QUOTE(Pat Garvey @ Aug 6 2007, 11:34 PM)
Ok, we have several threads going that have been hijacked to "We Be Tires for CW's". Let's start fresh here, so it's all in one place.
As I see it, the primary questions are:
1. Are vintage tires available? And I'm talking about original sizes. Where? How much? What are the advantages/disadvantages of these tires?
2. Are contemporary tires available in vintage sizes? Same questions as in #1.
3. Who's doing what about this situation? Are you caving to current tires, etc.? Why/why not?
4. Are the concours advantages to remanufactured vintage-sized tires worth worth the cost, from a performance/safety point of view versus maintaing purity?
Pat
First thing is to establish what constitutes the original tire provided by Porsche. From what I can find:
914-4's came with either 4 1/2" J x 15 with 155SR15 tires
or 5 1/2" J x 15 with 165HR15 tires
914-6's came with 5 1/2" J x 15 with 165HR15 tires
or 5 1/2" J x 14 with 185HR14 tires
The combination of of rim size and tire offering appears to be independent of whether it is a steel wheel or alloy.
I know Michelin ZX (155SR15), XAS (165HR15) and XWX (185HR14) appeared on delivered cars in the US. I can recall both a Dunlop and Continental tire also appearing but for the life of me I cannot recall the model name that they offered.
My point is, nowhere can I find mention of the tire brand provided, either is spec books or advertisements.
Vredstein Sprint was a favorite during the '70's as a replacement tire. Uniroyal, Firestone, BF Goodrich and Goodyear all had matching tire sizes.
Both XAS (165HR15) and Vredstein (155SR15 and 165HR15) are available from Coker Tire at $191, $79 and $89 respectively.
Having run several lower profile "contemporary" tires, and currently the XAS's, only disadvantage I have found is the "skinny" vs. "wide" appearance. On the plus side, with the XAS's, my speedometer finally is correct, and the ride is less harsh. If I were autox'ing, I'd want the lower profile for sure. Cost of the XAS is high compared to the majority of contemporary tires running around $85-$90.
There are other tires of the period that would fit, however they do not have the correct speed rating.
Contenporary tires I've found that match include BFGoodrich Radial TA (155SR15) at $62.
I opted to go the XAS route as my spare wheel has the original 165HR15 XAS on it and I am not likely to campaign my 914-6 is any autocrosses. That and an eBay deal that I could not refuse (seller purchased the Coker Tires and must have decided that they were to "skinny" for his liking.)
From a performance and safety point of view, I don't see any problem with using the Coker Tires, as it is my understanding that the tires are today's construction techniques with the original molds used for tread and sidewalls. The HR speed rating is certainly adequate for my needs.
How far you go in respect to obtaining a Concours advantage is open to question. If I hadn't had the original spare, I most likely would have opted for the Vredstein to save some cash.
If I had a VERY prepared car underside, I might have opted for the contemporary tires, and acknowledge that I may receive a demerit or point reduction during a Concours judging.
Knowing what class your going to be entered in may also enter into your decision on which way to go. Only in the Preservation Class would I think it necessary to have the original tire size of whatever brand that is available.