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I e-mailed someone about a set of wheels for my 1992 VW Jetta.
I was asking if a certain set would fit. 4x100's, 16x7, 42mm offset with 205 45 rubber. He said they will fit fine. Now, i believe my car has a 38mm offset. and he said the 42mm offset will still let the wheels fit fine without the use of spacers. Is this true?
 

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Re: Offset Question - False information? (Moosar)

You say that your car has a 38mm offset, but really your existing wheels do. How wide are the wheels with the 38mm offset ??
The offset (ET) is the distance from the centerline that the wheels mount to the hubs. Backspacing is the distance from the inner rim edge to the mounting surface.
You need to alter the offset when you change rim width in order to maintain the same backspacing.
So, if the 7" wide wheel has an offset of 42mm, the backspacing will be 130.9mm.
If your existing wheel is also 7" wide, the difference in backspace will only be 4mm, for a backspace of 126.9mm... less than a quarter inch.
If your existing wheel is only 6.5" wide, ET 38, the backspace is 120.55mm, and the new wheel will be 10.45mm closer to the suspension.
That might be a problem in the rear depending on the car. Usually though, you gain some room behind the rear rim when you go to a larger diameter rim due to the shape of the rear swingarm (which is the biggest limiting factor for backspace on most H2O VW's). In other words, if your existing wheels are 15x6.5, you should still be A-OK, but i would do some measurements between the inner rim and suspension front and rear before laying $ down.
=== what i did to calculate this...
wheel width in inches X 25.4 (25.4 mm in an inch) = wheel width in mm.
wheel width in mm divided by 2 = centerline measurement, which we add the offset to (or subtract in the case of a negative offset).
The center width + the offset = backspace
NOTE : this DOES NOT include the rim bead width, only the distance BETWEEN the beads, which is what your wheel measurements are. Therefore, for true backspace you have to add the inner rim bead width (typically 1/2 inch or 12.7mm).
 

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Re: Offset Question - False information? (Moosar)

quote:[HR][/HR]I e-mailed someone about a set of wheels for my 1992 VW Jetta.
I was asking if a certain set would fit. 4x100's, 16x7, 42mm offset with 205 45 rubber. He said they will fit fine. Now, i believe my car has a 38mm offset. and he said the 42mm offset will still let the wheels fit fine without the use of spacers. Is this true?[HR][/HR]​
If you consider that the factory 14x6 MkII wheel has a 38mm offset, and the 15x6.5" OEM BBS wheel has a 33mm offset,
you have to figure that a 7" wheel would need to have about a 27mm offset, not 42mm. The wider the rim, the less the
offset needs to be. A 15x7.5 Ronal ACT-LS for the MKII car has a 25mm offset which further indicates that the 42mm is
simply too deep for a MkII. 42mm is more like what a MkIII car uses (they use more offset than the MkII cars do).
The most backspace a MkII car will tolerate is 5" regardless of rim width. Anything deeper than that will cause the inner
rim to hit the rear trailing arm, and places the front inner sidewall very close to the strut. Have the guy meausure the
actual backspace of the wheel and report back to you. If it's 5.1" or more the wheels will not fit the car. I know this for
a fact as i've had a few sets of racing wheels with 5" and 5.2" of backspace. The 5" deep wheels barely cleared, but the
5.2" deep wheels jammed hard enough against the trailing arms that they would not turn when i tightened the lugs.
 

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Re: Offset Question - False information? (Moosar)

quote:[HR][/HR]So they WOULD fit?
with 205 40 16's?
here are the specs
http://www.1010tires.com/listwheel.asp?brand=Motegi&model=MR12
the 16x7's, 4x100, 42 mm offset[HR][/HR]​
No, i said that i think a 42mm offset would be too deep for a MkII car. That website doesn't list the backspace
measurement so without that i'd have to say they will not fit, unless the actual backspace of the wheel is 5"
or less. At 42mm, i seriously doubt it. Those wheels don't appear to be intended for a MkII VW. You'll have
to measure the backspace yourself, or have him to it if you don't have access to the wheels. I still say they'll
be too deep for your MkII car.
Randy
 

