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Fulcrum Bearings

pippi_langsamer-2pippi_langsamer-2 Posts: 1,400
edited September 2018 in Workshop
Having got the WinterBint down from the garage hanger in preparation for erm….the Winter, I noticed the front wheel bearings were shot (Fulcrum 777 discs on my Attain GTC Pro Disc).

So, stripped the axle n bearing out and proceeded to order some replacement 61903-2RS bearings from a bearing supplier (note, not Fulcrum specific bearings from a bike shop).

The bearings I received from the shop are marked as 6903-RS, although I believe that despite their slightly different product code, they are supposed to be the same bearings.

However, when I have installed the bearings, the axle will not pass thru the new bearings as it seems the ID of the new bearings is slightly smaller.

Just wondering whether this is some kind of tolerance issue, or are the two bearing codes actually different bearings despite what the interwab reports?

Any other bearing experts out there any advice?

(Incidentally, I spoke to the (helpful), bearing supplier, and returned the two new bearings along with one of the old bearings in the hope they could measure the ID of both and compare as I don’t have any calipers to check. Unfortunately, I fear they may have got lost in the post as 6 days later, they still haven’t received them!)
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  • cooldadcooldad Posts: 32,601
    They are the same dimensions.

    Where did you get the specs from before you ordered?
    I don't do smileys.

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  • drlodgedrlodge Posts: 4,825
    Inside diameter of those bearings is 17mm, what's the width of the axle? They might be the right size but are designed to be an interference fit.
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  • cooldad wrote:
    They are the same dimensions.

    Where did you get the specs from before you ordered?

    I took the spec' directly off the worn bearings (stamp), and searched suppliers for said spec. All suppliers stated same thing- 61903-2RS are same-same 6903-RS, so I ordered these:

    https://www.bearingboys.co.uk/Thin-Section--Dunlop--SKF/619032RS-Dunlop-Sealed-Thin-Section-Ball-Bearing-2123-p
  • cooldad wrote:
    They are the same dimensions.

    Where did you get the specs from before you ordered?

    I took the spec' directly off the worn bearings (stamp), and searched suppliers for said spec. All suppliers stated same thing- 61903-2RS are same-same 6903-RS, so I ordered these:

    https://www.bearingboys.co.uk/Thin-Section--Dunlop--SKF/619032RS-Dunlop-Sealed-Thin-Section-Ball-Bearing-2123-p

    (I also checked the Fulcrum tech docs for correct bearing code)
  • Ben6899Ben6899 Posts: 8,599
    6903-2RS and 6903-RS are the same dimensions. I have just fitted new 6903-RS bearings to a front Fulcrum Racing Quattro (17mm axle diameter).
    Ben

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  • drlodgedrlodge Posts: 4,825
    Only one way to resolve it, is to measure the axle (17mm) and the inside dia of the bearings you have. A micrometre would be useful.
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  • drlodge wrote:
    Only one way to resolve it, is to measure the axle (17mm) and the inside dia of the bearings you have. A micrometre would be useful.

    Or even a vernier caliper :)
  • drlodgedrlodge Posts: 4,825
    Or even a vernier caliper :)

    That's the chappy.

    mapra-q1-digital-caliper-0-150-ip67.jpg
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  • drlodge wrote:
    Only one way to resolve it, is to measure the axle (17mm) and the inside dia of the bearings you have. A micrometre would be useful.

    Yes, it would be useful. However, I don;t have one, hence me sending the things to the suppliers to measure for me (the bearings- not the axle).

    Anyway, looks like the whole bastid lot have gotten lost in the post now :twisted:
  • lesfirthlesfirth Posts: 1,149
    IMHO the bearings are the right size and just need a bit of gentle persuasion to go on your axle.
  • lesfirth wrote:
    IMHO the bearings are the right size and just need a bit of gentle persuasion to go on your axle.

    :)

    i suspect this is the case.
  • keef66keef66 Posts: 13,123
    Sounds very odd.
    Did the old, now lost in the post, bearings just slide off the axle easily or was bashing involved?
    Is the axle spotlessly clean and corrosion free?

    Wouldn't have thought they are meant to be an interference fit; everything you ever read about bearing installation tells you not to apply force to the inner race...
  • Mad_MalxMad_Malx Posts: 4,226
    Different wheels, but
    https://singletrackworld.com/forum/topi ... -bearings/

    6903 come in 18mm ID also.
  • cooldadcooldad Posts: 32,601
    Mad_Malx wrote:
    Different wheels, but
    https://singletrackworld.com/forum/topi ... -bearings/

    6903 come in 18mm ID also.
    No, those are MR18307.
    I don't do smileys.

