dirtydozen

Hello,

I have a roadbike with 50-39-30 chainrings and 11-26 at the back.

My father will need smaller gears in order to ride in the mountains this summer. My bikeshop told me that I needed to replace everything in the drivetrain but in the past they already made few drastic statements which weren't necessary true, they just wanted me to buy more stuff.

So my question is, can I buy on the internet a smaller 3rd ring (a 28) and just put it on myself ? I will also change the K7 (small rings at the back idk really how to say it in english) to have a 30 or maybe a 32 at the back, the bikeshop will do this because i don't have the tools required (or maybe it's not that hard to do ?)

I also have another bike that we used as a hometrainer bike which was bought in 1996. I was wondering if it was possible to put the K7 and chainrings of a newer bike (trek 1.2 2011) on the old bike, and if I do so, i would put entirely new drivetrain on the trek 1.2 2011 so my father can use it (but then I guess i need to change the levers on the old bike because it's some old 7speed campagnolo)

can you guys share your experiences with changing gears between bikes or buying new drivetrains ?

thanks in advance

Elvo

You will need a longer chain and quite possibly a long cage derailer. You will need to find a new derailer that is compatible with your drive chain (assuming it exists).

noodle soup

It sounds highly unlikely that you need to replace everything, unless everything is heavily worn. Most likely a 11-30(or even larger) would work just fine, but a new chain might be needed too.

dirtydozen

Ok thanks so I will do just that. Get a 28 chainring, a new cassette and chain and put everything on my trek 1.2 so my father can ride it

this means I'm getting a new bike yay


thanks for your input. i think i will forget about the old bike, there is too much to replace on it, i can just find a decent used bike for the same ammount

cyclintom

You didn't tell us what group and number of speeds you have. Most triples can get down to a 26. But the number of speeds on the rear is questionable. 7 or 8 speed freewheels or cassettes are very difficult to get lower than a 26 though sometimes you can get a 28. If you have a 9 or 10 speed rear you can go all the way down to a 32 or even lower rear though the rear derailler would probably have to be changed to a long-arm as well. With 11 speeds you can get mountain bike gearing all the way to a 42.

Remember that people that don't climb a lot cannot sustain climbing no matter how low a gear they have. What you gain in the requirement for less leg strength you lose by the slower speed taking so much longer to get up a climb. So you're exchanging too little leg strength for too little endurance.

dirtydozen

So, I'm gonna change 1 chainring and the cassette of my actual bike which has 9 speeds (50-39-30 and 11-26), sora all the way except for the Tiagra rear derailleur. 2011 bike so not brand new sora, it even has thumbshifters.
My old bike I think its a campagnolo mirage, not quite sure. It has 7 speeds but this bike is out of the question now, as I would need to put a whole new groupset on it.

I guess a 50-39-28 would work, but would a 50-39-26 work ? or would I need to replace all 3 chainrings to do a 48-38/36-26 or something around those lines ?
That's some good news, if I can put a 11-32 with a 26 or 28 chainring that would be great for him!

That's a good point! He has pretty good endurance so I think with the right gears for him he will be able to do some climbs, he already did one 2 years ago with a heavy mountainbike

Thank you very much!

fietsbob

front; 24 replaces the 30,... rear a long cage RD and a 12~34t cassette.. & new chain.

I don't know anything about your mechanical skills to say anything about you doing it...

if in doubt pay a bike shop..


24:34 is my touring bike low.




....

noodle soup

I’m just guessing that a bike that came with a triple can handle the changes you want to make. If everything is heavily worn, that changes things.

dirtydozen

Thanks! I think 32 at the back will be enough, specially if I end up putting a 26 or even 24 as you suggest. I would like to make those changes as cheap as possible and I don't think buying a long cage RD is necessary in my case, but i'll keep that in mind if I need to change the RD anyway.

Components are not brand new but it's not heavily worn either. I maybe rode 3000 to 3500km on it. I remember doing the chain worn test and it was doing ok, sadly Im living abroad now and next time i will see the bike is at the bottom of the first climb

fietsbob

Do the Math ... tooth count sums (big +big) - ( small+ small ) is how much chain slack has to be taken up.

Racing Dan

If you are changing both the cassette and the small chain ring you may want to look in to the total capacity of what ever rear derailleur you put on. The latest RD-R3000-GS has a total capacity of 43t, but Im betting the older ones are less than that.

cyclintom

MEASURE the inner chainring. If it is 80 mm you can fit a chainring from TA on it in size 26. https://www.sheldonbrown.com/cribsheet-bcd.html

Remember that these small chainrings often require long cage rear derailers as well.

noodle soup

excessive wear won’t be an issue then.

noodle soup

I suspect his bike already does have one, but it would be helpful if the OP posted a good photo of his drivetrain, or a detailed list of the components.

cyclintom

No doubt you're right but the 9-speed stuff was sort of confusing. You could use a short cage derailer on a 30 tooth triple and a 28 large tooth cassette if memory serves.

dirtydozen

That's very useful thank you!

Is there a method to be sure that my derailleurs will be able to support 28 or smaller chainrings ?

noodle soup

these limits are easy to figure out, if we know what derailleurs you have.

dirtydozen

https://www.culturevelo.com/2011-1-2 (its possible to zoom on the picture simply by putting the cursor on the bike)

I can't send pictures of my bike for the moment but i didn't change anything in the drivetrain area anyway.

From shimano's wikipedia page I can guess the rear derailleur is a Tiagra 4500 and the rest is Sora 3400

I found that the total capacity of the Tiagra 4500 is : SS 31T, GS 37T. The total capacity in my current set up is 35 so it means I have the Tiagra 4500 GS and that I am allowed for 37. So the 50-38-28 with 11-30 is not possible but now at least I can know which combinations would work, thanks a lot !!

I struggle to find a lot of infos about this RD since it is getting old, i found this website : https://www.modernbike.com/product-2126176854
So looks like the largest cog supported is 27 so that is not good.
Does anyone know what is the chain wrap capacity ?