How's my numbers?

[Treefrog]

looking for second opinion on this for my current buggy set up. Front and rear are almost the same numbers so not sure if having my anti squat/anti dive numbers in the mid 40s is good as was always under the impression closer to 100 was better. so flame away as it is tuesday

In version 3.0 and 3.1 of the calc, 50% is a good max value for the anti squat. The numbers look fine at ride height, but I suspect that they get a bit out of hand as the suspension cycles.

 

[Snowracer]

In version 3.0 and 3.1 of the calc, 50% is a good max value for the anti squat. The numbers look fine at ride height, but I suspect that they get a bit out of hand as the suspension cycles.

what do you mean out of hand? and any recommendations on changes to make to improve it ?

 

[Treefrog]

what do you mean out of hand? and any recommendations on changes to make to improve it ?

They will likely change quite a bit, and not for the better. Shortening the upper helps.

It's a bit of an inconvenience to transfer over, but the newer versions show multiple points of travel at the same time. See post 1 for the link

 

[Snowracer]

pretty hard to shorten my uppers with how everything is on my chassis. on the front the uppers are actually 1 inch longer then the lowers

put the numbers in the new version and my anti squat/dive number are even lower and what really stands out is my pinion angle changes through travel. if i move my frame uppers higher it makes the pinon angle change better but the anti squate/dive into the teens and negative at travel

 

[Treefrog]

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pretty hard to shorten my uppers with how everything is on my chassis. on the front the uppers are actually 1 inch longer then the lowers

put the numbers in the new version and my anti squat/dive number are even lower and what really stands out is my pinion angle changes through travel. if i move my frame uppers higher it makes the pinon angle change better but the anti squate/dive into the teens and negative at travel

They are lower because the point at which it is checked is closer to the rear axle for antisquat. Its the drive bias and braking bias. The rear doesn't look too bad. Through AS increasing in bump is better.

The front looks like it may be an issue. My guess is that moving the front upper frame points closer to the axle will help get it more consistent throughout travel.

 

[Yellow4r4]

This is my stretched 3" front and 12" rear JK with 4 link rear and 3 link front. I can't raise the front or rear upper mounts anymore do to the body. and lowers put the bottom edge of the joint flush with the skid plate. I was trying to keep all the Arms roughly the same length so I would only have to carry one spare. Any thoughts?

 

[Treefrog]

This is my stretched 3" front and 12" rear JK with 4 link rear and 3 link front. I can't raise the front or rear upper mounts anymore do to the body. and lowers put the bottom edge of the joint flush with the skid plate. I was trying to keep all the Arms roughly the same length so I would only have to carry one spare. Any thoughts?

The biggest things are the decreasing antis as the suspension compresses and the very little little front up travel in comparison to the rear's ~50% travel bias.

On an unrelated note, in cell K14, change F_Upper_Link to R_Upper_Link, and visa versa in cell K15. Not sure how I missed that when I added that feature.

 

[Yellow4r4]

The biggest things are the decreasing antis as the suspension compresses and the very little little front up travel in comparison to the rear's ~50% travel bias.

On an unrelated note, in cell K14, change F_Upper_Link to R_Upper_Link, and visa versa in cell K15. Not sure how I missed that when I added that feature.

I was originally trying to use the same length arms everywhere because that's what a lot of people's look like. But after you pointed out the drastically decreasing antis I think this looks better. As for the front up travel, that was just what it had without any stretch and a basic 4" lift with shocks in the stock location. I'll rework those numbers when I can see how far up it can go after the stretch. Thanks!

 

[Mouse]

I am working on a rig that has terrible road manners. This vehicle has a triangulated 4-link front and rear, using coilovers and a double-ended ram for steering. I suspect most of the trouble is within the front suspension, but I'm starting at the rear as it seems this rig pulls the front end up under acceleration. The rear suspension is using 4-link frame brackets from Poly Performance.

I've punched the suspension numbers into the Crawlpedia 4-link calculator and it gives me a 96% antisquat (pic below). In version 6.1 of your calculator I see a chart that graphs these values - how does this compare to the Crawlpedia calculator and does it suggest that adjustments are needed to improve the rear antisquat? (pic below)

View attachment

Version 6.1:

 

[Treefrog]

The values in the black circle are the ride height values. This is the same as the values at 0 travel in the chart(s). The values in the purple circle are are the values at a given travel. This is reported as the curve in the charts.

