Holy guacamole that's bonkers. Excellent write-up on that as well. You been around any rigs running the RK 4-link rear setup yet?
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74Weld Portal Review
- Thread starter SierraBronco
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- #212
Yip! Would recommend. Even with the stock guys you’ll notice a difference compared to those still running panhard bar.
1:05 for stock bronco vs 1:23 for stock with RK 4 Link
Not sure how well it’s going to work with the new suspension though. We’re going to have a lot of travel back there on the portal Bronco. Driveline might hit the gas tank. We’ll see.
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- #213
And just so we’re clear on what you’re calling bonkers-I’m not referring to the broken axle. That’s not really a concern. And don’t think the portals are going to save your axles. There’s a reason that we put the 32 spline UFDU on ours despite getting portals. Lot of people still blowing up axles while running portals.
What I was referring to was how your vehicle will behave with a dead rear axle. That was definitely a learning experience and made it abundantly clear why the racers don’t run portals on the rear. And remember, these guys have all the budget you could want for suspension design. Still not running them.
i thought there was a rule change for some of the classes discouraging rear portals. of course, i can't find the reference to it now
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That would be an interesting rule. Allow front but not rear. I’m not doing an extensive search but can’t find any rule like that either.
There’s gotta be some that are using them out back. Would make things so much easier from a gearing perspective. And of course-the clearance would be useful.
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- #216
Good example of the portal rigs bouncing when conventional rigs don’t:
~3:00 in. Bronco’s at 4:00
~3:00 in. Bronco’s at 4:00
It makes sense.... Why does a vehicle bounce? because you are loading up torque and then releasing it.... The springs respond. It is a lot easier to load up torque on the axle and suspension when you have a lever arm.
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I saw it, still don't believe it.
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Sounds like you “did the math” so what you’re seeing can’t possibly happen. Must be AI.I saw it, still don't believe it.
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TLDR: Portals were introduced to solve a CV angle limitation in AWD IFS Trophy Trucks while maintaining suspension travel comparable to 2WD trucks. Increased ground clearance was mostly a side benefit, though that clearance also happens to work well in KOH-style environments.
The advent of today's portals, the ones for sale by 74Weld, stems from a problem in Trophy Truck racing, specifically running an AWD platform. Prior to Mason Motorsports, the gold standard for Trophy Truck was 2WD; IFS front, 4 link full floating solid axle in the rear. The Herbst team had long experimented with AWD/4WD configurations with little success. They ran into one of the biggest issues limiting that platform; CV angles.
KOH and Trophy Trucks do not run portals in the rear because they simply don’t need to. With 40" tires and fabricated full-floating rear axles with massive hubs, they already have the clearance and strength required for racing.
Typical spindles (uprights/knuckles/etc) for 4WD/AWD setups have suspension travel limited by the CV axles in their conventional location. I think Herbst's AWD TT got maybe 20" up front, 4-8" less than a 2WD TT. That's huge in terms of how fast you can go through whoops or insurance when you brake check yourself into a ditch.
Mason Motorsports came along and ran 4-gear portal uprights up front. By moving the wheel centerline below the axle centerline, the portals allow the outer CV to sit higher in the upright and keep CV angles within limits while achieving roughly 24" of front wheel travel. There were doubters and haters, complaining it's too complex, it's gonna break, there's no benefit.
The haters were wrong. Not having AWD today = enjoying last place. It took a few years since Mason introduced AWD, but they rewrote the class definitions for Trophy Trucks. They were so dominant that SCORE created a 2WD/Legacy class. There were other parts that were needed for AWD vehicles to become the dominant platform (diff, transfer case, transmission, etc), but the portal uprights were the breakthrough for that last mile of AWD development.
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- #222
No disagreement with what you wrote. That said, if running portals in the back gave one an edge over the competition, they’d be running them, no?
The edge you want in the rear isn’t more ground clearance in today’s racing. It’s to reduce unsprung mass. Masons next gen trophy truck is looking to do that with a tractor tire drive configuration.
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I dun got me a set of dem portals 2 . 
Dey work good.
Nice write up. Good work @SierraBronco I just couldn’t resist posting it. I remember the 80’s swamp buggies. Lots of wild engineering there buddy.,
Dey work good.
Nice write up. Good work @SierraBronco I just couldn’t resist posting it. I remember the 80’s swamp buggies. Lots of wild engineering there buddy.,
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The stacked spacers thoughI dun got me a set of dem portals 2 .
https://www.facebook.com/share/p/18cd2SRMCK/?mibextid=wwXIfr
Dey work good.
Nice write up. Good work @SierraBronco I just couldn’t resist posting it. I remember the 80’s swamp buggies. Lots of wild engineering there buddy.,
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