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Wheel fitment issue with Modern Motorsport rear disc conversion?


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So I just finished a rear disc conversion using the Modern Motorsports kit and now my OEM (1973) 14" wheels won't fit (they rub the calipers)... I searched Modern Motorsports' website and see no mention of requiring larger rear wheels, but see on page 12 of the upgrade options sticky discusses 14" wheels not fitting... oh well, I guess, but does anybody know the minimum offset and diameter that I need to be able to put wheels on this car?

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:hs: The rear disc system will put you into the 15" or bigger rim sizes. I did the 280ZX rear disc brakes and started with 15"x7" zero offset rims. Right now I am running 16"x7" rims with front wheel drive offset w/1" spacers, with 225/50/16 tires. 14" rims will not work, sorry. You can use the zero offset as the starting point. But you can run other settings if you use a wheel spacer.:burnout: Edited by RedNeckZ
offset needed
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Thanks. To be safe, I was looking at a set of 16's in Cali, but the guy won't ship so I'm trying to find someone in Cali who can pick them up and ship them to me. If that doesn't work out, I'll just find the cheapest 15"+ wheels possible until I can afford some nice wheels.

 

Shitty that their website doesn't specify the need for larger diameter wheels, though... you'd think that's kind of important.

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:hs: The rear disc system will put you into the 15" or bigger rim sizes. I did the 280ZX rear disc brakes and started with 15"x7" zero offset rims. Right now I am running 16"x7" rims with front wheel drive offset w/1" spacers, with 225/50/16 tires. 14" rims will not work, sorry. You can use the zero offset as the starting point. But you can run other settings if you use a wheel spacer.:burnout:

Just to clarify, 280ZX rear disks DO fit under 14s. The Modern Motorsport setup uses 300ZX disks which are larger diameter and it's possible that they don't, I don't know because i haven't tried them. The early 280ZX rear disk actually fits under 13s, a friend of mine ran them on the back of his 510. I would assume the later 280ZX is the same but have no personal experience there.

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:flamedevi I have the early 280ZX calibers with the later (thin hat) rotors with the flat plate mount. I could not fit my 14"x7" western minilight look-a-like wheels over the brakes and had to go to 15" wheels. I was using the plans that I got from the Texas club ex-president (got it during the Colorado Z world meeting in the 90's). Don't know about it working any other way, sorry.
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:flamedevi I have the early 280ZX calibers with the later (thin hat) rotors with the flat plate mount. I could not fit my 14"x7" western minilight look-a-like wheels over the brakes and had to go to 15" wheels. I was using the plans that I got from the Texas club ex-president (got it during the Colorado Z world meeting in the 90's). Don't know about it working any other way, sorry.

Must have been an offset problem caused by using the thin hat rotor with the caliper designed for a thick hat. This would push the caliper about an inch outboard. If you consider the diameter of the rotor is 10.15" (just looked it up online), then logically you'd have a lot of room inside a 14" rim. My friend ran his with 14" 6 spoke ZX wheels, 13 x 7 Panasports, and 13 x 7 steel circle track rims. No problems on any of them, but he was using the deep hat rotor and the early caliper, so that moves the caliper inboard. I expect the same with yours if you add a wheel spacer or got a spoke design the similar to your 15's.

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I think most of the fit issues, are not about the diameter of the rotor+the caliper fitting inside the wheel, but more often, about the "inboard and outboard" positioning of the caliper. I had something similar happen to me with my front brake upgrade. I had 16X7 Epsilon mesh wheels on the front of my Z with 300zx vented rotors and S12W calipers, and I required a small spacer on the hub to push out the wheel away from the outside face of the caliper. The back side of the rim was nearly flat. What I mean is the mounting surface was the same backspace as the mesh part of the rim. Not sure if I illustrated that very well, but without the slim spacer, I could not bolt the rim up flush. It contacted the caliper before it would sit flush on the rotor hat.

 

Try a small test to see if the wheel is contacting the caliper face before the wheel sits on the rotor hat, or if it is an overall diameter issue. Its worth the check before you write the cheque.

 

Scott.

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I did the Modern Motorsports rear disc conversion and the stock 14's wouldn't fit anymore, just like you found. I ended up going with a set of turbo Swastikas 15 x 6 which work just fine. I actually have a second set of these for sale. They look better than the ones on my car, but two of the rims are bent. You could have them straightened and you'd be in business. I will ship them too. I'm in Oregon. If you're interested, then PM me.

 

Greg

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