Is there any logical reason for this?

[Fejery4491]

As I tear more and more into my 2g I find more and more things the 2 owners prior to me hacked together. I'm getting ready to drop the front subframe and strip it to coat it and during my degreasing process (this thing was caked with like 2 inches of muck) I came across an area of the front subframe that appears to be hacked up some.

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This is on the drivers side. As you can see, it looks as though someone cut that up a bit to get a that arm out or something. Here's a picture of the passenger side for comparison.

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Is there any good reason for someone doing this? Or is this just another fine example of them hacking stuff apart? I'm just a little picky about my build, and think I'll just pull the front subframe off my buddies parts car and just coat that and scrap this one. Unless of course there's ANY good reason for it, but based off the rest of this car, I doubt it.

 

[greengoblin]

That is terrible. You are going to have to have that fixed. There is no good reason to do that. I bet a bolt was seized and that was how they got to it to cut it out.

 

[95talongirl]

Grrrrrrr..... crap like that makes me angry.

Why can't people just leave things alone? If it's too difficult to to yourself, then take it somewhere. I'm sorry you have to fix this, now, too.

 

[Fejery4491]

At least I have a front subframe availible....I should post up their way of doing the drivers side motor mount for a 6 bolt swap hahaha. I will when I get inside.

Well I got dibs on the front subframe from the parts car, so now I'll pull mine tomorrow and swap in on the parts car so we can still roll it around.

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Oh, and here's a terrible cellphone pic of the drivers side motor mount, haha. They used the mount off the 1g instead of a 2g like they should, it didn't hold that side of the high enough so they just made a new hole and put a bolt into the wheelwell. The engine still leaned to that side. This car was so hacked together, don't even get me started on the wiring....

 

[bjones18]

An interesting, funny, and potentially good teaching aid might be a special section of DSM tuners with "FAIL" pictures of how NOT to modify your DSM. or FAIL pics like your own of how a previous owner might have a leading spot on a wall of shame :^)

These pics are amusing but running into this kind of crap because someone was too lazy, cheap, or unskilled to do it right... is no fun.

 

[greekgodchaos]

An interesting, funny, and potentially good teaching aid might be a special section of DSM tuners with "FAIL" pictures of how NOT to modify your DSM. or FAIL pics like your own of how a previous owner might have a leading spot on a wall of shame :^)

This I like a lot. A sticky thread should be made with posts of what NOT to do in whatever situation a user posts up. That way we could trim down the number of instences where someone posts up,

"Well I just spliced my MAFT into my wiring harness using blue wire nuts from Home Depot and now its not running right, what do I do??"

or my favorite:

"Ok so I just bolted on a hyBriD t3/T4 Turbo off EBAY onto my 420a and it won't fasterrr!! Whats wrong?? Oh and I have no other mods just the manifold and turbo."

Mods should really consider this, I think it would be a great addition to the Newbie Forum. Besides, thats what I believe these cars are all about; Preventitive Maintenance. Show the newcomers that rather than hacking into their electrical system blindly and using wire nuts, butt splices, or twisting wires together and then hoping that the electrical tape they layered on will hold them together isn't how you do it if you want to have a properly running car, and instead link to a page or two on how to properly solder wires together. Also this will keep the rest of us who have answered the same question a hundred times before from banging out heads against the wall or facepalming ourselves again and again. Just my opinion...

 

[jtmcinder]

OK, we've had our laugh; now let's make some lemonade. Why not take this as an opportunity to raise the inboard pick-up points by about an inch, to get the front roll center back up where it belongs?

 

[skatershawn]

Man, sorry to hear you have to deal with that!
Best of luck with you on the rest of your journey!

 

[Fejery4491]

OK, we've had our laugh; now let's make some lemonade. Why not take this as an opportunity to raise the inboard pick-up points by about an inch, to get the front roll center back up where it belongs?

Is that what greengoblin did? Or am I thinking about this completely wrong?

 

[jtmcinder]

Yep.

