Ifs 101

[SLOWPOKE693]

Who was the guy on the old board who built the tiny IFS/IRS race buggy for KOH using mostly GM components and some fabricated arms? I think he worked for Eaton or another company like that. I remember he had trouble in qualifying and broke the car but I don't think he ever returned to PBB after that. Anybody know who I'm talking about and what ever happened to the car?

 

[arse_sidewards]

The reason we designed and/or built complete bulkheads for the racers was to keep everything exactly where it needs to be for proper geometry

And what is that geometry if I might ask?

 

[SLOWPOKE693]

And what is that geometry if I might ask?

Its the good kind.

 

[patooyee]

One other thing, since I don't personally care about racing and I'm literally on the opposite side of the country from where all sand racing takes place, I also have no reference for people like Tech Tim et al other than my prior interactions on Pirate, etc. Obviously he knows his stuff but what teams they've worked with / cars they've worked on is completely unknown to me whereas it seems like common knowledge to a lot of ya'll. For all I know he could be building race cars for Elon Musk, or conversely, be a hobo living on a street corner. I've never even watched a KOH or U4 race on the internet, much less attended one. I've watched a couple of the back door events just to see how people from this side of the country do. I live in a completely different world than many of you guys. What little sand we have here is next to the ocean and we're not allowed to drive on it. Half a mile inland the trees begin and they don't end until the either the great plains or Hudson Bay. LOL. Public land pretty much doesn't exist here, forget vast tracts of it where you would have space to go fast for miles at a time. Most serious offroading is done on small tracts of private land here.

I only say all this to help ya'll understand the frame of mind I come from so that maybe you can help fill me in on some of the references that ya'll seem to take for granted. Thank you.

 

[JR4X]

If I were trying to build an IFS from scratch i would go find me a good handling SxS suspension to measure, increase the size in a model so it fits your needs and then tweak the mounting points from there to get the caster and camber gains you are looking for.

If I can figure out diffs, this is exactly my plan. Except, for mine I want to actually use SXS suspension. My Geo tracker has far surpassed it’s proof of concept for usefulness. It’s actually been the best fun per dollar rig I’ve ever had. You can buy the bulk head for a RZR straight from Polaris. Then all aftermarket suspension parts are bad ass. The tracker is close enough in weight to the RZR it seems like a perfect match.

problems I’m up against currently. That amount of money dumped into a Geo Tracker doesn’t exactly pencil out as a great investment. The diffs I need are more expensive than I can stomach. The only part that I can see will actually be difficult is the steering. Rzr’s have the steering rack behind the front diff so the steering arms are pointed backwards. I want to turn the knuckles around and build a swing set to have the steering in front of the diff. The rzr rack won’t work in the tracker. I’m not the least bit concerned about that part, I don’t want to sink $5,500 in diffs and never get the thing finished.

 

[patooyee]

That amount of money dumped into a Geo Tracker doesn’t exactly pencil out as a great investment.

You should try owning a boat.

 

[Weasel]

And what is that geometry if I might ask?

While I get the advantage to the pre fabbed bulkhead it seem there is still alot left on the table with the front points being set but not in relation to the shock mounts or the rear suspension. I'm not saying it's bad just seems like there is room for better.

 

[Stephen Wilson]

Certainly not an unknown concept, back in the day NASCAR teams used to buy front clips from one of several builders.

 

[SLOWPOKE693]

Certainly not an unknown concept, back in the day NASCAR teams used to buy front clips from one of several builders.

Thats not just a back in the day thing...... My uncle owns a circle track chassis shop up in the northeast and they use prefab front snouts from Howe, Lefthander, Troyer and a few smaller distributors almost exclusively. Cup teams do similar things as well. Don't get me wrong, some still build their own snouts, but buying one thats a proven winner and has tons of engineering and R&D behind it is a no brainer. You want to supply customers with the best available product.

 

[SLOWPOKE693]

It seem there is still alot left on the table with the front points being set but not in relation to the shock mounts or the rear suspension. I'm not saying it's bad just seems like there is room for better.

Want to elaborate on this?

 

[vetteboy79]

The guy who buys a weld in solution for his buggy will have a faster buggy but he will not have the acquired experience to pull off those lower end projects successfully.

Either you misworded this or are just misguided, but many of the guys using these 'weld in solutions' were winning KOH 10 years ago in solid-axle cars they built themselves, and winning rock crawl comps 10 years before that in cars they build themselves, and rec wheeling in home-built junk for decades before that. No one is out there thinking they'd like to build a chassis for the first time with no prior knowledge and using a fab'd bulkhead as a starting point.

Yes, there are drivers that just write a check and don't know how to drive or wheel, and just want a turnkey buggy with no experience. They're not building it either. The guy he's writing the check to (who's buying the fab'd bulkhead) has likely been around the block a few times, and as mentioned above, knows when reinventing the wheel is a waste of time and money.

I've never been one to follow the beaten path for anything, many of you know my build here, and like Pat I enjoy the pursuit as much as the result. I'm not in it for the podium, although I've gotten there a few times. But to equate using a weld-in bulkhead with a lack of all the other experience is selling a ton of qualified people pretty short.

