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Hi David, the wheels in the pictures are both sizes.  You are correct that the fronts are 17’s and the backs are 18’s.  

Another member wanted some info so I thought I would post some close up shots of the wheels.

I believe that the centers are different sizes but am not totally  sure.  I can’t check right now as the car had a few minor issues so it is at my friends shop.

I also want to say many thanks for the help in answering some of my questions along the way.  It was greatly appreciated.  Thanks again David.



If you figure out a source for a nice looking set of FR500 style (or anything else) that fit a narrowbody car, looks cool, that you can get modern, performance tires for, and doesn't cost over 6-7K for the set, please post up the vendor, wheel specs, and estimated price!

I'm sure a lot of people would appreciate it!




I now beleive the 285/50R15 P7 has actually been produced. I also beleive they are currently in a lorry on their way to Longstone Tyres! which is great news.

They will be on here soon

Of course i will post on here again when they get here. How exciting, but blimey iot has taken some time, but the Pandemic has cost us an extra 2 years, and i do have other projects in with Pirelli that have just been put on the back burner so it will be great to get these.

i am relatively confident i will be able to keep the price sensible.

Going to run 335/35/17 MICHELIN - possibly on a 13.0 or 13.5 rear and 255/40/17 MICHELIN - possibly on a 10.0 or 10.5 on a factory GT5 with all the GT5 plastic removed and rivet on GT4 flares.  Not sure what rims yet - - but looking to possibly use centre lock BBS.   Rear tyres took some finding - fronts are a 2 -3 month wait.

You need a 13.0 - 14.0 inch wide rim to fill original fiberglass GP IV flares depending on the backspacing you select.  The 335 17 is narrow in width compared to the 345/35/15 I run.  Measure multiple times and cut once to get the right look.   I have seen 335 tires on too narrow a rim with literally no back space attempting to fill the flare.  Remember the factory GP IV cars use a 14” rim.  

@lf-tp2511 posted:

According to the literature I found 13 inches would be the widest recommended rim, very common width for the 335 is an 11 inch width.


Larry, an 11" rim isn't ideal for a 335 width tire; however, it is acceptable. Increasing the width of a 2 piece wheel to 11.5", 12" or wider costs considerably more than an 11" wide wheel. That's because the company that supplies rims to Wilkinson, Coddington, American Republic, etc., make an 11" rim but nothing wider. If you want a wider rim, it involves cutting 2 rims in half and welding them back together, to give the width and offset you want.

Thanks all for the suggestions.  11.0" is way too narrow for my purpose, pulls the sidewalls in too much and seems to be often used as a sort of a 'cheat' (for want of a better term) on a narrow bodied car (on my narrow GTS - I am sticking with 15" - PIRELLI CINTURATO) - this is not a narrow body, currently a factory GT5 - going to GT4.  Yes - the car currently has 345/35/15 as per factory GT5 (I wish someone made a 345 in suitable 17"), but I want to get away from the 15.0".  I have seen a 335/35/17 on a 14.0" - but in my opinion, too much of the rim was hanging outside the sidewall.  When I physically have the 335/35/17 in my hands (after the holiday break) - I will be experimenting, and expect at 'worst' - the rim will need to be 13.0" - at 'best' - I am expecting 13.5" - yes slightly narrower than what I 'dream' of - as being able to run a 14.0" - but the 14.0" seems just a tad too wide for the 335 carcass.  HA - by "...measure multiple times..." - I assume you mean -'measure ONE THOUSAND TIMES BEFORE CUTTING' - HA - for whatever cutting is required - I will be measuring multiple multiple times - leaving it - coming back the next day - measuring multiple multiple times again - and then doing what is required.  My biggest 'headache' - is figuring out a safe way to remove the factory bonded GT5 flares without causing any damage - they are genuine factory plastic parts and I prefer no remove them undamaged.  I also intend to run the car as low as I can - that may also cause me a few headaches - and is one reason that I may go from a 255/40/17 on the front to a 245/40/17 - but only time will tell.  HA - I have seen a 335 on 15.0" rim - but way too much stretch and only suitable for fad type events.  The BBS rims will be multiple piece, and hence  I can juggle the width of the hoops to create either the 13.0" or 13.5" (HA - and dream of a 14.0") - HA - following the old saying - "it is only money".

Firstly, why oh why convert a 9000 series GT5 to a Group 4! The factory GT5 is a rare car, likely as few made as GT5-S!

I run aftermarket 17" rims on my factory GT5, apart from the diameter they follow the specs of the GT5/5S 10 spoke Campi's for width and backspacing with 13" rears and 10" up front. Tires are Michelin Pilot Sports 335/35 rear and 275/40 up front. IMO they work great, fill the flares as they should. They are higher profile than OEM tires, so cause the car to sit higher, I have the suspension set as low as I can go and as a result have some cracking on the front flares from tire rub.



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"Firstly, why oh why convert a 9000 series GT5 to a Group 4! The factory GT5 is a rare car, likely as few made as GT5-S!" -- Firstly - I do not care what you think of what I do my my cars - HA - my car - my money  - my choice.  I am also getting rid of the hideous Italian lounge chairs - AKA - the bucket seats - pulling the factory 351 and installing an all aluminium 434 CLEVELAND (when the DAMN block becomes available) with 8-stack EFI and HALTECH engine management - and I could not care if it was the most rare PANTERA on earth, I do not 'collect' cars for investment - I 'collect' and build to want I want - not to satisfy some 'collector//investor' mindset.  I have never liked the GT5 all that much from all angles - hence back to GT4 - which in my opinion is a more clean wide look.  And understand re the 275 being a bit too tall on the front - hopefully either the 255/40/17 or 245/40/17 solves my problem.

