Making My Own Control Arms

The OEM arms are most likely die cast. After clarifying the hardness measurements with the lab, the hardness is uniform across the surface and cut cross-section indicating that there is no heat/hardness treatment, and though this doesn't directly exclude drop-forging it does indicate otherwise.

Drum roll please!

So I've gotten my a few quotes back on a fully billet arm from 6051-T6 or 7075. The costs are indicative as I haven't designed the arms for manufacture yet as there is a bit of back and forth between available aluminium grades and then designing the arms to suit that grade and machining before I settle on a design specifically. Right now though, for the equivalent of 2400 GBP I should be able to make my own arms, with bushings and a replaceable ball joint - about 600GBP cheaper than a full set of the pattern parts from Eurospares. With a bit of shopping around and rework I am aiming to pull that below 2000 GBP.

To reuse the existing arms; the current bushings are about 100GBP a pop, and you need 8... so 800GBP + ~400-800GBP in reworking the arms to fit ~200-400GBP in ball joints... I'm not even sure it will be worth exploring that option unless I encounter a specific roadblock with my from scratch design. Right now the biggest issue I can see if finding a bushing that fits in the space Maserati has made... time to hit the catalogues.... I am still looking into how to rework the existing arm, but I can't finish measuring the cup until I'm home as I need a few different tools.

bravo

So no fun pictures yet I'm afraid, but info to share still!

I've been following up with different manufacturers, locally, in China and in Malaysia. Costs range between $580USD-$2700USD per lower arm, with some places requiring me to supply my own stock and others supplying the stock as part of the job. At the moment, I'm looking at one of the more mid-range outfits in China as I know they're a supplier for a number of major listed companies and have a good reputation. They also have fantastic response time on enquiries and adjustments as I make them. With their input I've narrowed down the field of potential materials.

Without getting into the nitty gritty right now (I'll save it for once I've completed the FEA), the main factor that will affect how strong a material is, is Ultimate Tensile Strength (UTS). If you have two Aluminium grades, the difference in density is negligible, so 4343 and 6061 are both 2.7g/cm^3. So if you have one grade that is 4 times the UTS as another grade you can reasonably assume that you will need 1/4 the mass. This is the reason that you can often get lighter parts using steel over aluminium as it is ~3 times heavier but often 4-8 times stronger, so you can use less material. There are other factors such as stiffness, hardness and such that all come into play but I'll save that for another post. This is all to give the background on some of the fun materials I've been looking into.

Since the OEM arms are so expensive, I've looked into some of the aerospace grade 7XXX series aluminium. 4343 has a UTS of ~110MPa and the grades I've been looking at are from 490-690MPa. The OEM arms weigh in at ~1.9kg, and so in theory the arms I'm making could be of equal performance weighing in between 300g-450g for the lower arm... And yes, it sounds super weird that a 1.7t car could be supported on a 300g piece of aluminium! One of the more unusual outcomes is that it could potentially be cheaper to make it from one of the higher grade alloys as I may be able to use a thinner piece of stock, but that will just come down to luck. More realistically the going for a 7XXX over a 6XXX will cost 15-25% more.

I ended up asking for quotes in really exotic grades, and I was able to get two manufactures to make the parts out of 7075-T621, so for the moment I'll be doing my final designs with this alloy in mind. I was trying to find a fantasy grade of 7178-T62, and one place was able to do it - but I had a minimum order quantity of 2t! Enough material to make ~6600 lower control arms (probably closer to 2000, by the time you factor in wastage) which seemed a wee bit excessive...

Anyway, that is where things are at right now! I'll hopefully select some bushings and a ball joint over the coming month and can start getting parts made!

Just an update on what’s happening with my car as it’s been sitting in a workshop for a few weeks now; mainly waiting for parts. Control arms were one issue and a problem engaging reverse the other. Replacing the gear lever with a Hills version only part fixed the latter problem as It turns out the power unit is playing up as well. I’ve sourced a 2nd hand replacement and all work should be done this coming week (including fitting a FD DBW conversion) - fingers crossed the car will then drive and behave like it should

Great initiative and awesome work by lambertius! Im rooting for you and hope you'll come up with a great build on these control arms!

Im driving a 2010 Granturismo 4.7L F1. Would love to see you design one for GT/Quattroporte as well!


Also, this might be silly but I came across this websit that rebuilds Lambo control arms https://gallardocontrolarms.com/. Seems like a similar problem to our Maseratis' ball joints, is it?

Certainly looks a similar problem with The Lamborghini ball joints.

A few posts so I thought I should follow up.

I've been a bit slack on the project the last few weeks, I've gotten quotes back so now I need to hammer out the meat of the design which is really only 2-3 days of work. What the real hold up has been is that I haven't gone bushing and ball joint hunting because that one is a 'how long is a piece of string'. I've got my car in a body shop at the moment, and while I didn't have it here distracting me I've been giving my other cars and projects some attention. Though none of it is related to this post, I thought I would let y'all know what I've been doing the last two weeks.