 

[mobil1syn]

While I get the advantage to the pre fabbed bulkhead it seem there is still alot left on the table with the front points being set but not in relation to the shock mounts or the rear suspension. I'm not saying it's bad just seems like there is room for better.

i suspect the bulkhead supplier will give you the travel of shocks to get. then its just cycle time to get everything to clear, not bind and turn.

insert the y-frame, rear pivot are already placed.

https://blitzkriegoffroad.com/colle...mponents/products/y-frame?variant=45921557702

https://diyoffroad.com/product-category/race-chassis-play-chassis/complete-yframe-setups/

 

[arse_sidewards]

Either you misworded this or are just misguided, but many of the guys using these 'weld in solutions' were winning KOH 10 years ago in solid-axle cars they built themselves, and winning rock crawl comps 10 years before that in cars they build themselves, and rec wheeling in home-built junk for decades before that. No one is out there thinking they'd like to build a chassis for the first time with no prior knowledge and using a fab'd bulkhead as a starting point.

Yes, there are drivers that just write a check and don't know how to drive or wheel, and just want a turnkey buggy with no experience. They're not building it either. The guy he's writing the check to (who's buying the fab'd bulkhead) has likely been around the block a few times, and as mentioned above, knows when reinventing the wheel is a waste of time and money.

I've never been one to follow the beaten path for anything, many of you know my build here, and like Pat I enjoy the pursuit as much as the result. I'm not in it for the podium, although I've gotten there a few times. But to equate using a weld-in bulkhead with a lack of all the other experience is selling a ton of qualified people pretty short.

I don't think you understand what I'm saying or you're just being dense.

Of course anyone buying those has knowledge of how they work and is not a novice the same way that the racing teams buying engines know what it takes to build one but just don't have the experience and consistency that comes with specialization. It's the little things that comes with specialization and experience that you're paying the big bucks for and figuring that out is the point of this thread. If the goal was to outsource the knowledge it takes to build IFS we wouldn't have this thread.

Thats not just a back in the day thing...... My uncle owns a circle track chassis shop up in the northeast and they use prefab front snouts from Howe, Lefthander, Troyer and a few smaller distributors almost exclusively. Cup teams do similar things as well. Don't get me wrong, some still build their own snouts, but buying one thats a proven winner and has tons of engineering and R&D behind it is a no brainer. You want to supply customers with the best available product.

Do they still do front end assemblies that bolt on with flanges? I always thought those were cool because you could crash your junk and have it fixed as fast as you can swap parts.

 

[SLOWPOKE693]

Do they still do front end assemblies that bolt on with flanges? I always thought those were cool because you could crash your junk and have it fixed as fast as you can swap parts.

Lefthander makes (made?) a chassis like that. Front and rear clips that bolted in place and aligned perfectly using slugs and alignment dowels. We never built any like that though, it adds to much weight to a chassis used for the small tracks up in the northeast.

 

[patooyee]

I'm comparing Chevy IFS knuckles from 2010 to 2013 and there appears to be a BIG difference in spread of the outer joints. It appears that the earlier model was designed to fit inside the wheel whereas the newer / current model curves inward so that it can rest outside the wheel, next to the tire to achieve a much lager "spread" in relation to the lower. It's pretty obvious when you compare these pics:

2013:

2010:

As a point of reference, compare the location of the top joint to the location of the top caliper bolt. I think that the caliper bolt spread may also be bigger on the newer one. I'd estimate the later model is a good 3-4" taller than the earlier. I know this helps the balls joints survive but was wondering if there were pros / cons from a design standpoint to either?

 

[SLOWPOKE693]

It looks like the 2013 spindle would require an offset upper arm due to the orientation of the upper ball joint mount. Not necessarily a bad thing if you need clearance for shock/springs. Taller spindles make it possible to run the upper control arms at a downward rake towards the inboard joint to achieve some camber gain. If you use a shorter spindle you would have to move the top inboard mounts down to gain the same result. I don't know what that does geometry wise, cause I R dumb with all this IFS stuff, but I picture in my head viewing the assembly from the side and calling the upper and lower arms "links". I know decreasing separation below certain specs on the frame side of a 4 link has negative effects, so I assume it work the same (but different) with A arms.

 

[mobil1syn]

both coilover or is the early on torsion?

 

[SLOWPOKE693]

09 2500 at work is torsion. I assume so is the bottom one in his picture

 

[Weasel]

Want to elaborate on this?

i suspect the bulkhead supplier will give you the travel of shocks to get. then its just cycle time to get everything to clear, not bind and turn.

insert the y-frame, rear pivot are already placed.

They could but we had good improvements in making sure that roll centers traveled in similar paths/rates front to rear. Balancing both to address jacking on either end and keeping the degree roll of each end similar. Some cars one end moved alot more then the other and the handling was never very telepathic to the driver (if that makes any sense). While travel can be set shock angles effect spring and damping rates, which obviously can be tuned. But that also effects the roll moments on both end which drastically effects how the car handles.

