Carbon rim spokes question

I currently ride a steel hardtail 26 with big tubeless tyres on Mavic 521 32 hole on the front and Stan’s Arch Ex 32 hole on the rear. I’m not a delicate rider but also not brutal, I weigh 80kgs and prefer to ride techie trails in the Lakes and Peak.

I’ll soon be getting a 5inch travel full suspension 27.5 and I’m thinking of trying some of the wide Light Bicycle carbon rims (30mm internal?) . Can I sensibly go down to 28 spokes?

What advantage are you expecting to get by having 4 less spokes?

Hmm, lighter.

Plus it’ll be less affected by stray custard

Hmm, lighter.

all of about 20g, I personally would go for lighter spokes (Dt revs, CX rays ect) rather than less spokes to save that weight.

Good idea, that means I can keep my hubs. Thanks

FWIW If it wasn’t for you having the hubs already, I would go for lighter spokes AND less spokes. The LB 35s don’t need stiffness adding…its the opposite! But its not worth ditching your hubs for. Remember you’ll also want to factor in 14mm nipples (rather than the standard 12) ideally, which may or may not effect spoke length depending on your nipple choice. Also, be aware that LB rims tend to need +2 mm on most spoke calcs IIRC… although someone who’s built a set more recently will be able to advise if that still holds I suspect.

Fewer spokes people, fewer. Not less.

lesser spokes could be an option though

Fewer lesser spokes could work, yes!

less money too.

The wide LB rims are great but I really wouldn’t bother ditching 4 spokes – Minimal weight saving for a weaker, bendier wheel, especially with a really stiff rim like that, I seem to remember reading that the effect is actually worse than with a bendier rim because of additional deflection on the opposite side (of the hub) to the load.

Some good stuff on Sheldon Brown on spokes, paraphrasing him from memory 36 to 32 was a marketing gimic and we really should have stuck at 36 and taken weight off the rim instead.

From the Nox site: what makes a stiff wheel in order of importance:-
1)The rim stiffness
2)The number of spokes
3)The spoke bracing angle
4)The gauge of the spokes
5)The lacing pattern

So if it was me I’d use thinner spokes rather than fewer spokes but that said, there are plenty of decent 28 spoke wheels around (Enve are 28 hole 2 cross, I think)

all of about 20g, I personally would go for lighter spokes (Dt revs, CX rays ect) rather than less spokes to save that weight.

Agreed, but go for Sapim D-Light’s or DT Super Comp’s IMO. Not quite as light, but usefully lighter than DT Comps, also usefully stiffer in my experience.

Fewer spokes people, fewer. Not less.

:LOL:

FWIW If it wasn’t for you having the hubs already, I would go for lighter spokes AND less spokes. The LB 35s don’t need stiffness adding…its the opposite!

Wheels should be as stiff as possible IMO. If you want more comfort, run a bigger tyre and/or tubeless and/or let some air out.

Also, be aware that LB rims tend to need +2 mm on most spoke calcs IIRC… although someone who’s built a set more recently will be able to advise if that still holds I suspect.

LB’s quoted ERD’s are a few mm short of actual. Built up 4 30mm rims the other day (24mm internal) which are quoted as 600mm ERD. The measured ERD was more like 604mm, and I needed to use spokes 2mm longer all round than calculated using their quoted ERD.

FWIW If it wasn’t for you having the hubs already, I would go for lighter spokes AND less spokes. The LB 35s don’t need stiffness adding…its the opposite!

Increasing rim stiffness but decreasing spoke stiffness has the effect of increasing wheel twist.

If you want maximum line holding, lace them with Sapim Races and run big **** off dual ply tyres at as low PSI you can run before squirm/rim dents kick in. If you want the lowest weight, by all means go for lighter spokes.

Stiff than Cx-Rays or Revs maybe – they’re not stiffer than Comps (you’re spot on with your other physics stuff though).

