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Old 01-04-2019, 04:50 PM   #1
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66mm calipers and 73mm calipers Mounting differences?

This is not my first post, have been on here as:Jim Aerbus, W22, for over 10 years, will not let me renew under that name???.
Question, is there any thing different that has to be done on a 2003 W22 chassis to mount 73mm calipers. Does a 2003 chassis already have 73mm Calipers? Getting ready to do brake job.
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Old 01-04-2019, 05:14 PM   #2
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As far as I know. no 73 mm calipers were installed from the factory on the WH chassis.

Link to 73 mm install.
http://www.oemys-performance.com/tec...tm#66mmto73mm]
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Old 01-04-2019, 05:29 PM   #3
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Yeah, thanks for that info, but that is why the question. Read all the saved stuff and came away in a daze My RV chassis was actually made in May 0f 2002, and is on a242" wheel base from Rexhall corp. with a 24,500 GCW. and I have owned it since new. Brake recall done when first came out. Have 73500 on it now, so thinking about new brakes with upgrade if necessary. Guessing 66mm calipers, but GVW is throwing me a curve. Vehicle has beefed suspension why Firestone 16' air bags on rear. So kind of a head bumper.
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Old 01-04-2019, 05:58 PM   #4
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Look at the back side of your caliper. All 73mm calipers have the "73" cast into the rear half of caliper.
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Old 01-04-2019, 06:56 PM   #5
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The information I have from the NAPA website shows:
66 MM piston caliper casting # 4153269
73 MM piston caliper casting # 4153222
This will be in raised numbers on the back (piston) side of the calipers.
To be sure the calipers will fit the knuckles you may want to go to a parts store and look at the two different calipers side by side and compare physical size
The pads will be different as well.
The caliper # for the 66 MM will be SE 8607
The caliper # for the 73 MM will be SE 8609
These are NAPA numbers. All 4 calipers are the same part number. The bleeder screw will fit in the top hole when installed and the brake hose will attach to the bottom hole. Both holes have a seat in them to make the bleeder location interchangeable.
Lynn
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Old 01-04-2019, 07:28 PM   #6
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If you had a brake recall done then it has 66mm calipers on it. That letter was sent only to 66mm caliper owners.



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Old 01-05-2019, 08:57 AM   #7
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Quote:
Originally Posted by Oemtech View Post
As far as I know. no 73 mm calipers were installed from the factory on the WH chassis.

Link to 73 mm install.
]Oemy's Web Site - Tech Tips
Dale, I certainly don't want to start an argument with you but the NAPA Pro-Link website (NAPA Auto Care Center operators only) clearly shows both size calipers for the W 22 chassis. This is not a Bible though. It could be incorrect.
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Old 01-05-2019, 09:36 AM   #8
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Quote:
Originally Posted by LETMGROW View Post
Dale, I certainly don't want to start an argument with you but the NAPA Pro-Link website (NAPA Auto Care Center operators only) clearly shows both size calipers for the W 22 chassis. This is not a Bible though. It could be incorrect.
Lynn
It may show it but I don't think I have ever seen 73 mm calipers come directly FROM WH.

The key to this install is the Tie Bars!

FYI - Glenn once told me about his buddies at the IHC shop, in Dallas/Ft Worth, that they replaced so many 66 mm on school buses and MD trucks that they had to use a front loader to scoop them up to load them in the recycle truck.

FYI2 - I was also told, can't prove it, that Bosch replaced as many as 250,000 66 mm calipers just on WH chassis. Makes sense as to why WH dragged their feet for 6 years.
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Old 01-05-2019, 09:43 AM   #9
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Quote:
Originally Posted by LETMGROW View Post
The information I have from the NAPA website shows:
66 MM piston caliper casting # 4153269
73 MM piston caliper casting # 4153222
This will be in raised numbers on the back (piston) side of the calipers.
To be sure the calipers will fit the knuckles you may want to go to a parts store and look at the two different calipers side by side and compare physical size
The pads will be different as well.
The caliper # for the 66 MM will be SE 8607
The caliper # for the 73 MM will be SE 8609
These are NAPA numbers. All 4 calipers are the same part number. The bleeder screw will fit in the top hole when installed and the brake hose will attach to the bottom hole. Both holes have a seat in them to make the bleeder location interchangeable.
Lynn
Before


After


Size Counts




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Old 01-05-2019, 09:59 AM   #10
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Quote:
Originally Posted by Oemtech View Post
Before


After


Size Counts




Excellent post Dale. I have a 2007 W24 chassis. Will it have the 73mm calipers? It looks like it does, but I am not certain.
Thanks again for the information.
Norman G.
Happy Glamping.
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Old 01-05-2019, 10:22 AM   #11
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Quote:
Originally Posted by Unplanned View Post
Excellent post Dale. I have a 2007 W24 chassis. Will it have the 73mm calipers? It looks like it does, but I am not certain.

Thanks again for the information.

Norman G.

Happy Glamping.
The W24 has 70 mm IIRC.


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Old 01-05-2019, 10:33 AM   #12
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I'm sure this has been discussed over and over but I wasn't on here when all the recall info was flying around. What was the issue that prompted the recall to start with?
Lynn
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Old 01-05-2019, 10:57 AM   #13
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Thank you for the great feed back on my questions about the calipers, they have been answered. I am sure that I must have the 66mm calipers so I will go from there. Jim C.
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Old 01-05-2019, 12:01 PM   #14
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Quote:
Originally Posted by LETMGROW View Post
I'm sure this has been discussed over and over but I wasn't on here when all the recall info was flying around. What was the issue that prompted the recall to start with?
Lynn
The original issue was one that I ID'd as the same issue I had with a Dodge Van back in the '60s.

Basically, the Phenolic coated steel caliper piston would absorb moisture, swell up, stick in the out position, burn up the caliper, melt the ABS Sensor and cause the rotors to crack/fracture.

WH delayed, delayed, delayed with every excuse from "You don't know how to drive.", install a grease zerk on the brake bell crank, install a return spring etc. It wasn't until NHTSA got involved that WH/Bosch did a "voluntary recall". Then you only got the calipers replaced and some brake fluid to replaced what was lost when you really needed to have the system flushed along with the ABS system. Rotors and pads were extra and many dealers were ripping customers for thousands of dollars in parts and labor.

I did some research and found out, at the time, there were only two manufacturers of Phenolic coated caliper pistons. Also, I found out there were 2 different coatings... light duty and heavy duty so to speak. The bottom line is WH use the light duty coating and fitted the caliper pistons to tight, IMHO.

The real solution is to install Stainless Steel pistons. But, the cost would have been outrageous. I had a customer that owned a machine shop, he made his own set of replacements out of SS. His testing should no issues after repeated panic stops.

So, why did this happen? It is how an RV is used. It is parked for extended periods of time, then driven for hours/days, has no brake maintenance done for possibly years, the system absorbs moisture, the brake fluid gets cooked from hard braking and so or later the caliper pistons freeze.

Part of the solution is to do a fluid replacement every 2 years. This where Speed Bleeders comes into play. Dealers were charging $$ to do this. It takes 3 qts of DOT 3 fluid and maybe 30 mins to flush/bleed the system. With Speed Bleeders you can DIY it for probably less than $20 for fluid and a one time cost of $30 for the Speed Bleeders.

OBTW - It took about 3 months to get the Speed Bleeders engineered and tested. Why.? The 66 mm caliper bleeder screw is an odd size, 7/16x24. They can be purchased from Speed Bleeder.
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