Tapered Roller Bearings - Why?

[ddaniels]

The main issue with tapered roller bearings is that they not only withstand radial loads, or rather, sideloads, but they also withstand axial loads, or front to back loads. If you draw a line from the center of the race out to the center of one of the ball bearings, that is the radial direction. If you draw a line straight through the center of the race that is parallel with the shaft, or whatever, that the bearing is mounted on, that is the axial direction. So, ball bearings provide, usually, only radial support. There are bearings that provide only axial loads and they are call "thrust" bearings. tapered roller bearings provide both. Needle bearings also only provide radial support. I would not think that tapered roller bearings would be necessarily required for steering heads, but couldn't hurt.

[UncleMike]

i know these are in the uk but these seem a pretty good buy. both bearings, 2 seals and bearing grease.
http://www.ebay.co.uk/itm/Yamaha-DT1...ht_1576wt_1271

Ordered! Thanks.

[UncleMike]

The main issue with tapered roller bearings is that they not only withstand radial loads, or rather, sideloads, but they also withstand axial loads, or front to back loads. If you draw a line from the center of the race out to the center of one of the ball bearings, that is the radial direction. If you draw a line straight through the center of the race that is parallel with the shaft, or whatever, that the bearing is mounted on, that is the axial direction. So, ball bearings provide, usually, only radial support. There are bearings that provide only axial loads and they are call "thrust" bearings. tapered roller bearings provide both. Needle bearings also only provide radial support. I would not think that tapered roller bearings would be necessarily required for steering heads, but couldn't hurt.

GREAT explanation! Thanks!

[850 Combat]

I'll bet that it (DT175) has plastic bushes in the swing arm like my RD400 came with.

[BentRod]

Tens of millions of motorcycles have been sold with nothing more than special design ball bearings in the steering neck. I agree that taper roller bearings will be more durable, but I wouldn't go off replacing the ball bearings that came with the bike from new unless they are worn out.

Agreed. If it isn't busted, leave it alone.
I simply wanted to advocate that there is a lot more to bearing selection than a simple cost/quality or better/worse type decision.

Additionally, ball bearings, thrust bearings, tapered roller bearings, each comes with different installation and geometric considerations. For example, given a pair of ball bearings, one installed at each end of the steering neck, both will take axial load. However, with tapered roller bearings, one bearing will be inverted, and will carry no axial load. This difference will effect how the load is then supported by the frame.

[UncleMike]

i know these are in the uk but these seem a pretty good buy. both bearings, 2 seals and bearing grease.
http://www.ebay.co.uk/itm/Yamaha-DT1...ht_1576wt_1271

I got these and they look to be of pretty good quality, but the installation instructions they promised were included were not in the package, but instead supposed to be offered on the website.

Visiting the website, the page that's supposed to house them is blank, with a promise that they'll be coming in the future. The live support system is never on, emails bounce back and calls go to a full inbox.

Guess you can't count on much customer support from Pyramid Parts.

[tkent02]

Yup, longevity from having a load spread out instead of covering one small point on a ball. It was a big deal back in the '50s when Harley went from roller bearing cranks to Timkens.

Timken is just a brand name, not a bearing type.

I'm curious what type did Herdely go to for crank bearings?

[850 Combat]

Norton 850's used barrell shaped main bearings. Balls wern't up to it, and rollers didn't appreciate the crankshaft flex. They called them "Superblend" Norton didn't invent them or anything.

Bottom ends started lasting longer. The Combat 750's had bottom end problems with roller bearings on the primary side main.