Hi all. Making the swap from my factory discs to the larger 11.75 rotors is something I've been thinking about for a while. I've done a lot of thread searching and come up with lots of info for drum to disc, but not disc up sizing. My stock brakes have never let me down but I do have, and plan to keep, bigger/heavier aftermarket wheels and tires. So I'd like to look at making improvements. Vehicle is my signature car. '71 Satellite with 408/904 and 8.75 with 3.23 SG.

So what parts are needed for the swap?

Thanks
roe

Rotors, caliper adapter to match your existing calipers.

You may wish to put new bearings in the new rotors, add bearings and seals.

That's it. Oh and 15" rims

Do you think the minor difference in diameter will have a noticeable impact in braking?

I just put in new bearings a couple of years ago, so I'd probably just inspect and repack if needed.

Everything that I've read has said there will be an improvement, especially in repeated stops and controlling fade. I'm trying to inch my way towards overall car completion. Rear discs and rear swaybar would be next. I want to work towards having someg fun safely on closed course with some curves and corners in the old boat. Nothing competitive, just fun.

The contact area is the same on both size discs since they use the same rotors and pads. The difference will be the "leverage" of the larger diameter rotor - which is less than 1" !! Circumference-wise the larger rotors are roughly 2.5" larger - less than a 10% increase.

Personally I don't think its a worthwhile swap to go from 10.87 to 11.75 unless you're converting from drums or old-style discs. The 10.87 caliper adapters are more abundant and less expensive. Seems anyone with a set of 11.75 adapters these days wants stupid money.

If your end goal is big stopping power then save your pennies now and do it right later on.

If you have 71 spindles, your gonna, hafta, change your spindles to 73 up spindles, because the larger rotors use a larger diameter inner wheel bearing.
Or the bearing, spindle spacer, that Dr, Diff sells on his internet web site.

So since what I have has been performing well would you guys recommend going straight to a 13" setup when I change? I'm not opposed to that because any wheel I use will fit over them easily. Smallest wheel I'd use is an 18". I also don't wanna over do it just because. I won't do any competitive stuff, just some courses for fun. The other 99% of time will be street driven.

I do have '71 spindles. If it's a matter of getting a caliper adapter and the spacer and driving away then that sounds good to me as long as those parts aren't stupid money. I've bought from drdiff before and his prices were reasonable. Does he still sell the caliper adapter too?

Just did this over the past winter. Used new '79 Diplomat rotors.
Got the caliper brackets from Dr. Diff. Truthfully, don't see much of a difference is stopping power, but they'er on now and I'm not taking them off.

Have you done any repeated high speed braking? Or have you had an emergency stop since the change.

I think I may see improvement where others may not have because of my wheel/tire combo. What's on here now is a 22" rim and tire. My next set will be a 18"front and 20"rear Torque Thrust II type wheel. Still fairly heavy I would assume.

What do you think?

Stanton made on "on paper" observation and 68lar an in use observation & both reported minimal gain. what about trying "right now" some agressive (ceramic?) pads and the important part a bed in procedure?. I used some good pads (not sure if they were ceramic) but they were aftermarket on a 10.87 setup & granted all I do is putt around town like an old fart but the braking force seemed more than adequate (& I did not bed em in) which reportedly make a very significant difference. might even check into a rougher surface of the rotors for more grab (talk to some brake lathe operators in the know)

Where can I find some ceramics? I hear good things about them but haven't tried them.

The usual places I go only seem to have semi metallic.

A quick Google search brought me to this page. http://www.carid.com/1971-plymouth-satellite-performance-brake-pads/

I'm thinking of trying the EBC Red or Yellow pads, or the Hawk performance street pads. The EBC Yellow pads are a race application. Will they be too aggressive and cause premature rotor wear.

Maybe I should also look at a bolt on rotor replacement to something better as well. Is drilled and slotted worthwhile?

I believe I got ceramics from RockAuto. Possibly Autozone or Advanced. Either way, they weren't hard to come by.

I dont think slotted/drilled would give you what you are looking for. I also would not sweat rotor wear. I would call several of those companies & outline what you are after & see what they recommend. I think with some proper pads (with or without a rougher turn on the rotors) that you will be upgraded. (also see what they say on the bed in for their particular pad type)

Thanks gentlemen. I'll call autozone and see if they can pull up stuff that I can't see on their website. If not I'll source some. Surprisingly rockauto.com is a dead end too.

So far about 14 passes down the 1/4 mile. So, yea, a few high speed passes. 15" wheel all around. 'Not into those larger wheels on an old muscle car..

Thanks for the real world data. Everything I read led me to believe that I would see an improvement, just not a huge one. I'll try the better pads and save up for a 13" or so front rotor and a rear discs at the same time. It'll probably keep me from doing it twice too. I'm sure that will get me by till I get to have some fun in the twisties.

I'm a fan of variation. I've done stock steel wheels, 15" period correct after markets and now big after markets with low profile tires. Next I'll mix the two and go 18-20" rim with a classic look and a low profile. I really like how the low profiles handle. Add in a rear sway bar, good discs on all 4 corners, stiffening platest on LCAs, firm feel box, tubular UCAs, and a few other upgrades and I think this behemoth will be fun to push some curves.

So based on what I want to do with the car, weight, etc...concensus was to save towards something better than just the factory 11.75 discs.

So I've been looking at Drdiff'so kits and was thinking about the the 13" cobra kit for the front and the 10.7" rear kit. I think that would do well.

But would I need to do that instead of going 11.75 front and 10.7 rear? This would save me some cash for not needing to buy the full front kit. I could re-use my current spindle and caliper and just buy the front rotor/spacer/adapter/bearings. How do you guys thing the two different setups would do for me with mostly street driving and the occasional twisties course?

11.75 front with stock calipers and 10.7 rear kit

Or

13" front and 10.7 rear kit

Keep in mind I would do upgraded pads like previously recommended in this thread.

Or should I look at keeping my 10.87 discs, upgrade the pads and go with a 10.7 rear kit?

I know I'm all over the map but I need some input from folks who know more than me for all of the ideas in my head.

Thx
roe

I think spending your money on rear discs is the last upgrade, not the first.

I've searched and read so many disc brake threads my brain is mush. It seems there is no consensus on the best approach. Some say the 11.75 was night and day from 10.87. Others say it wasn't worth it. I'm honestly confused as to which way to go.

Maybe save my pennies and just go 13" cobra kit up front and keep the rear drums for a while?

I run the 11.75" rotors with organic pads in the front and 11x2.5" drums in the back on my 65 Cuda, ran the same combo on my 87 Diplomat.

They work great in both applications.

I am not, however, running 150mph laps at a race track, nor am I doing the quarter mile in 8 seconds.

And unless you are doing those things you do not need anything more than what I run. Unless you want to "name drop".

I'm not doing either of those, but will eventually hit the twisties for fun.

One thing I overlooked is that the caliper adapters he sells are for sliders and I have pin type so I would have to buy calipers. If I have to replace the calipers anyway then I'd upgrade to the viper calipers like the kits that I think Andy sells.

Ohh....so many choices. But that's a good thing I guess. I'll keep reading and make a choice eventually.

Here are the ceramic pads I bought for the disc conversion - pin-style calipers.