Tyre Sizes on 105 chassis

["Neil Cotie (EED)" <Neil.Cotie@domain.elided>]

Hi everyone,

There was some discussion about tyre sizes for 105/115 cars.

At the risk of sounding "contrarian" or "old-fogey" at 32 years of age (but 16 years of Alfa experience), I would strongly suggest that 105/115 cars for STREET use should be kept to basically stock width tyres.  

We all know that the 105's as delivered from the factory up to perhaps the early 80's, when the 15 inch phone dial wheels came out on the Spiders, all wore 165r14's.  185/70r14 is the realistic alternative today. If you start throwing on 205 width tyres you can't expect that all you get are benefits.

A few points to ponder, from my humble point of view:
- the Burman steering boxes on most of the earlier 105's are prone to cracks and breakage of the aluminium case.  There's precious little talk about this on the digest and minimal awareness of this in the Alfa community.  Keep your eye on your steering box, folks.  Hope that when it breaks, you're not in an "awkward" situation.  I've broken one while getting out of a tight parallel parking spot that somebody else jammed me into.  The wider your tyres and the further outboard your wheels put the tyres, the easier it is to break the steering box.

- Wider tyres and wheels with small offsets (far outboard) just make for excessive steering effort in most real world situations.  

- Wider tyres have higher rolling and air resistance (i.e. they slow you down in a straight line) and are worse in the wet.

- How often do you really need the additional cornering forces offered by the wider tyre?  Be realistic here.

- With wider tyres it's easier to get a mismatch with the chassis dynamics (i.e. the car overall may be slower or handle worse with the wider tyres, if the rest of the chassis setup doesn't match what the tyres need)

- Wider tyres typically have more abrupt break-away when they lose adhesion.

- The driving experience:  When I want to go fast, the important thing for me is that I *feel* I'm going fast, not the absolute speed measurement.  When it comes to cornering, what really gives me the rush is working near the limit or as close as I can be given the road conditions.  So staying to narrower tyres makes it easier for me to get near the limits and practise being there, while being at a lower (safer) road speed.  The smoother break-away of the narrower tyres is also easier to deal with when learning.  

So which is it you really want?  Just to go fast, or to practise Fangio's waltz with your Alfa?

Everybody has their own preferences, but try to remember that we're talking about old cars here.  Historic cars that are from another era and which should not be judged by today's standards.  And which are a hell of a lot of fun when you take them for what they are.  If you're after a barn-stormer, consider another model of car...

IMHO !
Cheers,
Neil
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