TakingMyTime

OK, crush may be a bit of an exaggeration. I've also read all the other threads regarding spoke count, but unfortunately I have to ask about this particular situation. Since I may be dropping 2K+ on a bike (which I consider a lot for a bike), I'd like to have all the info I can get.

I really like the new Trek ALR 6 Pro. But... the "Vision Metron 40 LTD" wheelset appears to have 18 spokes in the front and 21(?) in the rear. I contacted Trek and they said the spoke count is the same for all size frames/builds. I understand these are very nice wheels but at my weight 210#, I worry about such a low spoke count. Granted, I do ride on very smooth well maintained roads and paths here in Southern California and this bike/wheels would not be abused, but I still worry about durability and longevity (which I care about more than weight etc). Also, I'm not a powerful rider by any means.

Should I be concerned about such a low spoke count or just shut up and ride it?

GeneO 

I ride 18 + 20 spoke Fulcrum race 7 LG CX @ 215# with no problem. It depends a lot on the wheels I think; I have wheels with higher spoke-count whose spokes loosen.

ltxi

About the same weight and also ride good paths/roads. Both my road bikes are on 16/20. Shimano wheelsets...RS11 and Ultegra. Work well.

fa63

You will be fine.

rmfnla

New bikes come with warranties...

Doge

The spoke count is not likely the issue. The rim material and profile/hub maybe. Rear is likely 20, 24 hole. 21 - would be odd.
210# is an issue for most. I expect you are using 25mm+ tires?

Looked it up - it is "odd" 14 cross x2 drive side and 7 radial non drive side (2:1 ratio)

So kinda like 28 back there. The tension should be about the same per spoke. Campy does this. I like it.

rpenmanparker 

As you found out, 21 is quite likely. Not odd at all. The spoke pattern is called triplet lacing or 2:1. There are twice as many spokes on the drive side as on the non-drive side. That means that the total number of spokes has to be a multiple of three. So the drive side has 14 spokes and the non-drive side has 7 spokes. That is done to balance the spoke tension on the two sides. Due to extreme dishing, the individual spoke tension on the non-drive side would only be about 1/2 of the tension on the drive side. But by using the 2:1 pattern, you get twice the tension on each spoke on the non-drive side by cutting the number in half. So the spoke tensions on the two sides will be almost identical. That makes for a more durable, more trouble-free wheel.

Sure you will see 16:8 = 24 more commonly, but Campy is well known for its use of the 14:7 pattern.

dvdslw

I'm 225lbs and have had no problems whatsoever riding on my Ultegra's with a 16/20 spoke count or my Easton EC90SL 38mm full carbon clinchers also with a 16/20 spoke count. My train of thought is that a factory built wheel will be just fine but don't even think about hand built. Every builder out there will say you need more spokes because they can't build them like the big boys.

noodle soup

Oh really?

I've built a few low spoke count wheelsets for a very powerful 240# rider, and had no build related problems. He's destroyed a few freehub mechanisms, but has had no problems since upgrading to WI hubs.

It can be done, but some builders are worried about their business reputation(if the have a problem).

Chandne

I'm looking to build my first-low-spoke-count wheels. My builder (has a very good reputation here) says that at 175-180, he would feel comfortable building even a 20x24 wheels as long as the rim was stiff to begin with. I think most carbon rims at 30mm+ will be stiff. A few aluminum rims are stiff too, even at shallow depth. I think it kinda depends on the rim.

Fox Farm

++

fa63

The big players (Shimano, Mavic, Campagnolo/Fulcrum) typically build wheels using less spokes at higher tension and with sturdier rims. I think this is in part to satisfy consumer demand for aesthetics (less spokes look cooler) and also to reduce costs. The problem with this approach is that given each spoke is having to carry a larger percentage of the wheel load (relative to a higher spoke count wheel), chances are that you are SOL if you break a spoke and need to limp back home. The spokes also tend to be proprietary (which means expensive to replace). Last but not least, one size fits all approach means that the wheels are really optimized for the "middle of the bell curve" riders, so if one falls outside this range, the wheels may not work the best.

