stb BmR or Hotchkis
10-24-2004, 02:45 PM
#24
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And what about the Spring/shock upper mount It is right there and what 360lbor more with a progressive spring? I saw a write up that the cornering weight of a f-body was like 1400lbs. And the sway bar transfers some weight to the other wheel in hard turns! The way I see it that is a ton of weight there! Now I think it was you mybe not that said a Aftermark k-member isn't as strong as a stock K, but then you said STB are useless? I am lost so I street drive my K-membered car and do realy hard turns, If the K can't that these loads then a STB would help right? Or where would that extra flex go?
Not trying to bust your ***** or anything but I just disagree!
Not trying to bust your ***** or anything but I just disagree!
10-25-2004, 07:30 AM
#25
2Fast ... Who deleted their post? And the ratings are 360 in/lbs, meaning for every inch of compression travel the spring can hold an additional 360lbs, assuming its a linear rate. If the spring can travel 4 inches prior to coil bind, it can hold 1440lbs.
From what I've read, been taught and experienced about the front suspension on a 4th gen F-Body ...
Using the above 1400lb figure, that would be spread between the front and rear tires, correct? That seems a little low for a 3700lb car. I would think 2000-2200 for the outside at 1G. But of course, we all know a stock F-Body can't turn at 1G ... so maybe 1400 is accurate.
Anyway, the forces applied start at the tire's contact patch.
Assuming 100% side loading traction (impossible by the way) the force is transferred to the hub assembly. Becasue the contact patch is almost a foot below the hub, the wheel tries to pry away from the hub, like when you use a church key on a bottle of beer.
Becasue the forces are below, the majority, if not all, the lateral force moves to the lower ball joint, because the wheel is still trying to pry away from the suspension.
This is then transferred along the lower A-arm and into the K-member.
The upper A-arm is nothing more than a stabilization point to keep everything in align. The stamped, sandwiched inner fender is well suited for this job.
But let's look at real life, instead of the hypothetical 100% side loading.
When negotiating a turn, the wheel turns about 15* or so at full lock. Again assuming 1G and no braking, the cornering weight of the car is spread between the front and rear wheels ... in actuality, the front carries more because the front tire is scrubbing against the pavement in order to change directions, but this is all hypothetical, right?
The loading forces are transferred the same way, however ... we now have the wheel turned. So the forces are transferred more rearward than laterally. Could this be why the A-Arm has the rear mounting point BEHIND the the tire's contact patch? I'll go out on a limb here and say ... YES!
Now, all that to illustrate that if the upper mount is so flimsy it flexes, tieing the 2 points laterally does no good because the forces generated are longintudinal, not lateral. But because the forces are so minimal, anything is overkill ...
Now 2Fast has a good point and one I hadn't considered ... a wheelstand. As the car comes down, the suspension compresses with minimal loading due to the contact patch.
If the susension bottoms out, it will either nail the bump stops (on the front frame rail, I believe) or bottom out the shock.
If the bump stops are removed and the shock bottoms out, the lower shock mount is the weak link, it would appear to a casual observer. Those 2 8mm standard grade bolts couldn't take too much shear forces.
If you have not removed the bump stops, the forces are transmitted to the bottom of the frame rail and come nowhere near stressing the upper shock mount.
whew ... that was way too much thinking for a Monday morning.
Bottom line ... an STB is $100 and your speed shop of choice will love you for buying one ...
From what I've read, been taught and experienced about the front suspension on a 4th gen F-Body ...
Using the above 1400lb figure, that would be spread between the front and rear tires, correct? That seems a little low for a 3700lb car. I would think 2000-2200 for the outside at 1G. But of course, we all know a stock F-Body can't turn at 1G ... so maybe 1400 is accurate.
Anyway, the forces applied start at the tire's contact patch.
Assuming 100% side loading traction (impossible by the way) the force is transferred to the hub assembly. Becasue the contact patch is almost a foot below the hub, the wheel tries to pry away from the hub, like when you use a church key on a bottle of beer.
Becasue the forces are below, the majority, if not all, the lateral force moves to the lower ball joint, because the wheel is still trying to pry away from the suspension.
This is then transferred along the lower A-arm and into the K-member.
The upper A-arm is nothing more than a stabilization point to keep everything in align. The stamped, sandwiched inner fender is well suited for this job.
But let's look at real life, instead of the hypothetical 100% side loading.
