BMR A-Arm warning

[sigintel]

There is a huge modulus gradient there. Highest stresses are carried on the extreme surfaces and you have a discontinuous surface there inboard that goes from forged tubing to forged tubing weld HAZ to cut plate. There should be cyclical majority compression there under braking. You are lucky you were not in a spin traveling backwards under full braking where the spindle/wheel could have been pushed under the car as the spin came around.

No big deal, but I would suspect this could be made easier to manufacture consistently by designing a single plate to join three tubes where the tube perimeter surfaces have no welds on outside edges. everything preheated in the jig and welds started mid length each tube and run outboard towards end of tube.

Alternatively, two mandrelled tubes and then a taco gusset plate to form the third tube inboard.

Either way, maybe consider no extremity loaded surface with a weld zone in cyclical loading?

 

[Swine]

 

[Mad Hatter]

Hi everyone.... Just wanted to share the email I got back from BMR.... Very happy with the prompt detailed reply.

Hi Matthew,

Thank you for the information. The reason I wanted to chat is because there are more layers than what meets the eyes in these scenarios.

The very first thing I notice is that they are indeed polyurethane bushing arms. While, I am sure there are many people who have chosen to use these in competition, or on cars with wider front wheels and race compound tires, that arm was not designed and tested for that kind of abuse.

The issue when using that specific design is that there is deflection within the poly, but there is zero to minimal deflection on the rear Delrin side. So now under hard/heavy braking you are pulling back on the arm and the front bushing allows it, but the rear does not. While this is great for streetcars, when repeatedly abused like this on racecars and track cars it does introduce higher than normal fatigue loads into the FLCA.

If you have a bearing on the front mount, you are now adding the strength to the entire arm and distributing the loads throughout the entire arm, instead of focusing on ripping the middle in half.

It also appears that those are the extended height ball joints? If so, that is just an additional factor that adds stress to an already poor design (poly front bushing) for handling applications on a tubular FLCA that was not necessarily designed for road course / R compound / 200tw tires etc.

So of all of this said, first and foremost is that if you continue to use a BMR FLCA you really need to consider the AA022 arms with a bearing front pivot and a standard height ball joint.

Now we need to figure out what to do to get you taken care of.

Outside of that, we need to go over the rest of the parts. Do you have a K-Member from BMR? If so, have you added the rear cross brace to ensure the legs of the kmember do not fatigue / bend / break? Our specific item for this would be the AAS001 “A-Arm Support Brace” – this is 100% mandatory for street cars with stock/wider wheels (non drag cars) and of course, cars that are tracked. If you do not have one, that would be another factor that did not help the arm ripping itself apart. The rear legs on the kmember deflecting also introduces more fatigue loads into the FLCAs.

For that brace, we suggest our BMR AAS001….but the Steeda or any other quality brace from a quality company will work just fine.

Can you provide me with order information? Was this placed directly with BMR? A dealer? Was it shipped directly to you, or to a forwarder?

The above is not pointing a finger, I am simply trying to express the cause for a failure of this nature on that specific item. We will work with you to ensure you get repaired and back up and running.

I look forward to your reply,

Thanks

Kelly Aiken

 

[Mad Hatter]

I Just paid the difference now and BMR is sending me a set of new one with spherical bearings (mine were poly). BMR behaved really well!! Impressed.

 

[Nvrfinished]

Kelly at BMR is a good guy. He definitely knows his stuff and is very interested in helping customers solve problems. I've called him a few times to discuss issues (with my car - not parts) that he has helped me out with.

 

[ChrisM]

It would be nice if they put information like that on their website. Here's part of the description for the arms. It's identical for both the poly and spherical bearings:

"Designed for street performance, drag race, and handling, and pro-touring applications, BMR lower A-arms are engineered to give you improved geometry and increased lateral grip during cornering situations."

Doesn't differentiate between track or non-track situations and is kind of misleading. I understand there are nuances between things like "track," "road course," "handling," etc, but the regular customer may not pick up on it.

Same with the K-member brace requirements:

"Designed for street performance, drag race, and handling applications..."

No mention of "Outside of that, we need to go over the rest of the parts. Do you have a K-Member from BMR? If so, have you added the rear cross brace to ensure the legs of the kmember do not fatigue / bend / break? Our specific item for this would be the AAS001 “A-Arm Support Brace” – this is 100% mandatory for street cars with stock/wider wheels (non drag cars) and of course, cars that are tracked."

It is "highly recommended" to run the brace per the website, but not "mandatory" if you are running the k-member with the a-arms.

I like BMR. This is merely a suggestion if any of them are reading this. May want to clean up your site a bit because it seems to contradict the statement Mad Hatter posted above. If you don't want to amend the item descriptions, maybe put up a "tutorial" explaining what parts should be paired with what depending on the application.

 

[Mad Hatter]

Just a note... I did ask Kelly about posting before posting his comments. But It would be great if BMR posted thus kind of detail some where on the BMR website..

Kelly was all for being transparent and getting info out to the people who use the products.

Sent from my SM-G900M using Tapatalk

 

[ChrisM]

Just a note... I did ask Kelly about posting before posting his comments. But It would be great if BMR posted thus kind of detail some where on the BMR website..

Kelly was all for being transparent and getting info out to the people who use the products.

