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Chainrings on Road Bike


julianp.oosthuizen
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I have a 8 speed entry level tiagra set up on my bike. I am battling on long hills and looked at an bigger cassette with no luck. Question is. I see there is 52 36 chainrings where my current is 53 39 even I count about 42 teeth on the inner chainring. Has anyone done a cheep not expensive upgrade on similar set ups. . I'll rather save up for a bike with better spec than spend on full upgrade.

 

Bike is Silverback Arizona

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There are a few things to consider which may not make it as cheap as you think. Rather get it to a bike shop and get them to confirm.

 

I'm not sure of the exact technicalities, but smaller chainrings often have a smaller BCD (Bolt Circle Diameter) which means it may not fit on your current crank. You may have to replace the whole crank.

 

Also, a smaller chainring means more "chain slack". You may also need a longer cage derailleur to take up that slack.

 

Also bear in mind that drivetrain parts generally wear with each other. So depending on how far your current chain ring has worn, you might need a new chain if you are going to put on a new chain ring. A new chain, might depending on how far your current cassette has worn, might require a new cassette.

 

Maybe some of the technical guys on the Hub can tell you if you will need these new items.

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I had the same problem with an old 8 speed road bike at home, I ended up buying a 32/12 cassette for the back wheel on eBay UK and getting someone to bring it back for me. Also put on a derailleur extender which you can get on Aliexpress for a couple of dollars (postage is long on this unfortunately). This is required if the large teeth at the back are too big for the derailleur.

 

A more expensive alternative would be to put a triple crank on the front, the double front derailleur can work with a triple crank, I am using one on the same bike. You would need a longer cage rear derailleur to take up the chain slack if you have a triple in front, as Longbarn Killer comments.

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I've done similar before on my previous bikes. Cant say I experienced any negatives.

It was an older bike though and changing the chainrings was as simple as bolting them off and on.

 

But i'd suggest having a look at a bike gear calculator, punch in the gear ratios you have, then play around with the purposed new ratios and see the difference it will make.

 

I wanted to change the small chain ring on my previous bike, popped into the late Frans Buys' shop and explained what I wanted to do, he pulled out a calculator, showed me the differences and we landed up only changing teh largest cog on teh cassette.

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The sad thing is that chain rings are not much cheaper than the whole crank.  If you are on eight speed the guts of your groupset is probably Sora - to the best of my knowledge Tiagra was introduced as a 9 speed.  When looking at a replacement crank keep in mind that you will most likely need a different BB as well.

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Also, a smaller chainring means more "chain slack". You may also need a longer cage derailleur to take up that slack.

 

Only if you leave the chain the same length (which you shouldn't). That said if you are only changing the smaller chainring and not the big one as well you might not be able to shorten the chain.

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