1 (edited by Lemon_Newton-Metre 2023-04-27 08:01 AM)

Topic: How to reinforce a rusty BMW jack point?

Finally got the clear title to this beast, and I find that in the two years it has been sitting (on pavement) the rear brake line rusted to failure. I look underneath and one - scratch that, two - of the jack points are rusted out and collapsing.

1. Suggestions to reinforce?

2. To rusty for Lemons?

Re: How to reinforce a rusty BMW jack point?

It is a Lemons car....clean the area as best you can and weld steel plates in. Once the cage is in it should add additional support.

"get up and get your grandma outta here"

3 (edited by Lemon_Newton-Metre 2023-04-27 08:42 AM)

Re: How to reinforce a rusty BMW jack point?

^Thanks for this; that's a great suggestion, but welding is beyond my demonstrated skill set right now (How hard could it be?), though my company has an educational benefit which will pay for a welding certification class I hope to take in the next month or two (/or CDL "A" training - I can pick one).

I'll get pics shortly, but quickly: the driver's side rear block is there, but the r.r. side block area is gone - crumbly.

Looks like the r.r. side can be jacked using the floor pan area?

Can I use spray foam in the opening for support with a board on the outside?

I've previously read about welding jack points to underneath cage mounting points - I'm planning on that later. This is initially just to replace the brake line so I can drive it on the road for a short time before starting a build (if I choose this candidate).

... Ok, I think I've just answered my question about spray foam - pretty sure I don't want to be melting it while welding in a cage.

Detail:
I have a jack stand under the l.r. lower control arm, but I'm not confident in it beyond getting the body up just high enough to look under with the wheel and tire still on. The arm has a compound curve that I don't like for a jack stand support, so I'm not counting on it. The jack is still on the lifting block, and I also have an oak 4x6 under the tire.

It's the r.r. I'm mainly concerned about for this question.

I'm planning on building cribbing before going under (i saw that suggestion before as well). And, this is outside on gravel, dirt, and no cover. And a slight incline.

Brake line replacement is a lot easier on full- size vans, that's for sure. Plenty of room underneath while on the ground.

Re: How to reinforce a rusty BMW jack point?

I would be very hesitant to take on a cage as a first welding project...they're way harder than they look and they look hard.

Using spray foam to back a plate you are trying to weld is not common practice... they have fire retardant spray foam which you can use to fill factory holes and gaps between fuel tank+engine compartment from the driver, or at least we've done it without backlash during tech. But I don't think that's the question you are trying to address.

Is there no better shells available? I would be hesitant to invest the time and money into caging a shell that has literal holes in it from rust.

Full Ass Racing (Captain)
#455 Piñata Miata - 1990 Miata   |   #735 BMDollhÜr 7Turdy5i - 1990 735i (Sold)

Experienced race-loser, 1x winner

Re: How to reinforce a rusty BMW jack point?

duthehustle93 wrote:

I would be very hesitant to take on a cage as a first welding project...they're way harder than they look and they look hard.

Using spray foam to back a plate you are trying to weld is not common practice... they have fire retardant spray foam which you can use to fill factory holes and gaps between fuel tank+engine compartment from the driver, or at least we've done it without backlash during tech. But I don't think that's the question you are trying to address.

Is there no better shells available? I would be hesitant to invest the time and money into caging a shell that has literal holes in it from rust.

If you have never done a cage, or have limited welding skills take it and have it done. The last thing you want to do is show up at a race, after spending time and money and fail tech.

"get up and get your grandma outta here"

Re: How to reinforce a rusty BMW jack point?

On the subject of BMW jack points. My E36 had really bad jack points when I got it. I cut the bottom of the rockers open, cut out all the rotten jack point structure, then welded in spreader plates inside the rockers and welded in pieces of roll cage tubing vertically so they pointed out towards the ground. Then patched back up the big holes and finally trimmed the tubing so it was roughly 1/2" protruding from the bottom of the rockers. So now my jack points are pieces of 1.75" roll cage tubing. Worked great, but you need welding skills.

20+ Time Loser FutilityMotorsport
Abandoned E36 Build
2008 Saab 9-5Aero Wagon
Retired - 1989 Dodge Daytona Shelby 2011-2015 "Lifetime Award for Lack of Achievement" IOE, 3X I got screwed, Organizer's Choice

Re: How to reinforce a rusty BMW jack point?

TheEngineer wrote:

On the subject of BMW jack points. My E36 had really bad jack points when I got it. I cut the bottom of the rockers open, cut out all the rotten jack point structure, then welded in spreader plates inside the rockers and welded in pieces of roll cage tubing vertically so they pointed out towards the ground. Then patched back up the big holes and finally trimmed the tubing so it was roughly 1/2" protruding from the bottom of the rockers. So now my jack points are pieces of 1.75" roll cage tubing. Worked great, but you need welding skills.

