Rear Suspension Recommendations

[Tincup]

I've been doing a lot of research lately trying to decide what type of rear suspension to put on my 67 Dodge D100. I see a lot of guys using parallel 4 bar setups on a lot of trucks, is this the best way to go for handling? How about triangulated 4 bar? For some reason I really like a trailing arm type suspension, I'm sure I could adapt a Chevy setup to fit my Dodge, it this better or worse than a parallel setup? What do you guy's recommend? I plan on running coil-overs. Thanks

[protouring70]

Maybe Rob from NO LIMIT ENGINEERING will chime in on this I've read some of his posts when people ask questions like this. He explains it in simple terms!

[RobNoLimit]

Thanks Brent. In a perfect world, you could build anything you want, and if we are focused on suspension performance, for street and track cars, we would all end up with F-1 prototypes. "packaging", and it's limitations has to be considered early on in the design. First, I recommend a trip over to 67-72chevytrucks.com and check out the "make it handle" thread in the suspension section.
Your dodge frame is a ladder style 34" OD chassis, fitting trailing arms to this may have its difficulties. 1. If the truck is low, the front mounting point for the trailing arms needs to be raised to just under the floor, or the top of the frame. without major mods to the frame rails, this limits the width of the trailing arm mounts at the axle to be around 34" wide, due to frame clearance, and we would really want them wider, say 42" to 45" on the axle. For handling, a wider suspension stance is better. But, if you mod the rails, next, build or mod the trailing arms to use a rotating bushing, "monster ball" or "johnny-joint" type. that allows them axle to rotate or 'tip' freely. Urethane bushings are good for drag cars with trailing arms, but bad for handling. coils, coil-over or bags can be used, but keep them at a wide stance, outboard on the frame.
Parallel 4-bars - from the top view, are a good fit to the OE chassis, but be careful, from the side view, they should NOT be parallel, they should be converging at the front mount, or getting closer together. Weight transfer lift points are determined by the point at which the top and bottom bars would cross, if they were extended forward. 4-bars that are truly parallel (roadster kits) never cross, - except somewhere out in space where light bends, and we couldn't lift anything from that far away, so no weight transfer. That means no traction. This set up will also need a locating device (side to side) like a panhard rod. This can be a plus because it can be mounted below the axle centerline to lower the roll center for better mid-corner and corner exit traction. Again bars and coil-overs outboard.
Triangulated 4-bars can also work well. One plus here is that there is no need for a panhard rod, but that can be a negative as well, as the roll center will be fixed very close to the axle center line. I recommend heims, rod ends, spherical bearings, or some type of pivoting bushing on the upper bars, to allow the axle to rotate freely. Lower bars and coil-overs outboard, upper bars can be inboard.
So back to the packaging design, What size tire, How low? and How much fab work? There are after all, No Limits :)

[Tincup]

Rob, thank you very much for taking the time to break it down for me. If I'm reading you right, sounds like the best way to go for my Dodge would be the parallel ( from the top ) 4 bar. To make sure that they are NOT parallel from the side, that they intersect at some point. Best to install outboard of the frame, and use a panhard bar, I would also like to include a sway bar. Would your Fatbar setup be a good choice?
As for the design, it's going to have 31.5" tires, its gonna be low, I am planning a big C-notch. I attached a link to my build thread, if you have a chance, please check it out.


https://www.pro-touring.com/threads/106912-Project-Cottonmouth?p=1066865#post1066865

[ArtosDracon]

That is the best way to go *IF*:
1: You're not interested in major modifications to the frame rails
2: You can put sufficient tire outboard of the links to retain traction.
3: You can appropriately package a panhard or watts link to locate the rear
4: You can accept that you're getting something drastically better and more adjustable than leaf springs, but not half way to the theoretical "ideal" for handling.

