Joined: Thu Oct 13 2005, 08:23PM
Location: Beautiful Down Town Roebuck Ontario
Posts: 227
Get a set of 69-72 spindles. The 2 pce rotors are 3x the price but everything else is the same. Dr Diff http://www.doctordiff.com/ makes spacer sleeves for the inner bearing to convert the early spindle to accept the unicast rotor but he doesn't do the outer yet. Any decent machine shop could make a pair pretty reasonable tho. He also has a grease seal that will work.
Joined: Wed Dec 21 2005, 07:34AM
Location: indiana
Posts: 791
I agree. Bearing spacers would require a lot of precision and knowledge of interference fitments so that spacers don't slip and gall the spindle. Seals require a suitable micro-finish to seal and also to survive. Lots of room for error and/or 'performance issues'.
Safest bet, if you can't find '73 stuff, is to get 69-71 spindles and just spend the extra $200 on rotors. I've researched lots of stuff on mix-match parts to find that Holy Grail of cheap aftermarket parts (with no luck, always 1 piece missing). If I had spent that amount of time at a part-time job, I would've earned enough $$ for the $150 rotors for me (and a few other folks to boot).
I think you have to go to 15" wheels with these, have to call them to be sure. When I talked to them at a show that's what I remember them saying but I might be wrong, seems the rotor was close to a 12" one.
The SSBC kits all take a 14" wheel ( 11.25 rotors ) But are all at least 300 more.
Or like said use a 69-71 setup & just have a bit more in rotor cost only, Don't think you'll ever wear out the rotors anyway no more than we drive these things.
But that requires a 15" wheel too ( 11.75 rotor ) and I wasn't sure you wanted to change?
That ECI kit looks pretty nice- especially the hub that solves all the bearing fitment issues. (I like it better than the new Scarebird version with the machined bearing spacer). If I didn't already have '73 discs I'd consider this one.
Joined: Wed Dec 21 2005, 07:34AM
Location: indiana
Posts: 791
I�m gonna chime in again, I said something similar to this in another thread somewhere. This is to everybody in general and nobody in particular. This is long but I think it�s worth the read (some of what I say refers to the Mopar Action article on the latest Scarebird kit -- I am not meaning to criticize them directly, I merely want to plant seeds of thought into anyone considering non-factory brakes).
There can be a huge difference between parts that fit together vs parts that actually work well together and give a long service life.
I spent 8 years as an application engineer, which generally involves choosing off-shelf items and assembling them into a working system. Using that background I've researched **lots** of component specs to find that Holy Grail of cheap aftermarket parts to use the 65-71 drum and 69-71 disk spindles with cheaper rotors (and also to find a suitable smaller setup to fit a C with 14� wheels). I�ve had no luck, there�s always 1 puzzle piece missing that keeps it from being an �engineered system�. If I had spent that amount of time at a part-time job instead, I would've earned enough $$ to buy the $150 rotors (and a few spares, too). I encourage everyone to contemplate that statement � these are your brakes you�re trying to save a few bucks on � what is your car (or maybe your or someone else�s life) worth???
So I now work as a test engineer (4 years and counting) and am learning about the subtle design details that can make or break a long service life (in addition to being safe!). So for a magazine proclaiming that a kit is a good product merely because they were able to install it and drive an 8000-mile road trip � well, call me a cynic, I am not convinced by that. Instead, show me 8000 stopping events, at hot and cold temperature extremes, and across multiple test samples, and then I�ll think they�re on to something. If such design and testing data exists with the various �aftermarket kits� I�ve yet to see it.
Some specific thoughts: Bearing spacers would require a lot of precision and knowledge of interference fitments so that spacers can be installed easily, fit the bearing race ID, but not slip and gall the spindle. Furthermore, seals require a suitable micro-finish to seal properly and also to survive the sliding friction during rotation. In my opinion, there is lots of room for error and/or 'performance issues' with such a one-piece machined part.
