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Unibody durability off road #4974762
01/10/19 03:15 AM
01/10/19 03:15 AM
Joined: Aug 2015
Posts: 142
Central NY/Arkansas
avacado11 Offline OP
avacado11  Offline OP
Joined: Aug 2015
Posts: 142
Central NY/Arkansas
I always see videos or pictures of off road capable trucks/SUVs being ran hard in the dunes or charging thru ruts on dirt trails.

My friend drives down dirt roads and hits ruts hard in his stock Wrangler JK like a baja truck without long travel suspension. I would never drive my Subaru down a trail like that, I don’t want to break or bend any suspension components.

So does body construction effect how durable a vehicle can hold up to abuse like that? Running into ruts, having suspension bottom out or come close to hitting the bump stops.

Would having body on frame be more durable or would the extra weight do more harm than good to the suspension? Does it even matter for stuff like that? I understand rock climbing where the frame is under constant stress but for super bumpy roads...would it matter from a durability standpoint. Say something like a Jeep Grand Cherokee vs a Chevy Silverado 1500


2017 Subaru Outback - 0w20 FS - Nitto NT421Q
2014 Lexus IS250 - 0w20 FS - Continental DWS06
2014 BMW i3 - Bridgestone Ecopia
2015 Nissan NV200 - 5W30 FS - Mastercraft Courser HXT
Re: Unibody durability off road [Re: avacado11] #4974763
01/10/19 03:35 AM
01/10/19 03:35 AM
Joined: Dec 2002
Posts: 41,948
'Stralia
Shannow Online content
Shannow  Online Content
Joined: Dec 2002
Posts: 41,948
'Stralia
That's been on my mind lately too.

My wife's Captiva is super stiffer in the body than my Colorado (In can see the movement in the box on the bed through the rear view mittor), and I've soend a few hours under the Captiva today and really like how the box unibody is put together and stresses transferred through it (plus can transport a single bed and mattress with the rear seats folded down.

On damp dirt roads, especially clay, the Captiva feels really quite torsionally rigid, with the suspension doing it's job, and the unibody being the platform for it all....in my 80s and 90s with 70s and 80s unibodies, chassis flex made suspension tuning hit and miss. My parent's R16 at 380,000km cracked the windscreen one day when I pushed it into a roundabout hard...the box flexed enough to stress the glass.

Wife's Captiva, I stuck the floor jack under the front subframe at the suspension pickup point, and with the tyre less than half inch off the concrete, the other side "slid" in as the suspension relaxed, and the tyre adopted a cambered position...there was nearly no load on it...that car is stiff.

Subarus and Captivas with a couple of inches of lift do well around here on the trails and the slippery stuff, ground clearance being the major issue, and decent tyres in sizes that fit (Toyo Open Country on wifes, jagged that one).

Not good at rock ledges, with no low range...but themed 80s subarus with low range did pretty good.

Unsure how well they last before they start busting windscreens like Ma and Pa's old Renault...but bush bashers need work/repairs typically anyway.


The Dunning Kruger effect is real.
The Galileo Fallacy is real.
Roll them into one neat package and crackmeup crackmeup crackmeup
Re: Unibody durability off road [Re: avacado11] #4974765
01/10/19 03:48 AM
01/10/19 03:48 AM
Joined: Jul 2003
Posts: 4,960
New Zealand
Silk Online content
Silk  Online Content
Joined: Jul 2003
Posts: 4,960
New Zealand
Here's a bit of a comparo...they all have a chassis except the Pajero which is a unit body and full independent suspension. About 6 minutes in check out the Pajero compared to the Prado.



1987 BMW R65 - Aegis SAE30
2005 Nissan Expert - Gulf Western 10W-40
1996 Volvo T5 - Penrite HPR15 - 15W-60. Ryco syntec filter.
Re: Unibody durability off road [Re: avacado11] #4974767
01/10/19 04:05 AM
01/10/19 04:05 AM
Joined: Dec 2002
Posts: 41,948
'Stralia
Shannow Online content
Shannow  Online Content
Joined: Dec 2002
Posts: 41,948
'Stralia
And a little suby brummy



The Dunning Kruger effect is real.
The Galileo Fallacy is real.
Roll them into one neat package and crackmeup crackmeup crackmeup
Re: Unibody durability off road [Re: avacado11] #4974774
01/10/19 04:18 AM
01/10/19 04:18 AM
Joined: Jul 2003
Posts: 4,960
New Zealand
Silk Online content
Silk  Online Content
Joined: Jul 2003
Posts: 4,960
New Zealand
You still have some...they all rusted away in 3 years here.


