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Rota RB/RB-R, 4x114.3, 17", Z-Offset Wheels

What would you prefer?  

188 members have voted

  1. 1. What would you prefer?

    • 17x9.5" -19 On all four corners (as the group buy has been)
    • 17x9" -13 Front and 17x9.5" -19 Rear even if it costs an extra $200 ($950 shipped)
    • 17x9" -13 Front and 17x9.5" -19 Rear at the same price ($750 shipped)

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I have been in contact with the Rota representative who is located about 30 minutes from my home. I inquired about having the Rota RB (it looks like a rewind/watanabe) made in a 17" by around 9-10 specification to our desired offset. A total of 25 people (100 wheels) would be required to run this deal. I think this one might be a long shot, but they are very attractive wheels and a 17X9.5 or so in a low negative offset might be just the ticket for our Z cars.


EDIT: Update - Pricing is $750 for a set of four shipped any where in the continental US. If you pickup in Hayward, it is only $700. These wheels will be setup to clear a stock suspension, but will most likely (almost 100%) require flares or fender rolling. I am working on determining the size that fits at the moment and will be making cardboard wheels in a 245/40, 255/40, and 275/40 size. The rears should fit 275/40 no problem. The fronts may need to step down to 255. We shall see. This will help me to determine an offset that works.


If you are interested and willing to jump on this, please express it. Suggestions on sizing are welcome as well. Images are in the link above.



1. Rudypoochris - Chris Moris - chrismoris@gmail.com

2. DSommer - David Sommer - dsommer479@yahoo.com

3. Sparkynacho - xxxxxx - sotoa01@yahoo.com

4. Rev240z - xxxxxx - bcproperties1@comcast.net

5. Panachedk - Adam O'Lena - amolena@uwm.edu

6. Streeteg - xxxxxx - Eguidice@hotmail.com

7. Dreco - xxxxxx - dreco@sbcglobal.net

8. Cowboy510- xxxxxx - coyboy510@hotmail.com

9. Cowboy510- xxxxxx - coyboy510@hotmail.com

10. DemonZ - xxxxxx - louho@hotmail.com

11. Shoryuuu - xxxxxx - shoryuuu@yahoo.com

12. Bjhines - xxxxxx - jwhines3@nc.rr.com

13. White_rice - xxxxxx - old_skool_rice@yahoo.com

14. Memc - xxxxxx - mfraserjr@gmail.com

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If I end up getting these wheels I will definately run flares on my car. If I stick with the 16X8 Rotas I have now, maybe, maybe not.


I used to think the same about 17"s on S30's. I think it looks fine now after seeing the cars with CCWs and other peoples builds. My main issue with 15" and 16" sizes is that there isn't really anything larger than 245 maybe 255, unless you go into Hoosiers and race tires. 17" you can go up to 285mm no problem with a wide selection.

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It is $750 free shipping in the USA for 4 in 17X9.5 -20 offset. What do you all think? We would need 25 people... thats alot.


EDIT: It doesn't have to be that size either, I just figure that is going to work out back. Does anyone know if that would be okay on the fronts with ZG's or is that really pushing it. I know the Wats are -13 16X9's, so these would stick out an extra half inch or so I would think.


These would be really serious wheels though. Ever see the lip on a 16x9.5 -19 watanabe... its fat. These would be a similar lip depth.



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Mustangs do have a 5 x 4.5 = (5X114.3) bolt pattern.


Also, Kim said the maximum size for a 17" wheel from them is 9.0-9.5. I think if we get enough people interested in a 17X9.5" wheel, we can get them to make them. To run these with ZG's I would think you'd have to be running coilovers for the added clearance to the strut. We should shoot for a backspacing around 5.0" backspacing. That equals a offset of about -6mm to -12mm should be about right..



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Just thought I would suggest the following.....I have been following this thread with some interest and I have noticed that there some predicting going on in regards to the wheel size and offset, I just thought I would suggest the following which should spark more interest in people actually purchasing. You could divide this into four categories which would make everyones order much less confusing to them and to the company making the wheels.


