Tubular front k-member/sub-frame design

[Ludachris]

I know it's been talked about before, and we've had some small vendors who tried to make them available (and never did). But why not use this thread to start spec'ing out a front sub-frame/k-member for the 1g?

I'd say it would be best to make something that bolts right in and uses all the stock mounting points so that all the stock suspension pieces can be used if so desired. If there are provisions to change the suspension mounting points, like moving them up for lowered cars, that would be great, so long as the stock points can still be used along with factory control arms.

I'm thinking we'd want to focus on steering rack provisions that will make both drag racers and road racers happy. And maybe there should be a couple options that make the sub frame stronger for road racing (side loads), and lighter for drag racing (which doesn't see side loads). The road racing version might have a few extra braces.

Take a look at the aftermarket k-members designed for the Mustang here:
BMR Fabrication Products

You'll notice there are a few options to choose from that changes the design.

Thoughts?

 

[tsi87889095]

I would like to make these for are cars. It will take help and research from you guys to be able to do this. I have all the tools to make these but i dont know what drag racers prefer over road race and rally. I know drag racers want light were road and rally want strong but light also. I am going to make my first project making lower control arms for the 1Gs and then i would like to make the 2Gs uppers for the front and rear. The 2Gs wont be to hard the 1Gs will be a little more in depth. As far as the 1G control arms i can put a mooge ball joint in the control arm. Its the same style we run in are nascar cup cars. They are a lot stronger than factory and they just thread in so they are easy to change also. You would just have to ream the spindle which is not hard. They also will be tig welded. I would use the factory bushings. Let me know what you guys think and more info on drag and road race setups for the sub frames.

 

[Ludachris]

Let's create a separate thread for the control arms.

As for the k-member, I would think the drag racers would want light weight with an option to not use the power steering, if in fact, that can save weight. They probably won't need the provisions for the north/south sub frame braces that connect the k-member to the front cross member where the front motor mount connects.

Road racers on the other hand will want strength and less flex, provisions for the north/south bracing, provisions for the power steering and possibly provisions for a different steering rack that might be a better option. If it's possible to add a secondary attachment point for the lower control arm for lowered cars, that would be a nice option too, but not terribly necessary, as it would solve the issue of roll center - which we can only address right now using longer ball joint stems (the Chrysler ball joints) and tie rod end spacers - a relatively cheap solution. Any improvements for reduced flex will be welcomed. Room for brake ducting would be nice, but that will probably be addressed with the control arms more than the k-member.

 

[CPHunter]

Me as a drag racer would like to see a tubular k that's light weight. Removes both north south bars and something that fits us auto guys drag racing. Stock size bushings would be great so if we ever need them replaced , we can just buy some replacements, unless there's a better soloution. ( poly. Or solid where appli. Like motor mounts )

 

[kawgomoo]

there in lies your problem.

People with the knowledge and skill to build a subframe, are not going to build one that accepts all the stock junk.

They are going to engineer out the problems as they go. Control arms and subframe go hand in hand.

I dont know anyone that would want to change teh subframe, only to save a few pounds. When for the exact same amount of money they could have one that actually addresses and corrects all {or some} of the major problems.

Steering column provisions is where you lost me. What does the column have to do with the k member? dsm's dont even have a steering column, just a retract, some switches and a bearing up top.

Steering Racks on the other hand...well thats the hard part. Can the entire dsm community really decide on a rack they would all be happy with? would the stock non power rack be fine?

When i tube out my k-member, arms and pretty much everything else underneath ill be glad to jig it up and knock some out for whoever wants one...but i make zero guarantees to how many stock parts will bolt on..if any.

im an offroad guy by nature, so i tend to use the same size poly bushing and spherical balls as i would in the buggies...more than strong enough, but with no dust boots or any way to retain grease i dont know if u street guys would be that into them.

 

[Ludachris]

there in lies your problem.

People with the knowledge and skill to build a subframe, are not going to build one that accepts all the stock junk.

They are going to engineer out the problems as they go. Control arms and subframe go hand in hand.

I dont know anyone that would want to change teh subframe, only to save a few pounds. When for the exact same amount of money they could have one that actually addresses and corrects all {or some} of the major problems.

