How's my numbers?

[ditcherman]

I can probably answer some of this.

His rear uppers are 5 inches apart. The 2.5 is distance from the center line.

3 link setups are slightly easier to package the uppers than a triangulated setup since you are beside the engine. He has some advantage in that his lowers are below the axle tube.

Thanks, not the first time I’ve made that mistake on the centers distance. I should have known.
I’m doing the same thing on my front three link as far as dropping the axle end below the CL.

 

[ditcherman]

You did get me thinking about lock to lock, granted this thing is massively toe-ed out right now, I grabbed some 2” box and gave it the old community college try. These are 48” long and I’m not tremendously worried about it if I mount them inboard of the frame. I’m chopping the frame at the body mounts anyway, so the rules are made up and the points don’t matter. As long as I can get the driveshaft to work and I’d love to not have to modify the oil pan. Even if I do, I have a sawzall, welders and a sense of adventure (actually if the oil pan starts getting fucked with I’m gonna be real tempted to dry sump it because I’m an idiot and make poor financial decisions).

Treefrog covered the rear uppers. Both axles are already welded up and I’m sure that’s gonna bit me in the ass when I actually start building the truck in 5 years.

I can relate to every bit of this! It’s a crazy thing we do.

 

[1981gMachine]

Hopefully this isn't too random for a 1st post. I've been deep in the rabbit hole for the last few weeks reading up on 3 link front suspensions. I found this from the Linked Suspension Bible thread on here and found the spreedsheet calculator on another site. I consider myself fairly knowledgeable on rear suspensions and front independent suspensions. I've read through Herb Adams Chassis Engineering book a dozen or so times in the 20years I've owned it. I understand the racing principles for car setups.

What I don't understand is what you should look for data wise for a good driving street truck. I know 100% anti squat and dive is considered neutral. But I would think for street driving, and being used as a truck. You'd want to sway those percentages one way or another.

I have a 2wd 67c10 that I'll be building a full frame out of 2x4x.250 wall mandrel bent frame rails and converting the truck to 4x4. I have no intentions on off roading it. 33" tall tires and what will amount to roughly a 2" lift over a factory 4x4 ride height. I want to do a 3 link with coil overs to get a better then factory ride. I understand the effects of anti dive on the front but I haven't found anyone talking about street manners when talking percentages. I'm thinking a little anti dive would be ideal to absorb PA roads and give some nose dive in braking. Is 90% a good starting point. With building a frame, I can move around most of the frame side ends to a degree. I'm not sure about the Roll Axis Angle. I thought I read somewhere that the number is reversed when calculating for a front suspension.

Is there anything the jumps out as a red flag?

 

[Treefrog]

Hopefully this isn't too random for a 1st post. I've been deep in the rabbit hole for the last few weeks reading up on 3 link front suspensions. I found this from the Linked Suspension Bible thread on here and found the spreedsheet calculator on another site. I consider myself fairly knowledgeable on rear suspensions and front independent suspensions. I've read through Herb Adams Chassis Engineering book a dozen or so times in the 20years I've owned it. I understand the racing principles for car setups.

What I don't understand is what you should look for data wise for a good driving street truck. I know 100% anti squat and dive is considered neutral. But I would think for street driving, and being used as a truck. You'd want to sway those percentages one way or another.

I have a 2wd 67c10 that I'll be building a full frame out of 2x4x.250 wall mandrel bent frame rails and converting the truck to 4x4. I have no intentions on off roading it. 33" tall tires and what will amount to roughly a 2" lift over a factory 4x4 ride height. I want to do a 3 link with coil overs to get a better then factory ride. I understand the effects of anti dive on the front but I haven't found anyone talking about street manners when talking percentages. I'm thinking a little anti dive would be ideal to absorb PA roads and give some nose dive in braking. Is 90% a good starting point. With building a frame, I can move around most of the frame side ends to a degree. I'm not sure about the Roll Axis Angle. I thought I read somewhere that the number is reversed when calculating for a front suspension.

Is there anything the jumps out as a red flag?

I recommend grabbing one of the newer versions of the calculator from the resources tab. 3-links got merged into the 4 link tool. It also has the roll slope corrected for the front.