Since you said road manners, is it safe to assume that you mean rwd operation? If so, then you need to change drive bias to 100% rear.

What other bad behavior does it have besides front wants to lift under acceleration?

 

[Mouse]

Yes, for road use it is 2wd operation. I will change the drive bias to account for this.

The worst behavior is wandering, left-to-right, back and forth. It is very difficult to maintain a straight line at anything over about 35 mph. When the front lifts under acceleration the wander is worse. I believe this is a product of the caster being reduced as the front end unloads. At ride height, caster is approximately 5.2 degrees.

I have completed the measurements for the front 4-link, but will wait until I complete adjustment of the rear before moving on.

 

[Treefrog]

Yes, for road use it is 2wd operation. I will change the drive bias to account for this.

The worst behavior is wandering, left-to-right, back and forth. It is very difficult to maintain a straight line at anything over about 35 mph. When the front lifts under acceleration the wander is worse. I believe this is a product of the caster being reduced as the front end unloads. At ride height, caster is approximately 5.2 degrees.

I have completed the measurements for the front 4-link, but will wait until I complete adjustment of the rear before moving on.

It sounds more like a front end steering issue than a rear end issue.

 

[Mouse]

The rear end is sagging a bit as the springs on the coilovers are over 10 years old. I think we will just be changing them out for new units.

Time to move to the front. The front frame brackets are Artec 4-link pieces cut into the frame. They sit high in the frame. The front upper links are bent to clear the engine. I'm confident that I can build new links that are straight and add better adjustability, but the upper frame brackets will need to be separate of the lower link bracket.

After running the numbers (below) it looks like the best course may to be to cut the the lower link brackets out and weld the new ones at a lower position (in addition to new upper placement).

Open to suggestions - I appreciate comments & help. Following new link brackets I need to rotate the front axle to add caster.

 

[Treefrog]

The rear end is sagging a bit as the springs on the coilovers are over 10 years old. I think we will just be changing them out for new units.

Time to move to the front. The front frame brackets are Artec 4-link pieces cut into the frame. They sit high in the frame. The front upper links are bent to clear the engine. I'm confident that I can build new links that are straight and add better adjustability, but the upper frame brackets will need to be separate of the lower link bracket.

After running the numbers (below) it looks like the best course may to be to cut the the lower link brackets out and weld the new ones at a lower position (in addition to new upper placement).

Open to suggestions - I appreciate comments & help. Following new link brackets I need to rotate the front axle to add caster.

Just from a quick glance, you have oversteer tendencies front, rear, and body. This is probably a big factor in the wander. Toe and caster probably play a role. As the rig squats, the caster is increasing.

 

[Mouse]

Any recommendations to reduce the oversteer?

 

[Treefrog]

Any recommendations to reduce the oversteer?

Move links around front and rear

 

[Mooseknuckled]

I could use some help running some final numbers before burning in my mounts. This is a dedicated trail buggy with 5.3, th400, atlas, 60's, on 40" reds etc. I've lowered it about 6" or so and I'm trying to keep it a low and slow crawler, but wouldn't mind being able to cruise through the desert comfortably. I haven't changed anything on the rear suspension other than coil springs and i'll be adding a sway bar. I've basically cut off and re-tubed everything from the firewall forward so the front suspension will be brand new. I'm guessing on overall weight but everything should be close? I also run water in the front tires. This is my first run with the 6.2 calculator so I'm sure I screwed something up
Thanks for any help!

 

[Treefrog]

I could use some help running some final numbers before burning in my mounts. This is a dedicated trail buggy with 5.3, th400, atlas, 60's, on 40" reds etc. I've lowered it about 6" or so and I'm trying to keep it a low and slow crawler, but wouldn't mind being able to cruise through the desert comfortably. I haven't changed anything on the rear suspension other than coil springs and i'll be adding a sway bar. I've basically cut off and re-tubed everything from the firewall forward so the front suspension will be brand new. I'm guessing on overall weight but everything should be close? I also run water in the front tires. This is my first run with the 6.2 calculator so I'm sure I screwed something up
Thanks for any help!

Looks good for the most part, some may want to try to get the overall roll slope to be positive for understeer. Regarding water in the tires, change the cg height to get the body cg to be accurate.