Steering column provisions is where you lost me. What does the column have to do with the k member? dsm's dont even have a steering column, just a retract, some switches and a bearing up top.

Steering Racks on the other hand...well thats the hard part. Can the entire dsm community really decide on a rack they would all be happy with? would the stock non power rack be fine?

When i tube out my k-member, arms and pretty much everything else underneath ill be glad to jig it up and knock some out for whoever wants one...but i make zero guarantees to how many stock parts will bolt on..if any.

im an offroad guy by nature, so i tend to use the same size poly bushing and spherical balls as i would in the buggies...more than strong enough, but with no dust boots or any way to retain grease i dont know if u street guys would be that into them.

Those with knowledge and skill to build them can build them with stock connecting points if the majority want them that way. Companies like BMR could probably change the Mustang sub frame and control arms, but instead they made factory replacements that are stronger, lighter, and are adjustable. I think that's all we'd need. Lighter and less flex are a couple big improvements over stock.

What stock junk are you referring to? Steering rack (edited my post to reflect rack and not column), control arms, sub frame braces, motor mounts, what else? If the builder isn't willing to produce a piece with provisions for things needed for a specific application (like road racing), then that's not the builder I'd want building them. I'd want a builder who listens to what we need and designs a piece around our needs, not what he thinks we need. I for one, wouldn't care to try and drive my car around with 255 wide tires without power steering. I could, but it would be more work than fun. This isn't going to be a dedicated race car.

 

[turbotalon1g]

I am talking with MA Performance right now (i refer to them as MAP, so don't get lost). If we can generate enough interest and get some dedicated buyers lined up they have enough 1Gs around to start looking into this.

 

[123abc]

As for a steering rack should we not be looking to electrically power assisted ones with different mounting points to correct bump steer?

 

[Ludachris]

As for a steering rack should we not be looking to electrically power assisted ones with different mounting points to correct bump steer?

I'd say that could be an option, but I wouldn't make it the only option. Can't we address bump steer in other ways too, like bringing the roll center back into the original design geometry with longer ball joint stems and tie rod end spacers?

 

[123abc]

I'd say that could be an option, but I wouldn't make it the only option. Can't we address bump steer in other ways too, like bringing the roll center back into the original design geometry with longer ball joint stems and tie rod end spacers?

For sure, but why keep using those things on a custom tube subframe when you could build those features into it? To be honest, in my mind I can't see many spending around 1k or more on a tube subframe just to have the stock geometries, and be slightly lighter than stock. Dollar for dollar, it doesn't seem worth it unless you can use a different, more popular, newer steering rack which would eliminate the stock power steering bs.


This is just my opinion though.....

 

[2gdanny]

there's this guys local to me he does good work, and i have seen him doing k members for bmw's, supras and other's he also did alex car from dogbox his front end and k member all tube.
all it would take is some talking to him and bring him a stock sub frame/ k member and im sure he would have no problem making it.

http://www.maximumpsi.com/gallery/dogbox1.jpg
http://www.maximumpsi.com/gallery/dogbox4.jpg
http://www.maximumpsi.com/gallery/dogbox2.jpg
http://www.maximumpsi.com/gallery/dogbox5.jpg

Maximum PSI - Custom Automotive Installation, Fabrication & Tuning

just an idea.

 

[Ludachris]

For sure, but why keep using those things on a custom tube subframe when you could build those features into it? To be honest, in my mind I can't see many spending around 1k or more on a tube subframe just to have the stock geometries, and be slightly lighter than stock. Dollar for dollar, it doesn't seem worth it unless you can use a different, more popular, newer steering rack which would eliminate the stock power steering bs.


This is just my opinion though.....

To be able to sell them in the DSM market, I think they have to be priced less than $1k no matter what features they have built in. I'm not sure it would make sense to have some guy building them. We'd be better off trying to get a shop that makes these for other cars (like BMR) so that we can keep the price down and have a quality product we can depend on. I know it's a long shot, but it's worth a try. We can try and get exotic on the options, but the reality is, there aren't many popular options out there for steering racks at this point, so it makes sense to keep the stock rack as an option since many will want it.

