My caster mod (with pictures)

[highanglehell]

http://www.lateral-g.net/forums/showthread.php4?t=42467

Reading this we should be trying to get 9+ caster on our trucks

[chevyrestoguy]

Wow, 9+ is a bunch of caster. In my opinion, 7+ (max) is the sweet spot. We don't run huge tires on the front, we are limited to the old technology of our suspensions, and we aren't road racing. High caster numbers are not always a good thing. You start getting issues of increased steering effort at low speeds, and an irregular contact patch in corners when the suspension is under compression or extension.

[solidaxel]

With that much castor I wonder what it is like to back down the alley !!!

[BMERDOC]

Yeah, 9 degrees is a bit excessive. 6-7ish should be enough with upwards of 8 being max for a street truck. There is such a thing as too much of a good thing.

[Theboatandcarman]

Enjoying this thread. Doing alignments at my shop, European cars always have the most caster and have the best highway feel in my opinion! I'll have to do this with my truck to get a target of 6 degrees

[The Rocknrod]

I have my entire chassis apart for powder-coating. Finding this thread now is great. I'm going to work on this mod this morning.
With any luck I'll bugger it up enough to have to buy a whole new front end.
Edit:
I only had one locating hole 1-3/4" from one end not two. So I drilled another (opposite side) at 2-1/2". Removed the front lower A-Arm bracket and am heading to the store to get the allen bolt for the locating pin now. Looks like maybe I will have to trim about 1/4" off the rear side of the A-Arm to make it work though.
I removed the rivet on the front a-arm bracket only as there is no pin on the rear of mine. No doubler plates either. and it has 7/16" u-bolts. Will have to upgrade. The rivet hole is 7/16" so I'm good there.
Must be the older a-arm set-up is different, mine is a 64. Good thing I'm doing this, someone put this unit together and one a-arm shaft didn't have the locating pin in the hole and mushroomed the pin head some. It was about halfway in and out of the hole originally.
Update:
Have to go get Cobalt Drill Bit today. I have a smaller cobalt and it worked (I have a drill press). But not a 11/16".

[crakarjax]

I have a bunch of 5/8" masonry bits that can be used to drill these holes, I bought a lot of ten or something ... if anyone needs them I'll ship them out at cost + shipping ($7 I would guess)

[BMERDOC]

I just remembered a thread that was up a while back. Bumpsteer will happen in a stock situation but be aggravated once the Caster Mod has been performed. This is a great way to help alleviate the situation.

http://67-72chevytrucks.com/vboard/s...d.php?t=620584

[The Rocknrod]

Originally Posted by crakarjax

I have a bunch of 5/8" masonry bits that can be used to drill these holes, I bought a lot of ten or something ... if anyone needs them I'll ship them out at cost + shipping ($7 I would guess)

I'll buy a couple of those from you if you don't mind. I PM'd you also.

[The Rocknrod]

Originally Posted by BMERDOC

I just remembered a thread that was up a while back. Bumpsteer will happen in a stock situation but be aggravated once the Caster Mod has been performed. This is a great way to help alleviate the situation.

http://67-72chevytrucks.com/vboard/s...d.php?t=620584

Good info.

[The Rocknrod]

I bought a drill bit from these guys last Sunday - still not here...
http://www.ebay.com/itm/Drill-Hog-11...item27fd254772
But I was able to drill a pilot hole with a cobalt bit on my drill press using a 650 rpm setting and using dry lube. The slower speed really made a difference in the cut.
Mocking up the lower as-arm it looks like I will be doing the slight trim of my a-arm exactly like crakarjax did in his pics shown on page 5 of this thread.

[BMERDOC]

Just got mine back from the machine shop. I plan on doing some experimenting in my alignment thread soooo... Hopefully mine will be driveable again by Halloween so I can post the results.

[The Rocknrod]

Cool beans.
I drilled mine with the Super Cobalt bit I purchased. Put it together on the cross member and trimmed the a-arms as needed (not much). My current status is "on-hold". Been out of work - Put down, kicked around . . .

[SCOTI]

I originally drilled my lowers for this mod but ultimately switched to Porterbuilt lower arms for additional clearance w/the front bags. I drilled them to move the shaft .750" forward so the PB arms added .250" to that (1" forward lowers & factory uppers). I finally got my turn on my buddys machine & I'm pretty happy w/the results:

Left Right
-0.7 Camber -0.6
6.4° Caster 6.9°
.12° Toe .12°

Rear thrust angle was -0.12°

Not bad for a dually.

[BMERDOC]

Originally Posted by SCOTI

I originally drilled my lowers for this mod but ultimately switched to Porterbuilt lower arms for additional clearance w/the front bags. I drilled them to move the shaft .750" forward so the PB arms added to that (1" forward lowers & factory uppers). I finally got my turn on my buddys machine & I'm pretty happy w/the results:

Left Right
-0.7 Camber -0.6
6.4° Caster 6.9°
.12° Toe .12°

Rear thrust angle was -0.12°

Not bad for a dually.

Pretty good results but can I ask... .75" from what? There seems to be some discussion about the stock indexing location. Mine was at 1 7/32" so I just did holes at 2" and 2.25". Then again mine is non-bushed 67-72. I get a feeling that as much trucks hit the alignment rack we'll see varying results as the original index holes are not in the same spot all the time.

[SCOTI]

Originally Posted by BMERDOC

Pretty good results but can I ask... .75" from what? There seems to be some discussion about the stock indexing location. Mine was at 1 7/32" so I just did holes at 2" and 2.25". Then again mine is non-bushed 67-72. I get a feeling that as much trucks hit the alignment rack we'll see varying results as the original index holes are not in the same spot all the time.

