TheSamba.com :: View topic

Fri Feb 08, 2013 11:49 pm

I'm working on the brakes for my 71 Bus (is this the worst possible year for VW Brakes?), I've got my new calipers which appear to be correct, but I have some questions about this locating bolt. The 4 bolts that I removed, driver side of vehicle had 2 bolts, one with the shoulder on it that fits the hole in the caliper very nicely. The other side just had 2 regular bolts. That side is also the side that for whatever reason had the caliper seize up while the vehicle was being towed, superheated the bearing grease and caught on fire. I have to reassemble it all this weekend and am wondering if it would be a disaster to use the regular bolt on the lower part of the caliper again while I wait however long it will take to order this special bolt in?

TL,DR: If you don't use the Special Locating Bolt, and sub it with a regular bolt, will it cause issues in the short term?

Sat Feb 09, 2013 7:48 am

on a 73+, each side has only 1 locating bolt. I tHINK it went in the top hole, but I am not 100% sure, although it may only fit in one hole, and again, not 100% sure. so each car had 4 bolts, two shoulder bolts and 2 all threads.

it doesn't break it down in the manual sadly, but you need a M12 x 1.5 bolt with a 10k grade quality, length unkown. it does not mention they are different, so that is annoying.

Sat Feb 09, 2013 7:51 am

http://www.mcmaster.com/#standard-cap-screws/=leji56

10 K and 10.9 are two different things in the manual (grade vs tensile strength) but some online references claim 10.9 superscedes 10K as a rating metric.

Sat Feb 09, 2013 8:25 am

The possiblity exists that some PO lost or broke the correct bolts, and substituted with non-OEM material. That increases the likelihood of poor fit-up, inbalance and binding....and fires while towing? :shock:

I don't recall sharing your bad experience with the '71 bus I had, but that was more than 15 years ago. Maybe brain fade got me. Look for the right part. I can't think of any reason why there would be different bolts on each side.

Sat Feb 09, 2013 8:41 am

"...on a 73+, each side has only 1 locating bolt. I tHINK it went in the top hole, but I am not 100% sure, although it may only fit in one hole, and again, not 100% sure. so each car had 4 bolts, two shoulder bolts and 2 all threads.

*See Bentley, Sec. 8 page 15, Item 7 Disc Brakes:

The exploded drawing shows locating bolt (part 15) applied at bottom. And Fig. 7-2 and 7-3 show 1971 and 1973 caliper sizes. Hardware seems to be the same, except 1971 had a smaller (by volume?) caliper.

If the wheel assembly got so hot while towing that the grease ignited, I think it would be wise to replace your bearings and assume the rotor is heat warped. Once installed with new bearings, perform procedure 7.4 Checking Disc Brake, found on page 8-21.

Sat Feb 09, 2013 9:14 am

early calipers use M12 bolts, late use M14, makes em very easy to tell apart.

Sat Feb 09, 2013 9:28 am

I'll try running the regular bolt for a bit till I can source the proper one, all the holes in the calipers are the same size (all bolts will work), it's just a matter of not wanting the caliper being in the wrong position and messing up again. Thanks for the help guys!

Sat Feb 09, 2013 9:46 am

no problem , just try to find one that isn't threaded all the way, and it will locate a bit better than an all thread.

Sat Feb 09, 2013 10:04 am

Cerot wrote: I'll try running the regular bolt for a bit till I can source the proper one, all the holes in the calipers are the same size (all bolts will work), it's just a matter of not wanting the caliper being in the wrong position and messing up again. Thanks for the help guys!

PM me. I can send you one as a courtesy!

Sat Feb 09, 2013 12:06 pm

Cerot wrote: ... all the holes in the calipers are the same size ...

If that's the case, then the calipers have been modified by a P.O. The stock ATE calipers have one of the mounting bolt holes enlarged, and the
locating bolt will fit in that hole but not the other (and a very precise fit it is!).

Sat Feb 09, 2013 3:49 pm

What's your snag with a '71? Nothing difficult with that year.