 

[turbotalon1g]

^Pretty much hit that on the nose.

If we can get the parts priced like the BMR stuff I wouldn't see an issue with sales it would still be a decent amount of $$$, but to those that would want to lose the weight they would buy it.

 

[slowgsr]

I use paul's 99gsxracer (I beileve thats his screen name). It replaces the front crossmember, as well as the bars that go towards the control arms.. actually it completely removes the bars that go to the control arms. It incorperates a solid mount, and gives a ton of room for a big downpipe. I really like mine, its great for drag racing. Im unsure how well it would work for road racing.

 

[Ludachris]

I use paul's 99gsxracer (I beileve thats his screen name). It replaces the front crossmember, as well as the bars that go towards the control arms.. actually it completely removes the bars that go to the control arms. It incorperates a solid mount, and gives a ton of room for a big downpipe. I really like mine, its great for drag racing. Im unsure how well it would work for road racing.

That's not the k-member, it's a cross member which connects the front frame rails and has the front motor mount - it doesn't touch the control arms. It is connected to the k-member by north south braces. The k-member subframe, which we are talking about, holds the rear motor mount and the attachment points for the control arms. It's a pretty substantial piece of metal.

 

[kawgomoo]

luda, i know you have high hopes. But i fear your goals and desires are completely unrealistic.

you want adjustability and complete bolt on.

you want quality material and construction.

you want it for a car that was never terribly popular and hasnt been in production for AT LEAST a decade.

You want all this at mass produced china made prices.

BMR i know is your holy grail. But there stuff is crap. Sorry to break it to you.

No fabricator worth his weight in dog shit is going to waste there time building a one off chromoly tig welded K member for a 1000 bucks hopefully to sell 5 of them to guys that will bi*** endlessly it didnt incorporate there one specific design idea.

Its just not going to happen.

BMR is mass producing mild steel mig welded junk subframes for one of the most popular cars in america. They make there money little by little.

There just isnt that market for DSM parts. And if anyone is going to build one, they are going to take the TIME to do it right.

Time = Money.

 

[Ludachris]

luda, i know you have high hopes. But i fear your goals and desires are completely unrealistic.

you want adjustability and complete bolt on.

you want quality material and construction.

you want it for a car that was never terribly popular and hasnt been in production for AT LEAST a decade.

You want all this at mass produced china made prices.

BMR i know is your holy grail. But there stuff is crap. Sorry to break it to you.

No fabricator worth his weight in dog shit is going to waste there time building a one off chromoly tig welded K member for a 1000 bucks hopefully to sell 5 of them to guys that will bi*** endlessly it didnt incorporate there one specific design idea.

Its just not going to happen.

BMR is mass producing mild steel mig welded junk subframes for one of the most popular cars in america. They make there money little by little.

There just isnt that market for DSM parts. And if anyone is going to build one, they are going to take the TIME to do it right.

Time = Money.

I don't think it's unrealistic. And I don't think it has to be chromoly, which would require a higher cost. I don't think more than a few DSMers would pay the cost for a chromoly k-member, probably none would pay $1k, but I can't see why a quality piece couldn't be produced for $600-700 in mild steel. And I wouldn't call BMR the holy grail, just a good example of similar parts made for another car - true, a much more popular car. Even UMI, who I've read is widely considered to have better quality versions of the same parts, is priced similar to BMR when it comes to k-members.

I think we can find a fabricator who can do this for a reasonable price that knows what he's doing. True, we won't get the best of the best to do it, but I can't see it being impossible. I've actually got a couple shops asking questions about the project now.

 

[KazooGS-T]

The k-member doesn't have to be chromoly... Look at mustang k-members; I've had a QA1 mild steel k-member on my car for 2 year/15,000 miles and haven't had a single problem, street/strip/highway/terribly shitty Memphis and Jackson roads.

I think many of you are over-complicating this, it can be done for relatively cheap and hold up extremely well. The initial investment is the largest part, I have a buddy local (search for White Rhino Fabrications) that could easily make this project come to life. Once the JIG is made, it's really simple.

