Update: Quick Performance Explorer rear disc conversion

[skrit]

I posted this in an update to another post but thought it might get buried and no responses so I'm starting this new one.

Recently purchased an explorer rear disc conversion for the Torino style Medium Duty Big Bearing 9" housing. One thing I've found is the rotor hat's centering hole is .075 (75 thousandths) too small to fit over the raised center "brake pilot/register/index" of my new Yukon axle shafts. I also tested with the original axle and it's the same issue.

I will not be "turning down" the register of my axles - they are already installed and I'd be lucky to put enough miles on the rear rotors to necessitate replacing them and doing this exercise all over again.

So.... how hard would it be to sand/grind that down? Maybe I just need to take it to my machine shop... it's just such a small amount to take off...opinions?

Was thinking of using my cylinder bore tool since I don't need those stones anymore.

 

[Broncobowsher]

So many ways of doing this. Keeping it true is the hard part.
A lathe would make short work of it. And would be the best option.
Small amount it relative. I look at that as a lot of material to remove. A small cylinder hone would be good if you were just trying to take off 2-3 thou. Fine tune the bore to match the axle.

 

[skrit]

I just realized that it was my fault that the brake register hole is too small. I ordered it without specifying so they came as 2.800" as standard.

My local machine shop said he can use his lathe so I'll nix the idea of a DIY solution.

Any idea how much larger the hole needs to be than the axle's brake register? If the brake register is 2.875 then make it 5 thous bigger to 2.880?

 

[Yeller]

.075 is a lot to use a hone for, you and your drill would be worn out. Personally I’d carry it to the machine shop. That needs to be true so you don’t develope a shimmy like a warped rotor.

I wouldn’t do more than .005 oversize.

 

[skrit]

.075 is a lot to use a hone for, you and your drill would be worn out. Personally I’d carry it to the machine shop. That needs to be true so you don’t develope a shimmy like a warped rotor.

I wouldn’t do more than .005 oversize.

Thanks @Yeller @Broncobowsher @toddz69 for your help.

 

[ntsqd]

When I had to open up the register hole on the Expedition rotors for Snowball's rear D60 I shot for line on line, that is if the register measured 3.000" then I wanted the pilot hole to also measure 3.000"
To hold the rotors in the lathe I used the parking drum surface with a thin piece of aluminum between the rotor and each jaw.

 

[skrit]

When I had to open up the register hole on the Expedition rotors for Snowball's rear D60 I shot for line on line, that is if the register measured 3.000" then I wanted the pilot hole to also measure 3.000"
To hold the rotors in the lathe I used the parking drum surface with a thin piece of aluminum between the rotor and each jaw.

Thanks. I dropped them off at the machine shop along with my exact axle register diameter along with the actual caliper scale I used to measure it with locked into place. Told him 1-2 thous bigger just so I wouldn't have to beat the rotor on. Hope he does'nt F them up.

 

[Apogee]

Just my experience, but you do not want a nominal "perfect" fit, as rarely do Ø3.000" pins slide into Ø3.000" holes, even with big hammers, presses, heat, etc. It might sound good on paper, but holes aren't necessarily perfectly round because perfect only exists in theory, everything has a tolerance associated with it, and it doesn't take much interference at all to make something completely "uninstallable" by hand when working with metal/iron.

That said, a +.002" to +.004" slip fit will typically not only install well, but will uninstall later by hand if needed, without excessive force or tools required. I modify my fair share of rotors for my work, and we typically interpolate the bores in the milling machine while adding different wheel patterns, but a lathe would be a good option as well.

FWIW, I would have modified the axles...one and done, over the counter rotor options in the future...you never know and I try to never say never.

 

[skrit]

Just my experience, but you do not want a nominal "perfect" fit, as rarely do Ø3.000" pins slide into Ø3.000" holes, even with big hammers, presses, heat, etc. It might sound good on paper, but holes aren't necessarily perfectly round because perfect only exists in theory, everything has a tolerance associated with it, and it doesn't take much interference at all to make something completely "uninstallable" by hand when working with metal/iron.

