Tires - performance versus vintage

[helowrench]

speedo works from the left front wheel

[fosd]

I was intrigued by Icvaldetaro’s (Luiz) observation (5/19/13) that increasing wheel size (from 4.5’ to 5.5” greatly improved his tire performance, and was hoping for some help in understanding why this is so. My problem is similar.
I have a very stock '71 Ghia with 185/65r15 Goodyear Integrity tires on 4.5" stock wheels that seem to have almost no traction in the rain. I’m planning on upgrading to some slightly wider Michelin Premier A/S 195/65r15s tires that are highly rated for wet weather, but I was going to just put them on my 4.5” wheels. So my questions are:
1. Is 195/65 tires on 4.5” wheels a really bad idea?
2. What are the biggest tires I can put on 4.5” wheels?
3. Should I just go ahead and buy 5.5” wheels and wider for better traction?
4. What is the max tire size I can buy for the new 5.5” wheels?
Thanks muchly.
Dwight

[helowrench]

Fosd,
I can give some very directly relevant info, as I am in a 71 ghia also.
195 wide will fit on the 4.5s, but due to the rim width, you probably will not gain any more contact patch. 185is already almost too big for a 4.5.
Now, let me ask you two things about the tires that you currently have mounted.
1 what is the age of those tires?
Unfortunately?!? Our cars do not wear out the tires quick enough, and this causes us to end up with old, hard tires (due to age as the rubber outgasses the volatile compounds).
2 what pressure are you running? Tire pressure is critical on these. Should be somewhere around 24rear 20front, unless those tires have very thin sidewalls, which will make them squirmy.

[helowrench]

Foss, to touch on the other part of your question, backpacking choice on rims is also critical for fitment on a ghia rear.
I had 5.5 wide 8 spokes for years, but could not run anything wider than a 165 tire, as even then the drivers rear would rub on full compression.

Now I have the 914 mahle rim, and 205wide, and could probably even run 215 as I still have room left.

[helowrench]

My mahles are 5.5 wide.

[RHough]

The new series 8 spokes from CIP have a large backspace and 195/65R15's fit at stock ride height on my IRS '72 coupe. The rears just rub a bit on autocross runs ... you should never have that issue during normal street driving.

That said I'm going with narrower tires. I will end up with the 175/70R15 to have the correct 25" height no rubbing ever and a period correct look. The 195/65s are just too wide to look right.

Edit/Update:

Wow. 175/70R15 is a tough size ... looks like the current choices are P6000 Pirelli 185/70R15 for $195 a tire or 165R15 Michelin XAS at $240 a tire ... I could just run Avons all the time ...