Pro Connect - Sheard Spoke - HELP !!!!!!!

[JamesC]

coupla reasons why BMX and mtbs bikes have more spokes

Hi properlegs
I can see why the wheels need to be stronger for BMX and mtbs, but why do you see it as important to have MORE spokes rather than THICKER spokes ?

For less demanding stuff with large 700C wheels, my personal choice is still to have plenty of spokes (say 32 or 36), but thinner gauge. It gives the rim greater all round support, so that an occasional high kerb or deep pothole is less likely to damage the rim.

James

PS Quite envious of what can be achieved with BMX's and mtbs, properlegs.

 

[proper legs]

spokes again

A thick spoke is no stronger than a thin spoke when used properly.... double butted gauge spokes (ie where the the thickness changes along its length) are lighter than standard gauge but just as strong, if not stronger. Thicker spokes would neccesitate larger holes in the rim and hub and weaken the wheel. Also it is the lacing of the spokes that provides the strength.... so more spokes crossing more times builds a much stronger wheel... or less spokes at a higher tension does the same but the design of the rim and hub is different. spoke under more tension are often of a straight pull design, IE no heel, or bend in the spoke. This is the weak point of any wheelbuild and modern wheelsets such as the pro connect shimano wheels run straight pull spokes to increase spoke tension and reduce spoke numbers to lighten the weight...

its a black art!

 

[Danny-K]

Yep! Wheel-building is more art than science.

24 or 36 spokes for the Pro Connect? I've read more than one report on this forum of snapped spokes and spokes coming loose on the Pro Connect - any more and I'm going to conclude that for riders over the mythological 150 lbs, (ie., 200lbs+), might be better upgrading to 36 spoked wheels.

However it all hangs together and starts off with the manufacturers stated kgF of force that the rim can handle as a total. Take a quality rim for instance with a total circumferential compressive strength that is able to handle 3200 kgF of force. So with 32 spokes that means 100 kgF for each spoke. The same rim with only 28 spokes would need each spoke tensioned to withstand 114 kgF. The less spokes, the greater the tension needed to maintain the integrity of the wheel when the same rider and frame weight is applied. If a 24 spoke version of the above rim was required the reduced amount of spokes would need to be tensioned even further so that each spoke had to be able to handle 133 kgF.

In the opposite direction if the same rim was chosen to house 36 spokes, then the stress and tension can be reduced substantially as more spokes mean only 88 kGf per spoke. So in this instance the 24 spoked version would need spokes tensioned by a staggering 51% greater than that needed for the 36 rim version. It's no coincidence tandem riders favour 48 spokes per wheel to handle their 'double' load.

Modern manufacturing process have developed 24 and 18 spoked rims capable of withstanding the massive kgF needed per spoke, that simply wouldn't have been possible when I 'were a lad'.

In essence - Less spokes = increased tension. Which in turn demands a stronger rim, otherwise you get reports of spokes 'pulling out'. And in addition stronger hubs are also required to maintain the higher tension required of the spokes.

Therefore as the spokes can only be tightened to the maximum circumferential compressive strength of the rim, more spokes won't do any damage if the tension is correspondingly reduced, and beneficially they can then support a greater load because that load is distributed among more spokes.

There does exist a 'best ratio' between the number of spokes, spoke diameter, (James's query about thicker spokes), and the cross section of the rim. And it's come about mainly by trail and error throughout the last century, to stand the test of time and that is for 700c wheels, 36 spokes will serve you best - you can still make build them faster and lighter than you ever dreamt possible - for a price, (custom wheel builders).

Besides, break a spoke on a 36 spoked wheel and you can cycle home quite safely without any further mishap. Break a spoke on a 24 spoked wheel and the others will go quite rapidly if you continue without replacement/repair.

I have been fortunate to have never suffered from broken spokes on any of my bikes that others seem to suffer from on an infrequent basis, (and I'm no lightweight), and apart from my folder they're all hand-built quality 36'ers. (Tell a lie: I once used some secondhand 32 spoked wheels designed for lightweight racing on a touring bike and snapped spokes during the tour, hence my aversion to anything less than 36 spokes).

So are 36 wheelsets slow and heavy? Not at all; one of my 60cm large-framed 'fast' road bikes hits the scales a shade under 21 pounds, (9.5 kgms), and it's fitted with 36 spoked wheels, (6' 2" and I weigh well over 200 pounds).

P.S. Almost all of my 36 spoked wheelsets have never needed to go back for a 'tune-up' or had to be rebuilt/respoked etc., (One 'fast' set has been in use on and off for over 20 years without ever needing re-truing).

 

[flecc]

So i think the stresses on a wheel are somewhat different from a battery assisted ride to the annual alottment meeting eh?

