That's it! Thanks!
Based on what I'm seeing, I have better camber gain than the FMJ spindle. Now to calculate the roll center and hope it is better too...
12:05 Garage- ’70 Duster build
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Based on what I'm seeing, I have better camber gain than the FMJ spindle. Now to calculate the roll center and hope it is better too...
mygasser
Well-Known Member
re the suspension travel.... if your total will be 4" you should have 'about' 2 1/2" compression and 1 1/2" extension. so at ride height the suspension should be compressed roughly 1/3. this is standard practice for suspension setup. you probably already knew but you mentioned 2" up and 2" down so.......
neil.
neil.
I'm waiting for new lower bumps to come in before I have a real measurement. I'll have them touch the LCA at 2", but I'm sure they will compress enough to get another 1/2" at the wheel.
I took several measurements with the suspension hanging on the ride height simulators Denny sends with the kit. They may not be dead nuts exact to my ride height, but its very close. I used the suspension calculator online to determine the roll center. There are some measurements that are difficult to get exact, but I messed with the numbers to see what changes it made. Some measurements made drastic changes while others did very little. The calculator outputs the tire camber, UCA and LCA angles. The results are damn near the same as what I measured, maybe just a tenth or so off. Either way, this looks fairly promising
DionR
Well-Known Member
I wonder what results you would get with the original BJ's.
I messed with it but not with as much precision as this time and it was 4" below the ground. I believe this was due to the UCA and LCA angles never intersecting. I don't quite understand the math behind that. Picture the LCA near level and the UCA pointing to the sky.
DionR
Well-Known Member
Not sure I have it right but here is how I think about it.
The way I picture it is, they upper and lower lines either intersect opposite of the CL of the car from the tires, or pass through the CL of the car and intersect. If the lines intersect opposite the CL of the car, and then you draw a line from that intersection to the CL of the car through the middle of the tire contact patch, the roll center is probably underground like your estimate with the original setup.
Another way to think about it might be that if the line from the control arm intersection passes through the tire contact patch before hitting the CL of the car, the RC is probably pretty low. Unless maybe both the inner mount elevations are above their respective BJ elevation.
Something like this?
DionR
Well-Known Member
Something to keep in mind is that the BBD article doesn't talk about what ride height they measured the roll center at. Or at least as far as I can tell they didn't, maybe I missed it.
The article is pretty old, so I wouldn't be surprised if it was at a stock ride height. So, while they list a roll center, I would bet it isn't much use comparing them.
Not that you said you were, just an observation.
Also, I wonder how camber gain is affected by initial camber. They started with zero camber and it seems like the norm now is a half to one degree negative chamber for street cars.
The article is pretty old, so I wouldn't be surprised if it was at a stock ride height. So, while they list a roll center, I would bet it isn't much use comparing them.
Not that you said you were, just an observation.
Also, I wonder how camber gain is affected by initial camber. They started with zero camber and it seems like the norm now is a half to one degree negative chamber for street cars.
This is very true.
I don't think static camber changes camber gain by any measurable amount. Obviously, more static negative camber shortens the UCA, but it is such a small amount, I doubt it is even measurable. My static is currently 1.7-1.8. I just started from zero to make it easier to understand.
If anyone needs some reading material, here's a story about my car on Mopar Connection magazine.
moparconnectionmagazine.com
Gallery: Tim Talbot's Duster Does Corners, Goes Straight, and Cruises Effortlessly - Mopar Connection Magazine | A comprehensive daily resource for Mopar enthusiast news, features and the latest Mopar tech
At the 2023 Holley Moparty at Beech Bend Raceway Park in Bowling Green, Kentucky, a black, modest appearing 1970 Duster was mixing it up with twenty heavy hitters in the Grand Champion Competition vintage class. The Duster, owned by Tim Talbot of South Louisiana, finished 4th in the class on a...
moparconnectionmagazine.com
So the Big Block Dart article is just a reprint of Bill Reilly's article that was originally published by Mopar Muscle. It's still available online here https://www.motortrend.com/how-to/mopp-0503-swapping-a-and-b-disc-brake-spindles/
Unfortunately, when Hot Rod and then Motor Trend brought all of those articles over from MM the way they're posted online doesn't capture all of the original captions under the photos, which is where they described the ride height of that car.