1. People running their Z with coilovers and with ZG flares - (specify the optimal wheel size, backspacing and offset for both front and back here)


2. People running their Z without coilovers and with ZG flares- (specify the optimal wheel size, backspacing and offset for both front and back here)


3. People running their Z with coilovers only and no flares - (specify the optimal wheel size, backspacing and offset for both front and back here)


4. People running a stock setup, some people like the look of the wide wheels but do not want to run flares. (specify the optimal wheel size, backspacing and offset for both front and back here)


Just thought I would add, that it is up to us as a group to figure out what is the best Wheel size, backspacing and offset for the wheels in each category, this is difficult for many people to calculate on their own.

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Okay. I agree on the offset comments above. I doubt these will fit without flares though so attention to all those planning on running stock. The wheels are probably just too large.


I have emailed Kim asking her to confirm that all we need is 25 sets of the same width and diameter. I also asked if I should compiled a list of people who are interested and their emails. Lastly I asked her to confirm a time estimate based off the knowledge that rota sometimes takes a while to deliver. She is the head of all north america for rota if I understand correctly and she has an office/warehouse 30 minutes from me. I might go meet her in person.


I figure we are going to need a list of people who are commiting anyways so please if you would like to get on this, just type your email and name and I will compile a master list edited into the very first post of this thread. DO NOT TYPE if you are un willing to commit. The price is $750 a set shipped to anywhere in the continental USA or $700 picked up in Hayward, CA.


Also, I did contact the 240sx forums and put a group buy post up, we shall see...

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The backspacing is going to be the same regardless of the width wheel you want to run. Opinions differ, but the general consensus seems to be that 5" backspacing works for those running coilovers. It would be less for those without coilovers, but personally I don't think it makes sense to run the width rims being discussed here without using coilovers.


Given the 5" backspacing you can calculate the offset needed based on the width wheel you want. Now there could be variances between manufacturers, and someone else posted problems installing their Rota's that seemed to be the correct offset.

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5" BS on a 9.5 inch wheel would be... 9.5+ 1" Lip = 10.5/2 = 5.25


Need -.25" = -6 offset


But is that too close for the front. Not talking strut to tire clearance. I mean tire to frame rail. My +10 16X8 grids touch with a 245 tire to the frame. Not badly, but enough to make it not clear. That would be the same back space. Could always use a bit of spacer, but it would be nice to make these fit right. Maybe rear and front offsets should be different while maintaining the same width? Watanabe 16X9 fronts use a 4.5" backspace same goes for the Wat rear. Maybe we should aim for that to be conservative? Something like -15 in the rear and -8 to -10 in the front using a spacer if needed.

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OK, I was asked to comment...


You are not going to get stock OEM type fitment from a wheel that's 3" larger OD and 4.5" wider then what the 240Z was designed for. You will have rubbing on the frame rails and TC rod in front at full lock. You will most likely have to trim the front edge of the parking light valance to clear at least the passenger side front wheel when turning left. Steering will be heavier.


Tire OD should be kept at 25" or less on the 240Z unless you plan on running bumpsteer spacers and/or relocate the front LCA inner mounting point. Even then, keeping tire OD below 25" is a good thing for these cars. Some sample tire sizes:




That's it in 17"...


For that size tire a 8.5" rim is fine and here's a picture of a 245/40-17 on a 8.5" rim:




A 5" backspace is typical for a coil over equipped 240Z. Spacers are sometimes used on the front for additional clearance and to get the front track wider then the rear for better handling.

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Offset doesn't matter, offset doesn't matter, offset doesn't matter.


What you need is 5" of backspace. Whatever offset that comes out to be, fine. If the wheel manufacturer needs an offset number to make the wheel, then either the manufacturer or you guys as part of the group by can do the math.


Offset is a by product of wheel rim width, wheel center thickness, mounting pad depth, and backspace. Since we as wheel buyers can really only specify wheel rim wdith and backspace, we get an offset number and have to work with it.