The Ford rotors are slightly smaller in diameter and thinner, so they�ll be more likely to warp than the Mopar ones (I�m not saying they will, just that there is the theoretical propensity for it). They might be cheaper, but will they last as long? Only time would tell, and we haven't gotten that feedback yet on the Scarebird kit.
It looks like the A6 inner bearing would fit the Mopar spindle and also the Ford rotor (although the rotor calls for an A13), so I thought that might be a step in the right direction (although I would need to confirm that the bearings are equally spaced between the 2 rotors). The seal, however, is a different story. The bore on the Ford rotor is larger than the Mopar, and the sealing surface diameters are different also. I reviewed the Timken/National Seal automotive catalog and there is no seal that would convert between the 2 (not even by going a little �tighter� on the seal diameter, which could be a questionable decision). The seal issue is apparently the reason for the spacer that Scarebird supplies. The same issue arose during my quest for discs for 14� wheels (ironically, the best options in 10� rotors for that application also used the same seal as the Ford).
I don�t want to rain on anyone�s parade. I believe that if you�re creating an oversize brake system for your car, or installing disks on something that never had it as a factory option, it�s understandable and justified to try the mix-match and custom parts route (especially if you can get 100% off-shelf components). But if you�re merely trying to get 11.75� discs on the front of a C-body, just spend the $ and get 69-71 or 73 spindles, get the corresponding rotors, and use the factory-engineered / factory-tested system. There are millions and millions of miles of validation, back in the day thru the current day, to back you up.
Joined: Thu Oct 13 2005, 08:23PM
Location: Beautiful Down Town Roebuck Ontario
Posts: 227
I wouldn't be too concerned about the spacer galling the spindle because the original bearing was a slip fit and it doesn't gall (unless the bearing seized). Just machine the spacer to the same clearance the bearing used. Dr Diff uses an oil pump seal from a 700r4 which apparently has the right dimensions. Herman (the guy from Holland) made his own spacers and turned a shoulder with a radius on the inner side so the bearing actually keeps the spacer located. All that being said it is likely just as easy to shell out the extra $$ dor the 2 pce rotor.
Joined: Wed Dec 21 2005, 07:34AM
Location: indiana
Posts: 791
I agree with you, somewhat. What I'd be concerned about is you now have 2 interfaces compared to the original's 1. The race doesn't gall on the spindle because it doesn't move because the bearing rolls instead. However, now you'll have 2 interfaces - race to spacer and spacer to spindle.
Yeah, the bearing still rolls easiest with the spacer, but unless that spacer is a near-perfect fit, there will be some relative motion at the surface contact (especially during braking and cornering), and with no lube there will be some wear (especially as diametral differences would lead to line contact ILO surface contact).
Further, if there is a hardness mismatch between the 2 interfaces, something's gotta give (probably the spacer as I'd doubt they are CNC machining it from a hardened material or heat treating it afterward). Maybe not today, not tomorrow, but eventually.
There has not been any official long-term and/or structured testing - so until they publish differently, I'm still skeptical.
Joined: Thu Oct 13 2005, 08:23PM
Location: Beautiful Down Town Roebuck Ontario
Posts: 227
I see your concern, I just don't agree that it is warranted. The original spindle/bearing arrangement is built to mass production tolerances that is to say not perfect. More like barely close enough altho I haven't actually measured the clearance. The fact that the bearing will slide on the spindle without any fuss means it has many thou of clearance. As for the spacer turning with no lube, it has no more reason to turn than the bearing does and if it did, it has the same lube that the bearing has on the spindle and that is almost none.
The one concern I would have tho is how the spacer stays located on the spindle. The outer one isn't a problem as it can't get past the nut, but if the inner worked its way to the outside and out of the bearing, it could cause some grief. If I go this route with mine I think the solution to that will be three pronged. Turn the sleeve with a radius shoulder (filet?) on its OD inside, stake the spindle and 2 small tack welds tig'ed at 12 and 6 o'clock just for overkill. I don't know what alloy the spindle is made from but being a massed production part it's likely not too exotic so spacers made from stainless should stand up at least as well.