When you lower a 2G to reduce weight transfer, you also lower the roll centers. Once the lower lateral arm angles down from the knuckle to the inboard pick-up, all sorts of bad things happen since the inwards force from the outside wheel is now levering the outside of the car down even more ... so you get extra body-roll. To fight this, you either have to go to outrageous front spring rates, which costs you mechanical grip, or move the ball-joint on the knuckle downwards (using, e.g., Whiteline ball-joints, but they don't fit 2Gs easily), or move the inboard pick-up point upwards. Since you're already going to have to work on the inboard pick-ups and this happens to be the best fix, that's what I'd look into doing.

Note, however, that if you don't do something similar to the compression arms' inboard pick-ups, you'll have the opposite of anti-dive, so the car will have issues when braking. But that's true for any lowered 2G.

 

[bjones18]

Yep.
When you lower ... you also lower the roll centers. ... or move the inboard pick-up point upwards....

and if you raise the inner LCA pivots you must raise the steering gear to avoid tons of roll-understeer.

Roll center height is important but not worth hacking up your subframe. and if you get your L/R heights different you will have different roll steer L/R. Off by one-mm vertical makes a noticible difference in roll steer. OEMs Hydropierce all suspension attachments in a single operation to maintain +/- 0.25mm

 

[Fejery4491]

Yep.

When you lower a 2G to reduce weight transfer, you also lower the roll centers. Once the lower lateral arm angles down from the knuckle to the inboard pick-up, all sorts of bad things happen since the inwards force from the outside wheel is now levering the outside of the car down even more ... so you get extra body-roll. To fight this, you either have to go to outrageous front spring rates, which costs you mechanical grip, or move the ball-joint on the knuckle downwards (using, e.g., Whiteline ball-joints, but they don't fit 2Gs easily), or move the inboard pick-up point upwards. Since you're already going to have to work on the inboard pick-ups and this happens to be the best fix, that's what I'd look into doing.

Note, however, that if you don't do something similar to the compression arms' inboard pick-ups, you'll have the opposite of anti-dive, so the car will have issues when braking. But that's true for any lowered 2G.

Well now you got me thinking, if I'm swapping out subframes with my buddies parts car it HAS to be tomorrow, or I'll be doing it out in the snow. I guess I just really need to decide what I should do.....

 

[bjones18]

How about this for starting a fail section

 

[jtmcinder]

and if you raise the inner LCA pivots you must raise the steering gear to avoid tons of roll-understeer.

Roll center height is important but not worth hacking up your subframe. and if you get your L/R heights different you will have different roll steer L/R. Off by one-mm vertical makes a noticible difference in roll steer. OEMs Hydropierce all suspension attachments in a single operation to maintain +/- 0.25mm

While you are absolutely correct that the steering box will need to be moved or Whiteline rod ends will have to be used, the idea that a DSM has lower inboard attachment points within .25mm of each other is laughable. If you don't have, for example, the RRE lower front brace, they move relative to each other quite a bit (and still move around after you add the brace). A small baseline difference is not going to be a big deal.

But, again, you are correct that something will need to be done about the added bump-steer, just as something really ought to be done about the inverse anti-dive on a lowered 2G.

 

[bjones18]

Not saying you gotta hold to 0.25mm. If you run Adams models or have a K&C machine you will see a difference in toe-gain with a 0.1mm increment in the vertical height.

I have driven vehicles with lots of anti-dive. It's not good. Also, I have a BMW 330 known for a high rear roll center- too chattery on lateral grip. I have also driven a car with roll-centers at the cg. Everyone who has studied suspension design has wondered about this concept for over 40 years... the guy who built this vehicle had lots of money. The vehicle was a basket case on small purturbation roads... dancing all over. Effectively, body roll and pitch allow a smooth transition (damped with good shock ratios and low-speed-valving) on transient maneuvers and road irregularities. Calculate the roll couple difference between stock and lowered 1.5"... roll center probably drops about half that. and roll couple change? More info on roll centers (abstract below):

Understanding Vehicle Roll Using Mechanism Simulation Software

Why does the average guy think suspension modifications are "shoot from the hip?" We swap engine parts that were designed for 4G63s. Few people take a stock piston and weld it or change it's dimensions hoping to make more HP.

