elcruxio

So I've been battling with this problem for a while now. While I can't do much about it anymore as all the gear is already bought and paid for (and the rear wheel was not cheap with a Hope hub and steel freehub body as addon) I'd like to discuss this topic theoretically and for future reference if do need to get a new wheel on the road.

As the title suggests, is 36 spokes really enough even with modern components?

So whether you have experience about the matter or know more about the actual theory all information would be greatly appreciated.

For middle weight people (under 80kg) a 36 spoke rear wheels should be quite enough even in 700c wheel sizes as it's unlikely they'll get their whole rear load over the tension of of single NDS spoke even with a very loaded rack due to weight distribution of the rider on the bike. However I'm at the moment 107kg and while I could lose a few kg, 100kg starts to be at the limit what's healthy for me due to too low body fat (I'm also 6'5" and relatively muscular and as a type 1 diabetic I'd like to keep as much muscle and some body fat around for cases of serious infections as even the common flu is much more serious for me than for the average joe).

This means that with a calculated rear load of 20kg (an absolute max weight limit I pulled out of a hat since I have no idea how much it's really going to be, likely not nearly that much) and my hefty body weight I'll weigh the rear wheel down at about 97kg, which is 15kg more than the average tension of my NDS spokes.

As we all know the weight put on the rear wheel is taken up by the 4 lowermost spokes in a 700c 36 spoke wheel and probably a bit more even with the spoke that's directly under the hub. This'll mean that I'll detension each spoke by at least 25kgf which will in turn drop the NDS tension to 57kgf every time the wheel spins around. This is actually pretty standard road bike NDS tension, and it's fine when on good tarmac, but riding bad roads and gravel roads in the balkans (and why not other areas as well) has me a bit worried. Doesn't take much of a bump to compeletely detension those NDS spokes when travelling at speed, especially when the luggage can't unweigh itself. Of course the lower the rear load and the better the rider, the more these stresses can be reduced, but there are times when there's no chance to properly avoid stressing the wheels (accidents and road curl)

I think the rear wheel build is really solid with probably less than 5% tension deviation between spokes (thanks DT Swiss, you're the best) and the NDS tension at 82kgf with DS tension at 135kgf, a heavy duty rim that weighs over 500g and triple butted spokes. The wheel has gone throught at least 5-6 stress relieve cycles (after everly cycle of tensioning in the build phase) as well as some other Voodoo I learned from Psimet (not directly, had to dig around a lot). It has also survived a lot already (albeit mostly without loads) and is protected by a 37mm tire which should have enough bounce to it to reduce the G force directly to the rim somewhat. But still can't get through this nagging feeling that it's not enough for a guy my size.

Why I didn't go for a tandem rear hub was mainly because when I built these wheels I had an aluminum frame which I ended upgrading for the LHT and didn't at the time want to A) pay over $300 for a DT Swiss rear hub and B) didn't want to cold set an aluminum frame that much. With the LHT it could be done but that would wreck the chainline and would require some fiddling to get right.

Now that I've gotten through my overly long intro to the subject, all experiences are welcome and especially if you weigh close to what I weight and have survived with 36 spoke 700c wheels with touring rear loads without breaking spokes I'd really like to know. And if your wheels haven't survived I'd also like to know. Just also give some details on the build (builder or machine built, which spokes, rim etc. if you can remember). Like I said, not much can be done before the honeymoon tour, but if the situation seems catastrophic I'll just borrow a bit from my soon to be wife and get a new rear wheel with 40 spokes or more. I'll have to sell the old one but I think there will be takers for a handbuilt touring wheel of this caliber.

robow

Can you help me with your math, you weigh in at about 105 kg, plan on carrying maybe 20 kg more, but feel the rear load will be in the area of 97 kg?
Does that mean you are intending to put 28 kg up front which would be more than most front ends would want to handle?
Is pulling a trailer completely out?

bikemig 

There are a lot of people who have ridden a lot of touring miles on 36 spokes. That said, 20 kg is a lot on the rear but it sounds like you're going to areas where you might need some extra gear. I think robow's idea of a trailer makes a lot of sense if that works for you.

I also think this is an area where some actual experience is worth more than a bunch of measurements. I'd take that bike out on a local shakedown cruise with all your gear and on some really bad roads to see what happens.

How fat a tire are you using?

gauvins

I am not an expert, nor a Clydesdale. Three things:

1. The definitive work on bicycle wheels can be downloaded here (Jobst Brandt)

2. 36H appears to be more than enough.

3. You seem to suggest that the weight is supported by the spokes that are under the hub. Actually, spokes work in tension - - it is the spokes that are above the hub that do the work.

imi

Do you ride "actively" over bumps 'n such? i.e float off the saddle...
I reckon that would make a huge difference to the momentary force on the back wheel.

I ride like that an' I'm skinny with a fairly light load

edit: that said a well built 36h wheel with quality components (Alpine III spokes?) is pretty bombproof.

