Converting to front disks

[remytherat]

I am looking to convert to front disks, keeping manual master cylinder. I have 14x7 wheels with small bolt pattern all around, but front passenger wheel is slightly bent and should be replaced.
When converting to disks, should I also convert to 5x4.5 bolt pattern with 15x7 wheels? If so, I will have a mismatch with the rear wheels, as I don't plan on changing out the rear end and thus the bolt pattern for a while. Is this okay?

 

[junkyardhero]

it's up to you if want to convert to the 5X4.5 big bolt pattern or stay 5X4 small bolt, you can do the swap with factory components or aftermarket kits exist for both.

you can run the smaller big bolt pattern discs with most 14" wheels, there can be fitment issues with some aftermarket small bolt kits and 14" rims.

benefits of the big bolt swap are cost and availability of parts as well as selection of rims.

ultimately the choice between small bolt/big bolt comes down to budget and what the ultimate end goal is.

you can run mismatched front and rear, just carry two spares.

 

[gdrill]

SBP generally is harder to find and or expensive.
LBP is dripping off the curbs.

 

[66fs]

I am looking to convert to front disks, keeping manual master cylinder. I have 14x7 wheels with small bolt pattern all around, but front passenger wheel is slightly bent and should be replaced.
When converting to disks, should I also convert to 5x4.5 bolt pattern with 15x7 wheels? If so, I will have a mismatch with the rear wheels, as I don't plan on changing out the rear end and thus the bolt pattern for a while. Is this okay?

Been there done that. Just keep the SBP in the end it is cheaper and less complicated. What car and what brakes do you have now? Get a conversion kit or a set original K-H front discs from a 66-72 A-Body.

 

[Dave999]

ideally you would also run a disk/drum master cylinder and put in a brake bias

the pressures necessary to activate fully, a set of disc calipers is way higher than that needed for the rear wheel cylinders... so a bias to stop the rears being full on when the fronts are only 50% on is needed. otherwise the rears lock first resulting in a disconcerting loss of control. i.e the rear will try to overtake the front in a spin until you lift off the brakes

if the fronts lock first at least you just, go...... in a straight line.

single most best upgrade i did was to add in the brake bias
My dubious 1 pot calipers really work quite well when allowed to supply most of the braking.

previously the rears were like an on off switch locked or not locked in anything but bone dry conditions
and my rears are 9 inch..!

on an empty or private paved road
Bias rears nearly off and start doing hard stops i.e try hard to detach a retina
each time adding a bit more rear brake until you achieve the best stop
you will know if you go too far because the car will end up sideways

when happy lock off the bias adjuster and never worry again.

Dave

 

[AbodyBB]

Putting any proportioning valve in the system makes the peddle feel harder.
If you have the original 10 x 1 3/4 rear brakes, keep them. This reduces the rear bias significantly. I drive mine without as much adjustment in the shoes so the pedal travels more thus giving more front bias.
Big bolt pattern on the rear can be done easily by using DrDiff axles and six cylinder B body drum. (Retains A body Backing plate) Drums are hard to find but soon I will do a write up to explain other drums that can be used.

Finally on the fronts read the multitude of comments on this forum with plenty of great insight from everyone who has done this. My personal preference is to use the SSBC kit. They still offer the dual pattern 5 on 4 and 5 on 4.5 rotor and uses the Kelsey Hayes caliper. The whole kit is based on the mustang disc system(KH calipers and Mustang rotor) so you can keep the SBP up front or change out later by swapping out your lug studs. Only catch is that eventually SSBC won’t provide dual pattern rotors for replacements. (I’m working on fixing that as well.)