50.4 BCD Chainring- I am a bit confused.

[Tom Norton]

So I have been looking at a Velo Orange Rando Crankset. It is labeled as a 50.4 BCD. So is it the same BCD for inner and outer? I was looking for potentially smaller inners but they seem a bit hard to find. Also some info labels it 50.4/80bcd.
So your assistance would be great!

[Reed Kennedy]

Only the outermost ring mounts to the crank. Then you mount the inner ring (or rings) to the outermost ring. Check out this picture from the VO site:

https://cdn.shopify.com/s/files/1/2196/9775/products/back_2.jpg?v=1521003103

The 5 bolt circle (mounting the outer ring to the crank) has a BCD of 50.4mm. 

The 6 bolt circle (mounting the inner ring to the outer ring) has a bigger BCD. In theory that can be anything. In practice the outer rings are generally drilled for an 80mm bolt circle like you mentioned.

Here's a place to order the smaller inner rings:

https://www.bikeonlineshop.net/specialites-ta/pro-5-vis-inner-middle-chainring

They go all the way down to 26 teeth! But keep in mind that if you keep the stock 46 tooth big ring and install a 26 tooth small ring it may not shift particularly well. You may also run in to issues with your front and rear derailleurs, depending on what they are.

Best,

Reed

On Sun, May 6, 2018 at 1:40 PM, Tom Norton <tnort...@gmail.com> wrote:

So I have been looking at a Velo Orange Rando Crankset. It is labeled as a 50.4 BCD. So is it the same BCD for inner and outer? I was looking for potentially smaller inners but they seem a bit hard to find. Also some info labels it 50.4/80bcd.
So your assistance would be great!

--
You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+unsubscribe@googlegroups.com.
To post to this group, send email to 65...@googlegroups.com.
Visit this group at https://groups.google.com/group/650b.
For more options, visit https://groups.google.com/d/optout.

[Tom Norton]

Thanks. This helps clear it up!!
Follow up question. The supplier for chainrings mention it is foan 8 speed. So am I not able to keep my 9 speed cassette?

[njh...@gmail.com]

On Monday, 7 May 2018 07:30:12 UTC+10, Tom Norton wrote:

Thanks. This helps clear it up!!
Follow up question. The supplier for chainrings mention it is foan 8 speed. So am I not able to keep my 9 speed cassette?

You may need to change the chainring spacing. I've used them ok with 10- and 11-speed chains/cassettes. The external width of 10- or 11-speed chains is about 2mm less than the 5/6-speed chains that these cranks/rings/spacers were originally designed for. I've used the Cyclotouriste chainrings with both 10- and 11-speed chains by replacing the standard spacers with M7 stainless steel washers stacked to provide 3mm of spacing - either three or four washers depending on whether their thickness is 1mm or 0.75mm. If you can't find metric washers then 9/32" is a very close match.

I found that if I used the standard spacers with a narrow chain, the chain would sometimes skate between the chainrings and refuse to catch when changing down to the small chainring.

Nick

[Reed Kennedy]

On Sun, May 6, 2018 at 2:30 PM, Tom Norton <tnort...@gmail.com> wrote:

Thanks. This helps clear it up!!
Follow up question. The supplier for chainrings mention it is foan 8 speed. So am I not able to keep my 9 speed cassette?

I am currently running these chainrings on 2 bikes with 10 speed chains and cassettes and 1 bike with 9 speed chain and cassette. All seem to work just fine.

I'm using the VO double bolt kit on two of them and official TA bolts on another. I prefer working with the VO bolts, but they all seem to function fine.

Best,

Reed 

[Tom Norton]

Again thank for the info. Another fellow on this site is sending me some pics of his Velo Orange crankset that I may buy and install on my Velo Orange Polyvalent.

[satanas]

I spoke with a guy at the Alex Singer stand after PBP 2015 who'd finished using a TA crankset with 11 speed Campag elsewhere, so it can be done. I didn't ask about chainwheel spacing, and he didn't mention any problems or changes, but he may well have used thinner spacers as Nick suggests.

Later,
Stephen

[Mark Bulgier]

"Nick" wrote:

> You may need to change the chainring spacing. 

TA made different spacer thicknesses BITD, every .5 mm from about 2mm to 4 mm I think.  I have most of those thicknesses in my TA stash.  Can be handy for cobbling together various non-standard builds, even though I don't use any modern narrow chains on any bike with TA cranks.  For example a same-side drive tandem, where the front and rear chains have to pass by each other, so those two chainrings need wider than normal spacing.  Or my home made TA pants-guard, sort of like a cyclocross guard except it needs to be spaced out wider to clear the front derailleur cage.  Note that took one thick and one thin spacer to get it out wide enough.

So, TA made them once, long ago, but that might be a moot point since the narrower ones were never common (in the US anyway), and they're probably near impossible to find nowadays.  V-O might be your best bet, or a stack of hardware-store washers as Nick suggests. 

-Mark

[satanas]

Those with lathe access could turn spacers up quickly too; definitely quicker than hunting online and waiting for delivery. :-)

[Ford Bailey]

I use the standard T.A. spacing (NOS parts) with Campagnolo 10 speed/ 10 speed SRAM chain. I have no problems.

[Evan Estern]

I use these cranks and they work nicely with a 9 speed chain and cassette:

https://www.ebay.com/itm/SunXCD-50-4BCD-T-A-Double-chainset-Cyclotouriste-Stronglight-49D/201916074261?hash=item2f0322c915:m:mc8Wj-9DFWkwnBBd2Hwk2UA

[Stephen Poole]

It seems the only rings they have are 26T inners...

On Thu, 18 Jul. 2019, 16:18 Evan Estern <evane...@gmail.com wrote:

I use these cranks and they work nicely with a 9 speed chain and cassette:

https://www.ebay.com/blahblahblah