Careful if putting 599 rims on 612!

Hey guys. Many of you have probably been following at some point my 612 re-build. I thought I'd go out on a limb and post this wheel specific update in a new thread.

I put 599 rims on my 612. So the wider rears, not the 599 style version made for the 612.

I have put 4,500 miles on the car with no real problem but just noticed the following with the car up on the lift. When the wheels are hanging, they rub on the inside. Check out the pictures.

I think they clear fine while on the road but going airborne could cause issues! I am thinking about trying a set of 1/2" spacers that I have for my Maserati QP (yes, with longer lugs too) to resolve but then I am concerned about any potential rubbing issues on the outside at the wheel well.

Has anyone else borne witness to this issue and have a perspective? Perhaps these wider rears are cutting it too close?!
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According to specs(If you compare PZero 612 and PZero 599 20" OE rear tyres, on OE 612 and 599 rims), you have increased the rear section width from 11.7" to 12.3". On top of that, the ET of the 599 rims are 63.8mm compared to 51.1mm of the 612 rims. This all adds up so that a 20mm spacer will put the inside wall of an OE PZero 305/35R20 599 tyre mounted on an 11" wide 599 rim in the same position as an OE PZero 285/35R20 612 tyre mounted on an 10" wide 612 rim. Next step is to see how much room you have on the outside for a spacer.

 

... and what is the best way to do that? Just throw a body or two in the trunk and eye-ball the spacing?

 

12.7mm of additional offset translates to exactly half an inch-- which would allow the one inch wider 599 rims to go on while retaining the same center, and allowing an extra half inch in either direction

Given that actual tire sizing for any given tire can vary among mfgrs, i find it surprising that half an inch under the fenders and translate to rubbing.

To further this point, 20mm wider tires at 10mm on each side of the center, is even less than a half inch on either side of the tire.

I'm not saying yours don't rub, I'm just surpassed! and wondering if anyone else can verify this on their cars as well because this subject has been discussed often on various threads here for years now.

I have both sets in my garage and I was just going to put the 599 set on the back of my 612 despite the mild difference is overall diameter...

 

Looking at the op's picture, MPSS do not come in the 305/35r20 but only in a 315/35r20. This will also make it wider than the stock 599 configuration. Just something else to consider. Maybe put Pirelli stock size on and it might help.

 

Yes on those sizes. And I bought exactly what the forum told me to buy!!!

So, should I use my 1/2" spacers and see how those work out?

 

Turns out my spacers are 15mm on my Mas. What do you think about that as an extension amount??

 

I think if you are going airborne in your 612, you have more than just rubbing issues!

 

check my old treads, i put on all rims and all tires with all spacers on my 612 with no issues on the rear, now on the front u wanna stay below 265/35/20s, all ferrari rims clear.

 

If you pull a spring out you can run through full suspension travel and see what you need. The rub does not look bad. Maybe instead of 1/2" an 1/8 or a 1/4 might do.

 

The offset is definitely the issue- I had 255 & 325 Michelins on 12" rims on my last 612 with no issues whatsoever

You can fit even more than that back there if you like, there's lots of room, you just have to watch the offsets
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Moe, your 612 is gorgeous !!!

Daniel

 

I have had no issues with the 599 size rims on my 612, running MPSS tires. And I have the stock suspension tightened.

 

OK, so perhaps, yes. But please jack you car up in a rear corner and let me know if you are contacting the wheel well carpet like my 2006 612.

Thanks.

 

No. If you keep the offset the same, the center of the rim and tyre will be the same no matter the width. The offset is measured from the center of the rim. What that half inch offset of difference between the 612 10" wide rim and 599 11" wide rim has done, is to basically keep the outside of the 599 rim flange at the same distance from the hub as the 612 rims, while moving the center of the rim and tyre 12,7mm inwards. However, the inside of the rim flange, now sit one whole inch further in. Those 15mm spacers will put the rim only 2 mm off center towards the outside and obviously make more room on the inside. Seems like the perfect size spacer to me if the tyre clears. How the suspension is loaded, is also affected by the offset. Decreasing and increasing the offset, moves the leverage point on the arm, and also load the hub bearing less or more depending on which way you go.

 

Very helpful! I am going to pull my Maserati spacers and lugs and mount them up for a try! Will report back...

 

OK, so I did the spacer work and analysis today. Pulled the 15mm wide spacers off my Maserati QP. I then installed them on my 612 (with the longer lugs).

Here are the pics. Bottom line is, spacers are absolutely needed. After putting in the 15mm spacers, I only had about 1/2" (13mm) of clearance when car in the air on lift. So about -2mm without the spacers. With lots of weight in the truck, the clearance seems like it will be fine in the outside of the wheel well. I won't know until I drive it and see.

The last two pictures so the stance without and then with the spacers. What are your thoughts?? Left wheel is no spacers, right wheel has the spacer. I took the pictures at 100% perpendicular as possible to the surface of the wheel.

I bought this spacer kit a few years ago from Formula Dynamics of Las Vegas. They do great Maserati and Ferrari mods. They are the gurus of Maserati mods for certain.
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Looks pretty good. Even if you install e.g, Hill engineering 11mm spacers, it looks like it will also leave enough room in case you feel like giving the MPSS F12 255/35R20 K2 and 315/35R20 K2 tyres a try, as they'll need an additional 4 mm on each side compared to PZero 305/35R20. How much does the arches stick out over the tyre wall at the tyres 10 and 2 o'clock position, measured from that point of the tyre straight up to the arch? I.e, in a straight vertical line from the ground, past the 10 or 2 o'clock point of the tyre and to the arch, if that makes any sense. It's not measured radially from the 10 and 2 o'clock positions on the tyre.

 

I do have the 315 MPSS tires on the rear. So with about 13mm of clearance and a 15 mm spacer, I wouldn't need spacers if I had run the 305 width, correct? So, I could go with a thinner spacer it seems...

For the measurement you are asking for, you want me to measure to the inside or outside of the arch? I assume inside, right? And where to on the tire? The max outer edge of the tire or the outer edge of the tread (which in inboard of the outer edge of the tire of course).

 

I just went and ordered the Hill Engineering 11mm spacers and lugs. That should be my best option here. I encourage anyone else running the 599 11" rims on the rear of their 612 to do the same.

 

Ah. I was under the impression that you ran the Pirelli's in 305. In that case you could basically go as low as a 5mm spacer(if anyone made such a thing for the 612). But yes, the 11mm would be my choice too. Tucking the wheels a bit more, will protect the car better from stone chips coming from the tyres.

Yes, the max outer edge of the tyre, and yes, the inside of the arch.

 

Now we know the reason for fitting stock 612 rear tires on the 599 wheels.

 

Taz - nice to see you posting here again.

 

Adam- Thanks.

 

I am starting to think that the 315's are definitely NOT the way to go if you want to put the 599 rims on the back of the 612. So, if you want MPSS tires, stick to the 10" 612 version of the Challenge wheels. Otherwise, if you have 599 rims on it, get the Pirelli 305's. and you will still be awfully close but OK. I believe I was ill-advised by this beloved forum into the 315's. Now, with that option, you need 11mm spacers (at $300) and your car will suffer from potential wheel-well rash (to be confirmed) and more road rash to the paint.

That's my summary so far.