Squeezebox

Congrats on getting married! I wish you happiness.
You mentioned your wt. the bicycle weighs about 30 lbs. What weight for the racks, bags , gear are you thinking about? Sounds like you're in a somewhat similar as me. ie. being under-spoked. I agree with using what you have. When it gets to be a problem find a solution. Wont hurt to look around now, so you won't get into an emergency situation. i'm gonna plan for a stronger rear wheel. You could talk to some of the tandem places for a stronger rear wheel, even if it does not have more spokes.
We have slung too much monkey poo at each other, I wish you happiness.
Also there is an American pro team, made up of all type 1 diabetics. Team Novo Nordisc, I believe. Check in with them for some of your medical advice.

elcruxio

Nope, about 35% of my bodyweight is carried by the front wheel, which means that when the bike is unloaded the rear wheel is supporting give or take 78kg (not a calculation, I measured this with a scale)
Trailer is out of the question since those are expensive and I hate pulling those things. Can't abide them. Horrid devices. When we get kids we're getting cargo bike or two instead of kiddy trailers, that's how much I hate them.

The rear tire is 37mm wide, which is almost at the LHT fender limit and incidentally is the fastest marathon plus width.

The Jobst Brand book actually explains the thing pretty well. The spokes one needs to be worried about are the ones on the bottom of the wheel as those go slack when weight is put onto the wheel. If the spokes lose enough tension to go even a little slack the resulting tight/slack/tight/slack cycle starts to fatigue the spoke which in turn will break them. So the wording "bottom spokes support" is incorrect, it also defines which spokes are the most important in the functioning of the wheel.

Spokes have tensile strengths several times that they ever face in the normal life of a wheel so the top spokes and other spokes which tighten when the bottom spokes slacken are in no trouble whatsoever.

I try to ride the bike as gently as possible following the very wise MTB saying "light hands, heavy feet". But that said even I sometimes unintentionally bomb into curly gravel road sections or holes in the road.

The spokes are Alpine III's which give me confidence, and the rim is DT Swiss TK540, which is relatively wide and should be extremely stiff as it's beefy, double walled and double eyeleted.

mstateglfr 

I am the same height and basically the same weight as you and have a 36 spoke wheel on the bike Ive used over the last couple years when packing heavy. Disclaimer though- everything Ive done in that time has been shorter 2-3 day trips, so nothing where its day in and day out riding for a month or more.
The wheels are Sun CR18 rims laced with straight gauge spokes attached to lowly(relatively speaking) Shimano RX100 hubs from the '90s.

Each time Ive loaded up the bike, there has been 28-35# of gear on the rear. In addition, I either pull a trailer with about 60# of gear or I have a 45# kid plus 35# weehoo(trail bike) attached to the seat post. I dont know what the trailer or weehoo add in terms of stress to a wheel since they connect to either the rear drop out or the seat post. I mention both because I would imagine they add some sort of stress and probably in multiple directions.


Ive never had an issue with the spokes and they are still well tensioned and the rims are true. I have done nothing to them over the last 2 seasons except clean off gunk from time to time.
Being the same height and weight as you and carrying the same weight or more(when adding in force from whats being pulled), I would think your really great rim+hub+spokes will be OK.

Again though, my overloaded trips have all been 2-3 days each so perhaps repeated daily riding for a month or more would change things.


Looks like you estimate rider weight at 70%back/30%front. Ive read anywhere from 60/40 to 70/30. But at worst, you are estimating on the high end, so thats good.
Any chance you could load some of the weight up front to reduce the weight in the back?

bradtx

elcruxio, Fundamentally, the wheel supports the bicycle weight from above, like a suspension bridge. Each spoke above the axle supports a portion of the weight. The spokes directly below the hub, for lack of better words, go slack. Spokes to the side are working to maintain alignment.

20 kg strapped onto the rear rack will be tough for any wheel, IMHO. Use front panniers for the majority of weight and the rear for the bulkier items. A trailer is also a viable option. Carrying or towing less weight is an even better option.

Brad

fietsbob

tl;dr consider: less OCD, tech, more marketing awareness.

Could go 48 spoke, (I did) but 36 [modest Shimano hub] chances a bike shop will have a spare wheel to sell you on the spot
is much more likely.

Now got The Money? 36 hole Rohloff 3 cross .. bracing symmetry, is better than dishing for wide cassettes.

They made the 36 after so Many people mounted the 14 speed IGH on tandems, riding gravel roads

then cracked a Hub flange On a long tour in Bolivia Or Peru.

Tourist in MSN

Nobody has ever accused me of being an ultra light bike tourist. I probably pack a bit heavier than you and weigh about 80kg. SO, I have a little less stress on my rear wheel than you, but not that much less. I use 36 spokes on the rear on two different touring bikes (one is 26 inch, the other 700c) and have had no problem. I think you should continue to use your wheel, carry spare spokes and the tools to put on a new spoke quickly if one goes. If you pop three or four spokes, then it may be time for a new wheel.

