Gearing again

For discussions about bikes and equipment.
molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Gearing again

Postby molzor » 4 Aug 2018, 8:16pm

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
Posts: 641
Joined: 10 Jan 2008, 8:44pm
Location: Highland Heights Kentucky,, USA

Re: Gearing again

Postby scottg » 4 Aug 2018, 10:51pm

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.
+++++++++++++++++++++++++++++++++++++
Why not the best, buy Cyclo-Benelux.

Brucey
Posts: 35525
Joined: 4 Jan 2012, 6:25pm

Re: Gearing again

Postby Brucey » 4 Aug 2018, 11:02pm

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
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Eyebrox
Posts: 252
Joined: 5 Aug 2015, 8:56pm
Location: Ayrshire

Re: Gearing again

Postby Eyebrox » 4 Aug 2018, 11:06pm

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
Posts: 35525
Joined: 4 Jan 2012, 6:25pm

Re: Gearing again

Postby Brucey » 4 Aug 2018, 11:09pm

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
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Eyebrox
Posts: 252
Joined: 5 Aug 2015, 8:56pm
Location: Ayrshire

Re: Gearing again

Postby Eyebrox » 4 Aug 2018, 11:12pm

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

Valbrona
Posts: 2221
Joined: 7 Feb 2011, 4:49pm

Re: Gearing again

Postby Valbrona » 4 Aug 2018, 11:14pm

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.
I should coco.

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Tigerbiten
Posts: 1902
Joined: 29 Jun 2009, 6:49am

Re: Gearing again

Postby Tigerbiten » 5 Aug 2018, 12:05am

Eyebrox wrote: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 .......... :D

molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 5 Aug 2018, 4:30pm

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
Posts: 35525
Joined: 4 Jan 2012, 6:25pm

Re: Gearing again

Postby Brucey » 5 Aug 2018, 4:45pm

molzor wrote:….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
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 5 Aug 2018, 4:56pm

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

djnotts
Posts: 1201
Joined: 26 May 2008, 12:51pm
Location: Nottingham

Re: Gearing again

Postby djnotts » 5 Aug 2018, 6:34pm

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
Posts: 149
Joined: 5 Aug 2011, 3:11pm

Re: Gearing again

Postby the snail » 5 Aug 2018, 7:17pm

djnotts wrote: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.

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hondated
Posts: 2355
Joined: 27 Mar 2008, 7:59am
Location: Eastbourne

Re: Gearing again

Postby hondated » 5 Aug 2018, 7:53pm

molzor wrote: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
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 5 Aug 2018, 8:21pm

hondated wrote:
molzor wrote: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!