Car and Driver : Impacts of upsizing tires ...

I listened to a video a couple of months ago about the upsized wheels on the new F1 cars. They went from 13" to 18" wheels, and the tech expert being interviewed said that they expected lap times to INCREASE by 2-3 seconds per lap due to the larger wheels. Higher moment of inertia adds a lot of effective mass to the car, making it harder to accelerate and decelerate. Also the shorter sidewall on the tire was forcing a complete retuning of the suspension springs and dampers. On previous F1 cars, the lower spring rate of the taller side walls was a significant part of the spring rate in the suspension.

Another example of going too large on the wheel would be GM's 5th-Gen Camaro. When first released the performance wheel option was 20", but when the max-effort track car Z28 was developed, GM went down to 19" wheels.

Wheels should only be as large as necessary to fit the brakes you need to get whoa'd at the end of the straight. On my Camaro, that meant 17" wheels and C5 Corvette brakes. If I added power, I'd have to put bigger brakes on, then increase to 18" wheels, which are more expensive. Speed costs money, how fast do you want to go?
Rick Ehrenberg has done quite well with 12" rotors and 15" wheels on his Valiant...though he expects to go with 17" wheels at some point, simply due to the lack of available tires for 15" wheels. I wound up doing the same on my Caddy...there just weren't any performance tires available in the size I ran.
 
For the above reason I'll be the last person on earth to paint my fist calipers (on my Mazda) with anything other than a dull silver that attempts to emulate the un-rusted, as-delivered rough casting look. H*ll, I don't even think that fist calipers (as opposed to four-or-more opposed piston calipers) are worth celebrating (in bright red or fly-yellow) 😇.
Flat black caliper paint is best. (It throws off heat better.)
 
Flat black caliper paint is best. (It throws off heat better.)
Up until 6 months ago, I would have 100% agreed. I've recently seen, but cannot find to cite, that almost all (non high gloss) paints are equally emissive. If you have a technical citation on what I thought as well, I'd like to see it. I'm researching emissivity for its effect on results with my thermal camera work.
 
17s and 18s...check. No way I'd run 19s with 35 tires. Love these Apex 18x8.5 et43s with 235/40s. Also running 10mm spacers up front and 15s out back (clears brakes without). Clear my 350mm BBK with room to spare. Apex's 17x9 in the same model will also clear which is crazy and will be my next set to run 255/40s for track.

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Up until 6 months ago, I would have 100% agreed. I've recently seen, but cannot find to cite, that almost all (non high gloss) paints are equally emissive. If you have a technical citation on what I thought as well, I'd like to see it. I'm researching emissivity for its effect on results with my thermal camera work.
HS physics showing black throws off heat best...and several companies switching to black engine paint in the 80s as emission controls made them run hotter. I will note that axles, brake drums, and most transmissions on the trucks at work are all flat or satin black.
 
HS physics showing black throws off heat best...and several companies switching to black engine paint in the 80s as emission controls made them run hotter. I will note that axles, brake drums, and most transmissions on the trucks at work are all flat or satin black.
Don't get me started on black intercoolers...
 
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