't save myself with power application because there's no power to apply.

!Zar!- The phrase "just a 240" bothers me with its dismissive attitude. Always has, always will.

You do bring up a good point about skill development; I can guarantee any driver here could see a decrease of at least a second (for the competition drivers in here, for the rest of us, we'd probably be looking at 3-plus second decreases on short tracks; I know I'd gain that much if I just improved my consistency) in their lap times at almost any track with a 3-day visit to a driving school. A switch to Z32 front suspension could not do the same.

Besides, wouldn't it be better to go with real racecar parts for the SLA setup rather than heavy and marginally adjustable stock bits? Tube frame the front, do some right proper measurements, weld some mounting tabs on and then do it with adjustable arms. Then widen the fenders by 150mm per side and put some 18x11s up there and call it good.

[Ian]

Yeah...so after driving REAL cars...you understand why people say "it's just a 240sx"


Corvettes are just better...Porsches are even better than that...deal with it

[OptionZero]

and mustangs are better than 911s!

[pablo180]

Just run 1.5 more degrees of static camber compared to what you'd want with double wish and put the fucking books down.

Sure you could run more static camber, but you'll affect straight line performance.

Who cares its a 240sx?

That comment is completely unncessary.

Why don't any of you Track Clowns just roll 450HP 3071 and 275/305 Stagger and beat vettes instead of womping about how if you adjusted your roll center enough and scraped the paint off your wheels to save 5 ounces your busty ass KA could maybe keep up?

Big Power(band) wins races, not just in drag racing.


The thread is about suspension geometry. Not engine performance.

[McRussellPants]

lol




message length

[seekanddestroy]

Sure you could run more static camber, but you'll affect straight line performance.

Straight line stability and traction to be exact, to a degree...
The Zero Sports STI is running something like 10 deg static and would destroy you on the track.

But then again, talking about suspension on a 240 forum is 100% pointless because 99% of the people on here are drifters.:)

[pablo180]

Straight line stability and traction to be exact, to a degree...
The Zero Sports STI is running something like 10 deg static and would destroy you on the track.

But then again, talking about suspension on a 240 forum is 100% pointless because 99% of the people on here are drifters.:)

Thanks for the correction.
I'm not familiar with the Zero Sports STI, but 10 degrees static is a lot to run. How much suspension travel do they have? What series do they run in?

Heh, I didnt think about the audience reading this, but i'd like to think that there are at least a couple of people who read this who are interested in racing their 240sx's :)

[ralphyboy]

I am 32 and the reality is the it's just a 240sx thing is null and void because it's light as hell and cheap as hell to buy in the first place. Any upgrades you do to a more expensive car would be as expensive as it is on the 240. You would never be able to get it as light as the car comes from factory, much less once you start adding lightness. If changing to orange juice filled blinkers made the car better and faster to the point that it went up against bigger and badder siblings I'm all in. If it happened to cost 4000 dollars, well guess what, I paid 1400 for my car so I would still have the edge in price over a z32 in exactly the same shape. Not all of us are drifters and some of us understand why we like these cars.

[seekanddestroy]

Thanks for the correction.
I'm not familiar with the Zero Sports STI, but 10 degrees static is a lot to run. How much suspension travel do they have? What series do they run in?

Heh, I didnt think about the audience reading this, but i'd like to think that there are at least a couple of people who read this who are interested in racing their 240sx's :)

Zero Sports ran their STI in the 06 eurotuner/superstreet time attack series.
I dont know any other specifics... although being pretty much a race car, it isnt running suspension with much travel, i didnt notice it having much/any noticeable body roll.

http://i12.photobucket.com/albums/a242/bluefcs3/IMGP37852313.jpg

[McRussellPants]

Thanks for the correction.
I'm not familiar with the Zero Sports STI, but 10 degrees static is a lot to run. How much suspension travel do they have? What series do they run in?

USA time attack mobile.

it probably has like 4.5/5 degrees from looking at the pictures, which is standard fare for R-comps and mac struts.

