Spokecount for cx wheels

[Multebear]

I'm building a new wheelset (carbon tubulars) for the cx bike (canti), and am considering the number of spokes needed. For road I always use 20/24 which seems to be appropriate. I'm 85 kg (187 lbs) at the moment, and when I'm in shape, I'm around 80 kg (176 lbs). They will get a lot of abuse obviously since it cx.

I'm looking at a 30 x 25 mm pair of farsports tubular rims at 300 grams each. I think the 260 grams version will be to light for my bigger body frame.

Will 20/24 be a gamble? And do I need to go 24/28?

[Lelandjt]

Definitely not 20/24. I was gonna say 28/28 but maybe you could go 24 in front if you don't mind giving up some stiffness.

[Multebear]

28/28 for cantilever brake wheels?

[morganb]

All of my cross wheels have been 28/28 or 32/32 except for a pair of Ksyriums that I totally trashed. I've destroyed a 28/28 Velocity Escape tub but been able to ride it out at least because of the high spoke count.

[Lelandjt]

You weigh even more than me (10ish pounds more) and with my riding style I appreciate light but stiff and strong parts. Unless the rest of the build is ultralight and not particularly stiff, a 24 spoke front wheel will probably be noticably flexible. I'd take the 20ish gram weight hit for a stiffer, more bombproof front wheel.
If you were comfortable with the lighter layup rim I'd be comfortable recommending a 24 spoke front wheel;)

[Hellgate]

I used to run 28/28 DT RR 1.1. Was 158lbs at the time. Raced about 35 races in a season for two seasons and only cleaned the wheels. These days I'm 164 and use Zondas. 16/21. They work great, cheap too.

Sent from my ONEPLUS A5010 using Tapatalk

[Multebear]

This is a surprise to me. But I will take your advice. I just wonder, how it’s possible to ride zipp 202 and 303 with very low spokecount like 18/24 for cx if the recommended spokecount is 28/28 for carbon tubulars.

[bm0p700f]

All the above comments assume all rim are of equal stiffnes as are all spokes this is not the case. There are 24F/24R disc brake wheelsets that will be reliable for cross but then with some rims the spoke count needs to be higher. so this question cannot be answered unless the rim is known.

Example Kinlin XR31RTS disc brake rims 24F/24R with sapim CX force and miche hubs will be fine for CX racing. Velocity ailerons are also stiff enough for low count but 28F/28R is stiffer. use a shallower rim though like the kinlin XR22RTS or the other rim around 22-25mm deep then a 28F/28R would be better.

Spme of the shallow stans rims should be build 32F/32R.

Velocity escapes are shallow tubular rim and should be build with a 32 spoke count rear.

Rim depth and width tells you the spoke count needed. mostly use sapim race or sapoim force or there equivlents. A 2.2mm elbow is really useful for disc brake wheels. Also thinner spokes like CX-rays or pillar 1422 or even sapim lasers work for very stiff wheels.. For example Ailerons built with CX-rays or those deep Kinlins built with CX-rays would be fine in 24F/24R.

It simply come down to lateral and radial wheel stiffness. What most people think are stiff wheels are floppy in book.

going back to the OP's question. 25mm deep carbon tubulars rims are not that stiff if they are that light. They might be O.K in 24F/24R but use washers and stiff spokes better use 28F/28R and thinner spokes you will have a better wheel.

All that is based on the wheels being for disc brake which they are not so it is all the wrong reply.

[simoncx]

Last couple seasons I ran 20h and 18h front tubulars mostly carbon 38 or 50mm high without any problems some wheels are 2-3 seasons old. This year I ran 2 disc wheelsets that are 20h front without any problems the rest were 24h and didn't see any difference, no flex or truing needed after races. For reference I'm about 155lbs or alittle less and ride pretty aggressive. One thing that I would look for is 25-27mm wide rims, a lot more gluing surface and hold lower psi better.

[ergott]

CX isn't necessarily harsher on wheels. Don't forget you cushion the wheel with a 30mm tire and low pressure. Road wheels are subject to potholes and the like with only a 23mm tire usually at 90psi or more.

Canti brakes do work better when the wheel is dead true so a few extra spokes does help. I'd say that a very stiff carbon rim and 24/24 should be fine. Yes, 20 is probably strong enough, but more susceptible to going out of true and brake rub. I run mini V brakes and they are closer to the rims than my road calipers.

[F45]

I went to 32 32 after a stick went into my 20h front wheel and sent me over the bars. It was the most confusing .65 seconds of my life.

[bm0p700f]

For cantis 20f 24r could be enough but 28r would be better. I assumed that new cx wheels would be for a newish cx bike. Obviously the op does not believe in braking.

[Multebear]

For cantis 20f 24r could be enough but 28r would be better. I assumed that new cx wheels would be for a newish cx bike. Obviously the op does not believe in braking.

I'm not gonna open the disc vs. canti talk. Just looking for advice for the next build. The rims that I'm looking at are around 300-340 grams tubulars at around 30x25 or 30x23 mm in dimensions. So is the advice that 28 rear is most preferable and 20 or 24 front? Or do you think 28 front as well?

I'm not afraid of adding 4 spokes on both wheels to get more wheeldurability. But I'd prefer to avoid to go 32/32 if I don't have to.

[bm0p700f]

I was simply joking. if you can make cantis work for CX go for it.

Front wheels are inherantly stiffer so a 20H front will be fine. 20F/28R would be ideal. The stiffer the rear wheel the longer it will last and if your RD does take out a spoke then you stand a chance of finishing the lap at least or the race maybe. CX seems to be a very destructive sport for rear mech, hangers and wheels.

[kavitator]

Tubulars in CX races - one hard crash in rock with low pressure in tire- cracked carbon rim.
Hookles will be more durable (tubless) or heavier (more durable) rim (40mm deep)

24/28 spokes