Wheel position can be adjusted using spacers. In the 4 sets of racing rims I've ordered for my own personal 240Zs I specify a 5.5" backspace and adjust clearance and fitment using wheel spacers.


You guys should also be concerned about caliper clearance and center hole ID.

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I'd would be much easier if evryone gave measurements the same way. Some wheels specify the offset and some the backspace.


From my experience the auto manufacturers are the ones that emphasize offset and the wheel manufacturers tend to focus on backspace. So when you read the wheel specs in a FSM or owners manual it talks about offset while the custom wheel spec sheets ask for backspace information.


And yes, the thickness of the wheel mounting flange and the wheel center does have an effect on offset, which the backspace number makes clear.

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Here's a link to a thread that discusses backspace and offset in detail including posts by people representing themselves as wheel designers.



There are many diagrams on the net depicting offset and backspacing, but the one included in the thread looks like a good one as it includes flange width. I guess in some cases the inner and outer flange widths can actually be different.


I just want to purchase rims that have the recommended 5" of backspace, when the only information I'm given is the offset. The Rota RB 17 x 8.5 wheels I ordered has an advertised offset of 4mm. Of course this information would also help determine the proper offset used to place an order for the 17 x 9.5 rims as well.

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I think I am just an unlucky group buy starter. :)


These wheels should really be flying out of here, but guess not. :P


Give it some time. A 73mm bore sounds more like it. I am talking to Kim I believe she told Justin any size and offset, but I want her/him to confirm that.


EDIT: Kim replied that any offset or bolt pattern is a go as long as there are 5 people (20 wheels) for that given offset or bolt pattern.

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Yes, but unfortunately the first group needs to be 25 people. LOL


I currently am making a 17" "wheel" out of cardboard with an adjustable measured offset. I will make 2 or 3 cardboard tires. Probably 3. A 245, 255, and 275mm tire set each with a "40" aspect to slip onto said mock wheel. This weekend I will fit them to my S30 with coilovers to find the optimal size. That way i can atleast get an idea. I will probably ship them to someone with ZG's currently installed for final measurements and backup gaurentee of fitment.

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I think the guys with wats run 245mm tires, not sure though. I went to my brothers today and put the mock up wheel on:


Image 1



Image 2



Image 3



Image 4



Image 5



Image 6



So I set the mock up wheels with one side a 275/40 sizing and the other a 245/40 sizing. I did not try the fit on the back. I started with a -6 offset testing the 245/40/17 combination, it did not clear the rails at full lock, there was interference at the fender as well.


Image 3 illustrates the contact with the frame rail and the coilover perch.


I then spaced out the wheel to a -19 offset. This looked the best and seemed to work pretty well. Using this offset I achieved 3/4" to 7/8" tire to rail clearance at full lock to the right (image 4). Also note in Image 4 that this setup yielded 5/8" to 3/4" of space between the wheel and the coilover perch. The coilover perch is ~3.5" OD, can anyone tell me the stock perch OD?


In Image 5 at full lock to the right again, one can see the tire did not clear the stock front valance. It interfered 1"-1/4 maximum (max interference appears to happen at full lock, I checked other angles). Can someone with ZG flares chime in about how much more space they add in that region. Does an airdamn remove that turn in on the lower valance entirely? I think this amount of interference is probably acceptable with a car setup on flares and possible air dam. Not sure though.


Image 6 shows full lock to the right, the clearance is approximately 1"-1/4 tire to rail. Nothing to worry about imho. There is no fender interference stock at the back. It is only at the front where the valence is located.


All of the testing was done at full droop. The car has bumpsteer spacers (don't think this matters). The alignment is setup by eye and ruler right now, it is straight enough to roll with no noticeable increase in resistance. The width of the cardboard to simulate the tire is the section width. The section being the widest part of the tire (the buldge) thus in reality there should be increased clearance as the outside of the tire is skinnier. I would think a 255/40 tire would work fine up front with this -19 setup provided the front valance to tire clearance is not a pinch point. The 275 tire won't fit with out major modification or pushing of the wheel out excessively far.


