Can Someone Please Explain the Correct Way to Measure Bolt Patterns?

No more "measuring." Call HEIDT'S Hot Rod Shop and ask them top send you a bolt circle template. 1-800-841-8188.

 

All of this goes right out the window with metric bolt circles. There exists a 115mm BC that is DAMN close to a 4 ½, even measures right close center-to-outside, but it won't fit!!

I once had a wheel adaptor in my pattern, which is the only sure way to check if a wheel will fit, because you are checking all five holes at once.

Tony Bones: The reason you measure bolt circle is because THAT is the standard. You cannot machine a five hole pattern with just the distance between edges of two holes. It's hard enough doing a five hole pattern when you have the diameter of the circle!!
Same with measuring axles - you gotta measure from each wheel mounting surface, drum attached. Measure the backing plates (sure, it's easier), and you'll find that NO manufacturer agrees on depth of brake drum and backspacing of backing plate.

Cosmo

 

I have always used the method of measuring across 2 bolts and adding a1/4"
But now I can't remember which cars had which bolt pattern. Calles for a new card to carry around. Keep it simple.

 

Probably a lot 'cause you & every gearhead/racer you knew, and every wheel manufacturer you're aware of - has been doing it wrong (or at least you were).
Try drilling an axle or wheel (pretend you're a manufacturer) using your measuring method, & you'll understand why it's the diameter of the circle that's being measured.....

 

Moser has free paper ones also.....you can fold it up and put it in your pocket.

 

I used the 5-lug method as shown in the above illustration on a '36 Ford wide-five. It showed 10.004" which is about a 1/4" off....10 1/4" is what it should have worked out to.

Then I measured center to center of two adjacent holes. That was 6.025" (6 1/32") and, multiplying that by my 1.7 factor, it came out 10.243" (10 1/4").

I guess we ALL have our own methods.....

 

Yeah, I get that - but MANUFACTURING wheels, or redrilling an axle flange, is a different issue. I thought the subject was IDENTIFYING EXISTING WHEELS - or a wheel stud pattern on a rear or front end.

If you look at "Animal's" drawings - he uses center-to-center measurement for all but the 5-lug configuration. For simple identification of existing patterns, what's the need for the variation in technique? No big deal, but I just don't get it.

I'm not suggesting any other way is wrong. Just noting that (what I knew as) the "accepted" method seems to have changed over the years (everything was simple when I was 25 - LOL). I'm the one who needs to update his thinking (however, I'm still not gonna start pronouncing "Porsche" as "Porsh", like everyone seems to do nowadays - LOL). Guess I just need to "bite the bullet" and spring for one of those little plastic discs.

Bottom line - JohnnyFast has it right. Everyone has their preferred method. As long as you've got it clear in your own head - and have a measuring tape in you pocket (something I always try to carry at swap meets, etc.), you'll probably be fine.

Of course, you could still have problems if you were buying on-line from someone who wasn't sure what the wheels fit. I that case, you'd obviously want to be sure both parties were using the same measuring method, but you should be able to get that worked out before making the deal.

 

When you have 4, 6, or 8 lug wheels, the opposing lugs are directly across from each other, so center to center is the diameter of the bolt pattern circle. With 5 lugs, you have no directly opposing lug bolt/hole so you can't measure center to center. To demonstrate draw a circle with a protractor or using a round object, & draw 5 little circles at the places where the lugs would go, with the large circle intersecting the center of the small circles. Now measure the diameter of the circle (which represents the size of the lug pattern) & across two of the lug circles & you'll see the difference.
~ Paul
aka "Tha Driver"

There is no problem that cannot be solved with the right application of high explosives.

 

does anyone know of a site on the internet of all lug patterns, of all years w/ the American manufactures?

Ie: when did Ford change thier lug pattern?

Does anyone know the lug pattern for a 46 Ford? is it the same as 55?

Thanks

 

Go to this site. http://www.roddingroundtable.com Open it and click on TECH SECTION. tHEN SCROLL DOWN TO ARTICLE ON bOLT pATTERN iNFO.