TimkenLL521849Tapered Roller Bearing Cone Only, 4-1/4 in Bore, Extra-Thin LL Series – Mating Cup Not Included

Product Description

This is a tapered roller bearing CONE – the inner ring complete with its rollers and cage – with a 4-1/4 in (107.95 mm) bore. Read that carefully before ordering, because it is the thing that catches people out.

A tapered roller bearing is a two-part bearing. The CONE is the inner ring, rollers and cage, and it presses onto the shaft. The CUP is the separate outer ring, and it presses into the housing. They are supplied as separate part numbers and both are needed to make a working bearing. This listing is the CONE ONLY. The mating cup for it is the LL521810, and it is NOT included here.

That is not a limitation, it is how the trade buys them. Cups and cones wear at different rates and get damaged independently, so replacing just the failed half is normal practice – and when you do replace one half only, always fit the new part against a cup or cone in good condition from the same designation, never a mismatched pair. Cup and cone raceways are ground as a matched taper; mixing designations puts the rollers on the wrong angle and destroys both.

Dimensionally, the assembled LL521849/LL521810 bearing measures 4.2500 in (107.95 mm) bore x 5.5938 in (142.083 mm) outside diameter x 0.625 in (15.875 mm) width. Note how shallow that is – only about 17 mm of radial section between bore and outside diameter, in a bearing 108 mm across. That is what the LL prefix signifies: an extra-thin, low-section series. You specify an LL bearing when the design has plenty of shaft diameter but very little radial room in the housing, which is common in gearbox output covers, wheel hubs, swing drives and pivot joints. The shallow section limits capacity compared with a chunkier series of the same bore, so it is a packaging choice, not a strength choice.

Because the taper is shallow, this geometry is radially stiff and takes thrust in one direction. Tapered rollers always work in opposing pairs – one bearing takes thrust one way, its partner the other, and the pair is set to a specified endplay or preload at assembly. Setting that correctly is the whole job on a taper installation; too much preload cooks the bearing, too little lets the shaft wander.

The ring is marked MADE IN USA. Also written LL-521849, LL 521849 and LL521849 cone. The mating cup is LL521810; the matched assembly is written LL521849/LL521810.