Forum home Road cycling forum Workshop

Re hooping 20 spokes

JoshthemuleJoshthemule Posts: 7
edited November 2017 in Workshop
So, I’ve got some Mavic wheels that came on my used bike. I want some wider wheels to accommodate 25mm tires. So, I’ve purchased some Easton rims that match up and I’ll start the build in a couple weeks. The Mavics have straight pull blades and I’ll be using straight pull 14 gauge Sapim, round.

Anyone do this before?

I’ve built 32 spoke MTB wheels and they came out great

Posts

  • 964cup964cup Posts: 1,359
    If you're using straight pull you need to be absolutely sure that the drilling in the new rims is the same as the old ones (spacing and offset), since SP spokes can't pivot at the hub. Be aware also that some Mavic wheels have proprietary spoke retention systems at the hub end, so you need to be sure your Sapim replacements will fit. Getting the length right for SP spokes is also more complicated than for regular J-bend.

    No idea why you think you need wider rims for a 25c tyre, but whatever floats your boat, I suppose.
  • What got this going is the annoying effort to take my wheels on and off because the brakes don’t open enough with the little cam lever to get around the tire. I set them correctly so the brake response is immediate.

    I have the spec sheet for my wheels so I’m fairly confident I have the right spokes. The ERDs are different but I just subtracted the difference from the current spoke length instead of using a calculator.

    I can’t find published hub dimensions for these wheels and I don’t know how to measure a straight pull hub but the spec sheet lists the spoke length so it should be easy math with two different ERDs.

    Both rims are zero offset and 20 spokes. I don’t know what you mean by spacing other than the spoke holes are evenly distributed around the rim.

    I’m mostly concerned about the round spokes being as strong as the flat blade spokes.

    If it doesn’t work, I can just reassemble the original rims. Also I’m doing it because I like working in my bike and building stuff as much as I like riding.
  • 964cup964cup Posts: 1,359
    I'd be surprised if the original Mavic rear isn't offset-drilled. Be careful about the ERD as it accounts for the nipple, and Mavic nipples are also non-standard (or can be). Be careful about the maths, too; this is a good read: https://www.sheldonbrown.com/spoke-length.html. 20h is a very low spoke count for a rear wheel; Mavic will have based their strength calculations on the tension sustainable with their (probably proprietary) bladed spokes. You will want to be sure that your chosen round spokes *and* the spoke bed in the rim *and* your selected nipples can take the same tension.
  • Exactly. That’s what I’m worried about.

    The spokes came with aluminum nipples but I think I’ll at least need brass. As for spoke tension, that’s probably my biggest concern.

    Thu are 2008 Aksiums and as far as I can tell without taking them apart and lokkkng at the spec sheet, they look to be pretty standard nipples.

    I did buy a tension meter so I can be a bit more precise than plucking a harp.

    I’m hoping I can see problems as they arise in the build and not find them at 40mph 50 miles from home
  • rolf_frolf_f Posts: 15,959
    Hmmm, small spoke count Mavic re-rimming with round straight pull spokes - what could possibly go wrong?!

    Seriously - I would ask Ugo's opinion on this. Apart from everything else mentioned, how are you going to stop the spokes from spinning? I think you've gone straight from the easiest wheel to build to the hardest. Why not just get a pair of sensible hubs for j spokes - they'd probably cost a lot less than you can sell the complete Mavics for.
    Faster than a tent.......
  • I’m not totally against that. Sometimes I have to have parts in my hand to know what questions to ask. I didn’t inspect my Mavic rims and found re-enforcement around the eyelets. I can’t find any strength ratings for my new rims. I did some research and know I need stronger spokes

    One thing I’m having difficulty with is conversion. Mavic specs the spoke tension in KG. Spain rates spokes at N/mm2. One is a pull force and another is a tension meter reading I suspect.

