Fitting zg flares on rear- determining flare height

[fusion]

I am in the early stages of fitting my rear ZG flares on my 280z. I have read through a lot of install threads, most of which have broken picture links. My understanding is the best way to decide how high up to mount the flares is to remove the spring from my BC racing coilover to allow the shock to compress all the way to the bump stop.  

 

However, when I did that, I can only compress the shock up so far until the rear wheel/tire (275-50-r15) runs into the factory wheel arch. There is still a ways to go before the bump stop bottoms out. But it's extremely hard to measure the distance remaining.  It's a chicken-and-egg scenario.  I can't determine where to make my cut line until I can compress the wheel/tire all the way, but I can't do that without cutting the metal first. 

I must be missing something, any thoughts?

[Patcon]

That is one of my objections to the flairs. Many times to run them you have to cut the wheel arches all up. Then try to weld them closed to keep water out of the car. That just doesn't seem like a good decision for a car that is likely to appreciate a lot in value in the next few years.

[HS30-H]

8 hours ago, fusion said:

I must be missing something, any thoughts?

The factory 'Overfenders' were shaped so that their attachment points were pretty much self-evident. The rears had a little kink in the mating face that matched up with the swage line in the factory metal. 

Generic copies-of-copies and their derivatives may not have such subtleties.

[fusion]

I am using Marugen Shokai over fenders.  They seem to have a bit of range of where they can be mounted.

[HS30-H]

6 minutes ago, fusion said:

I am using Marugen Shokai over fenders.  They seem to have a bit of range of where they can be mounted.

They are probably the most accurate reproductions on the market, so they *should* find their own mounting positions when you get the ends close to where they need to be. The main pitfall is mounting them on the wrong side of the car (seen a few cars like that...) but if you have the correct piece on the correct side of the car it shouldn't be too difficult to get them within a few mm of spot-on.

How's the sheetmetal on the car? No bondo/filler? Paint thickness? 

[fusion]

Car was media blasted to bare metal and sprayed with epoxy primer.  Metal looks good.

[mailnome]

If this is what you are doing, you just do the same that you have done if you have already determined your ride height.

You don’t have to cut the whole thing out at once and may only want to remove as little as possible to get enough clearance for the tire.

Do it a little at time. Jack up the tire till it hits. Look straight up at it and mark and trim some off, repeat till satisfied or sick feeling in stomach takes over.

If you have a lot of tire hanging out then you could put the flare up and mark a “cut no higher than line” then cut an arch out. I would also work my way out to that line too just to be careful.

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[HS30-H]

7 hours ago, fusion said:

Car was media blasted to bare metal and sprayed with epoxy primer.  Metal looks good.

So you should have the swage line to work to, and the Overfender will pretty much find its own position once you find the reference points.

Two of the fixing points (Nissan riveted the Overfenders onto the body, but you might want to use another fixing method) are almost ON the swage line, or are just below it. The Overfender overlaps the swage line at the uppermost peak of its curve. At the ends of the Overfender, the forward-facing end positions just above the dogleg and the rear-facing end drops down way below the bumper.

Hopefully this photo will help. It is a genuine HS30-H model Fairlady 240ZG and the mounting position is the factory one. The owner chose to insert some black welting between the Overfender and the body - which the factory never did - but hopefully you can still clearly see the body swage line as it runs along the body, the overlap of the Overfender and the two uppermost fixing points which are your reference for the height of the Overfender on the body: 

 

[HS30-H]

Once you've got the Overfenders mounted in the correct positions, THEN you can see how much it allows you to cut and clearance the rear arch sheetmetal. You can get very close to the Overfender mounting points, and this allows you more clearance than you are ever likely to need. Once you are cutting you might as well go all the way.

To sum up, the correct Overfender position dictates where you cut, not the other way around.

[HS30-H]

Here's what NOT to do. This car belongs to well-known "Serious Collector" and Bring-A-Trailer star 'Lstepp4re'. The Overfender is mounted too low on the body, and is also 'clocked'. All sorts of wrong:

 

[fusion]

Thank you for your help!