need help

[Joseph44]

I want to put new brks on my 1983 buick prk ave but I'm not sure what size rotors. Not sure but I think 2 diff. sizes were used the vin # is 1G4W69y5DH425229. Any help would be greatly appreciated. Dealer here not much help.

[tom_in_nh]

What I usually do in a case like that, is to buy all of them.

Once job is done, the incorrect parts are returned for refund.

No chance of screwup that way....

Good luck,

Tom

[Guest Jim_Edwards]

Or you could just pull a wheel and with a cloth tape measure, measure the outside circumference of the rotor on the car and do a little math to determine the diameter. But to make it easy, if the circumference is 34.5 more or less the rotor is considered an 11". If the circumference is 37.6 more or less the rotor would be a 12".

[Joseph44]

Thanks Jim I appreciate the help and by the way tom_in_nh 99% of the people on this site are looking for help on a project, But I'll give you a LOL this time. Thanks again Jim!!!!!!!!!

[tom_in_nh]

Glad to to try to help, Joseph.

When I give advice, it is from the viewpoint of a mechanic. This mechanic has seen many kinds of oddities....especially when car owners bring along their pile of new replacement parts.

I have seen the incorrect part inside of the correct box.

I have had the issues arise where the parts man's computer software had incorrect part numbers for a given application.

The list for potential errors can go on and on....

For me, it is not fun to not be able to finish a project on time because of incorrect parts, especially when the owner is waiting.

Much easier for me to deal with the returns later....

Tom

Edited January 17, 2012 by tom_in_nh
Spelling error (see edit history)

[Joseph44]

Thanks tom-n-nh I appoligize for the sarcasum and I do appreciate your help. Have a great wk!!!!

[NTX5467]

The reason the local dealer might not be much help is that 1983 is way BEFORE GM started using the VIN-defined parts lookup. You had to look at the option codes on the Service Parts ID label on (either) the underside of the deck lid or on top of the spare tire cover, under the trunk mat. As a result, the GM parts database has the brake system option codes listed, which can be matched on the SPID label.

I highly suspect they are the 11" rotors, which is the common size for the B/C platform cars with gas motors.

The OTHER thing is that if you told him "Park Avenue", the GM Parts database calls these cars "Electra, with Park Avenue Trim" (with the appropriate option code for the trim). Therefore, they might not have been able to find "Park Avenue" in the parts listings, only "Electra" . . . BUT if they went to the "VIN Decode" chart, this situation would have been "right there". Even though the only model ornamentation on the car might be "Park Avenue", they are still, for GM VIN purposes, "Electras". This situation carried over to the later fwd Park Avenues, too.

Regards,

NTX5467

[Joseph44]

Thanks NTX5467 I really appreciate the time you took to reply this info helped greatly. Thanks again have a great wk/nd!!!!!

[Guest Jim_Edwards]

What I find interesting is the fact there seemed to be an indiscriminate use of 11" and 12" rotors that apparently had nothing to do with anything unless some cars had the Tewes type booster and others not perhaps determining the rotor diameter.

[NTX5467]

What I find interesting is the fact there seemed to be an indiscriminate use of 11" and 12" rotors that apparently had nothing to do with anything unless some cars had the Tewes type booster and others not perhaps determining the rotor diameter.

This is why the brake system production/option code is important, which is on the SPID label in the trunk. The option code can also affect the other items on the front brakes (calipers, even with the same rotor size).

In some cases, the diameter and minimum rotor thickness is cast into a recess near the center of the hub section of the rotor, on the outer side.

Take care,

NTX5467

[Joseph44]

Thanks guys for all the input I appreciate the help!!!

[joe_padavano]

What I find interesting is the fact there seemed to be an indiscriminate use of 11" and 12" rotors that apparently had nothing to do with anything unless some cars had the Tewes type booster and others not perhaps determining the rotor diameter.

