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Replacing rotor question.

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TR4nut

TR4nut

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I picked up some new rotors a while back and it looks like I'm about to put them into use.

My existing crusty looking passenger side rotor has been grabbing badly, I measure 0.004-5 runout which is about double the acceptable spec. Bearings feel tight (no play), but when I drive I get a lot of noise I think from the pads moving as there are no rattle clips or anti-squeal shims on at the time.

Anyway, I was thinking to just swap out the rotor set and see how things behave before doing anything more involved. Couple of questions:

1) The rotors as boxed have milled faces, lots of concentric rings on the surface of the rotors from machining. Is this typical, or is it good practice to turn even new rotors for the installation? My thought is not to worry about it, and just check runout after installation

2) Rotor bolts - I was planning on replacing lock washers only, and retorquing. Bad idea?

Thanks,
Randy
 
Hi There Randy,

In my opinion the milled faces are just fine! The cutter marks actually disburse the heat in various directions.

Relative to the Bolts???????

Best Wishes,

Russ
 
I have never changed the caliper or rotor bolts on my TR3A in 180,000 miles over 50 years, although I have had them apart numerous times. If yours unscrew without undue force and if the hex heads are not rounded, I'd re-use them.
 
The machine marks are normal. If you desire there is a tool for scratching the surface in a non-directional swirl that helps setting in pads. Re-using bolts is OK, I usually replace lock washers and use mild loctite. Centralize the caliper over rotor so pads wear evenly.
 
Good advice and thanks. I bit the bullet and decided to put on the fancy rotors &pads (EBC) I had been saving for the future frame off work (which may always be in the future).
IMG_1971Small.jpg

I reused the bolts, but used fresh lock washers. I was surprised, but according to the manual the torque on the rotor bolts was 32-35 ftlbs. I torqued it up just a hair more because that seemed pretty mild.

Not sure how to centralize the caliper exactly, but since I went with fresh pads I used two c clamps and bottomed both pistons initially. The caliper itself on this car is fixed based on how I see it is bolted to caliper mount.

Hard to check runout with the dimples and all, but they checked okay, and my couple of miles on them were a lot quieter and the brakes aren't pulsing anymore. Also put on the anti-squeal pads which were missing - the main reason I tore everything down because the pads were clicking so badly I thought I was losing a wheel.

Randy
 
TR4nut said:
Not sure how to centralize the caliper exactly,
Click to expand...
The only centralization required is done with shims between the caliper and it's mounting bracket; only if the rotor is significantly off-center in the slot. The pistons will take care of themselves, the first time you use the brakes (which should always be done _before_ you need them).
 
TR3driver said:
TR4nut said:
Not sure how to centralize the caliper exactly,
Click to expand...
The only centralization required is done with shims between the caliper and it's mounting bracket; only if the rotor is significantly off-center in the slot. The pistons will take care of themselves, the first time you use the brakes (which should always be done _before_ you need them).
Click to expand...

Yep, that's what I thought and how I did it. Pumped the brakes after setting the caliper back in place on each side.

I think the restrictor valve may be the next thing to eliminate, seems like it keeps too much residual pressure on the valves. I was a little surprised when I initially pushed back one of the pistons, then realized the other piston was coming out - my guess it was due to the difficulty getting fluid past that valve.

Randy
 
TR4nut said:
I think the restrictor valve may be the next thing to eliminate, seems like it keeps too much residual pressure on the valves.
Click to expand...
That's what many people (including myself) do. I think even the factory eliminated the valve, a few years after your car.

But keep in mind you may have a low pedal after sprited driving or not using the brakes for awhile. That's what the RPV was supposed to prevent.
 
With brake fluid absorbing moisture over time, the spring in the restrictor valve tends to rust, which is not good in the hydraulic system. Figuring they hadn't been touched since they left the factory, I have dismantled and carefully cleaned up a few of them (during car rebuilds) with a soft bristled wire brush

They were dropped sometime during TR4A production, so obviously the factory considered that at least the cars with the later type TR4 disc brakes could do without them.

Regards,

Viv.
 
Randy,
Your new rotors look great. I like seeing pictures of other people working on their cars! Although now I feel guilty and will shortly be heading out to the garage.
The restrictor valves do tend to gum up over time. I would be inclined to keep it, but take it apart and give it a good clean. I have done this on several cars to good effect.
Also on my Triumph Dolomite the front brakes started to drag, which turned out to be the first signs of the master cylinder seals starting to fail.
Nick
 
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