BMR K-Member and A-Arms on Road Courses?

[Boone]

I looked into the BMR A-arms and K-member for my car at one time, and here is what I concluded:

K-Member is not as stiff as the stock or Maximum Motorsports model. My final opinion is the lower weight will likely be a wash from a handling perspective (the lower inertial forces and rearward COG counteract the loss in structural rigidity), and a small gain in power / weight ratio.

A-Arms had an early design that would break at a gusset where the BMR logo was located. Once the gusset broke, the tubes would be overstressed causing failure. This issue was addressed by BMR, and I don't know of any of the 2nd generation arms failing.

I am in the same boat with my '05 GT the OP is in. I want a comfortable street car with all the creature comforts afforded that can run with the big boys on track. People are as jealous of me sitting on grid with my AC on as I am jealous of them for beating my lap time by 2 seconds.

Weight loss is hard to come by if you're not willing to go all in. I recommend buying the best wheels and tires you can afford because no single component has a larger influence on your car's ability to turn. Mustangs are quick enough on the straights to hang with most corner carvers.

If this isn't enough, commit to the pure track car, or go buy a Vette.

 

[Norm Peterson]

DOM tubing is not heat treated to begin with, which makes it ideal for welding. Typ 75-87 ksi yield strength..which doesn't change when welded.

A HAZ still exists even in mild steel, just without the formation of hard microstructures.

https://www.ukessays.com/essays/engineering/the-arc-welding-of-mild-steel.php

I'm kind of curious about steel with ~80 ksi yield not having any heat treatment. I remember HY-80 as being low carbon content (not sure about carbon equivalent) with that kind of strength, but it was quenched & tempered.

Norm

 

[Boone]

Norm,

First, I'm an engineer in the overhead crane business, so mild steel and welding is what we do.

Your yield strength is in the correct ball park for DOM tubing, and you are correct the steel used has a low carbon content (but I'm sure you knew that). The heat affected zones to which you are referring are occurring at 180 degree angles to each other on the A-arms. The welding HAZ from a micro structure perspective is not as critical in this application due to the location of the gussets. I would be more concerned if the design incorporated welding of gussets across a structural member that was in tension. The HAZ has a greater tendency to crack when subjected to tension than I have noted in welds in compression or shear.

I haven't seen any mention of whether the BMR A-arm is stress relieved after fabrication. Stress relief is more critical in high carbon content applications, but it would go a long way to eliminate any worries I would have concerning fatigue failure of the weldment.

 

[kerrynzl]

If this isn't enough, commit to the pure track car, or go buy a Vette.

As a Corvette owner and an Ex-Corvette racer my advice is "don't buy a Vette"

Also I'd like to thank you for the intelligent answers here [especially directed towards the subject of metallurgy]

My father was an old timer racer and reasonably competent engineer that always boasted that his welds were much stronger than the base material.[typical "cow shed engineering" mentality]

So I Brinell tested his work once to show him what was happening.



All fabricated or modified suspension components should be correctly heat treated.

 

[fourdegrees11]

I looked into the BMR A-arms and K-member for my car at one time, and here is what I concluded:

K-Member is not as stiff as the stock or Maximum Motorsports model. My final opinion is the lower weight will likely be a wash from a handling perspective (the lower inertial forces and rearward COG counteract the loss in structural rigidity), and a small gain in power / weight ratio.

A-Arms had an early design that would break at a gusset where the BMR logo was located. Once the gusset broke, the tubes would be overstressed causing failure. This issue was addressed by BMR, and I don't know of any of the 2nd generation arms failing.

I am in the same boat with my '05 GT the OP is in. I want a comfortable street car with all the creature comforts afforded that can run with the big boys on track. People are as jealous of me sitting on grid with my AC on as I am jealous of them for beating my lap time by 2 seconds.

Weight loss is hard to come by if you're not willing to go all in. I recommend buying the best wheels and tires you can afford because no single component has a larger influence on your car's ability to turn. Mustangs are quick enough on the straights to hang with most corner carvers.

If this isn't enough, commit to the pure track car, or go buy a Vette.