1987 BMW R65 - Aegis SAE30
2005 Nissan Expert - Gulf Western 10W-40
1996 Volvo T5 - Penrite HPR15 - 15W-60. Ryco syntec filter.
Re: Unibody durability off road [Re: Silk] #4974777
01/10/19 04:32 AM
01/10/19 04:32 AM
Joined: Dec 2002
Posts: 41,948
'Stralia
Shannow Online content
Shannow  Online Content
Joined: Dec 2002
Posts: 41,948
'Stralia
Yeah, there's even a couple those older ones with the "power bulge" in either side of the bonnet around here.

edit...1988, a friend had one of those "power bulge wagons"...when we used to drive long distances, he jammed a jandal down beside the accelerator as a rudimentary cruise control.

Last edited by Shannow; 01/10/19 04:34 AM.

The Dunning Kruger effect is real.
The Galileo Fallacy is real.
Roll them into one neat package and crackmeup crackmeup crackmeup
Re: Unibody durability off road [Re: avacado11] #4974791
01/10/19 05:18 AM
01/10/19 05:18 AM
Joined: Nov 2018
Posts: 178
Northern Indiana
Skippy722 Offline
Skippy722  Offline
Joined: Nov 2018
Posts: 178
Northern Indiana
Here’s the way I think of it... you either have something so solid it has no give at all, like a really stiff unibody, or you have something that has some give, like a body on frame.

In the case of a stiff unibody, it’s great for on road handling. But stiff isn’t always good. Think like a piece of steel. It only has so much give before it breaks or bends permanently.

Now the body on frame. It’s got some more give to it, more springy. Kinda like a leaf spring. It can tweak a bit and return back to normal.

Now, what I’m describing here are very vague generalities. There are unibody vehicles that off-road great (Jeep Cherokee), and there are BOF vehicles that would fold in half off road.

Last edited by Skippy722; 01/10/19 05:18 AM. Reason: Fat thumbs

2016 Chrysler 300S v6
2012 Dodge Caliber SXT
Re: Unibody durability off road [Re: avacado11] #4974845
01/10/19 07:06 AM
01/10/19 07:06 AM
Joined: Jun 2003
Posts: 18,039
Deplorable in apple valley, ca
Chris142 Online content
Chris142  Online Content
Joined: Jun 2003
Posts: 18,039
Deplorable in apple valley, ca
Your friend drives like a fool. You can bend axles,frame etc from driving like that. " As fast as necessary, as slow as possible".

Some times you may need to get up a little speed to get over an obstacle. But dont be smashing over things constantly.


02 Wrangler carlube 5w30
87 F250 traveler 15w40
07 fjcruiser Chevron 10w30
Z400 castrol T 10w40
Can am maveric edge 5w40
57 case tractor 15w40
Re: Unibody durability off road [Re: avacado11] #4974895
01/10/19 08:08 AM
01/10/19 08:08 AM
Joined: Jan 2017
Posts: 2,207
VW Fanboy Island
maxdustington Offline
maxdustington  Offline
Joined: Jan 2017
Posts: 2,207
VW Fanboy Island
I have a feeling constant abuse and high miles will fatigue a unibody, more because it is glued together. Steel has an infinite fatigue life so in theory as long as you stay under the fatigue limit you should be good.

However, I know that if you plan take a air cooled Beetle off road it is recommended that you install a cage to reinforce the unibody. I'm sure that one is welded together.


03 Jetta AWP/09A 205k kms
Edge 0W40 + Mann 719/30
Re: Unibody durability off road [Re: avacado11] #4974900
01/10/19 08:10 AM
01/10/19 08:10 AM
Joined: Feb 2007
Posts: 3,729
Southeast
meep Offline
meep  Offline
Joined: Feb 2007
Posts: 3,729
Southeast
^^^ this ^^^


2018 F150
2015 crv (wifey!)
Re: Unibody durability off road [Re: avacado11] #4974930
01/10/19 08:47 AM
01/10/19 08:47 AM
Joined: Jan 2011
Posts: 3,328
PV Az
AZjeff Offline
AZjeff  Offline
Joined: Jan 2011
Posts: 3,328
PV Az
Originally Posted by avacado11

My friend drives down dirt roads and hits ruts hard in his stock Wrangler JK like a baja truck without long travel suspension. I would never drive my Subaru down a trail like that, I don’t want to break or bend any suspension components.