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Re: Offset Question - False information? (RandyWalters)

i calculate the backspace at something like 5.65"assuming a 1/2" lip on the inside...
that would be a no-go
 

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Re: Offset Question - False information? (RandyWalters)

As long as we are on offset and rim width....would a rim 17x7.5 et 38 be OK on a MK4 Golf? Would it cause any long term problems with the suspension?
(I think the Monte Carlos are 17x7 et 35)
 

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Re: Offset Question - False information? (YetiMan)

quote:[HR][/HR]i calculate the backspace at something like 5.65"assuming a 1/2" lip on the inside...
that would be a no-go[HR][/HR]​
Yes, 5.7" would be about how much it would work out to be on a 7" ET42 wheel. The inner rim would hit something well
before the wheel could even be mounted to the hub. Here's a few examples of rim widths, offsets, and backspaces:
16x7 ET20 = 4.7" backspace
16x7 ET25 = 4.9" backspace
16x7 ET27 = 5.1" backspace
16x7 ET30 = 5.2" backspace
16x7 ET35 = 5.3" backspace
16x7 ET40 = 5.6" backspace

Here's a pic of the result of my extensive offset research; i was able to determine the exact offset i'd need in order to
get fat 225/50-15 race tires under the fenders of my 89 BMW autocross car when everyone said there wasn't room. I
can't even get a popsicle stick in the gap, but the tires don't rub anywhere either (heh heh heh):



[Modified by RandyWalters, 7:48 PM 11-27-2001]
 

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Re: Offset Question - False information? (TurboDave18t)

quote:[HR][/HR]As long as we are on offset and rim width....would a rim 17x7.5 et 38 be OK on a MK4 Golf? Would it cause any long term problems with the suspension? (I think the Monte Carlos are 17x7 et 35)[HR][/HR]​
There's a lot of extra room for more backspace on the MkIV car so it can tolerate a broader range of offsets for a given
rim width. If i'm not mistaken ET38 is the offset on a lot of the aftermarket 17x7.5 MkIV wheels, like the new BBS VZ
for instance

 

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Re: Offset Question - False information? (RandyWalters)

Looking at Randy's picture, thinking... thats cool. Scary... but cool

Randy, you mention the Ronal/ACT LS wheels... did you own these, and what do you think of them ? I put some on my Corrado a few weeks ago (so it's too late to ward me off if you hated em, LoL), and was just wondering.
I liked the size, weight, and old school look of them, and am quite happy with them so far. I have matching spacers on mine from Ronal to make them 29mm offset (8mm spacers on ET37 wheels), which is perfect for the corrado (G60). When i drop a plumb bob from the fenders it Just touches the rim's shoulder at the bottom, and they are a quarter inch closer to the suspension than the stock BBS's.
Anywho, just wondering...
 

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Re: Offset Question - False information? (YetiMan)

quote:[HR][/HR]Looking at Randy's picture, thinking... thats cool. Scary... but cool

Randy, you mention the Ronal/ACT LS wheels... did you own these, and what do you think of them ? I put some on my Corrado a few weeks ago (so it's too late to ward me off if you hated em, LoL), and was just wondering.
I liked the size, weight, and old school look of them, and am quite happy with them so far. I have matching spacers on mine from Ronal to make them 29mm offset (8mm spacers on ET37 wheels), which is perfect for the corrado (G60). When i drop a plumb bob from the fenders it Just touches the rim's shoulder at the bottom, and they are a quarter inch closer to the suspension than the stock BBS's. Anywho, just wondering...[HR][/HR]​
YetiMan,
Take a good close look at the shape and color of the rim edge in my strut clearance pic. Look familiar? It's the inner rim of
my 15x7.5" ET29 Ronal ACT-LS which i'm using as my Bimmer's autocross wheels. I like them so much i also have another
set of the earliest versions with a straight 25mm offset and a deeper outer lip that i use as my street wheels. They've been
my favorite wheels for well over 15 years and still are to this day. The ET25 versions were the ones they made back in the
early 80's. The same exact part number was specified for the E30 BMW and the MkI and MkII VW since they all have the
same offset, bolt pattern, and hubcentric specs. The ET29 set is a newer version of the older ET25 wheel and is similar to
yours; ET37 with a captive 8mm spacer snapped into the backside. My ET29's were from last year's batch and have a sharper
edge to the outer lip. Your recently aquired set has a more rounded outer lip but otherwise are identical to my older ET29 set.

