Sky Render's Build Thread

[Rehagen Racing]

We actually use the rubber stock UCA most of the time. We've had 1 go bad and it was 4 years old. It was more from lack of maintenance. We can use the FRPP urethane upper insert and do at times, but we don't notice a huge difference.

Our rule package will allow us to use the different LCA's from FRPP.

 

[sheizasosay]

So there i was thinking for the longest time that heims were made to solve a problem. Now, apparently there is no problem or its not even close to mattering.

So is it fair to say that theses findings below are completely wrong? What am I missing?

Standard 2 piece setup using only 85 durometer bushings:





5 degrees of total rotation = 124.7 foot/pounds of torque



7.5 degrees of total rotation = 156.4 foot/pounds of torque



10 degrees of total rotation = not measurable with fixture. The 1/2" grade 8 bolt twisted in half at 9.2 degrees which was 210 foot/pounds of torque.

While the street/extreme joint has "0" all the way to 10 degrees.

Copied from J&M's web as the source cited above.

 

[BMR Tech]

Sorry for the confusion, but can you show a picture or something, sheiza?

Where is the a 1/2" bolt? (through-bolt?)

How do the factory bushings compare?

Where, exactly is the ft.lb TQ being measured from?

"Only 85" durometer.....well, what does everyone use?

Was a factory differential bushing considered in that exercise?

That is good info, but you need to know much more before using that data for/against applying it to this discussion.

 

[Whiskey11]

Sorry for the confusion, but can you show a picture or something, sheiza?

Where is the a 1/2" bolt? (through-bolt?)

How do the factory bushings compare?

Where, exactly is the ft.lb TQ being measured from?

"Only 85" durometer.....well, what does everyone use?

Was a factory differential bushing considered in that exercise?

That is good info, but you need to know much more before using that data for/against applying it to this discussion.

In addition to this, we are given units that are outside what we would expect for spring rates. I think the amount of added wheel rate is far more important than the amount of torque required to deflect the bushing. I would also point out that the bolts on a LCA should not be carrying load as the metal sleeve between the bolt and the bushing should be under compression between the ears on the axle and that should be carrying the load.

 

[csamsh]

Copied from J&M's web as the source cited above.

J&M is trying to sell stuff. You cited an advertisement. Not that the information is bad, but it's still an ad.

 

[BMR Tech]

Not only that, but, why were those angles chosen?

Anyone have any data, showing the relation (in degrees) of the chassis and the axle?

I think you would be surprised, by how much the axle "actually" rotates. It is probably much less than most think. I have always told my customers that I believe the centered UCA is not seeing as much rotation as people make you to believe.

There are many other variables, too. Like the shape of the bushing.

Food for thought; if you have 7* of rotation at the bushing on an UCA, you will have somewhere around 4.25" of separation on one side, and 4.25" of compression on the other side (wheel-to-chassis OR tire-to-fender). I don't even think a stock vehicle's axle will articulate that much?

 

[dontlifttoshift]

Yep, I have always used the 5* rule of thumb. any more than that will only happen in extreme situations, like rock crawling. IOW, if you are seeing more than 5* of roll there is more wrong with your setup than bushing compliance......

In the lower control arm thread Gmitch (I think) said he had tried several LCA and the J&M LCAs were the only ones that didn't snap oversteer.

 

[BMR Tech]

Yeah, 5* would be in the neighborhood of around 3.25" travel on the outer ends of the axle.

When I see people posting pictures, it only looks like, to me, that they are seeing maybe 2" of travel at the axle ends....sometimes it looks to be even less.

Here is a shot of Whiskey's car in a corner:

Hard to tell, but I wouldn't think that he has much more than 2" on each end, in this shot.

 

[Whiskey11]

Yeah, 5* would be in the neighborhood of around 3.25" travel on the outer ends of the axle.

When I see people posting pictures, it only looks like, to me, that they are seeing maybe 2" of travel at the axle ends....sometimes it looks to be even less.

Here is a shot of Whiskey's car in a corner:

Hard to tell, but I wouldn't think that he has much more than 2" on each end, in this shot.