There's no reason you can't drive down that trail in your Subie, just don't do it like you're racing in the Baja 1000. Easing over things isn't going to hurt anything but if you find yourself doing it very much a unibody might not be your best choice. Keeping a vehicle stock and avoiding underbody contact will keep you pretty safe, if it's going to drag don't do it. Find a new line or stack rocks.


86 Samurai 1.3 leftovers
14 RAV4 2.5 5W-20 PP
16 Silverado 1500 4.3, DI, AFM 5W-30 PP

The most important thing to do in your life is to not interfere with someone else's life. - Frank Zappa

Re: Unibody durability off road [Re: avacado11] #4975099
01/10/19 11:58 AM
01/10/19 11:58 AM
Joined: Jan 2004
Posts: 4,639
California
nthach Offline
nthach  Offline
Joined: Jan 2004
Posts: 4,639
California
The unibody Pajero didn't do too bad for what it is, and it was weird seeing that Prado without all the luxury stuff, as it's sold in the US as a Lexus. I know, Top Gear but it's a Range Rover being at least used for something else but a mall/soccer cruiser.


Re: Unibody durability off road [Re: avacado11] #4975207
01/10/19 01:51 PM
01/10/19 01:51 PM
Joined: Jul 2015
Posts: 4,147
New England
madRiver Offline
madRiver  Offline
Joined: Jul 2015
Posts: 4,147
New England
The 1984-200? Jeep Cherokee was unibody and a sought after off roader. They seem to last.

Re: Unibody durability off road [Re: AZjeff] #4975251
01/10/19 02:49 PM
01/10/19 02:49 PM
Joined: Jan 2017
Posts: 2,207
VW Fanboy Island
maxdustington Offline
maxdustington  Offline
Joined: Jan 2017
Posts: 2,207
VW Fanboy Island
Originally Posted by AZjeff
There's no reason you can't drive down that trail in your Subie, just don't do it like you're racing in the Baja 1000. Easing over things isn't going to hurt anything but if you find yourself doing it very much a unibody might not be your best choice. Keeping a vehicle stock and avoiding underbody contact will keep you pretty safe, if it's going to drag don't do it. Find a new line or stack rocks.
But they drive fast on rough roads during the commercials! It's AWD right? That means it should be unstoppable and never break, because it is a Subaru after all.


03 Jetta AWP/09A 205k kms
Edge 0W40 + Mann 719/30
Re: Unibody durability off road [Re: Skippy722] #4975321
01/10/19 04:08 PM
01/10/19 04:08 PM
Joined: Aug 2015
Posts: 142
Central NY/Arkansas
avacado11 Offline OP
avacado11  Offline OP
Joined: Aug 2015
Posts: 142
Central NY/Arkansas
Originally Posted by Skippy722
Here’s the way I think of it... you either have something so solid it has no give at all, like a really stiff unibody, or you have something that has some give, like a body on frame.

In the case of a stiff unibody, it’s great for on road handling. But stiff isn’t always good. Think like a piece of steel. It only has so much give before it breaks or bends permanently.

Now the body on frame. It’s got some more give to it, more springy. Kinda like a leaf spring. It can tweak a bit and return back to normal.

Now, what I’m describing here are very vague generalities. There are unibody vehicles that off-road great (Jeep Cherokee), and there are BOF vehicles that would fold in half off road.


if both vehicles hit a rut that bottoms out a suspension, which body construction would have a higher threshold in general? A unibody designed with off road in mind(ex. Grand Cherokee that’s trailrated) or a Half ton BOF with off road HD suspension(Silverado z71).

Would a 3/4 ton or 1 ton hold up any better with a even stiffer frame or would that work against it? What about fancy suspensions like Chevy Zr2 or Ford Raptor. I’m assuming that stuff is just for comfort. But would a well designed IFS be a weak point compared to a solid axle?

Last edited by avacado11; 01/10/19 04:12 PM.

2017 Subaru Outback - 0w20 FS - Nitto NT421Q
2014 Lexus IS250 - 0w20 FS - Continental DWS06
2014 BMW i3 - Bridgestone Ecopia
2015 Nissan NV200 - 5W30 FS - Mastercraft Courser HXT
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