Yet Another Cycling Forum
General Category => The Knowledge => Topic started by: zigzag on 24 August, 2014, 06:16:16 pm
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currently i'm running a 45/30 chainset at the front and have been very happy how it works for the type of riding i do (long distance, tempo, hilly and flat). i would like to continue running this setup as i spend almost all the time in the 45t ring, only shifting to 30t on steep hills and mountains. i used to have 42t as an outer ring and that was ok as well, but prefer 45.
now, if i wanted to enter a time trial i would need want a bigger ring in the front for downhills as i currently spin out at about 55kph.
the solution i am coming to is to run a triple (the shame, the shame.. :-[). in an ideal world i'd just get a proper tt bike with big 'rings, fast wheels and electronic gears. however as i want to keep my current bike and make it suitable for hills and tt's i wonder if there is a shimano front derailleur that could shift 53/45/30 chainset smoothly? has anyone run a similar setup? number of speeds not that important, 8,9 or 10. ta!
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It will be finding a suitable front mech that's the problem.
To shift inner to middle wants a mech with a fairly deep inner cage plate, but with only 8T difference between middle and outer you will quite likely to find that the inner plate fouls the middle chainring when trying to shift middle to outer. Raising the mech up the seat tube may result in the change out of inner going straight to outer.
Most current mechs are quite heavily optimised to work as well as possible with standard chainring combinations, with the result that they don't work well with oddball setups. I'd look for an old front mech from before the inner sideplate became so sculpted. I'm using Suntour XC Pro.
This does of course require that you have non-indexed front shifting (bar end or Ergo rather than STI).
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Friction or indexed, Shimano, Campag, SRAM, etc.?
I recall Shimano have had 30/42/52 chainsets so a mech for one of these might be suitable.
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Up til now, I have always preferred a triple (12-27, 52/39/30) (31-121 inches) to get my bulk up and down the Peak District pimples.
However, I recent took delivery of a new bespoke bicycle and was persuaded to buy a compact double 11 speed shimano ultegra.
This gives 11-32, 50/34. (30-127 inches)
Having used this I can honestly say that I do not miss the triple - with the 11 speed, there are very few "extra" steps available on the triple.
On the matter of the triple, the front derailleur is sometimes a little trickier to set up properly but, provided you have the correct bottom bracket and mech it does work OK. I have found that the better the quality, the better the shift. I have always used Ultegra level stuff - 9 speed and more recently 10 speed. These work and shift fine. I don't think the Ultegra triple is manufactured any more. Shimano still does a 10 speed triple in the 105 range but the front ring has 50 teeth (50/39/30) giving a maximum of 116 inches. (Ribble still has stock) Tiagra is also available in a triple. I have also seen individual spares of older models advertised so you should be able to get individual components if you want. Be sure to get a proper front mech for the desired chain width (10sp & 9sp seem to be slightly different - at least the ones I have slightly different cage widths)
The way I set up a triple is to loosen the cable with the chain on the inner ring, set the limit screw so that the cage just does not rub when in the rear biggest ring. tighten and secure the cable so that all the slack is taken on. Change to the big ring on the front and the smallest rear ring and adjust the limit screw so that the chain just does not rub. Seems to work for me....
Good luck!
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I've linked to it before but take a look at Wilko's bike (http://www.cyclingweekly.co.uk/news/latest-news/andy-wilkinsons-dolan-time-trial-bike-29431).
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If you want to use a fairly modern derailleur, you'll have to use a double mech without much contouring in the cage.
If you use an older front mech (which would be better), choose one without a deep inner plate. Many years ago, Shimano used to produce some triple front mechs in 2 styles per model, crossover and half-step. You want a front mech suitable for half-step chainrings.