Personally I’d still recommend 32 DT Comp (or Sapim Race) – the lad is 80kg, the arguments about losing weight on road bike wheels apply equally to mountain bike wheels. No way will he notice the difference of 90g on his wheels he gets by using Rev/Laser/Cx-Ray, which will improve his acceleration by 0.2%! He might just notice the decrease in lateral stiffness, resulting in twist as Tom points out.

I’ve been thinking along the same lines as the OP. What about running 28 spokes in the front and 32 in the rear? Mavics are 24 spokes IIRC.

IMO the whole idea of wheels being too stiff is utter bollocks unless someone can educate me and put me right. I reckon when people complain about not enough grip in corners due to stiffness, 99% of the time it’s because the frame is way to stiff.

If I was racing I’d throw my money at the first company that came out with a decent bike where they offer rear shock links and crowns of varying stiffness values, to tune the bike in for the weight of each rider.

I can’t think of a scientific way to prove it, but I’m sure that’s true. I’m not sure what direction it is people want their wheels to flex. Vertically – well they don’t to any detectable amount – not in comparison with a tyre with 60mm of travel (under static load, a standard old fashioned road bike wheel flexes ~0.15mm vertically – you’d need to pull 7g to get 1mm deflection). Laterally – really? when you’ve spent lots of money on stiffer forks with through axles etc. to eliminate that?

I can understand why you might actually want a little bit of a little bit of lateral flex at the interface between rear swingarm and the front frame at least, if not the forks. This acts as suspension when the bike is leant over, however a bike that is too stiff for a 140lb rider might be perfect for someone of 190lb and vice versa. Bikes such as the Oranges that are sometimes deemed a little soft, I think are fine for lighter riders.

I can’t understand wanting to have twist (a little different to purely lateral flex I think) in a set of wheels, vertical flex is ridiculous.

I don’t need to think of bicycles in this way because I’m not a racer, but it’s just how my mind operates because of my science background. I nerd out very easily.

http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.html

Suspension still acts as suspension when the bike is leant over – with a single track vehicle the force acting on the tyres has to go pretty close to the centre of mass of the vehicle or it falls over. A mid corner bump might change the direction of this force a small amount, but not enough to prevent the suspension doing its job (on a bicycle you also stay a lot closer to vertical in a corner than most people think – unless it’s bermed, but then the direction of the bump force follows the increased lean angle). I don’t think any lateral flex is actually useful – though would be interested to see what really happens using an instrumented bike.

I’m sure lateral flex in a wheel isn’t at all useful even for this, but then we seem to agree on that!

Suspension still acts as suspension when the bike is leant over – with a single track vehicle the force acting on the tyres has to go pretty close to the centre of mass of the vehicle or it falls over. A mid corner bump might change the direction of this force a small amount, but not enough to prevent the suspension doing its job (on a bicycle you also stay a lot closer to vertical in a corner than most people think – unless it’s bermed, but then the direction of the bump force follows the increased lean angle). I don’t think any lateral flex is actually useful – though would be interested to see what really happens using an instrumented bike.

I’m sure lateral flex in a wheel isn’t at all useful even for this, but then we seem to agree on that!

Depends on the lean angle I guess, at a certain angle the usefulness of the suspension is going to drop off considerably.

Yup MTB’s tend to be more upright but the fastest I’ve ever got down the dual at Chicksands was when I had the bike so leaned over on one of the flatish corners I thought I was Marquez 😆 Front and rear tyre both washing out, bar ends inches off the ground….really wish I had a photo off that….to this day I don’t know how I stayed on.

I like to lean bikes over for the lolz even if it means less grip anyway, so I probably shouldn’t be giving advice on what makes a good bike. I ride like an idiot on the whole.

No, because the resultant force will still be in the plane of the bike, and the suspension will still work for the reasons I explained. I reckon my “you also stay a lot closer to vertical in a corner than most people think” stands – I never suggested it doesn’t feel like you’re way leaned over!

