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Shimano BB-UN300 68mm Shell Square Taper Bottom Bracket - English Thread

Customer Reviews (12)

3.7 / 5| Write your review

£23.99

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Details

- A good quality bottom bracket for traditional chainsets
- Super-accurate bearings for smooth operation and improved durability
- Durable, hard-wearing sealed cartridge bottom bracket with square tapered spindle fitting
- Maintenance-free sealed cartridge bearing assembly keeps out dirt, mud, and water for long bearing life
- Fast and easy installation without adjustment
- Narrow body allows clearance for cable routing under the bottom bracket

Product Reviews (12)

Questions & Answers (12) Q & A

Specification

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Product Reviews (12)

Overall Product Rating 3.7 / 5

Disappointing life

By Martin

07 Oct 2024

1 / 5

Had 2 of these now, both exhibited significant play within 2000 miles. Definitely not as durable as bullet proof Shimano units of old. Very disappointing.

Limited service life

By Keef

29 Jul 2024

3 / 5

ConsLimited service life

ProsLow price

I got about 18 months and ~ 3000 miles use out of this unit which was a bit disappointing but they are quite keenly priced at the moment. I'll go for a better quality replacement (IRD) which should savetime and money with labour and postage in future and so an all round better option.

terrible

By Sylvia

02 Jun 2024

1 / 5

Consbearings disintegrated within a couple of months.

Between my husband and I we have gone through four of these within 6 month. The replacement ones we got sent by our bicycle retailer felt wobbly from the word go. I'm definitely not getting another one.

Wore out very quickly

By Michael

14 May 2024

3 / 5

ConsLess than satisfactory bearing life

ProsWell priced, easy to fit

Fitted to my Brompton in June 23. Noticed substantial play in the bearings this month (May 24).
It’s covered probably 3,000km in that time - very poor compared to the life I used to get from the older higher quality shimano BBs.
Once a year change is fine for some, but the advantage of square taper sealed BBs is usually that they’ll be around long after we’re all gone. Disappointing.

Failed after a few weeks of light use

By Phil

15 Oct 2023

1 / 5

I recommend this product

ConsPoor quality

The bearings inside must have failed as the spindle became loose and wobbly after only a very few miles of light use. Poor quality.

Great upgrade from the standard Brompton BB

By Matt Wood

07 Mar 2023

5 / 5

I recommend this product

I use my Brompton to commute on and do about 14 miles a day on it and found I was going through the standard Brompton BBs. I know they are pretty cheap but I was thinking there must be better ones out there. I contacted SJS to ask and Wayne was really helpful and recommended this BB. It is well priced compared to a lot of the other choices out there and certainly seems a lot more robust than the Brompton one.

Just the job !!

By Gary

30 Oct 2022

5 / 5

I recommend this product

ConsNone

Proshigh quality product

excellent quality product , used on a 1986 Raleigh restoration.

By Robert

30 Jul 2022

5 / 5

I recommend this product

ConsTake care to match the threads when fitting

ProsEasy fit, smooth operation and expected long life

The only way to replace bottom bracket bearings.
Easy to fit, smooth operation and long life going by a previous one I had for many miles and years.

Excellent service and product

By Martyn Wilson

05 Oct 2021

5 / 5

I recommend this product

ConsNone

ProsQuality

SJS went the extra mile in their advice. The bottom bracket is high quality and good value at the price. Recommended

Top quality

By Martin chant

25 Sep 2021

5 / 5

I recommend this product

ConsNon yet

ProsQuality and price

Recommend as an alternative for a Gates belt drive, time will tell but quality is super and price is good.
Biggest problem for BB on belt drive is the belt tension.
There is an app to get tension correct

A good replacement

By Giles Phillips

16 Jun 2021

5 / 5

I recommend this product

Consnone yet!

Proswell made and finished

Fitted this bearing set as a replacement for a BB-UN71 which had started clunking. Very nicely made and finished, and fitted in the hole with no issues. Only covered 20 odd miles so far but the clunk has stopped, so winning so far.

A good replacement

By Giles Phillips

16 Jun 2021

5 / 5

I recommend this product

Consnone yet!

Proswell made and finished

Questions & Answers (12)

What is the diameter of the shroud / tube in the middle of this BB?

