Folding Bikes - Another broken spoke! Advice?

Background - I have a Downtube Mini which I purchased in last year for a daily 11 mile commute along a smooth, flat MUP in Manhattan. Until recently, had no problems with the wheels. Then, about a month ago I broke a spoke on the rear wheel. LBS repaired it. This week I broke another, bent one. LBS repaired again. But now I am getting concerned.

This is a small bike with ISO 305 rims, running the stock Kenda tires at 60PSI. It has the Sturmey Archer XRFD8 IGH - so the spokes are VERY VERY short. I am no lightweight at 200lbs, and the bike has a rear rack loaded with about 15lbs of gear for work.

I have replaced the stock coil spring suspension with a hard elastomer - the suspension now feels locked up most of the time. wonder if this is causing trouble. (Note; the first spoke broke before the suspension replacement)

What's my best option?

New tires - Schwalbe Big Apples would fit, but would they help?
New wheel? Rebuild wheel? - ISO 305 rims are hard to come by. Peter White lists Aeroheat 305s on his website.
Shut up and ride? Fine, until I break another spoke..

DT Swiss. nuff said.

I had a similar problem with my Dahon P8.

I just had it rebuilt with stronger spokes.

Apart from fixing the wheel move all the extra weight to the front of the bike. Rear has got enough to deal with as is.

Fat tires, not to hard (low PSI).

Sprung saddle, thudbuster or similar.

Go back to softer elastomer. (Maybe all of the last theree is not needed).

I learnt some time back that any suspension on a bike helps "saving" rims and spokes. The (old) person saying it said that the best suspension for a bike is the fat tyres and sprung seat.

My friend had this problem, holydaying with a cheapo 16" bike. Had all his stuff in a backpack, jumped curbs and did not think about spoketension. After several broken spokes he "woke up", bought a City trailer for his stuff and stopped jumping. Payed more attention to wheels. Doing fine now. (Not suggesting you are jumping with a backpack).

What spokes does your lbs uses? Does the mechanic check the spoke tension by hand or with a tension meter?

Also, what lbs do you go to? I am looking for one in NYC that cuts small spokes. Thanks.

According to the website, the maximum rider weight is 215 lbs for the Mini. So perhaps you can lighten the load. Can you leave some of that stuff at work and not transport it?

DT Swiss. nuff said.

and if you want real good ones than take Sapim with polyax nipples

thor

i have little experience with small wheels..but it seems you need fatter spokes...industrial strengh like husky wheels

no
..... it might help to a point , but usually the problem is that the spokes are loose and than break ( at the neck )
there are two kind of spokes ....
A.Sapim, DT, Wheelsmith ( in that order )
B. all other which are junk ...



on small wheels the nippels hava fundamental importance as well.... Sapim polyax nipples are rounded at the bottom ( where they contact the rim) and they " point" better in the direction the spoke pulls... if your nippel exit straight ouf of the rim and than the spoke is bend sharply to the side, thats a weak point ....

the spoke will try to pull straight and will suceed over time, therefore it gets to loose and than breaks

...

the other problem is that on small wheels the angles are so much steeper than on a big wheel ... dia of the hub remains the same ....Spoke heads are bend in a certain degree ...usually for all wheel its the same. Sapim indeed has spokes which have a more promonced bend for small wheels

on sub 1000 dlr bikes sometimes the hubs are not necessary the very best available , therefore the hubs might or might not have very accurate hole diameters .... and in that case a larger dia spoke will indeed help as it will fill out the hole much better and therefore will not flex as much ....

we do have the Sapim Strong spokes which are 13 ga ( 2.34 mm) at the bend and 14 ga ( 2 mm) the rest of the spoke .. those can be cut easy to come up with indeed a stronger spoke ....


the whole crux to the matetr is that no matter what spoke if it is too loose than it will break. keep them nicce and tight and you look at a wheel which will last a long time

thor

the whole crux to the matetr is that no matter what spoke if it is too loose than it will break. keep them nicce and tight and you look at a wheel which will last a long time



+1

Given the pattern of breakage that OP describes, it sure looks like loose spokes was the original problem. It also is likely that some of the other spokes on the wheel are also compromised from flexing due to looseness. I'd replace all of them at once.

no
...


the whole crux to the matetr is that no matter what spoke if it is too loose than it will break. keep them nicce and tight and you look at a wheel which will last a long time

thor

great post!:) thanx

I took the bike to my LBS yesterday. They replaced two broken spokes and trued the wheel. Well, mostly trued. It's perfect side to side but has a slight vertical "hop" that is visible if you spin the wheel freely. Not sure if this is anything to worry about. My LBS is one block from my house and they have the machine to cut short spokes - very convenient. But it's a busy shop, and you never get to talk to the mechanics face to face. Everything is communicated thru a salesperson. If I break another spoke, I'm going to get all the spokes replaced - probably somewhere else, where I can talk to the wheelbuilder.

If rim is not round(vertical hop ) then it can not be trued. It may be worth investing in a new rim,as the spoke tension can never be equal?

The stuff about suspension preventing rims damage,yeah,but if you hit a big bump your weight needs to off the seat ideally regardless. This does not mean you need to stand but you need to unweight the rear wheel seatpost ect to absorb some of the shock. There is a limit to what suspension can do if the rider is giving the bike a hard time by overly relying on it.

If the rim is bad then I am in trouble.

I've been trying to find a source of 28-hole 305 alloy rims for awhile - ever since rhm wrote of his troubles finding a replacement for his Mini. Downtube doesn't have any. (He actually bought a whole other bike (http://http://www.bikeforums.net/archive/index.php/t-514269.html) on eBay just to harvest the rims!). Velocity lists 305 aerohead rims on their website but when you contact them they say that they haven't made them in a long time due to lack of demand. Niagara Cycles has one (http://www.niagaracycle.com/product_info.php?products_id=30300) but it's a single wall rim - probably not a good idea!