The only problem is that there would need to be a guaranteed interest, to make it worth his time. Also, I'm not sure how much of a difference the 2G K has from a 1G, but I will not pull the k-member off my 2G... I have my 1G that I can take by his shop to get work on the project started if enough people show interest.

 

[bostonhatcher]

I don't see a jig happening. It's one of those things where if you want it, just make it yourself.

 

[Sp1kE]

Have you guys actually pulled out and stripped the front K/subframe?
Its light as hell, I could hold it up with 2 fingers.....
If you want more ridgity, just cross stitch the thing, and maybe add an undercar brace from mounting point to mounting point.

Even the lower controll arms are light as could be!

The bad spot is the heavy cast knuckles. If you throw the knuckles on a scale, and then the Subframe with steering rack, I bet the weights would be nearly identical.

IMO there is no reason to get a custom or tube subframe made unless you want to see your pretty steering rack.

 

[Ludachris]

Have you guys actually pulled out and stripped the front K/subframe?
Its light as hell, I could hold it up with 2 fingers.....
If you want more ridgity, just cross stitch the thing, and maybe add an undercar brace from mounting point to mounting point.

Even the lower controll arms are light as could be!

The bad spot is the heavy cast knuckles. If you throw the knuckles on a scale, and then the Subframe with steering rack, I bet the weights would be nearly identical.

IMO there is no reason to get a custom or tube subframe made unless you want to see your pretty steering rack.

We've seen a couple people come through here and post how they've saved 15+ pounds over the stock k-member, but I can't remember all the details. I'd have to look it up. When you factor in the north/south bars that attach to the k-member, I'd bet there's some weight to be saved there. And I'd have to believe a tubular piece would flex less than a braced stock version.

As for the lower control arms, weight savings would just be a bonus. Adjustable heim joints and space for brake ducting is the bigger score. But I would think there would be some weight to be saved, especially since the 2005+ Mustang has a very similar lower arm and the tubular versions of those tend to save weight every time.

Lighter knuckles would be nice though, wouldn't they?

 

[Sp1kE]

We've seen a couple people come through here and post how they've saved 15+ pounds over the stock k-member, but I can't remember all the details. I'd have to look it up. When you factor in the north/south bars that attach to the k-member, I'd bet there's some weight to be saved there. And I'd have to believe a tubular piece would flex less than a braced stock version.

As for the lower control arms, weight savings would just be a bonus. Adjustable heim joints and space for brake ducting is the bigger score. But I would think there would be some weight to be saved, especially since the 2005+ Mustang has a very similar lower arm and the tubular versions of those tend to save weight every time.

Lighter knuckles would be nice though, wouldn't they?

Oh yes they would

15+lbs saved!? Maybe I was feeling jacked that day.....
But I do remember being embarrassed giving it to my buddy to sandblast and telling him that this light a$$ thing is what holds the front end of my car together

If I remember correctly, there is 6 main points where the subframe bolts to the car. 2 studs on the corners, and 1 bolt inbetween on each side.

I think the only way to make it stiffer would be to have something like a strut tower bar, but for the bottom. to make sure the subfame does not flex with the body in the center.

Those north and south bars are super light aswell. But I would love for them to take up less room a nice tubular piece would be great for that


None the less i would still love to see what you guys come up with

 

[SlickGSX]

Sounds interesting. For discussion sake, here's a link to a shop that made one before. Mitsubishi Ecliplse tubular K member

 

[CarTunr22]

I have to agree on the points kawgomoo mentioned. I have a good k-member/subframe sitting on my shop floor waiting for me to put on a jig plate so i can match all of the pickup points. After thinking about it for a while i just don't think what i will produce will be affordabe enough that people will be interested. Im going to make mine with some geometry changes and this will require bespoke a arms and some other custom parts that will bring the price up even more. I guess i just don't see the point of building a tubular k-member/subframe and not addressing some of the other issues in the front suspension/layout. Its going to be a large upfront cost but for what i will be doing it will remove alot of headaches and possible cost in the future.

 

[GDNF2ET]

Sounds interesting. For discussion sake, here's a link to a shop that made one before. Mitsubishi Ecliplse tubular K member

Great Link His work on the EVO is impressive..Lota weight and space being saved there..
Mitsubishi Lancer Evo race car