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Author Topic: BF and BG knuckles compared  (Read 6493 times)

chrispoe

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    • 91 BP Capri GT
BF and BG knuckles compared
« on: May 03, 2015, 03:49:29 PM »

For the longest time I’ve wondered what’s the exact difference between the BF platform’s steering knuckle (323 and Capri) and the BG platform’s knuckle (escort gt and protégé). In this first pic we have the BF on the left, the BG in the center, and a GE (2nd gen ford probe) on the right. I won’t bother talking about the GE knuckle because it just too different.


For this next pic I put a paint stirrer into the lower pinch bolt opening and centered it to the strut mounting point to help create an imaginary kingpin line. As you can see the pic below the hub is centered to the lower balljoint and the strut mount which means the caster will not change. I also measured the length of the steering arm hole to the center line and they both equal 120mm.


The next thing to look at was the lower balljoint mount. The lower mounts are identical to each other and the BF’s lower balljoint will mount to the BG knuckle. The location of the pinch bolts was the same distance from the center of the hub and to the surface of the hub flange.
 

Now the next thing to look at is the strut mount location pic

As you can see from the pic they are not quite the same. Both mounts are 26mm wide, but the holes are in different positions. The BG’s lower mounting hole is the same distance from the lower pinch bolt hole, but it’s also 3mm closer to the hub flange.  The BG’s upper hole spaced an additional 5mm apart from the lower hole compared to the BF and is moved 5mm closer to the hub flange too.

Now it’s time to take a look at the steering arm

The BG steering arm is the correct length from the center of the hub, but the height and the angle of the arm is different. In the pic above, you can see the effects the improper angle.  The BG knuckle will put the outer tie rod bearing 14mm closer to the hub flange and result in reduced ankerman.  The BG’s steering arm’s height is also 16mm lower then the BF’s arm and will result in an increase to bumpsteer.

Edit: The outer tie rode hole on the steering arm of the BF and the BG is 12mm on the bottom side, but the arm's width and depth in terms of height are different. The BF is 16mm while the BG’s is beefier at 19mm.
The wheel bearing opening diameter on the BF knuckle is 63mm and the rear seal is 52mm in diameter. The BG has bearing opening of 74mm and the seal is 56mm.


The last pic shows the difference in the hub and a nice crack on the top right of my rotor. The hubs on the BG knuckles have a different spline count and lug pattern. The BG hubs have 26 splines and come with a 4x100 lug pattern, while the BF hubs have 24 splines and the lug pattern is 4x114.


Edit 6/24/16: There are two variations of the BF knuckles.  One version has shorter caliper mounting ears to position the brake caliper closer to the center of the hub and uses a smaller 9 3/8” rotor.  The other version has longer caliper mounting ears and uses a larger 10 1/4” rotor.
The BG knuckle actually comes in multiple versions too. While all BG knuckles come with the same 26 spline/4x100 lug patterned hub, they come with two different size rotor options similar to the BF knuckles. There are also three different size lower balljoint stud sizes too, depending on which model and year of vehicle the knuckle is from.
« Last Edit: June 25, 2016, 02:41:10 PM by chrispoe »
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greywolf27030

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Re: BF and BG knuckles compared
« Reply #1 on: May 04, 2015, 10:01:55 AM »

Great research.  Your conclusion is not usable or modifiable?

Jack Byrd
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Jack Byrd

Rocketman

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Re: BF and BG knuckles compared
« Reply #2 on: May 04, 2015, 10:15:05 PM »

Not without a crazy list of modifications

Great pictures Chris! Thanks for the comparison
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


chrispoe

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Re: BF and BG knuckles compared
« Reply #3 on: May 05, 2015, 08:05:22 PM »

Great research.  Your conclusion is not usable or modifiable?

Jack Byrd

For my application (project GTZ) they’re usable and the modifications require were a lot less then originally planned. In fact no modifications are required to the BG's knuckle itself, just the BF's strut mount.
« Last Edit: August 21, 2016, 09:33:08 PM by chrispoe »
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greywolf27030

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Re: BF and BG knuckles compared
« Reply #4 on: May 06, 2015, 08:39:48 AM »

For my application (project GTZ) they’re usable and the modifications require were a lot less then originally planned. In fact the only modification to the BG's knuckle itself was to drill and tap the steering arm hole.

Next question, what is project GTZ.  Sounds interesting.

Jack
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Jack Byrd

chrispoe

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Re: BF and BG knuckles compared
« Reply #5 on: May 07, 2015, 09:09:22 AM »

Project GTZ is a complete upgrade of the brakes, drivetrain, engine, and suspension. Pretty much everything from the hood latch to the firewall is being upgraded.
« Last Edit: May 07, 2015, 09:21:21 AM by chrispoe »
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greywolf27030

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Re: BF and BG knuckles compared
« Reply #6 on: May 08, 2015, 08:08:22 AM »

Wow, sign me up for the thread.

Jack
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Jack Byrd

chrispoe

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Re: BF and BG knuckles compared
« Reply #7 on: May 08, 2015, 08:45:25 AM »

I really should start a build thread.
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greywolf27030

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Re: BF and BG knuckles compared
« Reply #8 on: May 09, 2015, 09:20:48 AM »

Inquiring mines want to know.... :-*

Jack
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Jack Byrd