Which wheel is stronger?
 

A heavy rim with 32 spokes, or a lighter rim with 40 spokes?

For example, a (675 gram) Velocity Cliffhanger with 32 spokes, or a (465 gram) Velocity Aileron with 40 spokes.

I suspect there's no simple answer to this, I'm just looking for general knowledge on rim strength vs. spoke count engineering.

Proof by popularity contest. You've come to the right forum.

Usually the strength comes from the rim and then you need spokes to keep the rim in place I think. 32 should be plenty strong. Strong alu rims for 26ers mtb start at about 500g or so and end at about 700g. For 29er mtb you can add at least 50-100g to that. Strong road rims start at about 500-550 or so think dt tk540.

You also want:
welded rims, not pinned or sleeved.
butted spokes like comps or alpines. Get the known brands.
brass nipples.
double eyelets.
even tension in all spokes. (That you can only get from a round rim to begin with)
And so on...

a Heavy rim* with 48 spokes in a dishless wheel , Like Fronts ...

*Sun Rhyno (not the 'Light', model) .. Prior I built a wheel set with Mavic mod 4 ..

I built 40 fronts 48 rear , a 48 front and reat offers you will have a spare rear rim

and take what you can find as a front wheel, when your rear rim is damaged..

Seeking repairs in the small town ..







....

Rims with fewer spokes are usually built to be stronger (and heavier) to compensate for higher spoke tension at each nipple/rim joint and to spread the load across more spokes.

So it's not simple - straight forward.

Add the problem of dished rear wheels, where left hand spokes have much lower tension. If a rim is weak (hence can't take much total spoke tension of all the spokes used) AND has many spokes, it can suffer from left hand spokes being too loose.

However, both rims from the example seem decent, double walled (one is just "deeper"). So I'd put a slight advantage towards the one with more spokes. Even though the other one should hold up fine even with 32 spokes, unless for tandems and/or heavy touring.

The extrusion Die Produces straight pieces which are then rolled into a hoop..

the hoop is then drilled for spoke holes

A Sun CR 18 profile extrusion in a 32 hole 406 rim will be stronger than a 32 hole 622,
mostly because of its size..
secondarily because the distances between the spokes is closer together..




...

If you are running the same rim size and rim model on each setup more spokes is always stronger. 36 spokes was the standard other than racing bicycles until some fast talking weight weenies swayed opinion and had some people convinced that 32 spokes was and upgrade. Industry saved a little money and bicycle shops made money when more failures happened. Narrow extruded rimes are cheaper to build not stronger. Having the spoke holes drilled with little offset between left and right is weaker. I have Velocity Psycho rims on my touring bicycle. My son has Ryde Andra 30s, both wheel sets use 36 spokes.

I think that you have to evaluate the wheel as a complete assembly.

More spokes will certainly be stronger - to a point. More spokes also means more holes to weaken the rim and the hub flanges. It's much cheaper and easier to replace a broken spoke than a failed hub flange.

I would much rather break a spoke on the drive side of a 36h wheel than on a 24h wheel.

Are we to assume the same spokes and build quality for both? I'd take a well-built 32-spoke wheel over a poorly-spec'd and built 36-spoke wheel ANY DAY.

Yes.

But what about a poorly built 40 spoke wheel? (kidding)

I find it a bit small compared to some people

What is a recumbent exercise bike?
 

:lol:

I think the back wheel on my old English 3-speed qualifies. The tensions were all over the place, but it still held together for 50+ years since so many were sharing the load.

I’d go with the 200 gram lighter rims any day of the week and twice on Sunday. Simply put, rims do very little for the overall strength of a wheel. Think about how the spokes are attached to the rim. It’s in tension only. There is no compressive force of the spoke on the rim. When the rim reaches the bottom of the wheel, it deforms slightly and slides up the spoke. The spoke undergoes momentary detensioning and then is retensioned as the rim moves away from the bottom of the wheel. The spoke is doing all the work.

Additionally, when a side load is put on the rim, the rim does very little to resist that load. A heavy or light rim will still flex sideways under load. If the spoke is weak, the head will flex and bend. Eventually, like a bent paper clip it will break. Try riding a rim that is poorly tensioned and you’ll feel the wheel snake belly on the road. Tension it up properly and the rim won’t bend as much but it is the spokes resisting the bending, not the rim.

If you really want to make the wheel stronger, use spokes with heavier heads like the DT Alpine III or the Pillar triple butted spokes. The heavier head fits in the hub better and resist fatigue about 50% better. Ric Hjertberg says that it like a 10 spoke increase in spoke count. I wouldn’t go that far but it is at least a 4 spoke increase. A 36 spoke wheel with DT Alpine III spokes will be at least as strong as a 40 spoke double butted spoke wheel.

I’ve been using triple butted spokes for the last 20 years on mountain bikes and loaded touring bikes. My incidence of spoke breakage went from often to essentially never even with mountain bike rims like the Mavic XC717 or Velocity A23 road rims. The way I build didn’t change, only the materials I use for building.

Steel rims are stronger, but not in any way that makes them better. If you are selecting rims to beat them with a hammer then stronger would be the primary consideration. But if you are wanting stronger and more robust WHEELS, then I am of the view that lighter less strong rims can be laced into a stronger wheel with more spokes that stays true longer despite challenging conditions.

I note what John Allen of sheldonbrown.com says about the trend toward lower spoke counts (quoted from: https://www.sheldonbrown.com/tooltips/truing.html)

"One additional warning: The techniques described here are not very applicable to "boutique" wheels with low spoke counts, unevenly-spaced spokes and rigid, deep-section rims. These wheels often cannot be made rideable if damaged. That is one good reason not to ride such wheels. They are expensive, too, a clear case of paying more for less!" -- John Allen

-Will

What are you doing with these wheels? Why is extreme strength required? If you have any doubt about the strength of a 32 hole wheel with a 465 gram rim the most likely reasons for lack of faith in that wheel are 1) you have been working with poorly built wheels, which is most wheels, or 2) you are carrying very heavy loads. If carrying lots and lots of weight you do need special wheels.

Strongest wheel I ever built was a Campagnolo K2 rim, 28 hole. K2 was a lot like the slightly better known Campy Atlanta rim, but in 26"(559) and 24mm wide. 500 some grams. I looked at how massively strong that rim was and connected it to an old Dura Ace 28 hole hub that was lying around. With only 14 spokes. Nice light Union 0.80/0.60 spokes. Basically 2.0mm/1.5mm. Beat that rim up for about a decade on MTB trails. When I was done with it gave it to a stunt rider. He promptly got himself airborne and did a few tricks he was sure would fold that wheel. His normal rims were 20" steel that weighed 6 or 8 pounds before being built. Just could not believe how strong the Campy wheels were. He tried hard and kept trying. Folded a good few forks and some frames before he succeeded in breaking that wheel.

Rim strength matters. Spoke strength matters. Build quality (even tension and sufficient tension) matters a whole lot. Wheels mostly work even when badly built and made with poor quality materials. If bad wheels didn't mostly work this whole bike thing would never get off the ground. Perfection is not required. Use good pieces and get a good build and you are just not likely to have problems. Unless, again, you are carrying extra heavy loads.

Assuming you don't run over pot holes, curbs and stumps for the fun of it daily, then I'd go for the lighter rim. And unless loaded weight is near max, then I'd probably opt for the 36 spoke version on the back and 32 on the front instead of the 40. Wheels of equal weight and same tires that have lighter rims should require less wattage. Though probably a minuscule amount.

But I'm certainly no expert at wheels in general.