Big bolt vs Small bolt

[R0K3_B3aRd]

Im getting a 8 3/4 rear end for my 65 cuda and i have no clue what people are meaning by big bolt or small bolt. Does it already come with it? how could i make it into one or the other?? Do i need other parts to make it happen? how do you know if a rim is big bolt or small bolt?? pleas help I'm completely lost on this topic thanks.

 

[70DartMike]

Big bolt is a 5 stud pattern, 4.5" across 2 studs. Same for the wheel pattern.

Small bolt pattern is a 5 stud pattern, 4" across 2 studs. Same for the wheel pattern.

An original A body 8 3/4 will be 5 x 4", aka Small Bolt Pattern.

There are numerous ways to make your original A body 8 3/4 rear into big bolt, such as purchasing new axles from companies like Moser or shortening original Big Bolt Pattern axles from another vehicle.

 

[69_340_GTS]

Big bolt is a 5 stud pattern, 4.5" across 2 studs. Same for the wheel pattern.

Small bolt pattern is a 5 stud pattern, 4" across 2 studs. Same for the wheel pattern.
.

Not sure what is meant by "across 2 studs" but that isn't how you measure a bolt circle. At least I've never heard of it. For the OP, the "big" is 4.50" bolt circle, and the "small" is 4.00" bolt circle, and if you are trying to use your original wheels you will need to get rear axles with the 4.00" bolt circle. You can easily estimate a five-lug bolt circle's size by doing the following:
http://www.roadkillcustoms.com/hot-rods-rat-rods/bolt-pattern-reference.asp#axzz3WFaKGvRy

Here is another way to measure Bolt Circles:

 

[70DartMike]

69_340, across 2 studs/lugs means exactly what your picture shows, it's measured across 2 of the lugs. Sorry I didn't have a picture to post, but what I explained is the same as your picture.

 

[dozer556]

This is how I've always been told to measure BP:

Not to be a jerk, but it's not as simple as "across two studs". With a 5 lug pattern, the measurement needs to be taken from the back of one stud to the center of the stud directly across from (not next to) it. Someone who is unfamiliar with this could measure across the wrong two studs and come up with an incorrect dimension.

 

[69_340_GTS]

This is how I've always been told to measure BP:

Not to be a jerk, but it's not as simple as "across two studs". With a 5 lug pattern, the measurement needs to be taken from the back of one stud to the center of the stud directly across from (not next to) it. Someone who is unfamiliar with this could measure across the wrong two studs and come up with an incorrect dimension.

That's what I was getting at. OP is obviously just starting out on the Mopar journey, so it's always a good idea to clarify stuff.

 

[70DartMike]

This is how I've always been told to measure BP:

Not to be a jerk, but it's not as simple as "across two studs". With a 5 lug pattern, the measurement needs to be taken from the back of one stud to the center of the stud directly across from (not next to) it. Someone who is unfamiliar with this could measure across the wrong two studs and come up with an incorrect dimension.

You're correct, I should have clarified which two studs to measure across.

 

[Mopar Tim]

You're correct, I should have clarified which two studs to measure across.

Well I have never measured the 4 inch wheel pattern, till just now!. you are correct. Another Mopar curiosity. I always thought it was center to center,, not:cheers::color:MT

 

[396 Signet]

The 4" pattern uses 7/16" studs whereas 4.5" uses 1/2" which are substantially stronger. Many misinformed installers have snapped off or over-torqued the studs on the small pattern.

 

[70DartMike]

The 4" pattern uses 7/16" studs whereas 4.5" uses 1/2" which are substantially stronger. Many misinformed installers have snapped off or over-torqued the studs on the small pattern.

Yes, and don't forget, often the drivers side studs were left hand thread (the nut spins on the opposite way). That throws people off too.

 

[2 Darts]

All drum brake cars were 5x4" pattern. (SBP)
All disc brake cars prior to MY '73 are 5x4" pattern. (SBP)
All disc brake cars MY 73-76 are 5x4¼" pattern (BBP)
All cars prior to MY 73 originally used LH thread wheel studs on drivers side. (Theory was that they would tighten by inertia as RHs do on the passenger side.) Look for L stamped on threaded end of stud. Because of so much confusion, many shops would swap the LH for RH studs.

 

[66fyssh]

...and to be very clear, Left Hand Threads (the ones with an "L" stamped into the end) loosen by turning to the right and tighten by turning to the left.

Oftentimes people that don't know Mopar will break the left hand studs by trying to loosen them by turning left, like "normal" lug nuts. What they are really doing is tightening them until they break off!!!!! As was stated, the driver's side of the car had left hand threads and the passenger side had right hand.

 

[BillGrissom]

I'll add a few snippets:

Many cars thru the 1960's (even Japanese) had LH thread wheel studs on the left side. You can find charts on the web. Somebody proved they were less-likely to loosen, but that proved too complex for people.

SBP is identical to today's 5x100 mm bolt pattern (for practical purposes), but that doesn't help since all cars with that pattern are FWD and those wheels don't work (wrong "back-space" for our cars).

The OP should insure that his 8-3/4 rear has the correct width. I am guessing he has an early A (always tell us), which were narrower than 1967+ cars.

Spoke wheels might be an option for SBP. My 1964 Valiant came with them. I don't know the vintage, but "made in China" so probably fairly current. The adapter has 3 bolt patterns, one of which is 5x4"D and fits my car, and is "lug-centric" (i.e. centers via the nuts, not a "hub register" hole). The main problem is that one must use an open-ended wrench on the nuts (perhaps a real thin socket would work, say Snap-On?). Interestingly, the center spinner nut which secures the wheel is LH thread on the right side (they are labelled). Not sure why that is opposite our lug nuts, but must be a theory. I need to get a spoke wheel spare since that would make a road-side repair much simpler. Don't know if these 14" wheels will clear disk calipers.