Resurfacing rotors

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Pb9717
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Resurfacing rotors

#1

Post by Pb9717 »

In discussions with a knowledgeable friend regarding my GL1100, I had asked about resurfacing the rotors as they’re 39 years old. He stated that the rotors don’t have enough material to permit a resurfacing and the resurfaced rotor would be too thin to be considered safe. I ended up purchasing a used rotor in good condition rather than resurfacing the damaged rotor caused by a caliper lock up.

Have any of you resurfaced a rotor and what’s been the outcome?
(2) 82' GL1100's
99' Triumph Thunderbird Sport 900
2006 Triumph Speed Triple
Cincinnati OH USA
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Re: Resurfacing rotors

#2

Post by Rat »

Check the threads at the bottom of the page ...

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Re: Resurfacing rotors

#3

Post by MikeNTexas »

I sent the rotors from my 1975 GL1000 to https://truedisk.net/. They did a great job and an amazingly fast turn around.
D8D7163A-8250-4841-8B6E-C72A0DE83E95.jpeg
D8D7163A-8250-4841-8B6E-C72A0DE83E95.jpeg (222.37 KiB) Viewed 222 times
1975 GL1000 Restored (sold)
1983 GL1100 Custom (sold)
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flyin900
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Re: Resurfacing rotors

#4

Post by flyin900 »

Used same shop recently at $45 US per rotor and excellent service and quick turnaround as noted.

P1070623.JPG
P1070623.JPG (123.81 KiB) Viewed 213 times
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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Sidecar Bob
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Re: Resurfacing rotors

#5

Post by Sidecar Bob »

As I mentioned elsewhere, re-surfacing brake discs to get rid of the shallow ridges caused by normal wear is probably counter productive. The normal light grooving is caused by harder and softer areas in the pad material so it will return within a few hundred Km of use anyway. Grinding the ridges off not only makes the discs thinner (= closer to the wear limit) but it also reduces the effective contact area between the pads and the disc so that until the pads and disc bed to each other again (= form new grooves) the brakes will be less effective.

As for the damage caused by the caliper locking up, whether it would be worth resurfacing would depend on how deep the scar is.
Mr. Honda ('83 GL1100/Dnepr) summer How a motorcycle evolves thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
redglbx
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Re: Resurfacing rotors

#6

Post by redglbx »

Let me just say the proper way to resurface a rotor of any kind is by Blanchard grinding them, Truedisc did them correctly because Blanchard grinding will cause the swirl marks you see in the pictures above. I worked in the Brake industry for many years and my friend ran a dyno which clearly showed an advantage with Blanchard grinding. New disc’sare only Blanchard ground that I’ve ever seen. On cars I usually run a DA sander on the disc’s to remove any glazing but that’s not a good looking finish for an exposed bike disc.
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flyin900
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Re: Resurfacing rotors

#7

Post by flyin900 »

Pb9717 wrote: Thu Nov 18, 2021 9:32 am In discussions with a knowledgeable friend regarding my GL1100, I had asked about resurfacing the rotors as they’re 39 years old. He stated that the rotors don’t have enough material to permit a resurfacing and the resurfaced rotor would be too thin to be considered safe. I ended up purchasing a used rotor in good condition rather than resurfacing the damaged rotor caused by a caliper lock up.

Have any of you resurfaced a rotor and what’s been the outcome?
I don't ride my various bikes more than 3-4K klms each per season, which would be about 2500 miles per bike. So factor than in for what it is worth. I had a set of 3 rotors done on a 1980's CB900C which is a 600+ pound bike by TrueDisk about 8 years ago and rode it for another 5 years. The rotors had no issues with warpage, or anything else untoward during those 5 years. I sold it to someone I knew casually and for another 2 years he rode it with no brake issues I am aware of in his time with that bike.

