| 80mm Calipers [message #98639] |
Sun, 05 September 2010 12:18  |
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JShot
Messages: 485
Registered: October 2006
Location: NW Ohio
Karma: 0
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Senior Member |
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Replacing the front calipers with new aftermarket 80mm calipers.
The caliper is in place, and secured with the two Allen head bolts.
The new pads still have a gap between them and the rotor and you can 'rattle' them.
No brake lines hooked up to the caliper yet.
Should I be able to manually slide the caliper in and out by hand, even an 1/8"? The part of the caliper that the tip of the securing bolt goes into (not the threaded end of the bolt) has some rubber in it so the bolt tip is really tight in the caliper.
Confused again in NW Ohio
John
John Shotwell
Ridgeville Corners, OH
78 Royale Center Kitchen
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| Re: [GMCnet] 80mm Calipers [message #98643 is a reply to message #98639] |
Sun, 05 September 2010 12:41  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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John, If the calipers are new and not reconditioned, the allen head bolts
should be quite tight in the rubber bushings, but you should be able to move
the assembly towards you and away from you some distance. Varies with
application. The pads will have space between the rotor and the caliper
until you apply hydraulic pressure to them and bleed the bubbles out. Some
of the 80 MM calipers have appendages on them that interfere with the back
of the wheel rim. Check this spacing extremely carefully, and grind off the
part of the caliper that interferes. Don't forget to lubricate the allen
bolts with the approved grease. Some of the chassis lubes will swell up the
rubber bushings. You didn't say if the rotors were new or reconditioned but
if they are new and are chinese or korean check the runout with a dial
indicator. If they don't runout within .002", have them machined. Brakes on
heavy vehicles are more important than any other system including the engine
and transmission. Do it once, using the highest quality parts that you can
afford, keep it squeaky clean, work deliberately and sober, and don't be
ashamed to ask for advise. The only stupid question is the one that doesn't
get asked.
Feel free to contact me off net if you want more details.
Jim Hupy
Salem, Or
78 Royale 403
On Sun, Sep 5, 2010 at 10:18 AM, John Shotwell <jshot@rtecexpress.net>wrote:
>
>
> Replacing the front calipers with new aftermarket 80mm calipers.
>
> The caliper is in place, and secured with the two Allen head bolts.
>
> The new pads still have a gap between them and the rotor and you can
> 'rattle' them.
>
> No brake lines hooked up to the caliper yet.
>
> Should I be able to manually slide the caliper in and out by hand, even an
> 1/8"? The part of the caliper that the tip of the securing bolt goes into
> (not the threaded end of the bolt) has some rubber in it so the bolt tip is
> really tight in the caliper.
>
> Confused again in NW Ohio
>
> John
> --
> John Shotwell
> Archbold, OH
> 78 Royale Center Kitchen
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] 80mm Calipers [message #98647 is a reply to message #98639] |
Sun, 05 September 2010 13:29 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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John,
Did you modify the caliper my removing the cast boss left of center
above the piston.
See pictures:
http://www.gmcmotorhome.com/commodore/front_brake/index.html
JR Wright
>
>
> Replacing the front calipers with new aftermarket 80mm calipers.
>
> The caliper is in place, and secured with the two Allen head bolts.
>
> The new pads still have a gap between them and the rotor and you can
> 'rattle' them.
>
> No brake lines hooked up to the caliper yet.
>
> Should I be able to manually slide the caliper in and out by hand,
> even an 1/8"? The part of the caliper that the tip of the securing
> bolt goes into (not the threaded end of the bolt) has some rubber in
> it so the bolt tip is really tight in the caliper.
>
> Confused again in NW Ohio
>
> John
> --
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] 80mm Calipers [message #98653 is a reply to message #98648] |
Sun, 05 September 2010 14:22 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I have that silicone grease on the pins before with good results. The grease
is a dust magnet, so use it on the areas where the rubber bushing travels.
No need to do the whole shaft. I have some wagner-lockheed brake assembly
lube that looks like jelly and smells like brake fluid. Hardly anyone
rebuilds calipers or wheel cylinders anymore in the trade. Mostly use pre
loaded calipers and new wheel cylinders and MC's. Cuts down on labor and
transfers some of the responsibility (read that $ liability) to the
rebuilder suppliers. My personal bias against using anything with silicone
in it stems from the fact that is you have ANY of it on your hands or shop
rags and you touch or wipe any part that needs to be painted, it will cause
fish eyes in the paint like you wouldn't believe, and nothing will stick to
it, ever. I was not referring to the smoothness of the rotor, but the runout
or wobble. Be sure to check the thickness, many times they have been turned
below safe wear limits. Most OEM calipers have the minimum allowable
thickness cast into the rotor. If in doubt, check the Manual for specs. Also
sometimes too smooth a contact surface on the rotors will be difficult to
break in new pads, so rough them up with 120 grit abrasive cloth and check
for heat affected spots and cracks in the surface.
Jim Hupy
Salem, Or
78 Royale 403
On Sun, Sep 5, 2010 at 11:52 AM, John Shotwell <jshot@rtecexpress.net>wrote:
>
>
> Jim and JR,
>
> Thanks for the replies.
>
> The calipers came from a lady whose husband had died - an old GMC'er - she
> was selling a lot of his parts at Calhoun this year. He had already ground
> off the 'appendage'. The calipers came with new PF pads, new brake lines
> with banjo bolts and washers, new pins, etc. - everything is there to do the
> complete job.
>
> Except 'grease'. I was going to use a silicone grease from a tube - looks
> almost like Vasoline - is that OK? The guy at Napa said that's what they
> sell for this operation. And should the whole length (except the threads) of
> the bolts be lubed?
>
> The rotors are original and very smooth, not at all grooved.
>
> John
>
>
>
> --
> John Shotwell
> Archbold, OH
> 78 Royale Center Kitchen
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] 80mm Calipers [message #98900 is a reply to message #98653] |
Tue, 07 September 2010 21:15 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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On the 80mm caliper note;
I just bought 80 mm calipers from O-Reily, they came with pins.
Thought that was nice.
They also have Performance friction pads 
I'm starting to like them, but their CV boots suck
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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