Anti dive is probably good to keep low, 20-30% with a normal braking bias. It will keep it from riding rough while braking.

Anti squat of 80-90% with all the drive bias set to the rear is probably a good target.

I think you are right about the roll slope being flipped.

 

[1981gMachine]

I recommend grabbing one of the newer versions of the calculator from the resources tab. 3-links got merged into the 4 link tool. It also has the roll slope corrected for the front.

Anti dive is probably good to keep low, 20-30% with a normal braking bias. It will keep it from riding rough while braking.

Anti squat of 80-90% with all the drive bias set to the rear is probably a good target.

I think you are right about the roll slope being flipped.

Thank you, I've been playing with he newest version of the calculator.

 

[endless CJ]

Regarding the rear, decreasing the antis some will help. As it is now, in 2wd, you will be right at 100% anti. And as the axle moves up and down, it will switch between squat and anti squat tendencies.

In the front, it may be worth looking more into which side the upper is mounted on. A good place to start that is to look into no torque roll with 3 links.

You may want to tend towards more understeer; a short wheelbase rig is more sensitive to it.

Just about to start burning mounts in place. I think I'm happy enough with the rear, i can move the frame mounts down about 1.5 inches, and i could spread the upper axle mounts out a little if there is some advantage. axle lowers are no longer moving without a plasma cutter...

Up front of course packaging is the issue. i can move the lower frame mounts around a little in all directions, but not seeing any change in roll slope. I'm assuming i want to get closer to 0 or less at ride height. appreciate any recommendations.

cj7 aluminum body, 5.3 LMG, needs to be streetable to get to the fun stuff...

Thanks,

Thanks for the feedback. I think I'm wearing out the tape measure at this point, but this is what I've come up with. Got a little understeer at ride height front and back, I'm assuming my front pinion numbers indicate i will not be gaining/losing too much caster, and I'm fairly certain it will physically fit. Rear AS gets high at full droop but stays under 100, +/-1" adjustment available on the uppers looks like it will give me some reasonable change in performance.. no matter what I tried i couldn't get anything reasonable with higher frame mounts on the lower links, front and rear, which sucks from a clearance standpoint, they will be dropped 1 1/2 to 2" off the bottom of the frame.
Front anti dive is in the 30's, and the line is flat, not sure the ramification of that number, but i think the flatness means the behavior won't change drastically through travel?

Thanks for any further commentary and advice!

 

[Treefrog]

Thanks for the feedback. I think I'm wearing out the tape measure at this point, but this is what I've come up with. Got a little understeer at ride height front and back, I'm assuming my front pinion numbers indicate i will not be gaining/losing too much caster, and I'm fairly certain it will physically fit. Rear AS gets high at full droop but stays under 100, +/-1" adjustment available on the uppers looks like it will give me some reasonable change in performance.. no matter what I tried i couldn't get anything reasonable with higher frame mounts on the lower links, front and rear, which sucks from a clearance standpoint, they will be dropped 1 1/2 to 2" off the bottom of the frame.
Front anti dive is in the 30's, and the line is flat, not sure the ramification of that number, but i think the flatness means the behavior won't change drastically through travel?

Thanks for any further commentary and advice!

Antis near full droop are less critical due to the low traction and subsequently low forces involved. The lowers are typically the governing factor is in low antis can go.

Your assumption about the flat line is correct, I think. I'm still looking into forces through travel.

 

[thezentree]

My turn?

I have a 1st gen Taco reg cab 3RZ with an old Trail Gear 3 link kit on it. Use case is southeastern trail rig that is going to see interstates to get to and from the woods. I'm at least the 3rd owner since it was built almost 20 years ago, and I was told the axle was "folded under" the truck. The upper link is 6" longer than the lowers and looks like it's been sleeved, so who knows how all this came to be. It drives like crap on the road, and I really want to make it be less bad. I don't think "good" is in the cards, so I'm happy to settle for that.

The rear is leaf sprung.

Here's what I measured today:

I'm kinda limited on what I can do with the frame side brackets. The frame side panhard bracket is potentially moveable, but I really don't want to mess with the link brackets on the frame.