I am not sure when that photo was taken (pre Springs Nats since no Tire Rack banner) so more than likely last year before coilovers. I think Poly becomes less of an issue the less roll the car has since everything is articulating less and less the stiffer you go. I know Maximum Motorsports did an analysis on the SN95 control arms and I wonder if they did for the S197 as well. I dont know...

More up to date photo:

Height to fender in front is 27 1/8" and out back is 27 3/8" so probably an inch and a half tops of body roll?

 

[BMR Tech]

Good info.

Yeah, 1.5" of roll is maybe 3* or so.

I would have a hard time believing a poly-bushed UCA in a set-up with that little roll, would produce much snap.....and I would highly doubt the effects would present themselves noticeably on a road course. I could be wrong though.

People have to keep in mind, the poly bushing is not going to move that same 3*......because most people still have a factory style diff bushing. Which means the poly bushing may not even twist, or create bind and deflection....at all.

 

[dontlifttoshift]

...and in the case of a LCA both the front and rear bushings would absorb the twist. It may not be an even split front the rear but it would be divided up.

 

[BMR Tech]

.....and in that case, measuring the resistance / force it takes to twist the bushing.....gets complicated, because the effect on the bushing is not side-to-side, as much as it is up and down....creating even less "bind"

 

[SoundGuyDave]

.....and in that case, measuring the resistance / force it takes to twist the bushing.....gets complicated, because the effect on the bushing is not side-to-side, as much as it is up and down....creating even less "bind"

Very true. HOWEVER, the fact remains that ANY rubber or poly bushing is still going to exhibit force that affects the wheel rate of the car in a roll condition. That force may or may not be linear, but it is still present. It doesn't matter if it's natural rubber, synthetic rubber, 58, 68, 80 durometer poly, Whiteline's proprietary unobtainium compound, or any other elastic substance, it still exhibits torsional resistance. If you REALLY want to eliminate that impact on wheel rate, the only solution is some sort of Heim, monoball, Johnny-Joint, etc. But, as has been noted, there is a tradeoff. By eliminating that elastic suspension, you have also eliminated ANY vibration absorption, and the result is increased NVH. For the truly hardcore, it's no issue, but for the street-driven car, it's probably not worth the aggravation. Can poly bushing work acceptably well in the lower control arm? Absolutely. Just lock the car down with massive bars, uber-high spring rates and damping curves, and they'll do just fine. I forget who said it, but: "Any suspension design will work just fine if you prevent it from moving."

I have personally been through three different designs of LCAs. Stock rubber, stock arms: They sucked. Limp as noodles, and the rear end could dance around like crazy. Adjustable poly/Heim: They sucked. After two track days, the poly bushings had destroyed themselves, tearing from the roll forces running through them. Adjustable Heim/Heim. Near-perfect. Pretty massive NVH increase (not as much as the poly motor mounts, though!), but absolute precision in force management, with an appreciably quicker reaction to load transfers. As it is, I think my tolerance for NVH is perhaps a tad higher than most. For the street-driven car, I personally think the best bet would be a nice, stiff tubular arm, with nice, soft rubber bushings. At least if you're going to be pushing the car around corners. For the straight-line crowd, go poly.

Right now, the only bushings in the car that aren't Heim joints are the swaybar bushings and the front lower control arm bushings. I understand MM is working on Delrin FLCA bushings, and I am patiently waiting for those to come out.

 

[BMR Tech]

I agree with you. Everything you said about bushing materials. I preach what you posted, everyday of my life over the phone....lol

As I posted in Post #55....I recommend a spherical-style bushing on the UCA.

As for LCA, when a customer tells me they are using their car for handling duty, I send them towards our TCA021....which is a Poly/Rod-End style LCA.

The arms I mentioned above, are FLYING off of our shelves. They are cutting 1.3 sixty-foots, as well as being run on a large amount of road-course cars.

All that said, a well designed Poly bushing in both the UCA and LCA will do just fine for 93.675% of the handling fanatics out there.

 

[BMR Tech]

I still remember the good 'ole days when LCA Relocation brackets were considered "bad" for handling....

SGD: I gotta admit, the unobtanium made me chuckle...lol

 

[sheizasosay]

I still remember the good 'ole days when LCA Relocation brackets were considered "bad" for handling....

