Shimano UN300 Square Taper English Bottom Bracket (Silver) (BSA) (68mm) (107mm)

Read Reviews
Write a Review
In Stock Online
Usually ships in 24 hours
$4.99 flat rate shipping! Learn More
This item earns up to 16 VIP Reward Points Learn More

Shimano BB-UN300 Square Spindle 68mm Bottom Brackets


  • Fits JIS square-taper cranksets
  • Crankarm fixing bolts sold separately
  • Hollow spindle

Frame Interface: BSA/English Threaded
Spindle Interface: Square Taper JIS
Bottom Bracket Shell ID: 1.37
Shell Width: 68mm
Spindle Lengths: 107mm, 110mm, 113mm, 115mm, 117.5mm, 118mm, 122.5mm
Color: Silver
Weight: TBD

This product was added to our catalog on September 8, 2020

Verified Owner
Monday, Jun 14 2021 (about a year ago)
Shimano UN300 Square Taper English Bottom Bracket (Silver) (BSA) (68mm) (122.5mm)
My 2017 Trek FX.2 had +7000 miles on it and was time to replace most of the moving bits. Replaced the bottom bracket with a UN300. The original bracket (VP BC-73) was 68 x 121.5 for JIS square-taper cranks. The UN300 was slightly longer (122.5 vs 121.5 mm) and changed the chain-line, requiring that the front derailleur needed adjusting. All-in-all, the UN300 easily fit into the bicycle frame and appears to be better quality then the original bracket.
Thursday, Sep 15 2022 (6 months ago)
Shimano UN300 Square Taper English Bottom Bracket (Silver) (BSA) (68mm) (117.5mm)
I used this to replace a >30 year old cup/cone original BB. I measured the spindle length and ordered the cartridge BB with the same spindle length. But no- it didn't work- the chainline is now too long by about 7 mm which makes a huge difference. I searched the internet and Shimano website to find anything explaining how far to the right the spindle extends, because spindle length alone does not tell the whole story. No luck. Ordering a second BB now and hoping it works.