How's my numbers?

[Treefrog]

Yes I'm going to move the front uppers at the axle to 7-9" separation. I just want the roll center closer to the CG to help control body roll. As for the IC I thought having them more stable would make the rig more predictable throughout the suspension cycle?

Raising the roll center will make it more prone to jacking, which on a tall rig is probably more scary. A lower RC means better handling but more roll. It would probably be better to fight the roll by outboarding the springs more and/or using a sway bar.

The IC moving isn't a big deal, because that line doesn't show that the tires are also moving. The anti plots are much better representation of that. And they look pretty stable. I could be wrong, but I don't recall antis affecting how well the vehicle tracks straight. More so how it it preforms in acceleration, and somewhat how it reacts to gas and brake in a corner.

 

[Broncofntc]

Raising the roll center will make it more prone to jacking, which on a tall rig is probably more scary. A lower RC means better handling but more roll. It would probably be better to fight the roll by outboarding the springs more and/or using a sway bar.

The IC moving isn't a big deal, because that line doesn't show that the tires are also moving. The anti plots are much better representation of that. And they look pretty stable. I could be wrong, but I don't recall antis affecting how well the vehicle tracks straight. More so how it it preforms in acceleration, and somewhat how it reacts to gas and brake in a corner.

I'm just going to widen the front uppers at the axle and run it some. I've been happy with it's trail manners. Thanks Treefrog

 

[Day215]

Not sure if this thread is dead or not, but here goes nothing. This is my first venture into linking the front of my rig.

Details: 92’ Toyota pickup, frame cut and raised at firewall, 26” to frame rail on 40’s, 119” WB, four seat family rig for crawling/camping, trailered to and from.

I’d like to get it lower but the current rear seat is sunk into the bed and would require reworking the rear leafs and fuel cell a considerable amount, so it has to stay at 26” belly height for now.

Bump

 

[Day215]

Droop

 

[Treefrog]

Not sure if this thread is dead or not, but here goes nothing. This is my first venture into linking the front of my rig.

Details: 92’ Toyota pickup, frame cut and raised at firewall, 26” to frame rail on 40’s, 119” WB, four seat family rig for crawling/camping, trailered to and from.

I’d like to get it lower but the current rear seat is sunk into the bed and would require reworking the rear leafs and fuel cell a considerable amount, so it has to stay at 26” belly height for now.

Bump

It's not dead yet.

Remember to account for joint size when working around a frame.

Doesn't look too bad. Roll slope is a little on the steep side, especially since its oversteer. AD is a little high as well. From a travel perspective, it has a fair bit of pinion angle change. Which means it has quite a bit of caster change. If it only sees low speed, probably not that big of a deal.

I recommend using the most recent version of the calculator. It can be found under the resources page.

 

[Day215]

It's not dead yet.

Remember to account for joint size when working around a frame.

Doesn't look too bad. Roll slope is a little on the steep side, especially since its oversteer. AD is a little high as well. From a travel perspective, it has a fair bit of pinion angle change. Which means it has quite a bit of caster change. If it only sees low speed, probably not that big of a deal.

I recommend using the most recent version of the calculator. It can be found under the resources page.

I downloaded the newest version. It’s kind of throwing me for a loop with all the new variables. I tweaked a few things and I’ll repost the new screenshots once I’m done.

 

[Day215]

Here are my revised numbers, along with the newest version of the calculator.

 

[Treefrog]

Here are my revised numbers, along with the newest version of the calculator.

Doesn't look too bad. Pinion is better, but the its going to have quite a bit of oversteer.

 

[Day215]

Doesn't look too bad. Pinion is better, but the its going to have quite a bit of oversteer.

Any way to correct it? What effect would it have when driving it?

 

[Treefrog]

Any way to correct it? What effect would it have when driving it?

I don't think you can get to understeer without bigger changes. But you can flatten the roll slope some by narrowing the lower frame mounts.

As is, the front suspension will want to steer tighter than it is being told to as the body rolls. Faster you go the more it will show up.

 

[Day215]

I don't think you can get to understeer without bigger changes. But you can flatten the roll slope some by narrowing the lower frame mounts.

As is, the front suspension will want to steer tighter than it is being told to as the body rolls. Faster you go the more it will show up.

I’m starting to get a grasp on it now. I appreciate the input. I can push my lower frame side mounts inboard a bit more. I guess it’s just time to build it.

 

[Treefrog]

I’m starting to get a grasp on it now. I appreciate the input. I can push my lower frame side mounts inboard a bit more. I guess it’s just time to build it.

It might help to think about it as a non-steering and if the wheel going forward or backward when it moves up and down. If one is moving forward and the other backward, the axle will be pointing a different direction.

Only other advice is to make sure your caster is at least enough that it never crosses vertical. Probably with some padding built in.

 

[Day215]

It might help to think about it as a non-steering and if the wheel going forward or backward when it moves up and down. If one is moving forward and the other backward, the axle will be pointing a different direction.

Only other advice is to make sure your caster is at least enough that it never crosses vertical. Probably with some padding built in.

