Moparts Tech Archive

Front Suspension

Tubular K-Member

Looking for feedback on the Magnum Force Tubular K-Member and rack steering.
Any problems?

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dbdartman
Moderator
Posts: 3505
From: Trenton, NJ
Registered: Nov 1999
posted 10-03-2002 08:12 PM

From what I've seen, they look good for drag racing, but I wouldn't use Magnum Force on the street. www.bigblockdart.com makes a VERY nice front steer R&P coilover conversion that IS street friendly. I've also seem someone that's making tubular K-frame that accepts stock parts (check the parts pages).

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ragtopdodge
Moparts Member
Posts: 1192
From: Des Moines, WA, US
Registered: Sep 2000
posted 10-03-2002 08:31 PM

The bigblockdart.com conversion is only a-body at the moment, but I'm trying to twist Bill's arm into building a b/e-body unit.
Magnum's doesn't have:

-provisions for motor mounts (i.e. kiss good bye to PS w/motor plates)
-provisions for sway bars
-reliance on the inner fenderwells to provide support for the car. I.e. look forward to them cracking.

Bill's system, from what I understand, will take care of all of the above, so it'll be street friendly.

The OTHER k-member setup found in Classifieds has issues and is more drag-oriented like the Magnum setup:

-no provisions for motor mounts (i.e. kiss good bye to PS w/motor plates)

-no provisions for sway bars

B/C it uses the stock suspension setup (torsion bars), that has its pluses and minuses.

+ Save money on expensive a-arms, coilover shocks.

- Torsion bars still can get in the way if you plan on running big headers say..on an a-body.

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340-4
Moparts Member
Posts: 718
From: Elyria, Ohio
Registered: Apr 2001
posted 10-03-2002 08:39 PM

I looked at those front coil over conversions too but thought the same thing about all that weight on the shock towers. If it didn't crack the towers I know they would bend inwards from all the flex.
Eric

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kekoakeakane
Moparts Member
Posts: 1006
From: Honolulu, HI USA
Registered: Jun 2001
posted 10-04-2002 04:03 AM

As far as the weight on the shock towers from the Magnum Force setup, you're supposed to reinforce them by welding gussets to the frame. It's diagramed on the website.

kekoakeakane

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AC
Moparts Member
Posts: 1700
From: Escalon, Ca. USA
Registered: May 2001
posted 10-04-2002 04:06 AM

The geometry is setup for drag racing. The intent is for the wheels to go straight for 1/4 mile passes. If you turn and let go it will snap back to center quick.
AC

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jfsram
Moparts Member
Posts: 904
From: Hamilton, Ontario, Canada
Registered: Jul 2001
posted 10-04-2002 05:27 AM

AC, that's from positive caster. Once you try it you will never go back.

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migsBIG
Moparts Member
Posts: 472
From: San Jose,CA
Registered: Mar 2002
posted 10-04-2002 05:34 AM

If you are intending on building a race/limited street car, that would be the package for you. ron jenkins of Magnum force is a Mopar guy, through and true. He is currently under development on building Viper suspension components to fit the earlier MOPARS!
If your looking for a street setup for regular use, call them up and ask if they should have one of there rack and pinion conversions kits to rework your stock k-member.

By the way, what kind of car are you building, and the use you are planning to do with it? We could answer you answers more info when we have all the facts!

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MoparTony
Moparts Member
Posts: 1925
From: Detroit area
Registered: Jul 2000
posted 10-04-2002 07:35 AM

I have checked into all 3. Magnum is good but too much money for just a K-member then you have to buy all the other parts.
Bill's is great for the street, but if you get the front in the air, you may have some problems with bump steer. Last I heard this was an issue.

The other one from Dave something, uses all the stock stuff and like the magnum piece has no bump steer issues. In talking with Dave at Norwalk he said he would/can gusset the longer arm of the K member if you wanted. Also there are no special parts to Daves unless you go rack style then the only part that is not stock. Also it is made of chrome-moly and comes with all the hardware.

