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Re: Tall vs. Short Spindles
[Re: 69 Road Runner]
#17853
10/31/05 09:35 AM
10/31/05 09:35 AM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
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Quote:
Rick, what's your opinion on using the later spindles with the tubular control arms? Does that fix the concerns that you have?
No. Modified or tubular upper control arms can change caster or camber, but can't fix the altered geometry / toe pattern.
Maybe I'm thick...? But the correct, OEM-engineered knuckles are readily available, repro or used. Since the OEM setup is known / proven to have minimal bumpsteer, and the tall knuckles are known to be a problem, why not just do it right?
Here's another E.G. from my limitless stash of stories:
One of the first years I ran the One Lap of America in my Valiant, two guys - great guys - from western Canada showed up in a pink Charger. They had the tall knuckles, calipers swapped, and I noticed the brake hoses were way too short and/or misrouted. I helped them fix that before the event began.
They claimed that the car had "perfect alignment". And it seemed fine on the highway sections. But on the track, they spun the car, went off, etc., repeatedly. I've always wondered how much of their grief was due to large amounts of bumpsteer.
Rick
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Re: Tall vs. Short Spindles
[Re: BergmanAutoCraft]
#17854
10/31/05 12:12 PM
10/31/05 12:12 PM
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Joined: Feb 2003
Posts: 4,204
Fort Worth, TX
Clair_Davis
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Posts: 4,204
Fort Worth, TX
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GMachine, I'm interested in them, since I'd like to have some extra travel in the suspension for the sake of overkill, but I'm not really having a problem with suspension movement with the 1.14" bars. Add to that the fact that I'd almost certainly HAVE to go with tubular uppers to regain the clearance I'd lose at the UBJ with the taller spindle... I think I'll let you blaze that trail for me...  If/when I get the urge to go with 17x9's up front, I'll probably have to go there. Are you thinking about the Fatman spindles? I don't suppose they took any time to look at A/B/E bump steer issues since they were trying to crank out a spindle for the street rodders to use on their Aspen/Volare front end swap kits... Clair
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Re: Tall vs. Short Spindles
[Re: Rick_Ehrenberg]
#17855
10/31/05 02:56 PM
10/31/05 02:56 PM
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Joined: Jan 2003
Posts: 27,490
So Cal
autoxcuda
Too Many Posts
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So Cal
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Quote:
Not quite sure what you mean by 'spindle axis' - I would take that to mean a line drawn between the centers of the two wheel bearings. But what you seem to be saying, then, is nothing that happens above the lower balljoint matters - if the arc of the upper balljoint changes, then toe does not change? That's simply not true. Go change camber and see what happens to toe!
Yea, when you change your camber you toe changes. But we're talking 1/8" difference toe change with the taller spindle.
Would you agree that a positive caster change lowers the rear tie rod end hole and thus ALSO changes bump steer?? I think changes with 4-5 degrees will see similar bump steer effects.
Also a lot of caster induces scrub when the wheel goes through its turning motion. Also it will change the cross percentage on a set of scales which sort of upsets the car in a corner. Even though there are some bad effects of caster, on a production based car the cornering is improved because it gives you some camber effect when the wheel is turned.
The suspension geometry deal is a game of compromises. When something is perfect something else get worse.
On our race team we set bump steer to the .005. And we have gone out to a race, made changes, won the race, and afterwards the bump steer was way off. Oh well, still won.
There are some aftermarke setups with horrible bumpsteer. I personally just haven't seen 1/8" at 4.5 travel beeing a big difference.
What I wrote above about bump steer and the lower half of the spindle occurs in only one specific case that doens't really happen in the real world. I edited that out. Sorry about that.
Quote:
They claimed that the car had "perfect alignment". And it seemed fine on the highway sections. But on the track, they spun the car, went off, etc., repeatedly. I've always wondered how much of their grief was due to large amounts of bumpsteer.
That's a lot of inferences. There could have been a ton of reasons for that. You need a back to back test run with the two different bump steers ONLY to see the bump steer affect. The taller spindle on a race car that is dialed in will need a different setup because the roll center went up (understeer) and the front tire temps should be better (more grip/oversteer) because camber is better.
I just like the taller spindles for the performance potential of more camber gain. That is sooo key in get good front tire grip and good tire temps at the track. For me, I'd just adjust out the bumpsteer if it was way bad from factory to start with.
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Re: Tall vs. Short Spindles
[Re: Digger]
#17857
10/31/05 06:21 PM
10/31/05 06:21 PM
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Joined: Jun 2005
Posts: 58
Oregon
Digger
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member
Joined: Jun 2005
Posts: 58
Oregon
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FYI, the site: www.piratejack.net/spindle.html is listing new spindles with brackets for $210. Don't know if they are the same source as MP Brakes, The Paddock and YearOne or not.
