Replace the Crank
I want to replace my old -but still good- 52/42 Shimano 105 crank with a 50/34 Shimano Sora (cheap), because i need an easier gear.
is it worth it? Will it effect the bike speed/performance? The 50/34 Shimano Sora i want to buy :https://www.decathlon.es/es/p/pedali...937?mc=8511779 My bike: https://cimg4.ibsrv.net/gimg/bikefor...f34c46f4cc.jpg |
It will work but you’ll need a new bottom bracket
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Originally Posted by mawn
(Post 22907861)
I want to replace my old -but still good- 52/42 Shimano 105 crank with a 50/34 Shimano Sora (cheap), because i need an easier gear.
Edited to add a simple drawing to help explain. Obviously not to scale, but just to show where I had the problem. https://cimg5.ibsrv.net/gimg/bikefor...7c97cf926.jpeg Dan |
Originally Posted by _ForceD_
(Post 22907986)
There’s one issue you ‘might’ encounter going from a 42 down to a 34 with the small ring. The smaller circumference of the 34 changes the angle of the chain back to the gears and could cause it to snag on the large ring.
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Who the HELL uses small/ small?? There is ZERO NEED.
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Assuming your 52-42 is 130 bcd, you could go to a 38 tooth small ring, the smallest that will fit on that bcd. Match that up with a cassette with lower gears to get even more low end. In regards to replacing the whole crank set, as stated above, likely going to need a new bb, only you can decide if it is worth it to you. What you are proposing is not that much cost, and relatively easy to do. I would do it if I truly thought it was going to be a plus to riding the bike.
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Originally Posted by HillRider
(Post 22907988)
Current 50/34 (aka "compact") cranks are so common that the chain interference issue has been long dealt with. Yes, a 53/34 crank can have snagging problems but not a 50/34 the OP is asking about.
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Originally Posted by SoSmellyAir
(Post 22908117)
It has been "dealt with" in the sense that Shimano tells us not to do it. For example, with the latest 2x11 drivetrain, Shimano dealer manual expressly states that there would be chain rub and noise while riding in the small chain ring with the four smallest cogs.
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Depending on which RDER you have, you may be able to accomplish lower gears with a simple cassette change.
OR cassette & RDER. |
Originally Posted by t2p
(Post 22908147)
some FD’s have a trim / ‘intermediate’ position that can reduce or eliminate the chain rub (when riding small ring with the smallest cogs)
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Originally Posted by Germany_chris
(Post 22907883)
It will work but you’ll need a new bottom bracket
Originally Posted by _ForceD_
(Post 22907986)
There’s one issue you ‘might’ encounter going from a 42 down to a 34 with the small ring. The smaller circumference of the 34 changes the angle of the chain back to the gears and could cause it to snag on the large ring. I wanted to change from a 52/42 setup to a 53/38. Once re-assembled, everything ran OK in the middle gears. However, the angle of the chain from the new/smaller ring back to the smallest gear caused it to snag on the large 53 ring. So I changed the small ring to a 39 and that increased the circumference jus enough so that it doesn’t snag on the large ring. Given that you’re also going down to 50 on the large ring ‘might’ allow clearance. But it’s and issue you might run into.
Edited to add a simple drawing to help explain. Obviously not to scale, but just to show where I had the problem. https://cimg5.ibsrv.net/gimg/bikefor...7c97cf926.jpeg Dan
Originally Posted by GamblerGORD53
(Post 22907999)
Who the HELL uses small/ small?? There is ZERO NEED.
Originally Posted by delbiker1
(Post 22908073)
Assuming your 52-42 is 130 bcd, you could go to a 38 tooth small ring, the smallest that will fit on that bcd. Match that up with a cassette with lower gears to get even more low end. In regards to replacing the whole crank set, as stated above, likely going to need a new bb, only you can decide if it is worth it to you. What you are proposing is not that much cost, and relatively easy to do. I would do it if I truly thought it was going to be a plus to riding the bike.
Originally Posted by Bill Kapaun
(Post 22908171)
Depending on which RDER you have, you may be able to accomplish lower gears with a simple cassette change.
