BMW 750il Challenge Build

rcutclif wrote: ...there are still a lot of variables in play.

The Dude: "This is a very complicated case, Maude. You know, a lotta ins, a lotta outs, a lotta what-have-yous. And, uh, a lotta strands to keep in my head, man. Lotta strands in old Duder's head.

https://www.youtube.com/watch?v=Jw36ivnRHRQ

Awesome build.

Well, ladies and gents, the self-leveling rear suspension (LAD) is now deleted. This is a hydraulic system that uses an engine driven pump (shares the power steering and power brakes pump) to add or reduce pressure to the two rear shocks to raise or lower the ride height. It uses a pressure regulator that is attached to the rear sway bar to sense when the car needs to be raised or lowered. Since it was leaking, and replacing those shocks is NOT challenge budget friendly, I decided to delete the system.

First - remove all the old and place it next to the new (used). These bilsteins and dinan springs are from an e34 5 series, but I thought they might fit. The different part number from bilstein may indicate different valving, but there wasn't exactly a huge selection of used bilsteins for 25 y.o. BMWs available, so I'm running what I could get. Note on weight difference: the 'bombs' (pressure canisters attached to the shocks) are quite heavy - maybe 10 lbs each, but the rest of the system (lines, regulator, and distribution block) weigh almost nothing. So this mod might save 20 lbs total.

Next bolt the bilsteins into position (lower shock bolt and the three upper mount bolts fit perfectly - woohoo!). The bilsteins even have 4 or 5 grooves on the shock body, and use a big c clip to fix the lower spring perch to the shock body, so they are even height adjustable! I left them in the middle setting for now. Unfortunately, both bump stops are ripped in half. Oh well, what can you do.

Driver side:

Passenger side:

Finally, to complete the mod, you have to re complete the fluid circuit. Remember this pump is shared with power steering and power brakes, so you can't just plug the lines - you need to connect the to and from lines so that the pump can continue to circulate fluid. Luckily, in the driver's side front wheel well, a plastic access cover is the only thing covering up the two lines. AND BOTH LINES HAVE A JUNCTION FITTING, so looping them together is simply a matter of un bolting, bending the lines around, and using one of the couplings to reconnect the two together! Easy, and free. Its almost like BMW planned for someone to do this. Ha. Here it is done.

So all in this mod cost me $100. The new (used) shocks came with springs, perches, very good looking upper mounts, good lower bushings, and free shipping. I was able to re-use the female to female connector to re-connect the hydraulic pump lines, and everything else was just removing dead weight! I guess I might even be able to sell things that aren't leaking, but so far I am finding few people are interested in buying this old crap.

Petrolburner wrote: Awesome build.

Thank you!

Mounted up all 4 hoosiers and did a test run in the nearby abandoned parking lot. threw around a lot of gravel! Here is the level stance pic. Front wheels poke out a bit because of the 1 inch spacers, but oh well.

Keep in mind this is 2 coils (out of 6.5) cut out of the front springs. I can't believe it is still sitting this high.

All that is left is to replace the battery (I think it finally gave up the ghost), finish up some small cosmetic details, and give it a good cleaning before the event. Maybe I'll even get crazy and change the oil.

I missed it... Why the spacers?

This thing should be fun!

Rob R.

wvumtnbkr wrote: I missed it... Why the spacers?

These 16x8 wheels with 225 street tires had rubbed the strut just enough to clean all the paint off the strut in one spot on both sides of the car (these wheels are from a newer 7 series, and have a slightly larger offset and are wider than stock - 23 vs 20, 8 vs 7 I believe), so:

A, I wanted to fix that problem,

and B, I wanted to run wider tires than 225.

I did some quick calcs and thought I would need 20 - 25 mm of spacer to fit the extra width (plus some just in case the hoosier is actually wider than a street tire). Searching Ebay, it turned out that 25 mm spacers were like $120, but I could get a 1 inch spacer (1 in = 25.4 mm) for $30. Easy decision.

Now I have about a finger worth of space (3/8 inch, maybe?) between the inside of the front tires and the strut. Plenty of clearance now.

Maybe if I find some good deals I will try a 15 or 17 mm spacer to see if it all still fits but would narrow the front track a bit.

So I was hooning around last night "testing" we'll call it, I developed a pretty significant clunk in the front suspension. Basically when you go from no brake to some, you get a pronounced 'clunk' that feels like it is coming from the front driver side wheel. You can feel it in the steering wheel.

I took the wheel off, and while I could not replicate said clunk with my own two hands and a prybar, I think it might be the lower ball joint.

I jumped on rockauto and ordered all 4 ball joints in the front end (they were $25 each, after shipping) to be safe. They are supposed to get here friday. Getting down to the wire!

I plan to have my wife help me today to see if I can get her to drive the car and replicate the clunk while I can look from the outside.

I had a similar clunk in my 95 540i/6 (same suspension design) that ended up being a loose balljoint so you may be on the right track. Good luck!

rcutclif wrote: So I was hooning around last night "testing" we'll call it, I developed a pretty significant clunk in the front suspension. Basically when you go from no brake to some, you get a pronounced 'clunk' that feels like it is coming from the front driver side wheel. You can feel it in the steering wheel. I took the wheel off, and while I could not replicate said clunk with my own two hands and a prybar, I think it might be the lower ball joint. I jumped on rockauto and ordered all 4 ball joints in the front end (they were $25 each, after shipping) to be safe. They are supposed to get here friday. Getting down to the wire! I plan to have my wife help me today to see if I can get her to drive the car and replicate the clunk while I can look from the outside.

