I am a frame builder AMA

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  • Does anyone know how lugs and fork crowns etc were pantographed back in the day? Were they cut or cast?

  • Bit of both,I think. Big manufacturers could afford to pay for custom moulds, smaller ones had them engraved. Technically, of course, using a pantograph would involve engraving. Pretty sure all the Roberts ones were machined not cast.

  • Using a pantograph mill

  • Im trying to build my mate a rad bike. Cue seeing a rad semi lo pro type thing on ebay with ridic tight clearances at rear. Takes 23mm clincher comfortably but would ideally like to put 25mm tyres on it.
    Thought of a few options -

    • File out the dropout to push the wheel back like in the attached photo. Would this be safe?
    • Ask someone to braze 3/4mm to the bottom of the dropout to make the frame sit higher on the wheel.
    • Get someone to braze new track dropouts.

    I have done many a bodge before with a file so pretty competent.

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  • I’d think if you file the dropout like that then the wheel will just move forward when you pedal. Not much for it to be grabbing onto.

    Plus filing it by enough to make any significant difference at the tyre will likely weaken it.

    If I was set on fitting bigger tyres in a frame then I’d be looking at dimpling the stays. If the bridges are an issue then either remove them or get someone to relocate them for you.

  • What's wrong with 23s? I've ridden them most of my life and the worst that has happened is that I got old. If you can feel much difference between 23 and 25 you're a better man than me, which isn't that difficult.

  • Thanks for the above pointers @M_V

    @Colin_the_Bald Yeah 23's will actually be alright. Was getting a bit too ahead of myself ha.

    Im on the lookout for what I believe are called top mount downtube shifter, any builders seen some for sale online anywhere? going to do some research and ping off a few emails later but in the meantime thought I would ask here.

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  • Like this?


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  • Yesss. I knew I'd seen it before. Thank you.

  • One more question, when does a frame loose its originality from being repaired? More than one tube?
    I know that unless the same framebuilder done the work it wouldn't be 100% original but hope you get what I mean. Pretty sure I'm over thinking it ha..

  • I’m currently “repairing” this Bridgestone.

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  • Philstone has a good ring to it tbh

  • Or Dastone

  • I’m not sure which thread this question should go in but I’ll try here.
    In this video

    they briefly discuss bb height and how it affects ‘ride feel’. At 21:00.
    I was interested to hear the idea that a bike with a higher bottom bracket climbs better.
    I’ve personally always preferred a low bb for just the reason he mentions, more planted feel when descending. But I live in a hilly part of the country and as I’m getting older the climbs are feeling harder.
    Can anyone chip in with this? Any experience with this?

  • I’ve personally always preferred a low bb.

    Same here, although it's probably more psychology than physics from what I have read. Interestingly a lot of frame builders spec lower BBs than you'll find on OTP bikes, so there must be something in it though.
    I can't comment on the higher BB climbing better, but 63mm for their gravel bike sounds super high to me once you take into account the fatter rubber...

  • I’m really not a fan of low bbs. It seems to me like the draw backs of a low bb are more difficult to live with than those posed by a high bb.

    Two of the frames I have built have pretty high bottom brackets and the only time I notice it is getting on and off.

    Conversely I’ve ridden bikes with low bottom brackets before and suffered pedal strike when cornering and climbing technical terrain and hated it.

    I always admit that I am not a particularly ‘refined‘ rider so might be so atuned to handling intricacies but my gravel fixed has a 12 ½” bb height and the mtb has bb rise instead of drop (not currently built up so not entirely sure of height) and I really feel they both handle just fine.

  • I've got a commision for a frame, pretty open brief in terms of construction so I fancy doing it lugged.

    Chances of me combining a bb lug, track spacing/chainline and clearance for 38c tyres?

  • Think I’d use the same bb shell as I did in this frame which, with straight stays clears a 25 no bother, think a 28 would fit in there too.

    So, curved stays (will that even work with the chainstay port angle?) or dimpled straight stays to get to 38?

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  • How feasible is it to convert a steel frame with vertical dropouts to horizontal dropouts/track ends? My old single speed dekerf definitely started out life with horizontal dropouts and Im thinking of buying a vintage steel MTB frame and converting it to SS in a similar fashion

  • Definitely doable. Things like the size of the current dropouts and how much length they leave on the stays after being removed will dictate how difficult it will be

    Have you considered sliders?

  • Thanks @PhilDAS glad to know its doable
    Sliders are definitely a possibility and probably more useful than track ends.

  • The problem I could see with retrofitting sliders is the axle position relative to the frame. I think it would hold the wheel lower and therefore lift your BB and steepen your frame angles.
    Someone more experienced would be better able to give advice on feasibility

  • It turns out that on my new not-quite-finished-but-nearly-there gravel bike frame I have zero or slightly negative clearance between the chainstays and the crank arms. The chainstays will need a wee dimple for chainring clearance, and I'm good with that. However, while my head says to just dimple the chainstays on both sides to allow crank arm clearance, my heart says that's a bodge and I should cut out the chainstays and fit new ones which have sufficient clearance.

    Anyone who wants to tell my head that it's right and to tell my heart that it should stick to pumping blood and keep out of framebuilding dilemmas is welcome to say so. Contrary views also grudgingly welcome.

  • Cut out clearance and braze in a curved piece in the cut out section?

    Like this but on the outside

  • Could do. Hadn't thought of that, I confess, but my initial reaction is a no on the basis that:

    1. I'm only looking for about 5mm extra clearance, max.
    2. I'm hoping that a subtle dimple won't be too noticeable whereas that option definitely would be. Although possibly in a 'played for and got' way rather than an 'Oooops, spot the fuck up' way.
    3. It'd involve more work. I need to make a dimpling tool anyway, so I might as well make a dimpling insert which will squish the chainstays slightly for crank arm clearance.
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I am a frame builder AMA

Posted by Avatar for coldharbour @coldharbour