It’s All About (Tyre) Width

Ferrari 365GTB/4 Daytona
the Daytona during a cold start up, showing the 7.5" rims and Pirelli tyres

Considering the options for fitting 9" wide rims onto the Daytona

With the relatively harsh winter in the UK it probably won't surprise you to learn that the Daytona has not ventured out of the garage for the last few months. I'm certainly missing getting behind the wheel and warm spring days can't come soon enough.

In the meantime I've been looking into a potential upgrade for the car in the form of wider rear wheels.  As standard the Daytona was fitted with 15 X 7.5" Cromodora alloy wheels, with Borrani wire wheels in the same size as an option. It is quite common to see Daytonas running 9" Cromodora rims on the rear as these give it a more planted look, as well as an increase in tyre contact patch. I'm thinking about following suit. 

Researching this further, it actually turns out that Ferrari never offered wider rims as an official option on the Daytona. However, they did homologate the Daytona with 9" rims to allow the race versions to run wider 11" rims on the track. The race wheels were made by Campagnolo and in addition to the 11" rears, the race cars ran 9" rims on the front wheels. It's therefore possible that some Daytonas were upgraded with the 9" Campagnolo rim on the rears when new, even though this was not officially offered. 

Ferrari did in fact deliver one street Daytona, the infamous Harrah hot rod, with the 9 and 11" wheels (see gallery). Purchased by casino magnate and West Coast of America Ferrari distributor Bill Harrah, the Harrah Hot Rod also had a full competition spec engine although it retained all the luxuries of the road car. It is alleged that when a sales man for Sikorsky helicopters tried to sell Harrah a new rotary winged aircraft, Harrah bet the salesman that he would buy the helicopter if it could beat him in the hot rod in a race from Las Vegas to Lake Tahoe. The helicopter lost.

One-offs aside, the majority of Daytonas running wider rear rims have fitted the Cromodora-made 9 X 15" rim used on the later 512 Berlinetta Boxer. Neither Campagnolo nor Cromodora still manufacture these rims new, but occasionally a set appears on eBay, though usually the auction ends for a sum that would be enough to purchase a small hatchback car! The more cost-effective route is to fit reproduction items and both the Boxer (Cromodora) rim and race Campagnolo rim are available through Eurospares and Roelofs respectively. 

Fitting wider wheels will also necessitate a change of tyres. The standard fit tyres for the Daytona are 215/70 15 Michelin XWX's although my car is currently sitting on Pirelli P4000 tyres of the same size. 215/70 15" tyres in a performance rating suitable for the 175mph Daytona are still fairly readily available, with Vredestein and Avon offering alternatives to Michelin and Pirelli. However, the same cannot be said for a suitable tyre for the 9" rim. 

For the Boxer with 9" rims Ferrari again used the Michelin XWX but used 225/70 section tyres instead of 215. For most of the Daytonas running 9" rims these are the tyre of choice, but the XWX is an old design of tyre now and only produced in small production runs, so it's very expensive at over £300 a tyre.

As is the modern way, I've turned to the various internet forums for advice on alternatives. A lot of people are still in favour of the XWX with its rounded sidewall is the most aesthetically pleasing tyre for the Daytona. A number of people have also recommended the Avon CR6 ZZ, which is actually a tyre marketed by Avon's motorsport division as a road legal race tyre for classic cars and is particularly popular with owners of the Ford GT40 and AC Cobra. Despite the marketing intent, consensus on the forums and Twitter is that these tyres are good for 8-10,000 miles (about 3-4 years mileage for the Daytona) and offer good wet weather performance. They are also a little bit cheaper per tyre than the XWX at around £270 per tyre.

There is a downsid, though. The CR6ZZ comes in slightly different sizes to the XWX with the 275/55 15" tyre being the choice I've seen fitted to 9" rims on the Daytona, although there is also a 245/60 version that will fit. With a much squarer sidewall than the XWX, they do give the car a slightly drag racer-esque look and there is the risk that they may rub against the inside of the wheel arch.  

I don't need to make an immediate decision as the Pirellis currently fitted have plenty of life left in them, and I could just replace them with either the Michelins or Avons on the existing wheels. In the case of the latter, I could also go to a slightly wider 225/65 which would increase the size of the contact patch without altering the overall diameter of the wheel and tyre. If you have any thoughts or suggestions on the tyres (particularly the Avon CR6 ZZ)  that I have mentioned above or prehaps a tyre I haven't thought of then let me know either via Twitter or Drive Cult's Facebook page.

Tyre changes aside, in a few weeks time is Goodwood's first Sunday Breakfast (with pre-1973 cars being the featured cars) and if the weather is warm enough and the roads are free of salt then that could be the Daytona's first trip out in 2013. I can't wait.

Finally, a few people have asked me for an update on the Iso Grifo restoration, and I'm happy to report that there will be one in the next month or so.