16.5 wheel hitting rear brake drums - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bluek5 · 03-01-2015, 08:45 PM

So I had a bright idea to put some 16.5 x 8.25 wheels on one of my Blazers. While I was tightening the rear wheels they did not seem to be tightening down soon enough. I thought maybe they were tight on the center of the axle. Anyway I went for a ride and could hear grinding noises coming from the rear end. I crawled under to investigate and it appears that the outer edge of the drum is in contact with the wheel. This is deforming the drum pushing it into the backing plate. I am just interested if anyone has experienced this before.
Thanks, Paul

65standard · 03-01-2015, 09:08 PM

I'm guessing that your new rims have too much back spacing.

**special-K** · 03-02-2015, 08:00 AM

never heard of such a thing. I have run 15" wheels on a K/20 with HO52 as well as on Dana 60s and they cleared those larger brakes. They even cleared the front calipers once I took the casting ridge out of the center radius

**Stocker** · 03-02-2015, 11:57 AM

It does seem odd -- I also ran 15s for a few years on my K20 with HO52 and big finned drums, with no interference at all.

bluek5 · 03-02-2015, 04:18 PM

Quote:

Originally Posted by 65standard

I'm guessing that your new rims have too much back spacing.

These wheels have about 4 1/2" of back space. The wheel is hitting the edge of the brake drum. It seems to be more of a problem of the shape of the wheel. Hopefully you be able to see where the wheel was contacting the drum in the attached picture.

bluek5 · 03-02-2015, 04:32 PM

Quote:

Originally Posted by special-K

never heard of such a thing. I have run 15" wheels on a K/20 with HO52 as well as on Dana 60s and they cleared those larger brakes. They even cleared the front calipers once I took the casting ridge out of the center radius

I ended up radiusing the edge of the drum about 1/4"-3/8". Just curious as to why the drums where hitting the wheels. As far as I know the 16.5 wheels were optional for this year of Blazer. The drums could be from a 73 or newer truck that still shouldn't really be an issue though.
Thanks for the replies, Paul

**special-K** · 03-02-2015, 09:40 PM

I know Blazers had the bigger finned drums and there were smaller ones on C/10s. Maybe the drum profile changed when disc brakes came out

03-01-2015, 08:45 PM	#1
bluek5 Registered User Join Date: Apr 2012 Location: Lehi,Utah Posts: 1,330	16.5 wheel hitting rear brake drums So I had a bright idea to put some 16.5 x 8.25 wheels on one of my Blazers. While I was tightening the rear wheels they did not seem to be tightening down soon enough. I thought maybe they were tight on the center of the axle. Anyway I went for a ride and could hear grinding noises coming from the rear end. I crawled under to investigate and it appears that the outer edge of the drum is in contact with the wheel. This is deforming the drum pushing it into the backing plate. I am just interested if anyone has experienced this before. Thanks, Paul Attached Images

03-01-2015, 09:08 PM	#2
65standard Registered User Join Date: Dec 2014 Location: Coal City, IL Posts: 695	Re: 16.5 wheel hitting rear brake drums I'm guessing that your new rims have too much back spacing. __________________ Tony Nicholas @ Midwest Metal Masters 1953 Chevy 3100 392 Hemi w/727 & 9” Ford 1985 Chevy C/10 6.0L 4L80 373 locker

03-02-2015, 08:00 AM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,862	Re: 16.5 wheel hitting rear brake drums never heard of such a thing. I have run 15" wheels on a K/20 with HO52 as well as on Dana 60s and they cleared those larger brakes. They even cleared the front calipers once I took the casting ridge out of the center radius __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

03-02-2015, 11:57 AM	#4
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,582	Re: 16.5 wheel hitting rear brake drums It does seem odd -- I also ran 15s for a few years on my K20 with HO52 and big finned drums, with no interference at all. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

03-02-2015, 09:40 PM	#7
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,862	Re: 16.5 wheel hitting rear brake drums I know Blazers had the bigger finned drums and there were smaller ones on C/10s. Maybe the drum profile changed when disc brakes came out __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~



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