help with 3 link calculations

[SchrammMan74]

I am in the middle of a three link on my toyota tacoma and really wanted someone to look over my numbers before i make it final
it is a 2000 toyota tacoma with 37" tires dana44 front axle.
i have already completed the rear 4 link. just looking for some help
thanks

 

[BCGPER]

38.5 is all you need, just ask Carl.......



I'm no help.

 

[cheepin]

I could try if I could read it.lol

 

[SchrammMan74]

I know it's small let me see what i can do about that.. figured it out

 

[reddman]

Here's what I would start with:

As far as your anti-squat, I think anywhere near 100% is crazy high. First thing I would do is lower your ride height if at all possible. Then drop your lower link frame mounts a couple of inches, the handling improvements would be worth the loss in ground clearance in my opinion.

That will also net you a huge stability gain by lowering your roll axis angle. 10* positive will not give you any kind of predictable handling, it's a pretty bad number. The good news is that by lowering your ride height and lowers like I suggested earlier, it will also move that number in the right direction.

Your panhard rod is pretty steep too. I assume it's to match the angle and length of your existing drag link, which is of primary importance, but flatter and longer are things to shoot for if possible.

I plugged all your numbers in and got some much better numbers by making the following changes:

-Lower ride height by 2", lowering all frame side mounts and the COG.
-Bringing the lower link frame side mounts another 2.25" lower off the frame.

That would bring your AS down to a less reactive 31%, and improves your roll axis to 2.5*, not ideal, but tons better.

Your panhard is also waaaay out in front of the axle. If that's the only place you can fit it, fine, but it see's some pretty serious loading and is going to require a hell of a mount off the axle.


There's my 2 cents.

 

[SchrammMan74]

Here's what I would start with:

As far as your anti-squat, I think anywhere near 100% is crazy high. First thing I would do is lower your ride height if at all possible. Then drop your lower link frame mounts a couple of inches, the handling improvements would be worth the loss in ground clearance in my opinion.

That will also net you a huge stability gain by lowering your roll axis angle. 10* positive will not give you any kind of predictable handling, it's a pretty bad number. The good news is that by lowering your ride height and lowers like I suggested earlier, it will also move that number in the right direction.

Your panhard rod is pretty steep too. I assume it's to match the angle and length of your existing drag link, which is of primary importance, but flatter and longer are things to shoot for if possible.

I plugged all your numbers in and got some much better numbers by making the following changes:

-Lower ride height by 2", lowering all frame side mounts and the COG.
-Bringing the lower link frame side mounts another 2.25" lower off the frame.

That would bring your AS down to a less reactive 31%, and improves your roll axis to 2.5*, not ideal, but tons better.

Your panhard is also waaaay out in front of the axle. If that's the only place you can fit it, fine, but it see's some pretty serious loading and is going to require a hell of a mount off the axle.


There's my 2 cents.

as the truck sits now there is only ten inch's from the top of the axle to the bottom of the frame. i at most get 4.5 inch's of up travel. I am thinking the frame has to stay there at least.. If i loswered it 2 inchs i would only get 2 2.5 of up travel. My truck is already as low as i could like it.

I am trying to fit the panhard in above the axle. looks like i am going to have to bend it around the diff cover but it should fit.
thanks for your help though..

 

[reddman]

Damn that's a good lookin' truck!

Yeah, looks like you can't go any lower.

Well even still, dropping the lower link frame mounts 2.25" lower would greatly improve your AS to 46%, and bring your roll axis down to 6*. I would feel ok about that AS, but anything you can do to bring the roll axis down to zero or a little on the negative side will work wonders on how "floppy" it feels on corners and sidehills.

To improve the roll axis, I would play with lowering the panhard if at all possible, spreading the axle side lower link mounts wider, and bringing the axle side lower link mounts up to around centerline.

Sorry if I'm a little long winded with my responses, I just love talking suspension theory!

Good luck!

 

[Tacoma]

Sorry if I'm a little long winded with my responses, I just love talking suspension theory!

Good luck!

Good, I'll call you when it's time to link the Blazer.

 

[SchrammMan74]

thanks the truck started out as a budget truck that i bought rolled and with a salvage title. it has came a long ways.
Thanks for the ideas. I am getting sick of this project now. I think i am going to shut the shop door for a couple days and then maybe move some brackets.. ha ha. My lowers are only moved in about 3 in's on each side of the axle. I really am a fan of anti-squat being a little on the high side. I have seen to many rigs with coilovers get on a steep incline and the front end unload and want to just flop over backwards. I am not a fan of the axle steer but how much is really to much. I find it nearly inpossable to eliminate all axle steer when fully flexed out.

 

[reddman]

thanks the truck started out as a budget truck that i bought rolled and with a salvage title. it has came a long ways.
Thanks for the ideas. I am getting sick of this project now. I think i am going to shut the shop door for a couple days and then maybe move some brackets.. ha ha. My lowers are only moved in about 3 in's on each side of the axle. I really am a fan of anti-squat being a little on the high side. I have seen to many rigs with coilovers get on a steep incline and the front end unload and want to just flop over backwards. I am not a fan of the axle steer but how much is really to much. I find it nearly inpossable to eliminate all axle steer when fully flexed out.

My reasoning for liking low, more "neutral", AS numbers is due to the inconsistency of traction in our world. Any AS # other than 0% is taking drive torque and moving the suspension with it. Shoving the chassis up (with a higher AS #) will cause a momentary increase in tractive force on the rear tires, which sounds great, but if at any time that traction is lost, and it very often will be, the suspension will unload. This can easily start a full blown bouncing cycle; and we all know bouncing on the rocks leads to

In a front end your AS number is really anti-dive or pro-squat. This fights nose dive when on the brakes hard, but can also cause some pretty nasty brake hop in extreme cases.


I wouldn't worry about roll steer at low speeds as much as I would be concerned about the serious roll oversteer caused by a positive roll axis angle. Oversteer is scary and a handful to keep in control of. Basically when you turn, going around a corner, and the body leans, roll oversteer will turn the truck even sharper by turning the whole axle housing into the turn, which makes it lean a little more, making it turn sharper still. It's a scary handling characteristic at best, and downright dangerous at worst.

A slightly negative roll axis angle will slightly understeer, which is a natural and easily predictable action for a driver to deal with. Whenever possible it's better to err on the side of a little understeer than any oversteer. When you hear race car drivers complain of a "loose" car, they are describing oversteer. It can be driven, but it's right on the edge of out of control.

 

[Goose]

I agree with redman. on the AS #'s
I linked my rear last fall & I left my lower front mounts a bit high (clearance)
It performed quite well, although on suicide hill I noticed that It hopped a bit.
I have since dropped the lower front mnt 2". I lost some clearance but my lowers have a much better angle now.