Heh, I didnt think about the audience reading this, but i'd like to think that there are at least a couple of people who read this who are interested in racing their 240sx's :)

I could drift a car on 195s on a 11J and 14kg springs.

doesn't mean I didn't read the same crappy internet FAQs and ZOMG Carrol Smith books as everyone whos a "real road racerZ"

[pablo180]

USA time attack mobile.
it probably has like 4.5/5 degrees from looking at the pictures, which is standard fare for R-comps and mac struts.

Hard to determine from the photo but it does look like it runs a lot of camber probably to compensate for the MacP strut design and limited suspension travel.
I could drift a car on 195s on a 11J and 14kg springs.

doesn't mean I didn't read the same crappy internet FAQs and ZOMG Carrol Smith books as everyone whos a "real road racerZ"

I'm not sure what you are trying to point out here.

[ohspizzill]

and mustangs are better than 911s!


and gixxers are better then mustangs!

[seekanddestroy]

Hard to determine from the photo but it does look like it runs a lot of camber probably to compensate for the MacP strut design and limited suspension travel.

Yeah, it isnt the best photo, but its the best one I found that I had. With macp, if you are running very stiff rates, you really do need a lot of static camber, because it a) isnt going to travel much b) will add positive as it travels if the control arms are above parallel in travel. Either way it really doesn't matter too much, with very stiff rates, you will have to run a lot of static either way, I mean unless you have caster etc set up, which I am not too familiar with so I cant really comment on that.

Those are d.o.t. Rs mcrussell, not quite as soft as full race compounds. :)

[pablo180]

Yeah, it isnt the best photo, but its the best one I found that I had. With macp, if you are running very stiff rates, you really do need a lot of static camber, because it a) isnt going to travel much b) will add positive as it travels if the control arms are above parallel in travel.

That is correct. Could not of said it better myself.

Either way it really doesn't matter too much, with very stiff rates, you will have to run a lot of static either way, I mean unless you have caster etc set up, which I am not too familiar with so I cant really comment on that.

Its kind of hard to visualize but adding more caster will give you more negative camber on the outside wheel as you have greater steering angles. The wheels kind of "dive" into the turn. One downside to this though is that the driver has to increase steering effort because adding more caster also picks up the front end of the car as you turn. This isnt a problem with cars that have power steering but can be a problem if you have a manual steering setup.

[seekanddestroy]

Its kind of hard to visualize but adding more caster will give you more negative camber on the outside wheel as you have greater steering angles. The wheels kind of "dive" into the turn. One downside to this though is that the driver has to increase steering effort because adding more caster also picks up the front end of the car as you turn. This isnt a problem with cars that have power steering but can be a problem if you have a manual steering setup.
Thanks, by increase, do you mean negative or positive caster? Or forwards or backwards would probably be easier to understand...

I do have tension rods, So I will definetly get some caster dialed in when I go get it aligned, I do have manual steering, but at the moment I am using 215/40/17 tires.. and will probably have some 215/45/17 Neovas on when I get the car to the track for the first time (still have to upgrade the brakes).. But steering effort with manual has never been an issue for me.

[pablo180]

Thanks, by increase, do you mean negative or positive caster? Or forwards or backwards would probably be easier to understand...


More positive caster meaning having the lower suspension point further in front of the contact patch of the wheel and having the upper suspension joint behind the contact patch of the wheel.

http://www.rqriley.com/images/fig-7.gif
This is an image showing positive caster.

[seekanddestroy]

More positive caster meaning having the lower suspension point further in front of the contact patch of the wheel and having the upper suspension joint behind the contact patch of the wheel.


This is an image showing positive caster.

Yeah, more would generally mean positive :doh:

I think I will get around 3 degrees when I get it aligned, to test it out and see if it is still easy enough to turn etc.

[!Zar!]

3* caster will make your car twitchy. And really twitchy for initial turn in.

I'd suggest starting off around stock. 6* iirc.