The shoulder bolt, as the book says, goes to the bottom. It's for a specific design purpose. When braking the caliper pulls on it versus pushing on it. The shoulder bolt is for locating and clamping and the top bolt only clamps
Unless someone screwed with the calipers, the bolts are not interchangable in there holes. Remember, the shoulder bolt is for locating so it needs to fit with accurate clearance in the hole.
'71 ATE calipers had the top and bottom valves. One for bleed and one for drain. So some people not knowing or not caring are apt to install the calipers upside down. Onve valve calipers prevent that.

Sat Feb 09, 2013 4:30 pm

Sorry my comment on the brakes was meant to be tongue in cheek, I've received some differing information from locals about the calipers, I actually quite like my 71. Wasted youth/adulthood has very kindly offered to send me the proper bolt so I'll be fixing this right, thanks again guys.

Sat Feb 09, 2013 5:21 pm

Desertbusman wrote: The shoulder bolt, as the book says, goes to the bottom. It's for a specific design purpose.

Well, I'm not too sure about that. My brand new ATE Brazil calipers have the shoulder bolt at the top, or at least it's on the
same side of the caliper as the one and only bleed screw. Could there have been some change in the Brazilian bus design
that would cause this? A factory screw-up? The brakes have been working fine for almost a year now.

Sat Feb 09, 2013 5:51 pm

It somehow is a screwup on yours. Bleeder at top and locating shoulder bolt at the bottom. It is a purposeful design.

Sun Feb 10, 2013 10:21 pm

the VW service binder to the rescue! Book B, section 3.2, verse ,err , page 3-12

VW wrote:
NOTE (Type 2)
The thread size of the bolts holding the brake caliper to the steering knuckle has been changed from M 12 x 1.5 to M 14 1.5. the tightening torque for these new bolts is 14.5 to 15.5 mkg (105 to 126 ft lb). The locating bolt on the new brake caliper is at the top of the steering knuckle (previously at the bottom)

Sun Feb 10, 2013 11:17 pm

fusername wrote: the VW service binder to the rescue! Book B, section 3.2, verse ,err , page 3-12

VW wrote:
NOTE (Type 2)
The thread size of the bolts holding the brake caliper to the steering knuckle has been changed from M 12 x 1.5 to M 14 1.5. the tightening torque for these new bolts is 14.5 to 15.5 mkg (105 to 126 ft lb). The locating bolt on the new brake caliper is at the top of the steering knuckle (previously at the bottom)

Wow, that's interesting. Bentley tells the change to the big bolts starts in '73 but it doesn't mention the postion change on the late model big calipers. I think the change to the big stuff in '73 shows that the earlies better well be done right.

Mon Feb 11, 2013 8:57 am

more year differences from the Bible Binder (is there a term folks use for these repair manuals? if not I kinda like bible binder, it is kidna layd out like one.)

VW, Section B3.2 3-10, 11th Suppplement (USA) printed 5. 73 wrote:
Note
A second bleeder screw weas installed on the type 2 caliper from april 1971 and on the types 1 3 and 4 caliper from august 1971. The extra bleeder screw ensures that the system is drained more completely when the fluid is being changed.

Removing and installing the brake calipers
It msust be assured that the caliper is installed with the piston retaining plates in the proper position.

To prevent a brake caliper from being isntalled on the wrong side, make sure that the piston retaining plate (arrow A) on types 1, 2, and 3 is arranged against the lower guide surface of the brake caliper and against hte upper guide surfaces on the type 4. Arrow B shows the direction of disc rotation when the vehicle is moving forward.

//removed cautions on T3 and T4 brakes

Brake Caliper Types 2 and 4
From August 1972

Larger brake calipers with pads 14mm (35/64 in.) thick preciously 10mm (25/64 in.). The caliper pistons have been lengthened from 29 to 33 mm (1.141 to 1.299in.).

Mon Feb 11, 2013 9:20 am

more details, casue I'm such a good Samaritan

Mon Feb 11, 2013 9:21 am

ok not that good a sumaritan, since the arrows are pretty hard to read, but I'm doing all right