Ronal makes strong and relatively light wheels and i love mine a ton. Ronal also made a lot of the OEM Audi wheels and are
the ones behind the scenes making the wheels for the top BMW tuners such as Hartge, A.C. Schnitzer, and Alpina.

15x7.5" ET25 deeper-dish Ronal ACT-LS:
 

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Re: Offset Question - False information? (RandyWalters)

Thanks for the info ! Yep, they have the slightly rounded rim lip. http://****************.com/smile/emthup.gif
 

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Re: Offset Question - False information? (YetiMan)

VetiMan What would I take into account for the tire width?would I use the foumula that you used just for a 225mm tire instead of for the wheel? and then translate it to the wheel to get the ofset let me know if I'm on track or way off
Ps great post!
 

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Re: Offset Question - False information? (RandyWalters)

quote:[HR][/HR]i calculate the backspace at something like 5.65"assuming a 1/2" lip Here's a few examples of rim widths, offsets, and backspaces:
16x7 ET20 = 4.7" backspace
16x7 ET25 = 4.9" backspace
16x7 ET27 = 5.1" backspace
16x7 ET30 = 5.2" backspace
16x7 ET35 = 5.3" backspace
16x7 ET40 = 5.6" backspace[HR][/HR]​
If what you say is true, how is it that my 15x7 et38 BBS RS, as well as my other set of 15x7 et 35 rims fit my 91 Golf without any problems? I am running a 195/50/15 tire on one set of rims and a 205/50/15 tire on the other.
 

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Re: Offset Question - False information? (marek)

quote:[HR][/HR]
16x7 ET20 = 4.7" backspace
16x7 ET25 = 4.9" backspace
16x7 ET27 = 5.1" backspace
16x7 ET30 = 5.2" backspace
16x7 ET35 = 5.3" backspace
16x7 ET40 = 5.6" backspace

If what you say is true, how is it that my 15x7 et38 BBS RS, as well as my other set of 15x7 et 35 rims fit my 91 Golf without any problems? I am running a 195/50/15 tire on one set of rims and a 205/50/15 tire on the other.[HR][/HR]​
Ah. Two reasons......
Claimed offset specs are not absolutely accurate on all wheels and can vary from brand to brand or model to model. For
instance i have three sets of 14x6 ET33 wheels (MSW, Panasport, and Ronal V2) for my 85 GTi, but the actual backspace
on the three is 1/8" (3mm) different. Three different brands and three interpretations of the same claimed ET33offset.
I've found the same inequities in my many BMW wheels (same claimed offset but slightly varying backspaces).
Another reason your deeper wheels fit without hitting on the inside is because of something i completely forgot about in
my other posts. The trailing arms and strut tubes are angled further inward as they get farther from the axle line, so as
wheel diameter gets larger you can get away with more offset since the strut and trailing arm are angled inward and away
from the rim. My absolute 5" backspace limit was measured using two of my sets of 13" race wheels, but a 15" or 16" rim
can have a little more backspace maybe even up to around 5½". The factory 15x6.5 16v Jetta GLi Wolfsburg BBS wheel is
ET33 which translates into about 5¼".
I had completely forgotten about the effect of the increasingly distant strut and trailing arm angle as it pertains to larger
wheel diameters and i stand somewhat corrected, but i still think ET42 on a 16x7 will hit one or both of these areas on a
MkII. Even if they barely cleared, the wheels would have that "pulled way in" look and look all wrong on the car.
Randy




[Modified by RandyWalters, 9:35 PM 11-29-2001]
 
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