MG Sports Cars

I went to Jim Blackwoods last Thursday and we installed his air bag front suspension system.
finding a location for the compressor and the guage. We put the compressor in the left rear fender pocket of the BGT and the guage is mounted almost beneith the steering wheel beside the volt meter in my car.
The bags were easier to install than the compressor and the guage. then we had to run the power to the compressor and the air lines back up to the front by way of the guage.
All worked well and we finished about 9:30 that nite(we started about 2 pm) We pumped up the system and then quit for the night. The next AM we checked the pressure (no loss) and then took it for a test drive.
It rides much smoother than before but there is no increase in lean in the turns. I then drove 530 mile back home with no trouble.
On roads that I am familiar with I can really tell that the harsness in gone and the ride is better.
Jim says the price will be $450 and he will install it for $300. You should be able to install it yourself though.
I have not driven it at night yet and I want to see if I can adjust my headlights using this system. Mine seem to be a little low and I figure I can just pump up the front a little.
So far I am really impressed with the system.

Steve

That sounds great, Steve. I am glad to hear it works so well. Too bad there isn't one for Triumphs!

Dan B

Steve,

Is this just on the front?
Did you use the standard arms and pivots or did you use spacer like Jim has done?

It is just the front.
All that was changed was the steel springs were removed and the air bags installed. Nothing else is changed.

Steve

Having ridden in the car, I believe this will soon become recognized as a serious performance modification. The progressive rate of the bags stiffens the suspension more quickly than the springs do, giving both a smoother ride and a stiffer suspension. How often do you get something like that? As a result roll control appears to be somewhat better as well. So basically a better ride, no worries about bottoming out, less roll, and on-the-fly ride height control. My car hasn't lost a pound of pressure in over 3 weeks, but if you should lose pressure for some reason the car will drop to the bump stops where it will remain driveable, if somewhat uncomfortable. Road hazard damage is next to impossible. Unsprung weight is reduced as well, by IIRC a couple pounds per corner.

To give a little more info on the system, as installed in Steve's car and for that matter the other installs as well, the air bags replace the stock springs with a steel cup locating the top and the spring pan locating the bottom. The area around the bump stops is ground back a bit for clearance. A 1/8" plastic air line exits an angle fitting at the bottom and is routed through holes drilled in the spring pan and crossmember and is routed into the cockpit area where control and pressure connections are made. Rubber hose insulates the line at contact points. Nowhere is the line or fittings exposed to road debris. Normally the compressor is located in the engine bay. Parallel "Y" fittings are used for junctions and all fittings are simple press-in insertion type, including the gage. Locations must be found for one standard 2-1/16" 270* sweep 150 psi white on black chrome bezel gage, one air bleed valve button, and one pushbutton to turn on the compressor. The gage nicely matches the stock instruments, the bleed is a brass button and needs about a 15/32" hole while the switch needs about a 5/8" hole. Soldering is required for the connections to the switch and the compressor and an unswitched fused power source is recommended, the cigarette lighter circuit is a good choice. The compressor is mounted on two rubber isolator stud mounts and can be configured 8 or more different ways to accommodate mounting location. I find the bulkhead recess where the rectangular rubber plug is located to be a pretty good spot.

The compressor supplied with the kit is pretty basic. It is slow and not particularly quiet but it was chosen to give acceptable performance while keeping the kit price down. There is a very wide range of potential upgrades. One option I like is the combo compressor/drier used in Lincoln vehicles. Powerful, quiet, reasonably priced aftermarket, or recycled junkyard pulls, this is a serious upgrade but adds some weight. Addition of a pressure tank, pressure shutoff switch, overpressure safety valve and solenoid valve gives near instant ride height control. Individual lines give corner jacking ability. When I have time to build the Mark-II Jag IRS it will very likely be available with air bags as well, meaning 4 corner control. Steve has rear tubular air shocks in his car meaning he already has front and rear ride height control, here too separate lines give 4 corner control. Of course on such a system gages and such can become a serious space issue.

This kit has been designed to give the most versatile combination of low cost, simplicity, control, weight reduction, and ease of installation but obviously everyone will have their own ideas about what is best, so the basic kit is a good starting point regardless of the finished installation.

JB



Edited 1 time(s). Last edit at 06/15/2011 05:13PM by BlownMGB-V8.

Do you have any pic of the install?

I thought so, but so far the only thing I've come across are early photos of the first install on my car before the air lines were worked out. I've got it torn down for a LCA upgrade right now but as soon as it is back together I'll post some new photos.

JB

Guess I dropped the ball on those photos, maybe I can do something with that tomorrow.

There has been some more development work on the system. We had a few issues with leak-down and tried a number of fittings before coming up with the right combination to reliably hold pressure. Oddly enough sticking with one product line for all of the fittings was not the answer, and I had to invest quite a bit in fittings before finding the answers I was looking for. Any air system is likely to be a challenge in terms of long duration air retention. The air compressor can make up for small losses but it's far better not to have to use it. Naturally the more devices and connections you have in the system the greater the challenge but I think we have it sorted out, and are presently seeing a typical leak down rate around 10 psi over a two week period. Not perfect, but tolerable, and I think we can improve on that.

Today the last one of my tires arrived and I was finally able to put my car on the ground and evaluate the new smaller diameter air bags. The suspension is noticeably stiffer with them than with the larger ones and I think they might be a good choice for someone looking for a competition oriented spring rate, or for someone who does not want to deal with trimming the plate under the bump stops. Pressures required appear to be in the 100-160 psi range. For my car I am going back to the larger diameter bags as I want the spring rate to more closely match the spring rates I'm running at the rear.

At this point we have the system on 3 cars. Steve's, which gets driven regularly, the MG-Roadmaster which does a lot of sitting around, and mine which has been spending a lot of time on the rack. So far it looks like it's working out pretty well. Steve told me recently that the ride is very definitely better, and he hasn't had any complaints with the handling either. We will try the MG-Roadmaster and my car initially with no swaybar and see what sort of handling we get that way just to set a baseline.

JB

I had a 58 Pontiac with rear air bags and it rode great, well, for a 58 Pontiac anyway. Would it be possible to fabricate a mounting system so as to use air ride in the rear in place of coil-over’s? How difficult would that be and would the results be beneficial?

Paul, there would be two ways to approach that challenge, and the one I would try first would be a set of air shocks. The other, and much more expensive option are the new air bags built around an adjustable shock but those are still horrendously expensive. Steve DeGroat has been running air shocks on the rear of his GT for years, but I think he is still using the leaf springs suspension. He has found a shock with a good damping rate however and with more air pressure I'm pretty confident it'd do the job. I believe he usually runs pretty low pressure except when towing and carrying heavy loads.

Steve, would you be willing to post the specs or application info on your air shocks?

JB