Converting/Modernizing front suspension

[bpestilence]

This is an idea that I am playing around with to upgrade the Talon. The first thing that I noticed when I installed my polyurethane bushing kit is that the Talon's suspension is overly heavy and has many more connections than most modern suspensions that I have worked on. So I am going to convert the MacPherson strut/ dual control arm setup to a more modern Anderson strut/ single control arm setup. This may sound like a lot of work, but after spending a lot of time looking at it and measuring things, it looks like it will require a simple set of brackets and carefully measured and drilled holes in the spindle.

Here is a picture I put together in MSPaint to show what I mean. I will get a much more detailed drawing together when I either renew my SolidWorks or figure out how to do it in ProE.

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I am also planning on making heim joint trailing arms. Together, I should elimiate the upper control arms, 4 ball joints, and half of each of the spindles. I want to know if anyone can see any major disadvantages to this. I know that I am going to be giving up easy camber changes, and I know that the brackets have to be very strong and well made, but this is well within my fabrication ability.

 

[PieEyedPiper]

Ah, SolidWorks. Do you have access to a good mill?
Very interesting idea. I'm excited to see the results.

 

[RipperXX]

I will be impressed when someone actually finishes a project of this magnitude. Seen to many good ideas and plans etc. And not enough executing.


But good luck.

 

[92awddsm]

I know that I am going to be giving up easy camber changes

Using cam bolts in the strut/spindle connection cam make for fairly easy camber adjustments.

 

[turbosax2]

What is the advantage of this besides less weight and less parts to maintain? Will you modify the struts or have to get different ones?

 

[bpestilence]

The new brackets will bolt to the struts in the same way that the fork bolts to it currently. Actually, since the forks are cast steel I will use them as the basis for the brackets.(getting a junkyard set) I don't think there are any OEM struts that will fit the bill, as I either need custom brackets or custom spindles.

Advantages:
1) Weight reduction
2) Greatly reduce the number of moving parts and fragile rubber boots
3) More negative camber change with a similar change in suspension travel
4) The ability to use camber plates instead of camber bushings (which are a b*** to adjust with the suspension loaded)
5) A big if: Hopefully free up some constraints to possibly improve the turning radius.

Disadvantes:
1) Could die if I design it wrong.

But, it won't be the first suspension parts I have fabricated, so I have a little more faith then I used to. You'd be surprised to see how thin those spindle brackets are on most new cars, anyway.

 

[Eagle 5]

I have thought of eventually doing this but requires lots of time that I don't have. I did make my own adjustable upper rear control arms. Very easy to do. Considering making adjustable lower arms more for weight savings and always nice to adjust of course. You could make fabricated front spindles or I believe they are cast steel which means you could weld to them. Though fabricating would be much better. I have thought of how to remove the lower a-arm and replace it with a tubular one (one company made some) or there is a thread on here where a member made a tubular "k" member and made lower arms that connected to the "k" member and another location on the front.

 

[Dallas J]

So what you're doing is getting rid of something that has a decent camber gain/degree of roll to something that has essentially none? The 2g suspension because of the double wish bone is largely known for its superior suspension geometry and design over a 1g's McPherson strut. Another thing is you lose the ability to get the caster 2gs like. On top of all of that, if you get into a situation where your lower control arm is pointing upwards (for a lack of better terms) youre gonna get into the situation where your roll center drops dramatically. This will increase your roll moment and overall roll which will further reduce your camber.

Also, you're creating a lever arm that is gonna bend the shock in any deflection of the assembly which will happen unless you make it really burly. The bending force will kill your seals.

If you look at the evo's, sti's, and M3's that get heavy into racing, they have to run a ton of static camber to combat it. Some of the auto-x M3s ive seen run -3.5 to -4.0 degrees of static camber.

 

[Defiant]

The design is interesting, but it's not a performance suspension. It's a bean-counter suspension, which is how the world got screwed into using Fearsome struts in the first place. And yes, you'll need a lot of strut to carry the additional loads.

 

[99gst_racer]

And yes, you'll need a lot of strut to carry the additional loads.

Exactly what I was thinking as well. The 2G shock is not capable of supporting the weight of the front of the car by themselves. If you remove the spindle, then you'll need a beefier shock shaft like 1G's have.

 

[bpestilence]

The 2G strut takes 100% of the load. The spindle simply connects to the upper control arm which keeps it constrained laterally. The spindle itself is holding no moment or tension.

I agree that the strut will have an additional moment at the shock rod. However I think if you look at the geometry more closely you will see that the Anderson strut will produce more negative camber change for the same suspension compression. Think about the upper control arm as "taking away from" the camber. If the upper control arm were the same length as the lower control arm, there would be no change in camber at all when the suspension compressed. The Anderson strut eliminates this, hence more camber change.

There is a reason that the Lancer, the Impreza, and virtually all new cars use this sort of suspension, and it isn't for cost savings in these expensive cars.

 

[99gst_racer]

The 2G strut takes 100% of the load. The spindle simply connects to the upper control arm which keeps it constrained laterally. The spindle itself is holding no moment or tension.

Yes, it holds freestanding weight just fine, but not lateral forces. Remove the upper control arm and take the car autocrossong, and the shaft of the shock is sure to bend. To change the 2G over to a McPherson strut design, you will definitely need to use a stronger strut that what the 2G's use.

