Ashwarren

Hi All

I have a round cottered bb on an early Dawes I am restoring and I want to swap it out for a square tapered one to match some cranks etc. I have coming. Its a TDC No 9. 120mm. Can anyone tell me what to look for?

3alarmer

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...look online for a sealed unit, square taper bottom bracket unit that has the proper threading for your Dawes (I assume it's standard threading), and is the recommended spindle length for your chosen cranks. The spindle length varies from crank to crank. You'll need to pull the fixed cup as well as the adjustable one, which is not always an easy thing to do. Might be worth getting someone with the right tools to do that operation.

rhm

Whatever bb or bb spindle you use, it should match the crank. I'm sure you can find a spindle that will work with the existing cups, or you can get a whole sealed unit. A standard English thread unit should be fine, but we can't tell you what length you'll need; that will depend on the crank.

Ashwarren

Thanks. I have extracted the fixed and adjustable cups already. I will have a look online as you suggest, I just wanted to know what I was looking for. The spindle length is 120 mm, you said the length varies from crank to crank?

Ashwarren

OK, cheers for that. Sounds like just buy a complete sealed unit is best. I have these cranks on order'

Vintage - Silstar Alloy Double Chainset 52 / 42 T , Cranks 170 mm, 80's Dawes
From a 1983 Dawes
Square Taper FIt
Chainwheels are 52 and 42 teeth
Crankarms 170 mm

How do I know which spindle is compatible with these cranks?

JohnDThompson 

Probably a 115 to 118mm spindle would work. Hard to predict, as the Silstar crank pre-dates modern cartridge bearing bottom brackets by many years. Some cartridge units, e.g., Phil and Mavic, allow side-to-side adjustment to fine-tube the chainline, but they tend to be expensive. If you're having a shop do the work, you could let them figure it out. If you're doing the work yourself, ask if you can return/exchange the cartridge if it doesn't work for you.

non-fixie 

Silstar was manufactured by Sakae Ringyo. Have a look here, and see if you recognize your set. If you're lucky, you'll find the right spindle length there.

dddd

A bottom bracket from that era typically had a bit of offset toward the driveside, perhaps a couple of millimeters, versus a cartridge bottom bracket that more often will be symmetrical unless it's one of the OEM cartridge bottom brackets having the style of letter code such as "D-NL" or some such.

Note that a thin cup spacer can often be used to duplicate such an offset, but the thickness is somewhat limited when using today's Shimano UN-5X series of cartridge-style bottom brackets having a mini-flange on the left-side cup.

Note also that using a square spindle in the old cups may not only affect the offset, but also that the left-side cup may either protrude from the bb shell or may not leave enough threads showing. These issues are due to the differences in cup thickness that turn up between different brands and models. But by all means give it a go if you have a spindle at hand or can return one that you buy locally.

Ferrouscious 

I would bet on 118mm as that's what was on my Austro. The spindle also may be stamped 3P, which corresponds roughly to the same. 122mm if you go to a modern symmetrical one.

Miele Man

If there is a bicycle co-op near you it might be worth your while to take the bike and the crankset there when you get the crankset. Then you can try different spindles.

Cheers

ryansu

Your fortunate if you have standard threading the Raleigh's of the early 70's had proprietary threading which makes this swap difficult and the Peugeot's are well French and the easiest option for them is the somewhat spendy VO French threaded bb

JohnDThompson 

I only recall the 1-3/8" x 26tpi bottom brackets on the Raleigh-branded production, but it's worth checking to be sure. If the OP's frame does have the 26tpi thread, there are at least three options available:

1) retain the original 26tpi cups and find a square-taper spindle with the appropriate length and offset for the chosen crank.

2) Use a threadless cartridge bottom bracket from Velo-Orange, YST, etc.

3) Use a Phil Wood cartridge ($$$) with Phil's 1-3/8" x 26tpi mounting rings.

Random Tandem

My Dawes Realmrider (late 70's, early 80's) had a British standard threaded bottom bracket, unlike Ralieghs I have cursed.

I agree with the suggestion of sizing the spindle at a bike co-op, if that is possible for you.

-Will