jeromio Posted March 29, 2001 Share Posted March 29, 2001 Okay, I know everyone is sick to death of this subject, but I'm a little spooked. I was about to press Submit on my order with discounttiredirect.com, the wheel showed "on order", so I called to see what that meant time-wise. The sales guy was typical of your average parts counter type robot - "What year, make and model of car, sir?". Obviously I know they're not going to have any listing, but I follow the drill so I can have a chance to ask my question. He comes back with "Nothing for that car", and I have to scramble to ask about this particular wheel. At each step of my description, Me: "It's a Konig - " Him: "Not gonna fit, Konig doesn't make a wheel for your car, sir" Me: "Do you have a Konig Monsoon-" Him: "No Monsoons are made to fit that car" etc, etc. So, should I be concerned? The robot has me a little scared that I'm gonna have to pay a restocking fee. But that 20mm offset has got to just be perfect.....Right? ------------------ 240Z.jeromio.com Quote Link to comment Share on other sites More sharing options...
Oltmann Posted March 29, 2001 Share Posted March 29, 2001 I think you have it reversed, +20mm will place the wheels further in. -20 would probably be fine though. http://www.tirerack.com/wheels/tech/offset.htm Quote Link to comment Share on other sites More sharing options...
jeromio Posted March 29, 2001 Author Share Posted March 29, 2001 I do want them further in. With the current 8 inch, 0 offset, the tires rub the fender when I hit a bump. So, a 20mm offset should push the tire and rim in, towards the center of the car and away from the fender lip. I guess one thing that concerns me is that others here seem to be getting rims with a much larger offset, for instance, Danno got 5.125 backspaced 8 inch wide rims which translates to 35mm offset. The Monsoon is available with a 35mm offset, but I think a 20mm would be better - unless I'm wrong.... ------------------ 240Z.jeromio.com Quote Link to comment Share on other sites More sharing options...
Danno74Z Posted March 30, 2001 Share Posted March 30, 2001 Hi Jeremy, I have been through this a million times myself - backspacing, offset, etc. etc. Please go to this site below and all will become clear. The rims I ordered have a 5.125" backspace and they are 8" wide. Look on the top of the chart and find 5.0" - 5.25" then look for 8" on the left side scale and where they intersect is you offset. In my case and verified mathematically by the guys at BC my rims are +15mm give or take a mm not +35 as mentioned. +35 would necessitate wheel spacers which I did not want. I hope this helps on clearing things up with offset and backspacing. Danno74Z http://www.wheelmart.com/SPINON.HTM Quote Link to comment Share on other sites More sharing options...
Oltmann Posted March 30, 2001 Share Posted March 30, 2001 Sorry, I misread your post. Personally I wouldn't listed to the saleperson. He will just tell you whatever his inventory system says, and for these old Datsuns it says "NO DATA." Quote Link to comment Share on other sites More sharing options...
jeromio Posted March 30, 2001 Author Share Posted March 30, 2001 Wow. I think the wheel industry definately needs to come up with some better, more consistent terminology. Just continuing with Danno's rims as an example, 8 inch rim, 5.125 back spacing. If backspacing is the dimension between the outermost inside lip of the rim to the mounting surface, then how can that not correspond to a 1.125 inch offset. That is if offset is the distance from the centerline of the rim to the mounting surface. I mean, there's only 8 inches of rim, so that would need to mean that backspacing - half the width (8-4=4) should give you 1.125" = 28mm offset( I think I used 5.25 previously to come up with 35mm offset). Now clearly there is some element of these measurements that doesn't translate as I think it should. I mean, Boyd's is not going to have come up with an incorrect rim - I'm sure of that. It's just that there's some extra stuff involved that's not really specified and isn't intuitive. Some kind of wheel manufacturer "Fudge factor" is in there someplace. I'll be so happy when this is all over with and I have some wheels and rain worthy tires on my car............... ------------------ 240Z.jeromio.com Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted March 30, 2001 Share Posted March 30, 2001 Heh, there's a reason why I put backspacing on th eFAQ as a question I'd love to see an answer for. I hope to learn from your experience! Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 30, 2001 Share Posted March 30, 2001 Not that backspace includes the rim lip thickness (on the order of 1/2") So that's why backspacing, rim width and offset are not directly related, unless you include rim lip thickness. Therefore, offset = backspacing - 1/2 rim width - rim lip width Assuming a 1/2" rim lip: offset = 5.125 - 8/2 - 1/2 offset = 5.125 - 4.5 offset = .625" ~ 16mm (So Danno, that 15mm looks o.k.) So working backwards: Backspacing = offset + 1/2 rim width + rim lip width For jeremio's wheel: Backspacing = 20mm + 8/2 + 1/2 = .79" + 4.5" = 5.29" (remember, I'm guessing a 1/2" rim lip width) Hope this helps, ------------------ Pete Paraska - 73 540Z - Marathon Z Project pparaska@home.com Pete's V8 Datsun 240Z Pages Quote Link to comment Share on other sites More sharing options...
Danno74Z Posted March 30, 2001 Share Posted March 30, 2001 Pete, Thanks for the offset verification on my rims. I worked through the math myself a few times and the most over looked thing is the rim lip. As a quick guide, I found the chart to be handy and quickly give one a good estimate of offset knowing the other variables. Jeremy, based on what you said and Pete's calculations the Konig Monsoons should fit your application. Danno74Z Quote Link to comment Share on other sites More sharing options...
jeromio Posted March 30, 2001 Author Share Posted March 30, 2001 I'm ordering the Konig Monsoons, 4 on 114, 17X8 with 20mm offset. Getting the Kumho's because they're pretty cheap and I like that big water channel down the middle. It's gonna be $1200 delivered. Currently have 14X8, 0 offset with 215 60 firestones which are extra fat sidewall wise. They rub the fender lip in the rear. I'm thinking the 20mm offset will be perfecto - just enough to move the tire away from the fender lip. I have coilovers, so there ought to be plenty of room on the inside (ordering 235/45s). Can you smell the debt? ------------------ 240Z.jeromio.com Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted March 31, 2001 Share Posted March 31, 2001 Thanks Pete - now I'll just wait to hear how his fit FWIW - a friend has FIKSE wheels on his car - WOW what nice wheels. I'm going to check those out before I completely settle but the TSWs are very high on my list. Holy smokes FIKSE wheels are bucks! I knew my friend spent several grand on his wheels but I didn't realize they ALL cost that much over there. Whew, too rich for my Z! [This message has been edited by BLKMGK (edited March 31, 2001).] Quote Link to comment Share on other sites More sharing options...
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