1- Applying for Medical School, all the applications have opened in Australia.
2- Characterising the way the brakes work on a couple of different cars. This is part of, but not directly related to my project of redesigning the brakes for the Maserati. Below is some raw data from my MX-5 running RE003s. Once you account for zero drift and a few other things braking forces averaged 1.2g in a 60km/hr-0km/hr test, quite impressive. I also did it on my BMW, and collected data on stopping distance, time to stop, rotor temps and everything else I need to cross-verify and validate a simplified model of rotor temps I'm making to teach people how to select brake pads. The data is raw, so don't read too much into it. All of this data is courtesy the help of my lovely fiancee.







3 - I changed the rotors on my MX-5



4 - Here is something car guys don't get to say very often - my MX-5 is a completed project! Everything is completely done! Until a rock hit the edge of the windscreen and sent a crack up the middle of the glass... Thankfully my insurance (Shannons) covers a no excess windscreen every 12 months so it is getting replaced tomorrow, which means I can finish my paint detail the day after and then go take some photos of the last car I spent two years fixing up!



5 - Rebuilding my window reg
6 - Cleaning up my headlight lenses and getting the inserts painted.
7 - Trying to finish a flashlight project that has been running way too long... I pulled the batteries out of storage a few days ago and accidentally shorted one out. They're 20A batteries and I need two of them.

Paulrv2 said:

Just an update on what’s happening with my car as it’s been sitting in a workshop for a few weeks now; mainly waiting for parts. Control arms were one issue and a problem engaging reverse the other. Replacing the gear lever with a Hills version only part fixed the latter problem as It turns out the power unit is playing up as well. I’ve sourced a 2nd hand replacement and all work should be done this coming week (including fitting a FD DBW conversion) - fingers crossed the car will then drive and behave like it should

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Fingers crossed it drives and behaves not line mine! I've got some good spares from all my transmission hullabaloo, so if you still need parts send me a PM. Not all of it is trashed.

leonidas said:

Great initiative and awesome work by lambertius! Im rooting for you and hope you'll come up with a great build on these control arms!

Im driving a 2010 Granturismo 4.7L F1. Would love to see you design one for GT/Quattroporte as well!


Also, this might be silly but I came across this websit that rebuilds Lambo control arms https://gallardocontrolarms.com/. Seems like a similar problem to our Maseratis' ball joints, is it?

Click to expand...

There is an old thread on here where someone was trying to come up with a similar solution for our arms, I ended up PMing them before taking this on to work out why they never completed it. He was held up with costs, and the arrangement of our arms isn't quite as convenient as the Gallardo to be reworked. So the issue is present across the next generation as well? If I can pull this off successfully, and someone can source me scrap parts for measurement I'd be happy to take it on. Obviously a bit of time before I get to that as this is still ongoing, but yeah - if someone finds the parts at any point send them my way!

So small update - I found a few websites that have bushing selection catalogues that I can go through online. If anyone has any suggestions for places to look at please let me know.

The websites are kind of helpful at the moment as I've broken a bone in my left foot making it a bit hard to operate my 3 pedal cars...



Anyway, back to the topic at hand...

Whiteline had the best site for searching based on parameters rather than vehicle so I used them. The critical dimension is length - since that is what seats the control arm into its mounting position.

I managed to find a few bushings used on the Holden Monaro from the early 2000s, so a contemporary of our cars with similar power and weight, so the bushing is a good candidate. I'll need to make a little sleeve to take up the slack in the bolt hole (ours ID is ~14mm, but the bushings I'm looking at are 19mm) or replace the bolt (need to get a better look at the arm mounts before doing that). Either way, I have a good candidate for a common performance car, so there will be plenty of aftermarket options.

Now the good news in this little adventure is that full set of four bushings (per arm) of an appropriate length fitted to my arms would be about $120AUD (~60GBP) compared to $680AUD (~340GBP). The bad news is that I can't find any bushings that match our OEM spec, so refurbing the old arms would still be $$$$ even if there were an economical solution for the ball joints.

In an odd bit of luck, a friend of mine who I was chatting to went to high school with the son of the owner of Whiteline. He will try and put me in touch - who knows, we might be able to get a set of fitted bushings anyway!

Just following up on the back of my remark about changing the bolt. The other idea would be get the actual subframe mounts remade from a little bit of billet steel as part of the process. They're bolted in place, so it should just be as simple as 'make part to accommodate bushing length'. This would then allow me to spec any bushing and bolt combo I want. So I could do an M3 for example, pretty much allowing for an infinite choice of aftermarket bushings. This would drive up my parts costs a bit, but would significantly improve serviceability in the long term.



Decisions...

I'd have thought changing the forks (23) would be easier but I believe they are not all the same part throughout the vehicle?

