Rear Disc Brake Conversion Kit - 1977 Transam

[1977 Transam]

Forgot to ask, "What size drums would be on mine at the moment"? 

Not sure if anyone knows.

Thanks.

Tommy

[1977 Transam]

Found this article comparing drum vs disc brakes which I found interesting.

http://www.edmunds.com/car-technology/brakes-drum-vs-disc.html

Tommy

[bonnevista]

Forgot to ask, "What size drums would be on mine at the moment"? 

Not sure if anyone knows.

Thanks.

Tommy

I think they're 9 inch from memory.

[LeighP]

Yep, B body drums are 11" vs the stock 9" diameter.

Most of the braking on a 2nd gen is accomplished by the discs on the front. The large drums are effective and unless you're using them for track work, I can't see heat build up being an issue.
Whatever you do, be prepared for the possibility of needing an adjustable bias valve.
Be sure to double check the seated depth of the booster's operating rod vs the piston in your mastercylinder.....problems with this surfaced on my car and others when combining repro mastercylinders and repro boosters.
You won't need to change the factory booster/master combo if you're only switching to 11" drums. You will need to replace the mastercylinder if you're switching to disc/disc, and in some situations, you may need to change the booster as well (factory disc/disc WS6 booster isn't the same as the earlier disc/drum booster from memory).

[bonnevista]

And in my series of car (maybe others), full size station wagons had 12 inch drums on the rear.

[sms777]

12" drums!!.....holy crap.....no wonder you call your car a barge....

[bonnevista]

Also, (and I'm dredging the depths of my memory here) the midsize Oldsmobile (Cutlass/F85) used a wider drum on the rear of their station wagon.  They still used a 9 inch drum, but it was the drum they used to use on the front with a wider shoe.  The backing plate was the weird part, as it had a funny offset to accommodate the wide shoe.

[1977 Transam]

Hi guys.

I was asked a question today from a parts supplier in the states.

He wants to know what the axle flange offset measurement would be on my Transam.

Would anyone know what it is please or where I can find this answer.

Mister google hasn't offered me an answer as yet.

Thanks.

Tommy

[LeighP]

Nothing here to measure, so I can't help.....but thats an odd question to ask. There are only two different 2nd gen 10 Bolt axles.....Drum brake, and Disc brake. The axle register (the raised seat for the drum centre) is a little bigger (wider) I seem to recall on the disc brake axle.
That could be what he's asking?

[1977 Transam]

I know Leigh.  It's very odd.

I've been searching everywhere for the answer.  Two suppliers gave me the option of 2.75" or 2.81".

I found this on the net...........

http://www.crankshaftcoalition.com/wiki/images/thumb/a/a7/Rear_end_axle_flange_id.jpg/800px-Rear_end_axle_flange_id.jpg

No info on the offset though.

Didn't think upgrading brakes would be so difficult.

One thing is for sure, companies sell their brake upgrade kits noting it's for a specific model, but when you want to buy it they ask you to double check the measurements.

Why promote a part for a vehicle if they don't know if it's going to fit.  And to top it off they know nothing about the vehicle they are selling parts for.

You would think they have a listing of the offsets if they are going to ask the question.

The first company that can confidently provide me with info on a brake upgrade install on my car will get the sale.

I'm fed up with it now.