Sorry, but on the 1977-1990 RWD GM B-, C, and D-body cars, there is a VERY discriminate use of the different size brakes. The regular B-body cars (Chevy Impala/Caprice, Olds Delta 88, Buick LeSabre, and Pontiac Bonneville) got the smaller 11" front rotors and 9.5" rear drums with the 5 x 4.75" bolt circle. The C-body (Olds 98 and Buick Electra) and D-body (Caddy Fleetwood) cars all got the 12" front rotors and 11" rear drums with a 5 x 5" bolt circle. The exception on the B-body cars is that cars with the HD brake and suspension package got the larger brakes and the larger bolt circle. This included the taxi/police packages, all wagons, and the 1977-79 cars with the 403 Olds motor.

A 1983 Electra Park Avenue will have 12" front rotors and 11" rear drums.

[Larry Schramm]

One of the major reasons for the different sizes of rotors, etc was what engine was in the car and did the car have heavy duty suspension for towing trailers, etc. If the car came equipped with a smaller engine like a V-6 it might have the smaller rotors. If it had a big engine then it would have the larger braking system.

I know the early front wheel drive Buick Centuries if I remember had 14 inch wheels for the 4 cylinder models and 15 inch wheels/tires and the brake sizes were different also.

[NTX5467]

With all due respect, if you check the ACDelco parts lookup for "1983 Buick Electra" brake frictions and rotors, it lists "18A30 12" front rotor with hub" and "18A57 11 1/64" front rotor with hub" . . . BOTH for "Estate Wagon" 1981-1984.

When I changed the vehicle spec to "1983 Buick LeSabre 5.7L diesel V-8", the same rotor listings came up, except that the 18A30 was listed as "11 7/8" diameter" rotor.

When I changed the vehicle spec to "1983 Cadillac Fleetwood Brougham 5.7L diesel V-8", the 18A30 rotor (11 7/8" or 12") was listed, with "18A2" being listed as "Limo". The 18A2 applications include the GM B/C cars between 1971-1976 and 1/2 ton 2WD light trucks into the middle 1980s.

With respect to the rear, in ACDelco, both 9.5" rear drums (originally aluminum drums, which must be replaced in pairs with cast iron drums) and 11" rear drums (of two different widths) with one set of rear brake linings. The listing of the 9.5" rear drums included "Estate Wagon".

Now . . . I fully realize that modern parts listings might not list all of the original "application specific" items, but now have "combined listings" in many cases, where one part fits many applications rather than one part fitting one or two vehicle applications only. Be that as it may . . . I highly suspect that which brake rotors/pads/rear drums/rear brake linings were under the GM B & C platform cars in any given year is more "production/option code dependent" rather than being "model dependent". In some cases, over the years, IF the brake system's capacity was upgraded due to increasing vehicle weight, then no further upgrades would be needed for trailer towing/HD/Police use vehicles.

The other thing is model interchangeability of the front spindles, which relates to the larger rotors needing different caliper mounting locations. AND related production costs.

I do know that some B-car station wagons came with 12" rotors as I found an article about upgrading F-body front brakes to 12" rotors, provided the F-body ball joints were the same as the B-car's ball joints (which were model year specific). Same caliper, just mounted farther out due to the larger rotors. It was better to upgrade to 9C1COPO Nova police car front pads (also used on 1981 Cadillac Limos!) than to do the spindle swap (which I missed the ball joint interchangeability by 1 model year on).

In the earlier VIN, as I recall, there is a VIN space designated to brake system capacity. Decoding THAT digit/letter designation will easily tell which brakes (rotor and drum sizes, front/rear) are under the car, but NOT the wheel bolt pattern. The brake option production code would further define the brake system as to front brake pads and rear lining specs and also which power brake booster was spec'd for the car (in the parts listings).

Respectfully,

NTX5467

[Joseph44]

Thanks guys for all the help I picked up 2 rotors duralast both 11'' now this veh. has air shock system from factory. It set up to pull t.trail,eng. 305ci v8. I'll be doing front brakes this wk I will measure one that are mounted and I will let everyone know. I really appreciate all the help guys. Everyone have a great wk I know it took time to research!!!!

[joe_padavano]

With all due respect, if you check the ACDelco parts lookup for "1983 Buick Electra" brake frictions and rotors, it lists "18A30 12" front rotor with hub" and "18A57 11 1/64" front rotor with hub" . . . BOTH for "Estate Wagon" 1981-1984.

