Moparts Tech Archive
Tubular K-MemberEdward Sakevich
From: Barnegat N.J U.S.A
Registered: Jul 2002
posted 10-03-2002 07:45 PM
Looking for feedback on the Magnum Force Tubular K-Member and rack steering.
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).
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.
-provisions for motor mounts (i.e. kiss good bye to PS w/motor plates)
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
+ 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.
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.
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.
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, that's from positive caster. Once you try it you will never go back.
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!
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!
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.
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.
You guys gotta check this out. http://dareracing.com/kmember.html
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.
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.
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.
Thanks for the info Bill!
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.
MoparTony, have you seen Dave's K member up close? How is the quality? Does anyone have one from him?
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
According to Baer's website:
The sky's the limit for Mustang II.
You can get the Extreme + Alcon brake setup with...optional 15" ROTORS!
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.
Hey Bill, what's the deal w/Baer's rod links:
Of any value?
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.
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.
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.
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.
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.