Rear Wheel issue...or is the bike at fault?
 

Hi all,
This all started at the Clydes forum, because i assumed my 240-250lb bulkiness was the culprit....http://www.bikeforums.net/showthread.php?t=553984
Since then, i had a new wheel built up by my lbs for my '07 Trek 7.2FX...
It's 36h 14g straight guage spokes, decent Shimano hub, and Sun Rim CR18....

Ok, i've been in the shop several times with truing/popped spoke issues (mostly drive-side spokes) with this new wheel, and, although i feel confident that they are doing the work properly(with pre-stressing/tensioning/re-truing, etc), I still am getting grief from this wheel :crash:

So my questions to you all (especially anyone knowledgable with Trek and their workmanship)

1. Could the BB/Chainstays be flexible(weak?) enough to cause abnormal torsion on the rear wheel? I've built up quite a bit of power in my legs these past few months, and it seems most of my problems happen after crankin up a steep hill...I don't mash nearly as much as i used to(last fall)...i usually stay in the middle (38T) chainring and the lower gears for most of my pedaling (my cadence is usually above 75RPM) I keep it in the lowest comfortable gear possible just to keep my legs spinning and cardio up.

2. Could it be the 28mm Gatorskins pumped to the recommended 95psi causing more stress to the wheel--->transmitted to frame--->back to wheel...This is a low-end bike(but when everything is perfect it rolls very well)....I used to have the stock 35mm tires with about 80psi(and of course, no wheel problems until I put the 'Skins on)

Could it be a factor of the two? I need your help guys, because these headaches are making me to want dump this money pit onto craigslist and save up for a hard-core bike that will give me alot less headaches...My lbs has told me they have never seen this problem (they also suggested that it could be the bike and/or choice of tires/psi)

Whew....long winded post, I know :notamused:

Are the nipples brass or aluminum? I would try brass if they're aluminum. My though is that your new, less forgiving tires are causing stress fractures in the threads of the brittle aluminum spoke nipples. When you then power up a steep hill, they sheer.

By "popping" spokes, do you mean breaking at either the head or threaded end? or, "pinging" that is associated with stress releiving?

Second question, have you ever dropped your chain off the the inside of your cassette and jammed it between cassette and spokes? If so, that will certainly contribute to spoke failure in short order. A derailluer stop screw adjustment can stop this.

P.S.

Do they (your LBS) own a tension meter? Many guys will swear they can tension by tune but few really can. This can be a real issue, especially when you're trying to run spokes at their or the rims highest suggested tension. If they don't have a tension gauge they'll be hard pressed to consistently and accurately hit the correct tension for a clyde wheel.

Just reread your Clyde thread. Plucking is at best a gross tuning method unless you're extremely skilled. Realize that drive side and non-drive side will have grossly different tension due to the required dishing of the wheel. On used wheels I tend to be more concerned with maintaining reasonably even tension and except that may not result in perfect true. If doing so, results in true that is so far out as to be unridable, it's probably time for a new rim. Trust me, many of us have experienced the very issues that you're going through. When I relocated to Auckland I interviewed not less than a half dozen shops and/or mechanics before I selected one that I would trust with my wheels. There is hope at the end of your tunnel. Eventually, you'll find a rim/spoke/builder combo that works for you and then you'll be hard to convince to change.

Bigfred,

Yes, they own a tension meter, but i was told that they can do it by feel (since they've done it so much) at least that's what i'm being told...i was well informed by them about the drive-side versus non-drive side tension differences and they said it was proper tensioned...myself being one to question everything had researched their choice of rim (I am on a budget) and found that most people who had good luck with that particular CR18 had to keep the spokes tighter than usual to keep the wheel trued....i still want to think that the wheel is the issue, but the stock rim was fine till i mounted the gatorskins....then i started popping spokes....as for the new wheel, the last spoke that popped(my misplaced term for breakage, sorry for the confusion :innocent:) broke at the head instead of the usual breakage about a quarter-inch up from the head. and i'm proud to say i never dropped the chain between the spokes and cassette in the manner you described....yet <knocks on wood>

And the nipples are brass, salaCzar.

