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

Gray Ghost GT

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I'm looking for ways to drop significant weight off the front end of a 2009 Mustang GT that does a lot of HPDE road course events, which translates to high-G turns and other stresses while driving in a performance environment for 25 minute sessions. My concern is strength of these lighter weight products. Is anyone using these two BMR parts on their road course cars? I appreciate your feedback. Mike

KM020_image2_small.jpg


AA010_small.jpg


http://bmrsuspension.com/?page=products&productid=1102&superpro=0

http://bmrsuspension.com/?page=products&productid=123&superpro=0
 

ddd4114

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I'm not necessarily trying to dissuade you, but what are you trying to accomplish by reducing front weight? Are you trying to mitigate a problem you're experiencing or simply trying to improve overall performance? Are you having understeer problems that might be easier fixed with different springs/bars or a splitter to balance out the wing pictured in your signature?

To answer your question, I don't have any personal experience with those parts and don't know how well they work for track rats. In general, it's kind of risky to replace parts like that unless you have a real need for them. If an aftermarket A-arm or subframe does fail on track, you could be in for a hell of a ride.
 

kerrynzl

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You'd probably get more weight savings by pulling the guts out of the front bumper.

Weigh their components and compare them to Ford, you'd be surprised.
Especially the lower arms. Weigh the ball joint end while the inner pivots are sitting on V blocks [to get unsprung weight, and compare this to Ford]

All the Mustangs that ran in the SCCA Grand-Am series [GS] used Ford Components plus an inverted strut
 
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noldevin

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Most of the road course guys say this isn't sturdy enough. They aren't designed with the lateral forces of road course use in mind.
 

SoundGuyDave

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Are you looking for a net weight reduction, or shifting the corner-weights and bias rearward? In terms of net, there's really not a lot you can do up front that doesn't get into stupid levels of cost and complexity (tube-frame conversion), but you can make some inroads into shifting the bias rearward. Battery relocation, computer relocation, ABS block relocation, delete EVERYTHING that you don't absolutely need, carbon pin-on hood, carbon fenders, etc. The LAST place I would look to save weight (particularly at the possible expense of structural rigidity) would be down low, like the K-member or the control arms. All that other stuff is up pretty high, which will affect your polar moment.
 

Gray Ghost GT

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Thanks everyone. I appreciate your feedback. The Mustang handles great on the road courses - just need to place it on a serious diet since it weighs in at 3,700 lbs. I'm looking for a net weight reduction while shifting the corner-weights and bias rearward. I relocated the battery to the trunk and added a lighter hood. I agree regarding the K-member or the control arms - don't want to sacrifice strength for lighter weight. The AC delete only gets me 30 lbs. Sounds like there aren't many weight loss options for a car that you also want to drive on the street. Been talking to some CMC, AI and other Mustang race car owners for ideas, but it gets expensive and extreme for what I'm looking for. Best to save my money for other consumables and etc.
 

ddd4114

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If you're just doing non-competitive HPDE events, then I wouldn't worry about it too much. Unless you're willing to invest a significant amount of time and money, you won't be able to reduce weight significantly enough to have a substantial effect on consumable wear or performance; you would only notice small improvements.

Aside from the easy stuff (removing interior trim, spare tire, etc.), I've only focused on reducing components that I already had to replace: the wheels, seats, driveshaft, and clutch/flywheel. For a dedicated track car, the battery would be on this list too. In my opinion, most other things aren't really worth going out of your way to replace or remove unless you're competing and need an edge. Even if you are competing, you'll probably have a minimum weight or power/weight that will prevent you from doing anything too crazy. I have a competition weight (including driver) of ~3750 lb in NASA TT, and I can *mostly* keep up with well-prepped cars that weigh 700+ lb less than me. The biggest drawback of weighing that much is consumable cost, not necessarily performance. Endurance racing is also a completely different story, but it doesn't sound like that's a concern for you.

Is there any specific goal you're trying to achieve with the weight reduction/relocation?
 

kerrynzl

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Thanks everyone. I appreciate your feedback. The Mustang handles great on the road courses - just need to place it on a serious diet since it weighs in at 3,700 lbs. I'm looking for a net weight reduction while shifting the corner-weights and bias rearward. I relocated the battery to the trunk and added a lighter hood. I agree regarding the K-member or the control arms - don't want to sacrifice strength for lighter weight. The AC delete only gets me 30 lbs. Sounds like there aren't many weight loss options for a car that you also want to drive on the street. Been talking to some CMC, AI and other Mustang race car owners for ideas, but it gets expensive and extreme for what I'm looking for. Best to save my money for other consumables and etc.

Weight removal is the fastest way to get gains.
It is all about power to weight: Engine power to weight, Braking power to weight, Cornering power to weight. [so removing weight gets gains in all 3 areas]
Now you need to know about the laws of dimishing results [eg: spending $12K on "gun drilled" titanium bolts to save 5lbs ]
Removing shit that doesn't need to be there is the cheapest approach, before you buy lightweght parts.

