Can i change to a smaller chainring on my chainset?

ILM said:

I have a specialized Allez double 18 speed. evanscycles.comallez 18 2008 road bike ec001390Open ↗

I'm struggling up some steep hills and was wondering if firstly I could swap my 34t chainring to a 30t and if so is it worth it?? the large chainring is a 52.
If I change to a triple then I need to buy a new left sti shifter, whole crankset and ? front derailleur. Reason I ask is that I have seen Tiagra triples with a 52,39,30t chainring, so all I'm doing is missing the middle ring out, is that do-able or not??

The smallest chainring that will fit on your chainset is a 33t ... and, it will be fairly expensive.

However, you can buy an MTB rear derailleur (for example, an LX -- NOT 'rapid rise' ... although I have considered using a 'rapid rise' rear derailleur with a set of Shimano ROAD shifters in the past) + an 11-32 LX cassette ... depending on where you buy the two items, your cost will probably be between £25 to £50.

ok, sounds like i may need a triple chainset instead, I've seen some on ebay, fairly priced, how do I know if my sora 9 speed flightdeck will work with triple chainset instead of my double at present??

ILM said:

ok, sounds like i may need a triple chainset instead, I've seen some on ebay, fairly priced, how do I know if my sora 9 speed flightdeck will work with triple chainset instead of my double at present??

Well, that's not what I indicated ...

And, it will be less expensive to do what I suggested ...

AND, having a cog with 4 more teeth to the rear will be more meaningful than having a chainring with 4 less teeth.

ILM said:

ok, sounds like i may need a triple chainset instead, I've seen some on ebay, fairly priced, how do I know if my sora 9 speed flightdeck will work with triple chainset instead of my double at present??

BTW. You'll need a new BB, a new front derailleur + a new rear derailleur if you want to switch to a triple chainset.

Your Sora shifters should work with a triple; but, maybe not. AFAIK, only the Dura Ace & Ultegra have "left"/front shifters which are EITHER double-only or triple-capable whereas I believe that the 105-and-below shifters are triple compatible.

hi

I misread your response, have found the cassette you've mentioned relatively cheap and also some rear derailleurs, inparticular the deore LX but what I don't understand is why I cant use this cassette with the tiagra rear I already have, could you explain please.

thanks

ILM said:

I misread your response, have found the cassette you've mentioned relatively cheap and also some rear derailleurs, inparticular the deore LX but what I don't understand is why I cant use this cassette with the tiagra rear I already have, could you explain please.

Well the thing to do is to try your current rear derailleur and see if it will work with the 11-32 cassette ... it may ... I just don't know the specs on the pulley wheels -- that is, whether the upper/lower jockey wheels on the Tiagra only have 10t OR if they have 11t.

If the Tiagra rear derailleur has 10t pulley wheels, then you are probably good-to-go ...

EXCEPT for the total chain capacity ... this is more of a non-/nuisance situation ...

Because, your bike was spec'd with a SHORT cage rear derailleur ... that means that you cannot have a long enough chain whereby the chain can be on the larger chainring & largest cog at the same time (something that shouldn't be done intentionally, anyway) ... that is, if your largest cog goes from 28t to 32t then you would theoretically want a chain that is two inches longer than is currently on your bike ... and therefore, you would want a rear derailleur with a longer pulley cage.

If you eventually put a chain on that has the 'proper' length for the NEW maximum combinations, then the cage will not have the capacity to prevent the drivetrain from having too much slack when using the inner chainring & the smaller cogs (again, something that shouldn't be done intentionally) ...

I think that having a slack chain is more of a cosmetic issue with a ROAD bike ... but, it can be problematic on a MTB, particularly one with a rear suspension that is bobbing along on uneven terrain.

Since 'I' don't mind dragging a little extra chain around to allow for the extreme cassette variations, I almost always choose a MTB rear derailleur for my ROAD bikes ... and, that is why I reflexively suggested you do the same -- you may deem it to be unnecessary.

alfeng said:

BTW. You'll need a new BB, a new front derailleur + a new rear derailleur if you want to switch to a triple chainset.

Your Sora shifters should work with a triple; but, maybe not. AFAIK, only the Dura Ace & Ultegra have "left"/front shifters which are EITHER double-only or triple-capable whereas I believe that the 105-and-below shifters are triple compatible.

Triple AND double for 105 and below. The triple DA(7800, not 7900) and ultegra are also triple AND double. Why shimano even makes a double only left shifter escapes me.