It sounds like the roll oversteer becomes an issue at droop? I’m trying to get a handle on which way my caster would rotate. Currently, caster is set to about 4 degrees. That’s what Dodge specs for the axle and also happens to be about as much as I can get while still keeping the truss mostly level.

I I needed to add more caster, the truss would need to roll toward the front of the axle but can’t since it runs into the webbing on the housing.

 

[Treefrog]

It sounds like the roll oversteer becomes an issue at droop? I’m trying to get a handle on which way my caster would rotate. Currently, caster is set to about 4 degrees. That’s what Dodge specs for the axle and also happens to be about as much as I can get while still keeping the truss mostly level.

I I needed to add more caster, the truss would need to roll toward the front of the axle but can’t since it runs into the webbing on the housing.

Roll slope affects how it turns. If both tires are drooped the same amount, it won't have an effect. Oversteer and understeer are much more of a ride height thing than a full bump or droop thing.

In the front pinion up will decrease caster, pinion down will increase it. It may be close, but you will probably have enough at 4 degrees. Especially if you don't plan to do desert racing.

 

[Diezl]

Drive and brake bias. V3 is all power at the end of the vehicle being looked at. V4+ it is adjustable. The values were 50% drive and 60% brake in the most recent version when it was uploaded. They are in the center column of inputs, towards the top.

Thanks! it was messing with me. I may have to tuck in my lowers at the axle a little as the tires will rub on the links at full lock. That seems to increase the roll slope a degree or so. I just included the front as the rear has been done for a couple years now.

 

[Treefrog]

Thanks! it was messing with me. I may have to tuck in my lowers at the axle a little as the tires will rub on the links at full lock. That seems to increase the roll slope a degree or so. I just included the front as the rear has been done for a couple years now.

It may be better to get the AD below 100%. My understanding is that things can get wheel hoppy when the drive bias causes it to cross over that line.

What's the use of the rig?

 

[Diezl]

It may be better to get the AD below 100%. My understanding is that things can get wheel hoppy when the drive bias causes it to cross over that line.

What's the use of the rig?

I believe its 65%? When i mess with the drive bias the anti lift changes, do i keep it at 50%?
Its mostly rock crawling and trail riding

 

[Treefrog]

I believe its 65%? When i mess with the drive bias the anti lift changes, do i keep it at 50%?
Its mostly rock crawling and trail riding

Sorry meant AL. Drive bias changes constantly on and off road with awd/4wd. Drive and brake bias are part of the anti formula.

50 is an okay number to leave it at. Just be aware that it can move between all front and all rear on the trail.

 

[Diezl]

Sorry meant AL. Drive bias changes constantly on and off road with awd/4wd. Drive and brake bias are part of the anti formula.

50 is an okay number to leave it at. Just be aware that it can move between all front and all rear on the trail.

Ok since im not familiar yet with this version vs V3. 100% AL or AS is kind of neutral correct? but should i be looking or trying to get at that number with 50% bias or 100%? I set my rear AS to 75% with V3 and was very happy with how it works.

 

[Treefrog]

Ok since im not familiar yet with this version vs V3. 100% AL or AS is kind of neutral correct? but should i be looking or trying to get at that number with 50% bias or 100%? I set my rear AS to 75% with V3 and was very happy with how it works.

Neutral is a bad way to put it but yes. At 100% the suspension does not move in reaction to throttle or brake. Instead it causes the suspension to stiffen.

V3 has 100% rear drive bias. That means that whatever the AS is is the highest it will be at that given travel point.

You will have to decide what bias you want to design around. 100 bias is the edge case. 50% would be more realistic.

That said, brake bias affects antidive and rear antilift. Drive bias affects antisquat and front antilift.

 

[Diezl]

Neutral is a bad way to put it but yes. At 100% the suspension does not move in reaction to throttle or brake. Instead it causes the suspension to stiffen.

V3 has 100% rear drive bias. That means that whatever the AS is is the highest it will be at that given travel point.

You will have to decide what bias you want to design around. 100 bias is the edge case. 50% would be more realistic.

That said, brake bias affects antidive and rear antilift. Drive bias affects antisquat and front antilift.

thanks for taking the time to explain to me. Anything else that i could try to improve? Im fairly limited but i could move things slightly.

 

[Treefrog]

thanks for taking the time to explain to me. Anything else that i could try to improve? Im fairly limited but i could move things slightly.

Pinion angle is probably the big one, but its probably not a big concern if caster goes goes past 0 at crawl or slow trail speeds. Same goes for roll slope, not the best, but should be fine for crawling and trail. Keeping the antis below 100% through travel is probably a god idea as well if possible.