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thanks for the replies. that chainset on Wilko's bike - i wonder if the granny ring is usable or just acts as a chain catcher.
i did some research and came to a conclusion that the jump between the granny and middle rings is not too important and front mechs shift up and down happily with many different combinations. where it matters is the difference between the middle and outer rings. there are two types of triple mechs - optimised for 10t difference (50/39/30, 52/42/30) or 13t difference (52/39/30). so in theory outer/middle combinations like 55/45, 54/44, 53/43, 55/42 should work no problem with widely available front mechs? my main requirement from this setup is to have a 42...45t middle ring (the common 39t middle 'ring is too small).
regarding 11sp compact chainset - it would probably work for me and i much prefer double vs triple, however the 50t ring is neither here nor there (too big for rolling terrain, too small for downhills in aero bars).
the chainset i would go for is likely to be 105 5703, as it is the only current decent chainset in shimano range that looks right with flat chainrings.
LWaB - how old those older front mechs you are referring to?
thanks!
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I currently run a 48/38/28 ATB chainset on my Planet X and change gear with a 105 front mech with friction levers. 8 speed. Cassette is 11-30.
No problem at all.
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Zigzag - if I understand your objective correctly, I think you may have almost answered your own question. As others have said, the key with modern derailleurs (Shimano in particular) which are sculpted to work with specific ring sizes which have pick up pins and ramps is to comply with the size parameters set out by the manufacturer. The answer then, is to cast about until you find a front mech with a specification that comes closest to your target.
My limited researches in Shimano’s documents reveals that the middle-outer minimum differentials and maximum inner-outer ranges are:
FD-4403 10t 22t
FD-4503 11t 20t
105 FD-5703 11t 20t
Ultegra FD-6703 13t 22t
If you follow this slavishly, you then have to chose from 10, 11 or 13t minimum steps between the middle and outer and then set the inner ring size to within the overall capacity. In practice, if you are prepared to settle for a less than fully usable set of ratios, the inner can usually be pushed smaller and you can just avoid small with small (when the chain will either catch on the inside of the middle ring and/or drag on the back of the cage).
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I use an 8sp or 9sp Shimano double mech to shift a 52/42/32 triple without problems. I think it could cope with a less than 10t gap between the bigger rings.
Shimano's half-step front mechs stopped being made last century when interest in making equipment for touring bikes died, before the current trend to disguise touring bikes as cyclocross or trekking bikes.
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Wonder if an MTB front mech would function well ? Often MTB triples 22/32/44 or thereabouts so big jumps and easily handled by the mechs
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Aye, but this is about a small jump, below the minimum published spec for the mech ... There'd also be the issue of the mech being designed to curve round a much smaller ring.
If you can't find a half-step triple changer, is it worth trying with a double mech? There's a good chance it'll cover the range (certainly I've got an old Mirage double mech shifting a triple fine, albeit 30-40-50), and the lack of sculpting might mean it copes better with the small middle-big jump.
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another query - would an inner chainring (i.e. withouth ramps and pins) work ok as a middle on a triple? i know older chainrings did not have any pins/ramps and cyclists used to use them in the past. i can't seem to find a triple-specific middle ring bigger than 42t.
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Depends whether you are using STI or not. STI without pins rarely works particularly well. Ergos or bar end levers are usually fine.
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I'm successfully shifting a 24-36-50 with a 105 mech (11-34 on the back), but that's with a friction bar-end shifter, which gives you a lot more wiggle-room than an indexed shifter will give you. Positioning of the front mech does have to be spot-on, too.
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i'd be using standard sti brifters. so it seems my choice is limited to 42t middle ring. unless there is an outfit that can modify chainrings by adding pins and milling ramps in the right places?
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Wonder if an MTB front mech would function well ? Often MTB triples 22/32/44 or thereabouts so big jumps and easily handled by the mechs
I'm running a 22/44 front double constructed from a MTB triple as you suggest. Works very well.
(http://i1085.photobucket.com/albums/j433/Lighthorse2/20130908_150249_zpsd80721d1.jpg) (http://s1085.photobucket.com/user/Lighthorse2/media/20130908_150249_zpsd80721d1.jpg.html)
The front mech is a road triple Sora. Which was O/E for the 30/42/52 Sora chainset.
Riding up a hill on a 22" gear is more comfortable on the ankles than pushing a bike walking.
