Narrow q factor triple chainset with steel rings

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reohn2
Posts: 36745
Joined: 26 Jun 2009, 8:21pm

Re: Narrow q factor triple chainset with steel rings

Postby reohn2 » 1 Aug 2019, 9:10am

Brucey wrote:
NickJP wrote:
fatboy wrote:I use brifters so ramp and pinless won't work for me.

From my experience they work fine...


as mentoned previously it depends on the sizes used as well as the rider. If you are used to ramps and pins and try to use some quite common combinations of sizes, it can be extremely troublesome to many (most) riders.

cheers

The shift on two bike 24t Spa's own inner ring to 39t plain Stronglight ring is flawless,one bike on friction and one on Deore MTB pods.Road STI's are just a as good even on tandems.
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I cycle therefore I am.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Narrow q factor triple chainset with steel rings

Postby Brucey » 1 Aug 2019, 9:22am

try the same thing with (say) a 30-39-52 triple and it will almost certainly drive you berserk.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

reohn2
Posts: 36745
Joined: 26 Jun 2009, 8:21pm

Re: Narrow q factor triple chainset with steel rings

Postby reohn2 » 1 Aug 2019, 9:51am

Brucey wrote:try the same thing with (say) a 30-39-52 triple and it will almost certainly drive you berserk.

cheers

I've tried it with 24 and 26/34 and 36/46 and 48t rings and it well.
I've never ever needed anything as big 52t outer and found the above combinations work well together with my cassettes of choice.
Last edited by reohn2 on 1 Aug 2019, 2:49pm, edited 1 time in total.
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I cycle therefore I am.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Narrow q factor triple chainset with steel rings

Postby Brucey » 1 Aug 2019, 10:29am

this isn't widely understood but it rocket science either; there are two main things that make the use of pins and ramps desirable if not mandatory on a (modern) triple


a) a big to middle interval of more than 10T.

b) a middle ring that is smaller than the average of the other two chainring sizes.


The first of these causes the middle to small shift to become increasingly troublesome because the FD is simply rather high vs the middle ring.

The second of these typically causes the inner to middle shift to become increasingly difficult; a typical result is that the shift won't go and then as the FD is pushed further the chain derails straight to the big ring instead.

Fortunately the typical changes that touring cyclists make to their triple gearing usually don't provoke these kinds of problems; it is most commonly the case that the big ring is made smaller (which helps with both a) and b) ) and/or that the inner ring is made smaller (which helps with b) ).

If you make both inner and big rings smaller by 2T or more, the need for ramps and pins usually becomes very greatly diminished.

In most cases where pins and ramps are used (despite not falling foul of a or b above) they allow better shifting under a wider range of conditions which is of benefit for less skilled riders and/or for shifts that are made under duress (eg on MTBs when the gradient changes suddenly). Old hands may feel no need for ramps and pins in their favoured setup (without understanding why necessarily) but in many OEM triple setups no ramps and pins on standard sized chainrings will almost certainly drive you crazy.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

bgnukem
Posts: 210
Joined: 20 Dec 2010, 5:21pm

Re: Narrow q factor triple chainset with steel rings

Postby bgnukem » 1 Aug 2019, 4:02pm

Just to complicate things, I experienced terrible shifting problems with my front mech (Deore XT M750 - 9 speed) when I replaced the original Deore chainset with one of the Spa Cycles triples a few years ago.

It really wouldn't work with the 10-tooth difference between the top and middle 'rings but replacing the middle with a 2T smaller ring solved the issue. It seems some front mechs may be designed to work with a larger 'drop' from large to middle 'ring, in this case 12T not 10T!

Certainly some triple mechs I have, have a much deeper cage than others which seems to be consistent with a larger drop.

fatboy
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Location: North Hertfordshire

Re: Narrow q factor triple chainset with steel rings

Postby fatboy » 1 Aug 2019, 4:36pm

Very interested in the description of pins and ramps by Brucey and I'm intrigued and it makes me wonder if a Steel Surly middle ring might work if I use 24, 38, 48 (currently running 24, 36, 48). The shift from small to middle might be sluggish but generally when I do that shift I'm not using much pressure. My shifter setup is Sora throughout and the rear cassette is 11 to 32.

What do you think?
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly

reohn2
Posts: 36745
Joined: 26 Jun 2009, 8:21pm

Re: Narrow q factor triple chainset with steel rings

Postby reohn2 » 1 Aug 2019, 6:51pm

fatboy wrote:Very interested in the description of pins and ramps by Brucey and I'm intrigued and it makes me wonder if a Steel Surly middle ring might work if I use 24, 38, 48 (currently running 24, 36, 48). The shift from small to middle might be sluggish but generally when I do that shift I'm not using much pressure. My shifter setup is Sora throughout and the rear cassette is 11 to 32.

What do you think?

If you're using STI's no problem as the over shift with road STi's will easily accommodate the lack of ramps and pins.
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peterh11
Posts: 214
Joined: 20 Mar 2010, 10:25pm

Re: Narrow q factor triple chainset with steel rings

Postby peterh11 » 4 Aug 2019, 12:28pm

bgnukem wrote:Just to complicate things, I experienced terrible shifting problems with my front mech (Deore XT M750 - 9 speed) when I replaced the original Deore chainset with one of the Spa Cycles triples a few years ago.

It really wouldn't work with the 10-tooth difference between the top and middle 'rings but replacing the middle with a 2T smaller ring solved the issue. It seems some front mechs may be designed to work with a larger 'drop' from large to middle 'ring, in this case 12T not 10T!

Certainly some triple mechs I have, have a much deeper cage than others which seems to be consistent with a larger drop.


To add a data point: I have a Tiagra 10 speed (current model I think) triple front with a Spa chainset (TA rings as sold by Spa) on an old touring bike. This changes really smoothly and easily across 26/36/46 and 24/34/46, using a 9 speed chain on an 8-speed cassette. I did need to set the height very carefully. To be fair this is with a friction lever mounted on Kelly Take-Offs, but I feel no need to overshift or anything, it just goes. Some trimming needed in inner and outer ring but not a lot.

It does have a deep cage and I suspect would handle say 24/36/48 too.

(Data point on life of the rings: I replaced the 26/36 with 24/34 to change the gearing. The 36 middle was quite worn after 8000 miles. Still usable but getting near the end of its life. Others were fine as I do probably 80-90% of my riding in the middle one.)

I have a newer bike with full Tiagra triple 4703 gearing including STI levers, so same front mech. This all works excellently as well, once I had practised a bit with the upshift, and the trimming feature on these levers is very good (once you have figured it out - poorly documented). This thread supports the hope that when I need to replace the chainrings, I could fit a Spa chainset with smaller rings for venturing out of the East Anglia flatlands :-). Thanks!

PeterH