Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum - This is the roll center, suspension pickup, and steering angle modification thread.

I want Def's stuff, but after having dealt with my entire front suspension for the last few months, I'm not sure I want to just turn around and sell it, since I don't think anyone would want to buy it from me, and I'd have no use for it sitting around if I managed to come up with the money for Def's stuff hahahaha

Stupid cars.

swiftmini

08-23-2010 06:02 AM

Got some testing done. Arms work well. Need to work out where my rc is so i can improve the setup further.

Also no arb!! Appears to be nice, i drove for 2 hours before i remebered they were missin.g lol.

http://i25.photobucket.com/albums/c8...i/7212d609.jpg

http://i25.photobucket.com/albums/c8...i/c387bad9.jpg

http://i25.photobucket.com/albums/c8...i/757a22a2.jpg

http://i25.photobucket.com/albums/c8...i/e95f621b.jpg

http://i25.photobucket.com/albums/c8...i/2a8b7517.jpg

A pic of it sideways showing very small amount of roll. Feels like it has more grip and less likely to push on in corner initiation (turn in)

http://i25.photobucket.com/albums/c8...i/993a6fb1.jpg

http://i25.photobucket.com/albums/c8...i/83f3285a.jpg

http://i25.photobucket.com/albums/c8...i/b375d14e.jpg

I dont get any clearance problems from the tension rod mounting position. Plenty of lock, loads of grip, fast steering! Iam happy!! Well until psm pull theyre fingers out and release everything i need :D

az_240

08-23-2010 06:29 AM

Looks like you clipped a hay bail in the first pic hehe

Good stuff... still waiting on pics of the crossmember/rack setup.

swiftmini

08-23-2010 06:33 AM

Ooops sorry, pics on theyre way now :)

swiftmini

08-23-2010 07:11 AM

conrad_s13.5

08-23-2010 07:44 AM

max needs to come out with those off-centered solid bushings for the steering rack they were talking about too!
i cant hack up my rack,...or i totally would
:/

SoSideways

08-23-2010 08:08 AM

What?

You don't hack up the rack.

You hack up the RACK MOUNTING BRACKETS ON THE CROSSMEMBER.

Hope that's what you meant in the first place...

swiftmini

08-23-2010 08:44 AM

Yep like the pics above :)

Also the offset solid bushes will probably only make 1/4inch difference. You can get an inch+ out of the stock crossmember :)

SoSideways

08-23-2010 09:02 AM

I don't think I'll be going that route, as my knuckles are modified in such a way that I do not get the over center type binding at full lock anymore, but that is certainly another good way to get rid of the over centering issue.

As a matter of fact, if you went with the front subframe mod, you might be able to get away with using the stock knuckles, those PBM or Tein tie rod spacers, and get a little more angle out of your stock setup, without going with modified knuckles.

Although, it seems that the subframe mod is actually a bit more involved and the knuckles would be an easier way to do it...

PoorMans180SX

08-23-2010 10:36 AM

I never overcentered with Tein spacers on my stock knuckles.

Swiftmini, that looks awesome!

SoSideways

08-23-2010 02:24 PM

Probably because you had stock type tie rod ends.

With any spacing and you might start to run into that problem.

I know I did with about 1.5" and up of spacing.

conrad_s13.5

08-23-2010 03:24 PM

yeah thats what i ment!....lol

FD rules say you cant touch the subframes/crossmembers in any way/shape/form. (im sure ya kno)

but maybe one day on my spirited-driving-mobile!

derek king

08-23-2010 05:18 PM

I just did megan adj front lca's and put my PBM knuckles on. Now my tie rods arent long enought (peak inner, wicked outer). I am thinking I might have to make my own sleeve that connects the inner to outer. The sleeve on it now is 2.5 inches long. I could use another 1.5 inches to have both ends safely threaded into the sleeve.

