mike455555

okay im fixing my bikes BB, i thought i bought the correct replacement parts

what came off the bike was a Shimano FCM151 28/38/48 X 170mm Steel / Alloy Chainset and a 68/118 BB

what iv tried to put back on the bike is a 68/118 BB and a SHIMANO Acera FC-M361 Chainsets MTB 48x38x28T 170MM Black.

now the problem is that i can not get the dallier to drop to the smallest cog on the chain set (i think its hitting the frame). dose this mean i need long spindles on the BB if so how longer would i need? or have it just fitted it wrong


thank you for any help in advance

aggiegrads

mike455555

here are some photos there is currently no cable on the FD, (i took it off to see if it would shift at the loosest setting (it dose not)

andrewclaus

This is pretty common when changing cranksets. They often have a different "dish." If so, yes, you may need a longer BB. Measure new and old cranks, from a straight edge across the small chain ring to the inside of the crank arm.

Also verify the front der is installed correctly, at the right height and parallel to the chain rings.

A fellow amateur mechanic showed me a trick, where all that was needed to get a shift was to slightly adjust the rear of the der cage to the center of the bike, just a degree or two off parallel. Not pretty, but it worked.

andrewclaus

I wrote the above while you posted photos. It appears the der cage is a little out of parallel. Try kicking it in a little.

mike455555

the FD is not installed properly yet however even when pushed right to the back wheel it still dose not shift down to the lower gear, if its a 118 BB would i need a 122 or a 127?

andrewclaus

Baby steps. You don't want to end up with the reverse problem, not able to shift into the large chain ring. If you can do it inexpensively, try a 122. Do you have access to a salvage bin at a bike co-op?

mike455555

not that im aware off? im quite out on a limb, would a 122 fix the problem?

andrewclaus

Can't guarantee it. To be more sure, make the "dish" measurement described above, assuming you still have the old crank. Add the difference to 118 to get the best length, but it may still be a guess if it falls between available sizes.

12boy

I have heard of putting a spacer between the BB and the frame on the drive side. I assume this is a cartridge BB. If it is a loose bearing BB, some spindles are asymmetrical and you may have reversed them. If it isn't a cartridge BB I would suggest taking the bike to the LBS and getting one, for which they can determine the right size.I have cartridge BBs in use for over a decade with no problems. Well worth $25.00.

nfmisso

Shimano recommends that the FC-M361 crankset be used with a 122.5mm BB. I could not find the recommendation for the FC-M151 crankset.

mike455555

i have since tried to put the old crank-set on the new BB (same problem happens) could it be my FD? i feel like if i replaced the BB with a 122.5 i would have more space to play with the the FD? it hops far off the chain set in top gear, so i would think that there would be room to play around the the FD on a 122?

i am fairly new to setting up bikes so thank you for all your guys help

Bigbus

When I first serviced my BB old style loose bearings, I noticed that the original spindle was offset and I put it in backwards the first time because I wasn't paying attention when I took it apart. I had the same problem you're having. Then when I switched it up to a sealed cartridge, I had the exact opposite problem and ended up shimming the FD out a couple of MM's so I could reach the tall sprocket. Before you go buying parts and throwing them at the problem, figure out how much distance you need to move the front sprockets out to get everything to work. Jumping from a 118 to a 122 might be too extreme and you end up shimming out the FD from the frame like I had to.
Good luck and hope you can figure it out,