Looking at getting a set of Middleburn RS7 cranks for my Orange 5.

I’ve only ever used external BB cranks. Are ISIS still pooh? I can only find Shimano UN54 Square Taper BB’s.

I know i need 73mm x 118mm (i think!) but real experiences with either would be great.

You need a 73-113mm bb…

Had middleburn square taper cranks for a long time now, always used the UN54 BB and it’s never been a problem, they have usually lasted about a year and would still be running, just start to grind when they go…

There are a few square taper still out there, i’d say stick with the UN54 though or splash out for a Royce Titanium Bottom brakcet.

SKF or superstar ISIS BBs are good.
i use sq taper though. UN54s are really reliable. you might be able to get a UN72 from parker international (but don’t get the last one 😈 )

that BB length sounds about right. think thats what i run wity my uno…

lovely cranks BTW…

I had to go for a 118mm axle, as 113mm was too short on my 73mm BB. The inside of the lockring was less than 1mm from the face of the BB with a 113mm axle – which isn’t enough clearance. That is with square taper.

The inside of the lockring was less than 1mm from the face of the BB with a 113mm axle – which isn’t enough clearance.

Why not? What do you need clearance for there?

Go with the taper ones , both mine 10 years old and still going strong , one with a royce bb and the other on a phil wood one , both of which are as old as the cranks

Here is how mine looked with the 113mm axle:

You can just about see the black line by the drive side of the BB, that is the clearance. I thought it ‘might’ be ok so took it for a ride anyway. Within 5 miles or so a few bits of sand had jammed into the gap and made the BB start to slowly unscrew – this caused the non-drive side crank to jam against the BB, and caused a rather slow journey home.

Looks like it’ll be Square Taper then.

Can’t afford a Royce one just yet though. If a Shimano UN54 lasts a year then that’ll be better than the BB on my current Hone crankset. First one lasted 6 months, second one has needed the non-driveside bearing re-packing with grease after 3 months!!!!!

Heavy and sh1t is my opinion of Hone cranks. I want to continue the British theme of Orange, Hope etc.

I’m not convinced 113mm will be long enough. My 36 tooth middle ring(bash/36/24) was catching the swingarm pivot cap before i spaced it out so i’m thinking 118mm should be okay.

Thanks for the help

Jason, what BB have you got? 113mm is fine for the RS7’s I have, theres a bigger gap than that, i’m on a shimano UN54 bb. I tried a 118mm and the chainline was really bad.

SKF Isis BB all the way; distributed by Middleburn now as well!

Another square taper user here.

Axle width will vary: to get chainring clearance on my Inbred I had to use a 118mm axle. This was also what was advised to get a 50mm chainline. Chainsuck damage was a bit of an issue on my Inbred so I did try a 122mm axle 😯

I have a RaceFace ISIS Signature BB on my hardtail. This is the second frame it’s been fitted to. The bearings were replaced after eighteen months, which cost me eight quid. The BB is now six years old, fitted originally to my Hummer in January 03, now to my Inbred 567. It’s worked faultlessly, and looks like it will carry on for years. Can’t see a problem with ISIS, personally.

Stupid question i’m sure….How would i measure my existing chainline?

Nevermind, found out how to on Middleburns website.

Square taper Middleburns on my Superlight as well. I originally had them set up as a Duo, but my aging knees have resulted in the need for a granny ring so now they’re a triple.

I’ve just changed the UN72 BB which has lasted for just over 2 years with no problems. This has been replaced with the UN54, lets hope that it lasts aslong as its predecessor !!

Definately Square taper instead of ISIS. Oh, and my BB is a 68 x 115mm

fingerbike, it is a UN54 73 x 113mm with RS8 cranks & Uno ring. With a 73 x 118mm BB I get about 3mm clearance each side, which seems about right.