This is a great idea... I should really do this. Seems like a better alternative to waiting for our pinch welds to stop bending (they just keep on going and going! lol)

Full Ass Racing (Captain)
#455 Piñata Miata - 1990 Miata   |   #735 BMDollhÜr 7Turdy5i - 1990 735i (Sold)

Experienced race-loser, 1x winner

Re: How to reinforce a rusty BMW jack point?

Yes, agreed: I believe all those who say cages are hard. I'm likely to take that welding class (mentioned above) next month (it's company funded!), and I'll need to practice after.

TL;DR:
duthehustle93 - yes; WAY too many candidates. But it looks like the rust is primarily rocker area, which shouldn't be too bad - right?

Mr.Yuck - understood, but that's why the welding class. Plus, I know a fabricator who does (primarily) drag race cars (cages, tube chassis, etc.) who could fix things when I make mistakes.

TheEngineer - [YES!] Thank you! I think I remember that description, now that you've shared it here. Did you tie them into the cage?

Add'l Detail:
This is a literal ”Under $500" E46 from a widely advertised, professional company, regular internet auction event, with the auction receipt to prove it.

But it's also a clean title, and I really want to drive it on the roadway for a while to determine its current 'intrinsic reliability' before deciding; after all, it's a German car and should be rock solid

It's also a "Ticket Me Red" BMW, so I'll anticipate penalty laps from the B.S. judges just for kicks ... because BMW = Easy Button. And anyway, I won't care about penalty laps.

If I build it, I won't have to replace the r.r. window I smashed to get into it when I picked it up at the impound lot. That was the first part of the dead battery issue.

S&W is right down the road, and I can go there to get a custom cage bent - of course, AFTER I remove the interior and install the seat (Bimarco Hummer).

I have plenty of time, I'm funding - and building - this myself, over time, and my "win" will be getting a car to pass tech - nothing more. Though, of course, I also want to get it on the track when it does.

I'll deal with an entry to an actual race, as opposed to a test and tune day, after passing tech.

And then, after an initial build, if I can become creative enough to come up with an idea to contend for the I.O.E. (the "real" win), then that would be my ideal.

Re: How to reinforce a rusty BMW jack point?

Lemon_Newton-Metre wrote:

TheEngineer - [YES!] Thank you! I think I remember that description, now that you've shared it here. Did you tie them into the cage?


Kinda. I didn't continue the cage tubes through or anything, but I did place the new points in the same area that the cage lands, so the new spreader plates are welded in on the other side from where the cage spreader plates are. That's about as tied in as I could get. I also made sure that the spreader plates for the jack points wrapped down around the main chassis rails of the car (as much as a unibody car has chassis rails, but the main box sections that run fore and aft). I put in a LOT of spreader plate so I could have it grab onto and spread the load as much as possible.

It did work well. I put the car on the lift after putting in the new jack points, and got lazy adjusting the pad heights on the lift arms. Normally when I don't get them 100% even the car just twists a little and compensates (talking like 1/4-1/2 inch off, not inches). The E36 lifted on 3 points... didn't twist at all. Felt good about that one.

20+ Time Loser FutilityMotorsport
Abandoned E36 Build
2008 Saab 9-5Aero Wagon
Retired - 1989 Dodge Daytona Shelby 2011-2015 "Lifetime Award for Lack of Achievement" IOE, 3X I got screwed, Organizer's Choice

Re: How to reinforce a rusty BMW jack point?

I have always wanted to do rally car pin stands. 
https://www.youtube.com/watch?v=O8ZyeCeoQn0

But I am too lazy.

Team whatever_racecar #745 Volvo wagon

Re: How to reinforce a rusty BMW jack point?

rb92673 wrote:

I have always wanted to do rally car pin stands. 
https://www.youtube.com/watch?v=O8ZyeCeoQn0

But I am too lazy.

Wholly Crap! Those stands make me nervous just looking at them. No lateral structure to the stands other than the top weld for the pin? And meant for 'uneven ground like we get with Rally cars'?

Thank you, no, not me - I won't be on their crew.

I think you're smart, not lazy.

Now, the 'pin receiver' function on the car - that's interesting.

As is, they'd have to prove to me EACH stand is capable of supporting the entire car balanced on the end of the pin without deformation, like putting it in a fixture in a press and and hitting it with the weight of the car. And they don't look like they'd survive that Q.A. test.

Though I _could_ be wrong...

Now, a reinforced top with a lateral component to each stand, such as a (minimum) triangular base space frame, would give me a lot more confidence they actually cared about crew safety rather than "How many can we easily put in the truck, while taking up as little space as possible?"

For that matter, regularly available, commercial-built jack stand with a 'pin' modification to the arm wouldn't be hard; might even be able to make a 'swivel-to-lock' function work safely depending on the strength of the pin - and the 'lock' function.

Re: How to reinforce a rusty BMW jack point?

TheEngineer wrote:
Lemon_Newton-Metre wrote:

TheEngineer - [YES!] Thank you! I think I remember that description, now that you've shared it here. Did you tie them into the cage?


