Ifs 101

[SLOWPOKE693]

Lots of camber built into that front suspension at ride height.



That is exactly what I want my SxS front suspension to look like.

 

[patooyee]

A recent Horschel screen capture. He is definitely in the top tier of rigs out there. Has built several rigs, upgrading each time. . I have not seen this rig in a turn yet. Thrown in here for what it is. Portal. Top outside the rim. Not a pavement pounder. Race'in......

Is it wrong that seeing suspension design like that gets me excited?

 

[SLOWPOKE693]

Is it wrong that seeing suspension design like that gets me excited?

Same boat...... I think its just part of the disease

 

[JR4X]

Thrown in here for what it is. Portal. Top outside the rim. Not a pavement pounder. Race'in......

Not a portal car

 

[mobil1syn]

portals

 

[mobil1syn]

mason which is at the top of the 4WD TT heap, hard finding ride height pics without body panels on

 

[michael.gonzalez]

PROFORMANCE MOTORSPORTS

My dad just picked up a set of their new CV axles for the EJ25 sandrail.

 

[Isdtbower]

Great updated pictures.

There is a "rule of thumb" that the axis between the upper and lower pivots go thru the rotating center of the CV's. This is to prevent plunge. But, depending on the outers camber and caster, gains, what they rotate around, and turning can change plunge. The, usually minor, plunge is taken up in the inner CV where the CV angle is not so great. The greater the plunge the more compromised the inner CV. Picture above shows this but also the conundrum of deep offsets for shaft length and location of the upper ball. Some of the reason for tall uprights is the interference of the wheel and moving the ball outside the tire. This is probably a compromise left for race'in and not recreational. (I couldn't afford a 7075 billet that big!)

I did prove to myself that turning is the real need for this "rule-of-thumb." For my IRS, REAR, I am using a midboard hub with the CV in the center of the wheel. There was no way I could get the axis thru the CV with top and bottom arms. There are actually diff-side pivot locations that allow for "no plunge". That location is about the same distance as the outside offset. This was challenging as mine were inside the diff. I used that point to draw a "pivot line" from, to place actual arm/link heim locations outside the diff. Most SXS are designed that way now. Some Dakar cars use something like that on their fronts, But I can't figure out their plunge issue.

Most commenting here know this but for some of those following along....

 

[Tech Tim]

did you run the numbers on a raptor knuckle?

No, for a couple reasons.

First off, the why we measured it up: We were looking at developing a trail series IFS, something in the $2,500.00 range that used some common parts to keep the cost down for the customer.

The Chevy GM 3500 IFS fit that bill, there are millions of those trucks out there, so tons of parts available pretty cheap. The 2010-down knuckle is pretty robust, has a good brake caliper and uses a UBH with the standard 8x6.5 bolt pattern. The OE CVs are fairly strong and RCV already had their cromo versions out.

The Raptor was still pretty new at the time, is a somewhat rarer truck and parts are expensive, they also use the metric bolt pattern.

It would be interesting to measure one or get a model.

 

[Wilson]

Tech Tim just because you specified “3500,” is the front suspension different between the 3500 and 2500?

The raptor stuff is interesting just because it is the highest performance OE setup and seems to be doing all right. Someone in this thread threw out a surprisingly low number for used front parts.... not sure how accurate that number would be, in gdeneral?

 

[AgitatedPancake]

Alright I've been a little scatterbrained when it comes to this thread. I keep jumping from thought process to thought process haha. Cool to follow along with everything you guys have been covered though.

Continuing the random theme, I have two questions that I skimmed the thread but didn't see covered in this thread - what kind of general center pivot to center pivot lengths do you guys see with your more common 14-15" wide center sections and traditional hubs (non outboard). The WMS would be a nice reference to make it relatable across all widths as well.

Second question, on something like a 934 joint around how long are the boots from the center of the joint out?

 

[Isdtbower]

Continuing the random theme, I have two questions that I skimmed the thread but didn't see covered in this thread - what kind of general center pivot to center pivot lengths do you guys see with your more common 14-15" wide center sections and traditional hubs (non outboard). The WMS would be a nice reference to make it relatable across all widths as well.

My center is 12.75" Flange-to-flange and the bottom arm is about 23" "wide." Outside of Tire is 85-86".

Saying that, I believe the WMS (Wheel Mounting Surface) is not really a good descriptor in a IFS. A IFS should be designed from the outside in. Wheel backspacing can be all over the map depending on how the upright can be designed. My wheel backspacing is 5 1/2". That allowed for a 2" longer half shaft ...with an upright that would still fit 'in" the wheel barrel. I was lucky to get special wheels made. Now they are more common as they are now generally available. Ultra4 OoT widths are usually above 90". I used the OoT width on my LJ as happy with that on the trails, but sand tires will get me out to maybe 100" OoT. I would not want that big width on the front however as the scuff would be terrible for steering in the dunes. For the dunes, The front wheel is 3" backspace and 8" wide rim with 35" tall-narrowish tire. Rear wheels are 12-14" wide with 3" BS. Tires are about 20" wide. Changing the backspace in a IFS allows you to work your "king pin angles," and scuff. The center bulkhead area is generally fixed by the diff choice, but you can play a whole bunch on the upright. and wheel backspace. Again...geometry is usually fixed by the inboard bulkhead pivots.

Yes. Make sure you allow for boots!!!!!!

 

[JR4X]

That is exactly what I want my SxS front suspension to look like.

Except for having the shocks on the upper A-arms instead of the lowers, that’s exactly what mine looks like. I went with the boxed internally gusseted fabbed arms instead of tubular because that’s what appears to work for the big boys.

 

[Isdtbower]

 

[Wilson]

And those sxs's have crazy body roll unless assisted by a sway bar. The body roll hurts the camber in a turn and why they roll so quickly and un-predictable.

