OK chainrings may not be the most interesting topic but they are one of the most visible parts of a bike and determine "the look" of a classic bike. For many years the Stronglight 49D and T.A. "Cyclotouriste" (AKA Pro 5 Vis) were the most popular of alloy cotterless chainsets and to many a vintage or classic bike looks perfect with one fitted. Both of these models used the same 50.4mm Bolt Circle Diameter (BCD) to mount the outer chainring to the crank. However the inner ring BCD, where the inner ring bolted to the outer was different between the Stronglight and TA products., so you could swap the pairs of rings but not individual rings between the two manufacturers. Also the Stronglight 49D was only ever sold as a 52 teeth/42 teeth double, whereas the T.A. Cyclotouriste was available in singles doubles and triples in a huge range of sizes down to 26 teeth for the inner and as many as 60 teeth for the outer. so many cycloists fitted their Stronglight 49D cranks with TA rings.
Many of these cranksets survive and need new rings. Both TA and Stronglight are still going strong as manufacturers of rings and chainsets (in the case of Stronglight), but only TA still make the 50.4mm BCD rings and they are to special order. Velo Orange make a few sizes and SunXCD are launching their own in April 2015. There will be 48T, 46T, 44T for outer and 30T, 28T for inner chainring. Prices will be available soon. We stock a range of new TA rings which we specially order every few weeks.
Both Velo orange and SunXCD make new 50.4mm BCD cranksets. The VO ones are more like the Stronglight and the SunXCD are more akin to the T.A. Cyclotouriste. We sell both makes, although the V.O. ones were unavailable for a while and the SunXCD are more popular with our customers.
See the range here
We sell an extensive range of bottom brackets so not surprisingly we get lots of questions. It is only a little bit technical, but can be confusing. So let's try and keep it simple.
BOTTOM BRACKET TYPES
First identify your bottom bracket type:
- Standard BSA (English) threaded: 1.375" diameter 24 threads per inch. 68mm shell width (mountain bikes have a 73mm shell)
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Older Raleigh1.375" diameter 26 threads per inch. 71mm shell width.
- French: 25.4 threads per inch x 35mm. 68mm shell width Right hand thread BOTH sides. Sometime in the early 80's French manufacturers gradually changed over to English threading
- Swiss same as French but with a Left Hand Thread on the drive side. Usually found on French bikes.
- Italian. 36mm diameter 24 threads per inch, 68mm shell width Right Hand thread BOTH sides
There are other rarer types that we can't help you with anyway.
IDENTIFYING YOUR BOTTOM BRACKET
- Rule number 1 - ASSUME NOTHING! whatever the make or age of your bike.
- Measure the shell width. It should be 68mm. If it is 71mm or 76mm it is likely an older Raleigh with 26 TPI
- If it is a Raleigh and originally came with a cottered chainset it is Raleigh 26 TPI.
Raleigh 26 TPI bottom brackets usually look like this
- If the adjustable cup and lockring are on the Left Hand Side, it is English or Swiss threaded, unless someone has assembled it incorrectly in the past (very likely)
- If the adjustable cup and lockring are on Right Hand Side, it is French or Italian.
- If it has adjustable cups and lockrings both sides it is probably French threaded
- If the fixed cup has a concentric circle engraved round the axle (see photo below) it is French threaded. Not all French threaded cups have this circle. They should but they don't always.
REMOVING YOUR BOTTOM BRACKET
- Remove the adjustable cup and lock ring. It shouldn't be tight. These are always right hand threaded so undo anticlockwise.
- Remove the axle and bearings.
- Remove the fixed cup. It may be tight. If you are sure it is English or Swiss threaded then it undoes CLOCKWISE . If it is VERY tight and you have any suspicion that it might be French or Italian threaded, try turning it anti-clockwise (it is worth a try!)
CHOOSING A NEW BOTTOM BRACKET
DECIDING THE LENGTH OF YOUR NEW BOTTOM BRACKET
The length depends more on the chainset you choose, than your frame. If it is a new chainset, the manufacturer/supplier can advise. If it is an old one the there is a database here
If you are just replacing the BB then this article by Velo Orange is worth a read too.
FITTING YOUR NEW BOTTOM BRACKET
- Make sure the threads inside the bottom bracket shell are clean and free from grit, flakes of paints etc. You should be able to screw in the cups by hand.
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Fit the fixed cup side first (RHS on English & Swiss - LHS on French & Italian) but don't screw all the way in and then the adjustable cup. Then tighten both sides up firmly.
TOOLS
- Over the years many and various tools have been used for bottom brackets. You will just have to find the correct one to remove your old BB
- To fit your new one, you need a "standard" (splined) tool to fit all of the VO bottom brackets
- For the Threadless bottom brackets you will need an external bottom bracket cup tool like this one
Any questions just contact us and we will try to help.
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