Back Wheel Spokes Breaking - Move to 36 Spoke ??
 

Hello -- First Time Poster -- Having a Problem with Back Wheels breaking Spokes - Heres Some Info

Trek 7500 - 700C Wheels - 24 Speed -- ( 135mm width hub ? ) - Weight 230 Lbs - I carry a 6 Lb tool pack and water on back rack - No Curbs / Jumps etc -- I Ride 20 - 50 Miles - paved road for Exercise, 2 or more times a week - Some Hills. Occasional Small Rocks / Fir Cones / Pieces of Bark from Log Trucks etc. But no Off Road - Slow on Railroad Crossings etc.

Bought the bike used and the First Back Wheel (700C - 32) began breaking spokes at the Hub and developed cracks between the spokes. Couldnt be sure of its past.

Bought a Set of Bontrager Camino - 32 Spoke wheels with 700C - 28 - 80psi ( they are double wall construction with eyelets ) -- 500 Miles began Breaking spokes again at the Hub. I had the Wheel Fixed by a Shop -- 150 Miles later broke another. I've been Chasing Loose Spokes after every Ride now. Getting pretty good at Re-tensionsing evenly using the brake pad as a statutory point to keep the wheel in line.

Not Sure to Just Keep Repairing and tweeking ... or ... Thinking I should maybe try to move to a 36 Spoke wheel.

No problems on either set of wheels with the Front Wheels. Probably not surprising. Thinking about just replacing the back wheel only. I Cant afford top of the Line but can spend moderate to get a set up that works.

I really like to get dropped off 40 - 50 Miles out and Ride Home -- the anxiety over my wheel is really taking some of the enjoyment out of the trip.

Any input appreciated - happy to provide any details i have overlooked to give the whole story. Thanks -

Your problem is bad build quality, not the spoke count. You need to either find a shop with a more skillful wheel builder or learn the skills yourself. Jobst Brandt's _The Bicycle Wheel_ is good.

The issue here is that spokes fail due to fatigue, with the number of cycles they survive (about 750 per mile) dependent on average stress and the magnitude of the variation (a heavier person causes more variation).

Wheels which have not been stress relieved have parts of the elbows which were never taken past their elastic limit and therefore have high average stress. After enough cycles all those spokes (especially on the rear drive side) will fail about the same time.

Wheels with insufficient tension (especially in the rear non-drive side) can have the spokes going slack and bending with the high stress from bending creating premature failures. The low tension also allows nipples to rotate and loosen which exacerbates the problem and means the wheels don't stay true.

Your machine built wheels failed because they weren't stress relieved and had some spokes at low tension . They would have survived if some one fixed that before you rode the bike. Other machine built wheels are likely to have similar problems.

The fix is to replace all of the spokes on the side(s) which have been breaking (they all have the same number of fatigue cycles and about the same residual stress so the rest should be failing in short order) with DT or Wheelsmith 14/15 gauge double butted with brass nipples. Set drive side tension to an appropriate level like 110kgf. Tighten the non-drive side enough to center the wheel. Stress relieve. Correct any minor problems. Assuming you correctly compensated for spoke windup the wheel will stay true until you put a bend in it. The spokes will last pretty much indefinitely, through many rims (even if crashed).

Thanks Drew

I live in the Eugene Oregon Area and will do some asking about a who in my area is a Good Wheel Person -- Thanks for the Recommendation of the Spokes and nipples. Your advice certainly makes sense. Thanks for the detailed explanation. Really helped me to understand whats going on.
Anxious to get back out there. We are supposed to have some nice days here at the beginning of Fall and I'd really like to take advantage of them.

Did you buy your new wheels from a Trek/Bontrager dealer? Bontrager wheels come with a warranty -- might have been worth taking it up with the dealer.

You could go to the CAT/Eugene bike works .. and learn to be your own wheel person.
They have a membership/hourly DIY repair shop section there.

You are a big enough rider that you rate a better quality rear wheel... the peace of mind you will get from having wheels that you know won't fail (under normal circumstances) is worth it.

And you don't have to break the bank to get good wheels... many off the peg wheels can be great if they are properly tuned up prior to riding.