I would have to measure the shafts again to give an accurate answer. They were new Moog shafts & I just drilled new holes .750" from where they were (this was before it came to light about the variations found).

That being said, the aligned set-up is the currently available Porterbuilt 1" forward lower a-arms so the lower BJ's are 1" forward of the OE location.

[chevyrestoguy]

Excellent caster numbers, Scoti!!

[BMERDOC]

Originally Posted by SCOTI

That being said, the aligned set-up is the currently available Porterbuilt 1" forward lower a-arms so the lower BJ's are 1" forward of the OE location.

I'm trying to gauge this before I hit the rack . Did you happen to print out your before and after sheet? Given input from guys who have done the mod it would seem that for every 1/4" the index is moved its worth about 1° of Caster. If your alignment was about 2.5 and 3.0 without shims before the alignment that would solidify my thinking. Not taking anything away from Rob because his track record is proven but I think we need to get away from the .75" measurement and start measuring from the end of the shaft. Anyone who has pre-mod (non-shimmed) specs could redrill their shafts to have equal caster once it hits the rack.

[picklito]

Originally Posted by BMERDOC

I'm trying to gauge this before I hit the rack . Did you happen to print out your before and after sheet? Given input from guys who have done the mod it would seem that for every 1/4" the index is moved its worth about 1° of Caster. If your alignment was about 2.5 and 3.0 without shims before the alignment that would solidify my thinking. Not taking anything away from Rob because his track record is proven but I think we need to get away from the .75" measurement and start measuring from the end of the shaft. Anyone who has pre-mod (non-shimmed) specs could redrill their shafts to have equal caster once it hits the rack.

Could not agree more. Reading back through our "progress" I think we did not appreciate how many different places our lower cross shafts could be starting from. I'm gonna talk to my alignment shop and see if they can give me a starting caster, then mod to try to hit 7 degrees.

Also - we are mostly trying to do this by moving the shafts. Now, I'm not a good metal guy (yet... I hope) but the guys I know who are, and who do it for a living, tell me that an appropriate form of cutting/patching/welding on the LCA to move the ball joint forward is very safe IF the guy knows what he's doing. I've only seen a few of our better fabricators doing this on this forum. What do you guys think about this?

[SCOTI]

I did get before & after..... But, while I'm not a 'pro', I directed my alignment guys & explained 'why' as we went along. I had already dialed in my stuff in the parking lot of my joint.

We started off @
-1.4/-1.7 camber
8.X/9.X caster &
didn't even look @ the toe.

They were freaking out how far from "spec" I was. But we got it dialed back to what I wanted pretty quickly.

[BMERDOC]

It would seem that this has turned into a lot of research but I think the answers will be worth it. Any guy on a budget will be able to modify the stock stuff and make vast improvements on how his/her truck performs.
FWIW, my progress is slow but I work and research (watching everyone here) to figure this out. 1/4" of movement for 1° of caster is fuzzy numbers at this point but lets step that up one notch. If 1/4" is worth 1° on the bottom why not machine the uppers 1/8th" to have the extra .5" movement to equalize caster on both sides? Again, all research and little to no development at this point but I'm thinking. You would only end up shimming to equalize camber at that point. Then again you could machine the uppers down to equalize camber. Certainly, there is a time when all that machine work adds up and it may be worth it to pay the money for tubulars but then you are still at the mercy of the guy manning the alignment rack.

[BMERDOC]

Originally Posted by SCOTI

I did get before & after..... But, while I'm not a 'pro', I directed my alignment guys & explained 'why' as we went along. I had already dialed in my stuff in the parking lot of my joint.

We started off @
-1.4/-1.7 camber
8.X/9.X caster &
didn't even look @ the toe.

They were freaking out how far from "spec" I was. But we got it dialed back to what I wanted pretty quickly.

Wow! Can you snag a shot of your shimming for us? I'd expect any alignment guy to lose his mind over those specs but we are experimenting here. ��

[SCOTI]

Originally Posted by BMERDOC

Wow! Can you snag a shot of your shimming for us? I'd expect any alignment guy to lose his mind over those specs but we are experimenting here. ��

I can't do a pic but I know what was in there. I had 2x 1/8" shims in the front (each side) & 1x 1/8" shims @ the rear (again, each side). As expected, I was off (excessive).

[BMERDOC]

Thanks Scoti!! You have provided me with a wealth of info. Given your before and after numbers along with the shims installed I have almost too much info to process. Now if this was my only job. From now on thats how I want everyone to report their results! Ha! I know your truck is a dually but its not far from getting us where we need to be. Soon enough we'll be talking about relocating tie rods and sectioning crossmembers and the lower crossshaft thing will be a non-issue because we'll have that part sorted. Between the math and the real world results its almost a done deal. If you can get your stock index numbers that would be great, if not then its no big deal. I have a feeling 67-72 guys will end up at different numbers than the 73-87 guys. Itd be great to get this down to 1/8" but frame and crossmember differences will be the end result. Someone will end up with a graph (probably not me) that charts this whole thing out and everyone will have the recipe to get their truck done right.

[picklito]

Originally Posted by BMERDOC

If 1/4" is worth 1° on the bottom why not machine the uppers 1/8th" to have the extra .5" movement to equalize caster on both sides?

Not sure I'm following this. 1/8" (where?) equals .5"(where?).

Uppers back is a good idea, too. Before I found these threads I was only thinking of lowers forward cuz I also wanted to move the wheel forward in the well, mainly for cosmetics. Obviously, uppers back would negate a little of this, but I'd take 6 degrees over a perfectly centered wheel!