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  • Mad_MalxMad_Malx Posts: 4,226
    ^I'll rephrase - several vendors sell things labelled as 6903 that have 18mm ID

    Edit: I might even still have mine that I can post, but I've fitted and extracted them once.
    I bought these in opposite error to the OP, then found they were too big.
  • Mad_MalxMad_Malx Posts: 4,226
    And just to confuse things further-
    https://www.kineticbikebearings.com/608-2rs-615.html

    I know there is a standard, but unfortunately it appears it isn't always followed.

    You need a caliper.
  • lesfirthlesfirth Posts: 1,149
    keef66 wrote:
    Sounds very odd.
    Did the old, now lost in the post, bearings just slide off the axle easily or was bashing involved?
    Is the axle spotlessly clean and corrosion free?

    Wouldn't have thought they are meant to be an interference fit; everything you ever read about bearing installation tells you not to apply force to the inner race...

    I agree "bashing" bearings is not of a good idea. I have not suggested that the bearings need bashing or are an interference fit.

    All this about measuring the bearings is a complete distraction. Assuming the new bearings are not wrongly marked imperial size, they are either correct, obviously too small or so big that they are flopping about on the axle. 1mm is not as the OP says "slightly smaller", it is obviously too small.He does not need a vernier caliper ( or being pedantic a "digital caliper" as shown above) to see if the bearing is 1mm too small.
  • The new bearings will never go on the axle- not without considerable force with a hammer anyway, and I suspect they'd then be stuck!

    The old ones slid off perfectly and the fit was spot on. Axle is corrosion free too.

    I can't fathom it, other than the inside diameter of the new bearings is <17mm.

    It's not like they were cheap cheap bearings too, so I'd expect tolerances to be OK
  • cooldadcooldad Posts: 32,601
    Have you measured the axle?
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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  • cooldad wrote:
    Have you measured the axle?

    In the absence of calipers, no.

    Given they're a lot cheaper than I thought, I might invest in some though
  • thats why i always measure so that i order whats needed not what some cocksplash bike mfr labels it as.

    I remember thinking what would i ever use one of those verniers for but its used quite regularly. Ive got a mechanical one and had to re learn how to read it lololol
  • Calipers ordered FFS :roll:
  • keef66keef66 Posts: 13,123
    I remember thinking what would i ever use one of those verniers for but its used quite regularly. Ive got a mechanical one and had to re learn how to read it lololol

    I got a digital one so I didn't have to relearn all that, and nice big numbers for my failing eyesight.

    Then I bought a micrometer to measure brake discs on the cars, and have to spend half an hour reading the instructions every time I use it... :roll:
  • keef66 wrote:
    I remember thinking what would i ever use one of those verniers for but its used quite regularly. Ive got a mechanical one and had to re learn how to read it lololol

    I got a digital one so I didn't have to relearn all that, and nice big numbers for my failing eyesight.

    Then I bought a micrometer to measure brake discs on the cars, and have to spend half an hour reading the instructions every time I use it... :roll:


    Joking apart, i struggle to read it unless the light is good and i have my glasses on. I might buy a digital one :(

    i thought when i spent £150 on it that it would outlast me if i looked after it and it appears it has.
  • Mad_MalxMad_Malx Posts: 4,226
    £12 or so from Lidl does me fine for the difference between 17 and 18 mm, seatposts, bolt sizes....
  • Yup, ordered me one of these:

    http://amzn.eu/d/hobqwfU
  • Sooooo….having received my shiny new digital calipers (very nice btw- very nicely made and a lot better quality than I expected for £15), I measured the OLD Fulcrum bearing and axle. Seems there’s a reason why the new bearings I ordered didn’t fit the axle.

    https://photos.app.goo.gl/n1y9QYQXK4TEHbAP9

    The picture of the bearing close-up isn’t very good, but it’s 61903-2RS, which….as all bearing manufacturers sites state, has an ID of 17mm.

    http://www.wychbearings.co.uk/61903-2rs_budget.html

    So, why is the ID of the bearing coming up closer to 18mm?
  • drlodgedrlodge Posts: 4,825
    Check this page out! https://www.kineticbikebearings.com/608-2rs-615.html

    18307-2RS (MR30187, 61903)

    THIS BEARING IS 1mm DIFFERENT FROM 6903-2RS AND USED IN MANY HUBS. THE ORIGINAL BEARING QUITE OFTEN HAS 61903 ON THE SEAL - CHECK YOUR INTERNAL DIA, THIS HAS 18MM (61903 CAN ALSO BE 19MM INTERNAL DIA WHICH IS 6903)
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  • drlodgedrlodge Posts: 4,825
    And an identical tale to yours here. https://singletrackworld.com/forum/topi ... -bearings/
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  • Mad_MalxMad_Malx Posts: 4,226
    8)
    There's an echo in here
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