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BOOST axle chainline

bobbydigitalbobbydigital Posts: 252
edited July 2019 in MTB workshop & tech
I see a lot of wheels claim that they are BOOST, 148 in my case, but in reality the hubs are standard and they (Mavic) just put spacers on the end of the axle, which seems to defeat the purpose of boost, which I thought was wider hub.


Anyway I was wondering, wouldn't that chainline suffer if you used a 135 spaced hub with 142/148 spacers.


I know they do brake disc spacers for the boost conversion but without the wider hub, what are you gaining?
What kind of spacer would you need for the cassette? The freehub will be further away from the chainstay on a 135hub.

Posts

  • tom_howardtom_howard Posts: 792
    148mm is Boost, there aren't any other sizes. (157mm Superboost is available, but looks like thats dying off) anything with a spacer isn't a boost hub

    You can't just put spacers at the end of the axle, you need to space the rotor differently too, as well as possibly re dishing the wheel, depending on which mount you use.

    Using the spacers doesn't give any advantage, other than it means you can put old wheels in a new, boost frame.

    no spacer for the cassette, it stays in the same position, hence the redishing the wheel and having all the spacers on the non drive side. though, you may need the boost offset (6mm) chainring, again, dependant on your frame/which kit you use
    Santa Cruz 5010C
    Deviate Guide
    Specialized Sequoia Elite
    Pivot Mach 429SL
    Trek Madone 5.2 Di2
    Salsa Mukluk Carbon
    Specialized Turbo Levo Expert 29er
  • bobbydigitalbobbydigital Posts: 252
    That isn't how Mavic sale them, which is why I asked for the chain line spacing.

    I bought a wheel said to be 148 from wiggle, it is actually 135 axle with 2 yellow spacers, I didn't know this at the time of buying it and it's not what I wanted.

    It has 2 spacers, which add 6.5mm to each axle, there is no option to run a single spacer on the brake disc side.
    Seems like bad marketing.

    I thought maybe people had some solution but with the 6.5mm on each side, it means the freehub is miles away and the chainline would probably be 45mm on my bike.

    qv5Dpre.jpg
  • tom_howardtom_howard Posts: 792
    Got a link? Just sticking spacers at each end of the axle won’t work.

    Edit, seen your pic, with no spacers, hows the brake rotor/caliper fitment?

    Thinking aloud, is the rotor mount on the hub removable? So they could use the same shell across the whole range?

    I guess how they’ve done it could work, just doesn’t seem to be the most efficient use of the extra space. If it’s any consolation, I can’t tell the difference between my boost and non boost wheels, and I’d be amazed if anyone else could irl
    Santa Cruz 5010C
    Deviate Guide
    Specialized Sequoia Elite
    Pivot Mach 429SL
    Trek Madone 5.2 Di2
    Salsa Mukluk Carbon
    Specialized Turbo Levo Expert 29er
  • bobbydigitalbobbydigital Posts: 252
    Without the spacers the wheel would slide around on the axle.

    I think the mavic hubs are 2 parts, they press them together & I think it is the brake side that is removable.

    I have i40 scraper rims to use but this rim was pretty cheap in the sale and I thought 148 for £70 seemed like a bargain, there's always returns, was a long time ago I bought but might still be returnable.
  • tom_howardtom_howard Posts: 792
    Sorry, I meant spacers for the rotor.

    I’d return it, then get what you want.
    Santa Cruz 5010C
    Deviate Guide
    Specialized Sequoia Elite
    Pivot Mach 429SL
    Trek Madone 5.2 Di2
    Salsa Mukluk Carbon
    Specialized Turbo Levo Expert 29er
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