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jughed
Moparts Member
Posts: 798
From: Illinois
Registered: Apr 2001
posted 10-04-2002 12:46 PM

You guys gotta check this out. http://dareracing.com/kmember.html
I am getting one.
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River
Moparts Member
Posts: 230
From: white haven, pa, usa
Registered: Dec 1999
posted 10-04-2002 06:11 PM

The AlterKtion never had bumpsteer issues. The early problem I had was the cheapy lower a-arms I tried weren't strong enough to handle a wheelstand. That was corrected long ago, soon to be REALLY perfected.
This is REALLY long, but I hope you'll find it helpful.
I obviously have my own opinions about the other ones out there, so I'll just tell you what to ask about and you can call them and form your own opinions.
You also should ask yourself why you want it. Weight? Handling? Clearance? All these systems are quite a few bucks...keep in mind you want the most gain from a given dollar spent, with the least amount of effort. Is some clearance alone worth $1000? Is maximum weight savings alone worth $4000? If you can't honestly justify it's cost/benefits, keep the stock stuff - you'll be happier.
Drag cars get worked on more, and are more forgiving of things, but a street car system should have ALL of the below items...

CAMBER - at ride height, you should have enough adjustment for -1 degrees to +1 degrees MINIMUM, to compensate for Chrysler's manufacturing. Otherwise, you may have to use offset bushings to get alignment right.
CASTER - lots of caster is fun if you're a driving enthusiast(I have 8 degrees on my own car) but it's a 2-handed drive on curves. That much steering effort may not be desirable for the average guy on an average cruise. Make sure you can adjust caster down to 1 or 2 degrees as well, for more of a relaxed, but stable ride.

BUMPSTEER - of course should be close to zero..true zero is unattainable due to the elliptical travel of the spindle and the circular travel of a tie rod - roughly, each wheel should not toe-in more than 3/32" over its full course of travel. That's about 0.4 degree with a 24-26" tall tire, or roughly .135 degrees per inch of travel. Less is better, but it's ok to have SOME toe-in. Indy cars only allow 0.100 degree per inch of wheel travel - but we dont have Indy cars. Some circle burners actually design toe change in, to help with corners, so they dont count at all. If theres any toe-out, hang up the phone.

ACKERMAN - Inside wheel should turn more than the outside one because they make different size circles when turning. OEM cars are checked by turning the inside wheel 20 degrees and checking the outside one. Mopars have a 2.5 degree difference, or 17.5 degrees for the outside wheel. The actual measurement isnt really important, as long there IS some, even 1 degree would be ok. But if the outside wheel turns more than the inside, you're in for a scare. If it's bad enough, a sharp turn off of main street will cause the wheel to rip right out of your hand and go to full lock. If you're not expecting that, it can be quite dangerous - and once you do expect it, it's pretty aggravating. Ackerman is definitely important!

ROLL CENTER HEIGHT - the lower the better, but be sure to ask, because the lower it goes, you'll need either a sway bar or pretty stiff springs to control body roll. A stiff ride is no fun on bumpy roads. Average A-body RC is (more or less) 7" high, depending on ride height adjustment. If it's a couple inches lower than this, expect some added body roll - Altered pivot points affect this but the other systems all use stock pivot points, so this statement is fairly accurate.

TURNING RADIUS - this is kind of personal opinion, but it should be less than 20 feet. A u-turn with a 20' radius requires 3 full lanes. In tight intersections, a larger turning radius would be tough to manuever. Kinda like a full-size Ram in a 10 foot back alley.

KING PIN ANGLE - some systems have fab'd spindles so you should be sure, for the sake of good stability, that the angle is at least that of the stock mopar, which is 7.5 degrees. More is better, less is not. More king pin angle also requires less caster for a good feel.

These are the items that matter most. Be sure to get solid answers for each question. For instance, "theres no bumpsteer at all" is a stupid answer. Ask for the actual numbers AT THE LIMIT OF TRAVEL . If a shop can't give you these numbers, they shouldn't be messing with suspension- or they're hiding something - if theirs is better than stock, they should be able to prove it. If they say "you dont really need to worry about that measurement", tell them you're not worried, and hang up the phone. Every measurement listed above has a direct impact on the behavior of your car.

Also keep in mind you'll need elephant ears with most of them, power steering is forgotten and sway bars would be a home fab job with most others. One other warning - rods ends are not permanent weather-proof items. They also tend to stretch over time and abuse, so they should be checked now and then, and it's recommended they be replaced every year or so, depending how often the car was used. Also be aware fabricating is necessary with some systems.
The above info was gleaned from racers, autoX'ers, custom guys, circle track racers, my own expeeriences, and 3 years of intense research. These generalizations can be reliably used for basic guidelines. If the system fits in these rules, you shouldn't have any troubles.
Changing front suspension is a big deal, effecting your car's behavior in every situation..do a little homework before spending the money and you'll be a happier guy for it.
Hope this helps.

