Are Harley-Davidson bolts metric or SAE?

Predominantly SAE (inch) across the chassis, with Torx on many controls, covers and the primary. Some fasteners and components are metric, so the reliable answer for your model year is the service manual.

What Torx size do I need for a Harley?

T27 is the size riders most often carry, with smaller sizes for switch housings and trim. Carry a bit set rather than a single driver.

Do I need chain tools on a Harley?

Not on a belt-drive model — and a broken belt is not a roadside repair. Check your own bike first; some models and customs run chains.

Harley-Davidson tool kit: the inch sizes and the T27

Updated 2026-08-09

A metric-only kit will let you down on a Harley-Davidson. Big Twins and Sportsters use SAE (inch) fasteners across much of the chassis, so a 13 mm spanner that nearly fits a 1/2in head is exactly how fasteners get rounded off at the side of the road.

The second surprise is Torx. Harley uses Torx widely on controls, covers and the primary — T27 is the size riders mention most often — and it does not share a driver with a hex key. Model years vary, so confirm against your own service manual rather than a forum list.

Inch sizes, not millimetres

Build the kit from a fastener audit rather than a set: walk the bike and note the sizes on the axles, the pinch bolts, the mirror and lever clamps, the battery terminals and the primary cover. On most Big Twins these come out in the 7/16in to 3/4in range, with a large axle nut at the top end.

Buy the sockets and combination spanners in SAE to match. Where a metric tool nearly fits, it is not fitting — it is slipping under load.

— Axle and pinch bolts: the largest sizes on the bike, and the ones you cannot improvise.
— Torx on controls, covers and primary — T27 is the common one, plus smaller sizes on switch housings.
— Allen (inch) keys on some covers and accessories.
— Battery terminals and the seat bolt that stands between you and them.

Belt drive changes the spares list

Most modern Harleys run a belt, not a chain. That removes the chain tool, the master link and the chain lube from the kit — a genuine weight saving — but it also removes the option of a roadside repair. A shredded belt is a recovery, not a fix, which makes tyre repair, electrics and fasteners the parts of the kit worth investing in.

Chain-drive models exist, including some Sportster-era and custom builds, so check your own bike before deleting the chain tools.

Wheels and inflation

Cast wheels on cruisers and baggers are tubeless, so a plug kit and inflation cover the common puncture without removing anything. Spoked wheels on some models run tubes — those need irons and a spare tube instead.

A heavy, loaded bagger makes a low tyre feel like a handling problem long before it looks flat, so a gauge you trust is worth more than its weight.

Vibration is the real failure mode

The recurring roadside complaint on big V-twins is things working loose: mirrors, licence plate brackets, exhaust shields, luggage hardware and accessory wiring. That makes threadlock, an assortment of SAE hardware, and a few minutes with a spanner at every fuel stop more valuable than an exotic tool.

Fuses and a length of wire belong in the kit for the same reason — accessory looms on heavily farkled bikes are the usual suspect when something electrical stops working.

The kit, item by item

Combination spanners — 8, 10, 13 mm
In SAE sizes — a near-fit metric spanner rounds heads.
Where to buy:Amazon
Torx bit set — T25, T30, T40, T45
T27 plus the smaller sizes on switch housings.
Add T50/T55 as a socket if your bike uses Torx axle or caliper bolts.
Where to buy:Amazon
1/4in ratchet + sockets (8, 10, 12, 13, 14 mm)
Only the inch sizes your audit actually found.
A stubby ratchet plus a short extension packs smaller than a full socket set. Add a 1/4in-to-hex-bit adapter to share the ratchet with your bits.
Where to buy:Amazon
Tubeless plug kit (sticky strings or mushroom plugs)
Cast wheels are tubeless — plug and inflate.
Rasp + insertion tool + 5 plugs. Vulcanising strips are more durable than cheap rubber strings.
Where to buy:Amazon
Threadlocker (small blue tube)
V-twin vibration undoes what you tighten.
Where to buy:Amazon
Spare nuts, bolts and washers (your bike's common sizes)
SAE hardware, not metric.
Where to buy:Amazon
Spare fuses (full set of your bike's ratings)
First suspect when an accessory circuit dies.
Check the fuse box lid for ratings; carry two of each plus the fuse puller.
Where to buy:Amazon
Tire pressure gauge
A loaded bagger hides a soft tyre.
Where to buy:Amazon

Generate the full list for your own bike

Questions riders ask

Are Harley-Davidson bolts metric or SAE?: Predominantly SAE (inch) across the chassis, with Torx on many controls, covers and the primary. Some fasteners and components are metric, so the reliable answer for your model year is the service manual.
What Torx size do I need for a Harley?: T27 is the size riders most often carry, with smaller sizes for switch housings and trim. Carry a bit set rather than a single driver.
Do I need chain tools on a Harley?: Not on a belt-drive model — and a broken belt is not a roadside repair. Check your own bike first; some models and customs run chains.