SGD: I gotta admit, the unobtanium made me chuckle...lol

I went through that debate and kept bugging people on this forum and throughout until I understood completely what was going on and also doing experiments on my own car with them. But you're right, there was a bit of that going around. Always the answers were "I heard" or "so and so said they are a no-no". At the end of the "drive for info", it is understood more. That's a good thing. It also stopped would be nay-Sayers and promoted purchases as the word spread. That's all a good thing....a "correctly" informed customer and a product understood and appreciated. I hate doing this on my phone, but it's all I got for now. Harder to organize myself. But, as usual, I site my info in hopes of getting it addressed if its wrong or to debate and wade through what matters and what doesn't. I certainly don't mind info being challenged.

Give me a hot minute, let me try to do what I can to address the info I'm now somewhat responsible for and I'll get back.

Oh....BMR, you ask about the "using only 85 durometer bushing....what is everyone else using". I would ask what BMR is using in the LCAs. I think it's pretty realistic to assume anything over 85 durometer would increase the value of those torque numbers listed from J&M. Though that "test" is in question, what I'm saying shouldn't be, as the higher the durometer, the stiffer the bushing.

And I would also totally agree that a car with higher rate springs would see less roll and less bushing deflection or bind relative to the same car, softer springs, and same bushings.

There is a reason MANY race cars use heim joints or other articulating joints and its not because they like NVH.

I'll get back later.

 

[Whiskey11]

Dave, Colin Chapman is your man for that quote: "Any suspension, no matter how poorly designed, can be made to work if you just keep it from moving." Which is a pretty damn ironic statement coming from the inventor of the Chapman Strut in which the best solution to make a car handle with them is to lock the car down...

When you hear me use the phrase: "Chapman's lawing your suspension" that is what I am talking about.

Kelly: Relocation brackets are still very very bad for SCCA autocrossers, unless your goal is a SM or CP car...

 

[BMR Tech]

Correct. There is a reason, no doubt about that.

On the other hand, you have shops like Rahagen Racing, who just posted that they run stock UCA's and Poly Bushed LCA.

All of our bushings are now either 90 or 95 durometer.

We played around with lower durometer / softer bushings earlier on, to only find ourselves replacing/warrantying poly bushings, much too often.

We offer about every combo there is, so I have the luxury of offering a complete rod-end set-up....a poly/rod-end combo....or the most common; all poly.

Poly has its place. I would never sit and claim that it is the "best" choice in a handling application, but it all just depends.

 

[BMR Tech]

Kelly: Relocation brackets are still very very bad for SCCA autocrossers, unless your goal is a SM or CP car...

Can you elaborate? If a car is lowered 1.5" - are you saying an autocross car will perform better with the LCA angled down towards the chassis at an angle of 3-4*......than it will with the LCA pointing up towards the chassis at an angle of 1-2*?

Are you implying that dropping the front points of the UCA and LCA mounting points, by lowering the car, and leaving the rear mounting points alone, is perfectly fine for auto-crossing, and it is not worth the effort to re-adjust the IC/AS setting?

Thanks for the post!

 

[csamsh]

Can you elaborate? If a car is lowered 1.5" - are you saying an autocross car will perform better with the LCA angled down towards the chassis at an angle of 3-4*......than it will with the LCA pointing up towards the chassis at an angle of 1-2*?

Are you implying that dropping the front points of the UCA and LCA mounting points, by lowering the car, and leaving the rear mounting points alone, is perfectly fine for auto-crossing, and it is not worth the effort to re-adjust the IC/AS setting?

Thanks for the post!

They're great from a performance point of view, terrible from a rules point of view. Relo brackets put us Mustangs in classes with stripped out AWD turbo cars on big Hoosier A6's, (street modified)

or REALLY stripped out pony cars (no windshields, full slicks, engine/trans swaps, cages, no interiors, etc. (C-Prepared)

To remain in E-Street Prepared or Street Touring Xtreme, (next year Ultra), streetable and non-trailered classes, we can't replace lower arms, and we can't relocate lower arms. This results in doing stuff like having two sets, only swapping on the crappy stock arms to run autocross. Because...that makes sense.