The -19 makes sense and I think the tolerances should clear stock springs. The watanabe 16x9 fronts use a -13 offset. Considering our wheels would be 1/2" = 12.7mm wider this works out. 12.7mm/2 (two sides of the wheel) + 13mm. That would make a -19.35 offset. 240hoke said there was plenty of room with his 16x9 -13 offset fronts on a ZG flared car, this 17x9.5 -19 offset should work.

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just to add.. i used to have a set of 17X8, with 5 inches of back spacing, and they just barely fit with the stock struts in the rear.. I ran a 235 tire, and rolled the fender a tad.. cannot go any bigger without flares or coilovers. 17's along, with more tire options will also be able to clear brake upgrades..


i'll find some more people

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17x9.5 won't work very well on a Z. save yourself some grief and get 16x8 with a 12 to 15mm offset... this should clear everything on a stock or lowered z. ZX's could probably use a 9.5, as they have more fenderwheel than a z.....


this is based on personal experience with 16x8 0 offset on a '72 240z. this setup has 3/4" clearance on rear coilovers and slightly more on front coilovers (hence the 12mm offset for stock Z). unfortunately, with 0-offset, tires will hit front wheel arch (unless you have an air-dam), rear tires will hit fender lip on a lowered Z (even if you rolled the lip). stock rear height will not hit if you run 26.1 trim height and 200 lb/in spring.


anyway, that's the truth..... spend your money however you see fit..... personally, i dig the Rota RB and would have bought a set had they been available in 16x8 +12ET....

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Guest coyboy510

I just came across this over the weekend and am very interested in a set for my Z. However, I have the same sentiments as someone in the thread about the size/offset combination discussed. It seems to still be unresolved?

The setup that I'd like would be for a Z running ZG Flares "without" coilovers. Im running Nissan comp springs with shortened strut assemblys. The offsets that I'd like someone to recommend would be the specs from the Watanabe site for ZG wheels (http://www.rs-watanabe.co.jp/matching/nissan.htm). I realize they aren't the same diameter, but can't we just use these values?

240ZG: (from the link above)


F: 15x8.5 -6 (offset)

R: 15x9.5 -19 (offset)


F: 16x8.5 -6 (offset)

R: R 16x9.0 -13 (offset)


Backspacing turns out to be: (determined by me...please double check math/conversion)

Width (in) Offset(mm) Backspacing (in)

8.5j -6(mm) 4.013779528(in)

9j -13(mm) 3.988188976(in)

9.5j -19(mm) 4.001968504(in)


Shouldn't we just keep consistent with what Watanabe did/does maintaining a 4" back spacing? Or at least for the folks that are wanting to run the ZG Flares.


How many folks are there now that want to buy?


Oh, I forgot to mention the the 17" or 16" diameter is fine with me.

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The 16x9.5 watanabes use a -19 offset. For our 17x9.5's, that is what I recommend after having made a mock up wheel, fitted it, and measured. I understand your worries though. There is no way to know until it is on. In any case, 4.5" backspacing (same as the wats) should clear a stock setup... earlier I asked for the stock perch OD (I have coil overs) if you have that dimension I will confirm it for you.


I know alot of people like to throw out numbers and imagine what it might be like based off of wheels that fit in approximately the same size. This is no good. As I posted earlier... the suggest 16x8 +12 which was supposed to be a safe size that would "same some grief" doesn't actually fit. I know because I OWN a set of 16x8 +10 and they already rub with a 245/50/16 tire. A +12 is only going to rub more.


The proposed wheels ARE going to require flares and possible snipping of the lower valance (shouldn't be an issue if your going air dam). Yes the offset will be greatly negative as well. This is not necessarily a wheel for the masses, but it is a great wheel that should provide killer looks and the ability to fit tires that other people just can't. I appreciate your size recommendations and information though. It is very helpful. After building a mock up and testing sizes I basically determined that the watanabe -19 is the way to go. Using a 17" rim we would have slightly more clearance as well since the struts point inwards. Just a thought.

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