BTW, the balljoints on those cars are built into the control arms and you replace the control arms to replace the ball joints. On early cars there was a "balljoint" built into the front cross member mounting, but it was ditched for a solid mount and a tubular cross member.

Note: do not use this cross member as a jacking point, you'll cause it to spread and woe-is-you if you try to remove or install that piece as it will not fit any longer. I had to use a tubing bender to tweak mine to reinstall it after replacing both mounting bolts due to rust damage along with the inner bushings.

To make it easier to remove and install the lower control arms, use a welder to tack the lower control arm mounting bolt nuts to the cross member. Otherwise you need to make a special 22mm wrench to hold them in place while you loosen and tighten it. Of course you have to torque the fasteners with the suspension loaded, adding another layer o fun. If you can get the parts clean enough, you can use JB Weld if you don't have a welder handy.

If you didn't get new control arms then you might also look at the inner bushings (750's use stiffer bushings apparently). Removing and installing them, even with a hydraulic press is pretty annoying and fiddly as you have to ensure they are aligned properly.

To help with bumpsteer reduction and correct camber on lowered cars you might look at spacing the ball joint mounting plate below the front struts by however far you lower it. I installed 1.25" spacers on mine, they weren't cheap, but looking at them they don't look too difficult to DIY with access to a router table, a skill saw and a drill press. I've used standard router bits with aluminum with good results when I made air horns for an intake on my 924, so cutting a slot and decking the other side to create a keyway doesn't look too hard to do after tracing the pattern, cutting it out. After making the notch cuts you can mark and drill the holes for the mounting bolts to ensure proper alignment.

Combined with slotting the upper mounting holes for the struts, you should end up with a decent amount of camber without a weird handling ride.

These links might help:

http://www.bimmerboard.com/forums/posts/563318

http://www.nmia.com/~dgnrg/page_26.htm

http://www.e38.org/e32/

BTW, if you don't want the LAD stuff, I might like to take them off your hands as I'm repairing mine right now and some of it is pretty rusty.

In reply to Bruce:

Thanks for the info! Yes, I ordered all 4 'control arms' that have the ball joints built in. It didn't look like it was going to be too hard to replace them, but I haven't started yet either.

I also haven't thought too much about adding camber or correcting for bump steer. Maybe ill get that far before next year, but yeah, that does look like an easy solution to drop the lower ball joint. I'm still not horizontal though on the lower control arm at static though, so it also may not be a huge issue yet.

As far as the LAD stuff, i'll send you a PM.

Car looks good. Looking forward to watching it autox tomorrow.

Looking forward to the Aristocrats dominating!

Well, Challenge is come and gone! What a great time for all. According to the posted results, looks like I scored a 12th place finish overall (15th minus the 3 exhibition cars above me). Not too shabby at all. I also got 2nd out of 7 in the aristocrat class, so no slowpokes there either.

Here is the car back home and in its final event form (I'm sure there are other photos out there, but I apparently took very few at the event):

And since the event is over and we are thinking about next year, time to clear some space in the garage. GRMers get great deals from me as well, if anyone wants to carry the torch. Note the hoosiers are not included, but I could be convinced to sell separate.

CL link

I think your ad should have a picture of full race rubber so I sent you a pic.

Maybe write that race rubber is available for additional fee.

Hype up the magazine connection. Maybe a sentence like, 'purpose build for magazine feature, now sold at a loss to make room for next magazine feature build." The story will hit the news stands in Feb 2016 so this is your chance to get in before the official release.

Also mention that the car won second place in class.

... why did most of the paint go away?

pres589 wrote: ... why did most of the paint go away?

...that sh!t's heavy.

Good to hear you guys made it home. See you next year!

thanks for the ad feedback, I updated it. I'll leave out that I am looking for a minivan to replace it with...

Great meeting you guys. Looking forward to next year's battle with minivans.

Nice job! It would be great to hear more about the driving experience since this was the first real outing.

Petrolburner wrote: Nice job! It would be great to hear more about the driving experience since this was the first real outing.

Thanks! And good point about talking a bit about how it drove!

Initial reactions:

• its pretty fast in a straight line. Unless you put the trans in sport mode, it shifts hard and regularly chirps 2nd. hehe.
• from inside the cabin, its really hard to tell you have a different sound than an i6. sure, at idle you can hear more pulses, but past that, to me its pretty indiscernible
• it drives 'smaller' than it is. Meaning tossing it around is easy and it is easy to control. Corners harder than it should for a car its size.
• it is still a LONG car. and still soft suspension wise, but smooth and predictable.
• you can tell it needs a bit of a refresh. bushings, noises, etc.
• we were unable to turn the ASC (active stability control) off, which was hindering the pro driver in the autox a bit. It was also engaging at the launch in the drag, but honestly it probably helped in the drags. Maybe a bit of research would reveal the right fuse to pull.
• got lots of attention in the paddock. The no-paint is really an attention grabber (good and bad).

Issues:

• it burst a leak in a coolant line during the autox. Easy fix, except the line was buried about 8 inches down between the firewall and the back of the head. Right above the trans too, so hard to get from below as well. I guess all BMWs of the era have slightly over-stressed cooling systems. (and 25 y.o. lines)
• it is making a driveline noise on hard right hand turns. Seems to be coming from the driveshaft tunnel, I think the u-joints on the driveshaft may be on their way out (common problem I read). Annoying for sure.

pres589 wrote: ... why did most of the paint go away?

Wondering that myself.

The car is now out of my hands, but it will live to race again!

https://www.instagram.com/p/BDnvpqFMWFK/?taken-by=caswell318

I saw Caswell posting about it on facebook. Cool next step for this car!