114,3 and 115mm ..... Hoax or fact?

[LMP]

Or..how to make a short story long....
...and if you start reading this thread......read it all through to the last post....
As my wife just bought a new Suzuki SX4, I was in the process of preparing for new snow tires. I have always used separate wheels for that purpose and the specs for the sx4 was 6in wide, 5 x 114.3mm (4.5in) bolt pattern, deep offset. I happened to have exactly the right fit, 4 Dodge Intrepid/Caravan wheels (recently acquired from discarded son’s car) equipped with partly used winter tires. But I also had 4 empty wheels for my ’93 Transport that had been provided by the GM dealer at the time I bought the TS in ‘93. The claimed specs on the internet for these GM wheels is 5 x 115mm bolt pattern. I wondered if GM used rounded up specs ...is 115 a short label for actual 4.5in (114.3)...as the difference would merely be 0.7mm diameter, so 0.35mm radius...that is 0.014in or 1/70 in..... But if the fit is same, it was easier to intall new tires for the SX4 on the empty wheels ...and eventually keep the Intrepid wheel/tire set for the TS . I searched various forums on the matter and the opinions varied from “b....it ..they are the same” to “no no...using the wrong one will make the first nut pull the wheel 0.35mm off center thus causing tire unbalance...etc....specially if they are not hub centric”...which is the case.
In doubt, I did have the tires taken off the Chrysler 114.3 rims and install new tires on them. Then, I went in the process of installing the used tires on my empty TS rims.....and I happened to pay attention to a label on the inside of the rim normally hidden by the tire....and to my stupefaction....I read what I had not noticed in 18 years : it read CHRYSLER......!
Not do not tell me that in 1993, Chrysler, that had been using 4.5in (114.3) bolt circle for decades...would have had different 115mm rims used on none if its cars but that GM would use for its cars....or that I had been unknowingly using “wrong” 114.3 rims for years on my alleged “115” mm TS..without ever noticing any off center or unbalance.
Now....tell me...has someone actually measured ...if possible..this alleged 0.7mm diameter difference between 114.3 and 115mm bolt circles? Why would GM switch to 4.514 in. bolt circle instead of 4.500? In the past, GM used 4 5/8 or 4.625in , that would be 117.5mm..but why bother to go to 115 in lieu of 114.3?
OK..what is your opinion? Was my effort to go blindly by the specs the necessary thing of was I fooled uselessly by a hoax ?

[500hpgtx]

HI Louis!

I would not think twice about the difference. What I believe is aggravating is that a friend wanted to use G6 wheels on his 2001 GTP. The GTP has our familiar 115mm bolt circle. The G6 has a 110mm bolt circle. No dice is what I told him. I also believe that your hoax is correct.

I had a 72 Cadillac Eldoradowith te 501 C.I. engine. The same piston for the
455 olds was a lot less than for the caddy. Have a great Christmas.

[LMP]

This is what GM was providing in 1993.
Kelsey Product X45315 KH120623 CHRY
MOPAR 15x6 5x4,5" (114.3)
My interpretation: 115 is a nominal label for 114.3

[LMP]

No, no I could not just look and guess. I did have to measure. And I did.

Here is the process: as the imaginary circle diameter cannot be measured directly with a five bolt pattern (it can with a 4 or 6 bolt pattern) I used a digital vernier to mesure the distance between two alternate bolt centers: not adjacent, skip one and go to the second bolt. THis is the largest distance that can be actually measured on this setup.

Now here is the calculation, for those who like to peek at a little bit of trigonometry.
a) a triangle is formed with summits a,b,c opposing sides A,B,C : summits a and b are the center of alternate bolts, and the third is the center of the hub. The angle formed at the center with the radius (between sideA and side B) going to each alternate nut is 2/5 of a circle, hence 144 degrees.
b) A and B, the two radius, are the alleged half diameter of the bolt circle, namely either 114.3/2 or 115/2
c) the length of the third side, the distance between the center of alternate bolts, is calculated with the equation C = sqr(A*A + B*B -2*A*B*cos(c))
..you can do it with the scientific calculator or use triangle calculators on the net.

Based on alleged bolt circles, we should have

C = 108.706 mm for 114.3mm (4.5in) bolt circle or 57.15mm radius
C = 109.3715 mm for 115mm bolt circle or 57.5mm radius
geometry www.avigex.ca/xport/hubcircle.jpg

I trained the digital vernier with measurements using alternatively inside and outside measurement prongs to alleviate visual illusions when measureing from the stud centers. I also measured outside of the studs, and inside of the studs and averaging the 2 readings for the center..
inside measurement www.avigex.ca/xport/ver5s.jpg
outside measurement www.avigex.ca/xport/ver2s.jpg
I took tens and tens of measurements to extract an average reading from the sum of all readings thus taking care of over and under measurements. Measurements were consistent within a very small margin of variation . Measurements were conducted on both front and rear hubs on the car, and on three other hubs on the bench, two front and one rear ( taken off the car for bearing hum, a classic on the TS) .


