42T to 39T chainring swap
#1
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42T to 39T chainring swap
Hello everyone!
I took my 1980/82? Bianchi “Claire” out on her maiden voyage, and had a great ride. 😀
the steepest hill I did was a real challenge for me with my 28 on back and 42T chainring.
1) Would a 39 on front be noticeably better?
2) is there a cheaper freewheel I could buy to get me 30 in rear? Can I use a 7 or 8 speed instead of my 13-28?
3) is it worth going to SiS shifters and derailleur? does the derailleur really need changing
thanks for the info and to the detailed post to me yesterday, I hit my message quota ans couldn’t reply to say thanks!
PS when I got her back home to do some tweaks the front tire blew out read on the tire stand! That was some luck, it could have been at 35+ kilometres per hour!
*any tricks to the photo uploader? I’m trying to add in a picture of my chainrings and it just sits there with the upload button grayed out*
I took my 1980/82? Bianchi “Claire” out on her maiden voyage, and had a great ride. 😀
the steepest hill I did was a real challenge for me with my 28 on back and 42T chainring.
1) Would a 39 on front be noticeably better?
2) is there a cheaper freewheel I could buy to get me 30 in rear? Can I use a 7 or 8 speed instead of my 13-28?
3) is it worth going to SiS shifters and derailleur? does the derailleur really need changing
thanks for the info and to the detailed post to me yesterday, I hit my message quota ans couldn’t reply to say thanks!
PS when I got her back home to do some tweaks the front tire blew out read on the tire stand! That was some luck, it could have been at 35+ kilometres per hour!
*any tricks to the photo uploader? I’m trying to add in a picture of my chainrings and it just sits there with the upload button grayed out*
Last edited by Amelio; 09-06-21 at 12:30 PM. Reason: Adding pic
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39 will help a little. Shimano makes a megarange in 6 speed but your rear derailleur might not handle it. Also if your bolt circle diameter is 130 you could go to 38 on front. If it's campy it will be 135 and 39 is your minimum.
Nice bike!
Nice bike!
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+1. If you're going to buy a new inner ring, might as well go with a 38T.
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You are faced with the problem many of us older folks have when wanting to continue use of a bike boom bike set up with a racing crankset and short cage rear derailleur.
As to your original question, a 39T would reduce your effort be (42-39)/42 = 7%. (i.e. about half the difference you get from shifting from your 24 to 28 cog; aka not much). /However, from squinting at the fuzzy photo of your bike I'd guess that the crankset is 144 bcd so you are likely stuck with the 42.
There are three possible routes to take to get lower gearing:
1. Get a long cage rear derailleur and longer chain and search for a 13-32 (or 34) 6- or 7-speed freewheel (8-speed won't work without a whole lot of hassle and $).. This is probably the cheapest and easiest route.
2. Change your crankset for a compact crank (50 (or 48)-34)
3. Go whole hog and do (1) and all trade the crankset and BB for a triple. This is a major operation and $$.
Forget about index shifting.
Also, your tube blew either because its ancient or you exceeded max inflation pressure. If you're running ancient tires then you should replace them before a serious blowout.
As to your original question, a 39T would reduce your effort be (42-39)/42 = 7%. (i.e. about half the difference you get from shifting from your 24 to 28 cog; aka not much). /However, from squinting at the fuzzy photo of your bike I'd guess that the crankset is 144 bcd so you are likely stuck with the 42.
There are three possible routes to take to get lower gearing:
1. Get a long cage rear derailleur and longer chain and search for a 13-32 (or 34) 6- or 7-speed freewheel (8-speed won't work without a whole lot of hassle and $).. This is probably the cheapest and easiest route.
2. Change your crankset for a compact crank (50 (or 48)-34)
3. Go whole hog and do (1) and all trade the crankset and BB for a triple. This is a major operation and $$.
Forget about index shifting.
Also, your tube blew either because its ancient or you exceeded max inflation pressure. If you're running ancient tires then you should replace them before a serious blowout.
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That first picture from a completely different bike threw me off, but I believe this is the OP's crank: https://velobase.com/ViewComponent.a...115&AbsPos=347
Since the blown tube has been mentioned in a couple of the OP's threads, I'd suggest it got pinched between the tire and rim on installation. A good practice is to put a little bit of air into the tube before installing it. Not much, just enough to give it some shape. That helps it to push away from the rim and into the tire once you've installed the second bead.