Yes – advice re tyre height is well accepted – unfortunately – if one decides to play around with larger diameter rims – DAMN tyre sizing can then quickly ‘ruin your day’ - HA.  I hope to end up with the sizes listed for the MICHELIN 335/35/17 @ 26.0” rear overall height – and MICHELIN 255/40/17 @ 25.0” front overall height (not sure if I can get a matching 245/40/17 – otherwise I would test fit a set of those to the front) and I will be running 4.62 gears.

Re anyone modifying their car – I often cringe at the wheels and spoilers and other ‘bling’ that many people install on their car – but – it is their car, they can cover it in pink shag pile carpet for all I care – HA. And I believe we are members of the ‘PANTERA CLUB’ (for want of a better term) where we do not have a ‘spasm’ like the FERRARI club seems to have if a line up of absolutely identical red cars has a different valve cap – HA.  PANTERA like LAMBORGHINI (HA – yes – I modified that a well) are what I call exotic hotrods and you do what you want – it is your car and you can do what you want without other people having a ‘spasm’ over changes.

HA – I missed out on an F40 some years ago – and yes – I was going to modify that too – HA – no doubt I would not be typing this now as some lunatic from the FERRARI club would have had me shot – HA.

The GTS of one of my sons, it looks dead stock outside with CINTURATO 225/50/15 and 285/50/15 and mostly stock interior – the only major changes are the mechanical specifications – engine mainly.  HA – one change I do to all our vehicles – pull the stupid radio//tape//CD players out.  The exhaust is the ONLY music required in these cars for me – HA.

Rethe horrible Italian lounge chairs (AKA – the bucket seats) and all the other parts I will be removing from my cars – all factory parts will be carefully wrapped and stored for the day I die and then my boys can either decide to drive my cars as I left them, or they can return to factory specifications.  Same as the matching engines, the factory engines will all be properly put into long term storage, and one day if they decide 750.0 hp is too much, they can always install the somewhat slower factory engines – HA.

Whether someone decides to turn their L into a GT5 clone, or turn a GT5 into an L clone – that is their choice.  Such is life.

Re my GT5 to GT4 – I see my biggest headache (other than making sure I do not damage the factory parts when removing them) – is making sure that the GT4 flares are an accurate fit (as one can get) and modern quality construction.  Everyone says “my flares are perfect’ – but that is often with a hand over one eye and the other eye closed – HA.

I hope to find a red Si to purchase – and I intend to change the factory 17.0” rims out to 18.0” rims on that.  My ‘theory’ at this stage - is to have the factory Si rims copied in 18.0” – exact same offset – same color finish.  The rather low-performance 302 cu in will be replaced with a 427 cu in.


I'd only be guessing, because you have GTS fender flares and I'm really only familiar with the dimensions that work on a stock bodied Pantera. Dennis Quella told me, with aftermarket GTS flares, you can add about 1-3/8" to the outer dimension. Another vendor with GTS flare expertise is Ron McCall. I have photos (below) of a GTS bodied Pantera he built and the dish on the rear wheels was HUGE! I'd send him a PM. Looks like you have the same wheels. Perhaps yours could be "re-rimmed". Also, why only 8" and 12" wide? You could go an inch wider, front and back, without difficulty. What tire sizes will you be using?



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Last edited by davidnunn

Hello everyone.  I am sure that I am not the only one that goes through 'wheel and tyre dimension anxiety' each time they are putting a new project together, but in an effort to hopefully ease my 'wheel and tyre dimension anxiety' a bit (HA - hopefully), I am ordering a tool that I have found online that can be used to calculate offset and also check tyre clearance.  I have no personal experience with using such a tool, but as soon as I figure out how to use it (HA - my 'weakness' is never reading instructions properly), I will post my experience with it.  There are multiple manufacturers of such devices, but until I receive mine and gain some experience with it, I prefer not mention the brand I am going to use.  I do not expect any 'surprises' with it as all the different brands seem to do the same thing, and all seem to do it successfully.  CHEERS from AUSTRALIA.

@MikeSchill posted:

Hi all. New to the Pantera world. Looking to have custom wheels made for my 74 that has gts style fairings on it. I’ve read all 4 pages of info and feel dumber than when I started! Lol. The wheels would be 18x8 and 18x12. I need help with backspacing. Want the deep recessed look in the rear. 0DA0C0A2-6CFC-44ED-9C50-31912EB79720781EC0FE-235E-4306-9777-EAC7DD27E352

Your car has a great stance and those wheels are really nice. What size are they?  

These are made by SIMMONS in AUSTRALIA ( - this is a 17" version.  They make them in a range of diameter, width and colors.  SIMMONS has been around for many decades and make quality products. I purchased my first set of SIMMONS near on 35-years ago, and they are still going strong on the car I sold.   They also have other designs.


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So I finally had time to pull the wheels and do some measurements. Current setup is 17x9 with 6” backspace (+1” offset)

17x11 with 6” backspace (-1/2” offset).  I’m thinking of upping the to 18x9 and keeping same dimensions due to the 245/35-18 being a little wider tire. The existing setup is pretty close to full turn fender rub about 1/2”    The rears 18x12 with 6” backspace would push the tire closer to flush of fender lip. Can’t really go wider or pull wheel in more because it’s already close to exhaust pipe and 335/30-18 should work. The car has adjustable coil overs on all corners and wilwood disk brake conversion all around.
Do my calculations look correct?

To be clear with builder 62 mm bore and 5x4.50 bolt pattern?


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