Modifying suspension attachment locations is a MAJOR design change. I don't recommend it unless you have read a few books and done some chassis work. But then again... it's their car. Go for it Dude! It's gotta be better... right?

 

[jtmcinder]

Not saying you gotta hold to 0.25mm. If you run Adams models or have a K&C machine you will see a difference in toe-gain with a 0.1mm increment in the vertical height.

Complete models of the 2G suspension exist; I wrote one of them. The idea that you will see a noticeable change in toe with a .1mm change in either ride height or pick-up point height is, to be gentle, untrue. Yes, it changes. We know these cars have non-zero bump-toe even when you have everything parallel, due to the fact that it's a SALA double-wishbone with a steering arm between the two arms. But it's not like tiny changes will do anything of significance, especially when the bushings are still rubber or urethane.

Modifying suspension attachment locations is a MAJOR design change. I don't recommend it unless you have read a few books and done some chassis work. But then again... it's their car. Go for it Dude! It's gotta be better... right?

Or you can trust someone who has done the math for you. I don't know everything about engines, so I let others tell me what to do. One of the reasons I'm still here, five years after selling the DSM, is to help people who don't want to spend six months learning suspension dynamics.

 

[greengoblin]

The Robi spec mods on my xmember move my suspension pickup point around 1in up and inward I believe. I do not have an OEM xmember to measure off of. I simple decided to trust Robi on this mod since he has WAY more experience than me and the mod has worked VERY well on Andrew's car.

As for moving the compression arm? I looked at that for some time and that would be very hard to do on the OEM xmember IMO. There just not a lot of room. If some one has moved there I would love to see how they did it.

Kevin

 

[bjones18]

The idea that you will see a noticeable change in toe with a .1mm change... Yes, it changes.... But it's not like tiny changes will do anything of significance....I'm still here... to help people.

Based on your note, I think we are in agreement. I commend you on your help with DSMTuners. The discrepancy challenge of this thread really started with an off the cuff suggestion to take a "boogered-up" subframe and possibly change an attachment location to raise roll center. While this is possible, and maybe a good idea, the information is not complete and may lead someone down a path that creates more problems than it solves.

1. Just about anything will drive down the road.
2. If you measure what you have you can tweak if needed.
3. Many outstanding vehicles result from poor designs & excellent development.
4. Some great designs are inferior due to poor development (tuning).

Revolution vs evolution. Design evolution is the result of many small changes that make positive impacts. Revolution often leads to unforseen issues.


For completeness: The issue with a suspension geometric "point" being off by 0.1mm or 1.0mm is not a real issue. The problem comes in that we have 20 suspension points (3UCA, 4LCA-2g, InnrTieRod, TRE, Gearmount: x 2sides = 20). Holding tolerances on a bridgeport-mill is one-thing. Holding tolerances when drilling holes on a subframe is another. If someone cannot hold +- 2mm on attachment points, geometry-curves can be all over the map, and roll-steer/bump-steer is the absolute most sensitive to tolerance variation. Numerically you can tell the difference in roll steer by moving a "primary-point" such as TRE-vertical 0.1mm. So... imagine if the eight-primary-points responsible for roll-steer are each off-dimension by 2mm... each in the wrong direction. Toe curves will be a suprise and most likely different left to right.

 

[Colt4G63 also]

Here's my contribution to the fail thread:

If you don't have the clips that hold your wheel bearings into the hubs, and your wheel bearings are traveling toward the center of your 1g DSM, but you don't want your rotors rubbing on your caliper brackets...

Don't do this

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[bjones18]

Very good note. "just the facts Maam." No F-bombs or degrading name calling.

It is interesting how 4-out-of-5 washers seemed to be enough. For those who are wondering... this will distort your brake rotor when the lugs are torqued down.