Master cylinder upgrade question - 1990 Suburban V1500 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dsy1 · 03-23-2021, 08:58 PM

I have read a lot about the master cylinder upgrade from OBS to NBS to solve the common spongy brake feel. I decided to try this on my 1990 4WD Suburban (V1500) with front disc, rear drum, and rear anti-lock system. This '90 Suburban still has the '73-'87 body style. My original master cylinder looks like this one

The replacement was this one

This replacement did not fit under the hood (too tall). Is there another replacement master cylinder that will work, or a better solution? I have already tried a new original style master cylinder, changed to performance pads and rotors with braided lines in front, and new shoes in the rear, and power bled everything but still have soft brakes and a spongy feel.

I posted this in the 73-91 Suburban section but it seems better here instead.

70GMCer · 03-24-2021, 08:11 AM

The NBS ms I put on my 97 GMC works great & cleared the hood. The one I bought looks just like the one you posted. Got it for the year 2001 from Amazon.

sntrym95 · 03-24-2021, 10:44 AM

The MCs on the Trailblazers are shorter but I don't know if they bolt right up. You'd probably have to get one and see.

dsy1 · 03-24-2021, 02:45 PM

I checked out the Trailblazer MC but the piston is a much smaller diameter.

sntrym95 · 03-24-2021, 05:06 PM

Quote:

Originally Posted by dsy1

I checked out the Trailblazer MC but the piston is a much smaller diameter.

Yeah I noticed that too. The smaller bore might be ok but you'd have to try it out. Given your restrictions, you might have to play around with a few of them to get it right.

Tom · 03-24-2021, 05:41 PM

73-87's did not have spongy brakes. If your master is not the standard 73-87 style, then use one of those.

**kwmech** · 03-24-2021, 07:53 PM

What's the difference in piston diameters? Just upgraded the axles in my 91 and I am in need of a different master. I was thinking about using a 3/4 ton from the same year, but the ports are swapped front to back. Not really an issue for me, but something bolt on would be nice

sntrym95 · 03-24-2021, 08:51 PM

1" on the Trailblazer vs 1 1/8" on the truck. It's fairly insignificant but you would definitely want to test it out. I don't know if the mounting hole centers are the same, I couldn't find any info on that.

03-23-2021, 08:58 PM	#1
dsy1 Registered User Join Date: Aug 2010 Location: San Diego, CA Posts: 127	Master cylinder upgrade question - 1990 Suburban V1500 I have read a lot about the master cylinder upgrade from OBS to NBS to solve the common spongy brake feel. I decided to try this on my 1990 4WD Suburban (V1500) with front disc, rear drum, and rear anti-lock system. This '90 Suburban still has the '73-'87 body style. My original master cylinder looks like this one The replacement was this one This replacement did not fit under the hood (too tall). Is there another replacement master cylinder that will work, or a better solution? I have already tried a new original style master cylinder, changed to performance pads and rotors with braided lines in front, and new shoes in the rear, and power bled everything but still have soft brakes and a spongy feel. I posted this in the 73-91 Suburban section but it seems better here instead.

03-24-2021, 08:11 AM	#2
70GMCer Senior Member Join Date: Apr 2005 Location: Joppa, Maryland Posts: 4,408	Re: Master cylinder upgrade question - 1990 Suburban V1500 The NBS ms I put on my 97 GMC works great & cleared the hood. The one I bought looks just like the one you posted. Got it for the year 2001 from Amazon. __________________ 1997 GMC Sierra Ext 1965 Mustang

03-24-2021, 10:44 AM	#3
sntrym95 Registered User Join Date: Jan 2006 Location: Big Pine Key, FL Posts: 745	Re: Master cylinder upgrade question - 1990 Suburban V1500 The MCs on the Trailblazers are shorter but I don't know if they bolt right up. You'd probably have to get one and see. __________________ Mike

03-24-2021, 02:45 PM	#4
dsy1 Registered User Join Date: Aug 2010 Location: San Diego, CA Posts: 127	Re: Master cylinder upgrade question - 1990 Suburban V1500 I checked out the Trailblazer MC but the piston is a much smaller diameter.

03-24-2021, 05:41 PM	#6
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,692	Re: Master cylinder upgrade question - 1990 Suburban V1500 73-87's did not have spongy brakes. If your master is not the standard 73-87 style, then use one of those. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

03-24-2021, 07:53 PM	#7
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: Master cylinder upgrade question - 1990 Suburban V1500 What's the difference in piston diameters? Just upgraded the axles in my 91 and I am in need of a different master. I was thinking about using a 3/4 ton from the same year, but the ports are swapped front to back. Not really an issue for me, but something bolt on would be nice

03-24-2021, 08:51 PM	#8
sntrym95 Registered User Join Date: Jan 2006 Location: Big Pine Key, FL Posts: 745	Re: Master cylinder upgrade question - 1990 Suburban V1500 1" on the Trailblazer vs 1 1/8" on the truck. It's fairly insignificant but you would definitely want to test it out. I don't know if the mounting hole centers are the same, I couldn't find any info on that. __________________ Mike



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