Who wants portal axles..everyone! (2 Viewers)
- Thread starter nigelsiam
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
I think you should bother because I'd personally like to understand why it lowers the CG. In my mind, you have two identical vehicles down to the finest detail- same weight, same springs, same wheel and tire sizes- except that one has portals, and the other has regular axles. In that scenario, how do portals change the CG? The roof of both trucks are at the same height above the ground, right? Or is one higher than the other? If the roof is higher, does that also mean that the cg is higher, or would it be lower? Does moving the tires further away from the body, frame and engine/tranny/transfer case lower the CG?
Clearly, you're passionate about your idea, and I respect that. Help me also understand it.
Fair enough:
(All this is approximate! don't nickel and dime me for half an inch here or there)
You have two 80's, the first with no lift with 30" tires and approximately 10" of clearance. (30" divided in two is 15" minus half your differential at 5") You don't need a lift to clear these tires, and you stick to the little 30's for the sake of an internet debate giving you net 6" increase.
The portal axles give you about 6" clearance without changing tire size. Your at 16" clearance with 30" tires.
The other cruiser is built with straight axles, you want the same 16" clearance, you bolt on 42" tires. 6" radius is 12" diameter, but you only net 6" increase of clearance (42" divided in two = 21 minus 5" diff is 16").
The second cruiser now needs to clear the 42's, you go to 8" of lift and cut out the fenders, move axles outwards.
The first cruiser, is 6" higher than stock, the second is 14" taller (6" tire radius +8" lift) the first truck has the same axle diff clearance.
So obviously no one would bother with 30" tires, but the point is COG comparison based on required clearance. Same clearance under the diff for these two trucks, but lift height needed for 30's vs. 42's... the portaled axle could have eve less lift if there was clearance for shorter springs, not that you would.
If you put 37"s on the portal truck no lift needed with 6" portal clearance, you now have 19.5" clearance from the diff, the straight axle truck needs 49's to match that and have the same amount of clearance under the diff, more actually cause 80 series axles won't last you long with that big of a tire off pavement so your running bigger axles now.
How and why does this matter? If your running a trek that similar sized trucks have been on you likely won't get high centered in ruts they would. If you need this clearance for a trail with tree stumps and obstacles to strattle you don't need as big of a tire to clear them, something you'll appreciate later on a side slope. Larger and fatter rubber has the advantage in deep snow, but deep snow is not a narrow v groove hill climb, and the lower gearing of portals will be your friend for bigger rubber anyways.
Sure, you've got the weight of the axles further up with the portals, but it's unsprung weight and isn't tilting the sprung components like the weight of your powertrain, roof tent and camping gear.
You can get away with smaller rubber, probably what others haven't considered. Please don't drag me further into an internet argument to split hairs though.
SmokingRocks
hopelessly addicted to Cruisers
I see how you are arriving at that logic, it's not what I described in my examples. And I stand by what I stated in my example, yes you gain clearance at the diff but all other things equal you will move the axle mass up higher thus raising the CG. Even if the roof line is at the same level.
Also
you don't need 8" lift to clear 42's (with enough trimming you can fit 40's on stock height search this forum for proof)
and
Doing this lowers the CG point.
Also
you don't need 8" lift to clear 42's (with enough trimming you can fit 40's on stock height search this forum for proof)
and
Doing this lowers the CG point.
Last edited:
2fpower
SILVER Star
A vehicle's center of gravity can be lower with portals as you don't need as large of a tire than it would be if using a conventional approach (big tires, big body lift) to achieve the same clearances.
Plus, Chicks dig the high axle.
Video Greg Maddux and Tom Glavine reveal 'Chicks dig the long ball' was their idea
Plus, Chicks dig the high axle.
Video Greg Maddux and Tom Glavine reveal 'Chicks dig the long ball' was their idea
SmokingRocks
hopelessly addicted to Cruisers
In theory I agree, if the only clearance we are concerned about is from the pumpkin to the ground.
That said, I'd have to run the numbers but I would believe that the COG would be the same as a rig that used tires and trimming to raise the axle to the same height. COG is all about where the mass is, and if the axle mass is 16" above the ground and the roof line is at 70" above the ground for both builds then the COG is the same or within a negligible difference.
Thats where I'll leave it. I look forward to seeing your work @cody c
I'll leave the numbers out, but look at it this way. With portals, the lift is all under the axle. What's on top isn't pushed higher in relation to the axle.
