Golf - Rear beam options - Front Subframe?

So I still haven't figured out what I'm going to do for the rear beam and since I'm going to use the stock gas tank, I don't have many options.

However, I came across this pic, which just might clear the stock tank.

They used a stock front subframe and put it on the rear - just add an additional bar that connects to where the tie rod was and you've got a independant rear suspension for cheap with some adjustability. I'm gonna go do some measuring and see if it will clear the tank. Plus it will make slapping on my 11" corrado front brakes on the rear, really easy

Anyone see any concerns with this? Shock length might be less than stock, but since there is no CV's, the shocks can hang down behind the hub further than in front.

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-Jason



Edited 1 time(s). Last edit at 11/25/2008 05:06PM by mack73.

That.... is intriguing. To say the least.

The geek in me says that unsprung weight will go up, since the beauty of the beam is that very little of the actual weight is moving at suspension travel, most of it is close to the pivot.

The geek in me also thinks, hey, I can get a spare subframe for the front, beef it, relocate the rear bushing so that it does not use one of the subframe bolts (you know, the way everyone else in the civilized world does it), cut and hack to make the Caddy rack fit... all the little stuff. Then the old suckier subframe can be given new life as a REAR subframe.

Mind you, this is all for the street car.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

My only concern is that this is INSANE!!!

Not enough VW pron in this thread so:

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Eddie Fiorelli Wrote:
-------------------------------------------------------
> My only concern is that this is INSANE!!!
>
>
>


Why is that insane? I nearly did the exact same thing with my Dodge Omni and if I had kept it I probably would have. The only problem would have been with escalation. You see, once you have put a front crossmember in the rear it gets the old gears in the head turning and you start thinking about how easy it would now be to just bolt another motor in the rear but then where do you put the gas tank and how do you rig up the shifter so it will shift two trannies and, well you get the point.

Doivi Clarkinen Wrote:
-------------------------------------------------------
> Eddie Fiorelli Wrote:
> --------------------------------------------------
> -----
> > My only concern is that this is INSANE!!!
> >
> >
> >
>
>
> Why is that insane? I nearly did the exact same
> thing with my Dodge Omni and if I had kept it I
> probably would have. The only problem would have
> been with escalation. You see, once you have put
> a front crossmember in the rear it gets the old
> gears in the head turning and you start thinking
> about how easy it would now be to just bolt
> another motor in the rear but then where do you
> put the gas tank and how do you rig up the shifter
> so it will shift two trannies and, well you get
> the point.


Yeah and then you'll end up with something like this



Rear Engine


Front Engine

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-Jason

This idea has just the right mix of simplicity and stupidity to make me really happy.

My only thought is that you may want to make the height of the subrame adjustable so you can raise and lower the inner pivot points of the control arms to tilt the roll axis in whatever direction feels appropriate. Ditto on inner mounting points for the tie rods, which will give you toe curve adjustment. I suspect, though, that a straight toe curve that doensn't change with bump will be best for your rallying happiness.

And that has me wondering about durability... Are you more likely to bend a rear tie rod/toe control arm in a rear-wheel ditch bump than you are to bend a rear beam? Just asking questions, I don't know how hard it is to bend rear beams, but I'd hate to see all this work go toward making the car more delicate.

Wait a minute, why the hell are you doing this again? Is there something wrong with the VW beam? Shocks too cheap? Too much travel? Not enough unsprung weight? Are you just doing this so you don't have to carry as many spares? (Same control arm front and rear!)

-D

eyesoreracing Wrote:
-------------------------------------------------------
>
> And that has me wondering about durability... Are
> you more likely to bend a rear tie rod/toe control
> arm in a rear-wheel ditch bump than you are to
> bend a rear beam? Just asking questions, I don't
> know how hard it is to bend rear beams, but I'd
> hate to see all this work go toward making the car
> more delicate.

This is a good point, though Audis have a similar arrangement in the rear and it doesn't seem to be a problem. It's really easy to bend rear beams but it's also easy to bend toe links, especially when they are in compression.

>
> Wait a minute, why the hell are you doing this
> again? Is there something wrong with the VW beam?
> Shocks too cheap? Too much travel? Not enough
> unsprung weight? Are you just doing this so you
> don't have to carry as many spares? (Same control
> arm front and rear!)
>

My reasoning for the Omni was that the rear beams were always bending. Even if you never hit anything (yeah, fat chance of that) the constant rally pounding would create more and more negative camber until the tires were rubbing on the springs. And having the same spares front and rear sounded pretty cool, too.

Yup, the VW rear beam is notorious for bending at the arms to yield camber. Basically don't bother putting an unreinforced beam (pre-89) beam on a VW since it you are extremely likely to return home with mucho more camber than you started with.

