Tuesday, November 30, 2010

Of wheels and tyres

One of the consequences of leaving the Ricciardi in storage for so long has been the need to replace the tyres. In fact the A509s still have masses of tread, but they were on the car when I got it, and must now be 14 years old or more - long past the expected life for a set of sports tyres. I've always felt that they were too wide for the car (at least on the road), so this is also an opportunity to go down to 195mm.

I've also been wanting to replace the wheels with some suitable alloys, so this looks like the time to do both.

One of the great things I'm finding about the modern Alfa Scene is the proliferation of manufacturers and suppliers of new parts. This is balanced to some extent by the rarity and high cost of many original parts (cough...brake boosters..cough), but it does mean that there are many options for things like wheels. An evening of browsing, and some photo editing with GIMP, and I've made my selection - replica GTA wheels, keeping the 14" size. A couple of Alfa specialists in the UK supply them, and at least one place in Melbourne imports them. Here's a quick GIMP mockup of the car with GTA-style wheels (I did a cr*p job of altering the perspective on the front wheel, which wasn't square to the camera).

Tyres are another matter. 14" is no longer the wheel size of choice for sports car manufacturers, and there are no performance tyres available in 65 profile, the size necessary to keep the gearing correct with 195mm tyres on a 14" rim.

A plaintive cry for help on the AROCA forum elicited a number of suggestions in 195x60, but I'm not prepared to drop the overall gearing any further. I've accurately measured the speed at an indicated 5700rpm as 170kph. The tacho may not have been accurate, but if it was then the diff ratio must be 4.55 - the lowest 105 ratio made, and very rare these days. Hugh reckons it's more likely to be the standard Berlina ratio of 4.3, but either way it doesn't need to be any lower.

Searching the web and ringing a few tyre retailers didn't help much, especially as the immediate response of the latter was to try and sell me a 195x60 road legal race tyre. My actual requirements are very different. At the moment I want, not ultimate grip, but progressive, predictable behaviour and excellent wet weather grip. The Ricciardi has always been an inveterate aqua planer, and needs all the help it can get when the heavens open.

At the moment I'm leaning toward one of the "all rounder" tyre models that are still available in 195x65 - Goodyear Eagles, BF Goodrich Sport/TAs, Bridgestone Turanzas, Yokohama A.drives, etc. Vin Sharp from PACE Engineering has suggested Michelin XM1s - he recently bought an Alfa 75 which happened to be shod with them and said they were surprisingly grippy at a track day. Perhaps more importantly, he found them very progressive, which is music to my ears.

I suppose the other possibility is to go up to 15" wheels and something very low profile, but I shudder to think what the ride would be like.

More thinking required.

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