Slotting the strut for more camber

[GTP]

This post is one of a multi-part series for DIY alignment measurement and adjustment.

Slotting the strut for more camber (this post)
At-home method for measuring camber
At-home method for measuring toe with Toe Plates
Tips for easily adjusting Camber and Toe between street and track settings
Review of Rear Camber Adjustment Kit (Steeda or J&M camber arm brackets)
My DIY Wheel Cribs
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When going to wide Cup 2 tires for the first time I knew I would need more camber to get the most traction and even wear. I determined that my J&M camber plates would bottom in their slots before the strut shaft contacted the tower hole. Therefore I would have to switch to another brand of camber plates (for longer slots) and cut more clearance into the tower hole.

Instead I decided to slot the upper strut-to-knuckle holes. This post is a pictorial of my method.

First, I did the math. The spacing between the two strut bolts is 78mm. 1 degree more camber requires Tan1° x Spacing = 0.017 x 78mm = 1.36mm. I decided to file 1/16” (1.6mm) to the holes, which calculates to 1.1° more camber.

I found and ordered a 5/8” diameter file from McMaster to file the 16mm holes “sideways” in the inboard direction. This ensured that the oblong hole remained perfectly round at the filed side.

I removed the struts. A ball joint press borrowed from the parts store worked much better than a short-handle sledge hammer for getting out the big splined 16mm bolts.

I put each strut on top of the trash barrel and started filing away. The strut holes were 0.629” diameter. I stopped filing when the oblong hole measured 0.700” in the long direction. Here you can see all the filings piling up. It took about 30 minutes of filing per strut.

I verified the result by measuring the “shift” in a bolt in the hole with a caliper, offset method.

During strut resassembly, I used a large F clamp to ensure the knuckle pushed the upper bolt against the inboard side of the new oblong hole. You can see it positioned at a small flat region of the GT350 knuckle.

A 24mm ratchet wrench was handy for initial tightening of the nut.

I also added serrated 5/8” Nord-lock washers at both ends of the upper bolt.

The NL16sp has a larger outer diameter and fits the washer head bolts better.

I torqued the lower bolt to 185# spec, but I torqued the upper bolt as hard as I could with a 25” breaker bar.

I measured front camber for street and track settings, and confirmed that I did gain the 1° extra camber desired. It is now 3.6°.

After my track weekend, I verified that the paint marks had not moved, so all good.

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[John S]

Do you prefer this method over camber plates? (cost saving option?)

 

[John S]

Sorry, reread the beginning.

 

[NightmareMoon]

The only thing I would add to this is with a slotted bolt hole there are a couple extra things to consider.

1) you're losing the splines when you slot it, so you're at a greater risk of having a bolt fall out of the nut loosens. For this reason its really recommended to use new strut to spindle bolts, as I believe these big boys one time use torque to yield bolts- that helps with the nut backing off sometime down the road. With the right torque and fresh bolts they should hold the position.

2) If the nut loosens, you'll loose that alignment, and it can bend the strut bracket in that case. (happened to me one time only minutes after leaving the alignment place).

If you're concerned about the bolt moving in the slot, you can also weld in a little bit of material inside the bolt hole to make the new position effectively permanent, which also helps keep things secure.

 

[mavisky]

Is that rubbing on your strut from your tire already?

You realize that by moving adding camber by slotting the strut mounts you're adding the camber relative to the hub and not the strut which thereby reduces clearance to the strut even more?

 

[kz]

I'll second what Nightmaremoon has written above - on my those strut bolts do come loose, I posted a pic elsewhere with one nut completely missing and another half down the thread.

Also with Steeda plates on a Magride car I can get ~ -3.7 degrees of camber without enlarging strut tower holes.

 

[GTP]

The only thing I would add to this is with a slotted bolt hole there are a couple extra things to consider.

1) you're losing the splines when you slot it, so you're at a greater risk of having a bolt fall out of the nut loosens. For this reason its really recommended to use new strut to spindle bolts, as I believe these big boys one time use torque to yield bolts- that helps with the nut backing off sometime down the road. With the right torque and fresh bolts they should hold the position.

That's what threadlock and the Nord-lock washers are for.

2) If the nut loosens, you'll loose that alignment, and it can bend the strut bracket in that case. (happened to me one time only minutes after leaving the alignment place).

If you're concerned about the bolt moving in the slot, you can also weld in a little bit of material inside the bolt hole to make the new position effectively permanent, which also helps keep things secure.

Good to know. I monitor the situation with every pad/wheel change.

Is that rubbing on your strut from your tire already?

No.

You realize that by moving adding camber by slotting the strut mounts you're adding the camber relative to the hub and not the strut which thereby reduces clearance to the strut even more?

Yes, I do. That's what spacers are for.

I'll second what Nightmaremoon has written above - on my [car] those strut bolts do come loose, I posted a pic elsewhere with one nut completely missing and another half down the thread.

Also with Steeda plates on a Magneride car I can get ~ -3.7 degrees of camber without enlarging strut tower holes.

Good to know. I did not want to get new plates and go through the hassle of exchanging them. And I did not want to go to camber bolts. After enough research and consideration, I settled on this solution.

 

[WD Pro]

I did something similar on a milling machine a long time ago.

I followed instructions from a magazine article at the time - it recommended using oversize washers of the correct internal diameter to suit the bolt, and then tacking them in place when you had the desired setting.

WD

 

[NightmareMoon]

yeah the lock washers look interesting. Let us know how they work out in the long run.

I don't think they'll actually solve for camping force with under tightened or overly reused bolts, but hopefully they do the trick of keeping those nuts in place. Seems like they should.

Sometimes you gotta run slotted struts for one reason or another. My current coilovers came that way and I set the knuckle bolts in the slot based on the clearance I need with my widest 18" wheels, and then do the rest with camber plates at the tower.

Witness marks are always a good idea!

 

[SL8888]

GM, Ford & Chrysler (Stellantis) and other auto makers spend millions of $$$ on suspension design for safety & longevity, and we sometimes take the liberty to modify or improve on their design. Pearls of wisdom were shared with me long ago, "Put your life on the line for your design"...

 

[WItoTX]

GM, Ford & Chrysler (Stellantis) and other auto makers spend millions of $$$ on suspension design for safety & longevity, and we sometimes take the liberty to modify or improve on their design. Pearls of wisdom were shared with me long ago, "Put your life on the line for your design"...

Someone will provide more details, but this method is what Ford recommends for cars that may need camber adjustments. It's pretty proven and reliable.

 

[kz]

GM, Ford & Chrysler (Stellantis) and other auto makers spend millions of $$$ on suspension design for safety & longevity, and we sometimes take the liberty to modify or improve on their design. Pearls of wisdom were shared with me long ago, "Put your life on the line for your design"...

It's a service manual procedure for front camber adjustment (as there isn't really anything else on a stock car).

 

[GTP]

It's a service manual procedure for front camber adjustment (as there isn't really anything else on a stock car).

I wanted to attach that to my post but I couldn't put my fingers on it.

 

[WD Pro]

Someone will provide more details, but this method is what Ford recommends for cars that may need camber adjustments. It's pretty proven and reliable.

It's a service manual procedure for front camber adjustment (as there isn't really anything else on a stock car).

I wanted to attach that to my post but I couldn't put my fingers on it.

Here you go

WD

 

[GTP]

Thanks.

I used it as a quality check of my math. But I went beyond the 1mm recommendation so that I would not have to repeat the ordeal, and to make sure I achieved the desired camber, or a bit more.

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