Kinda. I didn't continue the cage tubes through or anything, but I did place the new points in the same area that the cage lands, so the new spreader plates are welded in on the other side from where the cage spreader plates are. That's about as tied in as I could get. I also made sure that the spreader plates for the jack points wrapped down around the main chassis rails of the car (as much as a unibody car has chassis rails, but the main box sections that run fore and aft). I put in a LOT of spreader plate so I could have it grab onto and spread the load as much as possible.

It did work well. I put the car on the lift after putting in the new jack points, and got lazy adjusting the pad heights on the lift arms. Normally when I don't get them 100% even the car just twists a little and compensates (talking like 1/4-1/2 inch off, not inches). The E36 lifted on 3 points... didn't twist at all. Felt good about that one.

Nice - as I think you should.

I think for clarity's sake, the not 'twist(ing) at all' was likely due to the quality of the welding and locating the spreader plates you put in so that nothing collapsed when the lift hit the tube ends. And - I'm extrapolating here - the cage was already installed, tying everything together.

3 points lifting straight (as compared to 4 points) I would expect - in all circumstances where:
1. the weight is spread roughly evenly among the 3 points, and
2. largely centered, and
3. the item is a solid object, and
4. the tube ends are close to an even height above the lift points, yes?

I've got rusty crusty underneath in the rocker area, so I'm thinking this through carefully before going underneath.

I'm pretty sure I need more cribbing - never TOO safe.

Re: How to reinforce a rusty BMW jack point?

Rally style pin stands are fine, so long as the car is designed for them. They're fine laterally because they use a fairly long Pin into a close fit tube in the car's rocker, often integrated into the cage. That holds the stands vertical with no real risk of collapsing sideways. They also shouldn't really rock forward/backward because the bases are wide enough. As long as you build the stands correctly they are plenty strong. In fact this style stand is actually how the BMW road side jack works on most cars, or did, I'm not sure if/when they changed it. But the E36 has plugs you remove from the side of the rockers, then the jack inserts a pin horizontally like those stands, and you lift (assuming they aren't rusted out).


My comments on flexing on the lift were just about chassis stiffness. Normal car when you don't have all 4 pads 100% level with each other the chassis will twist a little when lifting and all 4 points touch and support. My E36 didn't flex at all and left one pad just floating. I put it right back down and adjusted the pads better.

20+ Time Loser FutilityMotorsport
Abandoned E36 Build
2008 Saab 9-5Aero Wagon
Retired - 1989 Dodge Daytona Shelby 2011-2015 "Lifetime Award for Lack of Achievement" IOE, 3X I got screwed, Organizer's Choice

Re: How to reinforce a rusty BMW jack point?

Lemon_Newton-Metre wrote:

It's also a "Ticket Me Red" BMW, so I'll anticipate penalty laps from the B.S. judges just for kicks ... because BMW = Easy Button. And anyway, I won't care about penalty laps.

There's your new theme.

Capt. Delinquent Racing
RUST-TITE XR4Ti - '21 ARSE-FREEZE-APALOOZA  I Got Screwed
The One & Only Taurus V8 SHO #31(now moved on to another OG Delinquent)
'17 Vodden the Hell - (No) Hope for the Future Award, '08 AMP Survivor, '08 ARSE-FREEZE-APALOOZA Mega-Cheater

Re: How to reinforce a rusty BMW jack point?

DelinquentRacer wrote:
Lemon_Newton-Metre wrote:

It's also a "Ticket Me Red" BMW, so I'll anticipate penalty laps from the B.S. judges just for kicks ... because BMW = Easy Button. And anyway, I won't care about penalty laps.

There's your new theme.

That has to have already been done to death, hasn't it?

I mean, Ok, I support the idea that an old, stale joke that someone references over and over again can become funny again [ex.: "Badges? ..."]; but that's really about the subsequent repetition, not the old joke anymore (my life is full of these already).

But I can't imagine this idea has yet gotten to that point; I don't think it's old enough. I can only imagine it's in that interim stage, where even those who repeat it admit it's just sad, and tired, and unimaginative.

... but: if it hasn't been done that many times, in the east, yet; ... agreed - that's a brilliant idea.

Re: How to reinforce a rusty BMW jack point?

TheEngineer wrote:

[snip] As long as you build the stands correctly they are plenty strong.

I had serious concerns about the ones in the linked video.

TheEngineer wrote:

[snip] In fact this style stand is actually how the BMW road side jack works on most cars, or did, I'm not sure if/when they changed it.

I've used - or seen - that type of jack before (can't remember when or where right now), and I found it cool, but that jack had a lateral component to its flat base. The stands in the video looked like single tube stock, which is a very narrow contact patch.

My 2000 E46 has pads underneath at what I expect are the jack points (there's no manual).

I really like the idea of a place to attach jack stands to a race car which are clearly separate from - and coordinated with - the jack points. They could just be additional jack points for that matter, but I _really_ like that idea. I'm guessing the professional teams design that into the build. Hmmm...

TheEngineer wrote:

[snip] I put it right back down and adjusted the pads better.

I expected no less ;-)

Re: How to reinforce a rusty BMW jack point?

if you're already welding dont forget to reinforce the subframe on that e46, common failure point!