• This topic has 28 replies, 8 voices, and was last updated 8 years ago by DT78.
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  • Dumb wheel build question – dishing
  • DT78
    Free Member

    I’m planning on rebuilding my LB wheel – I’ve never been able to get the dish right as well as the right tension. If I tension it correctly the tyre rubs on the stay. This is making me think I have used slightly the wrong length spokes. I used the quoted ERD but I think it was slightly out (others have said this too lesson learnt not to order spokes before actually measuring the rim)

    I rebuilt the front with 2mm longer spokes on one side and it is now perfect.

    The rear is built with 286 (which is what the spoke calc said to use) both sides. I have enough spare 288s to replace one side.

    If tension etc is the issue should I actually buy 2mm shorter spokes for the drive side to bring it back to dish rather than use the longer spokes on the NDS.

    Does this rambling make sense?

    Other option is do it properly completely disassemble and measure ERD rather than just spoke swap 16 spokes. That will take me a bit of time.

    neilthewheel
    Full Member

    Getting the dishing right means slackening all the spokes on one side and tightening all the spokes on the other side. If the rim is too far to the drive side, tighten the non-drive spokes.
    I usually do the slackening first, going right round the wheel, then tighten the opposite side.
    You really need a dishing gauge to show you how far in to pull the rim to get it centred.
    Not sure what you mean by

    If I tension it correctly the tyre rubs on the stay

    . How do you define “tensioned correctly?”

    matthew_h
    Free Member

    Tension on a dished wheel (with an asymmetric hub) will always be different side to side. It’s a geometry thing.

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    isitaboutabicycle
    Free Member

    What do you mean by ‘tension it correctly’? The rim should be centred on the hub – you can easily check this to reasonable accuracy by putting it in the dropouts backwards and seeing if the rim is in a different place, if you don’t have a tool. The drive side spokes should be quite a lot tighter than the non-drive, and you should have quite a lot of leeway in spoke lengths to dish a wheel correctly.

    isitaboutabicycle
    Free Member

    Oops

    DT78
    Free Member

    Bit more detail

    Have a dishing tool and a park tools tension thingy.

    I’ve been trying to match the tensions to the factory wheel, so yep higher on drvie than non drive by ‘5’. If I do that, getting it perfectly true radially it is well out of dish. There isn’t much clearance (scale 2.25 Ralph) and it rubs on the NDS.

    So, if I loosen off the rubbing side and dish the wheel to the centre correctly the NDS spoke tensions are super low (between 5 – 10 rather than 15 I want), and it means the wheel flexes under heavy cornering

    This makes me think I’ve buggered up the spoke lengths

    matthew_h
    Free Member

    What hubs are you using?

    It’s really quite rare to find a rear wheel that will have the same length spokes on both sides.

    DT78
    Free Member

    Chris King.

    ERD quoted at 592mm,

    Spoke calc said 286.9 / 285.7 so i used 286’s all round

    isitaboutabicycle
    Free Member

    As long as there isn’t masses of thread showing when the wheel is dished and tensioned reasonably well, you don’t need to worry about your spoke lengths. I assume the hub flanges must be fairly different diameters or something?

    DT78
    Free Member

    I’m wondering if when you enter the ERD details the quoted rim ERD needed to have the nipple depth added to it (so plus 2 x 4mm). As looking into measuring it this seems to be what you should do.

    matthew_h
    Free Member

    I would definitely not use the same length spokes on that.

    Try building it with the 288s on the NDS and see how it goes. Should work out a lot better. Ideal would possibly 287/286 NDS/DS but try the 288s as you have them

    DT78
    Free Member

    Flange diameter is the same at 57.4 / centre to flange is 20.1 and 33.9

    isitaboutabicycle
    Free Member

    Sorry, I’ve only just caught up with the 5-10 bit. You’re right, I’d be aiming for 20-25 on the drive side which should leave the rest at at least 15.

    matthew_h
    Free Member

    What’s the rim?

    PeterPoddy
    Free Member

    This is where the tension meter comes in.
    Any dished wheel will have different tension side to side. That’s unavoidable. But if you know what each side is tensionned to, you can average the two readings out to get the correct tension. 🙂

    DT78
    Free Member

    Its a Light bicycle carbon rim, the tension is up to 20 ish on the DS but 5-10 on the NDS if I get it dished. As soon as I wind it up more it just pulls over.

