Mechanics and Fixing Any Questions Answered

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  • A bent steerer tube maybe

  • can you tell how far the previous stem was inserted? That steerer tube is super short so it might tell you what the maximum is and presumably that much is safe as it had been ridden like that before?

  • I’d take it out and see if the stems will fit into the for without the headset. It’s at least a start to narrow down what is out of spec/damaged.

  • @yak I had a bike with a super short head tube and had a similar issue. Couldn’t find a bike shop to ream out the steerer tube but a machine shop did do it for me.

    Other suggestions are good, also why cant you use the original stem, are the new bars 31.8? If the old stem is 26.0 and your new bars 25.4 can just use a coke can shim

  • Likely that the tube in the fork was only reamed out enough for the stem it came with. I’ve encountered that with seat tubes in the past.

    You can check by cleaning the inside of the tube and looking for an edge or running a flat head screw driver up the inside and trying to feel for a difference. Just be aware that it will be a tiny difference, like 0.2mm sort of thing.

  • Likely that the tube in the fork was only reamed out enough for the stem it came with.

    @yak, more likely - in my opinion - is that you're hitting the butt in the steerer tube. They are heavier walled at the bottom to provide more strength where the crown attaches. The extra wall thickness can't go on the outside as a constant od is required so it goes on the inside. The headtube looks very short so consequently you don't have much of the thinner walled section of steerer into which to insert a stem.

    Depending on the steerer used the difference in internal diameter could be as much as a couple mm.

    I would not recommend reaming the steerer to remove the extra wall thickness.

    Instead, I would figure out how much stem you can get in before it binds and ensure that you always have as much of that depth used as possible.

    I'd probably also say you don't want to have the stem extend out of teh steerer by more than say, 50% of the length you can insert into the steerer. Ie, if you can get 100mm of quill into the steerer then you don't want a total quill length of anything over 150mm. That make sense?

    You may need to cut down the quill on the new stem but you need to get the angle right and do it neatly and you may also need to trim the bolt or replace it depending on how much of it is threaded.

  • Thanks all, that's very useful advice. Will have a go at removing the fork this morning for closer inspection. If I understand @M_V's post correctly then it's likely nothing wrong with the fork, and I just need a shorter stem (or cut down the one I currently have). Definitely prefer that idea to needing to ream it or buy a new fork!

    also why cant you use the original stem, are the new bars 31.8? If the old stem is 26.0 and your new bars 25.4 can just use a coke can shim

    The bars are 25.4 so I can use a shim, but it would set the bars too low as it's not a riser stem ("drop stem"? Dunno what the word is), and my partner prefers an upright position. But I'm considering whether its easiest/safest overall to keep the OG stem and look for bars with enough rise to compensate, if they exist.

  • Oh god yeah I didn’t notice how small that head tube is. I’d agree in that case

  • Anyone help with this gearing issue? The cable stop before the derailleur is as pictured below, but there's no way the cable outer will fit into that hole. Can you get thinner cable outer and ferrules so it'll go in? Or will I have to be really nifty/careful with a drill to open up the stop a bit? Cheers.

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  • Probably takes a stepped ferrule.

  • Wonderful. Another part I never knew existed.

    That's the renovation on hold for a few days then...


  • Is it a bell housing?
    If so, use a ‘stepped’ ferrule, like one of these
    Thin end goes into the guide and let’s the cable through while the thick end accommodates the cable outer

    Too slowwewwwwwww

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  • Update: plucked up the courage to take the forks off, fortunately the headset has caged bearings so that made it a lot less stressful. Checked it against a straight edge and nothing's bent. I found another 25.4 stem I'd forgot I had, which luckily went in past the min insertion point, so the bike is at least safe to ride and I didn't have to worry about shimming the bars. Interestingly, each of the four stems I tried went in by different amounts, between 52mm and 67mm. So I guess that means that where the steerer tube walls get thicker, different stems fit further down depending on their actual diameter, which I guess differs slightly and isn't exactly 22.2mm on any of them? Anyway. Cheers all, think I can at least rest assured that the fork probably isn't fucked!

  • Now, why don't I have one of those right here?

    Got one on order. Until then, I guess I can install the brakes and cable up the front mech.

  • Got one on order

    One? Never get just one if you have to order

  • Your local LBS should have some.

    Pop by Brixton Cycles if you are local and we have them for a couple of quid.

  • My local LBS (Rat Race Cycles) will almost certainly have some, so I can nip round tomorrow and get one. Then have the one being delivered later this week as a spare. If they don't have any, I'll call in at Brixton Cycles instead. Cheers.

  • Master cylinder failure. Buy a LH or RH sram hy'rd kit from anywhere that has one, they are less than £20 rrp, you don't need the metal plate thing, only the piston top and spring, o rings etc in the kit.
    Fairly simple to replace, follow the numerous youtube videos, think SRAM have a proper guide as well.

    Happens to a lot of them. Perfect bleed, gentle braking and it kinda works OK, but as you pull master harder it just goes to the bars, no leaks, no loose stuff, no seized pistons etc. Almost 100% this will be your issue.
    I'm a shop and I charge £20-25 labour to fix bleed and test ride.

    YOu cannot buy it from sram, its not an ISO size. Do not loose it Dab it in grease and work in a clean area.
    I've lost one before, utter ball ache.

  • DO

    How do you remove it then?

  • I've got a BSA BB (24mm axle), and need to put a drive side spacer in as I've got some strange rubbing noises. Do I put something on the thread side or the crank side of the bearing?

  • What crank? Modern cranks (Hollowtech ii etc.) won't tighten properly if you put in more spacers than they were designed for.
    Did you measure the BB width? Can you find where the rubbing is coming from?

  • It's a Chinese crankset (Magene). It's all tight but I think the chainrings (single spider-mounted unit) are just too narrow and set inwards. I've read some people buying a new set of rings and a spider and fixing the issue but I'd rather spend a few euros to move it out 2-3mm to see if it improves

    Definitely there's a rub due to chain angle when it's in the big ring and small cog and I'm hoping the odd cracking/pinging noise will also be fixed it I can sort the chainline.

  • Both will work, provided there's still enough clamping force to hold the two parts of the cranks together, but given the choice I'd go for a spacer between the BB shell and the DS BB bearing.

  • Just realised I can't actually pop by Brixton Cycles as the bike I would normally use to get there is currently being worked on (by me). LBS didn't have any stepped ferrules, so gonna have to wait until the one I ordered arrives before finishing off the build.

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Mechanics and Fixing Any Questions Answered

Posted by Avatar for OmarLittle @OmarLittle