47-55.1 IFS w/ air bags - front shocks?

[LEEVON]

I am running a traditional style TCI MII front end with air bags on my '50. The kit included frame tabs for mounting small/short shocks on the outside of the frame to the lower control arm. IMO the size and rate of the shocks isn't enough for a V8 truck. It rides like crap, doesn't absorb bumps the way it should, not very confident cornering, etc. I'm running 235 tires 15" wheels, nothing else unusual. I'm thinking of finding taller upper mounts and longer shocks with a higher rate.

Anyone dealt with this?

[e015475]

Have airbags on my truck. It isn't drivable yet but am concerned I'll have the same ride issue as you.

What size of airbag are you using in the front suspension?

What's the 'lever ratio' of the bag on the lower a arm?

What kind of pressure are you normally running in the front air bags?

I'm running a 7" bag on the front with the bag sitting right in the middle of the lower a arm. It takes about 90 psi or so in the bag to get the suspension off the stops. I've not driven it yet, but I'm concerned about a choppy ride like you describe.

I am using a stock length gas-charged shock on the front and I'm guessing it is about 20" long. To get the long factory shock to fit, I used a kit from Throrbros to build a shock tower for the upper mount. Here is a link to it-

https://*************/shock-relocati...relocating-kit

I modified it a little to add a third side to stiffen it up a little. Here's is a photo without the shock installed, but it should give you an idea

[e015475]

Looks like the link to Thorbros won't work. Just Google them (they used to be called SuicideDoors or something like that)

[joedoh]

Originally Posted by LEEVON

It rides like crap, doesn't absorb bumps the way it should, not very confident cornering

only one of those things, absorbing bumps, is a function of the shock, and only partly. riding like crap is usually a spring rate problem, cornering confidence is spring rate and sway control. absorbing bumps is also only partly a shock problem because spring rate has much more impact.

what air bag are you running? what pressure are you running? do you have up/down controls for each corner or up/down control for the front together?

a lot of people run too small a bag for the front, usually based on space constraints, and that requires higher pressure than normal to get to a ride height. these two factors, bag VOLUME and bag PRESSURE are usually the biggest difference between a good ride and a bad one. a high pressure/small volume bag will oscillate less, the shock cant do its job because the airbag is very stiff.

following with that, ride height has a lot of impact too. ride height with air bags is (generally) half travel of the airbag. with some suspensions thats simply not enough lift, because zero pressure is flat on the ground and so half travel is only 3-4 inches, not enough to clear some obstacles. I have seen it more often than not, the truck gets lifted all the way possible to give driving clearance and the ride is terrible, party because the suspension is "locked" with a super high spring rate and partly because the shock is topped out to its upper limit, which gives no down travel.

finally, when installing bags you want the last breath of air to leave the bag just as you hit the lowest point of the suspension. some kits are installed as one-size-fits-all, but tire size and the desired "aired-out" stance both impact the airbag mount placement. a good rule of thumb is to have the upper and lower mount ~3" apart when the truck is aired out. any less and the bag will squish completely before the truck is at the desired height, any more and the truck will still air out fully but there is extra volume left in the bag. extra volume means the pressure will need to be higher before any lifting happens when airing up, and final pressure will be higher to get to the desired height, both will impact spring rate and ride quality

sway control is either done with a sway bar, or individual corner controls, or both. if you dont have a sway bar or individual control bags, as you corner the air will be pushed from the outside bag to the inside, leaning you over in the turn.

how do you fix this?

1. "get realistic" about your drive height. if you need 6" of ground clearance at drive height, that means you need 6" of drop from half travel. Thats a tall order, especially on a short spindle setup like a mustang II. you may have to set the truck up to lay 2" off the ground when aired out, so that half travel is 4" lift and gives you 6" ground clearance. by the same token, you may feel like you need it higher than it has to be. if you get 4" at half travel, it may be enough to clear everything and just look "too low" to you and so you lift it more and ride quality suffers. or, a lot of guys think a truck should be level at ride height when the best ride is actually with the bags at half travel, which means the front may be higher than the rear because the front is a leverage setup. adding air to the rear to be level can make for a stiff ride.

2. set/check your mount distances. aired out the rule of thumb is ~3" between mounts. if you have more than that, use a spacer or change the mounts. if you have less than that, your truck is probably holding off the ground.

3. check your pressures. if you are at 100psi at ride height your spring rate is very high and you likely have 'too small' an airbag in there. moving to a larger bag with more volume will lower the ride height pressure and lower the spring rate, but there can be too much of a good thing. a huge bag will get to ride height with a low pressure and low spring rate that oscillates a lot and either foams the shock (rendering it useless) or bottoms you out on bumps.

the same thing goes for the rear, I see too many guys using leverage systems in the rear that have full lift at 10psi while the front takes 110psi. thats going to ride poorly no matter what shock you use.