 

[drozg]

These are my numbers for the racing buggy I am planing to build, it would have portal axles, front lower leading arm suspension and rear upper trailing arm suspension. It will be used for European trophy raid races and that includes 40 % of fast forest driving so I need very accurate car and 60 % of forest climbing (roots,mud etc.) , the only thing that wories me is the rear roll center change through travel, is that a problem ? If for example blasting through the forest and hitting a bump on driver side rear, would that push the chassis up and try to roll me over, or will it still articulate freely?
Is there any other thing you would change?
Thanks

 

[Treefrog]

These are my numbers for the racing buggy I am planing to build, it would have portal axles, front lower leading arm suspension and rear upper trailing arm suspension. It will be used for European trophy raid races and that includes 40 % of fast forest driving so I need very accurate car and 60 % of forest climbing (roots,mud etc.) , the only thing that wories me is the rear roll center change through travel, is that a problem ? If for example blasting through the forest and hitting a bump on driver side rear, would that push the chassis up and try to roll me over, or will it still articulate freely?
Is there any other thing you would change?
Thanks View attachment 495090 View attachment 495091 View attachment 495092

I don't really know about the rear roll center. Higher means body rolls less, but also reduces handling.

Maybe add some more convergence ange to the rear? Especially if racing. 40 is considered the minimum acceptable. And maybe try to get more pinion angle change in the rear? Keeps the u-jount angle down. Maybe flatten the front anti curves some? Decreasing with travel has it's pros and cons.

 

[drozg]

I don't really know about the rear roll center. Higher means body rolls less, but also reduces handling.

Maybe add some more convergence ange to the rear? Especially if racing. 40 is considered the minimum acceptable. And maybe try to get more pinion angle change in the rear? Keeps the u-jount angle down. Maybe flatten the front anti curves some? Decreasing with travel has it's pros and cons.

Thank you very much for advices.
Adding more triangulation at rear lower links will result in droping rear roll center bellow the front roll center, which is not optimal, if I am not mistaken? But uppers must stay straight because it is upper trailing arm suspension setup.
With front anti curves you mean anti dive change through travel?
You have any idea what causes such a high roll center deviation through travel or how to fix it?

 

[Treefrog]

Thank you very much for advices.
Adding more triangulation at rear lower links will result in droping rear roll center bellow the front roll center, which is not optimal, if I am not mistaken? But uppers must stay straight because it is upper trailing arm suspension setup.
With front anti curves you mean anti dive change through travel?
You have any idea what causes such a high roll center deviation through travel or how to fix it?

A bit of oversteer is fine on race rigs usually. And the body roll slope isn't the only factor in oversteer vs understeer. Its more important for streetable rigs to have understeer so that you have to worry less about who drives it.

Yeah, change through travel.

Usually you want to triangulate links with shock mounted to them such that the shock mount on the link is always on the outside of the chassis shock mount.

The cause of the moving roll center is that the Y values at the axle are both high. The closer the upper or lower link ends are to each other at the axle the less it moves in travel. What's happening is that the points where the a pair of links would cross moves with travel. The closer that point is to the axle end of the links, the closer it is to fixed in position relative to the axle. Roll center as plotted is relative to the bottom of the tires not the chassis.

There are some disadvantages to it, but having the lowers converge at the axle and the uppers at the frame has been done. As for cons, risk of having a link catch on something, risk of funneling rocks to a centered rear diff, possible tendency to put more of the acceleration load on the outside tire leaving a corner.

 

[drozg]

A bit of oversteer is fine on race rigs usually. And the body roll slope isn't the only factor in oversteer vs understeer. Its more important for streetable rigs to have understeer so that you have to worry less about who drives it.

Yeah, change through travel.

Usually you want to triangulate links with shock mounted to them such that the shock mount on the link is always on the outside of the chassis shock mount.

The cause of the moving roll center is that the Y values at the axle are both high. The closer the upper or lower link ends are to each other at the axle the less it moves in travel. What's happening is that the points where the a pair of links would cross moves with travel. The closer that point is to the axle end of the links, the closer it is to fixed in position relative to the axle. Roll center as plotted is relative to the bottom of the tires not the chassis.

There are some disadvantages to it, but having the lowers converge at the axle and the uppers at the frame has been done. As for cons, risk of having a link catch on something, risk of funneling rocks to a centered rear diff, possible tendency to put more of the acceleration load on the outside tire leaving a corner.

Thank you very much Sir. Appreciate all the help!

 

[Harleybarnes19]

First time using the new calculator and looking for opinions! Just now I noticed that it’d be good to have less pinion angle change but not sure if it’s possible.
All measurements are taken at full bump. Should I change the measurements for ride height?

 

[Treefrog]

First time using the new calculator and looking for opinions! Just now I noticed that it’d be good to have less pinion angle change but not sure if it’s possible.
All measurements are taken at full bump. Should I change the measurements for ride height?

What's the use of the rig?
Edit: Mind reposting the plots with "highlighted value" set to the ride hide?

 

[Harleybarnes19]

What's the use of the rig?
Edit: Mind reposting the plots with "highlighted value" set to the ride hide?

It’s mainly for rock crawling, AOP. May see the road going to the gas station and such. It’s a tj on tons. I did 2 different locations for upper link on the frame and have both. The unsprung weight is a guesstimate, I can’t tell what the cage is made of, looks store bought.