Relocating front roll center via subframe?

[Def]

I've been mulling this over for a while, and during this study break I figured I'd see what others thought about it.

What about drilling a hole "some place" upwards and either outwards/inwards on a stock subframe to adjust the roll center location? There seems to be plenty of room looking at the stock LCA/subframe interference, and especially if you moved the pivot out a little bit you'd gain even more clearance that way(would probably have to correct for the swaybar and possibly the tension rod being a bit off depending on the amount outboard).

This would effectively raise the front roll center cheaply and easily.

Any thoughts on the drawbacks to geometry? Just a quick look at it, most things shouldn't change.

[cazman]

I have too thought about this, but at the front kingpin angle changes and so does camber, so you will need decent camber tops or shorter ctrl arms.
You will also need longer tie rods, and while that is easy in Australia I dont know how available they are in th US

If you are talking about the rear end you must strengthen all your pick up points as they are very prone to breaking with stock leverage, let alone with the pickups moved further outwards. the other issue is clearance at the rear, as most ZT members are needing bent toe arms to clear the subframe already, and then if you move the points up and out you will need new arms,
New issue might be camber arms hitting coilovers on S13s, but S14s have this covered by using half moon style.
But yes food for thought, and without running a decent set of numbers through a program you may be going backwards with this mod.

[Def]

How would the front kingpin angle and camber change? It would if you change the track, but moving the arm up in an arc could keep the track the same.

I don't think doing this in the rear is feasible at all, no room to change the location of links.

[cazman]

Def, At the front you cant move it up by much, it must go out as well, as it hits the crossmember, it is sloped. If you know what I mean?
You might be able to move it up about 5mm without clearance issues.
So by moving it out like you said in the first post, it would change camber, and in my mind, it would have to change kingpin angle if you were moving it up and out

In local racing you must use your factory crossmembers, so what people do is redrill the holes further out for track, then weld a washer on for strength and to cover the old hole.

[Def]

It looked like there was quite a bit of room above it just eyeballing it, but I could see how you'd have clearance issues with moving it up too much.

So moving it out a little bit would be a lot like running S14 front LCAs on an S13. Which I've seen plenty do.


Anybody else have any ideas on this?

[Epstein]

I've thought about this several times, but always come back to that "make it stick" series by Mike Kojima. It states that in a macpherson strut setup, the tradeoff to minimize bumpsteer (if you can't have perfectly identical lca/tierod from front view) is to simply locate the inner pivots of both the tierod and lca at the same point (front view). It looks like this is what Nissan has already done. I'd hate to undo the one thing that Nissan and Theory agree on.

So to do this and not undo the above, you'd have to relocate the rack, too. Which would just be easier to raise the subframe, but require you to drop the engine mounts. There's oilpan clearance for about 20mm (Nismo mounts). Got a welder and a weekend?

[Longfellow]

Got a welder and a weekend?

I do!

How much further out do S14 LCA's place the ball joint on an S13?

[jmauld]

[djsilver]

I do!

How much further out do S14 LCA's place the ball joint on an S13?

Front track is 57.7" for the S13 and 58.2" for the S14 so that's 1/2" total (1/4" per side)