Bolt Patterns 5X120MM or 5X4-3/4"(120.65) ?

Discussion on wheel & tire issues
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Capeasy
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Location: Downey, CA.

Bolt Patterns 5X120MM or 5X4-3/4"(120.65) ?

Post by Capeasy » Tue Dec 01, 2020 6:53 am

I need to put this topic to rest guys. Since it was Cyber Monday today I thought I would once again look for some 18 X 10" one piece alloy wheels with an offset of about 40 to 50 mm (6-1/2" to 7-1/2" Approx. Back/space) which isnt easy to find. But came real close with a company in WI. called "Custom Offsets" that has an endless choice of wheels at a fair price until you get into the 2 or 3 piece wheels. And then called a couple more companys, but whats confusing is when they look in their fitment charts.
One says our bolt pattern is 5X4-3/4" in his fitment book the other online company says 5X120mm WTH? :?: :? So I purchased a couple wheel stud pattern Template gauges, the plastic ones with the multiple holes in them. And I tried some American racing spoke wheels off my 67 Nova which is a 5 X 4-3/4" using the 1/2-20 studs and those wheels fit perfect ! And when I use the Template gauge the 5 X 4-3/4" lines up perfect. When I hold up the template with the 5 X 120mm our PPV pattern is a bit bigger (Approx. .030) which is the difference between these two patterns that GM is using now. Can anyone out there finally put this to rest and either confirm with me or show me in a GM publication otherwise. Yes I know the difference is only about .030 between the two patterns. I have Willwood disc brakes all the way around on my 67 Nova and I did have some 5 X 120 rollers on there to just move the car around while were building it but I wont tighten up the lug nuts because Willwood said it may fit but its not correct and It'll bend my studs.
Thanks Guys
Walt (AKA:Capeasy) So. Cal.
2013 Caprice 9C1,Huron white, Blackbear tune,DOD Delete, Texas Speed stage 2 cam with all the goodies, Circle D 258 mm converter, 3200 stall. Spectra CAI, 3.45 Diff, deep trans pan. BlackWidow Venom exhaust,Granatelli oval cutouts, Doug
Thorley tri-Y headers, Pedders coilovers,Tower brace,

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kevink
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Re: Bolt Patterns 5X120MM or 5X4-3/4"(120.65) ?

Post by kevink » Tue Dec 01, 2020 3:35 pm

It's 5x120. There, it's put to rest, but this topic has already been beaten to death.

That being said, 5x4.75 do work and I have not seen one documented case of failure and lots of people run that pattern on 5x120 cars (myself included).
2011 9C3: 11.48 @118.

Capeasy
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Location: Downey, CA.

Re: Bolt Patterns 5X120MM or 5X4-3/4"(120.65) ?

Post by Capeasy » Thu Dec 03, 2020 9:49 am

Yeah I'm probably overthinking it. I wonder why GM engineers would make such a minor change like that, its only .030 maybe just to screw with us. Lol
Walt (AKA:Capeasy) So. Cal.
2013 Caprice 9C1,Huron white, Blackbear tune,DOD Delete, Texas Speed stage 2 cam with all the goodies, Circle D 258 mm converter, 3200 stall. Spectra CAI, 3.45 Diff, deep trans pan. BlackWidow Venom exhaust,Granatelli oval cutouts, Doug
Thorley tri-Y headers, Pedders coilovers,Tower brace,

lastcall190
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Re: Bolt Patterns 5X120MM or 5X4-3/4"(120.65) ?

Post by lastcall190 » Thu Dec 03, 2020 10:53 am

Metric market car vs imperial unit market? Though i am not sure that would explain the cts wheels also being 5 on 120
2012 Caprice
2008 CVPI

Both gone but not forgotten...

enginelord
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Re: Bolt Patterns 5X120MM or 5X4-3/4"(120.65) ?

Post by enginelord » Mon Dec 07, 2020 12:54 am

Boy, I spent some time on this one myself. Heard a lot, from many opinions. My take, 120.65 work with no issue. Many wheel manufacturers agree. It does 'flex' studs a very tiny bit. Some wheel hole and lug combinations more than others, but not an issue. The negative you heard is based on an exemption of liability from wheel manufacturers, because the math is not perfect. Kinda like changing from your original design tire size and/or offset is also very wrong. And a liability to anyone who changes it. But the physics of risk 'are' within very safe parameters. All hardware flexes. Actually an over-torque or an under-torque is at least twice as likely to fail rather than a bit of flex. I'm not a physicist just an experienced opinion from a 36 yr tech. The difference is just not enough to matter enough.

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Re: Bolt Patterns 5X120MM or 5X4-3/4"(120.65) ?

Post by Navy Lifer » Wed Dec 09, 2020 8:08 am

Well...I agree with Wilwood.

The Zeta platform, along with Cad CTS (2nd Gen), Alpha Camaro/ATS/CTS, and even FWD Regal, Impala & Malibu use 5 x 120 (4.72") bolt circle - and now C8 Corvette. Zeta is Gen5 Camaro, G8, PPV, and SS sedan - all using same hub register and 14mm wheel studs.

The issue is when a 4.75 wheel (assuming from Corvette most commonly), the wheel center bore is larger than the hub register - 70.3 vs 67.1. The right thing to do is to run a proper wheel made for the chassis, but if the BC is going to be ignored, which side loads wheel studs and gives weird torque readings, as well as high load concentration on a smaller area of the lug & tapered seat in the wheel....the VERY least that should be done is to use hub centering rings.

Don't try to put OEM 5x120 wheels on a Corvette (not that there would be any reason) - they won't fit, due to the difference in hub register size.

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