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09-24-2003, 08:39 AM | #76 | ||
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HOWEVER... you're missing the whole point on this thread -which is to guide the enthusiast in finding a wheel that WILL fit their car so they can get more rubber to the ground, SAFELY, without damaging parts Quote:
Here's a great explanatioin and will hopefully help you understand where I'm coming from: http://www.tirerack.com/wheels/tech/offset.htm --kC
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09-24-2003, 12:45 PM | #77 |
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Here is a calculator that I think works nicely: Wheel Offset Calculator It has a short explanation with it.
According to this calculator, what the original post shows as the ranges and what KC has been trying to explain is accurate: For example, if the STi's stock wheels are 7.5 with 53 mm offsets, the ideal offset for an 8" upgrade would be 47 mm, because the the clearences from strut housing to the inside of the wheel would remain the same; however, the wheel would extend 12 mm more towards the outside. I think the most important part is keeping the inside clearence optimally the same as original while having minimum outside extension of the tire. 12 mm would be roughly 1 in. that seems almost borderline extension to me. |
09-24-2003, 03:23 PM | #78 |
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Width .... Offset
6.5" ....... +53 to +55 7.0" ....... +50 to +53 7.5" ....... +47 to +50 8.0" ....... +43 to +47 Does this apply to all Subaru's? If not, what we need is a list of each year and model with the OE offset and wheel size. Then we can all figure out what we should be buying. |
09-25-2003, 03:01 PM | #79 |
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That got me to thinking about the old "Subaru engineers know what they're doing" line that people use to defend the way stuff comes from the factory. Maybe the engineers only allowed enough room in the fenders for tire/wheel combos that would be safe....
The blistered fenders could have easily been made an inch wider...but they weren't. Maybe the all-knowing Subaru engineers did this on purpose. The theory goes like this: Subaru engineers know best...nearly any combo that fits is safe...anything wider means going to a widebody which means you're on your own. Only time will tell if there are common problems with front wheel bearings going bad. |
10-03-2003, 07:59 AM | #80 | |
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--kC |
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10-03-2003, 11:27 AM | #81 |
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Is there any ideal offset and wheel size (with tires of course) that wont rub on a GC8?
I mean, would an 18x7.5 and a +50 with a 225/40/18 tire not rub? Or would it? Would I need something like a +53 ? Keith |
10-04-2003, 02:20 PM | #82 |
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what offset would you suggest for a 17x8.5
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10-12-2003, 12:16 PM | #83 |
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Yep, KC is right!
I have a question of my own, though. I have heard of problems with the 18x7.5s rubbing with a +48 offset. I have been recommended a +44 offset. I don't know what tires they were using, and they could be the problem. Has anyone else heard about this from people that have tried it, and not from dealers? I am looking at getting the 18x7.5 Volk CE28 or LE28s. Thanks- Nevin |
10-14-2003, 07:03 PM | #84 | |
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10-14-2003, 10:56 PM | #85 | |
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- Kean |
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10-15-2003, 07:15 AM | #86 |
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Yeah, that's kind of what I figured. I know 44 is still right around the "nirvana" range. Thanks for your help!
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10-16-2003, 12:38 AM | #87 |
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yeah this "nirvana" range is gonna make me pull a Kurt Cobain. so what are we sayin here.....that 18x7.5 with +44 is gonna be safe or what?
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10-16-2003, 04:20 AM | #88 |
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Yes, they should work. The guy that told me this actually has them on his car with the +44 offset.
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10-16-2003, 06:27 PM | #89 |
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excellent....now if I can just find a place that stops telling me they have them in stock when they really don't. Do these people not like money???
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10-21-2003, 05:44 PM | #90 |
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Ok guys, after reading this post I have more knowledge about the correct wheel/offset issue, but I'm also a little confused. Could you please let me know if this combo would work on my '02 WRX sedan:
5 Zigen Super Six wheels 18x7.5 w/ 48mm offset P235/40ZR-18 tires (not sure of the brand yet) My car is lowered approximately 1.5 in the front and 1.4 in the rear w/ H & R springs. Thanks so much for any advice. My main point of concern is the offset and the tire size, should I go with P225 instead of P235? |
11-06-2003, 01:58 PM | #91 | |
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Re: The Offset Information Thread
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11-06-2003, 03:57 PM | #92 |
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Also, is 8.0" wide the widest we can safely go on the wheel bearings???
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11-08-2003, 03:00 PM | #93 |
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Anybody got a picture of the wheel bearings? This thread is worthless without pix.
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11-08-2003, 09:01 PM | #94 | |
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BTW, they can't be removed or installed at home unless you have a hydraulic press. |
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11-19-2003, 02:08 AM | #95 |
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"Wheel bearings" - the rotating support for the wheel hub(that thingy with 5 bolts sticking out that you bolt your wheel to). Now these bearings have a load rating of (educated guess-check my name) somewhere in the neighborhood of 1600 to 3000 lb load, and there are two of them at each corner. as long as the centerline of the tire stays the same, you could put on a 20" wide tire and not change the load. Changing the centerline with more or less offset will change the leverage, but 5mm is only .2" and would be relatively nothing to the bearings. Clearance, both inside and out is the rub(pun intended). That said what I need is someone with experiance to let me know if I can get away with lowering 1.8 in front and going with a 17x7 with yokohama 215-45 on my wagon.
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11-19-2003, 02:28 AM | #96 |
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T-WREXX,
I haven't heard of any problems with the 5zigen wheels, so 48 should be correct. The whole 44 thing was with the CE28N and LE28N wheels only. |
11-24-2003, 04:10 PM | #97 | |
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12-08-2003, 08:13 PM | #98 |
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For those interested, the formula for calculating offset is:
[(Back Space - 0.5) - (wheel width / 2)] *25.4 Back spacing will change while offset should remain fairly constant. Not the other way around. That is how proper suspension geometry is maintained. Back spacing is measured from the outermost edge of the back of the wheel (including the lip) to the mounting surface of the wheel. Use a straight edge across the back of the wheel and a tape rule to measure the distance to the mounting surface. Measure your factory wheel to get offset. Use that offset number, plus or minus 3mm, and you should have a proper fitting wheel. Changing backspacing or offset to clear brakes may work short term, but bearing, ball joint, and tire wear will be dramatically increased. The wheel needs to be designed with proper spoke clearance and offset to work correctly on the car. Hope this helps. EAH |
12-09-2003, 12:19 PM | #99 | |
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12-09-2003, 11:17 PM | #100 |
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Kean:
I can appreciate your question. That is how I learned. No, I don't think 3mm will cause "drastic" problems in any specific area. The degree of deviation from a specification is proportional to some negative result. In other words, a wheel offset difference of 12mm might cause greater problems than one differing by only 3mm. Keep in mind that a wheel sticking out and added 1/2 inch has greater leverage and will change handling characteristics and increase wear. The offset calculation formula originally came from Weld Wheel Industries' website, a couple of years ago. It is however the standard. It was provided as a guide and for those who needed to find offset for their wheels. As far as my assesment of wear, I've driven dozens of cars and trucks over the years and have noticed differences in driving feel and parts wear with offset differences of only 5mm. As somone mentioned in an earlier response, a major difference in offset might cause a dealer to refuse warranty coverage of wheel bearing repairs. The bottom line is, wheel offset should remain as close to OEM design spec as possible for best results. Differing wheel widths and back spacing can change since those aspects really only effect clearance of some parts. Thanks, Eric |
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