If you could fit a wider tire for more cushioning, maybe consider that too. You did not say what pressure your rear tire is at, but you want enough pressure to avoid pinch flats but not too much pressure as at too high a pressure you add stress when you hit a bump. And too much pressure can cause a rim to split.

Occasionally you might want to carefully inspect the rim for cracking at the spoke nipple holes, that might happen before any spoke failures.

elcruxio

I'll be putting the heavier stuff up front and as I mentioned the 20kg is a worst case estimate. Likely one rear pannier is going to handle sleeping stuff, the second pannier is going to take clothes and the rackbag is taking half of the tent and all of my medical supplies (1000 syringe needles for one, there's other stuff as well)

elcruxio

I have considered a wider tire but that would mean that I'd need a new set of fenders, which while not all that expensive is still a hassle. The tire I have should support 115kg according to Schwalbe Germany. The tire and the rim both have a Max Pressure of 6bar, but following one of Psimet's tech tips I should get away with 5.5 Bar in the rear.

gauvins

I ride a LHT mounted on Schwalbe 2" (motivated by several factors, including the likelihood of riding on gravel tracks, the tolerance to lower pressure and expected durability). I've installed SKS trekking fenders because they can be easily removed, which is not a trivial consideration if you must fly your bike. Replacing your fenders might be a good idea, irrespective of the type of tire you'll use.

I also remember reading that a suspension seatpost or suspension saddle reduces the amount of stress transmitted to your wheel (and your rear end).

Have a great time.

LeeG

Nagging feelings are no fun but they aren't the wheel. If you picked a robust rim and built it well you covered the bases. Ride the hell out of it and if failures occur related to rim not holding up, get a beefier rim. What rim do you have?

elcruxio

Dt Swiss TK540. I'm guessing it should be enough since DT Swiss rims are apparently strong enough for DH with no tire Aaron Gwin no tyre Leogang UCI DH World Cup

Salamandrine 

You should be OK, especially with the 37c tires, but a lot depends on your riding style and skills. Some people are very careless and don't know to lift their butts out of the seat to go over a bump, ride through curbs, and just generally have bad riding technique. This actually matters more than weight. Butted spokes and a deep strong rim will help a lot.

That said, you are sort of on the cusp of where thinking about more spokes would be a good idea. 20-30 years ago, I'd have probably told you yeah, go to 40s, 48 in the back if you ride like a gorilla. Nowadays, I'd say try it, pack light, and ride carefully. Camping gear is lighter than it used to be.

fietsbob

Bring a Credit card , carry very little if your tastes are focused on light weight Expensive parts.

indyfabz

I've toured at about 215 lbs. (body weight) with probably in the neighborhood of 50 lbs., including racks, panniers and gear. 36H stock wheels on my heavy, 60cm LHT have performed flawlessly, even on rough, unpaved mountain roads. Alex Adventurer rims and Conti Top Touring II 35c tires.

LeeG

You're fine. Ride it till it wears out or crashes tweak it. But for kicks and giggles to allay your anxiety build up the cheapest rear wheel as backup, $20 Shimano hub, straight gauge spokes, Velo-Orange Escapade rim. Five years down the line after many tours a car backs into your bike trashing it and you'll have your backup wheel ready.

https://store.velo-orange.com/index.p...apade-rim.html

LeeG

I would love to see comparative testing of expensive 540g rims compared to inexpensive 620 gram rims. Then there are the 700g-800g Rigida touring rims. Seems to me the consumer market is biased towards lightest rim for any particular application whereas tourers carrying 30+ lbs have pretty much gone into an application where the difference between a light rim and a very heavy rim is not noticeable for the motor. The bike has become a truck.

FBinNY 

IMO a well built 36h wheel using butted spokes should be more than adequate. The key here is "well built". I've toured extensively and find that the cargo counts more than the rider because it's fixed weight, whereas the rider can lift his rear off the saddle and let his legs act as a suspension on bad stretches.

himespau 

Can you take it for an weekend fully loaded to try and see how it works as is?

elcruxio

I did a test count and the absolute worst case weight I'll get on the rear wheel is going to be 16kg or 35lbs. That's of course with full water bottles in the rear triangle and fully stuffed rear panniers. But with the rear packed full I notice I don't have all that much stuff left to stuff into the front pannier so it would seem that I'll stuff the front first to 10kg and see what's left for rear. That'll free up space in the rear panniers for groceries and extra water if we'll need it at any point.

elcruxio

Done that already. The rear wheel was freshly built so I was expecting some 'life' in the components. It was a gravel tour so most of our riding was on less than optimal roads, but mostly good conditioned hard pack gravel. The rear went out of alignment by 0.3mm on that trip and I've since tightened it a bit more since it would seem the marathon plus I have mounted has some considerable effect on spoke tensions.