If you lift the conventional way with springs, etc, the lift takes place all above the axle. That's why the COG goes up more than with portals, all other things being equal.
In the video I cited earlier, the owner noted he didn't want to raise things above the axle, so left things at stock height, but with increaed carrying capacity. Apparently, some limited lift is allowed in Australia, but he saw no need for it and definite advantages with doing it via the portals.
If you lift the conventional way with springs, etc, the lift takes place all above the axle. That's why the COG goes up more than with portals, all other things being equal.
In the video I cited earlier, the owner noted he didn't want to raise things above the axle, so left things at stock height, but with increaed carrying capacity. Apparently, some limited lift is allowed in Australia, but he saw no need for it and definite advantages with doing it via the portals.
So with portals we can run a smaller tire!
Out of curiosity, what do portal axles weigh? The Unimog ones are ungodly heavy.
Out of curiosity, what do portal axles weigh? The Unimog ones are ungodly heavy.
But what does it COST to keep your COG low and your axles high, man?
How low (high) can you afford to go?
How low (high) can you afford to go?
2fpower
SILVER Star
Pretty sure my Volvo portals are maybe 50 lbs heavier as a standard 80 series. Of course after all the armor I put on them probably a little heavier....
I have driven a nissan patrol that was owned by a mate of mine, on those marks portals. on the road around town, at highway speeds up the coast, windy roads, offroad etc. There were a couple issues with them but I think that may have had something to do with them being some of the very first ones that were produced by marks and were bugs that have (hopefully) been ironed out since.
If I had a patrol, I personally would be taking the time to put the $16k aside for them. some folks here are saying that it raises your COG and wont handle well etc. yes higher COG, however the geometry of the suspension remains that of the stock car. this patrol was on 37's that measured out to be 36" tall without a suspension lift and handled like a car. it did have better springs and bilstein shocks. and I was putting it to the test, it took lane changes and corners just like a stock patrol on better springs and good shocks. it was an auto petrol with lpg, f&r lockers, 37's. and offroad this drove some unimog only lines. it would scare natives.
one downside, it was so wide the tyres were bumping over the lane reflectors of both sides around some of Sydney's streets, you did have to be mindful about that with so many other terrible drivers around. the thing was too tall to park in any of the shopping centre car parks and any unit block garages. too wide for those too.
so a couple down sides however I still want a patrol on portals.
please excuse the s***ty photo, it's taken from my facebook and i have to crop out some other stuff. I'm pretty sure the tyres on it here are 35's but hey, this is about 10 years ago now so who knows.
If I had a patrol, I personally would be taking the time to put the $16k aside for them. some folks here are saying that it raises your COG and wont handle well etc. yes higher COG, however the geometry of the suspension remains that of the stock car. this patrol was on 37's that measured out to be 36" tall without a suspension lift and handled like a car. it did have better springs and bilstein shocks. and I was putting it to the test, it took lane changes and corners just like a stock patrol on better springs and good shocks. it was an auto petrol with lpg, f&r lockers, 37's. and offroad this drove some unimog only lines. it would scare natives.
one downside, it was so wide the tyres were bumping over the lane reflectors of both sides around some of Sydney's streets, you did have to be mindful about that with so many other terrible drivers around. the thing was too tall to park in any of the shopping centre car parks and any unit block garages. too wide for those too.
so a couple down sides however I still want a patrol on portals.
please excuse the s***ty photo, it's taken from my facebook and i have to crop out some other stuff. I'm pretty sure the tyres on it here are 35's but hey, this is about 10 years ago now so who knows.
Last edited:
SmokingRocks
hopelessly addicted to Cruisers
I understand but everything still moves up 6" including the axle. Your COG still moves up since ALL the mass of the vehicle is raised. COG is the point from which the weight of a body or system may be considered to act. The center of gravity of an object is calculated by taking the sum of its moments divided by the overall weight of the object. The moments increase in value as you elevate the object.
Wouldn't you agree that if you had portals which lifted the axle 3 feet above it's stock location that the truck would be more top heavy? Of course, because the COG was raised.
Yes if you are trying to equal the clearance from the axle to the ground. But not if the roof lines are at the same elevation.
- Thread starter
- #33
I have a new model to shoot for.. This 80 is saweeeeet!!!So with portals we can run a smaller tire!
Out of curiosity, what do portal axles weigh? The Unimog ones are ungodly heavy.
View attachment 1792598