So here is the punch. Measurements fell consistently within 107.9 and 108.9, most near to 108.6 with a few exceptions over 109, thus giving an average of 108.65, very near to 108.7 that would correspond to 4.5 in bolt circle. I extended the vernier to 109.3 and in that condition, the prongs of the vernier fell ostensibly outside the center of the studs. So conversely, the 115mm convenience label would turn out to be even less than 114.3, as tested on seven GM wheel hubs that GM labels as 115 One of the hubs on the table, though, visibly from a different manufacturer, was just a little over all the others and provided an average (of ten readings) at 109.077mm, hence between 108,7 and 109.37, and corresponds to almost midway between 114.3 and 115.

Bottom line: none of the measurements, even if we isolate the highest readings, prove the 115 label. "GM proprietary" 115 label IS actually closer to standard 4.5in 114.3mm.

WIth that number of takes, the residual error in measurement is dramatically small....another book on statistics would have to be opened here....The only way these measurements could have been significantly false would have to involve a faulty digital vernier but do not have any doubts.....I will go to that length and test another vernier agaisnt mine. Any discrepancy WILL be reported.......

[LMP]

NEW FINDINGS: doubt is the base for science.....so Well....yes...case revisited...new conclusions....
With results from the bench hub taking distance from "on car" mesurements, (see previous), doubts on my alleged conclusions started to install. Remember that initial measurements "on car" were tentatively using the apparent stud centers.... and these seemed to come smaller than following "on the bench" measurements once I found the discarded hubs....I must conclude that visual illusion was part of the game.

Bench measurements were easier to control...so I discarded all other measurements and started again with all the hubs I had..more than I had found initially....I happened to have six "scrap " hubs (3 used in first takes, then found three more, including 2 rear for Intrepid ) and in fact .... .. 1 of the first 3 front hubs came from my son's Intrepid.... They are almost identical, except for the way the three bolts hold them to the car strut: on one car, the threads belong to the strut, on the other, the hub unit has the threads....I think that I was mislead ... forgive me if I mislead you.
I paid extra attention to clean the studs with power wire brush so no foreign particle could interfere .
After separation of the two types... I made separate new measurements "by type" .....and the difference really appeared. And....it was easy to stack together the two types, stud against stud....and even visually, there, one directly against the other, there was a difference....small yes, but visible.....(PHOTO COMING) SO I confess, first mistake was to try to pinpoint stud centers on the car.....the other was I had the two types mixed on the bench, having forgotten that at one time, my son had his Intrepid hubs changed in my garage....
ahhh...so my GM dealer goofed in 1993....with obvious "no consequence" though.....as 500gpx suggested...
WHy in the hell did GM go to 115.....when 4.5in 114.3 is almost the norm all over the place, specially the Japanese, Camry, Sonata.... Suzuki....... ahhh... anyway....

....OK now.....let's talk about theories for climate changes.........

[Jrs3800]

No idea why GM did this... We have had people on another forum run the 114.3 wheels on the 115 hub but we really shy away from this due to the slight difference...

I have not seen anyone have serious issues running a 114.3 wheel on a 115 hub, but on the same note its not a risk I want to take...lol

[CANADA43]

LMP, you are a master of investigation (and must have more time for it than most of us), not to mention a major contributor of info to so many; I have seen your helpful posts all over the forums. i appreciate your detailed approach and plethora of photos and diagrams.
What would you see if you fit the actual hubs of the SX4 and the TS on each type of wheel (114.3 & 115mm)? Would you see that the wheels' tapered seats for the wheel lug nuts are concentric (or not) with the 5 studs protruding through? That should be a easy visual check for size match.
Best regards,

[borat2001]

Hi there guys, I am in the UK, I have a Chevy/GM Captiva (Holden) which has a PCD of 115mm, I have tried to install a set of 20" wheels with a PCD of 114.3 and they will not fit, the first 3 nuts go on ok, but ten because the wheel is out of line the remaining 2 nuts will not tighten properly. I was not gonna risk running the car on the wrong size wheel/hub/PCD! Hope this helps.

[LMP]

Read that....and yes, with brand new mags prefectly honed, this slight difference will probably come as obvious.....thanks for the input.

[WelmoedJ]

Interesting thread.
Now that you mention there may be different bolt pattern sizes on the TS.

My 1995 TS has the standard light alloy wheels.
From new it always has been difficult to get the rear wheels off.
Trying to get them off needs a kind of wobbling motion and I think these wheels rub against the bolts.
After I decided to start using winter tires I bought from a junk yard 4 steel wheels. Turned out these wheels came off of a Chrysler (Voyager?).
Anyway these steel wheels are by far easier to remove and replace than the light alloys.

Reading this thread I now presume the light alloys may have a slightly different bolt pattern size, causing the cumbersume removal and replacing of the wheels.

I do have the official 1995 service manuals but I have been unable to find any reference to the bolt pattern size in the general or wheels sections.
Perhaps they felt this not to be of importance, or I overlooked that info.
I have the Haines manual as well, but not here so could not check if that manual contains bolt pattern info.