But if you're really serious it is cheaper to buy a 2nd car dedicated for the track, than to depreciate a nice road going car.

My Mustang only weighs 3000lbs with a cage. [it is gutted out]
 

SoundGuyDave

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Weight removal is the fastest way to get gains.
It is all about power to weight: Engine power to weight, Braking power to weight, Cornering power to weight. [so removing weight gets gains in all 3 areas]
Now you need to know about the laws of dimishing results [eg: spending $12K on "gun drilled" titanium bolts to save 5lbs ]
Removing shit that doesn't need to be there is the cheapest approach, before you buy lightweght parts.

But if you're really serious it is cheaper to buy a 2nd car dedicated for the track, than to depreciate a nice road going car.

My Mustang only weighs 3000lbs with a cage. [it is gutted out]

+1 to everything Kerry said, PARTICULARLY about a dedicated track car. It sounds like you've got the bug, and trust me, it'll be cheaper in the long run to either buy a new daily-driver, or to put yours back to stock-ish and get a proper track car.

Compromise builds are never going to be as fast as a true race car, or as comfortable and useful as a true street car.

Sidebar: 3000lbs for an S197????? That's holy-grail territory! What the hell did you do to get it down that far? I'm sitting at 3300 with driver and fumes (overbuilt cage, some "enduro" goodies hurts the bottom line somewhat), and I'd love to know where you found the extra 300lbs!
 

kerrynzl

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SoundGuyDave;2397598 Sidebar: 3000lbs for an S197????? That's holy-grail territory! What the hell did you do to get it down that far? I'm sitting at 3300 with driver and fumes (overbuilt cage said:
I did it the easy way! I bought one of those special "Canadian Liightweight Specials".

My car is one of the original FR500C's that was campaigned by Blackforest Motorsport in the Inaugural season for Ford. [Ford used Multimatic and Blackforest as the factory teams]
It is an extremely rare car outside of the USA.
[attached is photos of the car at my home]

Replicating this car would be cost prohibitive, and they're starting to creep up in value [in 2-1/2years time it will qualify for Historic racing with an FIA Logbook]

Sorry to side track this thread.
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.
 

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Chriss_302

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Save your money and spend it elsewhere, weight reduction is the best place to start.
I'm currently prepping my car for ST2 and aiming for 3300-3400 lbs.

FRPP tubular front beam
HVAC Delete
Lighter wheels
2 piece rotors

All good places to start.

I run with guys that use parts that are oem on the 302s.
 

SoundGuyDave

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I did it the easy way! I bought one of those special "Canadian Liightweight Specials".

My car is one of the original FR500C's that was campaigned by Blackforest Motorsport in the Inaugural season for Ford. [Ford used Multimatic and Blackforest as the factory teams]
It is an extremely rare car outside of the USA.
[attached is photos of the car at my home]

NICE looking car!

Replicating this car would be cost prohibitive, and they're starting to creep up in value [in 2-1/2years time it will qualify for Historic racing with an FIA Logbook]

Sorry to side track this thread.
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.

Agreed, 100%. I would also add that the BEST route, at least up this way, would be to start with a high-mile GT, and basically strip the thing down to a bare chassis.

1) Sell the engine and trans, replace with a 5.0 crate motor and controls pack, and a T-56 with good ratios, like a MagnumXL, BossR1, or a Rockland Standard close-ratio box and an aluminum 1-piece shaft. Cat-less exhaust with long-tubes will save a BUNCH of weight. Aluminum flywheel and basic clutch, too.

2) Ditch all the stock electrical junk, and just wire it up old-school. Brake lights and the controls pack stuff is really all you need for a track rat. More involved if you want to build a night-capable enduro car, but for a typical sprint race or HPDE car, that's all fluff. Seriously, the electrical system weighs around 50lbs! (PDB, RCM, SJB, etc, plus a TON of wire).

3) Refresh the suspension: Best dampers you can afford, replace all the bushings up front with delrin/aluminum; all rod-ends out back, including the PHB. Watts weighs. Hydraulic or electric rack is up to you, depending on which donor you have.

4) Early GT500 brakes. With the "new and improved" weight, you won't need the 12-piston carbon-ceramic cross-drilled bling brakes that also cost a fortune. Stock rear calipers. GT500 HCU and Boss302 ABS module, wire in the wheel speed sensors and the two power leads, done. Bonus points if you relocate the block away from the nose.

5) Strip EVERYTHING out of the interior, including the seam sealer, weld-in a nice cage, bolt in one good race seat (plus belts and nets), and done.

6) Swap the stock diff for a TruTrack or gear-style diff, and either 3.73 or 4.10 gears (depending on your usual tracks). Diff cooler will be a good thing to have, as well.