Since the blown tube has been mentioned in a couple of the OP's threads, I'd suggest it got pinched between the tire and rim on installation. A good practice is to put a little bit of air into the tube before installing it. Not much, just enough to give it some shape. That helps it to push away from the rim and into the tire once you've installed the second bead.
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That first picture from a completely different bike threw me off, but I believe this is the OP's crank: https://velobase.com/ViewComponent.a...115&AbsPos=347
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#9
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sorry about that the picture uploader was giving me a hard time and I accidentally chose that from my other vintage bike, an Apollo 😊
yeah those were the original tires I believe and I’m glad nothing serious happened. Also happy I didn’t sell some of my spare tubes n tires that I had kicking around. 😊
thanks very much for your input I really appreciate it.
QUOTE=ThermionicScott;22217586]That first picture from a completely different bike threw me off, but I believe this is the OP's crank: https://velobase.com/ViewComponent.a...115&AbsPos=347
Since the blown tube has been mentioned in a couple of the OP's threads, I'd suggest it got pinched between the tire and rim on installation. A good practice is to put a little bit of air into the tube before installing it. Not much, just enough to give it some shape. That helps it to push away from the rim and into the tire once you've installed the second bead. [/QUOTE]
yeah those were the original tires I believe and I’m glad nothing serious happened. Also happy I didn’t sell some of my spare tubes n tires that I had kicking around. 😊
thanks very much for your input I really appreciate it.
QUOTE=ThermionicScott;22217586]That first picture from a completely different bike threw me off, but I believe this is the OP's crank: https://velobase.com/ViewComponent.a...115&AbsPos=347
Since the blown tube has been mentioned in a couple of the OP's threads, I'd suggest it got pinched between the tire and rim on installation. A good practice is to put a little bit of air into the tube before installing it. Not much, just enough to give it some shape. That helps it to push away from the rim and into the tire once you've installed the second bead. [/QUOTE]
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Random thoughts. Your dropout spacing is 126, the norm for the old 6-speeds. A new 7-speed FW will be a simple switch. (It looks like you have plenty of room between the chain now and the chainstay. 7-speed FWs can be a touch wider than the old 6 but there are things you can do if there is contact. Try it and come back here if so.
I'm a huge fan of triples and not-so-wide FWs. I have put many on bikes of your era. I always seek out 110 BCD triples because the chainring choices are so good. (I conceived the Peter Mooney of my username around a TA 52-42-28 triple. Re-geared it in 1995 with a 110 BCD triple. It's been 110 ever since, even now as a fix gear.)
If you can shift the current shifters comfortably - DON'T CHANGE! That allows endless playing with drivetrains with none of the hassle of getting shifters and derailleurs to work together.
The blowout - new folding tires on those rims? Do those rims have the bead hooks? (That old - probably not. The makers of folding tires assume that hook is there. With the old wire beaded tires, it was not needed.
And, as others have said - nice bike!
I'm a huge fan of triples and not-so-wide FWs. I have put many on bikes of your era. I always seek out 110 BCD triples because the chainring choices are so good. (I conceived the Peter Mooney of my username around a TA 52-42-28 triple. Re-geared it in 1995 with a 110 BCD triple. It's been 110 ever since, even now as a fix gear.)
If you can shift the current shifters comfortably - DON'T CHANGE! That allows endless playing with drivetrains with none of the hassle of getting shifters and derailleurs to work together.
The blowout - new folding tires on those rims? Do those rims have the bead hooks? (That old - probably not. The makers of folding tires assume that hook is there. With the old wire beaded tires, it was not needed.
And, as others have said - nice bike!
Last edited by 79pmooney; 09-06-21 at 12:43 PM. Reason: typo
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I also think the 39 ring on the front is a good idea. If you can find a freewheel 30 or 32 on the inside, I would do both, your knees will thank you.
2nd what 79pmooney said about your tires. If your rims don't have hooks, get some wire bead tires.
2nd what 79pmooney said about your tires. If your rims don't have hooks, get some wire bead tires.
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#13
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thanks 66, i’ve ordered the 39 tooth original ring for the front. Any idea where I could get a decent deal on the freewheel? The ones I’m finding are C$250.
#14
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you’re right I could’ve done a 38 but wanted to keep it as original as possible so I ordered a 39T. I couldn’t seem to find a 38 in silver that looked original. Thanks for pointing this out it’s appreciated!
