Magnumforce 2" drop spindles, 11.75" rotors installed!

[72bluNblu]

These are the rotors I bought

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220328885601&sspagename=STRK%3AMEWNX%3AIT&viewitem=#ht_7800wt_1448

Just drilled and slotted Cordoba rotors. A little fancier than stock, but nothing all that special. I bought my caliper brackets for $85 from a guy on A-bodies. 

Actually, the braking area for the 11.75" rotors is bigger...

If you figure the outside of the rotor is 11.75" and the width of the braking surface is 1.8" ( I measured it),

then the total braking area is  π (11.75/2)^2 - π(9.95/2)^2 = 30.67 square inches for the 11.75" rotors

For the 10.98 rotors the braking area is π(10.98/2)^2 - π(9.18/2)^2 = 28.5 square inches

The pad is the same size, but because the outer diameter is larger, so is the circumference of the rotor. So at any given moment the pad area in contact with the rotor is the same, but the pad "sweeps out" a larger area on the rotor because it travels a longer distance in doing so. This doesn't directly improve braking force, but because the pad is acting over a larger area the brakes are dispersing the energy of braking over a larger area. Also, there is more surface area to disperse the heat energy once the braking is done.

Long story short, the larger rotors will heat up slower than the smaller ones. They would also cool down faster if they had the same mass as the smaller rotor. I'm guessing that even with the drilling and slotting they still weigh more, so its a toss up if the greater surface area wins out over the greater mass in cooling the brakes. And I really don't feel like pulling out my thermodynamics book to figure it out  , or pulling my 11.75" disks to weigh them.

As HP2 mentioned, the braking force itself is only greater because of the greater leverage, but thats a direct multiplier in the force equation, so a little leverage distance makes a big difference. I can feel the braking difference with the new rotors. 

[Super Blue 72]

   Great info!



Thanks for the info guys!   

[72bluNblu]

Finally got my car aligned last weekend, took a few trips to get the adjustable UCA's set up right. Currently the car is set up with -.7* camber, +4.0 caster, and 1/16" of toe in. I managed to find a Les Scwhab with an alignment guy willing to set the car up to non-1972 specs, and he was very helpful in helping me set up the UCA's. They put in a lot of work on my car without going to an hourly rate on me. If you're in the greater Sacramento area and need an alignment or anything similar I can refer you over to them! 

[HP2]

So tell us, do you like the way it feels now?

[72bluNblu]

So tell us, do you like the way it feels now?

Definitely! 

I had some significant cross caster issues prior to my alignment that caused a pretty good "pull" to the left which caused some problems figuring out how the car really handled. The suspension obviously didn't change, but the steering certainly biased some things.

The car handles very well, MUCH better than before the suspension work. The 1.12" bars are about perfect for me, they're definitely stiff, but not punishing on the street (for me anyway). Even with just the 1.12" bars and XHD rear springs the body roll has been substantially reduced, though I still plan on getting sway bars for it to improve things some more. I may have to think about the size of the sway bars though, I don't know that I really need to use the biggest ones I can get. The braking with the 11.75" rotors is much improved as I mentioned earlier, the front/rear bias is much better. I can brake harder and stop shorter than before without locking 'em up.

I'm still a little disappointed with the steering. Although the alignment helped with the steering feel I really don't think I'm going to be happy until I get rid of the stock power steering. I'm sure that some of the aftermarket power steering boxes would improve this, but I've got a manual box and a new 20:1 gear to put in it to replace the stock power stuff. I'm thinking that will help a lot with road feel and feedback.

Finally, I still need to tie the frames together with some connectors to stiffen things up in the chassis. Even though I'm basing these observations on some aggressive street driving out on some remote mountain roads its pretty obvious now that chassis flex is coming into play with the handling with the upgraded suspension parts.

Overall though its a HUGE difference over stock. The car is much more predictable, although I would say (without having drifted it) that it feels like its still in understeer mode, although much more balanced than before. I'm really happy with it. New tires, frame connectors, sway bars, and a manual steering box are still on my list though to really get things dialed in. 

[autoxcuda]

So, you coming down to Buttonwillow for the Spring Fling Speed Festival this Thrusday??

It's now setup pretty decent for that.

[HP2]

Yes, if you don't have any chassis bracing, now is the time to add it.

What can you say about the stock Mopar power steering other then blech! The swap toa manual box will yield big dividends in feel.

I don't recall what size sway bar you have up front, but if you go bigger, it will make the understeer worse. With your current set up, you may need to add a rear bar to take the understeer out. Despite their radically different sizes, the stock style .75 and the Hellwig 1.0 size rear bars are both pretty close in applied rate with the stock bar being slightly less. I think the difference is something like 10# of force. But, that also could change with the swap from power to manual steering and the subsequent loss of weight off the nose.

Chassis balance is one of those things that include so many variables and can be achieved in so many different ways, that it becomes personalized to the vehicle and a simple change like swapping out a steering box or bumper can cause need to recalculate. It can get crazy quickly.

