I need some help from those of you who are familiar with the stamping on torque thrust wheels from the last 15 years or so, let's say. My '36 chevy truck had a set of chev-looking rally wheels on it (no GM stamping). I fell into 3 torque thrust Ds and the back pair is marked with "15x7" and they fit fine. I need to buy a 4th wheel and the front torque thrust wheel is stamped with "15x6 4.5" inside the wheel. Now, my front clip is out of an OEM vehicle, but it's a mystery at this point where it came from, so I don't know what bolt pattern exactly I have up front. Instead of measuring the lug pattern and probably getting it wrong, I thought I would ask y'all. Do you think that 4.5 is maybe for the backspacing? Why wouldn't the backspacing be stamped on the 15x7 wheel then as well as the 15x6? The seller told me they are chevy pattern wheels, and All 15x6 ones I see selling are not 4.5, but only 4. I am at a loss and if I buy this wheel in Canada at a wheel shop, it will cost me close to $400 after taxes - not gunna happen. I want to order it from the states instead, but I gotta be sure I am right about it. Thanks for any help! gribbs
The first thing that comes to mind is a 4 1/2 bolt pattern, as in ford or mopar. See if one of the rear ones fit the front. If the bolt circle is too big, you have your answer. 4 1/2 in front, 4 3/4 in rear.
My truck is in storage at the moment, so I can't swap the wheels around, but that is an easy way to tell for sure. I know that is how you measure them, but it is a tricky measurement when you are working with a quarter inch and the top and middle of a bolt. I have the 15x6 wheel here, so I think I will give measuring it a shot now on the inside of the wheel. Thanks guys for the help!
Can you get close to the wheel with a straight edge and a tape measure? You can check real quick if it is back space that way and once you rule that out you can move onto bigger n better things.
No it's not! 4-1/2, 4-3/4 and 5" are bolt circle dimensions, it's a diameter not across two lugs on a 5 lug pattern, if it was 4 or 6 lugs you could measure it that way. Pat
Stop right there and figure out your bolt pattern before you do anything else. 5x4 is dinky mopar 5x 4.5 is ford and bigger mopar 5x4.75 is GM car and 74 earlier van 5x5 is GM big car and truck, van. Yes it is. And you better not measure center to edge on a 4,6,8 lug. And you can do it another way too and probably 3 others
Look closer at the pic, it isn't going center to center. If you measure that way, it's right. I personally measure center to center and add a 1/4" and that gets you close enough to have the correct measurement, which is kind of what the picture shows
I knew I would get shit for this. There are several ways to do it but it is still a bolt circle and it is the diameter of that circle that the measurement number refers to. No need to remember to add 1/4" or if "A" equals something or center to end of stud etc. It's a circle measurement! Pat
If you want to tell the entire industry they are wrong you'll get some shit. Yes Of course it's a pattern based off a diameter, nobody would lay the holes out for drilling in such a way as pictured. But edge to center is how the studs or holes are measured, hook on and eyeball it center- you'll get 4" 4.5", 4.75 , 5.5. Maybe you'll get 114.3 mm 115 mm 110 mm. It's way more accurate than eyeballing the arc between 2 of the studs and measuring thru center to opposite stud.
Of course it is a bolt circle diameter. How EXACTLY do you suggest he measures that exact diameter short of placing the rim,drum,axle in a lathe and touching down a diameter. I gave him a REASONABLY accurate way of measuring to get his lug pattern. Please enlighten us.
And how on earth would you accurately measure that bolt circle diameter on the car, or on a wheel without making some sort of centering fixture?
OR, You can print out this template and check it for certain. http://www.classicperform.com/tech_articles/PDF/boltcircletemplate-1.pdf Personally I always have one of the plastic ones in my car, but that one will do in a pinch. Jim
Judging by this method of measure, I have 5x4.75 pattern. The offset is not 4.5, more like 3.75 or 4. Still strange. I gotta get my truck out and throw it on once and for all, before I make a purchase, I guess. Thanks for your suggestions! One of those plastic templates is something I always thought one day I should own, and this would be the day.
Hope you find this helpful as a wheel rookie will loose his mind. Just so you're on the same page with the wheel industry and can eventually find what you want- Offset is a term used to tell the distance that the wheel mounting surface is set off from center of the rim and "offset" almost always accompanied by either "positive" or "negative" to shown the forward or backward direction from center. Some wheels are zero offset. When measuring an unknown wheel to find the off set requires a simple math equation. The rims total width divided by 2 is considered your "zero" then measure the depth of the wheel mounting surface from the rear lip (aka back space) and distance from zero is the offset. Back space is a older term and that's used to tell the distance from the wheels rear edge back to the wheel mounting surface. It's based on measuring only, no math and contains no regard to the wheels width. So when figuring what wheels and tires are going to fit your truck, the next hurdle you'll cross is "tire buldge". The buldge of the tire, what sticks past the rims edge is what's going rub the body or chassis if things are tight.
Very well said! I had read that times before, but you put it plainly and I am more liable to understand and remember it better for the future now. You get a thumbs up for your teaching! (I am a teacher, btw).
@gribbs one more very important aspect when discussing wheel widths. I know veteran car people know this but many people do not realize that calling out a wheels' width based on the outer lip to lip measurement is not correct. There have been countless wheel transactions (new and used) gone sideways because of this. Even though it might seem odd; true wheel width dimension is taken from inside the inner and outer tire sealing beads. This is every bit as important as using the terms offset, backspace and front spacing. Miscommunicating any one of these will hugely affect fitting wheels on a car, especially early full fendered ones.
The Jalopy Journal