When negotiating a turn, the wheel turns about 15* or so at full lock. Again assuming 1G and no braking, the cornering weight of the car is spread between the front and rear wheels ... in actuality, the front carries more because the front tire is scrubbing against the pavement in order to change directions, but this is all hypothetical, right?
The loading forces are transferred the same way, however ... we now have the wheel turned. So the forces are transferred more rearward than laterally. Could this be why the A-Arm has the rear mounting point BEHIND the the tire's contact patch? I'll go out on a limb here and say ... YES!
Now, all that to illustrate that if the upper mount is so flimsy it flexes, tieing the 2 points laterally does no good because the forces generated are longintudinal, not lateral. But because the forces are so minimal, anything is overkill ...
Now 2Fast has a good point and one I hadn't considered ... a wheelstand. As the car comes down, the suspension compresses with minimal loading due to the contact patch.
If the susension bottoms out, it will either nail the bump stops (on the front frame rail, I believe) or bottom out the shock.
If the bump stops are removed and the shock bottoms out, the lower shock mount is the weak link, it would appear to a casual observer. Those 2 8mm standard grade bolts couldn't take too much shear forces.
If you have not removed the bump stops, the forces are transmitted to the bottom of the frame rail and come nowhere near stressing the upper shock mount.
whew ... that was way too much thinking for a Monday morning.
Bottom line ... an STB is $100 and your speed shop of choice will love you for buying one ...
10-26-2004, 06:31 PM
#26
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There where two videos posted in LS1Tech with cars that have dented the fender where the bolts bolt on the upper a-arm mount and another car that the fenders flexed so my they ripped the metal fender apart at the seem! One was harlans landing and the other was someones black SS!
And what about the part about the street car that has a BMR k-member. As some people are saying that there are much weaker than the stock unit and are known to break? Or why do the 25.2 roll cages have to have a 45* bar in ever 90* point in the cage! Someone must think it is needed?
And what about the part about the street car that has a BMR k-member. As some people are saying that there are much weaker than the stock unit and are known to break? Or why do the 25.2 roll cages have to have a 45* bar in ever 90* point in the cage! Someone must think it is needed?
10-26-2004, 08:26 PM
#27
Didn't see the videos and like I said above, I really hadn't considered a wheel stand landing. Only a handful of F-Bods can do that, while 100s of thousands can turn.
There are no aftermarket K-Members as strong as the stocker for lateral loading. I've seen a few BMR toothpick parts break.
The cages and the stress bars are ther for rollover protection. The forces generated can come from any and sometimes all directions during a rollover.
Plus, the WHOLE weight of the car (more than 1G during a violent rollover) is on a the bar(s) of a cage during a rollover, not less than 1/4 the weight, like MIGHT be sent through an STB while cornering.
There are no aftermarket K-Members as strong as the stocker for lateral loading. I've seen a few BMR toothpick parts break.
The cages and the stress bars are ther for rollover protection. The forces generated can come from any and sometimes all directions during a rollover.
Plus, the WHOLE weight of the car (more than 1G during a violent rollover) is on a the bar(s) of a cage during a rollover, not less than 1/4 the weight, like MIGHT be sent through an STB while cornering.
12-23-2004, 02:30 PM
#28
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Well This is all interesting. 
I dont know to much. But i did put the Hotchkis STB in, I noticed a difference. I put the eibach prokit on and didnt change the struts and notice my struts needed to be changed(it had a boaty bounce in the front kinda like a caddy) 
so i bought struts and shocks , and the STB, I put the STB on first before i the Shocks and struts and drove it around a few days before i put the Shocks and struts on, and it cut down on the boat like bouncing. And now that i have the new shocks and struts the front end is really tight. I dunno but thats my experience. If i think it works, then i guess i spent my money well. Plus i also think it looks cool, why not. 
I dont know to much. But i did put the Hotchkis STB in, I noticed a difference. I put the eibach prokit on and didnt change the struts and notice my struts needed to be changed(it had a boaty bounce in the front kinda like a caddy) so i bought struts and shocks , and the STB, I put the STB on first before i the Shocks and struts and drove it around a few days before i put the Shocks and struts on, and it cut down on the boat like bouncing. And now that i have the new shocks and struts the front end is really tight. I dunno but thats my experience. If i think it works, then i guess i spent my money well. Plus i also think it looks cool, why not.