I do know, because I've posted it here before when the article was complete, that the car that provided the data for that article was lowered 1" from stock. I've tried to get most of those important articles in the original magazines, I'm not sure I have that one though.
Found it! The original article is in the March 2005 Mopar Muscle. The part that apparently hasn't been carried over to the current online version of the article is this picture and its caption, which explains the ride height settings on the car used to create the geometry tables for both the stock and FMJ spindles.
Got the car back on the ground and finalized the alignment, which is 7.25 degrees of caster, 1.9 degrees of camber, and 1/32" of toe out. I tightened the shocks to my auto cross settings and went for a ride. The car definitely feels flatter with aggressive turning, but I won't know for sure until I run it around the cones.
With the new 1/2" wider track width, I did have to roll my fender lips. Fortunately, I have a friend that owns the tool to do this, so it was quick and easy to get it done. I know this is common practice for most that run a wide wheel. I checked for contact with the wheel at full compression and steering lock. It appears I'll have about 1/4" before anything touches. I do feel like the hub is in the correct place for me to add an inch of backspace to the wheel and finally get a 275 on the front.
While making these adjustments, we also addressed the sway bar. My tire was contacting the bar on sharp turns. Denny made a new bar that has bends similar to the Helwig and Hotchkis pro touring bar. The sway bar is no where near the tire now at full lock.
With the new 1/2" wider track width, I did have to roll my fender lips. Fortunately, I have a friend that owns the tool to do this, so it was quick and easy to get it done. I know this is common practice for most that run a wide wheel. I checked for contact with the wheel at full compression and steering lock. It appears I'll have about 1/4" before anything touches. I do feel like the hub is in the correct place for me to add an inch of backspace to the wheel and finally get a 275 on the front.
While making these adjustments, we also addressed the sway bar. My tire was contacting the bar on sharp turns. Denny made a new bar that has bends similar to the Helwig and Hotchkis pro touring bar. The sway bar is no where near the tire now at full lock.
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DionR
Well-Known Member
I've always wondered what the mod did when Shelby lowered the UCA mount on the GT350 1". After all this, makes sense that he was getting the UCA sloped down towards the center of the car and changing the roll center. Cool.
Have to admit that I am a little disappointed with the COC claim that they handle better if the suspension geometry has the UCA's sloping down from the center of the car and the roll center underground.
@HemiDenny, seems like you have a "Super Slammer" kit or something? Does that move the k-frame and LCA up on the chassis, thereby raising the top of the spindle in relation to the UCA chassis mount?
Have to admit that I am a little disappointed with the COC claim that they handle better if the suspension geometry has the UCA's sloping down from the center of the car and the roll center underground.
@HemiDenny, seems like you have a "Super Slammer" kit or something? Does that move the k-frame and LCA up on the chassis, thereby raising the top of the spindle in relation to the UCA chassis mount?
If the roll center adjustment works as I anticipate, the current bar may be fine. Now that I have a little education on the topic, I think a bigger bar would have been a band aid to the real problem. If the problem is fixed, I won't need the band aid.
To be fair, I've never seen Denny claim his kits offer better handling. That's kinda where I come in. Also, Denny doesn't force you to a specific spindle like some others do.
I know QA1 is claiming improved handling and I'd really love for someone to take measurements so we can all learn.
Tim is correct, HDK never claims they make the cars handle better.....I will however claim that the car will drive a whole lot different. Dropping a few pounds with the ability to (easily) be more aggressive on the the alignment specs to match our modern tires is the name of the game. Add the additional room afforded by the elimination the OEM steering and torsion bars that allow for easier powertrain transplants and it is a win / win for us Mopar hot rodders. Definitely not for everyone, especially those that want to keep their OEM ride.
For the record......Tim has an off the shelf / standard HDK package, not a "Slammer" or "Super Slammer" . Those packages were built for specific customers that wanted to lower the body to the extent they required extensive fabrication like raising the transmission tunnel and the OEM inner fenders. And yes, in those versions, as the the body drops, the K frame and its pivot points are raised. On most of the "slammer" builds standard length upper ball joints were used.
