Titanium Road & Gravel Bike...Wheel/Tire Question
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  1. #1
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    Titanium Road & Gravel Bike...Wheel/Tire Question

    I'm in the process of ordering a new Ti framed bike, with versatility as a goal. For a few reasons I've decided to purchase an Alchemy, either the Ronin Ti, or the Chiron (Ti). I'll be doing a lot of asphalt bikepacking (typical load: about 8-10lbs of pack weight), and some gravel riding. I'm not interested in MTB type terrain, as I would use my MTB for that. I've ordered the Ronin Ti with 32 Conti GP5000 tubeless, and was planning on a second 650wheelset, with maybe 45mm tires. The Chiron is described as more of a cyclocross bike, and has a max allowance for 38mm tires.

    Aside from any personal experience advice, I'm curious as to what the maximum recommended tire width on a 650c wheel might be for the Chiron. Would it still be 38mm as specified for a 700c setup, or is the restriction based on overall wheel/tire height, and not so much on width, allowing for a bigger tire? (I wasn't able to get a clear answer from Alchemy)

    https://alchemybicycles.com/product/ronin-ti/
    https://alchemybicycles.com/product/chiron-carbon/

    Thanks, Roy
    Last edited by rfield54; 2 Weeks Ago at 10:55 AM.

  2. #2
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    (...give or take, a 47mm x 650b tire has the same outside diameter as a 28mm x 700c wheelset)

  3. #3
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    Quote Originally Posted by rfield54 View Post
    I'm in the process of ordering a new Ti framed bike, with versatility as a goal. For a few reasons I've decided to purchase an Alchemy, either the Ronin Ti, or the Chiron (Ti). I'll be doing a lot of asphalt bikepacking (typical load: about 8-10lbs of pack weight), and some gravel riding. I'm not interested in MTB type terrain, as I would use my MTB for that. I've ordered the Ronin Ti with 32 Conti GP5000 tubeless, and was planning on a second 650wheelset, with maybe 45mm tires. The Chiron is described as more of a cyclocross bike, and has a max allowance for 38mm tires.

    Aside from any personal experience advice, I'm curious as to what the maximum recommended tire width on a 650c wheel might be for the Chiron. Would it still be 38mm as specified for a 700c setup, or is the restriction based on overall wheel/tire height, and not so much on width, allowing for a bigger tire? (I wasn't able to get a clear answer from Alchemy)

    https://alchemybicycles.com/product/ronin-ti/
    https://alchemybicycles.com/product/chiron-carbon/

    Thanks, Roy
    You need to get that answer on width. As noted, a 650b at 47 mm is about the same outer diameter as the 700c. But it is more often that width is the limiter, either based on the fork or the spacing of the chain stays at the bottom bracket. Unlikely that seat stay spacing at the brake bridge would be the issue. They should be able to tell you the spacing between the chain stays at the BB and the spacing of the fork.

  4. #4
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    Quote Originally Posted by Kerry Irons View Post
    But it is more often that width is the limiter, either based on the fork or the spacing of the chain stays at the bottom bracket. Unlikely that seat stay spacing at the brake bridge would be the issue
    Good info...thanks Kerry

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    Really hard to generalize. Since the stays widen as you move toward the hub, the smaller diameter 650b wheels will allow you to use wider tires than the 700c spec.

    One example is that my Jamis Renegade max tire widths are 700c x 40 and 650b x 48.

    I assume the difference in your case would be similar.
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  6. #6
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    These are definitely questions you should have answered by the frame builder.

    My steel gravel bike takes 40mm tires in the rear and if I used 650B wheels I do not think that would change at all. The stays are straight for quite some distance before they start to flare out closer to the hub. So I wouldn't assume anything.

  7. #7
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    Thanks for the replies. I'm going in to Alchemy this Friday to have some measurements taken for a custom Ronin Ti, and with that info and my Retul report from a few years ago, I should be a happy camper in the near future.

  8. #8
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    Quote Originally Posted by Jay Strongbow View Post
    These are definitely questions you should have answered by the frame builder.

    My steel gravel bike takes 40mm tires in the rear and if I used 650B wheels I do not think that would change at all. The stays are straight for quite some distance before they start to flare out closer to the hub. So I wouldn't assume anything.
    Point well taken.
    "COMPLACENCY IS LETHAL - VOTE in November." - System Shock.

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    bicycles in particular, you need to separate between what's merely true and what's important."
    -- DCGriz, RBR.





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