My caster mod (with pictures)
On Rob's Make It Handle thread, he mentioned that if he were to ever do a mod to increase caster, he would move the lower arm forward and the upper arm aft. This got my brain spinning, and I decided to do the lower arm mod. Here's what I did:
To start, I disassembled the lower control arms and blasted everything clean. Take a note of the locations of the factory-located spot faces, as they are going to change to a new location on the shaft. http://i222.photobucket.com/albums/d...igslist130.jpg I sent the shafts to a friend who is a machinist. The intent is to move the lower control arm forward .75", so the spot face holes will need to move .75" on the shaft. I discovered that the factory spot faces on my shafts did NOT line up with the locating pins on the crossmember at both the forward and aft locations. Only the front actually used the pin, and the aft point was not a pin at all, just a raised area that acted more like a spacer instead of a locating pin. I wanted positive pin retention, so it was important that both front and aft points pinned into the cross shaft. Here's what you need to do: First, spin the cross shaft 180 degrees opposite of the factory spot faces so you have a nice clear area to work with. Then, make your .75" measurement from the centerline of the aft hole. Remember, you're moving the arm forward, so the new spot face will be closer to the edge of the cross shaft in relation to the original factory spot face. Once you have set this measurement, you must go to the crossmember and measure the center-to-center distance between the front and aft pins. My measurement was 9.0" exactly. So, for the forward spot face hole, I went 9.0" from the centerline of the newly located hole. Here is a side-by side shot of the factory locations versus the new locations. The upper shaft is the factory location, the lower shaft is the new location. http://i222.photobucket.com/albums/d...igslist132.jpg In order to do this mod, you have to remove the saddles that are riveted to the center crossmember. The lower control arm cross shafts are kept from spinning by a stud that locates itself in the spot-faced holes in the lower control arm shaft. Here, you can see a picture of the front crossmember showing the two bolt holes for the u-bolts and the rivet head for the locating stud I mentioned earlier. The stud side is not visible in this picture. http://i222.photobucket.com/albums/d...slist116-1.jpg In order to get the saddles removed, you have a few options. You can grind the heads off and drive out the rest of the rivet. Or, you can fire up the torch and melt the rivet heads off, then drive out the rest. I opted for the torch. I learned quickly that even with the head and tail of the rivet melted off, the rivet stems did not come out without a fight. I had to warm up the rivet stem with the torch and shoot them out with an air chisel. The rivets go through 4 layers of steel (doubler plate, saddle, and and 2 layers of the crossmember). Once you get them out, here's what the pieces look like after a few minutes in the blaster: http://i222.photobucket.com/albums/d...slist118-1.jpg Here's what you'll see when the saddles, doubler, and rivets are removed. I decided that I was going to use a 7/16-20 X 1.50" socket head cap screw as the new locating pin, so the center hole in this picture needed to get opened up to a 7/16 to ensure that bolt would fit nice and tight. The light area in the front is the lip on the crossmember, which will be cut away. Sorry for the dark picture, my lighting was a little goofy. http://i222.photobucket.com/albums/d...slist120-1.jpg Moving the control arm forward will cause the aft side of the control arm to get really close to the center crossmember, so I removed the lip and blended out the cut to eliminate any sharp edges that could cause a stress riser. You will only need to cut the lip back to where it meets the second metal layer. http://i222.photobucket.com/albums/d...igslist121.jpg Here's a shot of the saddles back in place on the crossmember. This shows the bolt in place of the old rivet locating pin. For added insurance, I used Loctite and a stover nut. Here's a shot of the finished installation: http://i222.photobucket.com/albums/d...pension007.jpg In this shot, you can see the head of the fastener, which will locate perfectly in the new spot face positions in the lower control arm cross bar. http://i222.photobucket.com/albums/d...pension008.jpg While the control arms were out, they got blasted and painted. New Energy Suspension bushings were installed and all the balljoints were replaced with Moog parts. Then the moment of truth arrived, and it was time to install the control arms and see if the caster mod was a success. Everything fit perfect. The clearances were excellent, and the locating pins lined up exactly as planned. Here is a shot of the driver's side control arm. You can see just how much the control arm moved forward. http://i222.photobucket.com/albums/d...pension013.jpg Here's a close-up shot of the back-side. If you recall, I had to clearance the crossmember. I now have plenty of room with the control arm at full up/down. http://i222.photobucket.com/albums/d...pension009.jpg Here's a shot of the front side. You can really the .75" difference in position from stock. http://i222.photobucket.com/albums/d...pension010.jpg Here's another thing I did to eliminate a huge shim stack in the upper control arm. On the 1973-up half-tons, GM utilized spacers on the control arm bolts, along with the normal shims. Because I cut a coil from the stock spring, I knew that the alignment shop would have to add more shims to get the camber correct. So, I went to the wrecking yard and grabbed some other spacers(the fat ones) and added them to the mix. The original set-up was: 1 skinny spacer on the forward bolt, and one fat spacer on the rear bolt. The new set-up is: 1 fat spacer on the front, and 1 fat and 1 skinny spacer on the rear. Not much of a difference, but I don't like the look of a huge spacer stack on lowered vehicles. It moved the arms out about 1/4" of an inch. http://i222.photobucket.com/albums/d...pension004.jpg Not a great picture, but you can see the offset between the upper and lower balljoint centerlines. This shows you how much the spindle will tilt aft, thus increasing caster. http://i222.photobucket.com/albums/d...pension012.jpg I'm not sure how much extra caster this mod will give me, but I think it will definitely be worth the effort. All told, I have right at $50 into this mod ($45 for the machine work, $5 for the nuts/bolts). I'm probably a couple of months away from being ready for the alignment shop, so I'll post up my results when I get them. |
Re: My caster mod (with pictures)
Looks great!! please keep us posted on the alignment specs. From my notes, you should be 6 to 7 deg static, and have some adjustment. Keep up the good work.
|
Re: My caster mod (with pictures)
This is on your 64 C20.
|
Re: My caster mod (with pictures)
Great writeup! I think I speak for everyone whenever saying that writups with pictures are the best. I also look forward to seeing what caster numbers you achieve with this mod cause I plan to do this to my 84.