ALSO next problem The adj control arms adjust on the inside so if you are adding alot of length it pushes the sway bar mounts too far away to be useable....( Im not running a sway bar anyways just an FYI.

NEXT NEXT bigger problem. The mounting holes for the tensior rod are moved farther to the rear of the car so it added like 203007889 degrees of caster to the front almost to the point where I have my tension rods fully maxed out on length and still have a bit too much caster which is taking away from angle due to ackerman and making the knuckle max out hitting the lca before the rack is maxed out.

THE PLUS is with the spacers on the lca + the pbm knucks my tie rods,lca and tension rods are all very very close to horizontal.....

If someone could shoot me some links or info on what can help me out on the tie rod thing and tension rod thing before i have to resort to making stuff.

nieko

08-23-2010 06:00 PM

Ikeya Formula inner tie rod, PBM sells them.

super long, and you will be set sir.

derek king

08-23-2010 06:28 PM

and that will work with s14 outers? also I didnt see them on pbm for sale

ALSO does anybody know s14 tie rod thread pitch and size

95KA-Turbo

08-23-2010 07:37 PM

14X1.5

That's for the part the outer rod would thread in on.

Jonnie Fraz

08-23-2010 08:22 PM

Quote:

Originally Posted by conrad_s13.5 (Post 3603465)

yeah thats what i ment!....lol

FD rules say you cant touch the subframes/crossmembers in any way/shape/form. (im sure ya kno)

but maybe one day on my spirited-driving-mobile!

I believe that you might be mistaken on this. The rules I read state that as long as you do not cut completely through the cross member you are good. It also states if you are moving the rack forward you are good. You however may not change the pick up points.

nieko

08-23-2010 09:01 PM

Quote:

Originally Posted by derek king (Post 3603761)

and that will work with s14 outers? also I didnt see them on pbm for sale

ALSO does anybody know s14 tie rod thread pitch and size

Yes, those work with s14 outters :D

they aren't listed on the site, but call or PM Dan and he can help you out!

articdragon192

08-24-2010 01:52 AM

I had a question...
Why is the tension rod made to pivot independent of the LCA? Why not just weld it to the LCA instead of running a heim joint there, and make the LCA/ tension rod combo more of a lower A arm design?

DC Dan MAX USA

08-24-2010 02:20 AM

Quote:

Originally Posted by nieko (Post 3603712)

Ikeya Formula inner tie rod, PBM sells them.

super long, and you will be set sir.

Quote:

Originally Posted by nieko (Post 3604018)

Yes, those work with s14 outters :D

they aren't listed on the site, but call or PM Dan and he can help you out!

It was removed from our products section because of unreliable supply and the pending arrival of our original tie rod however we have some IFTR in stock now.
there is a link at the bottom of this page to buy IF tie rods
POWERED BY MAX: Forums

Quote:

Originally Posted by articdragon192 (Post 3604465)

Take my word for it, adjusting the new combo you can easily see the angle of the LCA change in relation to the tension rod. It should be pivotally mounted.
The only reason the stock type works is the bolt holes are lose enough to change the angle/ tenrod length a little. The flat end of the stock configuration aftermarket tension rods are the weak link in a front end collision. The joint and boxed in bracket will be stronger.

swiftmini

08-24-2010 05:07 AM

Quote:

Originally Posted by PoorMans180SX (Post 3603002)

I never overcentered with Tein spacers on my stock knuckles.

Swiftmini, that looks awesome!

Thanks dude. Iam very happy that you like!! I always look at usa for inspiration as you guys always appear to do things right. For example i wouldnt buy anything other than usa made bmx frame + forks.

I have another day of testing coming up on Monday so should have more feedback then!

Iam also trying to source the use of some corner scales so that i can accurately find my CofG position and then alter my roll centres to suit.

Does anyone have a rough idea what a good roll centre height would be relative to the cog.

Ie. 2inch below cog @ front and 1ich below cog @ rear

My plan is to place rc where i decide is good and then check for bump steer and adjust from there.