That said, I have had good luck with all the wheels I have used from the big three, even though I am a big rider at 225 lbs. In fact, I like my Fulcrum 5 LG wheels better than my hand-built 32 spoke front/rear wheels built around H+ Son TB-14 rims (using same tires/pressures). But if I am doing a long ride away from home, I am taking the 32 spoke wheels every time.

fietsbob

I'd save the Fancy Wheels for races and use something less exotic the rest of the time.

rpenmanparker 

There is no reason to increase spoke tension whether the rims can take it or not. The wheel does not get stiffer as the spoke tension increases, so you can't make up what is lost in tension with fewer spokes. The notion of there needing to be a certain "total tension" i.e. a certain sum of the tensions of the spokes is just a false myth that has somehow become part of wheel lore. So as the spoke number goes down, there is no need to maintain the total sum of tensions with higher tension per spoke.

Shimagnolo

"There is a best ratio between rim cross section,
spoke diameter and number of spokes. As the spoke count is reduced,
spoke tension must be increased to prevent slackening in use."

Source - Jobst Brandt, but what does he know about wheels? Spoke count (Jobst Brandt)

fa63

Higher tension may not result in more lateral stiffness, but what about radial stiffness? Improperly tensioned spokes cannot support the rim. If a spoke goes slack, it results in an unsupported length of rim and when a radial load is applied, the adjacent spokes will have to pick up the slack. This becomes a bigger problem for wheels with fewer spokes, as the unsupported length is greater.

Or maybe I am missing something, which is possible, and I am always open to learning new things

gsa103

On a properly built wheel, the spokes never goes slack. The goal is to set the tension such that all spokes always have some tension.

The problem is that rim is essentially a point contact, so almost all of the load goes into a single spoke when that spoke is directly vertical. The span gets even moderately large (probably less than 40 spokes), a single spoke has to be able to take essentially the entire load, and will require the same amount of tension. So that means going from a 32h wheel to a 24h wheel, the spoke tension might only need to increase by a small amount. If a stiffer rim is used, then the spoke tension might not need to increase at all.

noodle soup

Jobst knew a ton about wheelbuilding, but many of his "facts" are outdated.

A few years ago we spoke about how things were changing, and he admitted that it was time to update his book. We talked about wheelbuilding for almost 20 minutes at Interbike before his name badge flipped around, and I realized who I was talking to.

I almost immediately started back-pedaling, but he actually seemed to enjoy the disagreement.

You never know who you'll talk to at Interbike

fa63

Good points. Going slack was an extreme example, and it is not so much a matter of adjacent spokes picking up the slack. So what you are saying is that, all else being equal (rim stiffness, etc.), going from a 32 spoke wheel to a 24 spoke wheel does require an increase in tension, though it may be small, correct? In that sense, it makes sense that wheels with fewer spokes would need to resort to stiffer rims and/or increased spoke tension to maintain a desired radial stiffness.

rpenmanparker 

To prevent slackening tension does not need to be increased per se, elongation needs to be increased. Yes, that can be done by overtightening the same gauge spoke or alternatively by simply using a lighter gauge spoke at the usual tension. Even robust rims can't tolerate tensions much in excess of 130 kgF or so for very long. Neither can spoke and nipple threads. The best plan for low spoke counts is to use ultra-light gauge spokes at moderate tensions.

rpenmanparker 

No, stiffness in any direction is a matter of rim stiffness and spoke stiffness. Spoke stiffness is a function of spoke gauge and number of spokes. Tension is not a factor.

ThermionicScott 

I may not remember much from grade-school math, but 21 is definitely odd.

rpenmanparker 

Touche.

Doge

Think you missed my "odd" pun.
Anyway, I did not know others than Campy were doing that. For decades there have been attempts to balance tension. I built 2.0 on drive, 1.8 on non drive and in 1983 that was same TSI (Tension/sq/inch). Dish has changed. But the best, highest performance wheels are not all the same. Spoke breaking is not all that much an issue these days.

rpenmanparker 

Different gauge on the DS and NDS does nothing to balance tension in the spokes on the two sides. It helps to balance tensile stress as you pointed out. That isn't tension. It relates to making the spoke elongation more similar at different tensions. But still, if that is what you want to do, you need a 1.5 mm spoke on the NDS to match the elongation of a 2.0 mm spoke on the DS, tensions being the same.