Looking at your build thread I see four main points to consider.
1: You're going to have torque, lots of it, that means strong bars and weight transfer is going to be very important.
2: Your desired exhaust location is going to be very near if not coinciding with the location of your bars, that may have to be changed.
3: You're even more nose heavy than any of the small block and some of the big block builds going on, planning your roll characteristics around that is going to be very important to keep it from either under-steering till the ass comes around or from roll-steering unpredictably at turn in, which will force you to constantly make corrections through a turn and slow you way down.
4: Your rendering shows the truck VERY low. That is by no means a bad thing, but will be very difficult to achieve without major frame modifications or a custom frame. I see that you're getting the newer rolling chassis to start with, which has a much better front suspension on it. If you can't use the front frame section under your body, consider fabricating the frame mounts to use the newer suspension on your frame, allowing you to build some of that drop into the location of the mounting points. For the rear you are looking at a bare minimum of a step notch to get that low, which will then require bed floor modifications. IF you have the fabrication ability, for your height and power goals, seriously consider a fire-wall back or complete custom frame. By the time you get that new front suspension on your frame, step-notch the rear, reinforce the ladder frame and add the 5 links, you're halfway to a complete new frame anyway.

[Tincup]

That is the best way to go *IF*:
1: You're not interested in major modifications to the frame rails
2: You can put sufficient tire outboard of the links to retain traction.
3: You can appropriately package a panhard or watts link to locate the rear
4: You can accept that you're getting something drastically better and more adjustable than leaf springs, but not half way to the theoretical "ideal" for handling.

Looking at your build thread I see four main points to consider.
1: You're going to have torque, lots of it, that means strong bars and weight transfer is going to be very important.
2: Your desired exhaust location is going to be very near if not coinciding with the location of your bars, that may have to be changed.
3: You're even more nose heavy than any of the small block and some of the big block builds going on, planning your roll characteristics around that is going to be very important to keep it from either under-steering till the ass comes around or from roll-steering unpredictably at turn in, which will force you to constantly make corrections through a turn and slow you way down.
4: Your rendering shows the truck VERY low. That is by no means a bad thing, but will be very difficult to achieve without major frame modifications or a custom frame. I see that you're getting the newer rolling chassis to start with, which has a much better front suspension on it. If you can't use the front frame section under your body, consider fabricating the frame mounts to use the newer suspension on your frame, allowing you to build some of that drop into the location of the mounting points. For the rear you are looking at a bare minimum of a step notch to get that low, which will then require bed floor modifications. IF you have the fabrication ability, for your height and power goals, seriously consider a fire-wall back or complete custom frame. By the time you get that new front suspension on your frame, step-notch the rear, reinforce the ladder frame and add the 5 links, you're halfway to a complete new frame anyway.

Robert,

Your Right...

My goal is to build a street truck that handles well, and could run the auto cross, if I so choose. I do plan on major modifications including, rear notch, raising the bed floor, boxing the chassis, and because I want to use the Viper brakes, a complete scratch built front IFS designed around the Ram spindles ( or a custom set ) . The Gen 3 V10 is all aluminum and weighs in just over 500lbs, so really no worse than your average iron block V8. The early Vipers had a iron block and weighed over 700lbs. I am OK with better than leaf springs, but not " Ideal" I'm just looking for a Fun truck.
Thanks for you insight, it's very much appreciated.

[ArtosDracon]

If you can weld well, transfering the new 1500 front suspension onto your frame wouldn't be as hard as most people think. I'm very glad it went all aluminum, weight savings are never a bad thing. For the rear, I would really look into doing axle flip, C-notch and replacing the leafs, then reworking the 1500 axle or doing some drastic offset changes so you can use the rear end out of the 1500 without linking the rear. For a street truck that will see occasional abuse and regular fun, you can get pretty far with some frame boxing and bracing and new leafs and shocks.

[Tincup]

If you can weld well, transfering the new 1500 front suspension onto your frame wouldn't be as hard as most people think. I'm very glad it went all aluminum, weight savings are never a bad thing. For the rear, I would really look into doing axle flip, C-notch and replacing the leafs, then reworking the 1500 axle or doing some drastic offset changes so you can use the rear end out of the 1500 without linking the rear. For a street truck that will see occasional abuse and regular fun, you can get pretty far with some frame boxing and bracing and new leafs and shocks.

Transferring the front crossmember and control arm mounting points was my original idea, however the track width would need to be narrowed almost 8 inches, not to mention the ride height is off by about another 8 inches. So I agree, it's not that hard a swap, but it would be difficult to end up with the desired results for stance & ride height. I was considering using leafs in the rear, it would be very easy to fab up new mounting points on the chassis for the leafs, do a axle flip & c- notch, to achieve the desired ride height, I'm just exploring my options.