 

[patooyee]

It looks like the 2013 spindle would require an offset upper arm due to the orientation of the upper ball joint mount. Not necessarily a bad thing if you need clearance for shock/springs. Taller spindles make it possible to run the upper control arms at a downward rake towards the inboard joint to achieve some camber gain. If you use a shorter spindle you would have to move the top inboard mounts down to gain the same result. I don't know what that does geometry wise, cause I R dumb with all this IFS stuff, but I picture in my head viewing the assembly from the side and calling the upper and lower arms "links". I know decreasing separation below certain specs on the frame side of a 4 link has negative effects, so I assume it work the same (but different) with A arms.

Keen Observations. I don't have CAD models for the earlier models but I do for the 2013:

 

[patooyee]

both coilover or is the early on torsion?

Both torsion.

 

[Tech Tim]

While I get the advantage to the pre fabbed bulkhead it seem there is still alot left on the table with the front points being set but not in relation to the shock mounts or the rear suspension. I'm not saying it's bad just seems like there is room for better.

Shock tabs were welded into the lower a-arms, upper shock position was given to them.

Rear suspension depended on the team. We gave parameter suggestions to those that wanted them.

 

[Tech Tim]

I'm comparing Chevy IFS knuckles from 2010 to 2013 and there appears to be a BIG difference in spread of the outer joints. It appears that the earlier model was designed to fit inside the wheel whereas the newer / current model curves inward so that it can rest outside the wheel, next to the tire to achieve a much lager "spread" in relation to the lower. It's pretty obvious when you compare these pics:

2013:


2011:


As a point of reference, compare the location of the top joint to the location of the top caliper bolt. I think that the caliper bolt spread may also be bigger on the newer one. I'd estimate the later model is a good 3-4" taller than the earlier. I know this helps the balls joints survive but was wondering if there were pros / cons from a design standpoint to either?

We measured out a 2010~ish knuckle and ran it through the computer. The numbers weren't bad for what is was. However, we found that a taller upright would give better numbers. So, that 2013 that is taller, would be the better one to use (and agree with what we found).

 

[JR4X]

Cynicism inbound. The GM CV axle shafts are bullshit weak. I broke this one on a stock 2018 truck with the stock tires on it. I’ve done all kinds of horrible things to superduty’s and never broke an axle. I broke this CV when I wasn’t even stuck, no tire chains. I was coming out of a mud hole, the drivers side tire caught traction and the passenger side CV exploded. I can’t imagine try to keep one alive with big tires

 

[Wilson]

Cynicism inbound. The GM CV axle shafts are bullshit weak. I broke this one on a stock 2018 truck with the stock tires on it. I’ve done all kinds of horrible things to superduty’s and never broke an axle. I broke this CV when I wasn’t even stuck, no tire chains. I was coming out of a mud hole, the drivers side tire caught traction and the passenger side CV exploded. I can’t imagine try to keep one alive with big tires

to be fair, nothing oem compares to the super duty axle...

 

[arse_sidewards]

. I can’t imagine try to keep one alive with big tires

I would start by reading Weasel's sig.

 

[JR4X]

I would start by reading Weasel's sig.

I’m afraid any gains in weight losses will be erased by lower gears and larger rotating mass.

 

[patooyee]

Cynicism inbound. The GM CV axle shafts are bullshit weak. I broke this one on a stock 2018 truck with the stock tires on it. I’ve done all kinds of horrible things to superduty’s and never broke an axle. I broke this CV when I wasn’t even stuck, no tire chains. I was coming out of a mud hole, the drivers side tire caught traction and the passenger side CV exploded. I can’t imagine try to keep one alive with big tires

Fortunately, there's an upgrade:

https://www.rcvperformance.com/ultimate-ifs-cv-axle-set-for-gm-2500-3500-12-up-8-bolt-flange.html

Let us know how they hold up.

I would not consider any OEM axle shaft a long-term solution for what we do, including SD60 shafts. I'd for sure run a stock shaft in the beginning as proof of concept and to see how long it held up though. My local JY's sell those Chevy shafts for $35 + tax and have essentially unlimited inventory.

 

[Wilson]

We measured out a 2010~ish knuckle and ran it through the computer. The numbers weren't bad for what is was. However, we found that a taller upright would give better numbers. So, that 2013 that is taller, would be the better one to use (and agree with what we found).

did you run the numbers on a raptor knuckle?

 

[Isdtbower]

We measured out a 2010~ish knuckle and ran it through the computer. The numbers weren't bad for what is was. However, we found that a taller upright would give better numbers. So, that 2013 that is taller, would be the better one to use (and agree with what we found).

I see this trend recently in U4 builds and TT. It takes a lot of stress off of the top J arm and bulkhead. But not necessarily the Chevy top arm geometry as Patooyee showed.

I am pretty sure a shock tuner (and designer) will prefer verticalish but inward shocks with a 60%ish motion ratio. Rear engine guys will work at canting the top of the shocks together to improve over-the-hood visibility. I was advised to not cant my front shock package backward...But it looked more race'y.

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......