Sent from my SM-G900M using Tapatalk

Yeah, Kelly is awesome like that. I was more concerned about the legal differences between things like "highly recommended" and "mandatory." I'd hate for some litigious customer (the kind who would sue a track for not telling them about a hazard, for example) to have an issue with a BMR product and use that against them now that it's a public statement from a company rep.

 

[bpracer]

ChrisM - I did the same thing you did, went and looked at their site for descriptions for use.

" Designed for street performance, drag race, and handling, and pro-touring applications, BMR lower A-arms are engineered to give you improved geometry and increased lateral grip during cornering situations".

Doesn't really say "road course/track racing" only "handling".

 

[TMSBOSS]

The pictures said all I needed to know.
Let’s hope no one dies while trying to figure out what BMR is saying or avoiding to say.

 

[Mad Hatter]

I am busy making my OEM parts more race worthy in any case. They look like they will bend before they break! . But still, I did like Kellys reply, nice to see a direct and too the point answer these days. Will keep the new spherical ones in the box as spares.

 

[BMRTech]

I have put in a request to add or change information in our advertising material. If I could wear that hat at BMR, I would have already done so.

I've learned over the past 15 years that no matter how you slice it, there will always be people who will be able to bring out errors in wording. There is a fine line between properly informing the consumer and scaring a consumer away from your products. The fact of the matter is that BMR caters to the masses, "street performance", which is precisely what a polyurethane bushed suspension component is used to target.

My phone line is always open for those who want to call and discuss their needs, whether it's a street car or a 100% racecar. Drag or Handling oriented, when a customer tells me they're tracking their car I immediately point them towards a part that is indeed designed with that use in mind (or often simply tell them to put that money elsewhere) In this case, I do not recall speaking with the OP, but I do agree that there should be writing within the descriptions that clarify which part is best for the chosen use and application. I've experienced situations where we have done just that, and the consumers then find a way to pick it apart though - so sometimes you cannot win. "Well I didn't see that note because it was at the bottom of the page" OR "Well I didn't see that warning, because XYZ didn't have that on their website"

My honest and best recommendation is for people who track their cars to contact the company and ask them what is best for their goals and applications, when possible.

I am busy making my OEM parts more race worthy in any case. They look like they will bend before they break! . But still, I did like Kellys reply, nice to see a direct and too the point answer these days. Will keep the new spherical ones in the box as spares.

I believe your new arms have already been delivered. If you have any other questions or concerns you know my email address. Additionally, I have assisted with development on some stock FLCA upgrades that are about to be released from A3 Fabrications that feature a front spherical bearing and rear aluminum saddle with a delrin bushing. If you would like I can shoot over the information to those via email. Shoot me a reply when you get a moment to confirm delivery of the warrantied pieces. Thanks.

 

[Mad Hatter]

Thanks, I can confirm that they arrived in Miami. I will have them down here in Chile in two to three weeks. Delighted to see a active response buy a supplier and hope you manage to update the website with more accurate info.

If you can send any info on the new FLCA's that would be much appreciated. I have several friends running on the current ones and would like to keep them up to date.

 

[Grant 302]

Here are some pics of the failed A-arm.

A poly front bushing didn't 'cause' this. Neither did the rear delrin bushing.

Fatigue from street use can be much worse that track use...an example being potholes and road imperfections.

Use your heads guys.

.

 

[Mad Hatter]

For track/street work I will be using my original A-arm with sphericals. Its just that much more robust... I really cant see them breaking under the conditions as the my last BMR one did. But do appreciate that BMR stands behind their product and gave me a new set when it was beyond warranty etc. I actually originally bought the poly bushing unit thinking about the bad roads down here and the less then perfect tracks...

 

[Grant 302]

I figured that when you said you'd keep the replacement as a spare. Smart move.

My last comment is for anybody else...Because I feel this way:

The pictures said all I needed to know.
Let’s hope no one dies while trying to figure out what BMR is saying or avoiding to say.

Frankly, I am not surprised at all about the location of the failure.

 

[Steelhorse]

An advanced welding class and a good materials engineering book will tell you why that arm failed.

 

[Mad Hatter]

Here is a quick video of the new OEM a-arm with the sphericals......

https://www.facebook.com/video.php?v=10213999804047921

 

[Norm Peterson]

A poly front bushing didn't 'cause' this. Neither did the rear delrin bushing.

Agreed - there's stress intensification going on at pretty much the same location along both sides of the tube. Though those bushing factors probably aren't helping any.

Fatigue from street use can be much worse that track use...an example being potholes and road imperfections.

True, but street speeds are at least much lower when such things are encountered.

Use your heads guys.

This is probably the hardest part, at least if you aren't/weren't an engineer or without having worked closely enough with others who race or track their cars at a serious level. When you don't even know what you don't know, it may not cross your mind that the part you're reading the advertising for just might not be right for your intended use. Here, I'd take early mention of drag racing in the list being a warning as much as because it's probably going to be lighter and desirable for that reason alone. For "handling", the way I see it, the mass market buyer defines handling in terms of street-driving levels of cornering up to "moderately enthusiastic". Maybe 7/10ths. Maybe.


Norm

 

[Grant 302]

Bump. Because this shouldn’t be forgotten. It just might save someone in the future.
I’m kicking myself a bit for not stickying this when I was a moderator. Especially after Duane has a same/similar failure.