Even VW got the message by upgrading the beams with gussets in the late model mk2s:



The late model ones are better than the earlier beams, but they can still use more reinforcement for rally use.




Edited 2 time(s). Last edit at 11/26/2008 03:02PM by Eddie Fiorelli.

Hell, driving on the street and tap a curve with the inside rear and you get toe-out. (ONE of these days I'll fix that!)

Hit something HARD and things go really weird.

VW knew this was a problem with the beam from its inception. They're very flexible, actually. That's why VW pretty much invented bushing compliance rear steer with the Rabbit's odd ramped bushings (*), the beam would flex to toe-out and positive camber in mid corner so the ramped bushings' compliance would steer the beam the other way. They still added a shit-ton of toe-in and negative camber to compensate. As the beams got tougher and less flexible the rear alignment went closer and closer to zero toe/camber.

Anyway hit stuff and you bend 'em, so you need to brace them, which gets in the way of the stock fuel tank, so using a front crossmember is a keen brainstorm to be able to use the stock fuel tank and still not have to keep a stockpile of beams handy 'cos your choice is either beefing the beam and doing all sorts weird shit to seal a fuel cell, or stock tank and weaker beam.

(*) Look under a Honda Fit or a Toyota Echo/Yaris/Corolla. I wonder if they are paying VW royalties, the ramped beam bushings look almost identical to the stuff under my '89 VW. VW on the other hand have "graduated" to simply using regular cylindrical bushings but mounted at an angle (plan view) so that lateral loads steer the beam by just sliding the bushings on their sleeves, no ramps.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Pete Wrote:
-------------------------------------------------------
> Hell, driving on the street and tap a curve with
> the inside rear and you get toe-out. (ONE of
> these days I'll fix that!)
>
> Hit something HARD and things go really weird.
>
> VW knew this was a problem with the beam from its
> inception. They're very flexible, actually.
> That's why VW pretty much invented bushing
> compliance rear steer with the Rabbit's odd ramped
> bushings (*), the beam would flex to toe-out and
> positive camber in mid corner so the ramped
> bushings' compliance would steer the beam the
> other way. They still added a shit-ton of toe-in
> and negative camber to compensate. As the beams
> got tougher and less flexible the rear alignment
> went closer and closer to zero toe/camber.
>
> Anyway hit stuff and you bend 'em, so you need to
> brace them, which gets in the way of the stock
> fuel tank, so using a front crossmember is a keen
> brainstorm to be able to use the stock fuel tank
> and still not have to keep a stockpile of beams
> handy 'cos your choice is either beefing the beam
> and doing all sorts weird shit to seal a fuel
> cell, or stock tank and weaker beam.
>
> (*) Look under a Honda Fit or a Toyota
> Echo/Yaris/Corolla. I wonder if they are paying
> VW royalties, the ramped beam bushings look almost
> identical to the stuff under my '89 VW. VW on the
> other hand have "graduated" to simply using
> regular cylindrical bushings but mounted at an
> angle (plan view) so that lateral loads steer the
> beam by just sliding the bushings on their
> sleeves, no ramps.

What the fuck youse talking about?
pics or ban!
>

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

The ramped bushing thingy?

Here's a VW - you can see how there's a kind of ramp thingy so when you put a side load on it, the bushing center pushes the beam forward, making the rear steer against the corner:



Some autocross and road race guys are FINALLY learning that it makes the cars turn in super awesome if you flip those bushings the wrong way. Sounds like a recipe for squirrely handling if it's the least bit bumpy.

Here's the beam from a Honda Fit. I was wrong, it's not like the A2/A3 VW, but this is the way the A4 (New Beetle, Golf/Jetta IV) beam is laid out, almost exactly, with the angled std. type bushings:



I can't find any good Toyota pics. I might havbe been wrong about the Echo, but it was ONE of the new small Toyotas. Or maybe the Versa. Japanese companies are going gaga over superior VW technology (finally).

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

I once thought long and hard about doing the same thing and only took a pass as I did not think it would be fun to build it all in my condo parking lot.

The car drives OK down the stage with the beam bent and turns in really well with lots of toe out.

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In the long run reality always wins.

Jason, Build a beefy beam.....or put the motor in the back....and the cell up front.

ours:

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-Tom
DemonRallyTeam | Fine Tuning | CTS Turbo & RP Turbos | RalleyTuned | JRM | Meister Autowerks
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So did some measuring today and it won't clear the stock tank - probably about 3 inches shy.... oh well.

I guess I'll be beefing up the stock beam, but Tom, I don't think those will clear the stock tank either.

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-Jason