"jlmounce" (jlmounce)
10/02/2014 at 13:13 • Filed to: Firebird
3
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"jlmounce" (jlmounce)
10/02/2014 at 13:13 • Filed to: Firebird | 3
| 10 |
Looks like I'll be busy this weekend! Summit Racing shipped me out some tall upper ball joints and a disc/disc proportioning valve for my 1969 Firebird.
It's widely understood that the first generation F-Body front suspension leaves much to be desired. While it's basic design of a short/long arm independent control arms gives a good foundation to work with, packaging saddled it with poor caster, a spindle that is too short and over an inch of bump steer across 5-6 inches of suspension travel.
One of the largest problems with the front is negative camber gain. Or really the fact that there isn't any. In bump, the suspension actually exhibits close to 2" of positive camber gain in some cars. This is primarily the result of the short spindle. These tall upper ball joints not only provide freer movement than the factory pieces, but also increase the effective spindle height by half an inch. It does not resolve the negative camber gain issue, but it does reduce it a bit.
With these joints I'll also be able to get my Hotchkis 2" drop springs installed at the same time. This will change my lower control arm angles opposed to the steering arm locations and I'm hoping to see a reduction in bump steer. If not I can look at tall tie-rod ends to compensate there. These are just two small items that again does not solve the poor geometry of the 67-69 F-body front suspension, but should make for a bit more sure-footed drive.
Around the beginning of next year, I'll be gutting all of this in favor of RideTech components. Specifically, their strong arms, coil-overs, tall spindles and tru-turn steering setup. This front suspension packages allows caster beyond the 5 degrees possible with the factory arms, reduces bump steer to 50 thousands over 6" of travel, improves negative camber gain to the tune of about -2.5 degrees at bump, and relocates the ball joints to better angles for lowered ride height.
What about that proportioning valve you might ask? Well, I've installed disc brakes at all four corners of the car. What I have not yet done however is change out the factory combination valve. Disc brakes require more volume and line pressure then drum which are self actuated. As a result, the factory valve on my car is castrating my brakes in a manor that's not really safe. This disc/disc valve will give me more volume and pressure at the calipers, improving brake performance and feel.
So that's it! Getting closer with this car every weekend! I'm hoping to have a plated, insured, roadworthy auto within about a month and a half now. Just in time for it to stay in the garage and away from the snow!
CalzoneGolem
> jlmounce
10/02/2014 at 13:20 |
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For the drugs.
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jlmounce
> CalzoneGolem
10/02/2014 at 13:21 |
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haha, actually for candles! I like to have something burning while I work!
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CalzoneGolem
> jlmounce
10/02/2014 at 13:22 |
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I like to have something burning while I work!
That's what I was saying!
crowmolly
> jlmounce
10/02/2014 at 14:58 |
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Are you doing the Gmod as well?
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jlmounce
> crowmolly
10/02/2014 at 15:03 |
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If I was planning to stick with the factory control arms, I would be. However my plans include going to the ride tech strong arms which should be mounted in the factory mounts. I'll be utilizing their tall spindles to correct negative camber gain issues.
Since you have to trim off the top of the mount to get the factory upper arms to clear, I've decided to forgo that modification.
However my research seems to point to a half in tall UBJ along side the G-Mod is highly effective if you're doing some decent corner carving. It doesn't really do much for bumpsteer though. A tall tie-rod end would probably help though.
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crowmolly
> jlmounce
10/02/2014 at 15:34 |
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Yeah, I've got all DSE stuff and that works with and without the Gmod. Left the original holes just in case it was wonky and it appears to be better with the G.
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jlmounce
> crowmolly
10/02/2014 at 15:39 |
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are you running a tall spindle?
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crowmolly
> jlmounce
10/02/2014 at 15:46 |
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No. Back when I built it there wasn't too much information out there yet and Hotchkis, DSE, and GW all said don't use a tall spindle or tall joint with the Gmod.
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jlmounce
> crowmolly
10/02/2014 at 16:14 |
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That's still the majority of consensus. You "can" run both a tall spindle and the G-Mod, but you end up with a LOT of negative camber gain. Like close to 5 degrees at full compression. If it's a race car, that may actually work to your advantage. On the street though with street tires, you'll be off the contact patch in the opposite direction and probably have a car that pushes fairly badly.
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crowmolly
> jlmounce
10/02/2014 at 16:17 |
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Yeah, right now I have it pretty much where I want it, but I need new wheels and tires and a performance alignment.
Did you replace your sway bar yet? That made a huge difference in my case.