Should I use 14' or 15' wheels?

Griff · Griff's Garage

I have a 1970 Porsche 911 E with the original 14’ wheels. It’s time to purchase new tires and I need to decide if I should upgrade to a 15’. I have heard some pros and cons about the bigger vs. smaller wheels. I have heard that the smaller wheel generates more low-end torque. Does anyone have any thoughts on wheel size and tire size and what tires I should consider knowing that I am on a budget?

Thanks,

~ Griff

masraum · 06-10-2003, 11:07 AM

Well, at this point I think the problem is in getting decent tires for smaller wheels. I would probably go with 15's, but then again, if you can't afford 15" Fuchs, then just get new tires and save up for some new Fuchs.

DByers · 06-10-2003, 11:31 AM

I put Dunlop SP Sport 2 (P195/70 R14) on my 71 last year and have been very pleased with them. Yokohamas also have a good tire. Check with Tire Rack. Here is a link to the Dunlops
Dunlops SP Sport A2
I am planning on going to 16s Fuchs soon, but will keep the 14s

azasadny · azasadny's Garage

I put Dunlop Sport 9000's (215/50/15 on the rear and 205/50/15 on the front) on my 15" Fuchs this spring and have been very happy with them. Because 15" tires aren't always readily available, I had to order the tires from a local shop and wait a week or so for them. I'm eventually going to get 16" wheels, but I'll keep the 15" for now.

slammed1000 · 06-11-2003, 06:37 AM

18" would look nice!

slammed1000 · 06-11-2003, 06:38 AM

18" would look nice

masraum · 06-11-2003, 07:06 AM

18 might be a bit much on an early narrow bodied car.

DByers · 06-11-2003, 07:49 AM

Steve, I have a co-worker who swears he can some 22s on my 71. ;-)
But I think 16s would be about max. (16X7 r / 16X6 f)

304065 · 06-11-2003, 07:55 AM

There are four things to consider re: wheel size vs. performance.

The first is gearing. If the circumference of the 15" is the same as the 14" there's no change. If the overall circumference is smaller you have lowered (numerically raised) the overall gear ratio. This will give you greater torque multiplication and a quicker launch at the expense of top end. If you are autocrossing, this is a great choice if the rules permit.

The other factors are overall weight of the tire and wheel. I don't know the weight of a 14" fuchs offhand, you might weigh it and compare it to a 15". The polar moment of inertia of the wheel, or how much mass is distributed with respect to the wheel center, is another big factor, but as you are comparing fuchs to fuchs there's not much that can be changed. Finally the sidewall height: if you keep the circumference constant, then the 15" may have a lower aspect ratio (ratio of sidewall height to tread width) and give you less rollover in the corners, which is good, but will raise the spring rate of the sidewall, giving you a harsher ride.

18"s won't fit, even with 30-series rubber and would cost 1/4 the value of the car. . . not compatible with the budget.

You can get a set of 15x6" for $300-$500 depending on condition, just roll the fender lips and fit some 205/55 rubber under there and you're in business.

87wbtarga · 06-16-2003, 11:53 AM

Griff,
I have a '72 E, and a set of 15" and 16" wheels. I believe that your fender shape is the same as the '72. I am able to fit 205/50 tires on both sets of wheels, with the car lowered, and stiffened. I use the 15" for AX, and the 16" for DE. The lower rotating mass, and smaller diameter of the 15" make for a significant change, with improved acceleration, with my limited horespower.
The only spots I see rubbing are an occasional inside the rear wheel well (with 16" wheels), and some marks on the inside wheel well in the front, from turning too tight.
Since mine is an E as well I have thought about finding some 14" to try, but have held off, since I was not sure of the rubber available, and how a 205 width would fit a 5.5" wide rim (I think the 14's are 5.5" wide).
So depending on your application(s) you will need to decide.

best of luck,
Eric