When spokes break at the hub it is usually a sign of insufficient tension, as Drew Eckhardt said, above.
A 36 spoke wheel with double butted spokes would be stronger and more durable.

Thanks all


No - Ebay - They were take offs from a Upgrade. Good thought though !

32 spokes should be enough. I'd get a nice hand built wheel. I got rid of my Trek FX years ago because I was tired of the wheels & bike shop I bought it from with promises. Since I went hand built, I have never had a problem (3years). I'm a big guy and ride generally 100miles a week.

I'd imagine you could go lighter, but I've had great success with my Mavic CXP 33's (32spoke) on 105 hubs & 23mm tire.

Any bike shop cam order the rim, spokes and hub necessary to make a strong wheel. The problem, again, is getting them built (or even just tensioned) by someone who knows what he is doing. Properly built, just about any decent quality 32 or 36 spoke wheel should be sufficient.

Check these guys out. They have a section on the web page where they will build custom wheelsets.
And they are in Oregon. www.universalcycles.com

As a matter of fact, they're about a mile from my workplace. I go visit every once in a while. (They have cats!)

As others have said: a well-built wheel won't break spokes. I'm close to your weight (220 pounds now that winter is coming) and I ride a recumbent so I can't raise off the seat to lessen the stress on the rear wheel. OTOH, I've been building wheels for 30 years- I build mine with 36 spokes, decent rims (Salsa Delgado right now) and I build them with lots of tension. I don't break spokes. Low spoke tension allows the spokes to move, and movement causes metal fatigue.

IMO, the cheapest way to go would be to have the existing wheels rebuilt by hand with quality spokes. A good wheelbuilder can take your parts and make a bombproof wheel.

Have the wheel rebuilt with new quality spokes and you should be good to go stop replacing spokes as they break.
If you have more than 2 or 3 spokes break in a short time frame its time to replace the set.

tension...tension...tension...poor tensioning will and always will make everything else nice about a wheel moot...as the others have said - get a rebuild with new spokes by someone who'll get it right.

=8-)

Also, for a rear wheel, consider an off-center rim. Velocity makes two (the aerohead o/c should be stronger than the synergy o/c, all else being equal), and they let you have more even spoke tension between drive and non-drive side spokes.

At 266 lbs. (you and the bike and load) I would reccomend 36 double butted spokes tensoned to at least 110kg on the drive side.
These have proven to be good wheels for my friends. http://harriscyclery.net/itemdetails.cfm?ID=2469
On one of them the hub needed adjustment. It was a little tight.

Thanks Everyone -- I went to town today -- armed with some new knowledge ( Thank you all ) -- talked with several Shops. Found Two that were my kinda place -- Several that were not. One had to order pieces and the other had everything in stock and I liked the Help Offered.

Went with a New Mavic Rim A 119 - DT Double Butted Spokes - Brass Nips -- Installing on my Shimano 85 Hub - using The Cog Set from the Original retired Wheel set for the Bike based on Wear and Getting a New Chain ( 2000 Miles on Old One ) - New Kevlar all weather Hardcase Bontrager 700C - 32 Tire. Built - Tensioned - Installed and Fully Warranted for a Year. Will be a Nice Piece of Mind.

Can pick up Tuesday Mid Day -- Will Test Ride -- Would Like to Do a 50 Miler to the Coast on Thursday before the Oregon Weather Turns Inclement. Forecasters have said it will be a La Nina Year -- Wetter and Colder that La Nino Years. They say this run of nice weather could be our Last Blast. The old joke -- there are only two seasons in Oregon -- Winter and Road Repair.

Thank you all for your inputs and your Explanations - really helped me to not just be overwhelmed by the choices and options offered and allowed me to make a decision I feel good about.

Will Report on Outcome.

Soon, I will be posting some photos of a 50's ( I think ) Benotto Sport Bike that I have with some really Unique Features -- Hand Brakes but no Cables -- all done with rods and Levers - Vertical Pinch wheels -- I'll be hoping someone can help identify some info about its year etc. Will post in the appropriate Forum for ID Help etc.

Best to All