Gearing again

[molzor]

Hello,

I currently have a 4700 10 speed triple tiagra groupset. Im thinking about swapping the crankset for something like a deore triple mtb crank.

I have weak legs and struggle on the hills with a minimum 30t on the front when the bike is loaded.

You can get deore triples with a 22 or a 26 but could there be any compatibility issues here? Im trying to read about chainlines and stuff but i don't fully know what im doing.

Thanks for the help!

[scottg]

Replace the granny ring take off the 30t and put on a 24t.
Also what cassette do you have ?
The stock rear mech will go to a 32t.

[Brucey]

http://si.shimano.com/pdfs/ev/EV-FC-4703-3934A.pdf
FC-4703 uses an unevenly spaced 74mm four bolt fixing. Not sure how many smaller chainrings are made for this fitting.

MTB chainsets use a different chainline and chainrings sizes which often causes issues with the FD. Basically an MTB chainset works best with the MTB FD, but the MTB FD won't work with the Tiagra STIs.

A good way out of this bind is to get a triple chainset with smaller chainrings from spa cycles that works with a road chainline.

cheers

[Eyebrox]

Wouldn't it be easier to leave the front and swap the rear mech for a long cage version and change the cassette to a 10spd Deore one with a 42-tooth big cog?

[Brucey]

10s deore mech won't work with Tiagra 10s shifters. The only mechs that are compatible with these shifters are 4700 ones and 'road' 11s ones.

cheers

[Eyebrox]

Didn't know - though I should have. I have seen you mention it a few times. Cheers.

[Valbrona]

You don't just get increased chainline with MTB triples, but also increased stance width. This can be a real bummer for some.

Stronglight Impact Triple is a road-specific crankset that takes small chainrings since it has 74/110 BCD, but it is square taper and only works with a bottom bracket that screws into a threaded BB shell. Miche Race Triple is a modern style 74/110 BCD road-specific triple with integrated axle, thus making if compatible with most press-fit bottom bracket standards.

[Tigerbiten]

Wouldn't it be easier to leave the front and swap the rear mech for a long cage version and change the cassette to a 10spd Deore one with a 42-tooth big cog?

May be easier but ....
It depends if you like the narrow stepping between gears with the 11-30 cassette.
Plus will the wider stepping on an 11-42 give you a bad step somewhere due to the range.
If you like the steps then it would be better to shrink all the chainrings.

Unless you ride with a slow cadence and/or you like to pedal downhill, I think close to a 4:1 chainring:sprocket ratio for top gear is fine.
This will give you just over an 100" top gear or 30 mph downhill.
Then for first gear the sprocket wants to be around 4 teeth bigger than the chainring. That will give you a first gear in the low 20's.
If I was building a derailleur bike, I'd go with something like an 11-28 10 speed cassette and a 46-34-22 triple.
That will give you close to a 500% range with 10%-12% step between most gears.
The only hard part with that type of setup is finding out what MTB parts will work what road bike parts so you can get all the gears working.
But it is doable.

Luck ..........

[molzor]

Well this is much more complicated than it should be...

I could look into a spa road triple but that means changing the bottom bracket too. its hollowtech at the moment.

I spoke to the man in the local bike shop earlier and he seems to think a deore 610 26/36/48 will work? is he wrong?

Thanks for the help everyone, but I think im more confused than ever.

[Brucey]

….I spoke to the man in the local bike shop earlier and he seems to think a deore 610 26/36/48 will work? is he wrong?

well the chainline will be different (wider) and the FD may not reach that far, or it may reach but render some or all of the trim clicks in the shifter next to useless (the shift ratio of the FD varies through the stroke). The interval between the chainrings ought to be the same, and it isn't quite. So it might work, might not, might well enough to think its worth trying and then drive you nuts in the long run.

Choosing the wrong chainset merely to avoid having to buy a £15 bottom bracket (and that isn't guaranteed BTW, the deore uses a slightly different one to the tiagra) is a poor way of prioritising your choice, BTW.

cheers

[molzor]

Ok understood! Thanks brucey!
Ill have to find the BB too

[djnotts]

A second hand Hollowtech2 triple on which you CAN mount a 26/24 inner ring and thus keep b/b and chain line and mech? Plus a chain catcher!

[the snail]

A second hand Hollowtech2 triple on which you CAN mount a 26/24 inner ring and thus keep b/b and chain line and mech? Plus a chain catcher!

Yes, that might work - I'm running 5703 shifters/chainset with 26T ring without issue. Still some 5703 chainsets available I think.

[hondated]

Hello,

I currently have a 4700 10 speed triple tiagra groupset. Im thinking about swapping the crankset for something like a deore triple mtb crank.

I have weak legs and struggle on the hills with a minimum 30t on the front when the bike is loaded.

You can get deore triples with a 22 or a 26 but could there be any compatibility issues here? Im trying to read about chainlines and stuff but i don't fully know what im doing.

Thanks for the help!

Been here bought the T shirt etc Had my bike built with 40-30-22 as I thought I would be climbing many mountains but never have at least not on this bike.
So decided to replace it with 42-32-24 but it still felt like hard work so I then fitted 48-36-26 but still didnt feel right.

Needing advice I posted on here and also sent a pm to a couple of our learned brethren and then decided to buy a Stronglight Impact from 46-36-26 from Spa.
I of cause had to change from Hollowtech BB ut after one mistake I got the correct length BB after talking to Spa.
It cost a few bob to sort out but I have to say its been worth it as I mainly use the two big chain rings and the smaller one is my get me out of jail card. I should however add I have a 11 -34 on the back.
As I always say with anyone with these issues if your near Eastbourne come down and we can try the variations.
If you do decide to stick with Hollowtech and want a 48-36-26 CS Black Deore I have one for sale with BB in its box.

Good luck whatever you do.

[molzor]

Hello,

I currently have a 4700 10 speed triple tiagra groupset. Im thinking about swapping the crankset for something like a deore triple mtb crank.

I have weak legs and struggle on the hills with a minimum 30t on the front when the bike is loaded.

You can get deore triples with a 22 or a 26 but could there be any compatibility issues here? Im trying to read about chainlines and stuff but i don't fully know what im doing.

Thanks for the help!

Been here bought the T shirt etc Had my bike built with 40-30-22 as I thought I would be climbing many mountains but never have at least not on this bike.
So decided to replace it with 42-32-24 but it still felt like hard work so I then fitted 48-36-26 but still didnt feel right.

Needing advice I posted on here and also sent a pm to a couple of our learned brethren and then decided to buy a Stronglight Impact from 46-36-26 from Spa.
I of cause had to change from Hollowtech BB ut after one mistake I got the correct length BB after talking to Spa.
It cost a few bob to sort out but I have to say its been worth it as I mainly use the two big chain rings and the smaller one is my get me out of jail card. I should however add I have a 11 -34 on the back.
As I always say with anyone with these issues if your near Eastbourne come down and we can try the variations.
If you do decide to stick with Hollowtech and want a 48-36-26 CS Black Deore I have one for sale with BB in its box.

Good luck whatever you do.

Very useful post. The stronglight and bottom bracket sounds like the best option i guess. It isnt cheap though at 125 plus the bb

This is what I was looking at using...
https://www.rosebikes.com/shimano-deore ... et-2659081

I did also notice you mention fitting a 34t cassette. I did consider that but the tiagra rear derailleur maunual says it is ok for 34 on a double chainset, but only 32T with a triple!