My current plan is to shorten the upper link to bring the pinion angle down (it's pointing well above the tcase output) and to add a little more positive caster, but beyond that I'm not really sure how to make this be less bad. From what I've read here my AD numbers are way too high. The truck is way too tall but I don't think I can do much for that without rebuilding the frame from the firewall forward.

Anything jump out as immediately an issue?

 

[Treefrog]

My turn?

I have a 1st gen Taco reg cab 3RZ with an old Trail Gear 3 link kit on it. Use case is southeastern trail rig that is going to see interstates to get to and from the woods. I'm at least the 3rd owner since it was built almost 20 years ago, and I was told the axle was "folded under" the truck. The upper link is 6" longer than the lowers and looks like it's been sleeved, so who knows how all this came to be. It drives like crap on the road, and I really want to make it be less bad. I don't think "good" is in the cards, so I'm happy to settle for that.

The rear is leaf sprung.

Here's what I measured today:

I'm kinda limited on what I can do with the frame side brackets. The frame side panhard bracket is potentially moveable, but I really don't want to mess with the link brackets on the frame.

My current plan is to shorten the upper link to bring the pinion angle down (it's pointing well above the tcase output) and to add a little more positive caster, but beyond that I'm not really sure how to make this be less bad. From what I've read here my AD numbers are way too high. The truck is way too tall but I don't think I can do much for that without rebuilding the frame from the firewall forward.

Anything jump out as immediately an issue?

Any specifics about how the street driving is bad?

I suspect that you are underestimating the weights.

Antis do seem high, and the roll axis has way more oversteer than what is normally suggested.

Unfortunately, I think the most improvement will come from lowering the frame lowers and moving them in slightly

 

[thezentree]

Any specifics about how the street driving is bad?

I suspect that you are underestimating the weights.

Antis do seem high, and the roll axis has way more oversteer than what is normally suggested.

Unfortunately, I think the most improvement will come from lowering the frame lowers and moving them in slightly

I don't have a ton of seat time in it, but it was darty and loose, and has a ton of body roll. I'm sure adding caster will help with the dartiness. This is not really applicable to street driving, but it also wants to drive over the front axle if I hit the brakes in low-low.

You're probably right about weights. I spent about 5 seconds on making guesses there.

It sounds like there's not a whole lot I can do to make big improvements that aren't in "part it out and start over with a clean truck" territory. Oh well, thanks.

 

[girvin]

Hey there! this is my first post so if I am not doing this right let me know. I have a 2008 f450 CandC I am just finishing a cummins swap on. Running super singles and 38s. I want this truck for a few things. Daily driver / overland rig with a camper / welding rig for hurrican response and beach rig for surfing. So needs good street manners and good sand and fire road ability. I plan to runs ome 2.5 shocks all the way around. I want to build a 5 link suspension with airbags. I did the parallel bars then someone that know more then me said to make instant center point at the rear of the engine so I redid that in the calculator. So how are my nuimbers for use case? They will change a bit as I level the front and put the 38s on.

 

[girvin]

Also I havent done the front suspension so please ignore that.

 

[Treefrog]

Hey there! this is my first post so if I am not doing this right let me know. I have a 2008 f450 CandC I am just finishing a cummins swap on. Running super singles and 38s. I want this truck for a few things. Daily driver / overland rig with a camper / welding rig for hurrican response and beach rig for surfing. So needs good street manners and good sand and fire road ability. I plan to runs ome 2.5 shocks all the way around. I want to build a 5 link suspension with airbags. I did the parallel bars then someone that know more then me said to make instant center point at the rear of the engine so I redid that in the calculator. So how are my nuimbers for use case? They will change a bit as I level the front and put the 38s on.

Do you mind sharing the blue box at the top with biases and weights?

My first reaction is that you have a couple of conflicting uses. It seems like street behavior is the primary goal? Overlanding is not far off from that, but I don't know how well that will play with beach use.

From what I can tell, you will probably want to get the anti squat lower and probably lower the roll axis angle. It may benefit from a longer panhard bar to keep the side to side movement down.