Any thoughts on the UPR K-member? They make some pretty serious claims in their product description

http://www.uprproducts.com/2011-mustang-suspension-k-members.html

 

[Boone]

My thoughts on UPR...

They are a copycat company that may make the world's greatest K-member (or any other product)... but I'll never know because I won't buy their stuff. I prefer to stick with companies that develop, test, support, and ultimately improve their product. Some drag racers appreciate their lightweight components, but I don't have faith from a road course perspective.

That is my opinion, and I know opinions are like assholes...

 

[Pentalab]

My thoughts on UPR...

They are a copycat company that may make the world's greatest K-member (or any other product)... but I'll never know because I won't buy their stuff. I prefer to stick with companies that develop, test, support, and ultimately improve their product. Some drag racers appreciate their lightweight components, but I don't have faith from a road course perspective.

That is my opinion, and I know opinions are like assholes...

I saw pix of both the UPR + BMR K member, and toggled between em several times. The UPR is a 100% copy of the BMR. But BMR makes 3 x versions, depending on application. The $650.00 UPR K member is made from 4130 chromolly steel and weighs just 18 lbs. The $519.00 BMR K weighs 26 lbs..and is made from DOM tubing.

I see similar weight savings (and price differences) with roll cages made from 4130 CM vs DOM...and that all assumes the welds are done right etc.

I have the BMR A arm brace on my 2010 oem A arms. It weighs very little..and actually ties the A arms together. ( Steeda's chromolly version is the G trac brace.) Fords oem "A arm brace", (right below the firewall) actually just ties the back end of the oem K frame together.

 

[BMR Tech]

Figured I would chime in.

The last issue that I have been made aware of with our tubular FLCA was when Steve Poe broke one. He had been running our Gen1 design for a while and developed some cracks, so I told him we would make some changes to a set and send them his way. Well, one of those failed not too long after he started using them. The additional gusseting that we added was not performed properly, and the crack developed and that was all she wrote.

Shortly after that happened in 2012, we went ahead and revised our design which included going to .120" wall tubing, and revised the gussets with 40% thicker plate and no logos or cutouts. We also extended the rear portion to reinforce past the billet rear bushing stud and puddle-weld.

We have not seen an issue with the Gen2 design. Now, I have seen them fail under extreme impact situations, but I have not seen a failure due to the design.

As for our tubular K-Member. When the AAS001 is used, I have only seen one issue ever with our S197 tubular K-Member. This was on a very heavy 4,000~lb Roush road course car out of Oklahoma. They had some issues ripping the welds on the rear A-Arm mounts. They repaired them as they were not severe, and I never heard back from them other than the occasional "hey this stuff is still working for us".

*The only other issues I have seen with customers using our K-Members are the rear mounts caving in the floorpans. That area of the stock chassis is not very strong, so this is something that I think is more common than most know.

Our K-Member saves 22lbs over the OE K-Member.

Our A-Arms these days after revising, are only good for about 7-8lbs savings. (They used to save well over 10)

We are the first to admit our flaws. We also recognize that the OE design of the FLCA on the S197 is a very tough design to make strong, especially when trying to save weight. We have seen about every design (stock style replacement) from the aftermarket fail.

I recently did some digging on the OE FLCAs...and I came to the conclusion that once you upgraded them with the available bushing replacement options, etc....the savings compared to the BMR Tubular design is almost non-existent.

Anyone who has called us to discuss this topic will tell you that I am a straight shooter. I am not a "salesman" and I usually always try to lead people in the direction that I would take. In this specific scenario, I am not really a big promoter of tubular FLCA on dedicated track cars. We have thousands and thousands of them out on roads as I type this, but for the racers I tend to suggest putting that money into other areas.

To close, am I confident in our FLCA and K-Members? Absolutely. Do I suggest them to everyone who wants to save weight and race? Nope. Do I try to convince people not to use them? This depends on what the specific situation is and what the end user's goals are. For example, I have a racer (Pratt Cole) who just wants the parts. When I try to suggest things, or mention potential issues etc. I get "It's racing". Pratt uses our front end parts on a few cars and him and his crew really likes the parts.

Lastly, keep an eye out for some new stuff coming.

 

[SoundGuyDave]

Very well said, Kelly, and I applaud your honesty and candor.

