2WD Setup Like a 4WD

[r39o]

[IdahoDoug]

The forces of physics come to bear on traction and the tendancy to spin or not spin in a surprisingly simple way. I'll discuss as to two different rear engined vehicles of very similar weight, rear drive and a very similar front/rear split of weight. Essentially bus vs Vanagon.

The amount of traction available in a pair of contact patches is determined by the weight (downforce) on them. The ability to move the vehicle forward with that available traction is determined by how much vehicle weight must be overcome to initiate forward movement. Pretty simple.

For two vehicles with extremely similar weight, with extremely similar weight distribution, on the same surface and a flat surface there'd be very little difference in each vehicle's ability to generate forward movement.

Now come the variables when you hit bumps - I'll just mention the biggies.

Tires are a clear one and I'm going to assume they're the same which is a huge assumption because in reality this creates huge differences.

Another variable is rear suspension design and spring rates. Let's divvy them and discuss spring rates first. Springs push down on the contact patches with a force equal to the weight of the vehicle on the rear of the car - and we already said that was the same. However, when you hit a bump of lets say an inch with ONE tire, some springs will compress easily (soft) and maintain fairly equal contact patch traction. Harder springs will not - actually reducing the weight on the other tire and allowing it to break traction and spin. What makes a spring "softer" is that it is compressible an inch with only a little more force where harder springs will only compress that inch with a lot more force. The latter are said to be more progressive or rising rate springs - common. It's the RATE of progressivity that varies - essentially all automotive springs are progressive.

Turning to suspension, various types of suspensions are better or worse at maintaining that ideal equally balanced traction at each contact patch during the variability of typical surfaces. Some designs have enormous friction, some have enormously heavy components, and some take the tire in an arc or angle as the suspension compresses. These all bear on traction by briefly changing the amount of downforce where better designs are consistent. I don't know what the bus rear suspension is like, but it would seem logical that VW designed the Vanagon better having learned lessons, technology moved on, etc. So suspension type would also explain a difference in traction though I'd be surprised if this area favored the bus.

There are a myriad of other suspension differences that would account for a markedly different traction capability of two otherwise very similar vehicles, such as dynamic weight transfer from front to rear during acceleration, wheelbase, differential design, engine torque curve, etc. But these two (spring, suspension design) would be the big ones worth discussing.

If you're still reading this, I'd suggest that the bus's superior traction would most likely be a subjective thing. Meaning actual measurement might reveal the newer model to be superior with identical tires. It would be quite surprising to find that the Vanagon's suspension is not better than the bus' at finding traction.

DougM
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[vanagonjr]

[240Gordy]

[vanagonjr]

[dubbified]

IN reading this thread, I've got a 90 weekender, and I just went 3.73 R/P and the GW LSD, with a rebuild from GTA. Hope it is a improvement.

I've got BFG's and seem to like the offroad handling, Ice without posi was a trick.

Since I'm at engine/trans rebuild time, am going 2.25L with ratio rocker build on the engine at Northwest Connecting rod. Hopefully it stands up to the test of time..

should have it all back together in a couple weeks hopefully put a little early spring camping.

[ericos_bob]

I believe you could greatly enhance the 2wds offroad performance with some suspension work. Always found my bay window had much softer suspension than the 2wd vanagon. Perhaps a combination of a longer stretched out spring with the same rate as stock w plus a 2" shock extension by using greater angle cv joints like the porsche 944s would remedie the inferior 2wd vanagons traction issues when comparing them to their predecessors. By increasing drop down by 2" or so over stock while increasing total wheel travel by 2". I'm sure this would wake up a 2wds offroad abilities dramatically. Throw in a diff lock and you'd have it all. Ok maybe some staun internal bead locks so you can run the tyres down to 10 psi along with some big rubber.

MMM come to think of it I'm glad I have a syncro Even if it is only a front wheel drive at the moment

[Farfrumwork]

Oh yeah, I've been wanting a √4wd (square root of 4wd) sticker ala syncro style. "2WD" doesn't have enough geek in it, and I'll have a locker so "1WD" won't be fitting.

To those that think it is some kind of sacrilege

[Farfrumwork]

[BlackDogVan]

I want a 1WD syncro style sticker for my van.
_________________
Gone but not forgotten - 1991 Carat - AAZ transmogriffied to mTDi.
Still addicted, looking for Doka...

[boulderdrop]

[MsTaboo]

Yeah, I was deeply surprised at how bad my Carat was compared to all the Bays and the splits I had. Main reason I'm into Syncros!

Hey boulderdrop, are you sure you had it in granny? Mine is very much lower than 1st.
_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

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[Williamtaylor33]

[chimivee]

[240Gordy]

[boulderdrop]

[vanagonjr]

I'm still a bit mystified why 2WD Vanagons are so bad off-road, especially when Bays seem to have no problems. Yes, I been told the bay has better suspension travel - but I've been stuck on flat wet grass, as others.

Yes, I know the weight distribution for the Bay is better, but I've off-roaded with a Toyota T-100 P/U around Moab and barely used 4WD, and never used the front and diff locks. Granted, it had killer tires, but still I usually engaged 4WD as not to beat up the truck or the road (except for one really sandy road.) and then only for limited sections. I'd blame it on the high-pressure small tires, but Bays have those as well and apparently from the sounds of this thread, better tires certainly help but the vehicle is still somewhat marginal.

I still plan to install my Syncro trans some day and probably get better suited tires that I can air (way) down. Luckily we have lots of ground clearance which for hard packed dirt roads is often only what you need. I'm not looking for a killer off road machine - in fact, maybe I should forget the off road (I'm in New England anyway) and just lower it and embrace the street - great handling these things are for being vans!

John

[boulderdrop]

[shizzon]

[BlackDogVan]

I wish Wavetrac would embrace the vanagon...

http://www.wavetrac.net/technical.htm
_________________
Gone but not forgotten - 1991 Carat - AAZ transmogriffied to mTDi.
Still addicted, looking for Doka...