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No stock are 165/70x13, I made a mistake in my answer above it should be 165/55x15 [I corrected it]
 

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No stock are 165/70x13, I made a mistake in my answer above it should be 165/55x15 [I corrected it]
Umm, that is an odd tire size, and won't match the stock tire diameter. The stock tires were 165/78-13 (sometimes 165/80, or a lettered equivalent such as A78-13)

Most folks use 205/50-15 tires for that size of rim. I went with 195/55-15, as they are more available, a bit lighter, and are easier to turn while still providing more than sufficient rubber on the road
 

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Umm, that is an odd tire size, and won't match the stock tire diameter.

Most folks use 205/50-15 tires for that size of rim. I went with 195/55-15, as they are more available, a bit lighter, and are easier to turn while still providing more than sufficient rubber on the road
Yeah the 205's seem to be mentioned in quite a few threads. I'll take a look at the 195's. Thanks for the info.!
 

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Umm, that is an odd tire size, and won't match the stock tire diameter. The stock tires were 165/78-13 (sometimes 165/80, or a lettered equivalent such as A78-13)
165/70x13 is a normal and common size for tires at least here in Europe. The number after the slash in this case 70 is the height percentage of the sidewall of the tire relative to the width of the tire.
Height percentages in Europe are 85, 80, 75, 70, and so on.
Take a look here: TIRE SIZE / SPEEDOMETER DEVIATION here you can see which other tire and rim size you can use without having much deviation on your speedometer
 

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I am quite familiar with tire sizing, thank you for your advice. The factory tire for the Opel GT was not 165/70-13. I just recalled that those tires were also sometimes labeled 165-SR-13.

The "odd size" and incorrect diameter I referred to was your suggestion of 165/55x15. I just looked them up, and were mainly used in Alfa's and a few Citroen's back then.
 

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I am trying to understand the changing to the above mentioned wheels at the top of this thread. To accomplish the fit correctly one would need wheel centering rings to make up the difference in the hub center 73, to reach 57.1? Am I looking at this correctly?
 

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I am trying to understand the changing to the above mentioned wheels at the top of this thread. To accomplish the fit correctly one would need wheel centering rings to make up the difference in the hub center 73, to reach 57.1? Am I looking at this correctly?
Not quite. The front hub on an old Opel requires a wheel hub opening at least 57.1 mm (same as older BMW's and VW's with the 4 x 100 mm stud pattern). But Opels are "lug-centric", versus "hub-centric", so the lugs do the wheel centering, not the hub.

As a comparison, older Honda and Mazda wheels that have the 4 x 100 pattern may NOT have a large enough hub opening (Honda spec is 56.1 mm, Mazda spec is 54.1 mm). But some wheels will fit, especially after-market rims.

HTH
 

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That makes good sense. So these wheels would simply need to be bolted on and would work fine with no wheel centering rings required. In fact, as long as wheel hubs exceeded the 57.1 of the Opel hub opening, the wheels would work as far as hub criteria is concerned. Correct? Keith, you are always quite helpful, thank you.
 

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Not quite. The front hub on an old Opel requires a wheel hub opening at least 57.1 mm (same as older BMW's and VW's with the 4 x 100 mm stud pattern). But Opels are "lug-centric", versus "hub-centric", so the lugs do the wheel centering, not the hub.

As a comparison, older Honda and Mazda wheels that have the 4 x 100 pattern may NOT have a large enough hub opening (Honda spec is 56.1 mm, Mazda spec is 54.1 mm). But some wheels will fit, especially after-market rims.

HTH
Hi All- Keith is well versed on this subject. Let me add or clarify something- Opels sold in the US, at least since 1968, are Hub-Centric- that is, the rim centers on the ledge in the rotor hub or the end of the rear axle... that is the best way to center the rim. The lug nuts or bolts' only function is to fasten the rim to the hubs. I've been in the tire business since 1969, lots of high-end cars, track cars, show cars, daily drivers etc. We have cars come in with persistent vibration problems- "had these balanced a number of times and still have a vibration..." Mostly happens on cars (nearly any car!) where aftermarket rims were installed without! the centering rings- Step one is to install the centering rings, and generally the vibration is cured! Of course you can run without them, but you're likely to have vibration at speed. Fact. Rim manufacturers drill a larger than needed center bore so that particular bolt pattern can fit many different cars with the same pattern. Then! the centering rings will center things and you have a smooth ride! We're always amazed that people (the installer, the owner, whoever) did not install the rings. Usually they come with the new rims, sometimes you have to purchase them in addition to the rims. Do that. It'll serve you well! Last bit of free advice: Stay at or as close as possible to the original offset! The further "out" you place the new rims and tires, for that muscular, racy look- usually a heavier combination than the original, the more likely you are to invite vibrations, steering wheel shake, and "darting" left and right .... I've learned these things the hard way... Comments?
 

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Hi All- Keith is well versed on this subject. Let me add or clarify something- Opels sold in the US, at least since 1968, are Hub-Centric- that is, the rim centers on the ledge in the rotor hub or the end of the rear axle... that is the best way to center the rim. The lug nuts or bolts' only function is to fasten the rim to the hubs. I've been in the tire business since 1969, lots of high-end cars, track cars, show cars, daily drivers etc. We have cars come in with persistent vibration problems- "had these balanced a number of times and still have a vibration..." Mostly happens on cars (nearly any car!) where aftermarket rims were installed without! the centering rings- Step one is to install the centering rings, and generally the vibration is cured! Of course you can run without them, but you're likely to have vibration at speed. Fact. Rim manufacturers drill a larger than needed center bore so that particular bolt pattern can fit many different cars with the same pattern. Then! the centering rings will center things and you have a smooth ride! We're always amazed that people (the installer, the owner, whoever) did not install the rings. Usually they come with the new rims, sometimes you have to purchase them in addition to the rims. Do that. It'll serve you well! Last bit of free advice: Stay at or as close as possible to the original offset! The further "out" you place the new rims and tires, for that muscular, racy look- usually a heavier combination than the original, the more likely you are to invite vibrations, steering wheel shake, and "darting" left and right .... I've learned these things the hard way... Comments?

This is right on. I run vintage Centerline wheels on my 69 Z/28, and on my 68 El Camino. The ones on the El Camino are old enough they still use beveled lug nuts. The Camaro uses shank type nuts. I had centering rings made to fit. One of my buddies saw the Centerlines and said: "don't you hate that you have to retorque the lugs every so often?" I told him that with the rings, I had to do no such thing. The issue is magnified 10x with shank type lug nuts, but the same principle applies even if you use beveled lug nuts.

Some time in the mid 90's BMW changed the hub dimensions on all the 5 lug cars. The later wheels would bolt up to the earlier cars, but ALWAYS vibrated unless hub centric rings were used.
 
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