Bill ReillyWWW.BIGBLOCKDART.COM
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ragtopdodge
Moparts Member
Posts: 1192
From: Des Moines, WA, US
Registered: Sep 2000
posted 10-04-2002 06:43 PM

Thanks for the info Bill!
Definitely food for thought before jumping into a product head first.

BTW, when's your a-body Alter-K going to full production? Hope they fly off the shelves to fund b/e-body R&D.
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JERICOGTX
Moparts Member
Posts: 2357
From: MN, USA
Registered: Apr 2001
posted 10-04-2002 06:55 PM

MoparTony, have you seen Dave's K member up close? How is the quality? Does anyone have one from him?
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River
Moparts Member
Posts: 230
From: white haven, pa, usa
Registered: Dec 1999
posted 10-04-2002 07:01 PM

It'll be soon Ragtop. I working on some final items now, better a-arms, nicer shock mounts. Believe me, after 2 years of work, I'll have them available as soon as possible
Jerico, I haven't seen Daves K up close, but I traded many emails with him...even without seeing his work, I'd still trust it.

Bill ReillyWWW.BIGBLOCKDART.COM
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451boy
Moparts Member
Posts: 5066
From: Oregon
Registered: Nov 1999
posted 10-04-2002 07:16 PM

Bill,
Your system looks pretty good. What kind of brakes are available for the Mustang II knuckles? Does Baer (or someone else) have some big 13 inch rotors for those of us who like to stop?
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ragtopdodge
Moparts Member
Posts: 1192
From: Des Moines, WA, US
Registered: Sep 2000
posted 10-04-2002 08:40 PM

According to Baer's website:
http://www.baer.com/catalog/racer_20_web.pdf
(scroll down to Street Rod)

The sky's the limit for Mustang II.

I.e.

You can get the Extreme + Alcon brake setup with...optional 15" ROTORS!

http://www.baer.com/products/extreme.shtm

Can someone besides me nag Bill to make his alter-k for b/e-bodies? No offense to a-body owners, but I think I'm somewhat accurate that especially e-body owners, we plunk down a lot of cash on our cars (foolishly I must admit) and his setup will definitely sell w/that crowd.
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ragtopdodge
Moparts Member
Posts: 1192
From: Des Moines, WA, US
Registered: Sep 2000
posted 10-04-2002 08:55 PM

Hey Bill, what's the deal w/Baer's rod links:
http://www.baer.com/options/STEERING.SHTM

Of any value?
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DemonEric
New Member
Posts: 9
From:
Registered: Aug 2002
posted 10-04-2002 09:07 PM

I guess I'll add my two cents. I'm currently in the process of dropping a year's salary on turning my Demon into an all out road racing machine. I've looked into pretty much everything possible as far as front suspension.
I must admit that at first Dave's kit from dareracing.com was my choice. I questioned him about it and found two major problems. First, I feel the rigidity is questionable. My own personal opinion is that it just isn't as strong as a stock K. It should be okay for a track only dragster. Secondly, he uses a Pinto rack and pinion (Front Steer) with the stock Mopar spindles (Rear steer). The ackerman on this system will most likely be completely hosed. You may save some money over the other systems for your all out dragster, but in my opinion it's not worth risking your life.

The Magnumforce unit just doesn't do it for me either. On paper it should work, but it seemed too much of a hassle for me. Motor plates + reinforcing the shock towers + outrageous pricing = not worth it. It would be nice for them to post some of the ackerman, bump steer, caster, camber, etc of this system as well.

Now Bill's Alter-K-tion unit from bigblockdart.com interested me right off the bat. He had all the crucial caster, camber, bump steer, etc specs listed on his page. No welding required, no re-enforcing the shock mounts, no motor plates. Add this to reasonable cost and we have ourselves a winner. I'm very picky with my money and the only downfall I could find was the lack of camber needed for road racing. He has since fixed that with an optional drop spindle. When the time comes I will be writing Bill a check with a smile on my face.

