Lifted the front of the Raptor

[MarkT]

I am assuming that your impression is that on the stock vehicle the RCH is considerably below the COG...

I did not take exact measurements as it is not easy and it is very time consuming on a production vehicle. So I don't have the exact numbers you would get if you took the time to carefully measure and plot the suspension layout before and after the lift. My assumption, based solely on "eyeball engineering", my experience, and B's driving feedback is that the RCH was raised more than the CoG height was raised when he lifted the front of his Raptor.

Having the RCH move a lot more than the CoG height would be unusual. But one unusual behavior on the Raptor is how the front wheels gain quite a bit of negative camber when you jack it up. (the tops of the tires lean in) Most cars and trucks gain positive camber when raised. This indicates that the Instant Center (IC) of the Raptor front a-arm design is in an unusual place for a production vehicle. And this specific and unusual placement of the IC at ride height would result in unusual RCH behavior in my experience. I'm not an "expert" as Dan said but I've never owned or worked on a stock "street" vehicle that was set up this way.

Could B be experiencing the seemingly counter-intuitive handling change like stating lifting the front feels like it resulted in less body roll? In my experience, yes. And the other observations B made are consistent with the RCH being raised more than the CoG height... like less dive under braking.

YMMV.:thumpsup2:

 

[bstoner59]

OK, so now that our resident expert has weighed in, the question I'd like to pose to him (nothing like putting Mark on the spot) is, "So, are you going to raise your Raptor's front end AND disconnect your Raptor's sway bar?"

I don't think either mod is something that should be taken lightly. The onroad handling has been greatly affected in a negative way. As you stated the higher center of gravity is a huge deal offroad. If these were things that couldn't be undone I would never have tested either. If I could do the alignment on my own I would raise the perch and align the truck before trips.

 

[frogslinger]

I did not take exact measurements as it is not easy and it is very time consuming on a production vehicle. So I don't have the exact numbers you would get if you took the time to carefully measure and plot the suspension layout before and after the lift. My assumption, based solely on "eyeball engineering", my experience, and B's driving feedback is that the RCH was raised more than the CoG height was raised when he lifted the front of his Raptor.

Having the RCH move a lot more than the CoG height would be unusual. But one unusual behavior on the Raptor is how the front wheels gain quite a bit of negative camber when you jack it up. (the tops of the tires lean in) Most cars and trucks gain positive camber when raised. This indicates that the Instant Center (IC) of the Raptor front a-arm design is in an unusual place for a production vehicle. And this specific and unusual placement of the IC at ride height would result in unusual RCH behavior in my experience. I'm not an "expert" as Dan said but I've never owned or worked on a stock "street" vehicle that was set up this way.

Could B be experiencing the seemingly counter-intuitive handling change like stating lifting the front feels like it resulted in less body roll? In my experience, yes. And the other observations B made are consistent with the RCH being raised more than the CoG height... like less dive under braking.

YMMV.:thumpsup2:

Makes sense...

 

[Raptor1]

I believe the shocks are position sensitive,the shaft is now in a different position in the stroke,that is the part of the stroke that starts to stiffen up as the shock goes thru it's travel. Any other opinions to this?

 

[frogslinger]

What he said...

(actually I think it is in a softer part of the stroke but hey )

 

[bstoner59]

I agree...It's sits higher in the stroke so I assume it's softer as well.

 

[MarkT]

I agree with frog and b... softer part of the shock stroke...

(but probably the same damping rate as the stock ride height... the difference being after the lift the damping won't increase until the shock compresses that extra inch or so...)

 

[frogslinger]

snoogams

 

[bstoner59]

http://www.svtoffroad.com/showthread.php?1018-Fox-Shock-Perch-Adjustment&p=8179#post8179

here are my thoughts after a couple thousnad miles...

 

[Falcon]

Interesting blurb from Fox about our shocks...

INTERNAL TRIPLE BYPASS SHOCKS DEBUT ON FORD F-150 SVT RAPTOR – AN INDUSTRY-FIRST ON A PRODUCTION TRUCK – THROUGH FOX RACING PARTNERSHIP

• Ford brings the 2010 F-150 SVT Raptor, the ultimate high-speed off-road truck, to market with patented, internal triple bypass shocks by FOX Racing Shox, an industry-first on a production truck.

