Bicycle Mechanics - My spokes are grinding grooves into the plastic cog guard

I was having problems with my weight and the stock wheels that came on my Trek 7100. Being low on funds and having an LBS with a bunch of nice guys they hooked me up with a new wheel for free, a double walled Bontrager Select wheel. Today was my second cummute on the thing and once I got to work I noticed a strange noise coming from the rear wheel. Upon investigation I noticed that the spokes were griding grooves into the plastic wheel that protects the cogs (at least that is what I think the plastic does). It's not spinning, it seems as though the spokes are flexing and putting stress on the plastic part causing it to rub grooves into it and making a hell of an aweful noise. Is this something I should worry about? I have yet to call the guys up over this because I'd hate to alarm them over something that could potentially be "normal".
Has anyone ever had this happen?

wait so your spokes on the drive side are bulging outwards, to the point where they hit the plastic disc? More tension, much more spoke tension

yup, that's exactly what is going on, and it just started happening on my ride this morning, my ride on Friday I never had this problem.
Could it be happening because this is a new wheel? I know my weight (300lbs) has something to do with it but the guys at the shop were fairly certain that this wheel should hold up alright.
I'm kinda scared about making the 15 miles trip home on it this afternoon.

Depends on the design of the wheel. Sometimes the spokes are really close to the plastic guard anyway so any flex at all will provoke that behaviour. Just cut the thing off and have done with it. They do nothing anyway except make noise and attract dirt in my experience. I don't have them on my bikes.

Matt

But wouldn't the fact that they are grinding in the first place be an indicative that there is a problem? I'd hate to be half way home and my wheel and spokes tear asunder. I guess I'm looking for someone to say to me "yeah that happened to me once, it was just a spoke tension issue and all is well now".

wait so your spokes on the drive side are bulging outwards, to the point where they hit the plastic disc? More tension, much more spoke tension

Last time I checked, the plastic disc was attached to the spokes :/ Is it rubbing the cassette?

well i dont remember how close the plastic guard is to the spokes. I always took them off. If its really close clearance it MIGHT be acceptable but still. If they are really flexing your going to have spoke breakage issues. Those spokes will bend and stretch, bend and stretch again, and again until it breaks. What guage are these spokes? If they are lighter spokes even at ideal tension they will flex.

Last time I checked, the plastic disc was attached to the spokes :/ Is it rubbing the cassette?
the plastic thing is attached? Dear me, no wonder i took them off

Spokes will always bend to a certain degree. What you don't want is for them to bend so much as to break. Thus proper tension is important. If the spoke protector is attached to the spokes then the differences in bending about the wheel as it's loaded will of course cause a dissimilar contact on the spoke protector and cause a sawing motion to occur. Eventually the spoke protector will simply break off and become litter. At worse, pieces of that protector will break off in mid-motion and lodge itself in your drivetrain or your chain/seatstays and cause damage to your bike. Do yourself and the environment a favour and remove the spoke protector.

and if they are flexing a lot, tension the spokes so I dont find broken ones on the side of the road ;)

The guard is attached to the hub of the wheel, not the spokes themselves as I've seen on other wheels, and "sawing" is the perfect term to describe what is happening. If I puch the bike I do not hear the noise, but once I mount it the noise starts happening.

The guard is attached to the hub of the wheel, not the spokes themselves as I've seen on other wheels, and "sawing" is the perfect term to describe what is happening. If I puch the bike I do not hear the noise, but once I mount it the noise starts happening.

If the protector is mounted to the hub then it's less likely to break apart... unless of course it's getting sawed by the spokes like in your case. :D In order to remove it, you'll have to remove the cassette. It sounds to me like your spokes are overly flexing. What spoke-count are you running back there and how are they crossed? I know you won't like it but you might need to investigate a stronger wheel with higher spoke count.

What spoke-count are you running back there and how are they crossed? I know you won't like it but you might need to investigate a stronger wheel with higher spoke count.

This is the rear wheel I am on:
http://www.bontrager.com/Road/Wheelworks/Wheels/5754.php

I've invested so much money is this thing that, to be honest, I'd rather give up than put any more into it. I see people as big as me riding Wal-Mart bikes around town all the time and here I am with almost a grand invested in my commuting bike and I can't seem to make it to work and back 2 days without something going wrong with it. If not for my LBS "giving" me this wheel, my bike would already be stored in the shed for the summer. Oh well....

This is the rear wheel I am on:
http://www.bontrager.com/Road/Wheelworks/Wheels/5754.php

I hate to say it but I really think that wheel is inappropriate for your weight. Ask any of the bigger riders in these forums and they'll recommend at least a non-paired 32H (more likely 36H) with 3-cross rear wheel combined with a stronger touring-type rim. I'd be worried about the front too. You could perhaps sell your old wheels to finance some new ones.

Yikes! My first thought is that is one heck of a bad choice for someone your weight. What you SHOULD be on is like a 32+ spoke Mavic Open Pro, not a spindly paired spoke raceday wheel. If you want the ultimate, go for a 40 spoke tandem setup. You're commuting, not racing :-) so avoid anything ultra light, low spoke count.

Thinking more about it, I honestly, I would question the competency of the LBS in giving someone like yourself that wheel. I hesitated to put my 200lbs friend on Shimano R550's on a bike he rides maybe once a week. I wouldn't recommend that Bontrager wheel to a commuter, period, and certainly not someone of your stature. If you have any specific questions about beefing a bike up for someone your size, feel free to PM me. I've built several custom bikes for larger riders (one was over 400lbs).

They let me have that wheel for free because I totally scrwewd my other one and am unable to afford anything else at this point. By the way, nice to see someone else on here from Michigan. They told me that it might do the trick but weren't sure, guess I know now. Now I have to get someone at work to drive me and my bike home, where no doubt it will be sitting for a while as I have no way of coming up with enough cash to get a new wheel.

holy crap!! Your using that?! No wonder. I built wheels from PWDbyTRD and hes over 400.
He was using 26" wheels but they also do make them in 700c, the rims.

DT Champion 14g spokes 244mm
Shimano XT m7656 hub 36H
Velocity Deep V rims.

Those things were so stiff, when i was pre stressing them the rim hardly had any deflection. It was unlike anything i have ever seen, especially compared to what i ride with (sub 1500 gram wheels :D ).
As far as I know he has not had any problems, i think the cost for everything was a little above 200

They let me have that wheel for free because I totally scrwewd my other one and am unable to afford anything else at this point. By the way, nice to see someone else on here from Michigan. They told me that it might do the trick but weren't sure, guess I know now. Now I have to get someone at work to drive me and my bike home, where no doubt it will be sitting for a while as I have no way of coming up with enough cash to get a new wheel.
sell the thing on ebay

Okay, if I could come up with some extra money, would this wheel probably do the trick? I called a few places about getting tandem wheels and they are wanting $200.00 for them, there is no way in hell I'll be able to pay that much for a single wheel.
http://www.nashbar.com/profile.cfm?category=&subcategory=&brand=2122&sku=6238&storetype=&estoreid=&pagename=

that might do. They have the Deep V road wheelset out there. Called spartacus i think. I would really try to get something with a high cross section

Yeah the guys are giving great advice here. I wouldn't even use those wheels and I weigh 13st (is that around 180lb?) so they shouldn't have given you that as a replacement wheel.

The only low spoke count wheel I would ever use (on a race bike only too, not on a commuter) are the ones I use now, Ksyrium Elites. The bontragers are nowhere near as sturdy because of the way the spokes are spaced. Get a set of 32s or 36s and have done with this problem. You should be able to enjoy cycling at 400lb let alone 300.

Let us know how you get on.

Matt