Help Sizing Square Taper BB Spindle Length?

[David Benson]

Originally Posted by andy.mgnr

Hey all - I'm building a 93' Ritchey Road Logic and snagged a set of these Ritchey Logic Compact cranks that I will use set up as a compact double (like in the attached example)...
I checked Sheldon Brown's BB Size database and found this crankset listed with a 110-113 spindle length, however should I go a bit slimmer since I am setting this up double and not triple? Thanks!

I have used Ritchey Sub Compact cranks on a Ritchey Breakaway and a couple of gravel bikes over the last ten years.
On my current gravel bike I am using a 98mm Phil Wood ISO bottom bracket, which results in chainline around 44-45mm and 143mm Q factor with a minimal offset to the left.
Prior to finding the 98mm Phil BB I used Phil and Campagnolo 102mm ISO bottom brackets. Either of these will be easier to find than 98mm.
With 42/29 rings, shifting to the big ring is acceptable but not excellent using either a Campagnolo 10 speed or IRD front derailler.
When I tried the same cranks with 48/32 a Campagnolo 10 speed derailler would not shift to the big ring out of the stand. Your mileage may vary with some other derailler.

[kingpin75s]

Originally Posted by David Benson

I have used Ritchey Sub Compact cranks on a Ritchey Breakaway and a couple of gravel bikes over the last ten years.
On my current gravel bike I am using a 98mm Phil Wood ISO bottom bracket, which results in chainline around 44-45mm and 143mm Q factor with a minimal offset to the left.
Prior to finding the 98mm Phil BB I used Phil and Campagnolo 102mm ISO bottom brackets. Either of these will be easier to find than 98mm.
With 42/29 rings, shifting to the big ring is acceptable but not excellent using either a Campagnolo 10 speed or IRD front derailler.
When I tried the same cranks with 48/32 a Campagnolo 10 speed derailler would not shift to the big ring out of the stand. Your mileage may vary with some other derailler.

Lol. I was going to mention that I know at least one guy on RBW/iBOB that had custom 98mm Phil BBs made. That said, they will not be found as custom only and not many made, as I understand.

I have just stuck with the Phil or other 103mm JIS, but nice to hear some ISO setups have worked as well.

Like the style guys! TA rings and Grey Logic Compacts. Perfection. My NOS set on a re-build in progress now:

[andy.mgnr]

Love to see I’m not the only one rocking them like this! Just got my 107mm BB today which I ordered before I saw all the confirmation of 103mm, I’m assuming this clearance is looking far too much?

[andy.mgnr]

Originally Posted by David Benson

I have used Ritchey Sub Compact cranks on a Ritchey Breakaway and a couple of gravel bikes over the last ten years.
On my current gravel bike I am using a 98mm Phil Wood ISO bottom bracket

Interesting I assumed it was a JIS spindle but should I be using an ISO? I didn’t believe them to be interchangeable but is there an advantage to going ISO?

[David Benson]

Originally Posted by andy.mgnr

Love to see I’m not the only one rocking them like this! Just got my 107mm BB today which I ordered before I saw all the confirmation of 103mm, I’m assuming this clearance is looking far too much?

This is what mine looks like with the 98mm Phil BB:



and another with Campagnolo 102mm:


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FWIW I usually measure chainline from the seat tube and add 14.3mm, aka 9/16"

[David Benson]

Originally Posted by andy.mgnr

Interesting I assumed it was a JIS spindle but should I be using an ISO? I didn’t believe them to be interchangeable but is there an advantage to going ISO?

I think that JIS is correct, but if the taper in your cranks is relatively unworn, you can use ISO which will move the chainline inwards.

[David Benson]

Originally Posted by andy.mgnr

Interesting I assumed it was a JIS spindle but should I be using an ISO? I didn’t believe them to be interchangeable but is there an advantage to going ISO?

I think that JIS is correct, but if the taper in your cranks is relatively unworn, you can use ISO which will move the chainline inwards.

According to Sheldon Brown "if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length."

[andy.mgnr]

Originally Posted by kingpin75s

Lol. I was going to mention that I know at least one guy on RBW/iBOB that had custom 98mm Phil BBs made. That said, they will not be found as custom only and not many made, as I understand.

I have just stuck with the Phil or other 103mm JIS, but nice to hear some ISO setups have worked as well.

Like the style guys! TA rings and Grey Logic Compacts. Perfection. My NOS set on a re-build in progress now:

Got my 102 ISO square taper and the chain line is much better! However I’m having an impossible time setting up the front derailleur, did either of you run into this?

It takes a ton of tension to get it shift up it seems and it always throws it over the outer chainring into the crank arm, if I tighten up the outer limit screw enough that it doesn’t drop it won’t quite be able to shift up into the big ring! I’m on 50-34 rings and a full Chorus 11 2015+ group.