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Unread 05-15-2013, 02:51 PM
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Fair! Fair! is offline
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Join Date: Jul 2004
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Default Re: Vorshlag E38 740iL - Amy's G-ride

Project Update for May 15, 2013: Amy wanted to take the 740 on a road trip so we finally had a date to motivate us to do some repairs and updates to the big E38. Here's what went down in the past few weeks with our 2001 BMW 740iL - some repairs, some suspension development, and some clean-up work.

The number one problem that was noted during our PPI inspection was the front suspension was "jacked up". The front ride height was all goofy, the control arms had worn out bushings and ball joints, the front struts were blown, the strut top mounts were shot, and the end links were worn out as well. All fairly typical stuff on a 12+ year old BMW with nearly 100K miles.

One thing that was atypical was the front alignment - there was +1 positive camber on both front wheels?! That should never happen on a BMW with McPherson strut front suspension, and we think it was a previous repair that was done incorrectly that caused it (you have to preload the front control arms at ride height before you tighten them). This abnormal alignment and ride height was causing some funky front tire wear - both front tires were wearing very quickly, and eventually got into the nylon cords all the way around the outer edge on the RF tire (see above). If we would have fixed it sooner it wouldn't have corded, but these tires were so dry rotted and old anyway that they needed to be replaced. I knew that when we bought it, too.

Here's the production Bilstein PSS coilover kit we started with, made to fit another chassis

Problem was I really wanted to do the aftermarket suspension updates first, then order custom Forgestar wheels, then get new tires all around. But the corded RF tire + Amy's looming road trip accelerated things a bit. So we did the research and realized there wasn't much aftermarket suspension support for the BMW E38 chassis. Some OEM replacement type shocks, some Chinese coilovers (no thanks!), and KW coilovers (twin tube). Instead of these options we chose "none of the above" and ordered the above Bilstein PSS coilover struts and shocks shown. The "PSS" is a non adjustable monotube coilover kit that comes with new springs and is priced very competitively. The PSS9 is similar and has a single adjustment knob, but the price jumps up quite a bit. We figured that we would try the PSS and see if that worked without any valving adjustment. These particular shocks were not made for 1995-2001 BMW E38 7 series chassis, but instead are a Bilstein engineered kit for another "similar" chassis BMW. We felt like we could work with them and get them on the E38. Fingers were crossed.

Left: The car was on the lift for 2 days while we "re-engineered" the shocks. Right: Bilstein inverted front strut, disassembled for rework

The Bilstein PSS coilover kit looked amazing when it arrived and I was bound and determined that we would make it fit this car. The front struts featured inverted shafts and 36mm pistons inside. The rear was an easy bolt-on affair, but the front... not so much. I won't get into all of the details, but these went on and off the car several times checking bump, droop and ride height numbers with multiple spring set-ups. We made some significant tweaks, and after custom machining and other mods to the front strut housings, they fit perfectly at the ride height we wanted.

Click these two pics above for higher rez versions

Yes, it is lower than stock by a good bit, and the above pictures show the final ride height we settled on - which gave us plenty of bump and rebound travel. Front ride height is now 14-3/8" (center of wheel to fender lip) with full droop at 16-3/8" and maximum bump at 12-1/8"... that leaves us 2-1/4" of bump travel and 2" of rebound travel, which is just about perfect (we like to bias towards more bump than droop, with about this ratio). We could make another set like this with this ride height or up to 2" taller, depending on the needs of the owner. We will see if there's any interest and potentially make a production batch just like these, to keep costs down.

We also replaced a lot of suspension parts up front when the coilovers went on including: all 4 lower control arms, end links, and strut mounts. A pair of new tires went on the front in the stock 235/50/18 size - some cheap "Sumitomo HTR Z III", just to use on her road trip until we get the Forgestars ordered. The rears were also a bit crusty looking but they still had ample tread, so we elected to leave them in place for now. I was worried that it might ride harshly with the springs provided in the original kit, which we tested at 470 #/in front, 157 #/in rear, with the rears slightly progressive. But after the 6 hour road trip + 3 days of driving around while out of town, Amy, her mother, and grandmother all loved the ride quality - so that works for me. She did note that the front tires were pretty loud on the highway, so we won't be recommending that brand (not that we had ever recommended Sumitomo tires before).

The other "emergency" work performed included replacing all of the valve cover gaskets (2 levels of gaskets + about 20 bolt grommets per each side). While that was being done a new set of Bosch+4 platinum plugs were installed, and the stock valve covers were cleaned up, refinished and painted semi-flat black (instead of the factory gold), to match the rest of the black engine covers. The engine bay was already somewhat detailed before and this refinish work on the valve covers made it look that much better. There were several more new underhood parts that we ran out of time to install, including new power steering lines, air filter, serpentine belt, and some other small things. When a customer's car is on the line we stay late and make it happen, but when it is one of our own cars... we can always reschedule. The custom suspension install ate up a lot of time already. The valve cover leak was the worst offender under the hood, and at least that was tackled.

For various reasons there were almost no pictures taken while all of this work was going into the 740, so I've just stuck in the pics we have. It was a bit hectic around here with orders, customer service work, and everything else and this is all we shot. When the car comes back int he shop we will pull the wheels and get more pics.

What's Next?

After a little more measuring with the new PSS kit installed, custom Forgestar wheels will be ordered. We tested the OEM rear 18x9.5" wheels and 255mm tires on the front of the car, and they fit without any mods using the stock suspension, so the fronts will likely be at least that large (and maybe 10" wide). The rear looks like it can swallow a 11" wide wheel, so ... who knows? It will look tasteful but will be significantly wider than stock, and there won't be any garish colors, giant lips or chrome finishes on the wheels we're using. This is a BRAND NEW wheel from Forgestar, and there won't be another E38 on the road with this style and size, at least for a while. This isn't being built for any sort of track use, we just want to have a lot of tire under this car.

The rear suspension still needs some attention, too. Rear subframe bushings are SHOT - you can put a small amount of load on the rear suspension and watch them move. Trouble is the only replacement options seem to be OEM style rubber, as there's no love from Powerflex or Whiteline for poly replacements. Its not that this car "needs" poly bushings, it is the OEM bushings are just not very good - too mushy, and they will wear out again before long. Oh well, we will deal. There are several other bushings and bearings out back that will be replaced with new OEM parts when the subframe is out for bushing replacement.

When the rear shocks were being swapped, one step was the rear deck and back seat had to come out, and it was apparent then that all 4 OEM speakers mounted to the rear deck are blown. They were just shredded. We will check Crutchfield, BSW, and the other speaker sales outlets and get some fresh speakers in this car soon. There are still a few small cosmetic repairs that need to happen inside and out, including new window trim on one side that is messed up.

That's all for now... check back when we have more updates. We're just getting started on this car.

Last edited by Fair!; 12-04-2013 at 09:36 AM.