[RobNoLimit]

I looked at the thread, I saw this when you started. really cool. It looks like you have a few stumbling blocks. So, from a project planning standpoint, let me ask a few questions. at the desired ride height, what would the height of the bottom of the rocker be? Is the bottom of the frame height even with the rocker, and if not, what is the height difference? How 'tall' is the OE chassis under the cab? (rail height). How tall is the tire going to be, or what size tire? and lastly, width. What is the desired track width, or WMS (wheel mount surface to wheel mount surface)? and what is the body width, inner wheel opening lip to inner wheel opening lip?

[Tincup]

I looked at the thread, I saw this when you started. really cool. It looks like you have a few stumbling blocks. So, from a project planning standpoint, let me ask a few questions. at the desired ride height, what would the height of the bottom of the rocker be? Is the bottom of the frame height even with the rocker, and if not, what is the height difference? How 'tall' is the OE chassis under the cab? (rail height). How tall is the tire going to be, or what size tire? and lastly, width. What is the desired track width, or WMS (wheel mount surface to wheel mount surface)? and what is the body width, inner wheel opening lip to inner wheel opening lip?

Rob, My plan for the build is to set the center portion of the chassis at 6" ride height from the ground, it is currently 12" from the ground. The center of the frame is 6" tall, the front portion where the control arms will go is 5 1/4" tall. Not sure on the relationship of the rocker to the frame, I'll have to check that. The rear tire is 31.5" tall (305-40-22) the stock wheel from the SRT10, the fronts will be 28" tall (255-40-20). The rear track will be 64" wms - wms, (I'm going to narrow the Dana 6"), this will give me 1+ inch per side of clearance to outer bed side. The front needs to be 62" wms - wms, this gives me 2+ inches per side clearance to the front fender. I have been doing my homework.

[RobNoLimit]

OK, I think you are going to have to build a frame. In the long run, this would be easier than modding the OE chassis, or another. When I start a project like this, one of the first layouts I do is an elevation sketch. This helps me make a few key decisions. Here are some factors. Lots of torque, and a motor that is a little longer than most. Tire and whee combo is set. 6" rail height under cab, with a 6" tall rail. coil-overs. '67 D100. Looking at the rear tire, at 31.6" tall, that puts the axle CL at 15.8" off the ground. Add 1.5" for half of the axle tube, and 4" for compression travel, you have the bottom of the rail, over the rear axle at 21.3" from the ground. Up front, the tire is 28.03" tall, putting the CL at 14" from the ground. First key decision - You will need to use a drop spindle. This will allow the IFS cradle to sit a little lower, and give you better motor placement. As a general rule, most IFS's, with a drop spindle will set the rail height 2" below the spindle, or in this case, appx 12" from the ground. If you start with 2x6 tubing under the cab, and blend to 2x5 for the front, and 2x5 to 2x4 for the rear, these elevation changes can be easily built into the rails. - see pict. Next questions, what is the bolt pattern, and the big one, what is your chassis budget?

[Tincup]

Like This?
98077

[Tincup]

Rob, I don't think another complete chassis is in the cards ( I have 2 already ), but I do think I can make a good handling street truck out of the two I have. I do like your Fatbar setup for the rear, If I have the necessary space outboard, (I'm pretty sure I will) I will use it. Now all I need is a custom designed IFS built around the SRT10 spindle (or a custom built piece), so I can run the 15" brakes and the factory wheels. Know anybody?

Mike

98093
98094

[aggie91]

Try these guys:

Home of the Jeebus Joint...

http://michiganmetalworks.com/

[Tincup]

Try these guys:

Home of the Jeebus Joint...

http://michiganmetalworks.com/


I've seen their stuff, they do nice work.

[RobNoLimit]

There are drop spindles avail, and I am looking for a pdf or dxf file of the OE suspension points. Not sure what it would take to narrow the OE IFS to your needs, and, would it still perform.

[Tincup]

There are drop spindles avail, and I am looking for a pdf or dxf file of the OE suspension points. Not sure what it would take to narrow the OE IFS to your needs, and, would it still perform.

The only drop spindles I have found are made by McGaughys and they are only for regular Rams. The big brakes of the SRT10 have a different mounting arraignment. I plan on designing up a set as soon as I pull off the OE spindles, I have a friend with a CNC milling station, I'll see how much he'll charge me to whittle out a set from billet.

[drewpy]

Frame swap to a 94 or newer chassis,cab mounts are close if not the same and all the new brakes and suspension will bolt on.