[Striker01]

What are the best kits out there for 4 lug rear disc conversions? The kit at north race cars doesn't feature a new booster.

Is it not needed or?


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[Isaac2012mustang]

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[thadude]

You could upgrade to a 93 Cobra or SVO unit but I *think* the OE works as long as a proportioning valve is used. But tbh that LMR kit looks pretty solid to me.

 

[qtrracer]

I used the SSBC kit (essentially the 93 Cobra or T/B Turbo Coupe). Didn't need a new booster or M/C even with 87+ 11" rotors since the later caliper is the same size as the 86 caliper. Used the original 86 stuff. When I upgraded to the SVO 73mm front caliper, then I switched to the SVO M/C (still used the stock booster). This "upgrade" was a mistake. The F/R brake torque bias was too much to the front. Never did get it dialed in. The manual prop valve is not designed to overcome a mismatched F/R torque bias.

Otherwise, the 4-lug kits are pretty much the same rotor/caliper/mount. Don't expect dramatically shorter stopping distances. Most of the stopping power is on the front - 70+%. And brake dive/rear jacking makes the rear brakes even less useful.

 

[Striker01]

So I can get the ssbc kit and not touch the master or booster ?

With my torque arm set up next year, brake dive should be gone from everyone that I've heard.


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[qtrracer]

IIRC, the SSBC kit includes a M/C if the car is an 87+. Mine is an 86 so the 86 version was fine per SSBC. Used the 86 booster all the way through my Cobra brake upgrade. I also have the MM T/A and used to run a PM3L for a few seasons. The increased spring rate required for either rear suspension also requires more shock rebound control which helps with rear jacking. Still, even with these mods the brake torque bias is still in the 70F/30R ratio. This is fine for the typical weight distribution on a Fox chassis. When we move that weight around, then we need to adjust the bias to account for the new weight distribution. On a Fox chassis with say 53/47 weight distribution, the 70/30 bias is still pretty close; maybe 68/32 for the typical BBK using Cobra rear rotors/calipers.

 

[Striker01]

Thanks for the info! I was told by Jack from MM that my current spring rates are fine for the torque arm. That was my biggest worry. Off topic- how did you find the torque arm on the street?

So the LMR kit would work well based on everything in reading ?


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[qtrracer]

The T/A is fine. Actually, only a little NVH increase from stock, and a lot less than the PM3L I was running. Ride quality is greatly improved even with the heavier springs because all the bind is gone. I started out with H&R Super Race rears that were too soft. Moved up to the H&R version of the MM TA5. Those were better but I was at the top of my Bilstein HD damper valving range. I've since gone with a rear C/O with 200# springs and Race valved Bils, but haven't finished the car yet so don't know how that works.

I haven't looked at the LMR kit but they all use a variation of the Ford M2300C kit (45mm cast iron rear caliper, 10-11/64" (call it 10.25") 4 lug vented rear disc, e-brake cables, prop valve, fox length axle brackets and all fasteners/lines). These are the 93 Cobra or T-Bird Turbo Coupe brakes with the correct bracket for Fox-length axles. Just find the best deal. Sent you a PM.

The system works very well. Just need to get the knee-point bias correct with the prop valve. This is to prevent rear lock before front lock.

 

[Striker01]

The T/A is fine. Actually, only a little NVH increase from stock, and a lot less than the PM3L I was running. Ride quality is greatly improved even with the heavier springs because all the bind is gone. I started out with H&R Super Race rears that were too soft. Moved up to the H&R version of the MM TA5. Those were better but I was at the top of my Bilstein HD damper valving range. I've since gone with a rear C/O with 200# springs and Race valved Bils, but haven't finished the car yet so don't know how that works.



I haven't looked at the LMR kit but they all use a variation of the Ford M2300C kit (45mm cast iron rear caliper, 10-11/64" (call it 10.25") 4 lug vented rear disc, e-brake cables, prop valve, fox length axle brackets and all fasteners/lines). These are the 93 Cobra or T-Bird Turbo Coupe brakes with the correct bracket for Fox-length axles. Just find the best deal. Sent you a PM.