[drewcrane]

It can get crazy quickly,aint that the truth, like a can of worms,  also be careful with the "break in " of those rotors dont glaze them,sounds like those drop spindles are nice,how is your oil pan clearence? how many inches to the ground?i would like to know that.

[72bluNblu]

So, you coming down to Buttonwillow for the Spring Fling Speed Festival this Thrusday??

It's now setup pretty decent for that.

I wish! Hopefully next year. I'm racing just to get enough done to feel comfortable driving it to Van Nuys, longest trip its done so far is about two hours. I wanted to have the 340/4 speed OD in it by now, but I dragged my heels on the engine so I'm not done with that yet. Hopefully by Fall Fling...

Yes, if you don't have any chassis bracing, now is the time to add it.

What can you say about the stock Mopar power steering other then blech! The swap toa manual box will yield big dividends in feel.

I don't recall what size sway bar you have up front, but if you go bigger, it will make the understeer worse. With your current set up, you may need to add a rear bar to take the understeer out. Despite their radically different sizes, the stock style .75 and the Hellwig 1.0 size rear bars are both pretty close in applied rate with the stock bar being slightly less. I think the difference is something like 10# of force. But, that also could change with the swap from power to manual steering and the subsequent loss of weight off the nose.

Chassis balance is one of those things that include so many variables and can be achieved in so many different ways, that it becomes personalized to the vehicle and a simple change like swapping out a steering box or bumper can cause need to recalculate. It can get crazy quickly.

Right now I don't have any sway bars on it at all, as it didn't come with any from the factory. Whatever I do in the front I'll have to go bigger in the rear. I've thought about just putting a stock front bar on it and then going with an aftermarket rear, I know I can pick up a stock front pretty cheap so it wouldn't be a big deal if it turned out to be too small. Although I could just get stock front and rears and see what happens, if the stock rear is that close to the Hellwig.

I'm going to wait on the rest of the suspension tuning though until I do the 340/4 speed OD swap. I'm ditching the factory AC and power steering with that swap, plus going to an aluminum intake, so I'm losing a significant amount of weight off the nose. Not sure what the weight difference is on the aluminum case 4 speed OD vs the 904 thats in it now. I'd be willing to bet the 308 heads on the 340 will be a little lighter than the originals too even though they're still cast.

I was wondering about the frame connectors though, I'm torn on whether to just make my own through the floor connectors or go with the mopar bolt ins and just weld them. I don't think I'm going to do the fitted type that welds to the floor just because I think that'd be a whole ton of welding to do upside down, I don't have a lift or anything. I thought I saw somewhere though that the type of frame connectors affects what class you end up in for racing/autocross, although I'm not sure it will matter with the tubular UCA's/LCA's already.

It can get crazy quickly,aint that the truth, like a can of worms,  also be careful with the "break in " of those rotors dont glaze them,sounds like those drop spindles are nice,how is your oil pan clearence? how many inches to the ground?i would like to know that.

The drop spindles are awesome, real craftsmanship on those. I'd run them just because of how much stronger they look than the stockers. Oil pan clearance is fine, the Hooker Super Comps are by far the lowest point on the car. At the moment I can barely get a standard floor jack under the K member, and the headers are about 3.5" off the ground. Haven't measured to the oil pan just because the headers were my concern, the oil pan is several inches higher. Although when the 340 goes in with the Kevko pan it may be more of an issue, but the headers will still be lower.

[boydsdodge]

A summer later, how is the front end drop spindles doing?

[72bluNblu]

Everything is working great, I know I've put at least 4000 miles on them since they've been installed, probably more like 4,500. Brakes, torsion bars, and even my CAP upper and lower control arms are working as well as when I put them on. I did manage to dent one of my Hooker Super Comps on a speed bump though  . I guess that does go to show how low the front of the car really is. Next up though is a B body rear with 11" rear drums, when I go to that I'll be installing SS springs with a relocation kit in the rear. I haven't been as happy with the XHD's as I have been with the front suspension (too much sag!), with any luck the SS's with raise the rear a little, and I may raise the nose a touch when they go in. This will keep the car raked a little but should give me a little more wiggle room on the headers. Not ideal for corners, but a little reality for a daily driver. I have the dual position rear spring brackets, so I can lower it a little if the SS's give too much lift.

[boydsdodge]

leave the springs in and get a set of TTIs. well worth the cost, I found thenm easier to deal with then iron.

[Czar of Mopar]

Hi there. Been reading your threads and decided to order a couple of sets of those drop spindles No problems . However. That site you recommended  for the Cordoba rotors and caliper brackets has been removed. Can purchase the rotors no worries but can"t seem to come up with the caliper brackets.  Any idea's Thanks TJ

[boydsdodge]

Id say your going to have to do some wrecking yard hunts.

[brads70]

Hi there. Been reading your threads and decided to order a couple of sets of those drop spindles No problems . However. That site you recommended  for the Cordoba rotors and caliper brackets has been removed. Can purchase the rotors no worries but can"t seem to come up with the caliper brackets.  Any idea's Thanks TJ

Make a new post in parts wanted. Someone will have a set of know where to get a set. Did you look on e-bay? That's were I got mine.