And that subaru has that much camber in the front not only because it's MacP, but also because it's awd. That car needs as much turn in midway so it can rotate through the corner as it can get. Yes that car has an extremely short stroke. So I don't see camber changing alot through out it's bound.

It's hard for me to state much more on it's suspension setup without being able to see how the tierods are in relation to the spindle.

[Wiisass]

Hooray misinformation.

This thread is a mess.

Less suspension travel does not equal more static camber. Why would it, the wheel doesn't move as much, so it won't lose as much during cornering. And most race tires, even DOT R compounds like a lot of camber, like 3-4* and that's even with a suspension that won't lose camber as badly as a strut suspension in a turn.

You guys also don't seem to grasp the concept of why a strut suspension loses camber with jounce sometimes. Look at the instant center, look where it is stock, look where it goes when you lower the car and the lca and strut axis are greater than 90* apart. If you look at that you'll realize when and why the wheel gains positive camber in jounce sometimes and sometimes it doesn't.

As for caster and steering angle and it's relation to camber. Yes, more positive caster will increase negative camber with steer on the outside wheel. But you also have to remember that kingpin has the opposite effect on the outside wheel. And the steering effort increase is due to the increase in mechanical trail. The raising of the front end with steer has other effects and can actually add to the self centering effect of the wheel due to the added weight on that corner. Just be warned that too much positive camber, well actually too much mechanical trail, in relation to the pneumatic trail from the tire will wash out the feel and can cause the wheel to get stuck at lock. This is based on the moment that the mechanical trail creates around the kpi. And 3* of caster would not work. Stock is around 6-6.5 and I wouldn't go any less than that.

So now can we stop this whole thing, it's getting out of hand. I don't know if the original poster is convinced that trying to put a Z32 suspension on his car is a bad idea, but non of this partially true suspension talk that you guys are carrying on is going to help it. So just give it up.

[pablo180]

You guys also don't seem to grasp the concept of why a strut suspension loses camber with jounce sometimes. Look at the instant center, look where it is stock, look where it goes when you lower the car and the lca and strut axis are greater than 90* apart. If you look at that you'll realize when and why the wheel gains positive camber in jounce sometimes and sometimes it doesn't.

Had to draw it out to get an understanding of what you were saying. Makes sense.


As for caster and steering angle and it's relation to camber. Yes, more positive caster will increase negative camber with steer on the outside wheel. But you also have to remember that kingpin has the opposite effect on the outside wheel. And the steering effort increase is due to the increase in mechanical trail. The raising of the front end with steer has other effects and can actually add to the self centering effect of the wheel due to the added weight on that corner.

You've got it backwards. CASTER has the opposite effect from side to side when more steering angle is introduced. Kingpin inclination has the the effect of rasing front of the car regardless of which direction you are steering in.


Just be warned that too much positive camber, well actually too much mechanical trail, in relation to the pneumatic trail from the tire will wash out the feel and can cause the wheel to get stuck at lock. This is based on the moment that the mechanical trail creates around the kpi. And 3* of caster would not work. Stock is around 6-6.5 and I wouldn't go any less than that.


I'm assuming you meant too much positive caster, not camber. I dont see how adding more positive caster could cause the wheel to get stuck at lock.
If anything the additional mechanical trail due to more caster will just increase the self centering effect.


So now can we stop this whole thing, it's getting out of hand. I don't know if the original poster is convinced that trying to put a Z32 suspension on his car is a bad idea, but non of this partially true suspension talk that you guys are carrying on is going to help it. So just give it up.
No. :)

Off Topic: I saw the images in your website. Virginia Tech FSAE Alumni? What year?

[McRussellPants]

Hooray misinformation.

This thread is a mess..

Zilvia
Thread about Flux wire MIGgin on new front suspension
ect.

You guys also don't seem to grasp the concept of why a strut suspension loses camber with jounce sometimes. Look at the instant center, look where it is stock, look where it goes when you lower the car and the lca and strut axis are greater than 90* apart. If you look at that you'll realize when and why the wheel gains positive camber in jounce sometimes and sometimes it doesn't.

My frame could be 4inches into the ground before I'd start to gain camber.