    I think I’ll return them. It just seems that too much can go wrong.
  • beanstalkbeanstalk Posts: 143
    The Mavics have straight pull blades and I’ll be using straight pull 14 gauge Sapim, round.
    How does one stop round straight pull spokes from full length rotating?
    J-bend spokes are rotational fixed at the hub, for bladed spokes you have slotted spoke holders but round straight spokes...
  • 964cup964cup Posts: 1,359
    I'm running with this because it's interesting. Anyway:

    I assume s/he's thinking of using Sapim D-Light, which are 1.65mm (near as dammit 14 gauge) in the centre. That's 2.138mm2. So the spoke would fail in the centre at 2929N, which is 298.7KGf, or more than twice the maximum build tension (122KGf for Easton R90SL, for instance). I use D-Light a lot, they're excellent spokes (granted, I've never used the SP version). Anyway, spokes usually fail at the nipple or the head, not in the centre, because that's where the stress risers are (that's one of the arguments for SP spokes - less fatigue and stress at the head, because no bend).

    You stop round spokes rotating by holding them with pliers. Same principle as stopping wind-up in Lasers. Slows the build down somewhat.

    For the record, I think the OP would be far better off buying some half-decent hubs (in a 20/24 minimum, without knowing his/her weight) and some ordinary J-bend spokes, and building up new wheels that way.
  • beanstalkbeanstalk Posts: 143
    964cup wrote:
    You stop round spokes rotating by holding them with pliers.
    Pliers is what I thought and strictly avoid.
    964cup wrote:
    Same principle as stopping wind-up in Lasers. Slows the build down somewhat.
    Visualising the wind-up with bits of adhesive tape on the spoke is my principle.
    Then you can clearly differentiate between wind-up and pull and take out the wind-up after every tensioning by turning the key back.
  • 964cup964cup Posts: 1,359
    beanstalk wrote:
    964cup wrote:
    You stop round spokes rotating by holding them with pliers.
    Pliers is what I thought and strictly avoid.
    Pliers is what Sapim recommend. I tend not to use Lasers, but have some pliers with leather-faced jaws to avoid marking the spokes. The usual principle of over-turn and back off a quarter-turn or so applies. You wouldn't use Lasers drive-side anyway, so tensions aren't super-high. Brass nipples and lube the nipple seat.
  • I love this. I’m obviously an amateur that is over simplifying a process that has many more considerations than I knew. And here I have some real experts chiming in.

    So the whole point was to save a little dough and also get to do a fun project. Back to the drawing board.

    Thanks so much for the input fellas. And it’s “He”
  • beanstalkbeanstalk Posts: 143
    Why don't you get bladed spokes? They are easy to hold.
  • 964cup964cup Posts: 1,359
    It's *really* hard to build cheap wheels cost-effectively. When Shimano can sell RS010s for less than £100 a pair, there's no way to compete. I think the crossover point is about £3-400 in retail parts cost; at that point you can start to build something that's better - or more closely focused to your needs - than the market offers factory-made. E.g. Ryde Pulse Sprint rims in 20/24 on Novatec F291/482 using D-Lights. <1350g, tubeless-ready, wide rim, about £300 of parts. You could get quite close to 1300g using Lasers except for the driveside. Assumes rider weight < (say) 80kg and not necessarily ideal for winter use as the rim sidewall is relatively thin to get the weight down, but then other rim options are available.
  • So, rethinking my approach.

    I don’t have any problems with the front. 20 spokes and even tension will make it easier. I’ll get to use my hub and the spokes I’ve ordered.

    On the rear, exchange my R90 rim for the same model 28 spoke and purchase a new rear hub.

    Easier build and won’t require as much tention on the drove side.

    And I still get to build it.
  • rolf_frolf_f Posts: 15,959
    964cup wrote:
    It's *really* hard to build cheap wheels cost-effectively. When Shimano can sell RS010s for less than £100 a pair, there's no way to compete. I think the crossover point is about £3-400 in retail parts cost; at that point you can start to build something that's better - or more closely focused to your needs - than the market offers factory-made. E.g. Ryde Pulse Sprint rims in 20/24 on Novatec F291/482 using D-Lights. <1350g, tubeless-ready, wide rim, about £300 of parts. You could get quite close to 1300g using Lasers except for the driveside. Assumes rider weight < (say) 80kg and not necessarily ideal for winter use as the rim sidewall is relatively thin to get the weight down, but then other rim options are available.

    I did that for about £200. Worked out well enough as long as you treat them like Gremlins and don't get them wet!
    Faster than a tent.......
Sign In or Register to comment.