I do have one question. Why did you take the time to remove the u-bolt saddles and reattach them? Ive heard of quite a few people doing this LCA modification to gain caster and I haven't seen anyone mention that this step was needed. |
Re: My caster mod (with pictures)
Very nice write-up! Have you installed springs yet?
Oh, and PLEASE save the pics to the forum, so that they will be here for years to come :chevy: |
Re: My caster mod (with pictures)
Quote:
Quote:
Quote:
Quote:
Mods-feel free to put this thread wherever you think it needs to go to be a reference. |
Re: My caster mod (with pictures)
wont the spring rub on the pocket
|
Re: My caster mod (with pictures)
I've done this. Not as detailed and clean as yours. I.didnt notice and spring rub.
Posted via Mobile Device |
Re: My caster mod (with pictures)
So im anxious to read the reviews, notice any difference lol?
|
Re: My caster mod (with pictures)
Nice work! I'm planning on doing either this, or moving the ball joint on the LCA.
One thing, IMO the locating pin is most likely only there to aid in installation. Once you get the LCA u-bolts tight, I think they hold the shaft from moving front to back. So I don't think modifying the saddles is necessary, but it won't hurt anything either. |
Re: My caster mod (with pictures)
Quote:
|
Re: My caster mod (with pictures)
Quote:
Thanks. I had a co-worker tell me the same thing about the saddles, and although I can see where he's coming from, I had to disagree. To me, the locating pins serve a few purposes. First, they index the control arm at a certain location in relation to the center crossmember, which in turn, helps establish the factory-spec'd caster angle. Plus, they ensure that the rotation of the control arm occurs at the control arm bushing and not on the circumference of the shaft. If the rotation occurs at the circumference of the shaft instead of the control arm bushing, it will wear grooves in the shaft at the contact point with the saddles. If it wears excessively, then the shaft will become sloppy and wear out the other suspension components prematurely . True, the saddles/U-bolts hold the shafts tightly, but during the constant abuse that the suspension sees during normal use, they help to keep the lower control arms from moving from front to aft. If the control arm was only secured using the u-bolts/saddles and hit something hard directly on the forward face of the control arm, it could move the arm back slightly, changing the alignment. I may be over-thinking it, but I think the locating pins serve a very important function. |
Re: My caster mod (with pictures)
Quote:
|
Re: My caster mod (with pictures)
Thanks for the write up!
|
Re: My caster mod (with pictures)
Quote:
Great write up, and great mod. Be sure to keep us posted with results. |
Re: My caster mod (with pictures)
Quote:
My question is, will we experience undesirable toe-out on turns readings by taking the steering arm on the spindle out of alignment with the pitman arm/center link/idler arm assembly? It seems to me that given the triangular geometry we will create by doing this, the outer wheel will want to turn at a greater angle than design, while the inner wheel will want to turn at a lesser angle. The setup of my 1982 C10 is shown, with the steering linkage in front of the wheel center axis. http://mpsmithedu.comxa.com/images/align_toeout.gif Your thoughts? Mike |
Re: My caster mod (with pictures)
Mike-
That's a great question. I'm going to have to draw this out on paper and visualize the linkage. Moving the arm back .75" will effectively move the tie rod attach point on the spindle up slightly and slightly to the rear. Because the change is occuring at an arc, the collective position change in the upward and rearward direction is very small. What I need to do is to install the linkage completely on the truck and see if I have an ackerman condition. If so, I could probably shift the idler arm on the passenger side frame rail to compensate, but the pitman arm on the steering box determines the position on the driver side, and that could get tricky. I believe that the combination of the ball-joint unions on the tie rods and the idler can compensate for the slight alignment change, but until I put the linkage together and see for myself, I'm not 100% convinced. I'm very interested to get more opinions on this, so feel free to post up any opinions, theory, or data. |
Re: My caster mod (with pictures)
Quote:
|
Re: My caster mod (with pictures)
Quote:
|
Re: My caster mod (with pictures)
Quote:
Quote:
|
Re: My caster mod (with pictures)
chevy, what is the over all caster angle in this mod compared to stock? im building a front stub on my 86 and want to build control arms but only build them once. im looking for a good angle to set up my arms. any help would be greatly appreciated.
thanks |
Re: My caster mod (with pictures)
In post #2, Rob says that I should have between 6 and 7 degrees static, with some additional degrees possible after adjustments.
|
Re: My caster mod (with pictures)
Nice work. Thanks for the write up and pics.
|
Re: My caster mod (with pictures)
Just had a thought.... this mod would center my tires in the fender.
That has bothered me since i put the 6° of caster in. Posted via Mobile Device |
Re: My caster mod (with pictures)
Quote:
Posted via Mobile Device |
All times are GMT -4. The time now is 03:15 AM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com