By David

20 Dec 2023

I'm trying to figure out whether this BB would work with IRD conversion cups. I know Stronglight JP400 is a match, but I'd rather use Shimano BB due to a cartridge bearing seals being better.

SJS Customer Service:

The inner sleeve is 30.25mm. SK 21/12/23

Can this be fitted/removed with an old-style Shimano tool?

By Marco

24 Feb 2023

Years ago I bought a Shimano BB tool for fitting/removing older bottom brackets, such as a UN73. I still have the tool, so want to check if it will work with this newer unit.
Thanks

SJS Customer Service:

Thank you for your enquiry, yes it will be fine, these use a standard tool.

WD 24/02/23

I have a thorn Sherpa, 7 years old, is the 110mm axle length correct? Thanks

By john

19 May 2022

SJS Customer Service:

For any information or advice on any of Thorn bikes, frames and forks or parts, please contact our dedicated Thorn bikes sales team either on 01278 441505 or [email protected] and they'll be able to provide you with all of the information you need.

I have a thorn sherpa 5 years old, will the 68mm shell fit?

By john

07 Dec 2021

SJS Customer Service:

Thank you for your enquiry, yes 68mm will be fine

WD 07/12/21

Bolts required for vintage chainset

By Robert Ridley

28 May 2021

I am looking to replace the traditional cup and cone bottom bracket with a sealed unit to cut down on maintenance. the Chainset is a 1984 shimano golden arrow. Can you confirm if this BB would be a suitable replacement and recommend some options for compatible crank bolts?

Thanks,
Rob.

SJS Customer Service:

BB is very likely to suit if the cranks are JIS taper- being Shimano this will certainly be the case! Crank bolts wise- SJS part 37320 is the best bet.

JK 28.05.21

Could this replace a BB-UN71?

By Giles Phillips

10 May 2021

I'm rebuilding a '92/3 Marin and have extracted a BB-UN71 bottom bracket with 122.5mm spindle. Would this be a suitable replacement regarding fit and durability?
Thanks
Giles

SJS Customer Service:

Thank you for your enquiry, yes will be fine

WD 11/05/21

Can you tell me what's the difference?

By Greg

04 Apr 2021

between this and the the Shimano UN55 68mm?
Thanks, Greg

SJS Customer Service:

Thank you for your enquiry, Shimano have discontinued the UN26 and UN55 and they have been superseded by this part

WD 06/04/21

Is this ISO or JIS?

By Anonymous

17 Mar 2021

SJS Customer Service:

Thank you for your enquiry, it is JIS

WD 17/03/21

Thread length on this BB in reality

By Steven Wright

03 Feb 2021

Hello, are there really 13 threads on the RHS cup as per your picture please? What is the depth in mm from underside of the lip?
I have a UN300 in front of me with 9 threads/ 12mm max of threads from the lip underside.
I need just that few more threads due to a partially semi-stripped BB for peace of mind.
Thanks

SJS Customer Service:

Thank you for your enquiry, from base of lip to bottom of thread is 12mm.

WD 03/02/2021

Will this fit with FSA triple chainset.

By Richard Norman

25 Oct 2020

Hello, can you please tell me if this is the right length to mount a FSA triple chainset to an old (1980s) raleigh bike that I am rebuilding. The width is 68 mm but I'm not sure of the length.
Thank you.

SJS Customer Service:

Hello, I'm afraid without knowing the existing length we cannot assist. The BB to crank arm fitting is correct but you need to ensure the BB shell threading, width and length are known in order to purchase a 1:1 replacement unit.

Thanks,

JK 26.10.20

Plastic / Metal Ring On Axle

By Scott

24 Sep 2020

Hi guys, just wondering if you knew what the ring on the axle is for?

And if so is it removable?

SJS Customer Service:

The ring is a limiter, it is no removable.

Thanks

Bracket bolts

By Lynne

30 Jul 2020

I was wanting to purchase the Shimano BB UN55 68 - 122.5 to replace my old bottom bracket but it is not in stock so I was advised that this bottom bracket is an alternative. Do I also need now to purchase different bracket bolts to fit this different model bottom bracket when purchasing it?

SJS Customer Service:

You can reuse the original bolts.

Thanks - 04/08/20