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Re: Tall vs. Short Spindles
[Re: nd65]
#17859
10/31/05 08:05 PM
10/31/05 08:05 PM
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Joined: Nov 2003
Posts: 3,577
Long Island, NY USA
BergmanAutoCraft
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Posts: 3,577
Long Island, NY USA
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The spindle debate is merely, can we replace our A/E spindles with the 3/8" taller more plentiful F,M,J,M,R and 73 up B body units. This started, because I mentioned I ordered the fatman spindles, which allow me to lower my car more, and use more t bar preload in the process. Now, everyone is claiming there is an excessive toe change through the suspensions range of motion if the taller spindle is used (bumpsteer). I am still debating sending the spindles back, but I'd like to see them in my hands before I make that decision. For all practical purposes I'm sure tere would be no ill effects for the swap, but with at least on place making new replacement spindles it isn't necessary to go that route. I am stuck with the taller spindle, because noone makes a drop spindle based on the A body design.
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Re: Tall vs. Short Spindles
[Re: BergmanAutoCraft]
#17860
10/31/05 09:13 PM
10/31/05 09:13 PM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
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Marlboro, NY, USA
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Quote:
because noone [sic] makes a drop spindle based on the A body design.
...I'm pretty sure there are some good ones, properly forged, made in Australia. Not sure if they are '73-up or '72-down though.
Rick
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Re: Tall vs. Short Spindles
[Re: 69 Road Runner]
#17862
10/31/05 11:06 PM
10/31/05 11:06 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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First the tall spindle detractors claimed it would overextend teh ball joint. That argument was shot down so now they claim it'll cause bumpsteer.
That claim merely shows thier lack of understanding of front suspension design and the definition of bumpsteer.
Bumpsteer is caused by the tierod assembly moving in a different arc from the inner and out pivots of the LOWER CONTROL ARM. The height of the spindle will never change the relationship of the tie rod assembly to the lower control arm. In fact what bumpsteer that is inherent to the mopar front suspension is due to the torsion bars being where the inner tierod pivot should be.
Bumpsteer is a change in the direction of the tire as the assembly moves up and down. It affects toe and steers the car in a manner inconsistent with the driver's input.
What a taller spindle can cause is a change in toe as the spindle moves up and down. In the taller spindle test written up in MM what could be called excessive toe change occured at max droop. It could be said that the taller spindle merely accentuates any bumpsteer issues you have. BTW, if you expect good handling with your UCA on the bumpstop then you live somewhere outside the realms of physics.
Anyway, you might say the effect of the taller spindle at full droop is identical to bumpsteer (you'd be right) but the cure is completely different and they are different problems even is the SYMPTOM is the same or similar.
Now I am sure the bumpsteer fans will say 6 of one or a half dozen of the other. Well, words are all we have here and if you can be bothered to use them right then you are not likely to be taken seriously by those who do know what the words mean. Which is exactly how internet myths perpetuate.
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Re: Tall vs. Short Spindles
#17863
11/01/05 12:13 AM
11/01/05 12:13 AM
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Joined: Jun 2005
Posts: 58
Oregon
Digger
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Posts: 58
Oregon
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Here's a concise technical description of bump steer: www.racerpartswholesale.com/longtech3.htm It suggests that the upper ball joint position at least plays a minor role in bump steer. This link: www.bakerprecision.com/longacr17a.htm describes how to measure bump steer. It sounds like somebody needs to take the time to make the measurements to put this matter to rest.
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Re: Tall vs. Short Spindles
#17864
11/01/05 12:25 AM
11/01/05 12:25 AM
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Joined: Feb 2003
Posts: 7,982
Scranton, PA
Montclaire
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Posts: 7,982
Scranton, PA
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Quote:
First the tall spindle detractors claimed it would overextend teh ball joint. That argument was shot down so now they claim it'll cause bumpsteer.
Yes and no. It was found that ball joints built to stock specs, or NOS examples, will bind. Replacements, for whatever reason, will come very close to their limits, but do not bind. At least most won't. I'm sure a few out of hundred would, depending on the manufacturer.
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Re: Tall vs. Short Spindles
[Re: Montclaire]
#17865
11/01/05 01:02 AM
11/01/05 01:02 AM
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Joined: Jan 2003
Posts: 4,323
NY NY
340duster340
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master
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Posts: 4,323
NY NY
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here are some thoughts from a mechanical engineer who worked for FoMoCo, and is currently working at a leading product development firm, i also have 7 years diagnostic auto experience, and have had a few dusters and darts.
I WOULD NOT MODIFY STEERING GEOMETRY UNLESS a) you were a trained and certified chassis builder or b) using factory approved parts
basically these vehciles are designed to used stock parts, in stock locations, and changing suspension geometry could cause a loading condition that the structure was not designed for which could lead to failure and drastically altering or mis-matching parts could also cause premature failure. this should be common sence.
1966 Dart GT
...down to only 1 mopar for the first time in 15 years!
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Re: Tall vs. Short Spindles
[Re: Rick_Ehrenberg]
#17866
11/01/05 01:25 AM
11/01/05 01:25 AM
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Joined: Jan 2003
Posts: 27,490
So Cal
autoxcuda
Too Many Posts
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Posts: 27,490
So Cal
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Quote:
Quote:
because noone [sic] makes a drop spindle based on the A body design.