 

[BMR Tech]

Thanks Dave.

Here is a Gen2 A-Arm with a ton of abuse that we have in for analysis. In the meantime, what we are doing is, we will be updating our "adjustable" front bearing arms (like pictured) with some larger additional gusseting (the white paper), simply because more and more people have been using our FLCAs on track / racecars.

I will call this Gen2.5. I am pretty sure Gen3 will be the all new FLCA which is boxed and strong as an ox - and we may even make a cool new brace to "add-on" to our front K-Member for a full set-up for the hardcore track guys.

 

[Boone]

I prefer to stick with companies that develop, test, support, and ultimately improve their product.

Kelly's response is exactly what I'm talking about. Let's see if a UPR rep chimes in to defend their position.

 

[BMR Tech]

The issue we face with the S197 FLCA design is the lack of triangulation.

For example, we can make VERY VERY strong arms. However, those very very strong arms will not clear most 9" or wider wheels. Counterproductive, unfortunately.

Check this out. Strong as an ox, yet would need 8" wide wheels. lol

 

[BMR Tech]

Then you have even stronger. Something like this would be the absolute 100% best FLCA on earth for the S197.

Would people pay $1000 for them? Likely not.

 

[slackinoff]

As a Corvette owner and an Ex-Corvette racer my advice is "don't buy a Vette"
.

Sorry for getting off topic. But in regards to your FR500C, someone said why they were so much lighter than the a regular gutted GT......I did some research on your FR500C....wow, that engine is pretty special. I would love to see some pictures. The FR500S had pretty much a regular 4.6 in it, the C? That is a wild engine.

 

[kerrynzl]

Sorry for getting off topic. But in regards to your FR500C, someone said why they were so much lighter than the a regular gutted GT......I did some research on your FR500C....wow, that engine is pretty special. I would love to see some pictures. The FR500S had pretty much a regular 4.6 in it, the C? That is a wild engine.

Here's a couple of more pics of the car, including the engine bay. The engine still has a "Ford Racing" seal on it.

Please excuse all the gold wrap heat reflector on the intake. I won't remove it because it helps identify the cars history.

I found this "for sale" listing from 2011 which shows the same engine bay.
Bits of flouro paint are evident on my car.
http://www.modularfords.com/threads/179285-For-Sale-54-GRAND-AM-Mustang-FR500C

My car now has the original livery from when "Blackforest Motorsport" campaigned it.

All I need is a few misc pieces to finish car [grille, upper radiator plastic, Ac vent]

 

[Gab]

If I wanted to build a cheap dedicated S197 racecar, I would start looking for a V8 manual candidate with a nice paint job. [a repaint will cost more than the value of the car]

Then go insane on gutting the car, [I mean everything possible].
I would use stock brakes with race pads and keep the ABS.
Keep the motor stock except exhaust [weight saving] Intake filter, and add an oil accumulator.
Add 4.10 rear gears.
For suspension all I would do is play with spring rates and allignment.
And the biggest expense would be wheels and tyres.
and a simple 6 point cage + 1 race seat and harness.

The majority of the work and gains would be from stripping out the car.

I've seen some pretty good racecars built on the same method [usually in production categories]

If you threw $200K at your car, you only end up racing against others that also spent the same amount on theirs.

Having Fun and driving on the absolute limit of tyre adhesion is what it's all about.

Absolutely SPOT ON. In my experience, people tend to spend lots of money on parts with the expectation that they'll somehow be instantly faster. Rather, a simple combination of parts designed to work together, along with seat time usually does the trick.

 

[Mustang dog]

Figured I would chime in.

The last issue that I have been made aware of with our tubular FLCA was when Steve Poe broke one. He had been running our Gen1 design for a while and developed some cracks, so I told him we would make some changes to a set and send them his way. Well, one of those failed not too long after he started using them. The additional gusseting that we added was not performed properly, and the crack developed and that was all she wrote.

Shortly after that happened in 2012, we went ahead and revised our design which included going to .120" wall tubing, and revised the gussets with 40% thicker plate and no logos or cutouts. We also extended the rear portion to reinforce past the billet rear bushing stud and puddle-weld.

