[Guest]

I was wondering if there would be any ill effects If I put on just the lower LCA's from bmr? I am not really concerned with traction but I am sick and tired of people telling me "Dude!! your axle is F&%$ed up man!!" and I just want a cheap fix, and 160 seems like as cheap as you can get.

 

[Guest]

No, it messes up the pinion angle, and you usually need a new driveshaft when moving the axle back.

 

[Guest]

If you goto the extended to get rid of the wheelwell issue, you have to change both lowers and uppers or your pinion angle is WAAAAAY off.

Be aware that the "real world" cost of extendeds is gonna be closer to $1K (yes, you read that right!). This includes :</font>

• New extended lower and ADJUSTABLE extended upper BMR arms (the "fixed length" will NOT be right, trust me on this one!) = $380</font>
• New extended driveshaft = $325 if you have stock gears (and thus can "get away" with the Inland Empire smaller shaft) or $450 if you have non-stock gears (need better vibration resistance of a larger diameter driveshaft). Not changing a driveshaft is just begging for tranny tailshaft bushing issues
  </font>
• Springs : moving it back, with no other changes, will slightly lower the car. This is because the rear spring angle is now off....most folks just ignore this issue though</font>
• 5th brake line : varies from car to car, but on some there isn't enough slack in the stock line to accomodate needing an extra 3/4" of wheelbase. And having 400+ lbs of your rear suspension HANG from this rubber line every time you jack up the car isn't gonna help
  . Figure on a brake line swap = $100 for the 5-line kit from Russell or Earls (upside being your brakes work better afterwards). The word "bitch" has often been used to describe the job of swapping this 5th line while in the car </font>

So, you've gone thru all this crap to move the axle 3/4". Congrats, you now have a car that handles and launches worse than if you had just done the STOCK length BMR lowers only ($160) and been done with it

 

[Guest]

Congrats, you now have a car that handles and launches worse than if you had just done the STOCK length BMR lowers only

C'mon, Ed... tell us how you really feel! lol

 

[Guest]

Not only all that Ed said, but the rear axle isn't "F&%$ed up man!!", it's part of the design history of full size Chevrolets from about '58 on. Go to a car show and look at restored full size Chevies and you'll see that almost all of them have the rear axle set forward in the wheel well. The older ones have more of a "swoop" to the rear part of the opening than our cars, but the design feature is still there. So accept your history and don't F up your suspension.

 

[Guest]

FWIW, YMMV, 30k+ miles on a set of non-adjustable BMR extended arms, stock driveshaft, 2" lowering springs, stock 5th line, no vibrations, no problems.

Car doesn't get drag raced or autocrossed ever - 100% daily driver instead. With the basically stock motor, stock trans, whatever minor decrease in launching and handling abilities isn't of concern/not noticable over stock. Looks a helluva lot better though.

 

[Guest]

I dont think its f-ed but for those who dont know it would sure seem that way. Also when ever I have my car at a show everyone tells me "dude something is wrong with your rear end you might wanna check it out" and that kinda bugs me. I do take my car to the track but only after I have done a few things just to see how much it helped so if its going to wear things out or there is a chance my car will vibrate then I think Im going to stay away from it for know.

 

[Guest]

Originally posted by AutocroSSer:
Be aware that the "real world" cost of extendeds is gonna be closer to $1K (yes, you read that right!). This includes :

• New extended lower and ADJUSTABLE extended upper BMR arms (the "fixed length" will NOT be right, trust me on this one!) = $380
  
• New extended driveshaft = $325 if you have stock gears (and thus can "get away" with the Inland Empire smaller shaft) or $450 if you have non-stock gears (need better vibration resistance of a larger diameter driveshaft). Not changing a driveshaft is just begging for tranny tailshaft bushing issues
  
  
• Springs : moving it back, with no other changes, will slightly lower the car. This is because the rear spring angle is now off....most folks just ignore this issue though
  
• 5th brake line : varies from car to car, but on some there isn't enough slack in the stock line to accomodate needing an extra 3/4" of wheelbase. Figure on a brake line swap = $100 for the 5-line kit from Russell or Earls (upside being your brakes work better afterwards).
  
  So, you've gone thru all this crap to move the axle 3/4". Congrats, you now have a car that handles and launches worse than if you had just done the STOCK length BMR lowers only ($160) and been done with it

• Let's look at this from another angle. I'm not being argumentative; I just want to know.
  
