Changing a chainset...
Discussion
You live and learn it'll seem. I've realised I have no need for a triple and would like to change for a compact after covering around 150 miles on my Trek 1.5 triple...
I could not just use it, but trying not to cross chain and now mainly out of pride, I really can't find the right gear I should be in going uphill. I realise this could be combatting by just getting on with it in a higher gear, but if I'm going to change it later on I may as well do it now.
So I'm currently running 50/39/30 chainrings and a 11-26 9 speed rear cassette, with a triple front derailleur and a triple shifter. The current rings have some markings like 130 BCD S-9 and a marking saying 172.5 on the rear of the arm.
Full spec here: http://www.evanscycles.com/products/trek/15-triple...
Looking to replace with something like this:
http://www.chainreactioncycles.com/Models.aspx?Mod...
Is this going to work? Will I need a new front derailleur? BB Cups? I've no idea what they are? Can I just swap it out add the new one in and away I go. What difference will the arm length make? Is the above a decent enough chainset? Will I need to change the chain? The cassette?
So many questions....
I could not just use it, but trying not to cross chain and now mainly out of pride, I really can't find the right gear I should be in going uphill. I realise this could be combatting by just getting on with it in a higher gear, but if I'm going to change it later on I may as well do it now.
So I'm currently running 50/39/30 chainrings and a 11-26 9 speed rear cassette, with a triple front derailleur and a triple shifter. The current rings have some markings like 130 BCD S-9 and a marking saying 172.5 on the rear of the arm.
Full spec here: http://www.evanscycles.com/products/trek/15-triple...
Looking to replace with something like this:
http://www.chainreactioncycles.com/Models.aspx?Mod...
Is this going to work? Will I need a new front derailleur? BB Cups? I've no idea what they are? Can I just swap it out add the new one in and away I go. What difference will the arm length make? Is the above a decent enough chainset? Will I need to change the chain? The cassette?
So many questions....
Looking at the spec of the bike, it has an FSA Vero chainset which Chain Reaction also sell in a compact version: http://www.chainreactioncycles.com/Models.aspx?Mod...
and the Gossamer Pro has an integrated bottom bracket so for simplicity / compatibility you might be better off going for another Vero.
It's not as simple as just changing the chainset though, you'll also need a double shifter, only sold in pairs http://www.chainreactioncycles.com/Models.aspx?Mod... and a double front mech http://www.chainreactioncycles.com/Models.aspx?Mod... and I'm not 100% certain but you may also need to replace the bottom bracket for one with a different length axle. If you're not doing the work yourself, ask your LBS for advice as when I worked in a bike shop the only bikes with triple chainsets were mountain bikes and tourers and road bikes had 14 gears tops!
One other thing to be aware of is that a lot of bikes with a triple chainset will also have a medium or long cage rear derailleur to cover the wide range of gears which would end up being too long once you switch to a double chainset. The picture on the Evans website shows a bike with a double chainset and a short cage rear mech so you'd need to check which rear mech you have and replace with a short cage version if necessary.
Crank length won't make a massive difference if you've already got 172.5mm and buy a size up or down as you'll get 170 or 175 giving a 2.5mm difference either way. The 172.5s are probably specced as being "about right" for the frame size you have but without a bike fitting would only be approximate. As the Vero cranks come in that length and are available from CRC you may as well get the same size again.
Personally, having just spent £800 on a bike I'd just bite the bullet and leave it as it is rather than spend a couple of hundred plus to actually remove something. Just because it's there doesn't mean you have to use it....
The bottom gear on my road bike from 1990 is 42 x 21 and yes I've done the Beacon on it.
and the Gossamer Pro has an integrated bottom bracket so for simplicity / compatibility you might be better off going for another Vero.
It's not as simple as just changing the chainset though, you'll also need a double shifter, only sold in pairs http://www.chainreactioncycles.com/Models.aspx?Mod... and a double front mech http://www.chainreactioncycles.com/Models.aspx?Mod... and I'm not 100% certain but you may also need to replace the bottom bracket for one with a different length axle. If you're not doing the work yourself, ask your LBS for advice as when I worked in a bike shop the only bikes with triple chainsets were mountain bikes and tourers and road bikes had 14 gears tops!
One other thing to be aware of is that a lot of bikes with a triple chainset will also have a medium or long cage rear derailleur to cover the wide range of gears which would end up being too long once you switch to a double chainset. The picture on the Evans website shows a bike with a double chainset and a short cage rear mech so you'd need to check which rear mech you have and replace with a short cage version if necessary.
Crank length won't make a massive difference if you've already got 172.5mm and buy a size up or down as you'll get 170 or 175 giving a 2.5mm difference either way. The 172.5s are probably specced as being "about right" for the frame size you have but without a bike fitting would only be approximate. As the Vero cranks come in that length and are available from CRC you may as well get the same size again.
Personally, having just spent £800 on a bike I'd just bite the bullet and leave it as it is rather than spend a couple of hundred plus to actually remove something. Just because it's there doesn't mean you have to use it....
BliarOut said:
I did Ditchling Beacon on 26F/21R, what kind of hills are you talking about? 
....unless you're BliarOut of course. The bottom gear on my road bike from 1990 is 42 x 21 and yes I've done the Beacon on it.
I looked into this with my Trek 1500 and with all the bits that would need replacing have just decided to leave it. I see it as a challenge to myself not to use the 'granny ring' and therefore end up trying to power up hills in the 42 tooth middle but manage and I live in Bath at uni and Cornwall at home so it's not easy. A friend keeps mentioning that I can in theory 'lock' it out of the bottom ring so that I can't change down to it but I'm not sure how I'd go about doing that and it's not really an issue, I just don't use it.
AyBee said:
A friend keeps mentioning that I can in theory 'lock' it out of the bottom ring so that I can't change down to it but I'm not sure how I'd go about doing that
You would adjust the limit screws so that the mech cannot drop further than the middle chainring, so it doesn't matter if you shift past the middle ring on the shifters, the mech won't move.Back to OP, for the cost involved of new front shifter and chainset, you're probably better off selling your bike and getting a new one with a compact double already fitted.
I really wouldn't bother personally but if you insist:
Simply unbolt and remove your inner chainring and tighten the inner adjusting screw on your front mech until the chain doesn't go past the middle chainring. It won't cost you a penny.
If 1st gear is now too high for climbing simply replace your cassette with an 11-28 or 11-29. If you need lower than this you should stick with the triple!
No need to change the rear mech at all.
Simply unbolt and remove your inner chainring and tighten the inner adjusting screw on your front mech until the chain doesn't go past the middle chainring. It won't cost you a penny.
If 1st gear is now too high for climbing simply replace your cassette with an 11-28 or 11-29. If you need lower than this you should stick with the triple!
No need to change the rear mech at all.
Edited by Roman on Thursday 1st July 18:19
Gassing Station | Pedal Powered | Top of Page | What's New | My Stuff