 

[ryanw10]

I just measured numbers from my Jeep TJ and plugged them into the new calculator. I have overall been happy with how it handles on and off road.

 

[BioHazard2222]

OK if I throw some numbers up for feedback and help with my numbers?
I have been working on seeing if I can get a good set of numbers to incorporate in my Tube Buggy build.
The Panhard bar may need to be adjusted some, I haven't got all the mounting details worked out yet for the steering box, but I think I can get close to what I have there.
I did have to bring the rear upper axle ends back and down a bit to get the numbers where I think they should be, this is due to the height of the truss on my 14bolt
This will be mostly just a Trail Rig.
Let me know your thoughts, look OK? of need changing?

 

[Treefrog]

OK if I throw some numbers up for feedback and help with my numbers?
I have been working on seeing if I can get a good set of numbers to incorporate in my Tube Buggy build.
The Panhard bar may need to be adjusted some, I haven't got all the mounting details worked out yet for the steering box, but I think I can get close to what I have there.
I did have to bring the rear upper axle ends back and down a bit to get the numbers where I think they should be, this is due to the height of the truss on my 14bolt
This will be mostly just a Trail Rig.
Let me know your thoughts, look OK? of need changing?

The tings that stick out are the AS crossing over 100%, but given that it is fairly far into down travel and in rwd, it should be fine. The rear over steer tendency. And the front upper is better suited on the same side as the axle panhard mount. The vehicle roll slope looks good, but with any travel (pitch) it may change. The last plot down below the panhard views that shows the roll center heights on the same plot should provide some insight. The front lower links seem a bit short given the length of the uppers. Given what you are planning to build, the 4000lbs doesn't seem all that accurate.

Also run the numbers at 50% drive bias and 100% front bias to get a sense for what happens in different conditions.

 

[BioHazard2222]

The tings that stick out are the AS crossing over 100%, but given that it is fairly far into down travel and in rwd, it should be fine. The rear over steer tendency. And the front upper is better suited on the same side as the axle panhard mount. The vehicle roll slope looks good, but with any travel (pitch) it may change. The last plot down below the panhard views that shows the roll center heights on the same plot should provide some insight. The front lower links seem a bit short given the length of the uppers. Given what you are planning to build, the 4000lbs doesn't seem all that accurate.

Also run the numbers at 50% drive bias and 100% front bias to get a sense for what happens in different conditions.

Thanks Treefrog for feedback.
I did some changes that brought rear oversteer down a bit and the front link lengths...
I bumped up vehicle mass to 4500, just a guess at this point, same as the front and rear unsprung mass numbers... I am just guessing, you think I'm close based on what you have seen?
When you said " front upper is better suited on the same side as the axle panhard mount" I guess I wasn't sure what you meant by that, I brought the Panhard back to over the front axle, but I don't think that was what you were talking about. Can you explain?
and I ran same numbers with the 50% drive Basis, results in lower image... they look right?

I really appreciate your input and help on this, I guess I can look at all the numbers and graphs, and I have read a bunch about anti-squat, anti-dive etc, but for some reason not wrapping my head around it.

 

[Treefrog]

Thanks Treefrog for feedback.
I did some changes that brought rear oversteer down a bit and the front link lengths...
I bumped up vehicle mass to 4500, just a guess at this point, same as the front and rear unsprung mass numbers... I am just guessing, you think I'm close based on what you have seen?

This weight seems accurate for a rig loaded with camping gear. Unsprung mass numbers can be estimeated by adding the tire, wheel and axle weight. Add some in the rear and more in the front to account for brackets and steering.

When you said " front upper is better suited on the same side as the axle panhard mount" I guess I wasn't sure what you meant by that, I brought the Panhard back to over the front axle, but I don't think that was what you were talking about. Can you explain?

The axle ends of the the panhard and single upper link work best when both are on the passenger side. Portal axles are a bit different but that's a discussion for a later time.

The effect of locating them as such is reduced or eliminated torque roll at that end axle.

and I ran same numbers with the 50% drive Basis, results in lower image... they look right?

All it would do is reduce the anti-squat by 50% and give some anti-lift to the front. 50% drive bias is roughly equivalent to getting on the gas for the run up to a loose climb. 100% rear drive bias is roughly how it will behave when all the weight is on the rear during a climb.

I really appreciate your input and help on this, I guess I can look at all the numbers and graphs, and I have read a bunch about anti-squat, anti-dive etc, but for some reason not wrapping my head around it.