  How many guys have to change the uppers anyway? The bolt holes in mine are beat out of shape, requiring replacement. If I go with extended uppers, it will cost $70 extra.
  
  How many guys install a better driveshaft after gears anyway, due to vibration? The extended is the same price as the regular length. Extra cost $0.
  
  How much does the change in spring geometry lower the rear of the car?
  
  Again, how many guys convert to braided brake lines anyway? Extra cost $0.
  
  Cost: For the many folks that are doing the typical mods, ie gears, control arms, brakes (less common), we may total an extra cost of as little as $70. However, for the people that aren't planning many mods, the extra cost could be as much as $600. I agree that the cost to center the wheels is not worth it, unless it really is too irritating to ignore.
  
  Handling: You now have improved control arms and better swaybars (that couldn't be used on the stock lowers without tearing them up).
  Wouldn't it handle significantly better than stock? Can you quantify how much better it would handle with stock length BMR's vs. extended?
  
  Launch: I agree that every little bit helps here. Can you quantify how much worse the launch would be with the extended control arms? Does anyone have direct experience with this that they would like to share?
  
  Obviously, I'm one of the people that is planning on doing most of the mods anyway. I am considering centering the wheels while I'm at it, and want to know if it really will detract from the handling and launch. More info would be greatly appreciated.

 

[Guest]

I did this mod, both upper and lower RCAs with a new MMX DS. Although I like the look, the uppers were a total PITA!!!! Oh and I love the way my car launches!

 

[Guest]

You guys don't get it....
When someone thinks your axle has a problem...the correct answer is:
"I had the axle moved forward to give me better weight distribution at the track. It helps to launch the car better...you know...just like those NHRA Funny Cars. Take a look at them, there wheels are way forward in the wells for the same reason."
And finish with this....
"I can hook you up with a guy who will move your axle forward....If you want to be cool like John Force and me."

Later,
Bob T.

 

[Guest]

I have the extended BMR fixed uppers and lowers with an extended Dynotech driveshaft. Don't have a long term assessment but it feels better than stock and looks way better IMHO.

I had a local 4X4 shop put them in for me after I read the posts about the difficulties encountered with the uppers.

Robert

 

[Guest]

Hey Ed, you make some good points about the cost of doing x-length arms the right way. If your'e ONLY concerned with the appearance of the wheel location, it is an expensive fix. But grnmean also made a good point that many of us will do those other mods for other reasons.

So my question is how critical is the spring pearch alignment(shocks too for that matter)? How much of an impact does it have on handling? As far as launch, doesn't centering the wheel in the wheelwell allow the use of a larger diameter tire? Wouldn't this negate the slight degradation in geometry and provide better traction at launch?

Any input is appreciated as I plan on doing all these mods.

 

[Guest]

More details :

Moving the arms back (extended arms) does a few things geometry and weight wise....NONE of them good!

</font>

1. Worse weight distribution (more front-biased). Besides hurting handling on a car that is alredy front biased (albeit not as bad as an F-body), it isn't helping your launch either. There's a reason that folks are moving that battery to the TRUNK and not out on the edge of the front bumper </font>
2. Springs/shocks now cocked at more of an angle (cocked spring angle means the spring is no longer straight up and down, but rather sort of "sideways"). Can be solved on the shocks with longer bolts/shims, requires custom spring perches to be installed on the axle.....which presents geometry problems all it's own (your springs aren't really "on top" of the axle now!)</font>
3. Shorter wheelbase = better for handling. Pretty much a universal one there
   </font>

If you look inside the wheelwell (not just outside), you'll see that centering doesn't do jack crap for tire clearance.

 

[Guest]

Originally posted by AutocroSSer:
More details :

Moving the arms back (extended arms) does a few things geometry and weight wise....NONE of them good!

</font>

1. Worse weight distribution (more front-biased). Besides hurting handling on a car that is alredy front biased (albeit not as bad as an F-body), it isn't helping your launch either. There's a reason that folks are moving that battery to the TRUNK and not out on the edge of the front bumper </font>
2. Springs/shocks now cocked at more of an angle (cocked spring angle means the spring is no longer straight up and down, but rather sort of "sideways"). Can be solved on the shocks with longer bolts/shims, requires custom spring perches to be installed on the axle.....which presents geometry problems all it's own (your springs aren't really "on top" of the axle now!)</font>
3. Shorter wheelbase = better for handling. Pretty much a universal one there
   </font>

If you look inside the wheelwell (not just outside), you'll see that centering doesn't do jack crap for tire clearance.