...I'm pretty sure there are some good ones, properly forged, made in Australia. Not sure if they are '73-up or '72-down though.
Rick
Rick told me about this at Spring Fling 2000. And he said there was an ad for them in a mopar mag years ago. I have a pretty comprehensive Mopar mag collection and I just couldn't find it. I also asked OzHemi about it and he hadn't heard of it.
Any Austrailian guys out there know about this. I think a seperate topic on this Peter might bring out the Aussie mopar geeks.
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Re: Tall vs. Short Spindles
[Re: Digger]
#17867
11/01/05 01:48 AM
11/01/05 01:48 AM
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Joined: Jan 2003
Posts: 27,490
So Cal
autoxcuda
Too Many Posts
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Too Many Posts
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Posts: 27,490
So Cal
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Quote:
Here's a concise technical description of bump steer: www.racerpartswholesale.com/longtech3.htm It suggests that the upper ball joint position at least plays a minor role in bump steer. This link: www.bakerprecision.com/longacr17a.htm describes how to measure bump steer. It sounds like somebody needs to take the time to make the measurements to put this matter to rest.
Well like Rick said the measurements are right here in the table made by Bill Reily published in Mopar Muscle.
Quote:
Bumpsteer is caused by the tierod assembly moving in a different arc from the inner and out pivots of the LOWER CONTROL ARM. The height of the spindle will never change the relationship of the tie rod assembly to the lower control arm. In fact what bumpsteer that is inherent to the mopar front suspension is due to the torsion bars being where the inner tierod pivot should be.
That exactly what I was trying to say in an earlier reply but after Rick's reply I re-thought it and second guessed myself and edited out my comments. I think the end outcomes do effect bumpsteer in a round about way.
I think the effect comes from the camber curve changing as you said Thunderstruck. As the camber changes inward the tie rod pushes out the toe. This is when the tie rod is on a higher plane than the lower ball joint. Even though the tie rod and lower control arm are on the same arc, they almost always are not on the same plane.
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Re: Tall vs. Short Spindles
[Re: autoxcuda]
#17868
11/01/05 02:11 AM
11/01/05 02:11 AM
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Joined: Aug 2004
Posts: 3,310
Walnut Creek, CA
blown340
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master
Joined: Aug 2004
Posts: 3,310
Walnut Creek, CA
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Quote:
-SAE Mini Formula Design team suspension design and team leader for scratch built race car.
Hi there autoxcuda.. Well, I'm staying out of the conversation since my opinions are based on theory and I've never had a F body spindle on a car...
I just wanted to say though that its cool to see another Formula SAE alum on the board! I had the pleasure of working on 5 of the cars while I was in school and also was in charge of suspension design for 3 years. I also suffered the wrath of being the team captain for 3 of those years as well. 
-Jon
Last edited by blown340; 11/01/05 02:12 AM.
70 challenger convertible. 340/5 speed. blown, intercooled, efi, blah blah blah
71 valiant scamp 318/A833OD/AC/PS
00 dakota RC 4.7L 5 spd autoX'r. SRT10/T56 swap in process
73 W200 Power wagon, PTO winch, 4 spd
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Re: Tall vs. Short Spindles
[Re: blown340]
#17869
11/01/05 02:26 AM
11/01/05 02:26 AM
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Joined: Jan 2003
Posts: 27,490
So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,490
So Cal
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Quote:
Quote:
-SAE Mini Formula Design team suspension design and team leader for scratch built race car.
Hi there autoxcuda.. Well, I'm staying out of the conversation since my opinions are based on theory and I've never had a F body spindle on a car...
I just wanted to say though that its cool to see another Formula SAE alum on the board! I had the pleasure of working on 5 of the cars while I was in school and also was in charge of suspension design for 3 years. I also suffered the wrath of being the team captain for 3 of those years as well.
-Jon
Aw C'mon. Join in. What do you have to add??
Is that Okie State??
We had a pretty weak Formula SAE team. No class credits as in some schools and the glory hog Solar team got all the money.
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Re: Tall vs. Short Spindles
[Re: BergmanAutoCraft]
#17870
11/02/05 08:08 AM
11/02/05 08:08 AM
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Joined: Aug 2003
Posts: 2,474
Answering the call of the wild
ThermoQuad
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top fuel
Joined: Aug 2003
Posts: 2,474
Answering the call of the wild
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Here is a bump as I am hoping an engineering discussion will emerge from all of the hearsay, opinion and ego. Maybe you experts could discuss the data from the MM article a little deeper. Perhaps a real world study should take place where you took another test car and measured the bump steer/alignment angles differences between the changes. The final test would compare lap times and g forces thru the turns at say Watkins Glen. Until this is done the only real data we have is the one magazine article and a bunch of opinion. I am not asking for anyone to fall on their torsion bar [sword] but lets get to the facts.
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the opinions experessed are have thier points, BUT facts are facts, and I would like to know fact from opinion!