95 suburban c2500 7.4 13x3.5 new drum center .010-.012 larger than hub causes run out.

[superchevysb]

1995 Chevy suburban c2500 7.4 14 bolt 10.5ff

I have recently decided to replace the rear brake shoes and drums to further improve the rear braking. I went with the AC Delco Durestop brake shoes and AC Delco spring kit. The spring kit was disappointing as the springs were made with steel that made them way to hard to extend and the hook end were very shallow large radius to the point that with all the excess tension they would almost pull them selfs off, slip off. I cleaned the original spring and used them they worked great.
The brake shoes seemed to be made well and are FF confident of friction rated, hopefully that is enough to improve braking. I could not find a higher rate shoe.
The drums were purchased from Napa and the machining was great with one problem, the center hole was .010 and .012 larger than the hub. I initially thought they were machined wrong and center was not centered. Soon to discover the over size center was cause the extreme drag in one are of rotation. I put the tight spot to the bottom loosened and red tighten wheel to find the tight spot now opposite. Then I measure with feeler gauge to find the center was larger. I but 4 paices of .005 shim stock for one side and .006 for the other and evenly spaced them and held them on with rubber bands and electric tape. Slid drum on and it was snug and correct. I spun the wheel and watched through Inspection hole to see a nice even gap/no run out as it rotated. Adjusted brakes and push pedal several times when adjusting to keep center the shoes to get the best adjustment possible. Rotating the wheel it now has even drag the entire rotation. With run out it will cause the wheel cylinders to collapse as that tight spot comes around and make more pedal travel as wheel as cause a shake when braking. Seems to have worked out well.

 

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[Supercharged111]

Such is the struggle to get decent parts nowadays. Brake drums seem particularly afflicted. Are they out of round/balance too?

 

[Sean Buick 76]

I would either weld material into the drum or return the drum for another one.

 

[Schurkey]

Apparently, it's BOTH drums, and "good luck" finding something better when formerly-respectable companies race to the bottom by sourcing from the Communists. I'm not saying you shouldn't complain--clearly not enough of us are, or they wouldn't continue to sell half-assed parts.

Nobody should have to shim the brake drum to make it stop smoothly. Good for you for figuring out what's needed to make them work.

Assuming that NAPA sold you the correct drums for the application (not drums to fit a similar axle under a RAM, for example, or some Ford) it might be nice if you'd send those photos and description to the company responsible for importing, and the company responsible for selling those drums. (May be NAPA in both cases.)

 

[superchevysb]

Apparently, it's BOTH drums, and "good luck" finding something better when formerly-respectable companies race to the bottom by sourcing from the Communists. I'm not saying you shouldn't complain--clearly not enough of us are, or they wouldn't continue to sell half-assed parts.

Nobody should have to shim the brake drum to make it stop smoothly. Good for you for figuring out what's needed to make them work.

Assuming that NAPA sold you the correct drums for the application (not drums to fit a similar axle under a RAM, for example, or some Ford) it might be nice if you'd send those photos and description to the company responsible for importing, and the company responsible for selling those drums. (May be NAPA in both cases.)

You raise all valid points for sure. Speaking on the lack of quality control now days I bought 3 different brake line flaring kits and none of them would make even a decent double flare. I have been doing it for years and always used the kits around the shop that were probably 20-30 years old And were machined nice and worker flawlessly Everytime. Anyhow this was being done at home and I had to return all three kits because they were garbage machining was horrible. I ended up using a friends master cool hydraulic style flare tool to make nice flare. Sorry that was off topic but these junk parts and tools now days is frustrating. So yes the driver side drum was .010 over size center and the passenger side was .012 over size center. The hubs are stock and still have the factory machine markings so they were not pounded out of size or shape or anything like that. Once I shimmed them they ran perfectly true. So true that with just a slight adjustment drag they got hot. Normally you have some run out even minimum and you set the peak drag/adjustment to the tight spot and it works. I had to back the adjustment off some and all is well and still have great pedal. The shoes grab far better than the set that came off I'm sure that added to some of the heat in the drum also.

 

[superchevysb]

I would either weld material into the drum or return the drum for another one.

Yea I considered welding spots and filing each spot and trying to measure to keep them exact but shimming was the easiest method at that moment. I also considered center punching/knurling the inside but it probably would have been to tight to get on than.

 

[superchevysb]

Such is the struggle to get decent parts nowadays. Brake drums seem particularly afflicted. Are they out of round/balance too?

Once I shimmed them equally they were rite on with no noticable run out when rotating and viewing the slight gap between drum and brake shoe through inspection hole. Also the adjustment drag was consistent the entire way around now. Another problem with drums is the storage of them, if they are not stored or shipped properly they can deform. Seems hard to believe but apparently it happens. We used to have to do a fine cut on some pairs of new drums to get them true.