RPO 684/687 Differences :The Details

[Justin B.]

I know that the RPO 687 had the large "cups" on the bottom of the small brake shoe hold down springs but were they on the RPO 684 cars? I havn't heard of them being present on the early big brakers but what are your opinions? Thanks guys!!

[James G.]

Re: RPO 684/687 Differences :The Details

I know that the RPO 687 had the large "cups" on the bottom of the small brake shoe hold down springs but were they on the RPO 684 cars? I havn't heard of them being present on the early big brakers but what are your opinions? Thanks guys!!

Not exactly sure what you want here Justin, but I received the following from Fran Estereicher, Corvette collector that loves RPO brake/ suspension stuff and has access to GM Engineering from the 50's and 60's.



I attached the spring picture. does that help?

[Justin B.]

Re: RPO 684/687 Differences :The Details

Aren't the springs RPO 686, not 684 or 687?

[Bill M.]

Re: RPO 684/687 Differences :The Details

The 684 and 687 pull-back springs are dark green.

[Joseph T.]

Re: RPO 684/687 Differences :The Details

The 684 and 687 pull-back springs are dark green.

Here they NOS.

Same size and dimension as standard pull back springs but these are high heat treated...and painted dark green.

Joe

[James G.]

Re: RPO 684/687 Differences :The Details

Here they NOS.

Same size and dimension as standard pull back springs but these are high heat treated...and painted dark green.

Joe

So Joe, What are the springs Franz sent me above ?

[Justin B.]

Re: RPO 684/687 Differences :The Details

That is an RPO 686 set-up, not RPO 684 or 687

[Joseph T.]

Re: RPO 684/687 Differences :The Details

So Joe, What are the springs Franz sent me above ?

Jim

I don't know by the picture..I would have to check the part # in an old parts book. Just a guess but it appears to be a genuine spring kit. Not sure of the application.

Joe

[James G.]

Re: RPO 684/687 Differences :The Details

The 684 and 687 pull-back springs are dark green.

Thanks Guys,
I learned something here. Back in the day no one looked, we just changed the parts. Doug Hooper and I were talking last week about this. After each day of racing it was not uncommon to completely do a 'new brake job' at the race track.

NEW shoes, NEW Springs, and NEW drums. We even rebuilt wheel cylinders. A major RPO set up came in a wooden box for $202.00. And as I remember, there were springs and a quick steer adapter in there also.

[Franz E.]

Re: RPO 684/687 Differences : SPRINGS



SPRINGS very boring subject, unless you were a spring designer in a previous life.

[John N.]

Re: RPO 684/687 Differences :The Details

Franz, good to see you in Florida. Would you give a lesson on measuring brake spring tension. I do have fish scales. Also why was the small spring used for the race RPOs and the large springs used for the street metallic RPO.
Regards

[Joseph T.]

Re: RPO 684/687 Differences : SPRINGS

SPRINGS very boring subject, unless you were a spring designer in a previous life.

Franz

I wonder what kind of brake springs were used on my 59 Buick LeSabre which has its original finned drums.

Joe

[Franz E.]

Re: RPO 684/687 Differences :The Details

Hi John:

[Franz E.]

Re: RPO 684/687 Differences :The Details

Hi Joe:

[Joseph T.]

Re: RPO 684/687 Differences :The Details

Hi Joe:

Franz..If memory serves me correct the fronts are cast iron and the rears are aluminum..or vice versa.

Next time I get a chance I will look. The car has less than 50,000 miles but I did have a brake job...so who knows if they replaced the springs.

Hope you are well..

Joe