Mountain Biking - What bearings can I use to replace those in 20mm hubs?
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07-10-10, 11:18 PM
Since I'm upgrading to a 20mm axle up front with a new fork/front wheel, I figured I'd look ahead to see what's involved with replacing the bearing. Since I already went through the process of overhauling my rear wheel, I wanted to see what was different with these 20mm front hubs.
Can I buy just any bearings that are listed for 20mm axles? Do I have to get a specific brand? If I have a Shimano hub, do I need Shimano bearings? A quick ebay search finds two auctions that appear identical, but the title says 20mm 6805 and another says 20mm 6804.
What's the difference? Also - how hard is it (and what tools are needed) to do this task?
Like I said, just trying to look ahead. Thanks!
07-12-10, 08:39 AM
Well, I scanned ebay quick and found this auction:
Okay, so that appears to be the style bearing I need. I can only imagine there are many different kinds, due to the fact I saw an auction listed for 20mm 6804 bearing, 20mm 6805, etc. I'll have to figure that out when I ever need to get bearings.
Question, though. How many of these are used? Is there only two of them used, or do you "fill up" the axle so they are spaced the entire way across the axle? If so, generally how many of these bearings are used?
Does anybody find they have a preference, in terms of these style bearings vs open bearings?
6804 and 6805 are standard industrial sealed cartidge bearings. A bearing is a bearing, unless they are ceramic or something else really special. Blue seals (like your link) are nothing special. Green seal is a bit better grade of bearing. In those thin-section bearings, number/size of balls are probably going to be the same no matter the grade. If you live in/near a town of any size there is probably an industrial bearing supply (or two) that can match those numbers for you.
Now, the difference between 6804 and 6805: 6804 is a 20x32x7, meaning your axle will fill the ID. 6805 is a 'nuther animal: it is 25x37x7. there must be a bushing sleeve that slips through the inner race that the axle then slips inside of. Do I understand that you are converting a QR front hub to 20mm thru-axle? You will need a bearing with the sme OD as what's in it and (easiest way) 20mm inner race ID. Your hub will be either a 2-bearing hub (likely) or a 4-bearing. That is all you will need for quantity.
07-12-10, 10:53 AM
Thank you for the response. I was banking on assuming the official type of bearing would be stamped/printed on the side of the bearings within the hub, at which point if I ever need to upgrade, I can take one of those to a shop and see if I can get the exact same ones. I know at that point I'd also see how many bearings the hub rode on, but I didn't want to dismember the bearings from the hub just to see what's up. I'd rather leave everything intact until I NEED to do replacements.
I find it pretty interesting that a front wheel rides entirely on two of those bearings. With them being smaller bearings, do they tend to wear out quicker than standard open ball bearings that other hubs (namely 9mm) tend to have?
And yes - I am converting, but I'm not converting hubs... I just bought a new wheel all together that has a 20mm hub, whereas the fork I just purchased is also 20mm QR thru axle.
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