Bicycle Mechanics - Seeking new cone for old hub
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05-22-12, 06:22 PM
I have an older Trek 820 mountain bike that I recently picked up for my daughter. (Early 90s? - it has a cup and cone bottom bracket.) The left cone in the rear hub has some pitting and I would like to replace it. Problem is, I don't know exactly what I have so I'm having trouble figuring out if any of the current offerings will work. Of course, the sticker that used to be on the hub is long gone.
What I do know:
- It's a 126 mm hub. It came with a 7-speed cassette.
- nine 1/4" bearings on each side
- dust cap says Shimano FH-HG20
- the cone is 15.4 mm long and 17 mm in diameter
- axle appears to be 10 mm diameter with about 10 threads/cm (but I don't have a thread gauge)
- the front hub still has its sticker, which says Shimano HB-RM50 sealed mechanism
05-22-12, 06:31 PM
You have a very conventional Shimano 7-speed hub. The axle is indeed M10x1.0 (10 mm diameter x 1.0 mm thread pitch) with 9x1/4" balls/side and both are absolutely standard. Take the axle and the cone to a decent bike shop and see if they can match it and/or come up with a suitable replacement.
05-22-12, 06:38 PM
If they don't have it locally these folks most likely do. http://wheelsmfg.com/products/all-cones.html
05-22-12, 07:21 PM
I would prefer to order online if I can identify what I need. I'm a little frustrated with my LBS right now....
05-22-12, 07:40 PM
Hub cones are one of those things where visually matching the length and angle are critical for best performance.
Wheels Mfg. for example doesn't show your particular part in their line of replacements. This is where going to a
LBS to see if they have the part is going to work best. If not, then the next step is to either replace the wheel, or find
a wheel at the bike co-op with the same hub, then use those hub parts (if they're in good condition).
I might have a decent HG-20 rear hub with a shot rim; if you can't find the cone locally send me a PM and I'll look for you.
05-22-12, 07:59 PM
Thanks oldskool. I'm guessing I can get this one to work, but I'll let you know.
Is it typical for bike shops to have a selection of cones in stock at any given time? If not, how do they identify the best replacement part? Do they typically have a visual reference that they can lay the cone over to see if it's a match?
05-22-12, 08:41 PM
Is it typical for bike shops to have a selection of cones in stock at any given time? If not, how do they identify the best replacement part?
Do they typically have a visual reference that they can lay the cone over to see if it's a match?
Generally shops will keep a selection of cones in stock for the most current (and 'popular') hubs, but may have to special order cones
for older hubs. The only way to be sure of an exact match is physically matching the old one to a new one. In your case, you
definitely have an older hub, but fairly common on many bikes. That's why the 'pretzeled wheel' route may be the most economical
way to go, but totally based on the condition of the donor hub. If you have a co-op in your area, take a look at a couple and spin them
in your fingers.
05-23-12, 01:08 PM
I recently went through an old Schwinn hub. Finding cones for it online seemed nearly impossible, one of the newer LBS who didnt have a pile of old stuff laying around couldnt figure what to order either. I finally brought a couple of beers into one of the older shops and asked to scrounge through there old bin of extras. After digging for ~15min I found some that matched up "close enough".
So,,, go to the LBS.
05-23-12, 01:38 PM
Since this is a Shimano hub and all Shimano hubs use the same 9x1/4" bearing ball count, the "angle" will all be the same for any Shimano hub cone as will the threading. What will vary is the length of the cone nut and the interface with any dust caps or O-ring seals. You may have to find a near-miss and use spacers to get the correct locknut location.
05-23-12, 02:10 PM
Thanks for the advice. I'm going to call around to see if any LBS have a selection of cones for me to look at. If I don't come up with anything, I will take a chance on internet ordering something that looks close. I am confident I can match the physical dimensions (length and diameter of the entire part), but I don't know about the dimensions and curvature of the bearing surface. HillRider - is that what you mean by angle? This cone has no o-ring seal, so that isn't an issue.
Loosescrews.com has a Wheels Manufacturing cone (CN-R024) that it says fits several Shimano hubs, including the HG20: http://www.loosescrews.com/index.cgi?d=single&c=Hub&sc=Cones&tc=Shimano%20Rear&item_id=WB-CN-R024&id=78862384266 That may be the one I try if I order online. Other vendors don't list HG20 as compatible with this cone, though.
05-23-12, 02:53 PM
Yes, the curvature of the cone where the bearing balls run was referred to a "angle" in a posting above so I just reused the term. I guess it was a bit misleading. The Wheels Mfg. cones should work fine.
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