Firestone Ride on LX with AHC

[trackmur]

I installed a set of helper air bags on the weekend. I had bought the firestone bags through the heavy duty truck parts supplier that I use for work. I think they were around ninety dollars, and I think they are less than that on EBAY in the U.S. but I am not there and it is always nice to buy stuff from a business that will take anything back. This kit says it is for both the LC and the LX but the LX does have a very different bump stop. My LX has close to 400 000 km on it and I often pull trailers in addition to carrying a considerable load of tools at any given time. I have had 3 AHC dropping to low events over the years, all of them being quite obvious results of too much weight.

I wanted the bags to reduce the loading transferred to the displacers as the coil springs aged; and to allow me to not have to worry when I pull a couple of trailers that I have that have very heavy tongue weights. Presently I move all the tools forward when pulling these when the two 100# propane tanks are full.

Here are the Firestone directions:

http://www.firestoneip.com/site-resources/ride-rite/installation/4124.pdf

After reading this, and realizing that there were differences I went to work.

With AHC in low, the rear wheels off, the frame resting on jack stands and the rear axle lowered, I felt the brake flex line was sufficiently extended. I didn't bother pulling the shocks off, but instead grabbed the (2) macpherson strut compressor tools I have, compressed the spring slightly and then removed it. The LX bump stop has two small blobs of rubber atop a very large bump stop blob. The firestone directions expect the LX to have a bump stop similar to the LC and instruct you to remove most of the bump stop; 4 convoluted sections.

I unbolted the LX bump stop, and while I tried very hard to not break the fastener, the exposed threads at the top were sufficiently mucked to fail on the Left hand side. Turning back and forth did manage to get the bump stop fastener out on the right hand side. It was not that difficult to drill out the broken fastener, and it was certainly easier to run the air line tubing up through the larger drilled out hole than the one that remained threaded.

I removed the two convoluted sections of bump stop, likely leaving more bump stop than the firestone directions suggest. I felt this left the nicest surface for the air bag to work against.

In any case, it is a very simple task. Remove spring. Remove bump stop. Insert air line into air bag, insert air bag into coil spring, run air line up through bump stop and then up through bump stop retainer, re-fit spring/bag assembly, and then loosen the spring compressors.

The bags need at least 5 pounds of pressure to stay in place and keep the bump stop located, so the air lines need to be run, finished and a bit of air thrown in before anything else is done. The RH air line follows the rear AC tubing and then goes across above and behind the spare tire. The LH line follows the (my own) trailer power wiring that follows the frame rail from front to rear. The two schrader valves are set in a bracket that places them inside the ridiculous little bracket attached to the trailer hitch to fit trailer plugs onto if you don't mind having the trailer plugs ripped off frequently.

I was careful to have the bump stop up and in place and the bag next to it before adding air in. It takes very little air to inflate.

Once the bags have a bit of air pressure, I jacked up the rear axle, refitted the wheels and set the truck back down.

I have a plan for an electronic displacer pressure gauge, and then a junkyard air compressor, (probably cadillac, but not an engine vacuum powered air compressor like Elvis' last Seville, no matter how cool those 70s Cadillac engineers think they are) so that I can be very precise with applying air to the system, but for now I will just take a measuring tape and use the bags to return to standard ride height when a serious load is added.

Obviously, the stuff that the Australian folks are doing has inspired me.

 

[CappyKD]

Nice!

 

[lexi4darin]

But how does the ride feel? Any different?

 

[trackmur]

Sorry, I managed to get the title wrong, it should be Firestone Ride Rite on LX with AHC.

It rides the same, as switching the shocks from one setting to the other goes from soft and mushy to stiffer. I have only about 18 lbs of air in the bags. Clearly the fluid globe needs to be carrying weight for the shocks and the remote valve bodies to do their job. I did notice that there is a bit more AHC fluid in the reservoir, but I did not mark it before so that isn't a particularly scientific observation.

 

[lexi4darin]

How long did the install take?

 

[lexi4darin]

And how much extra weight do you suppose the LX470 can handle now that the air bags are installed?

 

[trackmur]

The second side was under an hour, though it was more difficult to sneak the coil spring out on that, the RH side, I didn't have to drill out the bump stop bolt. Again, I didn't unfasten the brake flex line and remove the shocks to get the axle completely out of the way; I compressed the spring a bit.

As for the increase in load capacity-I didn't want much. I wanted to be able to go somewhere with 8 adults and not have the AHC drop down to Low. I wanted to be certain that at the end of a 600 mile day I don't find myself twenty minutes from home, stopping at the side of the road to move tools out of the boxes in the back and into the passenger front footwell.

Obviously, Firestone are only going to say that their product will allow you to safely load your vehicle up to the recommended GVWR from the manufacturer. However, they also say the springs are good for 500-1000 lbs. I think the Australian version of the LC is rated to tow more than those sold in North America, and 100s with AHC are quite limited in carrying ability; I think this certainly would bring an AHC vehicle in line with a regular all steel sprung version.

 

[trackmur]

I have put a couple thousand miles on the LX since adding the bags, so I thought I would post a report. I easily had all of my tools, the extra stuff I carry for the car trailer, and then an Audi A4 on the car trailer; however the scale I expected to use was closed for repairs so I can't give actual numbers. With the Audi I ran 35 lbs of air in the bags. I have been going around with 15 lbs without.

Yesterday I had a new civic on the car trailer; mostly to deny the sales dudes of their ridiculous "delivery pod" handover theatrics. We got home with the civic, put it in the garage, and then went to dinner. The AHC dropped to Lo mode immediately after we pulled the car off of the trailer - I had gone to 35 each bag for that too; and I had left the LX running, and so it was sitting a bit high in back and wasn't able to level itself off. Clearly the AHC doesn't like being told what to do, so I had to shut the LX off, remove air from the bags, and then restart to make amends with the system.

I have looked at a couple of transducers to get the pressure at the bleeder of the fluid globe, but haven't done anything about it yet. I'll need to make an adapter to go in where the bleeder fits that can accept the transducer and then a bleeder as well. This would be useful, however I am pretty certain that simple use of a tape measure, taking a few notes and paying attention to the load vs airbag pressure will be much simpler. Also, driving it with the bags still heavily inflated was a bit hybristic.