I wouldn't know anything about using allotments, but I do know what it's like to be forced into a pothole by vehicle too close in ill maintained lanes. A shock impact is a shock impact. The forces in physics have been well understood for along time, and I'm not aware that BMX has created any new ones.

Like DannyK, I don't suffer from broken spokes on my bikes, all having 36 spoked wheels which I've built or retrued.
.

 

[flecc]

That would be bikes without electrical assistance then? not the ones you are all currently enjoying? the ones using modern technology developed by jonny foreigner...

take off them rosy glasses....

That's the difference, knowing of today and yesterday, as against only knowing today.

Revised, that reads bikes without electrical assistance but often with petrol motor assistance of between 25cc and 50cc. They used the modern technology of the time, developed by Johnny Foreigner and John Bull.

No rosy glasses here, just a wide ranging unblinkered and logical view of reality, in which connection, I wonder why my adversaries in this thread avoid the crucial point I've made about fewer spokes?

i.e. What is the point when there is no advantage, as I've very clearly shown, and 36 spokes add assurance against failure?
.

 

[JamesC]

A thick spoke is no stronger than a thin spoke when used properly.... double butted gauge spokes (ie where the the thickness changes along its length) are lighter than standard gauge but just as strong, if not stronger. Thicker spokes would neccesitate larger holes in the rim and hub and weaken the wheel. Also it is the lacing of the spokes that provides the strength.... so more spokes crossing more times builds a much stronger wheel... or less spokes at a higher tension does the same but the design of the rim and hub is different. spoke under more tension are often of a straight pull design, IE no heel, or bend in the spoke. This is the weak point of any wheelbuild and modern wheelsets such as the pro connect shimano wheels run straight pull spokes to increase spoke tension and reduce spoke numbers to lighten the weight...

its a black art!

The ProConnect front wheel uses a straight pull, 24 spoke Shimano wheel.

The rear wheel uses 24x traditional 13 gauge spokes in a special pattern described earlier in this thread by Mark - radial on the non-drive side and 2X on the drive side.

As Mark says, Shimano will have done their sums to come down to the 24 spoke configuration with the Nexus hub, and it will be interesting to hear the outcome of the 50cycles report.

James

 

[JamesC]

Danny-K

Thank you very much for the comprehensive post on the relative tensions in 24 spoke wheels vs larger numbers.

I can relate particularly to the point about being able to ride home with a broken spoke on say a 36 spoke wheel having suffered a few broken spokes prior to rebuilding the front wheel of my Torq.

For info, recommended spoke tensions for the proconnect rear wheel are given here as 900-1300 N (approx 90-130 kgF) on the sprocket side, and 700-1100 N (approx 70-110 kgF) on the non-drive side.

This is quite a wide range, and it would be interesting to know whether the higher or lower end is most suitable for the ProConnect.

James

 

[Danny-K]

For info, recommended spoke tensions for the proconnect rear wheel are given here as 900-1300 N (approx 90-130 kgF) on the sprocket side, and 700-1100 N (approx 70-110 kgF) on the non-drive side...This is quite a wide range, and it would be interesting to know whether the higher or lower end is most suitable for the ProConnect..

Thanks James, that's handy to know.

The original post on this thread by Timelord complained of the spoke snapping off at the hub end of the spoke. That could suggest that the spoke 'elbow' at the head of the spoke, where it bends through the hole in the hub flange may be too long, or too sharp an angle, for the tension applied to the spoke, (a common fault when spokes snap at the hub end, and usually sorted by inserting a brass washer to shorten the excessive play in the 'elbow' of the new spoke and the flange head), or poor positioning of the spoke head in the head of the hub during assembly, too thick a flange head for the spoke used or in some cases even the way the spoke patterns cross, rather than a tensile strength issue of the spoke chosen for the wheel.

And incorrect spoke tension still can't be ruled out. Too slack and ovalisation of the hole in the hub head can result, inducing movement in the spoke head and thus eventual breakage.

 

[flecc]

The point is having a lighter bike. Which is an advantage for any kind of bike, be it a mountain, road, BMX or pedelec bike. period.

There's no "period" about it.

Advantage = 0.18% of the weight of the bike in question with a typical 70 kilo rider. At less than two one-thousandths of the weight, it's impossible to detect or measure any advantage. How does that compare with this that you said earlier in the thread, "If you fitted a 36 spoke wheel to a pro connect your going to be adding a ton of weight". In fact it would take 6363 Pro Connects with 36 spoke wheels to add that imperial ton of weight. As an engineer, I deal in facts.

Disadvantage = Less wheel strength, as you've acknowledged in giving the reason for standard BMX having more spokes. All other factors equal, the lesser strength is a reality, the advantage as shown, almost mythical.

