Newoldschool Posted October 5, 2014 Share Posted October 5, 2014 (edited) Hey all, I've been doing a lot of research, combing through a lot of threads trying to find the right answer for my wheel/tire question. Right now my 240Z has unknown 15x7 rims, unknown offset. When I got the car it had 225's and would rub at full wheel lock, and scrub in the back over bumps (I suspect a wrong offset for the wheels). I went down to 205's, but it's such a tiny tire... the Z is my dedicated racecar, currently autocross but will be taking it to Leguna Seca track days. It just needs more meat. Ideally I'd run 245's. Doesn't look like there is much in the 15" range, so the "smallest" 245 tire I can reasonably find is a 245/45/16 (likely to be some sort of Proxy). Doesn't have to be a "street legal" tire as long as it could pass at a glance- again, it's my racing car, but I like to take it out for the occasional joyride too. Unlikely to ever be driven in the rain. Coilovers seem inevitable, and I'm also going to get a quality job for the inner lip getting rolled. I don't want to go with flared fenders though. I'd like to hear if anyone is running 245's with a similar setup, and if so, what offset (I keep hearing that 0 offest is the magic figure for Z's) and backspacing you are using? Also, 8" or 9" wide rims? I think my ideal setup would be a 16x9 with the 245/45/16. Willing to go up to 17 as well (many more 245's available in that size as well... 245/40/17 would be y choice then). I want to do a squared setup so I can rotate mid-season. Thanks for the help! Edited October 5, 2014 by Newoldschool Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 5, 2014 Share Posted October 5, 2014 I ran coilovers and 15x8s with 250s (weird sizing on Yokohama slick). I don't recall the backspace, I think it was 5", and I didn't roll the rear fenders. There was easily room for a 15x9 with those tires, possibly without even rolling the fenders. A lot of the hipo 225 15" tires are REALLY wide to be called a 225, and they actually fit better and give faster lap times on a 15x9. Look at Miata forums. Very popular size for them. Quote Link to comment Share on other sites More sharing options...
socorob Posted October 5, 2014 Share Posted October 5, 2014 http://forums.hybridz.org/topic/114638-1978-280z-gto-ls1-t56-ttt/page-8 Post 141 shows my new 245 rivals I just put on. These are on 17" G35 wheels, i believe from 03-04. The rivals are over an inch wider than the 245 sumitomos they replaced. This is with full TTT coilovers using 5 lug Q45 hubs in the back and 86 Z31 hubs in the front. with a wheel with maybe 1/4 or 1/2 inch less backspace 255s would probably fit. Quote Link to comment Share on other sites More sharing options...
thedarkie Posted October 5, 2014 Share Posted October 5, 2014 (edited) I don't know how those hubs contribute to the overall scope of this discussion ^^^ so it probably doesn't do him much good with an unknown offset and backspace. I'd love to get 245's on the back of my car without even rolling the lips, just with coilovers. I suspect it's very possible, just gotta do the math on wheel offset/backspace properly. Edited October 5, 2014 by thedarkie Quote Link to comment Share on other sites More sharing options...
ktm Posted October 5, 2014 Share Posted October 5, 2014 (edited) 245/50 R16 on 16x8 +10 wheels, Tokico HP Blues and cut 280z springs. No reason for coil overs to fit 245s. Edited October 5, 2014 by ktm Quote Link to comment Share on other sites More sharing options...
thedarkie Posted October 5, 2014 Share Posted October 5, 2014 ktm any shots directly from behind? the fitment looks great.. no rubbing up front? Quote Link to comment Share on other sites More sharing options...
ktm Posted October 6, 2014 Share Posted October 6, 2014 (edited) There was rubbing galore, but you will get rubbing with 225's on the stock lower valence. If you run an air dam then that helps with some of the rubbing issues up front. I, however, am using the stock valence along with a Bre spook. I had to trim the lower valences a bit for clearance, but it does not look bad at all. I have a 10mm spacer up front as well to help with brake clearance; I am not using a spacer in the rear. I barely rimmed the spring perch in the rear as well to give myself a little more clearance. I had to roll the fender ips on all four corners otherwise I would get serious rubbing if I went over the slightest bump. Now, I only get the occasional chirp from the passenger rear tire if I hit a severe road dip/transition on the highway and really compress the suspension. Otherwise, no rubbing. Edited October 6, 2014 by ktm Quote Link to comment Share on other sites More sharing options...
jt1 Posted October 6, 2014 Share Posted October 6, 2014 It depends on your ride height and camber. On my white track car, I used to run 245/45/16 on 16x8 rims, with 5" backspace and coilovers. Hoosiers would touch slightly on the rear, V700's wouldn't touch at all. 5" front 5.5" rear to the flats, 2.5 deg camber. Wheel width was inside to inside. jt Quote Link to comment Share on other sites More sharing options...
