How to: Adjust Subframe for Camber/Caster Adjustments

Stuff Needed:
-21mm socket (rear attach bolts)
-17mm socket (front attach & RMM bolts)
-Torque Wrench that covers at least 75 ft/lbs & 120 ft/lbs
-1/2" impact wrench if you have access to one
-Large prybar
-6x25mm+ bolt/screw w/ plain nut or STD equiv.
-wrench to match bolt
-ruler
-Two 3T jackstands
-Floor jack (I used ramps and the jack)
-Brick to chock the rear wheel (use the parking brake too)

Setup
I'm assuming at this point you already know that you'll need to shift your subframe, you have cross camber and/or can't otherwise get both sides camber to match.

***Item of note: Move the subframe to the side you desire more negative camber. You are moving the lower control arm ball joint farther outboard on the desired side which will give you more negative camber.

Get the car up on jack stands, you do not want to support the car by any part of the subframe.

Loosen the subframe bolts and the RMM bolt. Front two bolts located below near the shock tower. 17mm and 12" long extension (1/2" recommended). You only need to loosen them a few turns, enough to allow the subframe to move. The star washers may be loose. While you have the 17mm loosen the RMM bolt.





Loosen the rear subframe bolts (21mm), again you only need to loosen a few turns. Use an impact or a 1/2" breaker bar, these are tight.



I took off both wheels because it was convenient but you don't absolutely need to. You're looking for the hole that is designed for the plastic brake line clip. Here's the clip that installed on the right side. If like me you need to shift your subframe to the left you will have to remove the plastic clip that holds the right brake hard line. Either a small pick or small needle nose pliers will help disengage the two ears, set aside for reinstall later.



Put together your adjustment tool, also known as a bolt and plain nut. Assemble it inside of the hole as you see below. Snug it up on the subframe with the appropriate tools.





Adjustment
Using the tool start shifting the subframe. I measured the gap between the body tab where the adjustment bolt/screw goes and the FWD subframe bushing collar. I knew my subframe needed to be moved to the left to equalize my ability to adjust camber and then adjust in as much caster possible (mentioned later). I may be overestimating Mazda's quality control on the manufacture of the body and subframe but my initial plan was to equalize the measurement for both sides, in my case it was approximately 17.5mm for each side.



When it reaches the measurement you desire you're almost done. Now I bring up shifting the subframe forward to maximize whatever caster you can muster. With the adjustment bolt still in place grab a decent sized pry bar and the ratchet with the extension and 17mm and start with the front attach bolts. What you're going to do is use the pry bar in the radius of the body and pry on the back side of the forward subframe tower to force the subframe forward, this will increase your caster as much as possible. While holding pressure on the pry bar to keep the frame as far forward as possible snug up the bolt. Repeat on the opposite side. Double check your measurements and tighten and torque the subframe mount bolts, 65-85 ft/lbs for the front, 99-129 ft/lbs for the rear.and 54-66 ft/lbs for the RMM.



Here is a pic showing the subframe moved as far forward as possible to maximize the available caster. You can see there is a pretty substantial amount of movement in my case.



Reinstall any wheels removed and take the car off the jack stands, torque your lugs to 65-87 ft/lbs. Now it's time for an alignment, either do you own string alignment or take it to a reputable shop that will set the specs exactly as you want them.

If you have all the tooling on hand and ready this can be done fairly quickly and should you need to adjust further it'll be easier the second time.

 

Do you have any before/after specs?

Kinda curious on this as I've done this multiple times with very little effect.

 

Wow I wish I had thought about this when i had the subframe loose for installing my front sway bar! How much extra caster did you get?

 

I can track down before specs but no after specs yet, I need to replace the inner tie rods (nuts seized) and can't adjust toe. I should have taken a pic of both camber plates before because they were on opposite sides of the strut opening, not approx the same between both sides. I'm not going to string it straight away just the local shop that does a decent job. I've got to corner balance the car before I get crazy.

 

Did you adjust the rear bushings side to side as well?

Good idea on the screw / nut

 

Once everything is loosened up the rear slides back and forth easily so no twisting unless you set it that way.

Screw idea came from Zenit on the other forum and worked out great for more precise control. His thread was full of dead pic links so I thought creating one here with uploaded pics rather than links would be helpful for others.

 

Following a slight run in with a Lexus RX300h and it's daft owner it'll be a bit before I get a chance to corner balance the car and align it.

 

Update.....

Following the body shop debacle that lasted a month, weighing the car and getting it back on an alignment rack I have some feedback on the subframe shift.

Caster
Before above subframe adjustment
L 3.6* R 2.9*

After
L 4.0* R 3.5*

Although they are not matched they are slightly closer and more importantly more in general. I have yet another round of subframe shift to perform because I'm still having camber range of adjustment issues. I need to move the subframe another 0.2" to the left, I suspect the left caster will reduce slightly at that point but we'll see.

 

Since this is now somewhat of a diary in my quest to even out the camber available and gain as much caster as possible, I have made yet another and likely final adjust for now. I was able to get the subframe to slide left another 5mm however after taking some other measurements I'm still off approximately 3mm and to eliminate bind in the RMM I had to loosen the TMM and PMM and slide the engine a left a bit as well. Although 3mm doesn't sound like much that how far out of square the front end is.

I also found the camber plates I have installed have reached their limit as well. For now I'm stuck at the max they can provide until I draw up some new base plates and have them machined. I plan to have the car aligned later this week so we'll see what I'm able to get out of it.

 

I'm at the end of the line for now. I have managed to move the subframe as much as possible to resolve my camber issue, unfortunately I wasn't able to get as far as I'd hoped but it was an experience.

Without further a do here's the before and after results on the front-end:
Before camber plates (camber/caster):
L -0.08* / 3.4* R -1.6* / 3.1*

w/ Camber plates:
L -1.5* / 3.6* R -1.4* / 2.9*

1st Shift
L -1.4* / 4.0* R -1.3* / 3.5*

Final
L -1.4* / 3.9* R -1.4* / 3.4*

Net results:
Camber: a wash, limited to camber plate adjustment range on the L/H side
Caster: L +0.04* R +0.5*

So at the end of all this work I would say that it might be worth it for the added caster I can't say for certain what camber results one might achieve with the standard top hats.

Unfortunately, the camber never got to where I was hoping for (-1.8* to -2.0*) due to limitations on the left strut tower. I like the general design and adjustment functionality of the camber plates and for the price (~$170 USD before shipping) they have been worth it they do not seem to be designed to maximize camber as far as one would like/need for autocrossing. The class I'm running allows for camber plates and modifying strut towers but I don't wish to slot the towers since I have no plans to own the car for more than a couple more years. This winter I will likely draw up and machine out some new base plates for the camber plates and machine the spherical bearing housing slightly with a goal of getting -2.0* or more negative camber, there is room to make it happen.