We have not seen an issue with the Gen2 design. Now, I have seen them fail under extreme impact situations, but I have not seen a failure due to the design.

As for our tubular K-Member. When the AAS001 is used, I have only seen one issue ever with our S197 tubular K-Member. This was on a very heavy 4,000~lb Roush road course car out of Oklahoma. They had some issues ripping the welds on the rear A-Arm mounts. They repaired them as they were not severe, and I never heard back from them other than the occasional "hey this stuff is still working for us".

*The only other issues I have seen with customers using our K-Members are the rear mounts caving in the floorpans. That area of the stock chassis is not very strong, so this is something that I think is more common than most know.

Our K-Member saves 22lbs over the OE K-Member.

Our A-Arms these days after revising, are only good for about 7-8lbs savings. (They used to save well over 10)

We are the first to admit our flaws. We also recognize that the OE design of the FLCA on the S197 is a very tough design to make strong, especially when trying to save weight. We have seen about every design (stock style replacement) from the aftermarket fail.

I recently did some digging on the OE FLCAs...and I came to the conclusion that once you upgraded them with the available bushing replacement options, etc....the savings compared to the BMR Tubular design is almost non-existent.

Anyone who has called us to discuss this topic will tell you that I am a straight shooter. I am not a "salesman" and I usually always try to lead people in the direction that I would take. In this specific scenario, I am not really a big promoter of tubular FLCA on dedicated track cars. We have thousands and thousands of them out on roads as I type this, but for the racers I tend to suggest putting that money into other areas.

To close, am I confident in our FLCA and K-Members? Absolutely. Do I suggest them to everyone who wants to save weight and race? Nope. Do I try to convince people not to use them? This depends on what the specific situation is and what the end user's goals are. For example, I have a racer (Pratt Cole) who just wants the parts. When I try to suggest things, or mention potential issues etc. I get "It's racing". Pratt uses our front end parts on a few cars and him and his crew really likes the parts.

Lastly, keep an eye out for some new stuff coming.

And, this is why I continue to support BMR, and yes I have their K member installed with rad support etc. Not because it was lighter but to me it was one of the best options out there over stock. Yes , it makes working on the car a lot easier as well.

 

[kerrynzl]

Absolutely SPOT ON. In my experience, people tend to spend lots of money on parts with the expectation that they'll somehow be instantly faster. Rather, a simple combination of parts designed to work together, along with seat time usually does the trick.

My comments were based on the 90/10 rule [where you spend 90% of your $$$ on the last 10% of gains]

Most club racers [myself included] do it for enjoyment, so we should treat our racing like a "Gearheads" version of playing golf on the weekend.

 

[GT Premi]

I have the BMR K-member and A-arms on my GT500. I love them. I've been running them since, I believe, 2013 or '14. The only complaint I have with it is that the stock belly pans don't fit it.

Someone asked if a Watts link is worth installing for road racing. I say a Watts link is worth installing, period! I went from the stock panhard to BMR's adjustable panhard bar and brace. It was a world of difference, and I thought it was the cream of the crop. I now have their Watts link (with upgraded pivot), and I wish I had gone straight to that solution in the first place. When it comes to keeping the rear axle in check, a panhard bar and a Watts link aren't even comparable. It's that drastic of a difference, and that's taking into account how great I thought the panhard bar was.

I'm thinking about starting a thread with some suspension questions of my own. My GT500's suspension is 100% aftermarket (mostly BMR stuff), and I have an area or two I need to dial in with regards to steering feel and response.

 

[Gray Ghost GT]

I decided to stick with the OEM K-member and A-arms on my GT until an equally strong, but lighter aftermarket version arrives; preferably from BMR that I use on my suspension. Turning my attention to lighter wheels (CCW or Forgeline) and 305 tire square setup (same overall weight to my current OEM GT500 wheels with 275 square). I accept the weight.... it is what it is. After driving a heavily prepped Corvette C5 for 10 years that weighed 500 lbs. less (I got a little spoiled). Having an awesome time with my prepped GT!! Consistently turning 1:25 on the Summit Point Main circuit and achieved a personal best last Sunday at 1:24.7. Who knew it would be so much fun passing Porsches and Corvettes? lol