And with all due respect, I suppose you've NEVER found an error in an on-line parts listing or aftermarket catalog (yes, the AC Delco catalog is aftermarket, not a factory parts book). Show me a factory parts book that says that.

One more time:

EVERY SINGLE 1977-1990 (and actually, 1991-96 as well) B-body wagon got the 12" rotors and 5 x 5" bolt pattern.

EVERY SINGLE Olds 98/Buick Electra built from 1977-1984 got the big brakes.

EVERY SINGLE Caddy Fleetwood built from 1977-1990 got the big brakes.

[NTX5467]

Yes, I have found some errors in online catalogs over the years I've dealt with GM parts . . . at the dealership level. BUT, just as there have been some errors in the GM carline division parts books over the years, such errors (at least on the GM side of things, via contact with PARTECH or prior operatives in the GM Service Parts Operations organization) usually get fixed as soon as they are pointed out. At this point in time, I suspect any errors of the magnitude you've noted would have been addressed long ago, considering the age of the vehicles involved.

I am also fully aware that ACDelco is not only GM's internal supplier but also an aftermarket parts supplier. I might also add that in later years, almost every ACDelco part now has OEM GM part numbers on it, in addition to the prior ACDelco numbers. PLUS, the numbers noted in this particular situation (the ACDelco numbers) are also standardized "industry part numbers" that transcend any OEM part numbers . . . whether they are from ACDelco, Raybestos, or whomever. This simplifies things when an auto supply might change vendors, yet the part numbers in the catalogs are the same.

I also know that as vehicles age from their original model year, the later versions of catalogs for these vehicles similar age as GM part numbers are projected to be deleted by the time the newer version of the catalog is printed and distributed. I've also found that, in several cases, the older (and removed from the later catalogs) part numbers can still be available from GM warehouses . . . IF anybody cares to find an earlier catalog and the prior part number and research the GMSPO online databases. And we all know that, even in later GM catalogs, a multitude of earlier part numbers can be condensed into a much smaller list of part numbers after the particular vehicle's model year is past . . . case in point, fan clutches for the '88+ C/K chassis pickups originally had MANY fan clutch listings, but in about two model years, the listing was very condensed with the "SnowPlow" option fan clutch becoming the normal V-8 with a/c fan clutch. It could well be that as these consolidations took place, what you recall to be correct (at the time) migth have transitioned into what I've found online. I do have some copies of Chevy parts books from back then, but they aren't where my computer is. I'll see if there are some of the BOPC books at work, for good measure.

Respectfully,

NTX5467

[Joseph44]

Holly Toledo guys the more I read the more cornfused I get. I really appreciate all the research you all have done I'm sure it will help others with the same situation. All of you help greatly I'm sure. Have a great and safe wk!!!!

[Joseph44]

Well I put my rotors and new pads on just a word to let all of you know the rotors I bought at the parts store were 11" in diam. But the ones I took off were 113/4" so it took the later Buickroadmaster and Elec. prk ave use the same rotor. Thanks again for all the help all your responces were greatly appreciated Have a great wk/nd!!!

[joe_padavano]

...so it took the later Buickroadmaster and Elec. prk ave use the same rotor. Thanks again for all the help all your responces were greatly appreciated Have a great wk/nd!!!

Yup, as noted above. ALL the 1977-1984 Electras and 1977-1990 B-body wagons got the big brakes and 5 x 5" bolt circle.

[Guest Crusty]

Yeah, I see 9.5", 11"x3.25", and 11"x4" options online for about $30 each...the width variables don't make it any easier.

Edited February 3, 2012 by Crusty (see edit history)

[joe_padavano]

Yeah, I see 9.5", 11"x3.25", and 11"x4" options online for about $30 each...the width variables don't make it any easier.

Drum brake sizes usually refer to the width of the shoes, not the drums. The on-line catalogs for some reason list the overall height of the drum, which is somewhat useless. The B-body rear drum sizes are 9.5 x 2 and 11 x 2. Apparently some of the heavier C-body and D-body versions used 11 x 2.5 rear brakes as well. On my wagon, there are two different rear drums listed, and both fit the 11 x 2 shoes. The taller versions simply overlap the backing plate more, for some reason. They are functionally interchangeable, however, as I've used both.