    I’m planning on swapping the alloy nips to brass anyway so a respoke isnt a big deal, but ideally I wouldn’t completely take it apart.

    Only my 3rd wheelset, seems I’ve been lucky with the spoke calcs before. I’d read 2mm on spoke lengths either way would be fine.

    Front wheel had some nipples crack as thread was showing on one side. So should I have added 8mm to the quoted ERD to take into account the nipple depth?

    RustyMac
    Full Member

    What spokes? how much would you need to tighten the drive side by to get it dished and the non drive side at 15?
    My understanding was that carbon rims could take higher spoke tensions than conventional alloy rims.

    There is not a lot more work in stripping it right back and re building if you are going to replace all the nipples any way.
    I’d advise stripping it down and accurately measuring the ERD then ordering the correct spokes. Your looking at maybe 20-30 minutes more work to know you have it spot on.

    matthew_h
    Free Member

    I think I would unbuild the wheel and measure the ERD yourself. Make sure you get it right. I haven’t trusted the ERDs for any of the Light Bicycle rims I’ve built so have measured them.

    Also, be careful just winding on loads of tension on the grounds that the rims can take it. They can but your hubs probably have a maximum build tension too. I know the R45s do. You can crack the flanges if you build too high

    DT78
    Free Member

    Revs. which also confuses me a bit as I read that because they are tapered the tension might be lower.

    When it gets to 20 it is at the point where the alloy nipples are starting to round hence why I want to go with brass now.

    When I was running a 2.1 tyre I never noticed there was an issue as it didn’t rub so didn’t notice it was out of dish

    What sort of tension should I be looking for then? I thought using the factory wheelset was sufficient

    matthew_h
    Free Member

    Woah, getting readings of 20+ with Revs is way too high. That’s about 150kg force. Definitely sounds like you’ve got the spokes too short.

    With Revs I would probably go no higher than 18 (119kg) on the DS and then whatever is required to get the dish right on the NDS

    matthew_h
    Free Member

    This is the conversion chart:

    http://fcdn.mtbr.com/attachments/wheels-tires/777165d1362350568-park-tm-1-conversion-tables-imageuploadedbytapatalk1362350566.489881.jpg

    Revs are 1.5mm at their smallest diameter so use that as your reference for the tension

    DT78
    Free Member

    Ah. So copying the old wheelset was not a good move.

    Minefield this. Actually lacing the wheel and trueing is the easy bit working out the bloody numbers and lengths is the difficult thing!

    Reckon you are right. Dissamble and start again from scratch.

    I’ll keep telling myself you learn more from your mistakes

    scaredypants
    Full Member

    How would spoke length alter tension ?

    Unless they’re either sticking up & puncturing your tube / tape or else not properly engaged on the nipple, it can’t be a factor, surely – if you’re building to tension rather than just “x turns for each spoke” ?

    matthew_h
    Free Member

    Learning from these experiences is definitely a good thing. It’ll help you to realise earlier in the build when things aren’t looking or feeling quite right.

    I’m still learning and I’m well into the thousands of wheels built

    matthew_h
    Free Member

    How would spoke length alter tension ?

    Because he’s having to wind the DS spokes far too tight to get the dish right without the NDS being too slack.

    scaredypants
    Full Member

    but tension is to do with how much spoke there is between flange and nipple ( 😳 ) and the absolute spoke length isn’t relevant assuming you’re not so far out that you can’t wind the nipple on either a bit more or a bit less

    ?? (am I missing something) 😐

    matthew_h
    Free Member

    Yeah, actually you’re right.

    Geometry and the resolution of the forces in the wheel mean that it shouldn’t make any difference what the lengths are as long as neither side has hit the end of the thread.

    Readings of 20 on one side and 5-10 on the other seem too far apart to sound right to me so that suggests that something has gone amiss somewhere and the spoke lengths used don’t sound right to me (ie using equal lengths side to side not the actual lengths) and I think that is what has confused me.

    Hmm.

    I’m sure that seeing the wheel in real life I could figure the solution out quite quickly

    gazza285
    Free Member

    Spoke length does not alter tension. Do not copy factory wheels, most of the ones I have seen have some form of thread lock on them, so any tension readings you get will be false anyway.

    DT78
    Free Member

    Hmmmm.

    I’ll try completely detensioning then tightening up again. If that fails its take it apart, measure properly and rebuild. Looks like I’ll need to get a few nice ales in for the weekend 🙂

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