 

[eclipsh]

Funny... I've thought about doing the opposite with my 1g and making it a double wishbone front end because all the car rags constantly rave about double wishbone front ends and their superior handling.

Why not just set up an upper a arm lower on the chassis to allow for wider wheels and move it slightly behind the lower a-arm to increase camber in turns?

 

[bpestilence]

Okay, thanks for the feedback. I will analyze the moments and the geometry more carefully in ProE before I go ahead with this. But I will get started on the heim trailing arms.

 

[Dallas J]

I think if you look at the geometry more closely you will see that the Anderson strut will produce more negative camber change for the same suspension compression.

Sorry, but your simply wrong on this. Ive spend probably a good 20-25 hours on the Lotus Suspension design software designing the suspension on our FSAE car and have seen the camber gains of your strut set up.

The problem is the line from your lower ball joint to the upper mount can only change by the lower ball joint arcing outwards. This will only happen if your lower arm is angled downward and rotates towards vertical on bump/roll. Having your arms at a large downward angle creates a high roll center which if it gets above the center of gravity will cause a jacking effect.

With the double wishbone the camber is controlled by the location of the upper and lower ball joint. Because the lower arm is longer than the upper arm it has a larger arc. Under compression the upper arm moves farther to the inside than the lower giving you a camber gain. By angling the upper arm more at static equilibrium, under bump you'll get a larger camber gain. Thats why you see much different angles on race cars that have larger suspension travels.

 

[Locke]

There is a reason that the Lancer, the Impreza, and virtually all new cars use this sort of suspension, and it isn't for cost savings in these expensive cars.

The McPherson strut (which is what your illustration depicts, vs. the factory multilink suspension) is only used in modern design to reduce costs and allow for a smaller overall suspension package. Thats really about it.

The MacPherson strut package doesn't allow vertical movement of the wheel without either camber change or lateral movement. It lessens your ability to choose how camber if affected during motion, and roll centre changes are worsened. Since the wheel will lean with the body, it will promote understeer.

If you are considering Lancer's and Impreza's expensive cars, I would largely disagree. As well, vehicles designed for performance only (read: Race car) use double-wishbone or multi-link suspensions, and for good reason.

 

[Cs4g63]

So this basically comes out to making a 2g front suspension like a 1g front suspension? I just want to clarify, im not trying to rag on the idea, because that is what it looks like to me.

 

[99gst_racer]

So this basically comes out to making a 2g front suspension like a 1g front suspension? I just want to clarify, im not trying to rag on the idea, because that is what it looks like to me.

Pretty much, yeah.

 

[bpestilence]

Fine, fine. I will keep the suspension as is. I guess I will concentrate my efforts on making lighter, more adjustable pieces to replace the factory pieces.

 

[jtmcinder]

The trade-offs are a little more complicated than people are suggesting.

The main advantage of double-wishbone is geometry.

The main advantages of struts are weight and travel.

So, if the racing that you do requires good control of the contact patch and is done on flat surfaces, the conclusion is in favor of double-wishbone. 2Gs are the road-racing DSMs.

If the racing that you do is on lousy surfaces, the conclusion is in favor of struts. 1Gs are the rally cars.

- Jtoby

 

[Dallas J]

Also, 1gs are the stock suspension launchers. Good tire contact under full compression in the rear and extension in the front.

 

[ACM]

The trade-offs are a little more complicated than people are suggesting.

The main advantage of double-wishbone is geometry.

The main advantages of struts are weight and travel.

So, if the racing that you do requires good control of the contact patch and is done on flat surfaces, the conclusion is in favor of double-wishbone. 2Gs are the road-racing DSMs.

If the racing that you do is on lousy surfaces, the conclusion is in favor of struts. 1Gs are the rally cars.

- Jtoby

The only Group B rally cars I remember not using double wishbone suspension at both ends were the Quattro and the 6R4...The prime reason most rally cars use struts is because the series production car they're based on has them, and the regs require the same design suspension to be retained.

That applies as far back as the old Grp 1/2 cars (think Mk 1/2 RWD Ford Escorts), Grp A from the 80's onwards, and the current classes - the only class that allowed purpose-designed race cars was Grp B. I think most of the purpose-designed Baja racers also use A arms (the few that I've seen). Oh, Grp 4 allowed more leeway due to the limited build quantity, producing cars like the R5 Turbo - double wishbone both ends again.

Packaging for long travel double wishbone suspension is horrendous however.

Charles

 

[Jon Lane]

Fine, fine. I will keep the suspension as is. I guess I will concentrate my efforts on making lighter, more adjustable pieces to replace the factory pieces.

I was under a new EVO the other day and started thinking about how to convert the DSM 2G to their front susp. parts and pieces. A nice alloy, unified lower arm seems a nice touch...

 

[eclipsh]

I was under a new EVO the other day and started thinking about how to convert the DSM 2G to their front susp. parts and pieces. A nice alloy, unified lower arm seems a nice touch...

I've actually been wondering about using the lower arm and hub/brakes (possibly better front struts too?) in a 1g.

Since this is somewhat related... My buddy Pagosa DSM and I were bench racing over a couple beers the other night and were curious what kind of camber gains an Evo gets when the wheels turn versus a 1g. If they have more gain how do they do it besides caster? Anyone know the answers?

 

[Defiant]

Kingpin inclination angle.