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02-20-2012, 05:39 PM
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#1 |
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Junior Member
Join Date: Mar 2007
Location: Hideaway, TX
Posts: 4,950
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Can u tell from vin if a truck has 1" or 1.25" rotor?
see above
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71 Suburban 350/700R4 Project Trixie 72 CHEVY,Highlander,SWB,396,T400 |
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02-20-2012, 06:47 PM
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#2 |
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Garage wrench
Join Date: Feb 2008
Location: LaCrosse, WI
Posts: 1,855
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
no sir
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-Adam 90 V1500 GMC Suburban 350/700R4/NP241..... 01 Saturn SL1 stock DD..... |
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02-20-2012, 07:02 PM
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#3 |
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Registered User
Join Date: Oct 2011
Location: hudson,wi
Posts: 805
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
Pull the wheel off and measure outside to outside of the rotor. You'll know right away.
RIZ |
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02-20-2012, 09:43 PM
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#4 |
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BAD BOW-Silverado XST
Join Date: May 2000
Location: Senior Member from Austin, TX
Posts: 6,431
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
Check the RPO codes. Heavy Halfs, fleet trucks and special orders had them.
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02-21-2012, 12:14 PM
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#5 |
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Registered User
 
Join Date: Apr 2009
Location: New Freedom Pa.
Posts: 1,335
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
My 87 is a "Heavy Half" with 1.25" Rotors.
It has two RPO codes , "JB5" and "J55" JB5 Brake System: Power, Front Disc, Rear Drum, 6400 Lbs. JB5 BRAKE POWER, DISC/DRUM, 6,400 LBS J55 BRAKE SYSTEM HEAVY DUTY Desert |
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02-21-2012, 01:18 PM
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#6 |
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67-72 parts collector,…
Join Date: Nov 2002
Location: Mid-MO
Posts: 22,702
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
The best way is to measure.
I had an '86 with the HD rotors and an '83 with the light duty rotors. I'm not sure what GM was thinking. I know all the 71-72 front ends are 1-1/4". I think all the 73-80 front ends are also 1-1/4". 81-87 is anybody's guess,...
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Keith Convert to disc brakes. http://67-72chevytrucks.com/vboard/s...d.php?t=444823 |
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02-21-2012, 01:35 PM
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#7 | |
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Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,237
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
Quote:
K
__________________
Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ |
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02-21-2012, 02:57 PM
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#8 |
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Junior Member
Join Date: Mar 2007
Location: Hideaway, TX
Posts: 4,950
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
I will pull the wheel and check it out. I was in front of the computer at work and was trying to figure it out.
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71 Suburban 350/700R4 Project Trixie 72 CHEVY,Highlander,SWB,396,T400 |
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02-21-2012, 05:39 PM
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#9 | |
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Registered User
Join Date: Apr 2009
Location: New Freedom Pa.
Posts: 1,335
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
Quote:
JB3 BRAKE POWER, DISC/DRUM, 4,600 LBS Dez |
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02-22-2012, 08:14 AM
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#10 | |
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Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,237
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
Quote:
I know there was a manual system available as well, JB1 perhaps? It just occured to me that, during our recent move, I found the actual component charts that we use/used to release the specific brake hardware for the various systems - from 1979 or so. I'll see if I can find it again and post it up. K
__________________
Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ |
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02-22-2012, 09:55 AM
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#11 |
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6.0 powered square
Join Date: Feb 2008
Location: Mesquite texas
Posts: 3,459
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
my 80 big 10 had 1" rotors that some one swap in, but it now has 1.25 rotors front and rear
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Aaron 1980 c-10 short bed lowered, cammed 6.0, 4l80e 3600 stall, smp tune, wilwoods, and flames best time so far best et 7.86 @87 on motor 7.57 90 on a 75 shot Build http://67-72chevytrucks.com/vboard/s...d.php?t=283326 |
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02-22-2012, 10:23 AM
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#12 |
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C35 Crew Dually
Join Date: Nov 2008
Location: Belleville Ontario
Posts: 1,116
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
off topic but kinda the same but I went to order front pads for my CC dually and they asked me what size my rear breaks were? the sizes were 13.2 1/2 or 13.3 1/2 where do i measure?
sorry for the thread jack
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If it aint square, I don't care. 84 C35 CC Dually Project log... http://67-72chevytrucks.com/vboard/s...d.php?t=414892 |
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02-22-2012, 11:11 AM
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#13 | |
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Registered User
Join Date: Apr 2009
Location: New Freedom Pa.
Posts: 1,335
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
Quote:
Here is one of many resources. http://www.c2e.info/rpocodes/gmrpocodesGthroughM.html JB1 BRAKE, MANUAL DISC/DRUM 4300 LBS Dez |
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02-22-2012, 07:45 PM
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#14 |
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Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,237
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
Ok - as I mentioned, here are the actual charts that were used by the design engineers to release the various brake components. You can see the hardware sizes, bore dimensions, friction material, etc and breakdowns by part number.
Based on the '87 chart it looks like the 1" rotor was used only on the two smallest systems, the JB1 manual and the lightest JB3 power. You should be able to tell by looking for your truck configuration on here: 1974 and 1987 shown:   I'll post the complete set as a reference in a separate thread. K
__________________
Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ Last edited by Keith Seymore; 02-22-2012 at 08:12 PM. |
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02-23-2012, 11:28 PM
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#15 |
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Registered User
Join Date: Jan 2006
Location: Garland, TX
Posts: 970
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Re: Can u tell from vin if a truck has 1" or 1.25" rotor?
easiest way is to stick your index finger in the holes that run along the edge of the rotors. I if you finger goes in its 1.25 if it doesnt its 1"
works for me. lol
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'84 swb chevy '69 swb chevy '68 swb chevy '95 Impala ss-sold '89 chevy crew cab dually 3+3 |
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