 

[girvin]

hey tree frog Thanks yeah I moved a couple of things around on the calculator just trying to learn I will take a couple of new pics. Yes street manners and soft roading / overlanding would be good. The sand thing is I see heavy trucks get wheel hop in the sand and get buried My gx470 does an amazing job in the sand but is only 4500 lbs. Basically we want to be able to do light trails and drvie deep sand on the beaches going to surf spots and still handle great on the road. Thanks for all your advice!

 

[Treefrog]

hey tree frog Thanks yeah I moved a couple of things around on the calculator just trying to learn I will take a couple of new pics. Yes street manners and soft roading / overlanding would be good. The sand thing is I see heavy trucks get wheel hop in the sand and get buried My gx470 does an amazing job in the sand but is only 4500 lbs. Basically we want to be able to do light trails and drvie deep sand on the beaches going to surf spots and still handle great on the road. Thanks for all your advice!

From what I can find about designing suspension for soft sand, it seems that anti squat lower than typical for crawlers is recommended to keep from hopping. You will loose some bite from that. That sort of suspension geometry will provide an okay ride while overlanding.

 

[girvin]

so it looks good but I should get my anti squat lower?

 

[girvin]

I actually sent the wrong pics dangit

 

[Treefrog]

so it looks good but I should get my anti squat lower?

Antis lower and roll slope flatter. Raising the axle end of the lowers will help with both.

 

[girvin]

Here is my updates

 

[reclineaholic]

Treefrog, thanks for all the effort you have put into the calculator and answering all the questions. I've been trying different numbers on the calculator for a portal buggy that I'm building and I have the results attached. I haven't been able to get the roll slopes much closer to neutral without killing the anti's. Will this drive bad? It's a portal, rock crawler, trail only, rig that will not be driven fast, I want it to be the best that it can be on steep hills with ledges, some of the hills will have loose dirt and rocks requiring tire speed and some will be solid rock, I'll also be crawling boulders. I'm trying to keep the lower links like they are so they will be even with the bottom of the axle housings and the belly skid. Your advice would be much appreciated.

 

[Treefrog]

Treefrog, thanks for all the effort you have put into the calculator and answering all the questions. I've been trying different numbers on the calculator for a portal buggy that I'm building and I have the results attached. I haven't been able to get the roll slopes much closer to neutral without killing the anti's. Will this drive bad? It's a portal, rock crawler, trail only, rig that will not be driven fast, I want it to be the best that it can be on steep hills with ledges, some of the hills will have loose dirt and rocks requiring tire speed and some will be solid rock, I'll also be crawling boulders. I'm trying to keep the lower links like they are so they will be even with the bottom of the axle housings and the belly skid. Your advice would be much appreciated.

I put some info regarding antis and portals in the link suspension bible not too long ago. The calculator is not currently set up to calculate antis for portals. Are you using rotation reversing portals? And at what ratio?

For a crawler, roll slopes are fairly low on the priority list. But as a prediction you will likely have quite a bit of roll steer. From the conventional view of roll stuff, you should have fairly low body roll when off camber given the height of your roll centers.

It looks like it will crawl like other comparable rigs.

 

[reclineaholic]

I put some info regarding antis and portals in the link suspension bible not too long ago. The calculator is not currently set up to calculate antis for portals. Are you using rotation reversing portals? And at what ratio?

For a crawler, roll slopes are fairly low on the priority list. But as a prediction you will likely have quite a bit of roll steer. From the conventional view of roll stuff, you should have fairly low body roll when off camber given the height of your roll centers.

It looks like it will crawl like other comparable rigs.

Thanks Treefrog, they are humvee portals so rotation reversing, 1.91 to 1 gear reduction. I did a Ctrl F search of the link suspension bible for "portals" and it seems like your opinion of how the torque from the portals translates to the chassis through the links is still fluid. I'm thinking about how we used to check motor mounts in a 2 wheel drive car; hold the brake, put it in drive, and give some gas, the left side motor mount stretches and the right side compresses; put it in reverse and give some gas, and the right side motor mount stretches, the left side compresses. It doesn't matter which way the crankshaft turns it just matters which way the output shaft turns. I'm probably oversimplifying this and I don't claim to have any knowledge about forces in link suspensions but I think your calculator has to be at least ball park right for the anti's and I really have no choice but to use them since there is nothing else out there. I appreciate the info on the roll slopes and the roll centers and I think your 4 link calculator is awesome, thanks again for making it!