That said, a +.002" to +.004" slip fit will typically not only install well, but will uninstall later by hand if needed, without excessive force or tools required. I modify my fair share of rotors for my work, and we typically interpolate the bores in the milling machine while adding different wheel patterns, but a lathe would be a good option as well.

FWIW, I would have modified the axles...one and done, over the counter rotor options in the future...you never know and I try to never say never.

Thanks, my machine shop just finished opening them up a little on a lathe. Axle register was measured at 2.865. Machinist enlarged rotor hole is 2.890 which I think will be fine. When I pick them up I will provide an update on the fit. He asked how much larger and I said maybe 5 thous. He said I needed to go a bit larger for the exact reasons you explained - install and removal.

 

[Apogee]

Thanks, my machine shop just finished opening them up a little on a lathe. Axle register was measured at 2.865. Machinist enlarged rotor hole is 2.890 which I think will be fine. When I pick them up I will provide an update on the fit. He asked how much larger and I said maybe 5 thous. He said I needed to go a bit larger for the exact reasons you explained - install and removal.

Cool, I'm sure the .005" slip fit will work fine. When fitting circular male/female parts, it's important to note that a .005" total difference in diameters will only result in a maximum of .0025" runout, so while neither number is necessarily problematic, it will be half the .005" difference at most, and more likely less than that due to roundness and such.

 

[Broncobowsher]

If a touch tight, the cylinder hose could take off that extra thou or so.

 

[skrit]

Update:

Just got the rotors back and they fit perfect with no slop. Handed over $75 cash to my guy.

I wrestled with the calipers because they were being A holes. I ended up pulling the rubber boot back towards the outside because they were getting bound up on the backing plate mounts. I even confirmed I have daylight between the pads and the rotor. Hopefully i didn't install them upside down.

And BTW, I clear coated the Axle flange

 

[skrit]

A few more pics. I've heard red calipers each give about 20 hp more.

 

[ntsqd]

A few more pics. I've heard red calipers each give about 20 hp more. View attachment 931278

Only on the Ghetto Dyno.

 

[toddz69]

A few more pics. I've heard red calipers each give about 20 hp more. View attachment 931277 View attachment 931278

Do you have the little stainless (I think) pieces that go on the caliper mounts where the pads slide? I don't see them in these pics.

Todd Z.

 

[skrit]

Do you have the little stainless (I think) pieces that go on the caliper mounts where the pads slide? I don't see them in these pics.

Todd Z.

no - they weren't provided. Not sure why. I'm wondering if I even need them as there's very little lateral movement - like less than a 1/4".

 

[skrit]

I'm starting to have doubts about this install. Why is there so little clearance on the slider and why did I have to pull the boot out to get it to fit on both sides? I'm wondering how I can push the axle in farther but I'm not so sure it can go in any farther. The retainer is torqued to spec and before I did that I hit it with a few blows of a rubber mallet and did not see any inward movement. Everything is splined together and spins. There is nothing on the back side of the backing plate interfering - it's flush against the axle ends. The rotor is flush with the axle flange. See below - what do ya'll think? (I've reached out to Quick for their thoughts using this picture)

I used the provided spacer "B" which sits here but don't see how that could cause the issue since it's inside the axle end:

 

[Yeller]

The last one I installed was very close like yours, its working fine. Any consolation, it will get more in line as the pads wear.

 

[skrit]

The last one I installed was very close like yours, its working fine. Any consolation, it will get more in line as the pads wear.

true - thanks for sharing that @Yeller

 

[Wild horse 75]

Check the outer register on the axle. If there isn’t a chamfer on it you’ll need to add one. The drum inside doesn’t have a square corner and it will prevent the rotor from fully seating against the axle flange.