Disk brakes cause spoke breakage!

[ripvanrando]

I am considering buying a bike with disc brakes after a long ride in the rain. All of my front wheels have 16-20 radial spokes.

I just learned that disc brake front wheels have a whopping 24 spokes and they are CROSSED?

***?

Any engineers to explain why? And how did they determine 24 was the right number? Why not 20 spokes?

[zap]

edited.

Originally Posted by ripvanrando

Any engineers to explain why? And how did they determine 24 was the right number? Why not 20 spokes?

Sure why not. Our front disc tandem wheel has 20 spokes......Rolf Prima Tandem wheelset.

Purchased in 2012 and have at least 12,000 miles on our Rolf Prima Tandem (disc) wheelset.

[ripvanrando]

Originally Posted by zap

edited.



Sure why not. Our front disc tandem wheel has 20 spokes......Rolf Prima Tandem wheelset.

Purchased in 2012 and have at least 12,000 miles on our Rolf Prima Tandem (disc) wheelset.

That is the best engineering explanation ever.


Almost like putting dimples on rims because golf balls traveling at 120 mph have them. Why not? People will love them.

[zap]

Originally Posted by ripvanrando

That is the best engineering explanation ever.

Talk to the fime folks at Rolf Prima

[Toeclips]

Maybe the guy overheated

[KonaSS]

The guy lost 10 minutes on a stage, was understandably frustrated and looking for a reason, blames equipment as an excuse.

His explanation doesn't pass logic either in mode of failure, or the amount of time lost (unless it was a 10 minute wheel change).

Nothing to see here unless you want to believe in bogeymen and that all disc brakes are bad.

[rain dogs]

Isn't this a pretty simple engineering question for someone with experience with heat cycling metals? (Understand I am NOT that person) but wouldn't a steel spoke have to be heated to something in excess of at least 300°C to see even the most miniscule influence on fatigue/strength, and even then.... I mean, we safely braze steel frames at many times that heat and sure, not the same mechanics, but really.

300°C may not seem like so much, but, you're talking heat that would have to transfer from the disc, through the aluminum carrier, into the hub, out to the flanges and into the spoke through a very small interface ALL while spinning through the air travelling at some 90kmph.

That would have to be a MASSIVE amount of heat at the disc. Like MASSIVE. I'd wager a bet that tubulars will explode on a rim brake rim at a MUCH lower temperature than a spoke from a disc brake rim (but that is a guess.)

I don't buy it. When compounded with it being the drive side spokes....

For sure, there are heat related effects of discs. Bearing grease degrades more quickly in the disc side bearings on disc hubs. 100%. I think grease breaking down a little more quickly and spokes failing because of heat is not the same cup of tea.

[b33]

Originally Posted by GregL

His bike/wheel sponsor (Specialized/Roval...) has got to love that article, complete with a photo clearly showing their logos all over bike and wheels. Talk about biting the hand that feeds you...

Greg

Dunking on Specialized is a victimless crime.

[redir]

I don't really care either way about disk brakes on the road. If I get a custom frame made some day it will probably have rim brakes just becasue they are good enough for me and I have good rim brake wheels but...

Every time this argument comes up I think to my self that disk brakes were probably one of the greatest inventions for Mountain Bikes and I would not ever even consider going back to rim brakes. And my MTB brakes need occasional pad replacements but they run almost 100% problem free for years before they might need to be bled or something. And I am not breaking spokes on my MTB wheels left and right either.

So if they are all that good for MTB (which I can argue is a lot harder on braking then on the road) why are they so terrible for road bikes?

Again, I don't think they are necessary for road as I can flip my self over the bars with rim brakes so they are certainly good enough, but bad for the road?

[unterhausen]

Originally Posted by KonaSS

His explanation doesn't pass logic either in mode of failure, or the amount of time lost (unless it was a 10 minute wheel change).

He was dropped on the climb and the wheel failed on the descent. I imagine that the problem got bad enough he really needed a wheel change, and it really doesn't surprise me that it would take a very long time to get a wheel under those circumstances. He had plenty of time to think of people to blame, that's for sure.

[KonaSS]

Originally Posted by StephenCL

To be fair, I remember reading an article maybe 4-5 years ago written by an Engineer that cited this as his entire reason he would never go disc brake. I remember specifically he cited catastrophic spoke failure due to repeated heat cycles....

https://cyclingtips.com/2022/05/did-...and-heres-why/

So......can we take a pause on quoting/sourcing thoughts from "Engineers" for a while.....?

[rustychisel]

Wait, what would Hambini say? He's an engineer.

[Tandem Rider]

Is there any grease left in the bearings? It doesn't take much heat to get the grease to run like water. The grease is between the rotor and the spokes.

[rain dogs]

Originally Posted by KonaSS

https://cyclingtips.com/2022/05/did-...and-heres-why/

So......can we take a pause on quoting/sourcing thoughts from "Engineers" for a while.....?

Exactly, this. That's silver brazing temperature 925C that spokes are resistent to... much higher than what I speculated above.

Another example of "the internet of logic". We seem to like to lose our minds before use our minds.

[Wakatel_Luum]

Originally Posted by redir

So if they are all that good for MTB (which I can argue is a lot harder on braking then on the road) why are they so terrible for road bikes?

Again, I don't think they are necessary for road as I can flip my self over the bars with rim brakes so they are certainly good enough, but bad for the road?

Apparently it's the higher speeds on long descents that cook the brakes, causing the discs to warp, rub etc on road bikes. Cooling them down is more of an issue.

MTB's are generally run at slower speeds overall and more stop/start.