 

[Treefrog]

Thanks Treefrog, they are humvee portals so rotation reversing, 1.91 to 1 gear reduction. I did a Ctrl F search of the link suspension bible for "portals" and it seems like your opinion of how the torque from the portals translates to the chassis through the links is still fluid. I'm thinking about how we used to check motor mounts in a 2 wheel drive car; hold the brake, put it in drive, and give some gas, the left side motor mount stretches and the right side compresses; put it in reverse and give some gas, and the right side motor mount stretches, the left side compresses. It doesn't matter which way the crankshaft turns it just matters which way the output shaft turns. I'm probably oversimplifying this and I don't claim to have any knowledge about forces in link suspensions but I think your calculator has to be at least ball park right for the anti's and I really have no choice but to use them since there is nothing else out there. I appreciate the info on the roll slopes and the roll centers and I think your 4 link calculator is awesome, thanks again for making it!

The change in housing torque is not fluid. The issue comes with the calculator not yet being able to account for how portals move the start of the line for antis. Overall I would not worry about it much. The antis with portals get closer to the antis without as the rear takes a higher percent of the drive bias.

 

[reclineaholic]

The change in housing torque is not fluid. The issue comes with the calculator not yet being able to account for how portals move the start of the line for antis. Overall I would not worry about it much. The antis with portals get closer to the antis without as the rear takes a higher percent of the drive bias.

OK, does that mean that if I select a lower front drive bias the rear anti squat will be closer to right?

 

[Treefrog]

OK, does that mean that if I select a lower front drive bias the rear anti squat will be closer to right?

With my current understanding of antis, I think that the black line is the anti line. Without portals, it is the green line. Since your IC is located near the front axle's vertical plane, the difference between the two is quite small.

I would not worry about it to much. Your suspension looks like it will preform like most comparable buggies.

 

[reclineaholic]

With my current understanding of antis, I think that the black line is the anti line. Without portals, it is the green line. Since your IC is located near the front axle's vertical plane, the difference between the two is quite small.

I would not worry about it to much. Your suspension looks like it will preform like most comparable buggies.

Thank you very much for your help! I plan on having a couple of adjustment holes on the upper link frame mount so I think I'm good to go.

 

[zerobalance]

Anyone care to give input on this, front axle numbers. It's a bit goofy but I'm building a VW bus so forward control, with the engine just behind the front axle. I'm a complete rookie. Toyota axles and I am fabricating frame rails, so easy to manipulate the link locations. I think I'm within reason but not completely sure.

 

[Treefrog]

Anyone care to give input on this, front axle numbers. It's a bit goofy but I'm building a VW bus so forward control, with the engine just behind the front axle. I'm a complete rookie. Toyota axles and I am fabricating frame rails, so easy to manipulate the link locations. I think I'm within reason but not completely sure.

I highly recommend using one of the new versions. 5.x should work in google sheets.

You may want to double check all of you inputs.

Your wheel centerline is 12.75 in from the ground, your lower links are 4 inches above that. You have very little separation between the upper and lower links. Your panhard bar starts and ends on the same side of the vehicle, at the same point. The lower links end on the opposite side of the axle.

 

[zerobalance]

I highly recommend using one of the new versions. 5.x should work in google sheets.

You may want to double check all of you inputs.

Your wheel centerline is 12.75 in from the ground, your lower links are 4 inches above that. You have very little separation between the upper and lower links. Your panhard bar starts and ends on the same side of the vehicle, at the same point. The lower links end on the opposite side of the axle.

Many thanks. I thought I did have the newest version from the first page here. I will regroup. I missed fixing the tire height cell. I am slogging through the old place 3 link threads to gather as much information as possible to get this right the first time.

Thank you again.

 

[Treefrog]

Many thanks. I thought I did have the newest version from the first page here. I will regroup. I missed fixing the tire height cell. I am slogging through the old place 3 link threads to gather as much information as possible to get this right the first time.

Thank you again.

The 4 link calc. V4.0 and newer combined 4 link and panhard bar suspension tools.

The best advice I can give on 3 links is don't try to do the cancel out drive torque trick unless you know what you are doing.