The gear that lives in the boot.
Accessories are usually the least evidenced corner of a site like this one — a wall of star ratings and no numbers. It turns out they do not have to be. Inflators get timed to the second, jump starters get measured in cranking amps, and phone mounts get pulled until they let go. Where those figures exist we print them with their conditions; where they do not, we say so and talk about fitment instead.
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Cargo
The empty rack was the expensive part.
Measured at 65 mph: the rack alone, carrying nothing, cost a sedan 11 per cent and an SUV about 2. And a hitch carrier returned 4 mpg more than a roof box on the same car.
−11% with nothing on it
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Inflators
Four minutes, or fourteen
Six inflators, one tyre, timed from 10 psi. The quickest reached 30 psi in 1:34 and the slowest took 6:40 — and the figure everyone quotes flatters the small pumps.
1:34 – 6:40 to 30 psi
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Jump starters
3000 amps. For a twentieth of a second.
Peak amperage lasts 20–50 milliseconds; cold cranking amps is sustained for thirty seconds and is what your battery is rated in. The two units advertising the highest peak publish no CCA at all.
425–700 A sustained
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Phone mounts
“Tested for hold strength.” No strength published.
The top result is written by a mount manufacturer, ranks its own product first, and contains no hold-strength figure in any unit — we checked all six. What can be checked instead.
0 figures published
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Tool
How long will your tyre take?
Published times are measured on one 245/50R20. Enter your own size and the measured times scale to it — the ratio is honest even though the absolute volume is not knowable.
Any size, any psi span
What this section recommends
One product per page, each chosen on the measurement that page reports. Amazon holds the live price; we do not copy prices onto the site.
Check priceDeWalt DXAEJ14
Highest published cold-cranking figure of the seven
from Jump starters: peak amps is not the number that starts your car
Check priceiOttie Velox magnetic vent mount
A genuine MagSafe mount, not a disc needing a plate stuck to your phone
from MagSafe car mounts: hold strength promised, never published
Check priceSlime Cordless Pro Power
Third fastest to 30 psi, at half the weight of the two quicker units
from Tyre inflators: the fastest is 4.3× the slowest, on the same tyre
Product photographs: DeWalt, Slime, iOttie.