The system works very well. Just need to get the knee-point bias correct with the prop valve. This is to prevent rear lock before front lock.

Saw the PM brother and thank you! I was going to do this come spring time as I just did an entire suspension and new interior on the car so I'm going to need some time to recover lol!

I'm hoping the HR super sports I have for 94-95GTs is a sufficient rear spring for the MM TA. I know Jack already told me so, but I'm a paranoid bastard and don't want to do it twice hopefully!


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[qtrracer]

Jack knows his stuff and his parts. Generally, you want the rear rate to "match" the front rate in terms of wheel rate, or frequency. Wheel rate is easier for me. So, if you have a conventional spring or C/O on the front, that dictates what should be run on the rear with either a conventional or C/O spring. Jack's recommendation is probably based upon your front spring rate, as compared to your conventional rear rate.

In my case, the rear was too soft given the front and you could tell by the way the car handled. I increased the rear but still wanted a decent ride so I was still mismatched. I tried increasing the rate of my adjustable rear bar. While that was OK, it was still mismatched.

Basically, your design reads for ride comfort over handling prowess. That is where I was too. Frankly, the better the car handles the less friendly the ride becomes. As a result, in my experience the car is not as enjoyable to putt around in on those cruise days. So, I give up some handling for ride quality. It's always a trade-off.

 

[Mustang5L5]

So I can get the ssbc kit and not touch the master or booster ?

The SSBC kit is essentially a 1993 cobra setup, so yo should really try and replicate all of the specs of the cobra setup.

That means 1" bore 1993 cobra MC, and the tandem 205mm brake booster upgrade (1993 cobra unit). I beleive the MC comes with the kit for the 87+ cars, but you'll have to source a booster from somewhere like RockAuto

 

[Striker01]

That LMR kit has a lot of bad reviews for install and fitment. I'm not sure if I'll go with that one.

North race cars and ssbc by the looks of it.


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[Striker01]

So the kit from north race cars does not come with the MC from what I'm seeing.

I'm not sure if I should go with the SSBC or NRC kit. I'd also like to upgrade to stoptech sport slotted rotors but I'm not sure what I'm getting rear rotors for (93 cobra?)

Also who makes a performance pad for the mar calipers ? I've read that it's a D347 part number but I can't find anything from Hawk.


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[Mustang5L5]

They are both 1993 cobra rear setups. The SSBC kit comes with the MC, but it's the 1985 town car 1" bore old style MC, which lacks the hookup for the low fluid sensor. To be honest, i'd rather get the 1993 cobra MC and keep the modern looking MC reseviour and low fluid sensor. Figure the 93 cobra MC is $100, and a 3-2 kit from max motorsports is $40. Plus, you should really install the 1993 cobra booster, which is roughly $100.

If you plan on buying different rotors, i would just piece the parts together myself. Price it out first and see what's more cost effective to do. Buy the brackets only from NRC ($160). Hop on Rockauto.com and get two 1993 cobra calipers ($90 each including core), etc etc.

I'd probably just buy the NRC kit, the rotors you want, Ebay off the rotors that come in the kit, and then add a 1993 Cobra MC, a 1993 cobra booster, the 3-2 conversion kit, the prop valve plug, and an adjustable prop valve.

 

[qtrracer]

Hawk as well as most other brake pad suppliers offer pieces for the 93 Cobra/87/88 TB Turbo Coupe. There are several profile numbers but the D347 is the one I generally use. For example: Raybestos (https://www.summitracing.com/parts/.../parts/agb-pg-d347?seid=srese2&cm_mmc=pla-msn-_-shopping-_-srese2-_-raybestos); Hawk (HB580F.627 | Hawk Performance), etc.

Discbrakesrus (discbrakesrus) carries Centric rotors. Centric owns StopTech.