I am grateful for Tims input and glad to reciprocate with HDK "help" wherever possible.
Denny
HDK
DionR
Well-Known Member
Wasn't really calling Denny out on that, more of a general statement.
What other options are there for spindles with the HDK?
QA1 also uses M2 "style" spindles which I am betting results in a less that perfect UCA arrangement. Maybe they ship with an extended UBJ like you put in? Betting not though. Sorry, but feels like bad advertising rather than truth to me.
I really do think that the mindset for most is that a COC is needed to make an old car handle all because a Chevy really does need a new front suspension design to make it handle. And thus all makes need one because, like, Chevy is the best so if they need it so do we. Duh.
Any Mustang 2 spindle will work on the HDK. However, I think the new ride tech spindle for chevelles will work. I found a steering arm that will provide the same steering angle as the M2. It would just be a matter of using the correct ball joints. The best part about the HDK is the adjustability and adaptability.Wasn't really calling Denny out on that, more of a general statement.
What other options are there for spindles with the HDK?
QA1 also uses M2 "style" spindles which I am betting results in a less that perfect UCA arrangement. Maybe they ship with an extended UBJ like you put in? Betting not though. Sorry, but feels like bad advertising rather than truth to me.
I really do think that the mindset for most is that a COC is needed to make an old car handle all because a Chevy really does need a new front suspension design to make it handle. And thus all makes need one because, like, Chevy is the best so if they need it so do we. Duh.
If a GM spindle will work, a whole new realm of brake options open up.
DionR
Well-Known Member
Sorry Denny, but I've got to say that feels like "politician speak" to me. Drive different? Certainly not worse, so you must mean better. Which could be interrupted as "handle better", and if someone else were to say that and you didn't correct them then you didn't say it, right? And if they go from a worn out mis-aligned TB suspension to all new parts, they wouldn't really be wrong would they?
Don't take that harshly, not trying to poke at you, but you have to see that as a little bit of a double speak.
Honestly, I struggle to see how a TB suspension with a decent wheel rate, a good amount of caster and decent camber and a Borgeson box would feel much different that a COC.
Unless you mean that the roll center is underground with the COC so it actually has more roll in the corners than the TB suspension. That would be different. But no one says it will feel a whole lot different and mean worse, so...?
I would never argue that there aren't some advantages to a COC, fitting a motor is certainly one of them. I would argue that it isn't the only way to do so though. Not that you have said that, but I know others have at least implied it.
And to be clear, a COC isn't required to be more aggressive on the alignment specs, so not sure I would include that in the list of advantages. Certainly the COC kit adds the ability to length or shorten the LCA, but that isn't the only way to get more aggressive on the alignment specs so not sure how it is different.
Ok, to me that comment says "if you don't care about handling keep the TB's, but if you do want it to drive and handle like a modern car then you need a COC". Sorry, mixed messages here.
That's probably not what you meant, but it's what I hear.
Gotcha. I wasn't sure if I was remembering that correctly. It was just an idea since the M2 spindles appear to be on the short side for a handling package.
It's interesting that the "Slammer" and "Super Slammer" kits require inner fender work and tunnel modifications. So bringing the k-frame up so the spindle height is better and the geometry is actually decent causes all kinds of problems. Which kind of implies that the real issue is that the spindle is just too short.
I think with Tim's input you will be able to get to a package that will actually handle well. Not to say it didn't before, but the results Tim has posted so far imply that there were some deficiencies that were unknown before.
It also implies to me that there isn't a COC on the market that has a good roll center. I really wonder if QA1 already knows this but ignored it.
Either way, let me end by saying that I am glad that you (Denny) and HDK are here and are always looking to improve their product. I do think the HDK is the superior product in the COC arena and would be the one I would chose if I went that direction.
DionR
Well-Known Member
So you didn't try the ride tech spindle, right? Would be interesting to see how that all works. Did that spindle accept the wheel bearing you are already running?