OR cassette & RDER. |
RDER = Rear derailleur
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Originally Posted by GamblerGORD53
(Post 22907999)
Who the HELL uses small/ small?? There is ZERO NEED.
the cross-chain test is part of every multi-gear setup in my shop. and if the chainline is good, there is no major issue to remedy... a bit of der. fiddling and out the door it goes. |
Hollowtech II bottom Bracket... https://www.theproscloset.com/produc...ttom%20Bracket
Tool to install/remove Hollowtech II BB... https://www.rei.com/product/799545/p...53b9ffd53989e3 these are images to show the Part and tool.. You should shop for the best deal in your area.. or go to your Local Bike Shop for parts and/or installation |
Originally Posted by mawn
(Post 22907861)
I want to replace my old -but still good- 52/42 Shimano 105 crank with a 50/34 Shimano Sora (cheap), because i need an easier gear.
is it worth it? Will it effect the bike speed/performance? The 50/34 Shimano Sora i want to buy :https://www.decathlon.es/es/p/pedali...937?mc=8511779 My bike: https://cimg4.ibsrv.net/gimg/bikefor...f34c46f4cc.jpg Your RDER is also a longer cage (GS) version of the series normally used for a triple crankset. Regarding your RDER, it should be rated for a 27 teeth largest sprocket on the cassette. Most people report going a tooth or 2 higher is possible. |
I think you'll find the 50-34 more useful than what you have and the new style bottom bracket will be much easier to deal with in the future. Sounds like a good plan.:thumb:
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Originally Posted by KCT1986
(Post 22908298)
Have you checked that the current crank is just a double? The 52/42 rings are standard on a triple for this 105 (FC-55??) and your smaller ring looks that it has shift pins for shifting from a third small chainring. The actual part number should be stamped on the back of the crank arm, right next to where the pedal mounts.
Your RDER is also a longer cage (GS) version of the series normally used for a triple crankset. Regarding your RDER, it should be rated for a 27 teeth largest sprocket on the cassette. Most people report going a tooth or 2 higher is possible. |
Originally Posted by mawn
(Post 22908409)
its a triple "Shimano SG A-52-42-30", the previous owner removed the 30.
The Crank swap will be the easiest, and best choice for lowest price total, eh? the "triple" install will have other hidden costs too... possibly shift cable, cable housing, bar tape(depending on Shifters used), and possibly a rear derailleur... installing a hollowtech II crank is easy.. remove pedals, remove old crank and bottom bracket, CLEAN everything, put a dab of grease on the BB threads, install Bb, slide new crank in place, side new Left crank arm on, tighten clamp screws, adjust chain length and front derailluer,.. then go ride! |
Originally Posted by SoSmellyAir
(Post 22908117)
It has been "dealt with" in the sense that Shimano tells us not to do it. For example, with the latest 2x11 drivetrain, Shimano dealer manual expressly states that there would be chain rub and noise while riding in the small chain ring with the four smallest cogs.
Edit: Ways to get past the FD-shifter compatibility issues - go friction in front. Keep your brifter to match the left but use either a downtube shifter for the front (might be a challenge to mount on your Ridley) or install a bar end shifter on the handlebar. That will allow you my FD cage adjust trick and at least an extra usable cog in back. |
Originally Posted by SoSmellyAir
(Post 22908117)
It has been "dealt with" in the sense that Shimano tells us not to do it. For example, with the latest 2x11 drivetrain, Shimano dealer manual expressly states that there would be chain rub and noise while riding in the small chain ring with the four smallest cogs.
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Originally Posted by mawn
(Post 22908409)
its a triple "Shimano SG A-52-42-30", the previous owner removed the 30.
From the picture it looks like the front derailleur is the triple version of the series, the outer cage has a ridge along lower edge that was only on the triple version. A 30T inner ring would give you great gearing range and also maintain close ratio. |
Originally Posted by mawn
(Post 22908409)
its a triple "Shimano SG A-52-42-30", the previous owner removed the 30.
It should be Shimano PN# Y-16X 30010 The "road" guys could probably tell you what else would fit. How many teeth on the largest cog in back? if 23T, going to a ??-28T cassette would give the same low gear ratio as changing your 42T ring to a 34T. |
Originally Posted by Bill Kapaun
(Post 22908757)
Find another 30T ring I presume you still have the 3 speed L shifter?
It should be Shimano PN# Y-16X 30010 The "road" guys could probably tell you what else would fit. How many teeth on the largest cog in back? if 23T, going to a ??-28T cassette would give the same low gear ratio as changing your 42T ring to a 34T. in the back there's a 9-speed Cassette 13-23. |
Why not a subcompact double 44/28 or 42/26
The rear derailleur cage is long so replace the cassette w/11-34 or 11/36 |
That 9 speed RD, even though a GS, won't take more than +/-27. BITD we replaced them with MTB RDs to use a 32 or 34.
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