All respect intended BUT there are a few guys in the Top 5 of Class 6 bolt on cars running the extended BMR's and having 60' time others would die for. Granted I run this particular set up and have been chasing a driveline vibe. Still I pull consistent high 1.7xx's and very low 1.80's.
If I were to do it all over again. I would have stayed with the standard length arms (probably different vendor also).
It's actually interesting at the track to watch some SS's launch with stock control arms and you can actually see the tires shaking around due to the crappy stock arms.

As for the topic asks - Probably not a good idea.

 

[Guest]

NeverFollow

what brand of LCA's did you purchase?

 

[Guest]

He has BMR, same as me. Why wouldn't you get the BMRs again? Would you go with Hotchkis instead? Just curious.

Just for clarification. I did this mod because I hated looking at the rear wheels un-centered. I accept the well made arguments that this is the wrong mod from a performance and handling perspective. However, I don't feel that it has negatively impacted my performance to the point that I would not do this again.

 

[Guest]

Originally posted by stumpy:
He has BMR, same as me. Why wouldn't you get the BMRs again? Would you go with Hotchkis instead? Just curious.

Just for clarification. I did this mod because I hated looking at the rear wheels un-centered. I accept the well made arguments that this is the wrong mod from a performance and handling perspective. However, I don't feel that it has negatively impacted my performance to the point that I would not do this again.

I do run the BMR extended control arms. I did have one LCA break in the past and their tech department at BMR sucks. I guess that kinda puts it in a nutshell.

 

[Guest]

Aftermarket extended will improve handling and launch over stock arms, but stock length aftermarket arm are better. That is why you are not dissatisfied with the handling it is still better than stock.

 

[Guest]

Originally posted by NeverFollow:
I do run the BMR extended control arms. I did have one LCA break in the past and their tech department at BMR sucks. I guess that kinda puts it in a nutshell.

I see your point and it makes sense. While my experience with BMR tech support has been positive, it's also possible for someone to screw up and piss off a customer.

The funny thing is, I would probably have stock length RCAs on right now had it not been for the fact that Global West could not return my calls. Plust, every time I called I was told to call back in a few hours or the next day because they were too busy to take my order. Do that for a week and you certainly do piss off a 'potential' customer.

 

[Guest]

Originally posted by AutocroSSer:
[QB] More details :

Moving the arms back (extended arms) does a few things geometry and weight wise....NONE of them good!

</font>

1. Worse weight distribution (more front-biased). Besides hurting handling on a car that is alredy front biased (albeit not as bad as an F-body), it isn't helping your launch either. There's a reason that folks are moving that battery to the TRUNK and not out on the edge of the front bumper </font>
2. Springs/shocks now cocked at more of an angle (cocked spring angle means the spring is no longer straight up and down, but rather sort of "sideways"). Can be solved on the shocks with longer bolts/shims, requires custom spring perches to be installed on the axle.....which presents geometry problems all it's own (your springs aren't really "on top" of the axle now!)</font>
3. Shorter wheelbase = better for handling. Pretty much a universal one there
   </font>

All these general statements are true. But let's take a look at the actual impact, on a mathematical basis. Based on factory specs of curb weight 4180#, wheel base 116", Front/rear weight distribution 55.48%/44.52%, I did a "Sum of the moments" calculation: moving the rear axle .75" rearward will shift the weight distribution by only 12#. This will change the ratio to 55.77%/44.23%, a shift of only 0.29%. I don't know if this would be noticable, even on the autocross. This would have about the same impact as putting a set of decent speakers in the front doors, adding the chrome fuel rail covers, three guages to the A-pillar, a cell phone, toll change, some CD's and a Big Mac in the glove box. Switching to Aluminum heads or moving the battery to the trunk would reverse this "damage" 3 times over.

The spring/shock angle change is also miniscule. Assuming a spring height of roughly 12", a lateral change of .75" will change the spring and shock angle by only 3.6 degrees, and the ride height only .02". I don't know if this will have a noticable effect on anything.

The change in wheelbase is 0.65%. Noticeable? You wouldn't think so.

Conclusion: Unless my numbers are whack, if you want to spend the money to move the axle back (correctly), go for it, unless you are trying to get that last .1 second off your time at the track.