• Position-sensitive dampening is a key feature of the shock, helping resist bottoming in desert terrain at high speeds

• Internal bypass technology is instrumental in assuring on-road driving comfort, while still able to handle tough desert terrain

BORREGO SPRINGS, Calif., Aug. 17, 2009 – Ford’s Special Vehicle Team (SVT) and FOX Racing Shox are taking consumers where no other OEM has taken them before: off-road in the desert with the internal triple bypass shocks, exclusively available on the 2010 Ford F-150 SVT Raptor – an industry-first on a production truck.

With 12.1 inches of usable travel in the rear suspension and 11.2 inches in the front, the softly sprung suspension has enough travel to handle the toughest terrain in the desert. Usable travel is what matters – most trucks have seven to eight inches, but are so stiffly sprung that the actual movement is much less.

“Typically, automakers go for stiffer suspension character for off-road, which is the wrong approach for desert pre-runner performance,” said Jamal Hameedi, SVT chief nameplate engineer. “The suspension travel allows the truck body to ‘float’ over bumps and undulations at high speed, doing all the work to keep the truck’s attitude stable.”

Bypass shocks are used extensively in racing by pre-runners – vehicles that can be driven on-road and are capable of driving at high speeds off-road – and off-road motorsports teams. Crucial in smoothing out rough desert terrain, bypass shocks traditionally use external welded tubes to manage hydraulic pressure and provide customized jounce and rebound capability.

The internal bypass shock technology is a great off-road enabler for the 2010 F-150 SVT Raptor because it resists bottoming in the desert terrain thanks to its position-sensitive dampening.

“As the shock moves through its travel, it becomes significantly stiffer as it gets deeper into the suspension travel, becoming roughly four times stiffer at the end of the stroke than the beginning,” [Note: the Fox video says 7 times stiffer] explained John Marking, vice president, FOX Racing Shox. “The ability of the shock to go from soft to hard is what prevents it from bottoming.”

The damper also performs well on the street. Unlike most off-road vehicles, the F-150 SVT Raptor exhibits on-road plushness, improved body control and more stable roll damping because of the SVT-tuned sway bar, springs and shocks.


Heavy-duty components can take the heat

The beefed-up suspension with heavier-duty components, such as a 7/8-inch-diameter stainless-steel shock rod, also improves the force F-150 SVT Raptor can take on landings. Raptor shocks also can handle seven times the compressive damping force versus a comparable standard shock.

For Raptor, SVT engineers needed a shock with the capability to manage the heat generated in off-road conditions. The new rear damper has a remote reservoir that hangs off the side – enabling it to hold considerably more oil than a traditional shock.
With a volume of 735 cubic centimeters, the rear reservoir with more oil allows for greater heat absorption and better shock performance. The oil temperature in the internal bypass system can range up to 400 degrees Fahrenheit and as low as minus 60 degrees, depending on weather and operating conditions.

And even though Raptor is designed to excel off-road, it will still have the on-road comfort a customer would expect from an F-150.


Functional and visible appeal – shocks have it all

The shocks are visible from the front of the vehicle through openings in the front bumper, a key part of a desert truck’s appeal. With no chrome on Raptor, the visible suspension serves as the “bling” of the truck.

“Our objective was high-performance-based – we needed the shocks to perform off-road with authority and maintain street capabilities, all with visible appeal,” said Kerry Baldori, SVT chief functional engineer. “The relationship with FOX Racing Shox allowed us to achieve this.”

Designed to protect the stainless-steel shock rod from stones, a black plastic polyethylene rock shield covers the rear damper. Similar to that on dirt bikes, the shield has the strength to handle rocks thrown at it when racing across the desert at high speeds.

Another strong visual cue is the blue anodized aluminum ends on the shock absorber, with pieces both on top and bottom. The anodized ends also provide a weight reduction. The Ford SVT and FOX Racing Shox logos are co-branded on the shock, displaying the importance of the relationship.

SVT approached FOX Racing Shox because of its experience in the racing world and customer interface. While this is the first time FOX has supplied an automaker, FOX’s familiarity with the target customer and racers’ expectations of an off-road shock absorber proved to be valued insights.

Notice the parts about the position sensitivity ... stiffer with further travel. Changing the perch might just mean that you are sacrificing some ride due to the fact that you have changed the reference point. If standard perch is zero stiffness.. then changing the perch would mean you start stiffer, and the ride is stiffer. The key will be if you have enough travel left to absorb heavy shock forces. Unfortunately... Brian is the only one I know of that drives his truck to that part of the operating envelope <G>.

So it's all You B-man!

Falcon