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Adjusting the front subframe

 
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Old 05-17-2019, 09:42 AM
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Question Adjusting the front subframe

I went to get an alignment and rear tires yesterday. The alignment tech said the front subframe had been removed previously and was not dead on. This prevent one wheel from being centered on camber. It was just at the edge of the range while everything else was dead on. The he showed where it did not line up perfectly from the torque markings said it was most like taken off for a previous service or something. Is this a big job to get centered? I know I will have to do an alignment again, but that's fine. I may not even bother if it's going to be really expensive job since it is aligned within spec.
 

Last edited by brightoncorgi; 05-17-2019 at 02:42 PM. Reason: original text said rear subframe and meant front subframe
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Old 05-17-2019, 02:08 PM
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Maybe it's not that big of a difference. How much off is that camber?

Btw, are you referring to front or rear? Your title says otherwise.
 
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Old 05-17-2019, 02:34 PM
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Originally Posted by V12Vin View Post
Maybe it's not that big of a difference. How much off is that camber?

Btw, are you referring to front or rear? Your title says otherwise.
The front sub frame. The right front caster was maxed out at 4.7 (range is 4.8 - 5.5) was 4.7 before and after the alignment since he could not adjust it.
 

Last edited by brightoncorgi; 05-17-2019 at 02:42 PM.
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Old 05-17-2019, 07:32 PM
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I wouldn't worry about it, it drives straight and wheel is centered correct? That's not going to induce excessive tire wear. The left was @ 4.7 caster before also. Then changed to 5.0 Vehicles tend to pull to the side with the least amount of caster. So if your street is straight and it doesn't drift to the right with those readings its it's fine.
 
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Old 05-18-2019, 12:58 PM
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^ +1
 
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Old 05-20-2019, 11:37 PM
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Don't worry about it. I'd say 1 minute trust angle is as good as it gets.
 
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Old 05-21-2019, 12:36 PM
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The front subframe doesn't really allow for moving, some of the bolt holes are oval to allow ease of threading when removed(because of the chassis flex)..but it's not an adjustable part. In theory I guess you could enlarge or oval the holes more to gain the ability to move the subframe, although this would require removing the lower suspension arms each time to adjust the subframe (making dialing in the alignment near impossible or excessively laboured).

One of the main reasons the caster is not in spec on the VH platform is related to the upper front arms. The plastic bushing sleeves walk in the arm, which result in the caster not meeting spec, if caster is to far out it can hinder the camber settings as well. Something I'm really confused about, why did the tech adjust the Caster on the left to 5.0 when it was better set to 4.7 matching the opposite site. Just because 5.0 was the desired spec in the "green", doesn't mean the car will now handle better and prolong tire wear. If the caster setting on the right was found to be maxed out but still near spec, the left caster should of been set to match (which it was already).

Btw, those specs in the Hunter alignment are a "weighted" alignment spec. which means your Rapide needs a full tank of fuel + 150lbs on EACH front seat, 30lbs of weight centered in the boot/trunk. If the weight was NOT applied, means the spec used was incorrect. The weight is not to simply simulate passenger weight in the vehicle, its how manufactures have determined the estimated height of the vehicle when load is applied to the vehicle at highway speeds (aka downforce). If this was an air suspension vehicle the actual ride heights would of been monitored, being your car is coil sprung, weight is applied because over time those springs will sag, thus measuring stationary height would be inadequate.
 
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Old 05-22-2019, 05:08 AM
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irish07 What is your suggestion then with the car? Do you think this is upper control arm related? Should I do the alignment again to correct the left caster? The car was not sandbagged before adjusting. The AM dealer does not do that either.
 
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Old 05-22-2019, 05:58 PM
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brightoncorgi I would recommend first taking a look at your front upper arm bushings. If you see the bushing sleeve has walked out of the arm by few millimeters (very possibly), correct the issue by installing newer arms with metal sleeved bushings. The V12 Vantage S/Rapide S/ 13MY DB9/Vanquish had different arms with metal sleeved bushings to correct this issue (which in my opinion is a common occurrence with the plastic sleeved bushings Aston used front and rear). The main different besides bushing stiffness of the metal arms mentioned, is the balljoint size..I don't recall the Rapide balljoint size off memory but the dealer would know by looking at the parts catalog. Think the base Rapide and Rapide S shared same 12mm balljoint and Rapide S arms had the metal sleeves that I would fit into the regular Rapide. It's been awhile since I've done a Rapide so I'd measure it out before ordering anything...Nonetheless this is all assuming the upper arms are with plastic sleeves and that they have walked resulting in caster issues.
 
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