So unless your a high mileage rider; personally I feel that this is a good option vs the big bucks for anything new rotor wise to fit these bikes.
Last edited by flyin900 on Thu Nov 18, 2021 5:27 pm, edited 1 time in total.
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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flyin900
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Re: Resurfacing rotors

#8

Post by flyin900 »

Sidecar Bob wrote: Thu Nov 18, 2021 12:47 pm As I mentioned elsewhere, re-surfacing brake discs to get rid of the shallow ridges caused by normal wear is probably counter productive. The normal light grooving is caused by harder and softer areas in the pad material so it will return within a few hundred Km of use anyway. Grinding the ridges off not only makes the discs thinner (= closer to the wear limit) but it also reduces the effective contact area between the pads and the disc so that until the pads and disc bed to each other again (= form new grooves) the brakes will be less effective.

As for the damage caused by the caliper locking up, whether it would be worth resurfacing would depend on how deep the scar is.
Bob what you say here does makes sense with the grooves remaining to assist with the braking area. I personally find most of the brakes on all my bikes are well antique vs anything modern. So I try to ride with that in mind; realizing I am stopping the Queen Mary on the heavy stuff. :-D
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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Sidecar Bob
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Re: Resurfacing rotors

#9

Post by Sidecar Bob »

I've been thinking about this and it seems to me that resurfacing would be best reserved for discs that are rust pitted.
Mr. Honda ('83 GL1100/Dnepr) summer How a motorcycle evolves thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
Bloodhound
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Re: Resurfacing rotors

#10

Post by Bloodhound »

I worked as a Automotive machinist years ago and we had a nice Berco brake lathe with the Blanchard segmented wheel on it , great machine . I see that the disc factories do both sides at once , and grind them wet .
76 GL1000 ,73 Norton mk5 , 75 Triumph T160 , 49 Matchless G80 500 rigid ,and
X4 76 HondaTL250s
Pb9717
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Re: Resurfacing rotors

#11

Post by Pb9717 »

Sidecar Bob wrote: Thu Nov 18, 2021 12:47 pm As I mentioned elsewhere, re-surfacing brake discs to get rid of the shallow ridges caused by normal wear is probably counter productive. The normal light grooving is caused by harder and softer areas in the pad material so it will return within a few hundred Km of use anyway. Grinding the ridges off not only makes the discs thinner (= closer to the wear limit) but it also reduces the effective contact area between the pads and the disc so that until the pads and disc bed to each other again (= form new grooves) the brakes will be less effective.

As for the damage caused by the caliper locking up, whether it would be worth resurfacing would depend on how deep the scar is.
There was one particular groove caused by the lock up that gave me pause regarding leaving it on the bike. It was deep enough to expose copper colored metal. and significantly lower than the surface (at least 1-2-mm). The used replacement has the grooves seen in most used but not abused rear disks. So that's what's on the bike now.

Th resurfacing was an option I was being advised against, as I was being told that the disks were produced to be at or near minimum safe thickness, and reducing that would simply not be recommended. I see lots of folks have had success with the resurfaced ones. But for now, I'll stay with the used unit.

I've just ordered (2) new sets of brake lines for the front and back of the two GL's from Raymond at APEX. Killer price of $255 delivered for 8 individual lines, including the custom shorter line for the lower bar. Hoping my rear brake lock up issue is over after this.
(2) 82' GL1100's
99' Triumph Thunderbird Sport 900
2006 Triumph Speed Triple
Cincinnati OH USA
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Sidecar Bob
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Re: Resurfacing rotors

#12

Post by Sidecar Bob »

Grinding past a 1-2mm deep gouge on a dist that was already thinner than new could easily leave the disc pretty close to the minimum thickness...

The disc on the front of my winter machine was actually under the minimum recommended thickness when I replaced it a few years ago (winter is hard on things like that). It still worked OK but I didn't want to take any chances. Even at that thickness the friction surfaces were still the normal colour of the stainless steel. I wonder if the copper colour you saw was something from the pad?
Mr. Honda ('83 GL1100/Dnepr) summer How a motorcycle evolves thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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