Wilwood parking brake and LMR/SVE wheel clearance issue

[FDLWproject]

Hi fellow problem solvers - happy Sunday

Things are picking up quickly on my MK4 build and I recently got my wheels and test fitted them on the hubs while the car is on jacks.

The issue:
The front wheel/brakes fit great. However, I put the rear 17” LMR wheels (17x10.5) on the hub and there is like 1-2MM clearance of the inner rim and the parking brake caliper. The wheel has weights on the inner rim for balancing, and they touch the caliper slightly on rotation. Something definitely needs adjustment. The LMR rim tapers on the inside of the wheel, constricting slightly from inside to out. There is no clearance issue for the brake caliper, just the parking brake caliper.

Relevant build details:
MK4 kit
8.8 IRS (SN95 hub assembly)
Koni coil over shocks
Wilwood 12.88” brakes that I purchased from FFR with kit (Dynapro Radial-MC4 Rear Parking Brake Kit - has separate brake/parking brake caliper and pistons)
- https://www.wilwood.com/Search/PartNoSearch?q=140-15138
Wheels from LMR - Mustang SVE FR500 Wheel & Nitto Tire Kit - 17x9/10.5 (link below- same as Blitzboy and man they look awesome)
- https://lmr.com/item/WTK-1007UBGN/mustang-fr500-wheel-tire-kit-94-04-black-nt555-g2-17x9-105

What is still outstanding:

Tightening CV axle nut – according to manual, should wait until I drop drivetrain in / install ebrake cables fully
Parking brake cables hooked up to parking brake (cables are fed through chassis though and hooked up to parking brake caliper)
Final IRS alignment – aligned as close as I can to manual specs, no Loctite on toe arm yet though until I get final alignment by someone smarter than me
Final brake line assembly (not really relevant – the flex lines from caliper to chassis mount are done)



Potential solutions based on threads I've seen:

Option 1: Grind down the caliper body at a steeper angle where it would slope more and not touch (thread here - https://thefactoryfiveforum.com/showthread.php?41682-Wilwood-Parking-Brake-Clearance-Issue)
Option 2: See if I can move the Wilwood parking caliper mount bracket inwards towards the hub to pull it away from the rim. Based on a quick look, it really doesn’t look like an option, as the parking brake caliper is already quite tight against the rotors.
Option 3: Contact Wilwood. Yes obvious answer but wanted to hear of any other solutions. I’ve seen from Blitzboy’s thread that he potentially had to swap out the entire parking brake caliper for another solution - potentially even another brake/parking combo caliper. Huge pain and $$$. Jesse (Blitzboy) also said in his build thread that he had a fixed rear and that IRS shouldn’t be an issue. Seems to be the same problem here though.
Option 4: Would the CV axle not being tightened yet have anything to do with this at all? Is there a chance that tightening it would pull everything tighter towards the axle and therefore fix the clearance issue?
Option 5: Would the final alignment change anything - my guess is definitely not.



Separate question – is this amount of clearance between the shock assembly and wheel going to be an issue (~0.4”)?

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[facultyofmusic]

Hey glad you found my thread! I too considered some of the options you listed above. Here were my thoughts and why I decided to grind it down.


Option 2: See if I can move the Wilwood parking caliper mount bracket inwards towards the hub to pull it away from the rim. Based on a quick look, it really doesn’t look like an option, as the parking brake caliper is already quite tight against the rotors.
Based on my measurements, there wasn't a way to bring the caliper "inward" enough to clear the wheels. Plus you'd be doing this by modifying the brake caliper mount, which consists of enlarging some mounting holes to give you more wiggle room. I didn't like the idea of intentionally introducing more "wiggle room" to my brake caliper mounting brackets. Oddly enough my mounting brackets DID come loose once at about 50miles. I tightened it back up and added some more loc-tite.


Option 3: Contact Wilwood. Yes obvious answer but wanted to hear of any other solutions. I’ve seen from Blitzboy’s thread that he potentially had to swap out the entire parking brake caliper for another solution - potentially even another brake/parking combo caliper. Huge pain and $$$. Jesse (Blitzboy) also said in his build thread that he had a fixed rear and that IRS shouldn’t be an issue. Seems to be the same problem here though.
This one was simply a question of $$$, which I didn't want to spend. After inspecting the body of the caliper I decided even if I trim off a bit of it it's still plenty strong to hold the clamping force required to keep the car in place. There are better places to spend that money. (e.g. wilwood parking brake cables to replace the FFR provided ones.)


Option 4: Would the CV axle not being tightened yet have anything to do with this at all? Is there a chance that tightening it would pull everything tighter towards the axle and therefore fix the clearance issue?
While I don't have any evidence to prove this I REALLY don't think tightening the axles will solve your problem. It's worth a try though. Worse case scenario you get new axle nuts. Best case scenario everything works out. I tightened my axle nuts pretty early and I never had to undo it. The IRS area is very accessible.


Option 5: Would the final alignment change anything - my guess is definitely not.
It will not.

Note that I'm not saying my way is the obviously correct way to do it. You may care about the look of the parking brake calipers more than I do, or just don't feel comfortable modifying brake calipers, that's fine. :) Do what's best for you. Have fun and be safe!

[CraigS]

I'd say step one is tighten the axle nut. I don't see any reason not to. If you are concerned just tighten one side to check for clearance. Is there enough taper inside the wheel that a 1/4 to 3/8 wheel spacer would help? You could simulate spacers by stacking up washers on three lugs as a test. Since the 2015+ Mustangs came w/ at least 18" wheels fitting 17s is a challenge. When I did my IRS retrofit on my MkII, I used the OEM calipers and I had 3 sets of 17s. One from OE and 2 from American Muscle. The OEs didn't fit, the AMs did. Spending $ on 18s or on different 17s 'might' get you a fix. But if Wilwood doesn't have an answer I'd get out my big grinder for a free fix. One more thought. Move the weights. Standard practice is for balancers to put the weights as far out on the wheel as they can. But they can be moved inward and the amount of weight increased for the same effect. On one car I had previously I had permanent marker zones on the insides of the wheels pointing out where weights could NOT be placed.

[FDLWproject]

Very glad I asked - thank you both!

I’ll try tightening the cv axles first, then see if moving the weights would help - hadn’t considered that. Also - I have an extra set of Wilwood parking calipers that I damaged (my own stupidity, not related to this) that I plan to use as a test run with the grinder before moving on to the good ones. Serendipity at its finest.