thedarkie Posted October 6, 2014 Share Posted October 6, 2014 Thanks for the info. I wonder how going to a 245/45 instead of the tall 50 would change that behaviour. I have a 260Z with no front valance.. I just checked my 205/50/16 on the rear and I easily have another 1.5" of space before I hit suspension, and the wheels are 4" backspace. I think a 245/45/16 on an 8.5" wheel would work in the back. There was rubbing galore, but you will get rubbing with 225's on the stock lower valence. If you run an air dam then that helps with some of the rubbing issues up front. I, however, am using the stock valence along with a Bre spook. I had to trim the lower valences a bit for clearance, but it does not look bad at all. I have a 10mm spacer up front as well to help with brake clearance; I am not using a spacer in the rear. I barely rimmed the spring perch in the rear as well to give myself a little more clearance. I had to roll the fender ips on all four corners otherwise I would get serious rubbing if I went over the slightest bump. Now, I only get the occasional chirp from the passenger rear tire if I hit a severe road dip/transition on the highway and really compress the suspension. Otherwise, no rubbing. Quote Link to comment Share on other sites More sharing options...
Mike Mileski Posted October 6, 2014 Share Posted October 6, 2014 (edited) I have 245/40X17s on the front of my car and 265/40X17s on the rear with stock fender wells and no rubbing. I have coil overs, Z31 front hubs and a TTT rear setup. I didn't need to roll my fender lips either. Mike Mileski Tucson, AZ Edited October 6, 2014 by Mike Mileski 1 Quote Link to comment Share on other sites More sharing options...
thedarkie Posted October 6, 2014 Share Posted October 6, 2014 Yeesh every time I think I've figured out the largest size, someone one-ups it... 265 under stock fenders. Damn. What specifically do you have on the rear and how is it different, dimensionally, than the stock setup? Whats the backspace and offset on your wheels? I'm impressed that you got that much tire under there... now I need to know if I can get away with a 265 with just coilovers on stock hubs and fenders. Quote Link to comment Share on other sites More sharing options...
Phantom Posted October 6, 2014 Share Posted October 6, 2014 Mike, Evidently you have the near perfect wheel width and offset. Are you running the same widths in the front as the rear? My son is running 8.5" wide wheels in the front with 245's and 9.5" wheels in the rear with 275's - but he has flared fenders. So what are your wheel widths and backspacing/offset? - whichever way you want to state it. Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted October 6, 2014 Share Posted October 6, 2014 Those don't look like 265s, but it's hard to tell. Quote Link to comment Share on other sites More sharing options...
socorob Posted October 6, 2014 Share Posted October 6, 2014 Also what brand tires. Sumitomos 245s are 1.25" narrower than bf goodrich rival 245s. I know its "supposed " to all be 245mm wide, but apparently it ain't so. Quote Link to comment Share on other sites More sharing options...
Leon Posted October 7, 2014 Share Posted October 7, 2014 Also what brand tires. Sumitomos 245s are 1.25" narrower than bf goodrich rival 245s. I know its "supposed " to all be 245mm wide, but apparently it ain't so. Exactly. Tirerack is a good source to compare different tires of the same size. They publish actual section and tread widths. Quote Link to comment Share on other sites More sharing options...
madkaw Posted October 7, 2014 Share Posted October 7, 2014 (edited) I get slight rub with 245/45/17's on my 240 with lowering springs and NO coilovers. This is a +4 offset. Like KTM-I believe the +10 offset is the key for maximizing under stock fender. You will have to use a spacer up front. My fronts clear now that I beat in the spring perch a tad. Very rarey the front touches the air dam when reversing in a tight turn and hitting a bump. I'm going with 225's since I messed up with the offset. I think 235's would clear with the +4 offset. Tires are General Ultima XP 17X8.5 rims +4 offset Edited October 7, 2014 by madkaw Quote Link to comment Share on other sites More sharing options...
ktm Posted October 7, 2014 Share Posted October 7, 2014 Clifton ran 275s on his car nonflared. He was also using coil overs in order to achieve it though. 245s are about the widest you can go without coil overs due to the diameter of the spring and perch. Coil overs are smaller in diameter and will allow you to go wider with the right offset. Quote Link to comment Share on other sites More sharing options...
thedarkie Posted October 8, 2014 Share Posted October 8, 2014 (edited) ktm I think you have me sold on the 245s, I just think I'd prefer a 245/45... the 50 seems kinda tall. If Im buying new wheels though I might just go staggered with a 225 up front to avoid rubbing. Edited October 8, 2014 by thedarkie Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted October 8, 2014 Share Posted October 8, 2014 225/50/15 all four with zero offset 15x7 and you avoid a lot of hassle and spend more time on the track. How much faster do you really think the larger tire will make you vs the hassle? Quote Link to comment Share on other sites More sharing options...
Newoldschool Posted October 9, 2014 Author Share Posted October 9, 2014 I have 245/40X17s on the front of my car and 265/40X17s on the rear with stock fender wells and no rubbing. I have coil overs, Z31 front hubs and a TTT rear setup. I didn't need to roll my fender lips either. Mike Mileski Tucson, AZ Mike- wht offset and backspacing? I want to go squared up on the tires- 245's all around is good for me. I'd rather have all 4 wheels be the same than try to squeeze out a little extra beef in the back. likely going to go with 16x8's, but i've heard 16x9 with 0 offset and proper backspacing works too. Would really like to avoid spacers if I could. Quote Link to comment Share on other sites More sharing options...
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