Tell me how to make that possible, and still have camber gain be my biggest problem and I'll get the spanners ready.

[ixfxi]

you guys cant fuck with pablo.

[Wiisass]

What do I have backwards? More caster, more negative camber gain with steer. KPI is the opposite. Higher KPI, more camber loss with steer. As far as raising the car with steering, it is more an effect of KPI. Caster does have some diagonal weight jacking properties as well though. But all in all, the work together, becuase you can't have the effects of one without considering the effects of the other.

I did mean caster, it was just a typo. Adding more positive caster will increase the mechanical trail. Adding mechanical trail has it's benefits and it's downfalls. You will get more self centering and better steering feel, but the idea is to balance the mechanical trail with pneumatic trail. Look at pnuematic trail versus slip angle curves, pneumatic trail peaks earlier and falls off as the slip angle increases. You need to look at the feedback at the steering wheel as the slip angle increases. You want to have a certain fall off of feedback as you reach the limit of adhesion. So you don't want too much, but you don't want too little. And the wheel getting stuck at full lock, too much mechanical trail move that point too far forward and it can create too much of a moment when the wheel is fully turned. This moment when translated to the steering wheel can make the force input necessary to turn the wheel very high. So like you had said that required steering force is increased as you increase caster, this is the extreme of that.

Yeah, VT FSAE Alumni, 03-06.

[Wiisass]

My frame could be 4inches into the ground before I'd start to gain camber.

Tell me how to make that possible, and still have camber gain be my biggest problem and I'll get the spanners ready.

You're going to have to go lower than that. Just get your CG at ground level and then you won't have any weight transfer when doing anything. You won't even need a suspension on there besides to steer.

[seekanddestroy]

Yeah about caster, Like I said I dont know much about it, I didnt look at the FSM for stock specs.

Stock is 5.55-7.25.

So would be getting it set at the higher stock limit be ok? Like I said, i'm not running large tires right now.

Toe-in is 0-12 deg stock, I think I will have it set around 0, or perhaps a little bit of toe out.. anything wrong with this?

[pablo180]

The rabbit hole just gets deeper and deeper. All in good fun i hope! :)

What do I have backwards?

This part...

But you also have to remember that kingpin has the opposite effect on the outside wheel.

We're practically saying the same thing but I just think its because of the way I am reading it or the way you are typing it is whats bringing up confusion.....so lets summarize.

Kingpin Inclination (KPI) has the same rising effect on both wheels regardless of which way you turn. It adds to steering effort because you are literally picking up the front end through the steering wheel. It has the undesireable effect of putting the wheel in positive camber as it turns.

Caster has the positive effect of additional negative camber on the outside tire as more steering angle is introduced. It picks up one tire while dropping the opposite tire causing diagonal weight transfer which gives the oversteer effect that so many drifters look for. It also does give more steering feel due to the mechanical trail that comes along with adding more camber.

KPI and Caster are both related.

I agree with you that you need to balance mechanical trail with pnumatic trail so that you can adjust steering angle once you feel the tires begin to break loose.

MacP strut can gain or loose camber in jounce based on LCA location as well as the angle between the strut axis and the LCA. The double wishbone design is more desireable because you can control your camber curves throughout suspension travel. That is not to say that MacP cannot perform well on the track.

[Wiisass]

I didn't have that backwards, I think you just read it wrong. I said:

Yes, more positive caster will increase negative camber with steer on the outside wheel. But you also have to remember that kingpin has the opposite effect on the outside wheel.

So KPI has the opposite effect meaning positive camber gain with steer versus the negative camber gain with steer effect of the caster.

And although caster can add to an oversteer condition, I would attribute much of the affect to it. Especially for drifting, counter steer will load up the opposite wheel as compared to normal steering. If you enter a normal turn, the inside front and outside rear wheels will see added weight due to the diagonal weight jacking, but if you're countersteering, it will be the opposite. So it may help with entry to some extent, but even during entry, you won't see too much of an effect because you won't be steering that greatly.