Your spokes are breaking because they were not tensioned right. The ones that are the most fatigued are breaking first, but most likely they are all fatigued and sooner or later they will all break. You cannot know which are fatigued and which (if any) are not. Replace them all.

Lucky you, I happen to have a rim I'll sell you for what I paid for it, since I had to replace the hub not long after I replaced the rim! It's a somewhat better rim than what the Mini came with. In fact, I'll throw in the spokes, which are virtually new.

I don't believe you will need to replace the rim (yet). You can replace all the spokes yourself (costs time), or you can have your bike shop do it (costs money), no matter. I can give you the email of a guy who cuts custom spokes, quite cheap. I don't believe the quality of the spokes is nearly as important as getting the spoke tension right.

rhm's explanation fits the symptoms perfectly - no trouble with spokes for the first ~ 700mi, then spokes start breaking, even though I'm doing the same commute. I've pm'ed about the rim - thanks!

The stuff about suspension preventing rims damage,yeah,but if you hit a big bump your weight needs to off the seat ideally regardless. This does not mean you need to stand but you need to unweight the rear wheel seatpost ect to absorb some of the shock. There is a limit to what suspension can do if the rider is giving the bike a hard time by overly relying on it.

Absolutely. I only talked about the hardware, but knees (also resting more on the hands) are serousely important shockabsorbers too.

I put a sprung saddle on my folder today and really felt the difference. more comfy for sure.

Where on the spoke are the breaking?

If at the J-Bend, likely the problem is low tension. If at the threads, it is more likely a result of bad spoke angle, something that is not easily corrected, as the only real option is to build these wheels 1x. Using Sapim Polyax spoke nipples (with the rounded head) may help deal with bad spoke entry angle at the rim.

Where on the spoke are the breaking?

If at the J-Bend, likely the problem is low tension. If at the threads, it is more likely a result of bad spoke angle, something that is not easily corrected, as the only real option is to build these wheels 1x. Using Sapim Polyax spoke nipples (with the rounded head) may help deal with bad spoke entry angle at the rim.

The first spoke break was at the J-bend.

The second spoke break was not at the J-bend. Not sure where it was. Happened when I was cranking away, thought I ran over a branch or something. By the time I stopped several miles later, half the spoke was gone, the other half was mangled by the chain.

The first spoke break was at the J-bend.

The second spoke break was not at the J-bend. Not sure where it was. Happened when I was cranking away, thought I ran over a branch or something. By the time I stopped several miles later, half the spoke was gone, the other half was mangled by the chain.

So, it broke somewhere in the middle? :D

Yep loose spokes will break every time.

no
..... it might help to a point , but usually the problem is that the spokes are loose and than break ( at the neck )
there are two kind of spokes ....
A.Sapim, DT, Wheelsmith ( in that order )
B. all other which are junk ...




Completely right. The only problems I ever had were on small wheeled bikes with ill-tensioned spokes. I weigh about 165 pounds and can still break spokes if the wheel is not tensioned right. I had a spate of breakages on my Merc when I first got it and have broken about 7 in the cheapy strida clone. I may buy a strida back wheel for that bike because I am sick of replacing them and I know that will fix the problem. It is really mainly about the quality of wheel building, but better spokes would also help obviously as long as the wheel is properly tensioned as well.

I've had some spoke issues with my wheel, too. Not a small wheel, but a very large hub, meaning relatively short spokes, so some of the issues are similar to small-wheel issues, and, of course, some spoke issues are the same no matter what size wheel you have.
1st issue was that I went with a 2 X patter and ended up with too sharp a spoke angle, like K6-III said, and had spokes break at the nipple.

Rebuilt with a 1 X pattern. All seemed well, but after a month or so, those started breaking at the hub. I noticed, as I was replacing the spokes, that there was a relatively severe bend where the spokes crossed. I expect the spokes to bend around each other a little, but this seemed to indicate some unusual stresses on the wheel (to me, anyway. I have not built many wheels).

I used DT Swiss spokes both times. When researching to respoke, I found two interesting tidbits:
1) Peter White has some interesting things to say about changes in DT Swiss spokes a few years back (link (http://www.peterwhitecycles.com/DTspokes.htm)). Short version is that the bend has become more severe, which Peter suggests could cause breakage at the bend if used without spoke washers, which is exactly my problem.
2) My hub specs state (and I should have read them more closely, but was working from my old, 2 X instructions, and just modifying them for 1 X) that if you're doing a 1 X pattern, you should have all of your spokes exiting the hub flange from the same side, not alternating, like a normal 2 or 3 X build. Seeing the way the spokes bend around each other on my build, I can see the sense in this. A 1 X pattern crosses spokes much closer to the hub, where they are still on slightly different planes from having exited the hub flange on opposite sides.

I'm guessing that stress of too severe of an angle at my spoke crossings, combined with not using spoke washers with the DT Swiss spokes, resulted in far too much stress at the spoke where it bends into the hub flange. I now have a new set of Wheelsmith spokes, so we'll try all this again. This time following the manufacturer's specs on how to do a 1 X pattern using their hubs.

All of this is a long winded way of saying that if you're considering a wheel rebuild (and it sounds like maybe you should -- once a couple of spokes have gone, it's usually just a matter of time for the rest, especially if they were poor quality spokes to begin with), and are breaking spokes at the bend where they pass through the hub flange, you might consider DT Swiss with spoke washers or consider a different spoke, and if you're going with a 1 X pattern (which, unless it's what you already have or your spokes are breaking at the nipple, I would not), you might get some further advice on the proper wheel build for your particular hub.