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I currently run Tiagra triple 9 speed crank, 50/39/30 The BCD on the 50 being 130mm. I'd like to replace the 50t with a 52t to make it 52/39/30. I'm looking at a Shimano 105 52t chainring but it says it's intended for a double crank and 10 speed drivetrain.

But you think I can make that ring work in my setup?

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Strictly speaking you should keep with 9-speed rings, as the teeth on a 10-speed ring will be dimensioned to fit a 10-speed chain. But the difference is very small and I reckon lots of people will be successfully running this kind of setup. Bear in mind, if you can find Ultegra 6500, this is also a valid 9-speed option (and great quality). –  PeteH Aug 1 at 16:00
    
what would be the 9 speed equivalent in shimano 105? i'd rather a 9 speed but can't find any on ebay or anything. –  towpse Aug 1 at 16:41
    
it's hard to find 105 that's strictly made for 9 speed –  towpse Aug 1 at 16:47
    
looks like it is 5500. Found this link which might help. Don't think I ever saw 9sp 105 on sale, I reckon its pretty rare. –  PeteH Aug 1 at 16:48
    
9-speed/10-speed shifting-related issues aside (negligible), the only thing to watch is your rear derailleur take-up capacity. If it's already maxed out, it might not like being stretched out to top capacity. Obviously you shouldn't be running the big ring with big cogs anyway, but if you're right on the limit and accidentally shift into that gear combination, there's a slim chance of locking up the drivetrain. But probably negligible. –  headeronly Aug 1 at 19:48

3 Answers 3

Should work fine, assuming the BCD on the 105 52t chain ring is also 130 mm (and not 110 mm - compact). The 105 chainring will be profiled ever so slightly thinner for the 10 speed chain, but will not affect 9 speed performance. Make sure to orient the new ring in the correct position with the small metal tab (that catches an errant chain) pointing toward the crank arm.

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the ring i'm eyeing is Shimano 105 5700 52t 130mm 10-Speed Chainring Black. So it sounds like I should be aware that the 10 speed chainring will be slightly thinner meant to accommodate a 10 speed chain; but the 9 speed chain should still work. Should I be concerned with any possible front derailleur issues? is 52/39/30 combo ok? I think it's more standard to be 52/42/3x (thirty something....) –  towpse Aug 1 at 16:36
    
9 speed chain will work fine, the derailleur will be fine. Recall that you wear away your rings through use, but your derailleur still works fine. Running a 10 speed chain on a 9 speed ring may give you more grief however, although I bet it would still be quite functional. –  Rider_X Aug 1 at 17:14
    
why does it matter for the manufacturer to specify that a chain ring is for a double, rather than a single or triple? check out the package here ebay.ca/itm/Shimano-Chainring-5700-130x52T-B-Type-Black-/… –  towpse Aug 1 at 17:35
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I'd guess the ramps are slightly differently designed to account for the different jumps on a triple and double, but it likely doesn't make a huge difference in reality. –  Batman Aug 2 at 0:53

First, consider this; can you spin out the 50t? If not, there isn't anything to be gained by going to a larger chain-ring. At a cadence of 90rpm and a 50t x 11t will yield over 32mph & a speed of about 42.5mph could be attained with 120rpm. Even with 50t x 13t & 90rpm, the speed would be close to 28mph. If you make the switch, you may find the front derailleur can't handle the larger chain-ring, so check the specs first. Older Tiagra derailleurs could handle up to 53t, but the design was changed for better shifting, and the current model specification shows a top gear of 50t with a range of 20t (meaning the difference between the large chain-ring & the small ring can be no more than 20t, ie. with a 50t outer ring the inner ring could be no smaller than 30t)

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As long as your front derailleur can be adjusted vertically to accommodate the 52tooth chainring, the drivetrain should run fine.

The jumps between gears is not large so shifting would likely not be a problem but this will not be the quietest of drivetrains.

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