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I am going to build my first bmx bike from scratch. I’ve watched tons of YouTube vids to get me started. I want to build my own wheels and lace my spokes. I was wondering if I can or should use the same 36 spoke rim on front and back wheel? I understand that the hubs are different

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    BTW (and I'm not a fan of YouTube tutorials in general but accept they have their place) a decent written description with diagrams is far better during the actual building of a wheel
    – Chris H
    Commented Jun 23 at 6:40
  • @ChrisH It is in fact harder to produce "a decent written description with diagrams", this is why one finds fewer such things than substandard youtube videos where you can extract the needed information with some luck
    – fraxinus
    Commented Jun 23 at 15:08
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    @fraxinus definitely. Harder but more beneficial. Personally I hate seeing myself on video and find editing a chore, but write technical material and draw diagrams for work. So as well as preferring to refer to old-fashioned tutorial material I find the idea of producing it less troublesome. I had to work from a video the other day (I'd never installed remote lockout before and my new fork didn't come with a manual). It wasn't even in focus!
    – Chris H
    Commented Jun 24 at 5:34
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    In freestyle BMX, many people use stronger rims for the back wheel (because it takes most of the abuse), and lighter rims for the front wheel (so that barspins etc. are easier). For example, with the Odyssey rims (which are popular), the light "birdcage" model is mostly used for front wheels, and the strong "ribcage" model is used for backwheels (they also have the "rollcage" model which is kind of in between and used for both)
    – Fatalize
    Commented Jun 24 at 8:30

3 Answers 3

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Every rim I'm aware of is suitable for both front and rear use. You could use different rims front and rear (for example if you want a wider tire in the front, you could use a wider rim to match), but there certainly isn't any need to do so. The vast majority of bikes will have identical rims front and rear. Best of luck with the project!

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    Another reason for a difference is aerodynamics (e.g. in time trialling) , with the extreme case being a disc rear wheel. People sometimes run a very deep section on the back, but not the front where it's more of a risk in high winds.
    – Chris H
    Commented Jun 23 at 6:38
  • That's actually interesting because the load is so much higher in the back (at least with "normal" bikes with a, say, 45 degree sitting position). Also, with chain gear shifts, the wheel is highly asymmetrically loaded; I can easily see potential for optimization there. (At second thought: With a "normal" bike it is not very interesting to shave off 75g or whatever.) Commented Jun 23 at 15:08
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    @Peter-ReinstateMonica You bring up a good point. I do wonder why even the lightest XC and road wheelsets have the same rims front and rear. Maybe it turns out that the steering and braking forces present on the front wheel require it to be more or less as strong as the rear? Or more practically, it might just be easier for the wheelbuilding factory to use the same rims. Could be worth asking as its own question!
    – MaplePanda
    Commented Jun 24 at 2:21
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    Another example - 32 spokes at the front, 36 at the back (or 24/28 etc) but if they're identical apart from the drilling, do they count as different?
    – Chris H
    Commented Jun 24 at 5:36
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As a general rule, it’s not just fine to use the same rims front and back, it’s actually the norm for a majority of types of bicycle. There are only a handful of situations where this is not the case:

  • Time trial bikes often have much deeper rims on the back, as deeper rims can improve aerodynamics significantly, but the increased cross-section perpendicular to the axle is a liability in anything but a direct head or tail wind when used on the front. The extreme case is a solid disk wheel on the back.
  • If you wish to use different tire widths front and back, you would typically use different rims to accommodate this so that the outer diameter of your tires is as close to being the same when inflated as possible. Normally this would be done to put a bigger tire on the front, which lets you optimize a bit better for traction there (which in turn gives you better braking power and better control during turns), but unless you’re building for aggressive off-road riding it’s probably not worth it.
  • Some bicycles go a step further and use different outer diameters for their tires, which almost always means different rims. This was the norm on many early velocipede designs from before the invention of the modern safety bicycle, most famously the high-wheeler (now commonly known as a ‘penny-farthing’). On more modern bikes, I’ve mostly seen this on recumbent tricycles (TerraTrike comes to mind as a brand that does this) and cargo tricycles, with the single wheel usually being larger.
  • On very rare occasion, I’ve seen people mix spoke counts, usually a 32-spoke on the front and a 36-spoke on the back. Usually this is done simply because that’s what’s available (either immediately at hand, or in terms of what they can get for the hubs and/or rims they want to use).

Aside from that, there are ‘special’ rims with offset spoke holes designed specifically to be used for building wheels that need aggressive dishing, with the idea being that you can better equalize the spoke tension from side-to-side with them (and yes, that really is a thing, it’s just not enough of a thing to matter for how most people actually ride). In most cases, these would only ever be used on the rear wheel with a particularly wide cassette, as that’s the only place you would need to dish the wheel that aggressively. However, you need to go out of your way to get these, and they’re usually far more expensive than ‘normal’ rims, so it’s very unlikely that you’re dealing with them.

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  • The "mullet" setup is actually somewhat popular on MTBs now. 29" wheel in the front, 27.5" in the rear. It's not just penny farthings and recumbent trikes.
    – MaplePanda
    Commented Jun 24 at 2:16
  • Recumbent bikes too, 20"-26" had been very popular for a long time but almost all combinations will have been tried. Smaller in the front is the most usual.
    – Willeke
    Commented Jun 24 at 4:40
  • Small differences in outer diameter are common, but just due to tyre size (e.g. around 10mm on my MTB) so not requiring different rims, it's big differences in OD that matter here. A lower spoke count on the more lightly loaded wheel saves weight so is fairly common too, just not on stock wheels.
    – Chris H
    Commented Jun 24 at 10:01
  • @MaplePanda I actually had not known about the usage on MTBs, though that does make sense given that they’re often going to be cornering aggressively enough for the larger contact area to matter for performance. Commented Jun 24 at 13:53
  • Other benefits of the mullet setup are that the larger front wheel helps roll over obstacles compared to a full 27.5" setup, the smaller rear wheel gives more wheel-to-butt/saddle clearance for full-suspension bikes, and the whole bike is somewhat more nimble than a full 29".
    – MaplePanda
    Commented Jun 24 at 16:51
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Rims exist with an "offset" spoke hole layout. If you had one then it would only be suitable as a rear wheel because front wheels are symmetrical.

This would be fairly obvious when looking at the rim, so if you have one then it's not hard to spot.

They's supposed to be stiffer and stronger by not having different spoke tensions on each side of the rear wheel. Since they're still uncommon, that's likely marketting fluff and any real gains are minimal.

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Based on searches, these offset rims are found more in the wider rim widths of MTBs and fatbikes, and not on road bikes.

Not a dupe but related post: Asymmetric wheel. Which side should the "asymmetry" be on?

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    Front wheels aren’t necessarily symmetrical, and rear wheels aren’t necessarily asymmetrical. For example, on the hybrid I use as a commuter, the front wheel is actually visibly dished to account for disc brake rotor, and the rear wheel has almost no dishing because the brake rotor needs about as much space as the single sprocket for the belt drive. Commented Jun 24 at 1:42
  • @AustinHemmelgarn good point - there's a difference between Rim and Wheel - so its possible to have a symmerirc rim on a wheel that is asymmetric. And excellent point about the Disk rotor balancing out the cassette.
    – Criggie
    Commented Jun 24 at 3:10

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