Strange that you had problems after changing tyres on your original wheel. What size tyre and pressure are you using? When I got back into cycling 3-years ago, I weighed 245-lbs and hopped on my 15-year old training wheels (Shimano 600 hubs, 36h 14ga spokes, Mavic MA-40 rims) and had no problems. Those wheels already had 50k-miles on them as well.

If your new wheel AND your original stock wheels are breaking spokes, then there's something in common between them. We should try to determine what that is.

Also any shop that say they can determine spoke-tension by feel is full of BS!!! I've built over 200 wheelsets and can tell that it's impossible for a human to determine exact spoke-tension by feel or sound. Take the wheel back and make them measure the tension on each spoke and entre it into spreadsheet for you. Analyzing the overall tension as well as tension-variations between spokes on each side will tell you A LOT about the quality of the wheel-build.

As for failures, breaking at the head is typically a fatigue failure. The crack is perfectly clean and the two parts can be re-assembled to fit perfectly. A forced break that overcomes the ultimate-strength of the material will often be 10mm away from the head and will show signs of distortion and stretching of the material. The crack will also not be symmetrical and can't be re-assembled cleanly. What kind of break do you have?

O.K.

So, do you know what brand the spokes are? Wheelsmith, D.T., etc.

If you don't have many miles on the wheels and the chains never been dropped, the first thing that comes to my mind is that the spokes may be over-tensioned. It's true that clydes will normally want tension at the upper end of the allowable spectrum but perhaps you LBS has gone a little too far.

Really, a set of shimano hubs(just about any of them), Sun CR-18's and quality name brand 14ga. spokes should build up into a reasonably durable wheel for someone your weight. I'm putting my money on excessive spoke tension, which can also cause a wheel to exhibit truing issues. As the excessive tension attempts to cause the rim to assume the shape of a potato chip.

I'd try a wheel with an offset rim. I dont know what rear spacing your running but a 135mm OLD with an offset rim may result in a ZERO dish wheel which in turn will help with tension differences left to right.

IMHO tension meters are over rated. So what, its properly tensioned according to meter....and your still breaking spokes. What do you do then?

What most people dont realize is that 700c wheels are the same diameter as 29'r mountain bike wheels. Why not find a nice 32H or 36H 29'r wheel?

I weight 260 lbs and I built my wheels (alex DH22 rims:love:, 14G DT Spokes, Shimano Exage hubs) about 3 and a half years ago and have had no problems... I average just less than 30km/h (maybe 18mph) on rough roads with 700 X32 or 700 X 35 tires pumped up to about 85psi. I beat the Sh!+ out of my wheels and they have not detensioned or broken a spoke yet. Probably 3000 km on these wheels so far on a rigid aluminum frame.

I have the same rim and spokes on my road bike (on and older 105 hub) and have a few thousand kms on that one with 700X23mm tires pumped to 115psi. THe previous wheel on my road bike was a colnago-branded Ambrosio (sp?) with 14G spokes... years of trouble free service on those ones as well. By the end there were just too many dents and dings from potholes and getting doored by cars, but I never broke a spoke.

I did break spokes on previous wheels, though.. and they were all wheels built by someone else... I starting building my own wheels knowing that I needed higher tension for durability.

My advice to you: Get a truing stand and a tension meter, and check your wheels periodically to make sure the tension is in (or slightly above) the upper end of the reccomended tension range for the rims. Learn to true, and ultimately, to build your own wheels... then you will never have a question as to how even or how high the tension is, and you will have no-one to blame if it goes wrong.

if the tension is good, and you're still breaking spokes, more spokes, thicker guage or DB/TB spokes.
there is also tie soldering the spokes.

Sun CR-18 is rated for touring/29'er, it's a good rim.
the only rim with offset in this width that comes to mind is the velocity synergy.

usually you want an off center rim to equalize the tension for the non drive side, which is more prone to fatigue breaking spokes, since they are looser.

