Lessons learned VTO Retro 4 15x7 P12

[TurboRagtop]

Shannon,
What are your thoughts on mounting this combination on my '66 roadster, given the smaller wheel house in the front, vs. the later models?
Here's my alleged math...

Current setup 195/60-14
195 Width (mm)
7.68 Width (in)
0.6 Aspect ratio
4.61 Tire height (rim to tread)
9.21 Tire height (total rubber)
14 Rim dia (in)
23.21 Total height of tire/rim assy

New setup (like yours) 195/45-16
195 Width (mm)
7.68 Width (in)
0.45 Aspect ratio
3.45 Tire height (rim to tread)
6.91 Tire height (total rubber)
16 Rim dia (in)
22.91 Total height of tire/rim assy

-1% Change in percent


Thanks.

Karl

[sfdaugherty]

Karl: I run very thin spacers in the front to clear the hubs (maybe1/8”) so you can probably gain a bit by machining the wheels. I don’t have any clearance issues in the front. The back is very tight (can hardly fit a finger between the tires and the fender.

Shannon

[sfdaugherty]

I forgot to ask if the offset is the same.

[TurboRagtop]

Shannon,
I plan to order the same offset as you went with: +12.
Still plotting my strategy, but what are the PROs and CONs of a 16 inch wheel vs. a 15 inch? I can do either, but I have a somewhat high HP car and I know I will need as much contact patch as possible.

Thanks.

[sfdaugherty]

I'm not an expert. I chose the 16" wheels because I like the look. Some hate it. If you need a larger contact patch, you need a wider tire.

[Pjackb]

Shannon,
I plan to order the same offset as you went with: +12.
Still plotting my strategy, but what are the PROs and CONs of a 16 inch wheel vs. a 15 inch? I can do either, but I have a somewhat high HP car and I know I will need as much contact patch as possible.

Thanks.

16 vs 15 on a lightweight car

Pros:
Looks
More tire selection (especially if you go 215 or 225 in the rear)
Big brake clearance (but not really an issue with 15s )

Cons:
Weight
Costs
Ride quality

a 205 tire on proper width wheel will have the same contact patch regardless if 14,15, or 16 , going wider is fine but there's actually a point of diminishing return in plus sizing.
Here's a great article on the subject by Car and Driver https://www.caranddriver.com/features/e ... res-tested

Going plus 1 every time they tested 195/15, 205/16, 215/17, 225/18 and 235/19 inch wheels and tires sticking with sames brands and acceleration was slower with each up size with a full second and 2mph in the 1/4 mile from best to worst

I would check with Michael and Kevin what they're putting on their turbo cars but I believe it's 225 with the RX7 rear conversion

[TurboRagtop]

Great article on plus sizing, thanks.

[RCMike]

a 205 tire on proper width wheel will have the same contact patch regardless if 14,15, or 16 , going wider is fine but there's actually a point of diminishing return in plus sizing.
Here's a great article on the subject by Car and Driver https://www.caranddriver.com/features/e ... res-tested

Going plus 1 every time they tested 195/15, 205/16, 215/17, 225/18 and 235/19 inch wheels and tires sticking with sames brands and acceleration was slower with each up size with a full second and 2mph in the 1/4 mile from best to worst

I would check with Michael and Kevin what they're putting on their turbo cars but I believe it's 225 with the RX7 rear conversion

There is more going on there, but it is an interesting article. The overall size gets larger as they get up there, with the biggest being a half inch taller than stock. That is the equivalent of putting in a taller final drive, which will hurt acceleration. And braking and acceleration will suffer as the shape of the contact patch gets shorter but wider, while change of direction will get better.. Would love to see a slalom in the test..


On the cars Kevin builds, 205 is as big as fits under stock fenders. Unless someone wants to significantly enlarge the rear fenders, wider will cause rubbing.. Now, Kevin's dad car is wider, with flared fenders. My green car will also be wider, because the fenders were significantly widened..