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#1 |
Senior Member
![]() Join Date: Aug 2018
Location: London, Ky
Posts: 1,161
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Lower a arm, moved forward for caster
So I moved the lower a arms forward 3/4" and when I put the spacers and shims on the upper a arms I barely get the full thread of the rear nut on it. I used square body a arms and the stock cross member that come on the truck originally in 1971. Are the studs for the upper a arms shorter on the 71 crossmember than they are on the newer square body a arms. I'm worried about getting the alignment right when the time comes. Hopefully someone that has run into this will chime in. I followed an old thread that someone done a how to on and with the spacers that was recommended I can't get any shims in the rear stud on the upper a arm. Here is a picture of what I have as of now.
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#2 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,526
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Re: Lower a arm, moved forward for caster
Get rid of the convex washers if there is no concave place for them and just use the shims. Mi-matched parts
And why did you move the lower shaft forward out of the index hole? Should be enough alignment to get the proper caster |
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#3 |
Senior Member
![]() Join Date: Aug 2018
Location: London, Ky
Posts: 1,161
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Re: Lower a arm, moved forward for caster
I followed an old thread on here called my caster mod I think was the name of it. He drilled a new index hole in the lower a arm shaft to move it forward to gain more caster.
Last edited by CarlsLQ9SS; 06-11-2020 at 01:11 PM. |
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#4 |
laying low
![]() Join Date: Mar 2001
Location: Searcy, Ark. USA
Posts: 13,232
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Re: Lower a arm, moved forward for caster
Carlos have you looked in the suspension forum yet? You may get more response down there as it is suspension specific. A number of guys have done this mod but I am unaware of any issues with it.
They say 5 to 6* positive caster is what you want for good return to center and handling. I have not done this yet but will consider it.
__________________
Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross |
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#5 | |
Senior Member
![]() Join Date: Aug 2018
Location: London, Ky
Posts: 1,161
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Re: Lower a arm, moved forward for caster
Quote:
Last edited by CarlsLQ9SS; 06-12-2020 at 07:11 AM. |
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#6 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,117
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Re: Lower a arm, moved forward for caster
I too did the caster modification that involves redrilling the lower control arm shaft. How much is your truck lowered? The lower the truck's ride height is the more shims it takes to get things come around to acceptable specifications. Remember alignment specifications are trade offs. You're looking for the best balance for your intended usage. The factory has it's own parameters in mind when they publish their recommend alignment specifications.
Do not remove the convex washers! They are there so the shims can sit properly against the upper control arm shaft. In order to align the wheel properly the upper control arm shaft will not be parallel to the frame. This means that the shims will only contact on one end. In order to avoid having to make angled shims GM used the convex washer so the shim will seat flat against the control arm shaft and the center part of the shim will seat against the washer securely. It is possible for the shims to work out without the washer. (Something I know from experience ![]() You can look at the link below for details on what I did with my Burban and it's alignment. Unfortunately it is somewhat spread out in the thread so you will have to do some scrolling. https://67-72chevytrucks.com/vboard/...698377&page=11 This links to the previous page showing how I modified the index on the shaft. https://67-72chevytrucks.com/vboard/...698377&page=10
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 Last edited by HO455; 06-11-2020 at 01:54 PM. Reason: -2 grammar |
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#7 |
Senior Member
![]() Join Date: Aug 2018
Location: London, Ky
Posts: 1,161
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Re: Lower a arm, moved forward for caster
Thank you for the links, now i get to do some more reading on your awesome build! Read a few pages so far, and looks like alot of good info!
Last edited by CarlsLQ9SS; 06-11-2020 at 02:29 PM. |
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#8 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,117
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Re: Lower a arm, moved forward for caster
Thank you sir. Good luck with yours.
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#9 | |
Registered User
Join Date: Apr 2001
Location: DALLAS,TX
Posts: 21,967
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Re: Lower a arm, moved forward for caster
Quote:
Lowering a truck can impact the quantity of shims required. How it's lowered has more to do w/just how much. Aggressive spring drops usually require more shims vs a drop spindle + mild spring drop. I believe the truck in question is a 71 but it's using 73 & later arms. The 73 & later arms use the convex washers because the mounting shaft is set-up for them. Earlier trucks or shafts w/o the 'divot' don't require them. Generic alignment shops will traditionally attempt to get the settings that are "In the Book". You want better settings. Factory stuff calls for (in general): 1-3.5° Caster; .5 - .7 POS Camber; 1/16 - 3/16 Toe-in. The caster mod will get you easily in to the 5° range. Too aggressive can be too much as well so that 5-6° would do well. Camber needs to be opposite what the factory specs, Aim for 0 - .7° NEG. I usually request .5 NEG & it works well for daily driving. Go more aggressive if you're building a 'sport' truck. As a side benefit, negative camber requires fewer shims on a set-up like this (C10's). Toe is kind of regulated to how much tire is involved. I would try to keep it on the lower side of the specs @ 1/16 - 1/8.
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67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. |
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#10 | |
Senior Member
![]() Join Date: Aug 2018
Location: London, Ky
Posts: 1,161
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Re: Lower a arm, moved forward for caster
Quote:
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#11 | |
Registered User
Join Date: Apr 2001
Location: DALLAS,TX
Posts: 21,967
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Re: Lower a arm, moved forward for caster
Quote:
Back in the day (>30yrs ago), we would sometimes need to put longer upper shaft bolts in for the excess shims as a result of just cutting coils. With drop spindles & other lowering options, you can keep the spring longer & usually not need the super thick shim stacks.
__________________
67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. |
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#12 |
Registered User
Join Date: Jul 2012
Location: Whitehorse yukon
Posts: 1,218
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Re: Lower a arm, moved forward for caster
My question is why not buy new 73 up studs to get longer bolt length
Then there will be less worry of catastrophic failure of thread engagment at say Interstate highway speeds |
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#13 |
Senior Member
![]() Join Date: Aug 2018
Location: London, Ky
Posts: 1,161
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Re: Lower a arm, moved forward for caster
I was wondering if the 73 up had longer studs. Maybe someone that knows for sure will chime in.
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#14 | |
Registered User
Join Date: Apr 2001
Location: DALLAS,TX
Posts: 21,967
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Re: Lower a arm, moved forward for caster
Quote:
Why put a longer stud in where it's not needed?
__________________
67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. |
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#15 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,117
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Re: Lower a arm, moved forward for caster
There are quite a few threads about "Not enough threads" problem" which I have read and the 1973 stud replacement cure is not one I have heard of. The studs may be longer but maybe the splines are wrong. I'm not saying it isn't a cure but if it was that simple I don't think I would have found so many threads on the issue. The most common replacement cited are ones from Speedway and Jegs. Not vehicle specific so you would have to measure yours to determine if they would not only be longer but that they fit correctly.
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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