S-14 subframe into S-14 discussion...

[jmauld]

The S-13 guys have a thread about how great the S14 subframe is, the S14 guys should too. (Just joking)

Anyway, is there an improvement to be had by moving the subframe closer to the chassis? It doesn't look like there's a lot of room to move it, but there is a small amount.

What are the cons of doing this? It looks like it would help a small amount to get the arms back in their original positions, so there might be a chance to reduce binding.

There are rumors that metal to metal contact on the rear of the BMW is the root cause for the infamous self-ejecting rearend. I assume that we really don't have to worry about that, as this area of the S14 is a bit beefier than the shock towers in the BMW.

[Matt93SE]

The early Z guys have problems with that too, but it's usually because they will switch to a solid mount on one end of the diff and have rubber/poly bushings on the other end. That puts all the stress on the solid mounts and causes them to fatigue and eventually fail. (We all know how thin the metal was on those early Zs, so I can see that happening quite easily.)

For them the fix was to go all-metal or all poly or stay all rubber.

Tangentially, the S14 would probably be in the same boat diff-wise but I don't see any reason why it would cause problems by mounting the subframe directly to the chassis. guys have mounted solid bushings on them for years. I've seen several ex SWC cars and whatnot just weld washers and a piece of steel tube through them in place of the OEM bushings, then they bolt that directly to the chassis. never seen those tear the mounts off, so I can't see it being a problem with you guys.

than again some of the guys here are running 2-3x the torque as a SWC racer. 2x the torque means 4x the chassis flex..

[CodyAce]

Anyway, is there an improvement to be had by moving the subframe closer to the chassis? It doesn't look like there's a lot of room to move it, but there is a small amount.

THis is a 'wonder' of mine as well. I don't have mine up in and pressed yet, so I'm wondering if removing 1/4 to 1/2" of material from the top of the ES bushings (and obviously the sleeve) would be a worthwhile 'move'.

[Epstein]

Well, as much time and effort as people put into moving the rear ball joint down 1/2", moving the subframe up 1/2" would do the exact same thing to the RLCA angle with the added benefit of affecting the other 3 arms as well. I want to say that I saw a scan of a Option or Tengoku mag about this. Also, I want to say that I have a pic of Nismo bushings compared to stock and that it mounts the subframe closer.

The only down sides I can think of are possibly pinching the ebrake cables (they run over the subframe) and the pinion angle of the diff which probably is negligible.

[Longfellow]

I have ES poly subframe bushings which are pretty damn tall. I wonder if I could cut the tops off of them and then shim them between the bushing and the chassis with a 1/8 peice of plate steel.

[Longfellow]

I have these which I installed over a year ago:


I'm thinking about cutting off the top section (wider part) so the top of the bushing sticks out about 2-3mm higher than the subframe itself and then making shim plates to put over it. I'll probably make 8-12 shim plates out of 1/8" plate steel or aluminum so I can stack them if I want to change the height.

[CodyAce]

This is what I had in mind as well...just simply remove that top 'lip' down to a marginal thickness and make a round plate for the tops of them...

I mean the bushing itself is going to take up the fore/aft/ movement of the subframe...but once you 'tighten' the subframe in, it's really securing it's clamp of the subframe itself against the 'frame' of the car using the metal sleeve on the inside...

I guess what I'm getting it, is that I can't see it hurting anything (only helping) by removing that upper lip.

[Longfellow]

My thoughts exactly. I just figure I'd make some slotted shims out of 1/8" plate with a 3" hole saw in the drill press and stack them accordingly.

[AdamR]

How would that effect the anti squat?

[Def]

Moving the subframe up raises the roll center and increases anti-squat.

I don't know if I'd even bother machining shims, might just opt for a washer that's already made and take the lip all the way down so it's flush up top. You might not even need a washer up there really as long as the subframe itself isn't the only thing touching the chassis.

[CodyAce]

Moving the subframe up raises the roll center and increases anti-squat.

I don't know if I'd even bother machining shims, might just opt for a washer that's already made and take the lip all the way down so it's flush up top. You might not even need a washer up there really as long as the subframe itself isn't the only thing touching the chassis.

I was thinking about using a Freightliner side front aero washer...I'm thinking it's damn near the right size..hmmmm

[Longfellow]

I have some 16ga aluminum I might use as a washer type thing between chassis and subframe. 3" hole saw and a step drill bit and they're done. I will need to make shims for the bottom side.

[CodyAce]

I have some 16ga aluminum I might use as a washer type thing between chassis and subframe. 3" hole saw and a step drill bit and they're done. I will need to make shims for the bottom side.

Ah, now I'm tracking...due to the threads running out of space...hell, any 1/2 or 9/16 ID washer should work for that....

[Longfellow]

True, I wasnt sure how much slack I'll need to take up.

I plan on foaming the subframe as well. I'd like to see how that works out. I think it'd add a little rigidity to it. I know of a shop in japan that did it to a street spec 350z and it works wonders. I'm also hoping it gets rid of a bit of road noise.

[jmauld]

Moving the subframe up raises the roll center and increases anti-squat.

Okay, so if I understand this correctly.

Raising roll center: GOOD
Increasing anti-squat: BAD

If you were getting ready to put 400ft/lbs of torque through the rear tires, would you do this mod?