Tuesday, October 16, 2007

Shimano Hub TLC

'Decided to overhaul the Shimano hubs in my stable:

They consist of a pair of 1991 Shimano DX hubs (HB-M650 and FH-M650), a 1996 Shimano LX Parallax Front Hub (HB-M564), and a 1997 Shimano XT Rear Hub (FH-750).

SteveUK posted an excellent write up on this procedure. Click on the image or here.

Tools required

Chain whip
Hyperglide cassette remover
13 mm Cone wrench (front hub)
15 mm Cone wrench (rear hub)
17 mm Cone wrench. The locking nuts of the FH-M750 XT rear hubs come with flanges, regular wrenches won't fit.
Large Adjustable Crescent wrench
Long 10 mm Allen Hex Wrench

I rarely open up my hubs, but when I do, I replace the ball bearings.

Ball bearings come in different grades. The higher the number, the lower the tolerance. I.e. the greater its deviation from the dimensions of a theoretical, perfect sphere. Grade 1000 is too low a grade to be used in Shimano hubs. Grade 100 is acceptable. If memory serves, Shimano uses Grade 45 bearings in their hubs (up to XT). Shimano XTR and Dura-Ace use Grade 25. Enduro has Grade 5 ceramic bearings. Another dealer offers Grade 3 ceramic bearings.

John kindly pointed me to a local business that sells high quality bearings. Located along Jalan Besar, near Singapore Casket (where you can get beds with a lifetime guarantee :-D ), SLS Bearings (S) Pte Ltd is an authorized distributor of SKF bearings. Trivia: Leonardo da Vinci conceptualized the ball bearing around 1500 AD.

Bearings are sold in minimum quantities of 100 pieces. While I do not doubt the quality of the bearings delivered to SLS, their storage procedures seem inadequate. Many bearings were marred from oxidation.

3/16" (4.762 mm) Bearings
Grade 40
Part Number:  NIS RB 4.762 G40
SG$5 (US$3.41) for 100
Inspected:  50
Rejected:  10
Good:  40

1/4" (6.35 mm) Bearings
Grade 40
Part Number:  AKS RB 6.35 G40 (1/4)
SG$6 (US$4.10) for 100
Inspected:  100
Rejected:  61
Good:  39

Inspection was carried out without aid of a magnifying glass or high-powered desk lamp. If I used them, the rejection rate would probably be significantly higher. In other words, buy a lot more than you need.

Note: if you have Dura-Ace or XTR hubs, they come with Grade 25 bearings. I.e. Grade 40 is too low a grade for your hubs. At the very least, you need Grade 25 or better.

Removing the freehub cassette body bolt can be a royal pain in the rear as the 10mm Hex bolt is torqued down to 36 ft/lbs or 50 Nm. Many mechanics end up clamping the 10 mm Allen key to a vise and cranking on the wheel with both hands in order to break the bolt free.

Even at 7 - 15/32" (190 mm), the long Allen key may prove insufficient (without resorting to a vise). Park Tool has an extra long version to address this.

Never one to follow the crowd or convention, I sought another way.

I did it my way! A 16 - 5/8" (422.3 mm) Craftsman 1/2" Drive Flex Ratchet makes short work of the freehub cassette body bolt. With over 8 cm more leverage, at 19 - 13/16 (503.2 mm), the Craftsman 3/4" Drive Quick Release Ratchet is also a great contender.

Overkill? Maybe.
Fun? Definitely.
Why bring a tank to a knife fight?
Because it's fun.
Because it's viscerally more satisfying.
And more importantly, because I can  :-P

1 comment:

Anonymous said...

Lol, I found this sitesearching for skf bearings, luckily Martin at http://www.halifaxbearings.com sorted me out. Gawd knows what I'd have found looking for dodge or NKE bearings.