We just had an interesting discussion on this in another list... some advice from a trusted mentor & wheelbuilder:

Wheel strength is determined first by spoke tension. The wheel can only carry as much weight as the tension in the spokes that it is STANDING on. If the spokes on the bottom of the wheel are slack, your wheel falls apart. Your bike wheel is NOT hanging on the spokes, it is standing on them. In fact almost all spokes break because they are not tight enough. The nipple and the rim will fail from over-tension long before the spoke breaks.

Having more crosses in your spoke pattern spreads the work among a larger number of spokes (and therefore the total tension available to keep the wheel together).

Tandems use more spokes for several reasons. More spokes mean that you can cross them more. A 48-spoke wheel can go five-cross. So the number of spokes that take the load can add up to nearly half the wheel! 36-spoke wheel can be built up to 4-cross, so it holds a heavy load. 32-spoke wheels are limited to 3-cross.

Trying to overload a rim and over-tension can lead to catastrophic failure of the wheel. So, more spokes makes more sense.

the spokes won't share a load if they aren't weaved. in a 3x lacing pattern, that means there is only one other spoke that shares some of the load.

One cylindrical steel thingy, lightly pressed against another cylindrical steel thingy - really isn't much to work with to transfer axial load from one to the other with.

Only benefit from weaving that I can see is that as torque causes one to slacken the same torque will cause the other to tighten, and due to the interlace preventing them from running straight between the end points this will do some good in terms of keeping the tension up in the spoke that would have gone slack otherwise.

how about tie soldering it?

or you can weave it like this:
http://www.instructables.com/files/d...TC.SQUARE2.jpg

You should aim for even tension around each side of the wheel. The instructions with the Park tensiometer say the tension of all the spokes should be within 20% of the average. However dont have the max tension spoke next to the min tension one, tweak the tensions so you get a gradual change of tehsion from the max to the min and still keeping the rim wobble less than 1 mm. If the variation is + / - 20% I think you were starting off with a warped rim - I think with a reasonable rim you can expect to keep the tension even within + / - 5%

Thanks for the input so far guys...I'm leaning towards the improper tension issue more than anything else....when i first took possession of the wheel, i put about 40miles on it...luckily it was by the weekend so i rode it that saturday afternoon to my lbs to have it re-tensioned/trued...rode it back home that day(only 8miles) and it was already out of true again :eek: So i took it upon myself to true it back up (easy 5 minute job)...I would have called the lbs back at that time but they were already closed...i started checking through Sheldon Brown's wheel articles, and found out how important spoke tension was....well, the non-drive side was a bit loose all the way around so i gave each spoke 1/2 to a full turn till my the wheel started to dish, then i backed each one of the non-drivers off a slight-bit, trued it, then popped it off the bike and stress relieved it a couple times, put it back on the bike, checked for true, made a few slight adjustments(barely touched the drive-side) checked for a general uniform tension(pluck-test, and by feel)...

Hopped on the bike, took it for a quick spin (1mile) heard the usual little pings, got back to the garage, checked it, it was looking really good...I rode on this wheel for almost 2 weeks(over 270miles) and the wheel only went just slighly out of true, but nothing to be too conserned about....then, on that Saturday(weekend before last) I was on a short ride back from a friends house, and low and behold, "POP".....

...frustrating!

Try using DT Swiss Super Comps or Alpine III spokes

In a similar note: I used to frequent a bike shop that is the local Trek & Mavic distributor. Once the man behind the counter proudly told me that their master mechanic can build wheels without tension meters. I got hold of a Park tension meter & have built a few wheels that are going very well!

Neither one of those suggestions will strengthen the wheel. The first facilitates rim replacement; the second is merely cosmetic.

Your story about the wheel loosing tension over the first few rides is a very good clue that the wheel was not tensioned (or just as importantly stress relieved) high enough for a bigger rider... A lot of people can build a nice wheel that will hold up under a 160 or 180 lb rider, but they don't know that the tension has to be higher as the rider gets heavier... it really only makes sense, but it is easier for a builder to bury his head in the sand and say "the guy is too heavy! All my other wheels held up fine."