Interesting article – though I have one issue, where they talk about high flanges making wheels stiffer. Only if you use radial spoking – which might be a fair point as it’s in the context of wheels some of which are radially spoked. But they then talk about high flanges on the drive side of rear wheels, which are typically tangentially spoked meaning that the height of the flange makes no difference (think about what happens to the length of a tangential spoke when you change the flange height – or try playing around with a spoke calculator).

No, because the resultant force will still be in the plane of the bike, and the suspension will still work for the reasons I explained. I reckon my “you also stay a lot closer to vertical in a corner than most people think” stands – I never suggested it doesn’t feel like you’re way leaned over!

I agree and to be honest I like really really stiff bikes as I think it makes them more playful. However shouldn’t stiffness be balanced against feel? Isn’t there a relationship between contact patch feel and stiffness? I hear about this a lot in motorsports.

Really considering building up the LB 38mm rims with 36 hole Hope hubs. 😆

I’m seriously thinking about getting one for my uni (which will probably be a 36 spoke build, as that’s what most uni hubs are) 🙂

Current idea is to run them on a GT Sanction, with Fox 36’s and 35mm bars and procore inner tubes. The idea being to make a bike that monster trucks over stuff when upright, has reasonably centralized mass and is responsive to weight shifts/being thrown around sideways and weighs under 30lb. Id rather run an aluminium frame (by all acounts it’s very stiff) as I can spend more money on lighter parts, centralizing the weight better and distributing expense around the bike in the event of a crash.

The unicycle sounds great!

Wheels should be as stiff as possible IMO. If you want more comfort, run a bigger tyre and/or tubeless and/or let some air out.

Im not convinced on this. Carbon wheels can feel quite dead and wooden I think when built up very solid, certainly compared to their alloy counterparts. I think its more down to vibration feedback through the wheel than deflection per se. In the same way a carbon bar is a little less jarring than the alloy equivalent. That however is entirely subjective and practically impossible to prove either way, and I’m probably imaging something thats not really there 😉
What I do know for a fact is that a LB 35mm rim running 28h and very light spokes, if well built will be more than capable of taking pretty much any punishment that you throw at it. You’re far, far more likely to smash the rim on a rock and destroy it (I run 17-20 PSI as a rule so going lower pressure isn’t much of an option and Im not wanting to go dual ply) than you will be putting it out of true, so I say go fewer and lighter – no reason not to IMHO.

EDIT: To clarify, I have a set of LB 35s built with Sapim Race 32h j-bend, and a set built with D-light 28h SP. In my head the lighter set is better – its certainly actually lighter, and I perceive its a better wheel. That is probably not true, but what is for sure is neither have ever missed a beat and I would be not believe anyone who claimed they could tell which could hold a line better than the other.

Thanks for all the help, very interesting.

Isn’t there a relationship between contact patch feel and stiffness? I hear about this a lot in motorsports.

I know from my time (a summer placement in 2013) in a certain motorsport teams dynamics department, one of my tasks was seeing how compliance in both roll and heave in the rear end (of the car) effected the handling and CPLvar (EDIT:contact patch load variation, lower=more consistent grip). The findings were along the lines of heave wanted to be reasonably stiff, so to pass as much of the force to the shock/damper, while in heave a small amount of compliance (or even 0.5deg free play) showed to be beneficial to CPLvar, but slightly reduced the body control.

Driver feedback was mixed, one liked the added roll compliance and felt that the could get on the power earlier (which the data backed up) but the other couldn’t tell the difference.

TBH taste is always going to be the more important thing, not more this or less that. And you don’t need to know or understand the science to know what feels right or wrong to you. But that makes this sort of chat pretty fruitless most of the time…

Actually Sapim CX-Ray are the strongest & lightest spokes
If you actually built your own wheels you would know this……

What do you mean by strongest and lightest?

CX-Rays aren’t the lightest spoke you can buy, far from it. All they are is a flattened Laser, in the same way an Aerolite is a flattened Revolution. They do have a higher fatigue strength than a Laser too, but again, this doesn’t make them ‘strongest’.

If you knew anything about the wheels you’re building, you’d know this.