Danno74Z Posted April 29, 2000 Share Posted April 29, 2000 I'm trying to figure out what are the largest wheels and tire combinations one can run under an older Z. I'm looking at two scenarios; first, without any modifications except lowering springs and second, with coilovers. Also, what backspacing and offsets are being used? I looked at the JTR book and I would like some additional information. Any help would be great. Thanks all, Danno74Z Quote Link to comment Share on other sites More sharing options...
pparaska Posted April 30, 2000 Share Posted April 30, 2000 Jim Biondo did all that research for me, and I ended up buying his wheels and tires (he went to 5 lug wheels, C3 Vette stub axles, 300ZX front hubs, Integral SSR wheels). Jim had the wheels I now have on his stock rear fendered early 260Z (same as my 73) with 2-1/2" coil overs. He had these wheels custom made to fit the widest 17 inch combo in there. (The wheel maker was WRD, which is out of businesss now.) The rear wheels are 17x9s with 149mm backspacing. The tires are 255/45/17 Michelin Pilot SX MXX3s. Note that tires from other manufacturers of the same size can be larger, enough to not fit, since Jim really maxed out this combo. In fact, it's maxed out such that you mount the coilover sleeve up high on the strut and have to use short (8" with the 240Z strut isolator) springs that have to be at least 275 lb/in to stay out of coil stackup for a stock weight car hitting dips. I also had to trim the fender lip a bit (you can't tell from the outside of the car unless you look up under there.) BTW, the fronts are 17x8.5s with 235/45-17s. I don't think going to 18s would buy you much, but maybe a 265 could fit on maybe 18x9.5 wheels. HTH, ------------------ Pete Paraska - 73 540Z - Marathon Z Project - pparaska@tidalwave.net">pparaska@tidalwave.net - Quote Link to comment Share on other sites More sharing options...
Owen Posted April 30, 2000 Share Posted April 30, 2000 I fit some 16 x 10 Hayashi Racing wheels on my 73 and it seemed like they were still too skinny...? This is with stock suspension. Owen ------------------ http://www.homestead.com/s30z/index.html Quote Link to comment Share on other sites More sharing options...
Mikelly Posted May 2, 2000 Share Posted May 2, 2000 Im using 15X8 inch wheels with Zero offset and I run 265-5015 out back and 225-50 up front. I am not using coil overs and I have flares on the rear. I have no clearance issues. Also, the car pulls well over a G. Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
MYRON Posted May 2, 2000 Share Posted May 2, 2000 I am using 16x8 weld draglites with 4.5" offset,using 205/50/zr yokohama 520's... see members rides......Myron Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 3, 2000 Share Posted May 3, 2000 Referencing Fikse's site (the best description of wheel terminology I've seen) http://www.fikse.com/cad.html they have the following graphic: notice the difference between "rim width" and "overall rim width". Overall rim width is the standardly referenced rim width with twice the wheel lip width added to it. So when converting backspacing to offset, you need to: subtract the rim lip width from the from the backspacing, then subtract half of the rim width to get the offset. The rim lip width is generally about 10-15mm. So for a 149mm backspacing, you get: 149mm-15mm-(9in/2)*25.4mm/in = approx. 20mm positive offset (using Fikse's offset convention.) I remember positive offset meaning a deep dish wheel, but I'm dating myself . So 20mm (4/5 inch) is not too much. The reason for this offset is to get as much tire inboard as possible. Some might say overkill here, since I had to run 8 inch coilovers to get it to fit. ------------------ Pete Paraska - 73 540Z - Marathon Z Project - pparaska@tidalwave.net">pparaska@tidalwave.net - Quote Link to comment Share on other sites More sharing options...
Danno74Z Posted May 3, 2000 Author Share Posted May 3, 2000 Thanks Pete, I was off just a little on the rim lip (15mm) to get to the 20mm offset. That is more like it. The 8" coil-over is the length of the spring you used - right? Danno Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 4, 2000 Share Posted May 4, 2000 Yes, an 8 inch free length rear spring, which force me to a 300 lb/in (I might be able to get away with 275 lb/in). The issue is that for that short of a spring, you only have so much room until you get to coil stackup. The static weight of the car uses some of that, and hitting dips, etc. uses more on top of that. The stiffer spring compresses less for the static and dip. If they're too soft, you get coil bind when you hit that dip, etc. But I've got a plan to be able to lengthen the spring. I've used the 240Z top strut isolator. I'm going to take some height out of it (I think you can take close to an inch out) by taking the shell off the rubber (heat slightly with a torch), cutting the rubber height down, reassemble, and peen the shell over the bottom part of the rubber to encase it. Maybe some rubber cement in there as well. I've heard this works well. I have an email in to Andy at Dandos to see if he knows of any progressive rate coil overs, and if they are available in 9" free length at the rates I'd want (probably around 200 lb/in.) ------------------ Pete Paraska - 73 540Z - Marathon Z Project - pparaska@tidalwave.net">pparaska@tidalwave.net - Quote Link to comment Share on other sites More sharing options...
Danno74Z Posted May 4, 2000 Author Share Posted May 4, 2000 Thanks guys for all the input on wheel and tire combinations. I feel this information could help a lot of builders so if there are others out there with information please feel free to chime in with data. Pete, you mentioned that your rear rims were "17x9s with 149mm backspacing". I'm trying to determine the offset of your wheels. I did some math, "scary" and this is what I came up with. 9inches = 229mm 229/2 = 114.5 per side of centerline of wheel (fudge factor for lip) 149-115 = 34 mm positive offset 34mm = 1.34 inches 34mm seems high for our type car. Did I make a mistake in calculating the offset. Thanks, Danno Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 4, 2000 Share Posted May 4, 2000 I've found that adding 1" overall to the wheel's "size" just about works perfectly. An 16x8 is 9" wide, and so on... Pete, if Andy comes up short, give me a call at work. I have an SSI catalog with a few different progressive coilovers spring, but I can't remember if there were any 9" free length ones... ------------------ Michael Sen-Roy Houston Performance 281-893-6080 ------------------ Quote Link to comment Share on other sites More sharing options...
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