This CAN be done for around $30K (USD) plus the cost of the donor, less the sale of the engine and trans. What you're left with is a ZERO-mile drivetrain, and nothing but what is essential to start, stop and turn, and essentially a build that would need to be restricted down to fit into American Iron. Long-term survivability is high, consumable expenses are relatively low (Toyo or Hoosier R-comps), and it'll be a hoot to drive, and should scale between 3000 and 3100 without driver.

Obviously not a complete parts list, but you get the idea from the broad strokes. Yes, you can "improve" on this list, but it will drive the cost upwards for "relatively minimal" gain. Skip the accumulator and go to a GT350R oil pan, for a net cost of ~$1000. Automatic V6 donor can save you bucks, but you'll need to replace the rear axle assembly.
 

fourdegrees11

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So is the BMR K-member and A-arm any good?

I think telling someone they should just go ahead and build a straight up race car when they're asking about weight reduction on their street car might be a bit over the top...
 

A John In NJ

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This would obviously go against your whole direction but would a Watts Link be worth getting for hardcore track use?
 

Norm Peterson

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I think telling someone they should just go ahead and build a straight up race car when they're asking about weight reduction on their street car might be a bit over the top...
Replacing the K-member is close enough to being a race car mod to raise questions of overall benefit to cost and "if you're this serious about dropping a few lbs of sprung weight down low in the car perhaps you should consider gradually building up a separate race car instead". Whether that would end up being this one or something else is irrelevant.

For a handling-centered application, the K-member would be worth somewhat less than 20 lbs (don't forget to add back in the weight of the recommended A-arm brace). I don't know what the potential weight savings for the A-arms (L-arms?) themselves might be.

The 75 lb weight loss that you may have seen in the advertising is almost certainly for a dragstrip or serious street/strip build where you get to throw away another 26.5 lbs by swapping the radiator support out and losing the front sta-bar (and its brackets and endlinks).


Norm
 
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Pentalab

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Replacing the K-member is close enough to being a race car mod to raise questions of overall benefit to cost and "if you're this serious about dropping a few lbs of sprung weight down low in the car perhaps you should consider gradually building up a separate race car instead". Whether that would end up being this one or something else is irrelevant.

For a handling-centered application, the K-member would be worth somewhat less than 20 lbs (don't forget to add back in the weight of the recommended A-arm brace). I don't know what the potential weight savings for the A-arms (L-arms?) themselves might be.

The 75 lb weight loss that you may have seen in the advertising is almost certainly for a dragstrip or serious street/strip build where you get to throw away another 26.5 lbs by swapping the radiator support out and losing the front sta-bar (and its brackets and endlinks).


Norm

AutoXracer on the Roush Forum had his BMR A Arm shear right off, just like you cut it in a bandsaw, precision slice. I thought for sure it was the weld, but apparently the slice was a hair on the outboard side of the weld.... like by .01". Gerald had one of the very 1st new BMR A arms + BMR K frames. Dunno if BMR changed the design, or added gusset plates etc. I never did hear what happened after that.... it did get resolved in the end. It was just in DD mode when it sheared, no track time.

The oem pass seat weighs 52 lbs..and the rear seat weighs 40 lbs.... both come out quickly. Add everything in the trunk, like spare tire, jack, tools etc, all of it, and you could easily dump 135+ lbs..without spending a dime. That's all sprung weight of course. A full tank of fuel weighs 100.6 lbs (fuel). You could dump some additional weight via fuel level... like 25-75 lbs.
 
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Norm Peterson

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AutoXracer on the Roush Forum had his BMR A Arm shear right off, just like you cut it in a bandsaw, precision slice. I thought for sure it was the weld, but apparently the slice was a hair on the outboard side of the weld.... like by .01".
That would mean the heat-affected zone was what let go, not the weld filler metal proper.

I'd heard of at least one failure (don't remember whose), and I think I heard of a change as a result. Kelly would have to be the one to verify that.


Norm
 

Pentalab

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That would mean the heat-affected zone was what let go, not the weld filler metal proper.

I'd heard of at least one failure (don't remember whose), and I think I heard of a change as a result. Kelly would have to be the one to verify that.


Norm

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. 4130 Chromolly steel is 70 ksi yield in it's un -heat treated form. The usual deal with 4130 CM steel is to bend it, drill it, weld it etc, then you heat treat it...dead last. Once it's gone through the heat treating process, the yield strength increases to 107-125 ksi. But you can't weld to it after that..or you you lose the benefit of the heat treating process, and yield strength drops like a rock... back to square one. It's also a bitch to drill heat treated CM steel.

I will ask gerald what the final outcome was. Being beyond the weld, thicker walled tubing could be used, or bigger diam tubing, or both. Or a short DOM tubing insert could be inserted into the problem area, increasing the wall thickness just in the problem area. It may have been a welding process issue. To dump 20+ lbs from the oem config is a feat in itself.
 
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