The QA1 kit start with M2 spindle but they modify the steering arm. "QA1 spindles start as Mustang II components and have modified steering arms. Standard Mustang II spindles cannot be used."
Its all good.
The difference in the steering feel is best described as a more modern precise feel. I don't consider that any part of handling but I can't help how some might look at it.
Yes, the widely used Mustang II spindle is shorter than our OEM Mopar spindles, hence the extended upper ball joint to help out.
Tims package is as unique as any other package is unique.......all kinds of different ride heights and tire diameters which IMO generally effect the UCA angle. Tim is getting his dialed in for what works best for Tims application. On my personal Duster, I run a lot taller (27") tire (raising the spindle pin / raising the upper ball joint ), and tucked further inward allowing the chassis UCA attaching points to be lower to the ground. My UCAs have a nice downward towards the center of the car angle to them.....but that is my application......coffee getter.
The Slammer / Super Slammer are designed for those that want to lower ONLY the body (I think they used to call it challeling) keeping the suspension at OEM height.....so naturally you would have to raise the driveline (tunnel) and the inner front fenders for tire clearance. I have found over the decades that while many like to talk about such a project, most do not want to do the mods and are looking for something that simply bolts in.....so they are not a big sellers.
no offense to the TB people......I own cars with them. Simply, a rack / coilovers are not for every project and everyone.. The HDK UCAs (available separately) allow for increase caster without the bind, something that most struggle with using strictly OEM components.
It is fun to work with the innovative guys here on FABO. Rarely a dull moment and that is the way I like it!
The difference in the steering feel is best described as a more modern precise feel. I don't consider that any part of handling but I can't help how some might look at it.
Yes, the widely used Mustang II spindle is shorter than our OEM Mopar spindles, hence the extended upper ball joint to help out.
Tims package is as unique as any other package is unique.......all kinds of different ride heights and tire diameters which IMO generally effect the UCA angle. Tim is getting his dialed in for what works best for Tims application. On my personal Duster, I run a lot taller (27") tire (raising the spindle pin / raising the upper ball joint ), and tucked further inward allowing the chassis UCA attaching points to be lower to the ground. My UCAs have a nice downward towards the center of the car angle to them.....but that is my application......coffee getter.
The Slammer / Super Slammer are designed for those that want to lower ONLY the body (I think they used to call it challeling) keeping the suspension at OEM height.....so naturally you would have to raise the driveline (tunnel) and the inner front fenders for tire clearance. I have found over the decades that while many like to talk about such a project, most do not want to do the mods and are looking for something that simply bolts in.....so they are not a big sellers.
no offense to the TB people......I own cars with them. Simply, a rack / coilovers are not for every project and everyone.. The HDK UCAs (available separately) allow for increase caster without the bind, something that most struggle with using strictly OEM components.
It is fun to work with the innovative guys here on FABO. Rarely a dull moment and that is the way I like it!
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I didn't try the ride tech spindle. I was leaning that way until I found the 2" long ball joint. I don't see any reason why it wouldn't work. They don't publish the ball joint taper and I found conflicting information on what Chevelles actually had. I would have called them to get more info before moving in that direction. What I have found is the circle track racers have gone through all of this and have many parts to modify control arm angles and GM spindle steering arms. The great thing about the HDK having screw in ball joints for both upper and lower is pretty much anything goes if you have enough tenacity to figure it out. Perhaps a GM spindle is the way to go since there are many options in heights and brakes. Again, this is all speculation that it will work, but I don't see any reason why it wouldn't.
Dion, you can go back and see where I mentioned the car felt better. It really is hard to explain, but it felt better right out the box from Denny. Perhaps its just the steering since there's no dead spot, or maybe it just well built chromoly tubing not flexing like a 50 year old stamped steel K-member and LCAs. I can't pin point exactly what it is. For the regular guy driving to the local cruise night or ice cream shop, he will interpret this as "handling better." But does that same guy even know what type of suspension geometry offers superior handling? I doubt it.
The car did pretty good without any of the current modifications. I'd bet 95% of people would call it good and not touch it. I don't fall into that statistic.
My local autocross is mid January. I'll know more then, weather pending.
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