rubiconazoid

I have a Trek MultiTrack. I recently carried it to the LBS for new tires. Got the new tires put on - they seem just fine.
Before I carried it to the shop, I had zero issues with the bike. Now, since the new tires were installed. It seems like there is a problem in the drive train area. While pedaling, under moderate load, I get some "bumping" - feels like in the drive train somewhere. Doesn't seem to be a chain slipping but could be. Maybe from bottom bracket - not sure.

Could just taking the rear tire off cause something like this - like not putting the chain or something back exactly like it was? I have zero problems when shifting, it's just the clunk I feel when pedaling
Thanks much

CliffordK

It really depends on the bike, and the "clunk/bump".

One option is a loose wheel axle/cones. You would be able to wobble the wheel back and forth and feel a clunk side to side. This may have gotten worse at the shop, but would have been due to an underlying condition that the shop should have picked up and fixed.

The other option, and more likely, is that you're getting a slight amount of slack in the chain when coasting or backpedaling. Then when you resume pedaling, you feel a clunk upon taking up slack in the chain. This could be caused by numerous issues such as a sticky freewheel/freehub, poor derailleur adjustment, or simply cross-chaining. This is usually more annoying of an issue than an actual issue.

A skipping chain is usually noticeable when pedaling with moderate to high force, and you feel the pedals lurch forward with a crunch noise from the rear. Also caused by poor derailleur adjustment, or worn components like a rear cassette/freewheel.

As far as derailleur adjustment, replacing a tire shouldn't affect it, unless there was a washer on one side of the dropout and it got put on the wrong side. Still, it never hurts to check adjustment whenever the bike is put on the rack.

I'd start with a bit better description of what you are feeling then follow up from there.

You can ride into your shop and talk to the LBS Mechanic, he or she might have something to suggest.

cny-bikeman

Took to the shop - working OK
Back from the shop - not OK
Next step - return bike to shop

woodcraft

Tire not seated?

Andrew R Stewart 

These are good ideas and there're more possibilities. But with so little data who knows? Agree that returning to the LBS is the best way to find out more. Andy

rubiconazoid

Thank you for suggestions. If the bike shop was just down the street I would have already taken it back - it's not that close. I will recheck and give a close look today and see if I can narrow down the possibilities.

Baboo

One of the things I would check is to be sure the axles are fully sated in the drop outs and the wheel is centered. If it isn't something easily found by looking then as others have said return it to the bike shop.

Allen

rubiconazoid

After closer inspection and a couple more rides I notice that the chainring seems "wobbly." There is quite a bit of play side to side when I rock the pedals 90 degrees to the rotation. There is no play in the pedals' normal rotation. A little search indicated that inside of the bottom bracket there are 2 bearings on each side and a piece (the metal piece that runs all the way through that the cranks attach to) that can be replaced. If these are worn would it probably be the cause for this play in the chaninring and the bumping noise?

When pedaling, when I look down through the front derailleur the chainring wavers some in relation to the derailleur which is fixed. The chainring moves side to side about an 1/8" as it rotates.

Paul Barnard

If I understand you correctly, no that piece connecting the two bearings won't cause the chainring to move. You'll need to look more closely to see if it is a chainring or bottom bracket issue. Grab the chainring with two hands and push it then pull it back toward you watching the bottom bracket area for movement. That will tell you whether you have a BB or chainring issue. It may be as simple as something being loose in the BB assembly. Have you snugged up on any of the bolts?

andrewclaus

Line up a crank with the seat tube. Grab the crank with one hand and the seat tube with the other. Try pushing them together and pulling them apart. There should be no noticeable play. Squeeze hard to be sure. If there is play, your bottom bracket needs to be serviced or replaced. It may be a cartridge assembly that cannot be serviced, but they're not very expensive to replace.

It would be helpful to know if the noise is in cadence with pedaling, chain length, wheel rotation, or none of the above.

How long had it been before tire replacement that the bike was ridden?

rubiconazoid

Bike is frequently ridden (50 miles a week in the summer). Previous tires were worn past indicator on the rear.

I did what you suggested, lining up the crank with seat tube and pushing them together and pulling them apart. There is at least an 1/8" of play there, maybe a little more.

cpach

Yes, that is bad, and should get resolved. Ideally the shop could've inspected the bike during the flat change and advised you to additional needed service, but sometime's that's hard to do for on the spot service like new tires. This is almost certainly unrelated to them changing the tires. Assuming the problem is the bottom bracket the replacement parts are inexpensive and the labor relatively fast/inexpensive. I'd also recommend asking for a thorough service assessment. To be frank, many bikes of similar vintage and used as daily drivers and need a lot of work--could really use all bearings replaced with new cables and housing and often new chain, cassette, and chainrings. People get scared when the repair bills get high, but do better when you cost out how much use such bikes have gotten without maintenance and how reasonable such costs would be if distributed more evenly through the lifespan of the bike.

rubiconazoid

My initial post was truthful about there being no noise prior to going to the bike shop, but I certainly do not blame the tire swap for what's going on with the bottom bracket. I guess the two things just happened to coincide. Bike has been carefully watched since I bought it new, and this is the first mechanical issue it's had. No problem with anything else. I have someone lined up to look at it in a couple of weeks.

Thanks all for the responses.