I may actually have to change the forks anyway. For whatever reason our bushings are super skinny compared to what is out there. If I go too large, then I may take up all the space in the mounting position. This is a major pita, you wouldn't want to pay someone to do this job for sure!

I don't know if this helps or not, but a lot of our cars bushings are shared with older Ferraris (particularly 456/550). Energy Suspension makes poly bushes for our size (186493, 186494) but that only leaves one (186496) which I don't think cross-references with any Ferrari.

I'm also not sure if the Ferrari 456/550 wishbones have the integrated ball-joint, by the way which wishbones of the Maserati have replaceable ball joints? I know there were a few but I can't seem to recall.

Twinspark said:

I don't know if this helps or not, but a lot of our cars bushings are shared with older Ferraris (particularly 456/550). Energy Suspension makes poly bushes for our size (186493, 186494) but that only leaves one (186496) which I don't think cross-references with any Ferrari.

I'm also not sure if the Ferrari 456/550 wishbones have the integrated ball-joint, by the way which wishbones of the Maserati have replaceable ball joints? I know there were a few but I can't seem to recall.

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None of the ball joints are replaceable, but the front upper only needs the outer part of the arm rather than the whole thing.

I had a look at the poly bushes as there have been a few candidates over the years. Like the others these lack the design where the mounting bolt locks an inner shaft and the rubber has a metal sleeve which rotates around that shaft. The rubber does not go into sheer when the suspension arm moves with the OEM bushes. Any solution where it does isn’t suitable in my view.

Zep said:

None of the ball joints are replaceable, but the front upper only needs the outer part of the arm rather than the whole thing.

I had a look at the poly bushes as there have been a few candidates over the years. Like the others these lack the design where the mounting bolt locks an inner shaft and the rubber has a metal sleeve which rotates around that shaft. The rubber does not go into sheer when the suspension arm moves with the OEM bushes. Any solution where it does isn’t suitable in my view.

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Its funny you said this. I had been wondering why the Maserati bushings were such a weird dimension for a while. I'd not seen anything laid out the way these ones are and it just didn't make sense. You're a low volume manufacture, everything I've seen in these cars shows me that they used the cheapest parts available whenever possible and it just doesn't make any sense that they would go and get some weird unique dimension for a bushing. That would be way too expensive. It eventually hit me, the bushings are a common size padded out, presumably so that you could only get the part from an OEM supplier.



Upper is on the left, lower is on the right.

What you can see is the metal plates that Zep mentioned, rubber, the metal casing, rubber, and the metal plate. You can see the metal shaft inside the bushing.



The real length of the bushing isn't 61mm, but 52mm (rubber to rubber). The end metal is a piece of stamped sheet which is then pressed onto the central shaft. There is absolutely reason to do this except to pad out the length of the bushing. Every other setup I've seen would normally just use a washer which is a separate part and not integrated into the bushings. Most bushings have an internal 19mm diameter and supply a central shaft as a separate part which you need to assemble.

This means that the bushing dimensions are a much more common than I initially realised and it has made it a lot easier to source a similar match. My plan is to implement the bellow. Like the OEM bushings I'll be padding out the fitment, but my insert will be designed to be reused.



With the bushing choice made a lot simpler, I need to source a ball joint. I'm currently thinking of forgoing the ball joint altogether and using a rose joint. It will be a lot cheaper in both manufacturing and parts, and a lot easier to assemble. It should also improve the stability of turning in with the trade off being a slightly harsher feel.

There is a second metal sleeve attached to the rubber that allows rotation around the inner sleeve that isn’t in your drawing.

There's a company in the USA that makes replica bushings (MIE). Also if I'm not mistaken the 4200 has 3 bushing sizes as the front/rear uppers have a different Part# and diameter.

Zep said:

There is a second metal sleeve attached to the rubber that allows rotation around the inner sleeve that isn’t in your drawing.

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I don't have an account and can't see them, but it seems that there are some good descriptive pictures here.
https://www.ferrarichat.com/forum/threads/bushings-why-the-550-is-awesome.408186/

Enz0 said:

I don't have an account and can't see them, but it seems that there are some good descriptive pictures here.
https://www.ferrarichat.com/forum/threads/bushings-why-the-550-is-awesome.408186/

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I think you have made the same search as me....
...and I couldnt find any cross sectional diagrams of a Flanbloc either. Plenty of other types of 'flexible' bushings.
Trade name, right...? Is it intellectual property or that they just dont get used widely..? Either way, I'd like to see one cut one in half....

TimR said:

I think you have made the same search as me....
...and I couldnt find any cross sectional diagrams of a Flanbloc either. Plenty of other types of 'flexible' bushings.
Trade name, right...? Is it intellectual property or that they just dont get used widely..? Either way, I'd like to see one cut one in half....

Click to expand...

Well I’m not doing it again!