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Early 70s TA Cranks...Can I mod to Mid Compact?

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Early 70s TA Cranks...Can I mod to Mid Compact?

Old 06-18-19, 09:32 AM
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chainwhip
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Early 70s TA Cranks...Can I mod to Mid Compact?

Recently bought this:
1973 Raleigh Competition
_________________________________________
Exploring if I could fit a 36T 110bcd x 5b inner ring to convert this from a 52-42 to a 52-36? :




Original TA 52-42 Crankset

_________________________________________
Thanks for input.
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Old 06-18-19, 10:48 AM
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No, you can't -- this crank has three holes and a 116mm bcd, so it's not compatible with the chainring you mentioned. You'll need to try a different crank, unfortunately. Cool bike, by the way...

Last edited by noobinsf; 06-18-19 at 10:52 AM.
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Old 06-18-19, 11:01 AM
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A 116BCD will accept a 36t ring, maybe even a 35t - IF YOU COULD FIND ONE.

(You won't)
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Old 06-18-19, 11:06 AM
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Well, there's this:

116 bcd rings

If you can get the price down to say $50 by ordering a batch of 35T rings, you might make a few new friends here.
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Old 06-18-19, 11:10 AM
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Beautiful TA Crank. Sell it and buy one more suitable to your needs.
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Old 06-18-19, 12:10 PM
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Scarce as hen's teeth




About 10 years ago, I changed the TA "Pro 3 Attaches" chainrings on my late 60's Bertin C37 from 52-42 to 50-37.



36T was the smallest chainring TA made for these cranks and after months of searching I finally came up with a 37T.



You can probably find a 36T 116mm 3 bolt chainring but it needs to be arced to fit closely on the crank web plus the holes counter bored in the rear. These cranks take special chainring bolts with a large diameter head and a smaller diameter than standard chainring bolts. They tend to be brittle.

They break EASILY if overtightened and replacements are hard to find (been there - done that). I wouldn't trust those bolts just to hold a non fitted (non arched) chainring onto the back side of the large ring.

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Old 06-18-19, 12:14 PM
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116bcd

Originally Posted by noobinsf View Post
No, you can't -- this crank has three holes and a 116mm bcd, so it's not compatible with the chainring you mentioned. You'll need to try a different crank, unfortunately. Cool bike, by the way...
Thanks.
Didn't feel I was getting an accurate bcd measurement, but it looked larger.
Completely missed my 3 vs. 5 oversight
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Old 06-18-19, 12:25 PM
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Originally Posted by verktyg View Post
About 10 years ago, I changed the TA "Pro 3 Attaches" chainrings on my late 60's Bertin C37 from 52-42 to 50-37.



36T was the smallest chainring TA made for these cranks and after months of searching I finally came up with a 37T.

You can probably find a 36T 116mm 3 bolt chainring but it needs to be arced to fit closely on the crank web plus the holes counter bored in the rear. These cranks take special chainring bolts with a large diameter head and a smaller diameter than standard chainring bolts. They tend to be brittle.

They break EASILY if overtightened and replacements are hard to find (been there - done that). I wouldn't trust those bolts just to hold a non fitted (non arched) chainring onto the back side of the large ring.

verktyg
Sounds like I'd be wise to learn from your pain.
Beautiful bike!
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Old 06-18-19, 01:49 PM
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Originally Posted by non-fixie View Post
Well, there's this:

116 bcd rings

If you can get the price down to say $50 by ordering a batch of 35T rings, you might make a few new friends here.
Couldn't hurt to ask! 35T and of aluminum instead of titanium, and the price may be reasonable.
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Old 06-18-19, 01:53 PM
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If you wanted to keep it French, you could go with a Stronglight 99. 86BCD will go down to 32T, I think. Might go to 30T. There is a 99 sitting on the Bay currently as well as some cheap rings including a 36T. Sakae/SR also made a 86BCD crank as well. Some of those might be available as well.

Last edited by seypat; 06-18-19 at 02:01 PM.
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Old 06-18-19, 02:18 PM
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Search on eBay for Stronglight Touring Sport chainrings. This was another 3 arm 116bcd crank of the era and I find that smaller chainrings for this are more common. They'll fit the TA Pro cranks you have but you will have to drill the chainring holes larger to accept the TA chainring bolts. This is what I'm currently running on my Sports Tourer.
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Old 06-18-19, 02:19 PM
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As mentioned above, 36t is the smallest to fit but a challenge finding TA branded ring. Though chances are better finding another brand 3 bolt and modify to attach. I like the minimalist style and would certainly attempt a modified ring before changing the crank.

There are adapters 3 hole to 5 (possibly 6 as well) hole but unfortunately defeats your purpose. Those adapters are for 45 tooth.

This leads why the TA Cyclotourist cranks were and still desired today.

Also consider the Stronglight 49D and others with the 50.4 BCD, plus there's adapters for other large BCD rings.. Great options and flexibility.

Last edited by crank_addict; 06-18-19 at 02:24 PM.
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Old 06-18-19, 02:59 PM
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Originally Posted by crank_addict View Post
As mentioned above, 36t is the smallest to fit but a challenge finding TA branded ring. Though chances are better finding another brand 3 bolt and modify to attach. I like the minimalist style and would certainly attempt a modified ring before changing the crank.

There are adapters 3 hole to 5 (possibly 6 as well) hole but unfortunately defeats your purpose. Those adapters are for 45 tooth.

This leads why the TA Cyclotourist cranks were and still desired today.

