I know. Another Disc Brake Conversion thread, but humor me, please.

I have read ALL of the disc brake conversation threads and the pros and cons of front wheel only, converting all four, drop spindles, etc., and I am probably more confused than before.

Here is what I want to do. I do not need my '68 Cutlass convertible to drive like a modern car, but I would like it to brake and handle a little better for safety. I am having a shop replace all of the bushings with polyurethane. I am adding boxed rear control arms and a sway bar in back. I am having them replace all the ball joints and shocks, and I am also upgrading the steering box to a CPP faster ratio unit. I am leaving the drum brakes on the rear and just having the shop replace the brake lines.

Now to the brakes. I want to change the front to disc, but I want to keep the 14" SSII wheels. I am thinking that I go with one of these kits:
Right Stuff Detailing AFXDC14
https://www.summitracing.com/parts/rsd-afxdc14
Right Stuff Detailing AFXDC02D
https://www.summitracing.com/parts/rsd-afxdc01d

These seem more or less the same except that the second one comes with a 2" drop spindle.

My questions for you:
1) Does anyone seem any problem with these kits for what I want to do?
2) Will the 2" drop work well with the rest of the suspension, or would the suspension need or benefit from other changes such as different ball joints?

Thanks in advance.

 

People who get a 2" drop spindle do it for the look (stance). It probably doesn't contribute much to handling. It does however make you more likely to bottom out driving over bumps and going up driveways. If;s really a personal decision.

The best thing you can do for handling besides what you mentioned above is to get sticky wide tires. If handling is your #1 priority get 60 or 65 series tire on 16+ rims. Try to keep your original tire diameter so you don't have to deal with a speedometer change and RPM doesn't change on the highway. Go for some expensive modern sticky performance tires. Don't get the TA radials, Dunlop or MT radials everyone is buying in 15" sizes. They are old technology and will handle like a 1970s-1980s car.

I am not sure but you could search the group, but factory disk brakes are more likely to give you a better engineered (more likely to work right) solution than aftermarket. I believe the more common 70-72 factory brake hardware will bolt on to your 68. So a combination of junkyard and rockauto parts should work well.

 

Thanks for the feedback. I would not mind changing the stance a little bit, but it is not really a priority.

Handling is probably my least concern other than I do not want the changes to lead to an overly tight or twitchy steering response. I am hoping that the faster ratio power steering box, poly bushings and new roll bars will be an improvement over stock.

I was just looking at some old articles, and Road Test Magazine tested a 68 Cutlass with standard drum brakes. They averaged around 165 feet to stop from 60 mph. Popular Science tested a similar Cutlass but with front disc, and it averaged 172 feet to stop from 60 mph due to excessive rear wheel lockup causing them to have to pump the brakes more to control the stop.

If I am keeping the stock 14" wheels, perhaps I am better off just keeping the drums. I am guessing that to get much shorter stopping distances, I would really need much larger rotors front and rear, but this would require new wheels and tires. My car will be a fair weather cruiser, not an autocross racer or daily driver in the rain, so I am not too worried about brake fade or wet weather performance.

 

The drop spindle will likely cause a problem with the 14" wheels. The lower ball joint and outboard end of the lower control arm get awfully close to the inside of the rim due to the drop.

 

That settles that. I am definitely not going to do that.

Much appreciated, Joe. Any opinion on the front disc kit, or do you think I'd be better off just refreshing the drums all around?

 

I've used the stock-style mini-kit from Right Stuff. It basically replicates the OEM 1969-72 single piston disc brakes. The mini-kit includes the spindles, splash shields, and caliper brackets. I get the heavy cast iron parts (rotors, calipers, and M/C) locally to save shipping, but RockAuto works also. Use the brass GM-style combo valve that's available everywhere (PV2 style). Hoses, wheel bearings, and caliper mounting hardware are available everywhere. The frame brackets for the brake hoses are available from the repro houses. I bend my own lines.

 

Thank you, Joe!

 

I didn't see anywhere that you have changed or intend to change the springs. New springs can make a drastic difference in how the car rides and handles. I swapped out the original 40+ year old springs on my car for heavier duty FE-2 springs (Moog 5536 front, 5409 equivalent rear) and the car handles much better, while still maintaining a comfortable, smooth ride quality. Interestingly, the front height didn't change as the new springs kept the same ride height as the worn out originals (they are much stiffer).

 

That is a good point. I will almost certainly have them replace the springs, but I had not given any consideration to what to buy as a replacement.

 

Frankly I like the moog cargo coils for the rears. They are progressive springs normal pressure at normal but when compressed they get stiffer. Maintains the same good ride but when cornering hard they minimize body roll.

 

That sounds ideal. Thanks!

 

Is this the kit that you are referring to ?

 

Yes, that's it. Last time I bought one a few years ago at Carlisle it was $175 or so.

 

Hi Joe -
Seems like you hit the nail on the head... I just had my mechanic replace my original DRUM front brakes with the "Leed Brakes conversion kit (LEB-FC1002SM) . Lo and behold, the rims are verrry close to brake assembly. A little grinding may tide me over for the original rims... but here's the fly in the ointment.... I just bought NEW RIMS (not oems but rather very close look-alikes). These new rims lock up when mounted. One might assume we could just grind a little more off of the associated parts but in this case, it is most likely way too much to grind off. Any suggestions short of replacing my 14" wheels ? I'm stuck now since new rims would mean new tires... (15") . ugh.
My question might be... is there any kind of adapter or spacer that would be safe and acceptable we could apply to this conversion? (Maybe there's something that can get me over the hump and still use the new rims.)

Sadly, I feel that I wrongly trusted that the Leed kit would work ok -- (the Right Stuff kit currently has way too long a lead time to consider and others didn't include the spindles).

Thanks so much for all your help!

 

Sorry, I did not see this threaded before. You needed to get a brake template from Leed. I used Baer brake template for the 13'' rotors for my fronts, that required 17'' rims. And flush air valves.


Maybe a thin spacer will work. Without hitting fender. You have any pictures. Get a brake template from Leed to be sure that the next rims will work. You may have to sell 14'' ones. For larger rims or 14'' rim that the brake template will fit. And keep the tires.
https://baer.com/Wheel-Spacers-machi...llet-aluminum/