 

[TomR]

I have the North racecars kit and it works fine with Hawk pads and a manual Raybestos MC39568 master cylinder. By using Hawk pads I have perfect proportioning when I lock up **but** I have a drag car with big rear tires. The fronts hit first on my car, and it stops great from 140-145 on short tracks.

 

[Striker01]

They are both 1993 cobra rear setups. The SSBC kit comes with the MC, but it's the 1985 town car 1" bore old style MC, which lacks the hookup for the low fluid sensor. To be honest, i'd rather get the 1993 cobra MC and keep the modern looking MC reseviour and low fluid sensor. Figure the 93 cobra MC is $100, and a 3-2 kit from max motorsports is $40. Plus, you should really install the 1993 cobra booster, which is roughly $100.



If you plan on buying different rotors, i would just piece the parts together myself. Price it out first and see what's more cost effective to do. Buy the brackets only from NRC ($160). Hop on Rockauto.com and get two 1993 cobra calipers ($90 each including core), etc etc.



I'd probably just buy the NRC kit, the rotors you want, Ebay off the rotors that come in the kit, and then add a 1993 Cobra MC, a 1993 cobra booster, the 3-2 conversion kit, the prop valve plug, and an adjustable prop valve.

What's the prop valve plug ?

I'll probably go with the NRC kit and purchase the 93 Cobra MC, the lines from MM, 2 stop tech rotors, hawk hps pads and call it a day.

I heard the cobra booster requires you to hammer in the shock towers a little bit. NOT gonna do that lol.


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[Striker01]

Hawk as well as most other brake pad suppliers offer pieces for the 93 Cobra/87/88 TB Turbo Coupe. There are several profile numbers but the D347 is the one I generally use. For example: Raybestos (https://www.summitracing.com/parts/.../parts/agb-pg-d347?seid=srese2&cm_mmc=pla-msn-_-shopping-_-srese2-_-raybestos); Hawk (HB580F.627 | Hawk Performance), etc.



Discbrakesrus (discbrakesrus) carries Centric rotors. Centric owns StopTech.

Thanks for the pad info! I'll order those up.

Now I gotta find the stoptech rear slotted rotors for the cobra


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[Mustang5L5]

What's the prop valve plug ?

I'll probably go with the NRC kit and purchase the 93 Cobra MC, the lines from MM, 2 stop tech rotors, hawk hps pads and call it a day.

I heard the cobra booster requires you to hammer in the shock towers a little bit. NOT gonna do that lol.


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The plug is used to "gut" the oe combination valve under the MC when you run an adjustable prop valve that installs at the union on the passenger side firewall.

https://lmr.com/item/M2450A/Mustang...ioning-Valve-Plug?gclid=EAIaIQobChMI5YHf4KiU1gIV1lqGCh3VXgAREAQYASABEgKNAfD_BwE


As for the booster, i didn't touch my firewall sliding it into my '88. The 90-later cars have even more room so there really is no need to bash a strut tower. Trim the studs down slightly, slot the 4 holes to the pass side, and loosen the upper intake and slide it off to the side, and you can get the booster in without a hammer.

I personally feel it's needed. The brake system was designed to use the assist provided by the larger booster, so going throught he trouble of converting and not doing the booster is not taking full advantage of the upgrade. The cobra booster offers 2X the assist of the stock fox v8 booster.

 

[bucho65-2]

When I went to rear discs I got the bigger booster also. No hammer needed but I did have to elongate the bottom holes for the booster a little bit. I think I went with a MC for a 94 GT. Looks just like the stock one but 1 1/16" bore. Also did the 73mm front caliper but wouldn't recommend those. 60mm calipers work much better.

Is there a reason you are not converting to 5 and cobra brakes? I'm kicking myself for not doing it when I added the rear discs. Stopping distance did not improve that much but I'm not over heating the drums anymore. Only happened during spirited driving in the canyons.

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