My 2011 Felt Z85 with nearly 3,400 miles has had its original square taper bottom bracket creaking and clicking for some time now. I finally decided to take out the original BB in order to replace it. When I removed it I found it to be labeled "RPM BB-7420" with a "68" mark on it. So I know I need a square taper BB of 68mm width. But what about spindle length? The shortest Shimano UN55 I can find is a 68x107mm. But when I put my digital micrometer on the spindle it measures more like 103mm. So does that mean the UN55 won't work for me?

Shimano doesn't make every possible spindle length, only the ones that their cranks might take, the ones that are current OEM or the ones that will sell in a number that makes them happy. There are other BB makers that do provide a 103 spindle with a 68 shell width. Andy.

The 107 mm UN55 BB would move each crank arm outwards 2 mm. While it may work, it will move the chain line outward and widen the tread width. I performed a search for 68 x 103 bottom bracket and there are several available, none Shimano.

Those with more experience with your drive train than I will hopefully add their thoughts.

Brad

Is your BB symmetrical or not?
Sometimes the DS is a few mm longer and sometimes not.

Yes it is symmetrical.

The trouble I have found is finding one with decent ratings that doesn't cost a fortune. Many reports of my original FSA/RPM BB-7420 developing noises after just a few months or few hundred miles. Mine has over 3,300 miles on it but has been making noise for at least 1,000-1,500 of those miles.

I'll probably end up getting this one: Amazon.com: IRD QB-55 JIS Square Taper Road Bicycle Bottom Bracket: Sports & Outdoors

I bought this one because I wanted steel cups. The threading is very clean and it's smooth and dead silent. I have no idea how long it will last, but the first few miles have been luxurious.

It seems to be far higher quality than it's price tag.

Amazon.com: Sunlite Square - Comp Cartridge Bottom Bracket - 68mm, ENG, Square Taper, 103mm, Steel: Sports & Outdoors

People hate Bike shops where things can actually be seen .. measured and compared ..


costs more than the cheap Shimano disposable stuff, but Phil Wood BB can be pressed sideways because they use a precise fit

of the axle in the Bearing ID and that holds it in place , \but can be pulled thru the bearings with the crank arm bolt itself..

and a little ingenuity.. 2 of the installation tools and a couple flat washers worked for Me.

Personally, I'd try to figure out what's making noise. Are the bearings spinning smoothly? If so, I'll bet something else is moving around- an issue with cartridge BB's since there are so many metal-to-metal interfaces that can move around.

I would remove the BB, clean the threads, clean the inside of the cups, clean the outside of the cartridge, and then reassemble with grease on all mating surfaces. If the noise goes away, you've fixed the problem. If the noise goes away then reappears, I'll bet there's a bit too much clearance between a couple parts. I would repeat the dissassembly/reassembly process, but use a layer of plumber's teflon tape in place of grease.

I went through this a couple years ago on a bike with a cartrige BB in an aluminum frame. It took a couple repetitions with grease before I tried teflon tape. It's been tight and noise-free for a couple years.

When I hold the BB in my hand turn the spindle I can hear/feel a slight grinding in the bearings.

OK- time to replace. But your original description said "click", not "grind" or "rough". That's why I went all sideways...

IMO: you should try to find a Shimano BB-7410 103mm bottom bracket. I've had much better luck with Shimano BB's that other brands.

$50 and up for a used one, up to $200 for a NOS one. Ehh no thanks.

I said clicking at first because that's the sound it was making under load, especially when out of the saddle. But when turning the spindle by hand I can feel the grinding.

Tange $32.00:
Tange 68 x 103mm Square Taper Bottom Bracket Cartridge JIS Fits Sugino Messenger | eBay
Sugino $56.00:
Sugino CBBF 103 68 x 103mm Messenger JIS Taper Track Bottom Bracket Fixed Gear | eBay

I ordered the IRD QB-55 one from Amazon on Sunday.

Where did you see those prices?

Just Google searched it and that's what I saw.

expected delivery date Thursday 8 May DANG IT! Stupid USPS!

I was going to put my old BB back in temporarily so I could at least ride the bike until the new one came in, but I think I messed up the threads a bit on the BB cups and can't get it to thread back in easily, and I don't want to risk messing up the threads in the frame.

If it is the cups, remove them, run the point of a scratch awl around the first couple threads to see if there's an obvious flaw to remove, then reinstall them one at time to be sure they thread in smoothly. You wouldn't be the first person to cross-thread a bottom bracket cup, not by a long shot. I've done it a couple times, and it's a horrid feeling.

It helps to watch the cartridge from the other side as you're threading it in. This makes it easier to spot misalignment before the threads get damaged.

Ugh. That moment when you realize it's not a snug fit and you've gone to far....yuck.

Well the BB ended up coming in yesterday. Went to put it in last night. WON'T GO! I turned the bike upside down and had a close look, and sure enough a couple threads on the BB shell drive side are tweaked. So I'm taking the frame and the BB up to the LBS this morning to have them chase the threads. I actually took it yesterday but it was right before they closed, and the guy thought they looked pretty good. But he wasn't looking at the bike upside down either.

Sometimes, if they aren't too bad, you can rotate the BB backwards, while keeping it "centered".
You may feel it "drop" into a thread. At that point, see if it will screw in by hand, using light force.
That's my SOP since they are easy to cross thread.

IRD BB way better than Shimano.

Tried that many times, couldn't get it. Took the bike and BB to the LBS again on Saturday and they got it all fixed up for me for just $15! I think they gave me a discount since the guy said it was fine on Friday or something. I ain't complaining.

Really? I couldn't find very many reviews on them. I'm actually still hearing a single click sound at one point in the crank rotation, not nearly as bad as before, so I'm wondering if it's one of my pedals or something.

And now just 4 months later, I have definitely determined that this BB is completely shot! I started hearing clicks and pops only 2 months after installing it. I thought it might be the pedals, and the noises progressively got worse. It's REALLY bad now, when pedaling out of the saddle. I switched pedals to my wife's platform pedals, and still heard the loud popping and clicking sounds.

Really disappointed in this BB. Would I have much trouble using a Shimano UN55 107mm spindle instead of a 103mm spindle? That would push the chain rings out 2mm correct?

A derailleur equipped bicycle rarely runs it's ideal chain line, I wouldn't worry about using the 107 mm BB spindle.

Brad

Wow, I am such an idiot. I now have a new Sunlite BB, but the problem never was the BB. It was the rear skewer/axle!!

https://www.bikeforums.net/bicycle-me...l#post17134109