However, perhaps you'd like to tell me of one other realistic full size wheel production e-bike ever that has had less than 30 spokes, other than the Derby Cycles Pro-Connect/Dover model. Even the exceptionally light 17 kilo sporty Cytronex-Trek e-bike has 32 spoke wheels.
.

 

[frank9755]

The point is having a lighter bike. Which is an advantage for any kind of bike, be it a mountain, road, BMX or pedelec bike. period.

No, there's no doubt it's a fashion/image thing, not about weight minimising!

The weight difference on this bike is not significant, so that is not a consideration. It may be on a professional road or track bike, but that's not a relevant comparison. You've also got to take into account the extra weight that may be needed to incorporate stronger rims to compensate for the missing spokes, so the wheel may not even end up lighter after all!

If Derby Cycles really wanted to shave every gramme of excess weight from the Pro-Connect they would be getting rid of quite a few other things including putting even fewer spokes on the front wheel (as on professional road bikes) which bears less weight and so the level of strength required is lower.

PS Crossed with Flecc's post

 

[JamesC]

The point is having a lighter bike. Which is an advantage for any kind of bike, be it a mountain, road, BMX or pedelec bike. period.

I cannot agree on this point.

For me, one of the best features of the ProConnect is the tidy linkage between the Panasonic drive system and the Nexus 8 hub.

However, I see it as a disadvantage that the final selection as to which version of the hub to use came down in favour of the relatively unusual 24 spoke hub / 700C rim. Equivalent rims are hard to find, and as discussed earlier in the thread, the wheel will always need good backup from 50cycles when rims and spokes need replacement.

Meanwhile, the Nexus 8 is emerging as a versatile hub gear, now badged as the Alfine.

Here is a good example of how well it can look in 36 spoke format, and I don't believe a bike such as this suffers badly from the weight issues of 8 or 12 extra spokes.

What it gains is a wide variety of rim choices, enabling it to be more easily developed as a tough road or (smooth) trail bike, with or without family members on board, pulling trailers when appropriate.

It is too early to worry about the 24 spoke question, let's wait and see. But if issues develop, the Alfine hub in its more traditional format is worth remembering.

The Alfine hubgear is very close in pedigree to the premium redband nexus 8 that we see on the ProConnect. It is already equipped with the right shifter and cassette system, sprocket and non rotation washers.

Launched for 2008 on mountain bikes, I would be interested to hear if the Alfine has proven sufficiently robust for this application.

Here is one review.

Next year, we might see more bikes with the Panasonic drive mated to derailleur gears. It will be interesting to see which is the better bet regarding gearing.

James

PS Crossed with Flecc and Frank's post

 

[mikepepler]

Erm, my pro-connect has 36 spokes per wheel, I just counted them. It was one of a batch that only arrived in the UK a couple of weeks ago. Has the spec been changed because of this problem?

Mike

 

[flecc]

Could well be Mike, and if so I'm not at all surprised. As you may have seen above, I've fiercely defended my judgement that 24 spokes is not a good idea on these near 21 kilo e-bikes.

The Pro Connect seems to be evolving anyway. 50cycles previously showed one photo of one with a front dynohub like the Agattu's, and that most certainly would not have been 24 spoked.
.

 

[JamesC]

Erm, my pro-connect has 36 spokes per wheel, I just counted them. It was one of a batch that only arrived in the UK a couple of weeks ago. Has the spec been changed because of this problem?

Mike

I can't answer that Mike - the spec on 50cycles web site still refers to the Shimano WH-8R25 rear wheel, which is a 24 spoke affair.

Having said that, the WH-8R25 is very hard to find in Europe so it may well be that they have started to use the more recent 8 speed hubs with a different wheel build.

Quite likely the hub will have written on it either SG-8R25 or SG-8R36 - these are the premium (redband) hubs which are usually offered as 36 spoke. The SG-8R36 is the more recent, using rollers rather than pawls in the freewheel, as can be seen here in the recent Velovision magazine via the hubstripping website.

Alternatively, the hub might be labelled Alfine which is a similar spec to the SG-8R36, but able to take a disk brake rather than a roller brake by removing the black dust cap on the non-sprocket side (I would guess that the ProConnect continues to use rim brakes).

James

 

[flecc]

This site has a photo of the 2008 Pro Connect with 36 spokes per wheel in a step through version. Click on the photo to see it clearly in detail.
.

 

[JamesC]

Erm, my pro-connect has 36 spokes per wheel, I just counted them. It was one of a batch that only arrived in the UK a couple of weeks ago. Has the spec been changed because of this problem?

Mike

Mike

Is your ProConnect the Xtra Small with 26" wheels, or one of the regular frame sizes with 700C wheels ?