Anti-squat, anti-lift, ant-squat are the percentage of load transfer from acceleration carried by the links or control arms instead of the springs.

 

[BioHazard2222]

The axle ends of the the panhard and single upper link work best when both are on the passenger side. Portal axles are a bit different but that's a discussion for a later time.

Thank you again Treefrog, ill do a bit more work on this and see where we end up.
Is there a way to tell the Calc to show the upper link on the passenger side? by default it shows up on drivers side.

 

[Treefrog]

Thank you again Treefrog, ill do a bit more work on this and see where we end up.
Is there a way to tell the Calc to show the upper link on the passenger side? by default it shows up on drivers side.

Yeah, just use negative y? values. I don't believe there is a restriction on using negative on that input.

 

[ryanw10]

Could I get some input on the rear 4 link shown below for a Jeep JK? The front 3 link is already welded in place so nothing can be changed there.

 

[Treefrog]

Could I get some input on the rear 4 link shown below for a Jeep JK? The front 3 link is already welded in place so nothing can be changed there.

Overall, not bad. Cg seems a bit high, that will change the antis some. Also the body all three roll axis are oversteer or neutral. Not necessarily a bad thing, but can be a problem if an unaware drive gets behind the wheel.

 

[93blackxj]

Here are my numbers for a buggy that I have been designing. This will be a trail buggy that I would eventually like to race. So when designing the suspension I based a lot of it on keeping the pinion change to a minimum while keeping the angles around 20 degrees to run 1350 joints all around and keep driveline vibrations to a minimum. The only problem that this caused is that antis drastically decreases as suspension travels to full bump due to my upper links being longer than lowers to limit pinion angle change. I shortend the length of the belly a little bit to increase the length of my lowers and this helped some. I know I have seen tree mention that it is possible to accomplish this without making antis squat decrease through bump but I cant seem to figure out how. Any input would be appreciated. I also have +/- 1" in the uppers at the frame for the rear

 

[Treefrog]

Here are my numbers for a buggy that I have been designing. This will be a trail buggy that I would eventually like to race. So when designing the suspension I based a lot of it on keeping the pinion change to a minimum while keeping the angles around 20 degrees to run 1350 joints all around and keep driveline vibrations to a minimum.

Pinion angle change is not necessarily a bad thing. In the rear it helps keep the angle at the pinion lower since that is a single u-joint with limited deflection. It is unwanted up front because it changes caster. The other thing to consider is how often it is going to be at the point of max angle

The only problem that this caused is that antis drastically decreases as suspension travels to full bump due to my upper links being longer than lowers to limit pinion angle change. I shortend the length of the belly a little bit to increase the length of my lowers and this helped some. I know I have seen tree mention that it is possible to accomplish this without making antis squat decrease through bump but I cant seem to figure out how. Any input would be appreciated. I also have +/- 1" in the uppers at the frame for the rear

Moving the upper frames back so that the upper link is about 70-75% of the lower in 2d should help. Moving it along the link won't affect the ride values at all. Get it sorted in the side view then start going after roll stuff. Change one value at a time and see how it affects the curve.

It is possible to get a rising curve, but it took a lot of playing around with the values to get it figured out.

Just a warning about the lower frame Z values front and rear: That is the pivot point expect another 1.5 inches below that for the bracket and rod end.

 

[93blackxj]

Pinion angle change is not necessarily a bad thing. In the rear it helps keep the angle at the pinion lower since that is a single u-joint with limited deflection. It is unwanted up front because it changes caster. The other thing to consider is how often it is going to be at the point of max angle

Yeah thats what I was trying to accomplish in the rear was get the happy medium of least amount of pinion ujoint change but staying under 20 degrees or so. But after playing with the calculator and remembering where you said somewhere in one of these threads that pinion angle isnt necessarily determined by upper/lower link length its more about the chassis side mounting points relative to each other. Playing around with the calc, moving the uppers back or lowers forward seems to do about the same with the antis curve but doesnt effect my ujoint working angle much. Thanks for the tip.

Just a warning about the lower frame Z values front and rear: That is the pivot point expect another 1.5 inches below that for the bracket and rod end.

Yes i understand, I plan on having a belly height of around 17" or so with down travel bias then if i want to raise to 18" or so have a 50/50 split.