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Big Guy/Broken Spokes(9 posts)

Big Guy/Broken Spokeswcwilson
Sep 28, 2001 8:57 PM
Hi,

I am a big guy (240 lbs) and have a bike with Mavic CXP-21 wheels (with DT spokes if that makes a difference). I am breaking a spoke on every longer ride. Besides losing weight (in which cycling should be helping) what can I do to stop breaking so many spokes? Should I have different wheels? If so, what wheels would people recommend for a man of my size?

Thanks,

--Wayne
re: Big Guy/Broken SpokesCT1 Guy
Sep 29, 2001 12:57 AM
Nothing wrong with the parts - just the way they've been put together - machine built wheels are notorious for incorrect spoke tension and breaking spokes. Unless you're running 28 spokes - should be no problem for your size & weight if the spokes have been tensioned correctly. You don't mention the hubs - poor finish around the spoke holes raises stress which causes spokes to break. Suggest you get the wheels tension-balanced by a wheelbuilder who knows what they're doing who will most probably dis-assemble the wheels and rebuilt them properly.
Disagree -- Parts ARE the problemjtolleson
Sep 30, 2001 11:39 AM
The Mavic CXP 21's have been NOTORIOUS for broken spokes, even for lighter riders. I'd consider a heavier-duty wheelset with more spokes.
9 times out of 10peloton
Sep 29, 2001 8:11 AM
When you are breaking a lot of spokes it is because the wheel is improperly tensioned. Bring the wheels to the best wheelbuilder you can find and have him or her retension the wheels for you. That should solve your problems.
DT Spokes and Pre-StessingRich Clark
Sep 29, 2001 8:31 AM
Spokes shouldn't break. When they do, it's usually the result of poor wheelbuilding or defective parts. First, look here for an interesting article about some DT spokes which may or may not apply to your wheels:

http://www.peterwhitecycles.com/DTspokes.htm

Then look at this article regarding the need for stress-relieving spokes when a wheel is built. This step is very often skipped with machine-built wheels, and can result in a spate of spoke-breaking beginning after a wheel has several hundred miles on it:

http://draco.acs.uci.edu/rbfaq/FAQ/93.html

Whoever sold you the wheels ought to rebuild them under warranty. Unfortunately, it sometimes happens that problem wheels come from shops where the niceties of proper wheelbuilding aren't fully understood, so you may need to insist.

RichC
Non-drive side spokes, right?nee Spoke Wrench
Sep 29, 2001 4:27 PM
If I'm right, this is a fairly common problem which has little to do with your weight. Here's the issue:

Modern 8 and 9 speed bikes have the rear wheel dished pretty severly to make room for the freehub. The problem is that when the right side spokes are tensioned to the greatest degree possible without rounding out the nipples, the left (non-drive) side spokes still don't have enough tension. Rims, like CXP 21's, which don't have eyelets are especially bad because friction between the spoke nipple and the soft aluminum limits how much tension can be applied. The loosely tensioned left side spokes actually go slack at the bottom of every revolution and are tensioned again at the top. The poor spoke elbow gets bent back and forth until it fatigues and fails.

Usually, when people break spokes, they take the wheel to a shop. If the shop replaces the broken spoke, trues the wheel, and returns it to the customer; all they have done is to return the wheel to it's original state. In other words, a wheel that has broken spokes in the past.

As other posters have indicated, the solution is to re-tension the wheel. The ONLY way to do this with a non-eyeletted rim, like a CXP21, is to use a spoke tensionmeter.

You need to find the right wheelbuilder and he will solve your problem.
Lemme add one thing...cory
Sep 29, 2001 5:20 PM
I quit paying attention to wheels a few years ago when I had a really good local mechanic build me some good ones, but I was about your size then (ask me how much weight i've lost this summer...), and I was breaking spokes every 100 miles or so. If you're running 28 spokes, I'd really consider going up to 32 when you get new wheels. I'm running 36s on my road bikes now, 32 on the MB, and I haven't done anything but extremely minor truing in at least two years.
Non-drive side spokes, right?wcwilson
Sep 30, 2001 9:58 AM
Actually, it has been half and half. The first time was drive side. I actually that one go for a while because I did not notice it until the wheel was really getting wobbly. I was going to take a stab at truing it myself when I saw a spoke was broken. A few others were completely loose. The last one was drive side and the two in between were non-drive side.

Thanks to you and all the other people that asnwered my question. The concensus seems to be that I need a good wheelbuilder, not new wheels. That is good to know...

--Wayne
ditch the CXP21'sCarl T
Oct 1, 2001 6:14 AM
I'm currently 195 lbs, down from 215, and had a similar problem with a set of the same rims this spring (32 spoke/ultegra hubs/15 gauge spokes). After breaking several spokes on the rear wheel, I had it rebuilt with 14 gauge DT spokes. Got a couple hundred miles and started breaking spokes again.

These were the stock wheels on my 2000 Raleigh R-700. I talked to a mechanic at the local Raleigh shop, and he advised that this was a very common problem on this bike.

My theory is that the CXP21 rim is too weak for bigger riders, and flexes a lot, causing the spokes to flex and break after a short period. I finally called Colorado Cyclist and had them build me a set new set (32 spoke, Ultegra hubs, CXP33 rims, 14 gauge spokes). 800 or so miles later they're still going strong. Best $237 I've ever spent...