James

 

[wotwozere]

Flecc

This is really confusing why you state that 24 spokes should not be on a near 21kg bike, surely the riders of the bike can vary upto 20Kgs each way no matter if they have 24 spokes or 36.

It really does not make a difference on the number of spokes so long as they are fitted correctly. This is a very out of date thought from the Guru and feel you are being overly defensive in order to save face on such a pointless thread.

thx

Bob

 

[flecc]

Flecc

This is really confusing why you state that 24 spokes should not be on a near 21kg bike, surely the riders of the bike can vary upto 20Kgs each way no matter if they have 24 spokes or 36.

It really does not make a difference on the number of spokes so long as they are fitted correctly. This is a very out of date thought from the Guru and feel you are being overly defensive in order to save face on such a pointless thread.

thx

Bob

There's no face saving involved Bob. Those who know me also know that when I need to back down or apologise for an error, I'm always ready to do so. I'm not backing down on this because so many are misguided in what they post in opposition. Sadly I keep having to repeat myself as I have to again now:

1) 36 spokes is emphatically not out of date thought when the majority of new bikes have 36 spokes and that number is near universal on e-bikes. This is after all an e-bike forum. It's the higher priced lightweight race style bikes that sometimes have less, and no e-bike can be classified as being one of those

2) Rider weight is to some extent sprung weight due to the body's absorbency of shock, only the bike weight immediately impacting on the road wheels. This is particularly relevant in BMX which dienamics didn't seem to understand. When stunting on BMX, the rider is up on the pedals with knee and hip joints angled as a shock absorbing cantilever. Despite little of the rider's weight directly hitting the wheels, it's still thought desirable to have 48 spokes.

3) If it really makes no difference how many spokes there are as you say, why don't BMX have less than 48, why do any bikes use more than 24? That's not confusing as you feel, it makes perfect sense to have a rim adequately spoked for the use involved.

4) The opposing posting is very centred on sport bike practice which isn't relevant here. E-bikes are not race machines, being used predominantly as utility bikes and commuters, very few solely for leisure. E-bikes are much heavier, often carry heavy loads and sometimes do heavy towing.

5) If fewer than 30 spokes is all that are needed, why is the Pro-Connect/Dover alone in that out of all the e-bike models in the world?

6) Your comment on not mattering if the spokes are fitted correctly I've also previously answered. In this imperfect world they won't always be, and that's why the more forgiving 36 spoke standard is desirable, especially when as I've so clearly and repeatedly shown, there is no advantage in fewer. As James has observed, there can be disadvantages as well to having fewer.

7) Do the opposers even have e-bikes? I rather doubt they all have. This is relevant to their thinking if all their experience is of unpowered bikes.

8) This is a members forum where all are entitled to express and defend opinions. When faced with something one disagrees with, the options are to disagree or leave the thread. Advising someone else to stop expressing their opinion isn't a very acceptable option.

Now if someone wants to disagree, please can they do it by showing me how what I've said above in each point is erroneous, not by constantly repeating previously answered errors.
.

 

[wotwozere]

Flecc

I really do not understand what you are getting at, are you saying that no ebikes should ever have less than 36 spokes, why can you not grasp that it makes no difference. Are you saying that a wheel with 36 spokes has never snapped in the history of wheels? Have you ever had a spoke broken on any bike either electric or not? If so how many did the wheel have.

Do you have any scientific proof that 24 spokes is not good for a bike, how many wheels and spoke combinations have you tested in your entire life, I fine it hard to understand your judgement when you seem to have no experience with any wheel except a 36 spoke type. I think it is time to concede to common sense and admit you are wrong.

Please do not eat yellow snow

thx

Bob

 

[flecc]

Already answered Bob. For a given set of component quantities, more spokes are stronger than less spokes, and the rim is supported more evenly throughout the arc, both facts.

Those are the advantages, but there are as I've so clearly shown, no realisable advantages to having less on our kind of bikes and sometimes disadvantages, so why use less when it's not as strong.

So why don't you admit you are wrong, since it's clearly me stating relevant facts in support and you only making statements without supporting them.

I did say please when asking that disagreement should show in what way my points were wrong, but once again you just repeat the same error again which had been answered in point 3 above and previously. i.e. If it makes no difference, why do BMX bikes and some load carrying types have 48 spokes, and why are the great majority of all bikes and virtually all e-bikes using 36 spokes?

Are all those worldwide bike designers mistaken? I think not.

As others have said previously, bike design was pretty well settled after 100 years of the "safety" bicycle and we too often seem to be in an age of fashion and gimmickry just for something fresh with which to sell bikes and extract ever larger amounts of money from customers, regardless of whether it's better or worse for them. You may be taken in by some of this, but I'm not and no-one will persuade me to be.
.