Also consider the Stronglight 49D and others with the 50.4 BCD, plus there's adapters for other large BCD rings.. Great options and flexibility.
Just for the record: Miche makes 35T rings with a 116mm BCD. I just bought a couple. €15 a piece. Five holes, so no use to the OP, but if you're going to have them made for lower gearing, one might as well go for the smaller tooth count.
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Old 06-18-19, 03:26 PM
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Five possibilities in the real world: Velo Classique in Falls Church, VA, Peter White Cycles in New Hampshire, American Cyclery in San Francisco, Bicycle Specialties in Toronto, St. Johns Street Cycles in the UK. St. Johns has a good website, others are all reachable by phone. The smallest ring you can use with that crank is 36 t. I ran one as a 36/46 for awhile. Good cranks!
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Old 06-18-19, 05:17 PM
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I have two of the supposed elusive 116bcd 3 pin 36T rings. Took very little to find them. It's collecting. Work at it.

Stronglight had rings that fit. There are also steel rings to same pattern. 38T to pattern is far more plentiful if that will work.
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Old 06-18-19, 05:20 PM
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Originally Posted by seypat View Post
If you wanted to keep it French, you could go with a Stronglight 99. 86BCD will go down to 32T, I think. Might go to 30T. There is a 99 sitting on the Bay currently as well as some cheap rings including a 36T. Sakae/SR also made a 86BCD crank as well. Some of those might be available as well.

-----

The Stronglight model 99 & 99bis chainset goes down to 28T, both early and late type.





---

Anecdote -

Years ago I would run into Howard Sutherland trundling about the streets of Berkeley on his dark blue Jack Bobson. I once inquired of him as to the T.A. Trots Attachees chainset it wore. He replied that he liked it very much. High praise coming as it did from "The Mechanic's Mechanic."

---



-----
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Old 06-18-19, 06:05 PM
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The solution to your problem is not a scarce chainring or another crankset but another bike!

Here’s my 1973 that is almost finished (thanks Roger! &#128521
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Old 06-18-19, 06:17 PM
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OP if you get a cyclo touriste you can pretty much do any ring combination you want.
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Old 06-18-19, 06:34 PM
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Part of the reason these cranks are so loved is the Q factor is very low. The arms are almost parallel to the bike frame.
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Old 06-18-19, 06:50 PM
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Thanks for all the input so far...

I appreciate all of your leads and comments.
A lot to chew on.
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Old 06-18-19, 06:56 PM
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Originally Posted by Slowride79 View Post

The solution to your problem is not a scarce chainring or another crankset but another bike!

Here’s my 1973 that is almost finished (thanks Roger! &#128521
Nice Jubilee RD.
Black cloth bar tape?
22.5" frame?
Very well kept specimen.
Garage queen? j/k

I'm really enjoying the ride quality of this model Raleigh.
Just driven to tinker, I suppose.
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Old 06-18-19, 08:02 PM
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Originally Posted by chainwhip View Post
Nice Jubilee RD.
Black cloth bar tape?
22.5" frame?
Very well kept specimen.
Garage queen? j/k

I'm really enjoying the ride quality of this model Raleigh.
Just driven to tinker, I suppose.
I was just joking that it’s an excuse to buy another bike
i think a TA cyclo tourist would look great on your bike. Your choice but I would save the original crank in case you or next owner want to change back again.
yes mine is 22.5” , yes black Tressostar cloth tape. Found it in pretty rough shape but thanks to good people in better shape now. https://thecabe.com/forum/threads/‘7...tition.148754/
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Old 06-18-19, 08:14 PM
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Tale of three cranks. I bought this Peugeot PR10 back in August with a Stronglight TS with a wonky pedal thread and some kind of acid etching damage on the ring (@ about 1 o'clock in below picture). I had a Sugino compact 52/34 laying around, so on it went a as an experiment. I liked the way it rode, but had several inside chain drops, even after repeatedly adjusting FD. It may have been a chain too long problem. I came across a great deal on a Stronglight 99, 52/40, which restored its Frenchness, and rides pretty well with the same 28t freewheel. I know smaller rings are available for the Stronglight 99, so I may be on the lookout for that. Lots of options, good luck with yours.

As bought, Stronglight TS (50/40 ?), broken (missing) Simplex FD, 24t freewheel.

Sugino GT compact 52/34, added Shimano Exage FD, 28t freewheel. I like the look of the Sugino crank.

Current set up, Stronglight 99, 52/40, IMO, best looking of all 3 cranks.

Last edited by Slightspeed; 06-19-19 at 09:33 AM.
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Old 06-19-19, 06:16 AM
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Originally Posted by Moe Zhoost View Post
Beautiful TA Crank. Sell it and buy one more suitable to your needs.
Agreed, it's a lovely design. I had always thought that perhaps, having only three arms, it would be more prone to lateral flex. My wife had a set but her bike was stolen. Any chance you can live with a somewhat taller gear?
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Old 06-19-19, 08:19 AM
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Originally Posted by verktyg View Post
You can probably find a 36T 116mm 3 bolt chainring but it needs to be arced to fit closely on the crank web plus the holes counter bored in the rear. These cranks take special chainring bolts with a large diameter head and a smaller diameter than standard chainring bolts. They tend to be brittle.

They break EASILY if overtightened and replacements are hard to find (been there - done that). I wouldn't trust those bolts just to hold a non fitted (non arched) chainring onto the back side of the large ring.
I always loved these cranks to look at. The fact that they spec'd smaller diameter bolts on a 3 arm crank though -- that is just so very French....

I wonder if the same people making titanium chainrings for these are also making replacement bolts? It would make sense. A good machinist should be able to make them, but the cost would be pretty high.

BTW it's very cool that someone loves these enough to make Ti chainrings just for these now rare oddball cranks.
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