Eric Limbeck
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River
Moparts Member
Posts: 230
From: white haven, pa, usa
Registered: Dec 1999
posted 10-05-2002 12:16 AM

Looks like Baer has quite a selection of rod end kits there. I'm using a similar arrangement, but only because of having to fab the steering arms to have a strong attachment. The idea of "bumpsteer adjustment" in these kits is actually misleading. You can't adjust it out. You can only move the given bumpsteer one way or the other. By changing the height of the outer tie rod end, you put the tie rod at a different point in its arc. Looking from the front, the tie rod gets shorter and longer as it moves up and down. When it's level, it's the longest, and gets shorter when it moves in either direction. By changing the height, it'll be further through that arc, so the wheel will begin to toe in sooner in one direction and later in the other direction. Adjusting this way would be good for say a drag car that runs with the nose up...you could adjust the height of the tie rod end so the wheels maintain the toe setting at full extension, but toe-in alot in dive...but since the drag car is almost never in a dive situation, it's a better setting in that instance. An AutoX car would be set the opposite way for cornering. Small adjustments usually make a large difference.
And you're right Tony. My main goal was a killer street setup. From there, I changed or adjusted some things to make it more strip friendly. Just like the rest of the car, I doubt I'll ever stop messing with it.

You don't happen to have the #1835 AFCOs do ya?

Jerico, I'm not sure how Dave attaches his, if he makes a few parts for it or not. Swapping the stock lower balljoints changes Ackerman to the exact opposite, causing the situation explained above. In a strip car, you'd never notice this problem. Again, Street use is a whole new set of rules. Notice the Magnum and AJE systems have fab'ed lower balljoints and/or spindles...it was easier for them to solve some problems that way.
Bill ReillyWWW.BIGBLOCKDART.COM
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gtxmonte
Moparts Member
Posts: 1685
From: Trinity, AL. USA
Registered: Oct 2000
posted 10-05-2002 12:43 AM
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When swapping the lower joints side for side, you do get into ackerman problems as Bill says. What I normally do is cut the stock steering arm off the lower joint and build my own, or modify the spindle to use a upper type screw in joint in the bottom also. While some may cringe at welding on stock spindles or balljoints, if you know what you are doing, you will not have a problem.
Bill have not talked to you in a while, I see you got your bumpsteer issues worked out. The kit looks nice.

Monte Smith
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River
Moparts Member
Posts: 230
From: white haven, pa, usa
Registered: Dec 1999
posted 10-05-2002 02:16 PM
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Hey Monte. Yes, it HAS been a while. Making my own steering arm solved alot of the original problems. I did my best to be able to use stock spindles and tie rod ends, but it just wasn't possible.
I have Flaming River's catalog, and they offer the Billet steel u-joints, Aluminum alloy joints and the pin/block type. I think I'm going to use the alum alloy ones...they're about the same price and strength of the steel joints and half the weight. If I can lose weight without any sacrifices, I'd be stupid not to. The pin/block joints are pretty weak(under 300lb-ft), and big guys can actually break them under a panic situation. I have some, but I wont use them on the street.

I'd love to build a strut car - just don't have the beans to do so right now. I'd also love to build a full chassis Dart with a no-compromise AutoX approach - for the street of course. A Viper killer if you will. It could easily be done, just takes bucks.

If you can afford/build a full strut nose, it has the most benefits in a fast car. Slower/limited tire size cars would gain more by staying with a-arms, as theres more travel, aiding weight transfer.

I noticed DemonEric mentioned cambergain - I should clear up something on that. For the bolt-on approach, camber gain is only 1.38 degrees in 2.5" with stock a-body. AlterK is just 1.45 degrees for the same travel. not much better. Theres a spindle extender available that raises the upper balljoint 1.9375". Using this part REALLY adds serious camber gain...an excellent part for sure. However, I found out that with deep wheels, there isnt enough room to raise the BJ that much - it'll hit the rim. So, if I use 2" drop spindles, along with the spindle extenders, I get massive camber gain, along with good wheel clearance. Dropped spindles and the extender adds about $260 to the cost, but the improved geometry is up there with pro cars. Even I'm amazed I could get a bolt-on system to have the geometry of a custom chassis. The only question to it all at this point, is that some classes require stock stuff, so using this would put you in a different class or take a penalty. If you have to run with chassis cars, weight or chassis stiffness may become an issue - I dont know yet if the benefits would outweigh the shortcomings of competing against chassis cars with a unibody, or taking a penalty in a stock class. I have spoken to guys that have improved lap times by raising the upper joint just 3/8"...if camber gain was good enough to keep the tire flat on the road, as this system would do, it might still run faster even with a weight penalty. That's only conjecture though...we won't know for sure until it actually sees a road course. All this stuff applies somewhat to stock suspension as well. If it's possible to make similar changes to the stock Mopar stuff, similar gains are possible - there would be alot of welding and fitting, and using jigs to hold meaurements perfect. Definitely not a weekend project.

Bill ReillyWWW.BIGBLOCKDART.COM
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