Been riding a specialized mountain bike for about a year just for excercise. Decided I like it enough to invest in a nicer bike. Purchased a Trek 7.5 FX about two weeks ago. Really like the bike. I stay on the largest front sprocket all of the time since it is not that hilly where I ride. Use about four of the rear gears starting with the smallest. In the two lowest gears, I can hear a slight chain rub on the front guide and it gets worse if I stand up to peddle. Of course the bike store says some chain rub noise is normal. I have not taken it back in for them to look at it yet. The store is about an hour away. Some of the problem is that the front sprocket looks to not be true causing the chain to weave back and forth inside the guide. Is this normal for a bike like this or should the sprocket be perfectly straight with no chain movement?
Sprocket Question.
- Thread starter Woody0301
- Start date
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Manonabike
Über Member
No, I don't think it's normal.... you just need a little adjustment on the front derailleur. 2 minutes job for a bike mechanic I'd think.
I hope so but the chain moving back and forth going into the derailleur worries me and why does it get worse when I put more stress on it by standing up. I worry more about the sprocket not being true. I have a couple of other bikes that did not cost near as much and the sprocket does not wobble.
I plan on taking it back next week. I would'nt think about adjusting it myself at this point. I wonder what the chances are of the sprocket being the problem instead of the derailleur adjustment? Like I said, when I talked to the bike store on the phone, they were already making excuses and saying that all bikes have some noise. Could be a showdown but I hope not.
Manonabike
Über Member
The front sprocket is called a chainring and the crankset the whole thing.
Why it gets worse by standing up..... very likely that it is because all your weight goes on the pedals hence there might be some movement of the outer ring but it could also be that the crackset needs tightening up or even the bottom bracket.
Most new bikes need re-tightening after 200 miles or so.
Have you had a fall? If not then I think it's unlikely the chainring being the problem.
No falls. There's not a scratch on the bike except for the backside of the outer ring. Not sure where those came from either. Looking back though the noise did show up at about 150 miles. 200 on the bike now.
Cubist
Still wavin'
- Location
- Ovver 'thill
The rub is normal as your cables have stretched, and just need adjusting.
The wavering chainline :- I reckon the chainring may be loose or bent, or the Bottom Bracket loose.
Your description of the way you use your gears concerns me. You will be putting massive strain on the drivetrain, not to mention your knees.
The wavering chainline :- I reckon the chainring may be loose or bent, or the Bottom Bracket loose.
Your description of the way you use your gears concerns me. You will be putting massive strain on the drivetrain, not to mention your knees.
Found time to drive an hour to the bike store today. They had it fixed in about 15 minutes after the guy did a test ride. He said something was loose inside the crank allowing the drive to wobble. Rode around the parking lot and it seems to be fixed anyway. Will find out for sure tomorrow. Never been educated on gears. Always used the one I could physically stand and get the most speed. Is there something I am missing?
Manonabike
Über Member
Cubist
Still wavin'
- Location
- Ovver 'thill
Yes
Try to find a gear that you are spinning rather than mashing. If you are always up against your maximum you will grow enormous thighs, but struggle on hills. Try to "spin" at 80-90 rpm, and see how much easier life is.
No doubt, thanks to all that gave me some feedback on the problem and tried to help. I believe you were the first to respond!!! I was excited that someone replied at all. He really got it straightened out though. Rode around the block and it is as quiet as can be in all gears. Really happy with the bike. Thanks again to everyone, but i'll be back with more questions. As a matter of fact I do have one more. What are some different ways to carry a bike in a pickup without laying it down? I like DIY projects. Built a nice bike rack out of PVC I saw on you tube. Modified the dimensions somewhat but it works really well.Mmmm, well it's customary to thank the members that have tried to help
Well as a matter of fact, I have been trying to build my legs up some so I was on the right track there. I am mainly riding for fitness and to relieve stress though. Thanks for the advice.
Manonabike
Über Member
You are welcome. Can't help you with your other question though. Perhaps if you find a way to fix one of those roof rack for cycles or even a bike stand
.... I'm sure you'll find a way.