And as for the strut losing or gaining camber, the LCA location alone will not cause positive camber gain in jounce. It's the instant centers that define this, so it has to be a combination of the strut angle and the LCA together.

[SoSideways]

And as for the strut losing or gaining camber, the LCA location alone will not cause positive camber gain in jounce. It's the instant centers that define this, so it has to be a combination of the strut angle and the LCA together.

So if I got an adjustable LCA like those Orangetree or Ikeya Formula ones, or even the SPLparts ones, I can lengthen the LCA w/ the pillowball mount, and also move the mounting point where the ball joint mounts to the spindle (moving the LCA's location to decrease the angle between the LCA and strut), would I be able to get close to being able to gain regain some of the "negative camber gain" effect that is found on the stock suspension/ride height, or would it still not come close?

Car's an S13 that's got 2.5" of space between the frame rail and ground.

Just curious how close it will get to that point...

[McRussellPants]

Anything you can do to make the angle between the LCA and SAI smaller will get you more negative camber gain.


I don't care enough to be Mr Geometry and work it out.

your gonna have pretty big sideloads on your strut to get it back to the stock height gain rate, so I doubt its worth it.

[Wiisass]

Stop saying SAI. Unless someone changed SAI to mean strut axis inclination instead of steering axis inclination.

And if he's that low it will probably just get less positive camber gain in jounce.

[McRussellPants]

Stop saying SAI. Unless someone changed SAI to mean strut axis inclination instead of steering axis inclination.

And if he's that low it will probably just get less positive camber gain in jounce.


camber plate ball joint to LCA outter ball joint. same thing?


I thought we agreed your frame height would be way the fuck below ground before you actually start to get positive camber gain.

[Wiisass]

Kind of but not really, the steering axis is from the upper ball joint the the lower ball joint, but the way instant center is defined is a line perpendicular to the upper ball joint and in line with the LCA. And you know that the strut doesn't lie in the steering axis.

[pablo180]

ahhh....sounds like we need some visual representation here to clear things up.

If anyone is genually interested in seeing camber change in jounce i'll happily make a model of it on Solidworks and put it in CosmosMotion so you can see it in action.

I just need a couple of people to give me the following parameters.
LCA inboard joint to outboard joint and angle with reference to ground
Upper and Lower points of MacP setup and angle with reference to vertical
Distance from lower ball joint to lower MacP setup.

[Wiisass]

If you need visual representation look in chapter 17 in racecar, in the front suspension section under Macpherson strut. There is a diagram that shows instant center and roll center. The upper control arm line is a line perpendicular to the strut axis at the toop and the lower control arm is a line from the LBJ to the inboard pivot. I don't know why you need pictures and models to show that.

And why use solidworks if you're really going to try and model the suspension. Use a real program like ADAMS or even Susprog3d. It's a lot less work to get better results.

[wanganwonder]

i think i got an alignment once

[pablo180]

Yes, you can see it in Race Car Vehicle Dynamics (RCVD for us formula guys) but you can see much more about behavior when there is an animation in front of you instead of a photo.


And why use solidworks if you're really going to try and model the suspension. Use a real program like ADAMS or even Susprog3d. It's a lot less work to get better results.


Modeled in Solidworks and run in CosmosMotion. What is CosmosMotion powered by??

ADAMS.

You can check out our white paper up on their website.
http://www.cosmosm.com/pages/services/support/documents/Motion_VehicleSuspension.pdf

[A Spec Products]

http://www.lasa.org.uk/uploads/netgain.gif

[Chernobyl]

Pablo and Wiisass,

Are you guys employed engineers or just students?

[Wiisass]

Well I didn't realize that Cosmosmotion was powered by ADAMS. That's good to hear actually. I just started using Solidworks at work and I haven't had the chance to explore all the features too much yet. We just used stupid Unigraphics when I was at school for all our CAD, and then ADAMS for the suspension design. How is the interface in Cosmosmotion versus the interface in ADAMS? Like how easy is post processing, etc?

Chernobyl, I work.