#15
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i’m really not sure about the hooks I’m going to try and include a couple pictures here could you guys pls tell me if there are hooks or not? Thanks for the help, such a friendly group of people here so glad I found you!
I also think the 39 ring on the front is a good idea. If you can find a freewheel 30 or 32 on the inside, I would do both, your knees will thank you.
2nd what 79pmooney said about your tires. If your rims don't have hooks, get some wire bead tires.
2nd what 79pmooney said about your tires. If your rims don't have hooks, get some wire bead tires.
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I put a 39T inner on an early 42/52 DuraAce crank. It helped but wasn't a massive improvement. You might be able to find a Triplizer ring to convert your bike to a triple front. Have fun with the project.
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Amelio I'm not seeing clearly the rim profile in your pics. That said, I think those are hooked rims.
Here's a link to a site with a pretty clear explanation of the difference,
Hooked and Hookless
Here's a link to a site with a pretty clear explanation of the difference,
Hooked and Hookless
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Hello everyone!
I took my 1980/82? Bianchi “Claire” out on her maiden voyage, and had a great ride. 😀
the steepest hill I did was a real challenge for me with my 28 on back and 42T chainring.
2) is there a cheaper freewheel I could buy to get me 30 in rear? Can I use a 7 or 8 speed instead of my 13-28?
I took my 1980/82? Bianchi “Claire” out on her maiden voyage, and had a great ride. 😀
the steepest hill I did was a real challenge for me with my 28 on back and 42T chainring.
2) is there a cheaper freewheel I could buy to get me 30 in rear? Can I use a 7 or 8 speed instead of my 13-28?
Can you pull the wheel off and take a picture straight on to the sprockets and close up (just need to see the sprockets)?
If this is the case, you are sitting pretty and can build your own 7-8 speed cassette from a new SRAM, Sunrace, Shimano, etc., HG compatible cassette. Before I explain how, post the picture so I can confirm.
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#19
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While the above is not the best picture to say with certainty, I believe your bike is not running a freewheel, but is instead equipped with a Shimano Uniglide Freehub cassette. I do not see any space for a removal tool. This is why I don't believe you have a freewheel. Also, the color of the sprockets are the color Shimano used on UG cassettes, back in the '80s.
Can you pull the wheel off and take a picture straight on to the sprockets and close up (just need to see the sprockets)?
If this is the case, you are sitting pretty and can build your own 7-8 speed cassette from a new SRAM, Sunrace, Shimano, etc., HG compatible cassette. Before I explain how, post the picture so I can confirm.
Can you pull the wheel off and take a picture straight on to the sprockets and close up (just need to see the sprockets)?
If this is the case, you are sitting pretty and can build your own 7-8 speed cassette from a new SRAM, Sunrace, Shimano, etc., HG compatible cassette. Before I explain how, post the picture so I can confirm.
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I believe I have some similar hubs. Some are deep enough for more speeds than others but all can take modern freehub sprockets if the sprockets are slightly modified. You have an incredibly versatile hub there!
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Thanks Russ! When you say sprockets, do you mean cassettes? Sorry just trying to nail down this terminology, it's a tad bit confusing for me!
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You will also need two chain whips to remove the outer sprocket.
This hub is similar to yours. I have built a custom cassette out of modern sprockets.
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#23
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okay thanks for explaining all that. Could you please tell me about your set up that looks like a huge low gear on an older bike, love it! How does that older derailleur handle the big sprocket?
yes, cassettes. The modern ones have slots in the hub with one slot a little wider to orient the sprocket so that indexed shifting works better. Your hub probable has all equal sized slots. The modern sprocket will need filed in one spot to fit. You will lose a little bit in terms of index shifting but I never noticed because I friction shift.
You will also need two chain whips to remove the outer sprocket.
This hub is similar to yours. I have built a custom cassette out of modern sprockets.
You will also need two chain whips to remove the outer sprocket.
This hub is similar to yours. I have built a custom cassette out of modern sprockets.
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To answer the original question, yes, it makes a difference. I got a 1982 Lotus Supreme this Spring that came with a 52/43 crankset and a 13-23 cassette. I found a 39 tooth chainring and a 13-26 cassette, and it made a BIG difference. I also got another bike with 52/40 and a 13/32 cassette, which did give me lower gears but I found the jumps to be too large, both because the cadence changes were too much AND because the derailleur required overshifting then backing off in order to change gears. I put a 13-26 on it and it shifts MUCH better.
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