For bigger riders it is also more important to vigorously stress relieve, as stress relieving should set the shape of the spokes so that riding will not cause them to deform any more - I usually do this by grabbing opposing sets of parallel spokes and squeezing tightly with my hands.

I noticed that on the Speedgoat.com custom wheel-order webpage they ask the riders weight... I wonder if they (or some other builder wth experience) has reccomendations on spoke tension for heavier-than-average riders?

Also, I have built all my wheels just using hand-checked tension and they have held up well, but I am going to get a tension meter before I build another set... just to compare. And if anyone is wondering how much tension I use in my own wheels: "a lot." :D

I call this the "big guy" syndrome. After reading this thread, I agree with LarDasse74. I feel the replacement wheel was probably undertensioned when it came off the stand. But through this whole thread, I saw no one mention or ask about your riding style. With the big guys, that is an issue for sure. Do you punch the cranks and push tall gears? If so you would do yourself and the bike a favor if you didn't.

As a wheel builder facing a wheel build for someone over 200 pounds, I always try to find out what kind of pedal stroke or style they use. And then with the new sneaker I just built, I try to include some advice on pedal technique. Spinning circles at faster cadences will make any wheel last longer. This is especially important for the bigger riders.

Update:

As stated before i spin the pedals higher in the lower gears than mash the higher ones...occasionally, when i approach a short little hill, i'll stand up and crank it a bit just to keep my speed up and help me over it...but most of the time, i'm in the saddle spinning fast and furious in the lowest of gears (28T front, 32T rear) ...my lbs asked me the same thing, if i was getting out the saddle to pedal or not...funny, i just got back from a vacation down near Ocean City, MD...I took the old Nishiki...all the roads are uber-flat down there....I rode so fast one day that I lost my balance taking a turn, layed the bike down, and landed hard on my right arm...I'm okay, but the rear wheel was fubar....I took it into an lbs in Bethany Beach, DE....turned out i broke several spokes in an odd fashion...not clean breaks, but slivers of metal close to the heads...i payed $60 for a new wheel(Weinmann RM19 rim) they gave me a loaner till the work was done (Jamis Earth Cruiser.....fun bike!)...got the bike back, rode it 20miles, then took it back in for minor tweaks, tension, truing...its been rock solid since then(thanks, George :beer:)...meanwhile, my poor Trek has been hanging up on the wall waiting for a wheel that can handle me...no doubt that my local lbs has sold me a good wheel, and i have confidence in their expertise...but the puzzle remains: it's got to be either just a simple tension issue, or it's because my gatorskins are transferring too much shock to the wheel, or that my Trek is just flexing a little too much the wrong way under my torque, or a combination of it all...I know, i know :deadhorse2:

^^^ Okay. You are not a crank crusher. All of us have to crush them occasionally for those quick bursts, short hills, etc. It is the 2 hour crank crush day after day that does the damage. Your problem is a puzzle. The one thing I might have suggested would be to use double butted spokes. Wheel Guru's much more knowledgable than myself (Brandt, Keith Bontrager, and others) feel they are a better choice because they flex more. Less likely to break as quickly under uneven pressure by big fellows. A good 2.0/1.8 DT spoke might help.

Where are the spokes breaking? At the hub or at the nipple? A straight pull set up (read - more expensive) might just alleviate the breaks if they are occurring at the hub. Another trick I use for the big guy wheels is to use a 4 cross pattern on the build. A 36 hole rim is a perfect number to use this cross on. A 4 cross build disperses the load differently than a typical 3 cross build.

Of course this is just my opinion. Ask 10 wheel builders this question and most likely there will be 10 different answers.

Zardhex, how many spokes have you broken on your new wheel? If you've replaced more than two, you should probably get it rebuilt with new spokes. But don't have the same wheelbuilder do it, because he won't build it properly.

Where are the breaks occurring?