Ill start a build/project thread on here to document all my findings ect ect

Cheers
Kev

PoorMans180SX

08-24-2010 07:31 AM

Quote:

Originally Posted by SoSideways (Post 3603364)

Probably because you had stock type tie rod ends.

With any spacing and you might start to run into that problem.

I know I did with about 1.5" and up of spacing.

Negative, I had SPL outers with both correction spacers.

Quote:

Originally Posted by swiftmini (Post 3604543)

Does anyone have a rough idea what a good roll centre height would be relative to the cog.

Ie. 2inch below cog @ front and 1ich below cog @ rear

This is a hard one man, it depends on your springs rates, total roll resistance, and ride height.

I just grabbed some good info from Mike Kojima's "Making It Stick" that was in Sport Compact Car.

Quote:

Originally Posted by Mike Kojima

On most cars, the ideal location for the roll center is 2 to 5 inches above the ground for the front suspension and 4 to 10 inches above ground for the rear suspension. With the rear roll center higher than the front, the car will transfer more weight to the front, making it more likely to understeer. Most purpose-built racecars utilize this design because it allows them to be tuned for slight understeer at high speed and more oversteer at lower speeds.

The mass and roll center locations can be used to predict a car's natural handling characteristics. If the front and rear roll centers are plotted and a line is drawn between them, the line indicates the roll axis of the car. The roll axis is the axis that the car rolls around in a turn.

The mass axis is a line drawn between a car's front and rear centers of gravity, which can be determined using the method discussed above. Mass axis can be roughly plotted by drawing a line through the center of gravity points in the front and rear of the car. Since there isn't already a preexisting engineering term for this axis, we'll call it the Mike axis.

When the roll axis and the Mike axis are plotted next to each other, the distance and slope between the two are useful in determining a car's natural handling tendency.

If the space between the two lines is greater in the front of the car, with an upward sloping Mike Axis, the car will tend to understeer due to greater weight transfer to the outside wheels at that end of the car. Front-engine, front-wheel-drive cars strongly exhibit this trait. Conversely, if space is greater in the rear of the car, with a downward-sloping Mike axis the car will tend to oversteer.

On another note, apparently I can edit my original post again, I'll try and get to that this week!

conrad_s13.5

08-24-2010 07:34 AM

Quote:

Originally Posted by Jonnie Fraz (Post 3603980)

well,.. ima have to bust out the rule book again it looks like!.....lol

SoSideways

08-24-2010 07:36 AM

Well then I don't know, maybe it's 1.75"+ before you'll run into over centering then.

Because I was over centering on that setup, or else I wouldn't even have opted to get my knuckles modded.

PoorMans180SX

08-24-2010 07:57 AM

Oh, and from the same article there is this picture:

http://image.modified.com/f/15587576...n+modified.jpg

With this caption:

Relocated ball joints

Quote:

This Sentra racecar has had the lower ball joint relocated downward to correct the roll center and the camber curve. Chevy parts from Coleman Racing were used to fabricate this with a minimum of expense. This is an example of how these principles can be inexpensively and easily applied on any car.

Rod ends in bending on a track car. Just thought that was interesting.

SoSideways

08-24-2010 08:12 AM

That picture has been quoted and brought up many times before, and everytime it is the same answer: it is not the best way to do it.

Will it work? Yes.

Will it last? Maybe.

Will it fail? Eventually, and it will be a very spectacular failure, usually when a huge load is placed on that corner, ie. under braking, heavy cornering, etc.

I mean, I guess you can switch it out every 3 races or something, but then it gets expensive...

PoorMans180SX

08-24-2010 08:24 AM

Just thought it was interesting, since everyone says not to do it. I'm pretty sure that car was tracked regularly and didn't have any problems.

I'm also pretty sure everyone in this thread knows it isn't the "best way to do it".

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