Tuners work with what they are given. Maybe not what they would prefer.

It is "super easy" to tune springs and shocks but sway bars...not so much. Gary Ferrivanti could disconnect his sway bar from inside the cab. He would do that in the rocks, but stiffen in the dez. Now we have active shocks. Good luck programming those.... But the future. "We designed" to give the tuners the best chance and most adjust ability. Basically vertical, 50-60% motion ratio, and 90* at full stuff. Your choices though.

The shock tuners of tomorrow will be just like the engine tuners of today

 

[SLOWPOKE693]

The shock tuners of tomorrow will be just like the engine tuners of today

Agreed.

 

[JR4X]

And those sxs's have crazy body roll unless assisted by a sway bar. The body roll hurts the camber in a turn and why they roll so quickly and un-predictable.

Tuners work with what they are given. Maybe not what they would prefer.

Yep it is insane how much of a difference that makes to the roll center. When that thing was stock width (64” OoT) it was unmanageable. I could roll it so easy. I made it wider (78” OoT) lowered the suspension ride height while increasing the motion ratio. With the 3° camber, better motion ratio and lowering it, now I can throw it in a turn and not feel the suspension unloading. It does rely heavily on sway bars though.

 

[SLOWPOKE693]

Yep it is insane how much of a difference that makes to the roll center. When that thing was stock width (64” OoT) it was unmanageable. I could roll it so easy. I made it wider (78” OoT) lowered the suspension ride height while increasing the motion ratio. With the 3° camber, better motion ratio and lowering it, now I can throw it in a turn and not feel the suspension unloading. It does rely heavily on sway bars though.

Are those SATV arms on the front?

 

[rockyota83]

Are those SATV arms on the front?

according to the sticker on the uppers yes they are

 

[SLOWPOKE693]

according to the sticker on the uppers yes they are

In his build thread he mentions using Campbell designed RuffStuff suspension components. The sticker is why I asked the question.

 

[JR4X]

Are those SATV arms on the front?

Yes. It’s long travel stuff for a Turbo S. Literally built just like horschel stuff, the inside of them looks like a ladder, all the pieces are keyed together. Went with the 4340 threaded rebuildable ball joints to. So far pretty pleased with it.

 

[JR4X]

In his build thread he mentions using Campbell designed RuffStuff suspension components. The sticker is why I asked the question.

I used the Campbell/RuffStuff cage and bumper but I didn’t like their tubular suspension components.

 

[SLOWPOKE693]

Yes. It’s long travel stuff for a Turbo S. Literally built just like horschel stuff, the inside of them looks like a ladder, all the pieces are keyed together. Went with the 4340 threaded rebuildable ball joints to. So far pretty pleased with it.

I have the SATV 300m ball joints in the front of my car and they are very nice. Im about to order the trailing arm ball joints from them as well, to complete the package. SATV makes a set of high clearance tubular lowers for my car, and are adjustable like yours, but I have heard very mixed reviews. Some people claim having to adjust the lower arms all the way out just to get the caster/camber back to factory specs. I want them so I can add camber to the front end like your car but don't want to be stuck with a set of unadjustable arms if this is the case. Raceco USA makes a tubular cromo set that claims to have a better camber curve than factory but gives no details on what that is all about, just says "better". They are also STUPID money!

Hess Motorsports just came out with a billet rack for the Talon. I think that is going to be my next purchase. The stock ones are turds and don't take much abuse before giving up the ghost. The Hess rack also offers a few more degrees of steering which the Talon R needs.


Edit: How far apart are your front shocks mounted from each other at the top?

 

[Stephen]

I wonder if UTV suspensions rely on the rounder profile of a typical UTV tire to make camber control less important? Then we start putting square profile car (truck?) tires on them and mess it up. Similar to dirt bike tires, a good knobby works fine laid way over or off camber but a trials tire quits playing nice in those conditions. Could be a good thing to watch out for.

 

[Wilson]

I wonder if UTV suspensions rely on the rounder profile of a typical UTV tire to make camber control less important? Then we start putting square profile car (truck?) tires on them and mess it up. Similar to dirt bike tires, a good knobby works fine laid way over or off camber but a trials tire quits playing nice in those conditions. Could be a good thing to watch out for.

Great point! Treps ftw!

 

[rockyota83]

Great point! Treps at 50psi ftw!

fify

 

[Weasel]

but sway bars...not so much.

Sway bar are pretty easy. It's just a torsion bar. Some math involved but it's not terrible hard. Determine your roll moment balance and what spring rate you need on the bar is a bit more difficult.

 

[Isdtbower]

I wonder if UTV suspensions rely on the rounder profile of a typical UTV tire to make camber control less important? Then we start putting square profile car (truck?) tires on them and mess it up. Similar to dirt bike tires, a good knobby works fine laid way over or off camber but a trials tire quits playing nice in those conditions. Could be a good thing to watch out for.

I wondered why I hated trials tires! They were just not right for faster trailing or two track. I also hated tires with large blocks, which were made for 50/50 street trail. I don't mind the large block BFG's on my LJ though...Those tires do have a soft shoulder. But not "get'in it" either.

On my IRS, I am actually counting on the rolled edge of the rear tires and camber to correct about 1/2* of toe out on roll stuff.....Based on MC experience...... COOl observation.

 

[Tech Tim]

Sway bar are pretty easy. It's just a torsion bar. Some math involved but it's not terrible hard. Determine your roll moment balance and what spring rate you need on the bar is a bit more difficult.

^^^^ This.

 

[Stephen Wilson]

I don't know if it's a problem off road, but in road racing the problem with stiff sway bars is that yes, you can fine tune the rate, but it's a completely un-damped spring.