Note the 'Dog fang' device just above the inner ring.
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i'd be using standard sti brifters. so it seems my choice is limited to 42t middle ring. unless there is an outfit that can modify chainrings by adding pins and milling ramps in the right places?
Could you use an outer ring (eg Stronglight 46T) in the middle position? Would have the ramps and pins you need for better shifting.
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The other option is modification. I ground the inner cage plate of a modern Shimano triple mech to clear the middle ring that was bigger than specified. That worked quite well.
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i'd be using standard sti brifters. so it seems my choice is limited to 42t middle ring. unless there is an outfit that can modify chainrings by adding pins and milling ramps in the right places?
Could you use an outer ring (eg Stronglight 46T) in the middle position? Would have the ramps and pins you need for better shifting.
i thought about this; the only thing i'm not too sure about is if the chainring bolts would be sticking out too much to the inside as the bolt "bed" would be milled on the wrong side (facing spider arm). chainring bolts then would catch the chain when in granny ring and middle of cassette.
The other option is modification. I ground the inner cage plate of a modern Shimano triple mech to clear the middle ring that was bigger than specified. That worked quite well.
i have a dremel tool and wouldn't mind doing some grinding :). but i'd like to explore widely available options first.
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Zigzag - just going back to where we came in, your OP ....... I know you to be a pretty strong, fast rider, so I was surprised that you say you’ve been running on a 45-30 double - by my reckoning, on 25mm rubber, that’s about 108” on an 11t top sprocket. I’d call that on the low side for a rider such as yourself, unless you have very much a “spinner not a masher” style.
If you are indeed a spinner then would you not manage fine with a standard triple set up? A 52-39-30 on an 11 up cluster would give a top gear of 125” - switch to a 53 big ring and you’d have 127”
Are you fixated on using the middle ring more than most and if so, what’s the rationale?
Just asking ....
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i normally keep the cadence of around 80, and my current 45x11 top gear is high enough for all the riding i did so far (non-competitive, audax, hills and mountains). standard triple with 39 middle ring will require more front shifting (which i want to avoid) than the one with 42..45 ring. currently if i go downhill faster than 55-60kph i just tuck in and coast.
the reason for using 45 middle ring is it's the right size for flat and gently undulating terrain and i spend 95% of time in it, that's why i'm fixated on getting it right :). 52 ring is too big for that type of terrain (especially if there is headwind) and 39 too small. generally i'm very flexible regarding the cadence (ridden many audaxes including lel, pbp, mille miglia on a single chainring), but want to try a triple set up with my favourite 45-30 plus a big ring for tailwinds/aerobars/downhills. after searching the internet yesterday it looks like i'll have to settle for 42t middle ring.
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Fair enough, I guess it’s a case of “each to his own”. I was just puzzled. Running 45/11 at 108” isn’t that far away from 52/13 (106” or if you insist, 53/13 which is 108”) Personally I’ve always found the larger the ring and sprocket, the smoother the drive feels, provided you don’t get the chain too crossed up, and 52/13 would be no worse a chain angle than middle/11t.
It sounds to me that you’re going to a lot of effort to avoid using the parts you intend adding to the bike! ;D
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Fair enough, I guess it’s a case of “each to his own”. I was just puzzled. Running 45/11 at 108” isn’t that far away from 52/13 (106” or if you insist, 53/13 which is 108”) Personally I’ve always found the larger the ring and sprocket, the smoother the drive feels, provided you don’t get the chain too crossed up, and 52/13 would be no worse a chain angle than middle/11t.
It sounds to me that you’re going to a lot of effort to avoid using the parts you intend adding to the bike! ;D
i think we look from different perspectives - i'm more interested about the most usable gears, while you pay more attention to the tall end of the range :). with the current 45 ring my cruising gear is 45x15..13, perfect chainline and smooth drivetrain and that's where i spend most of my time riding. the big ring would come handy for tt's and that's the only reason i'm contemplating a triple chainset, as i don't know any other way to have a very wide range. maybe i'll just get a proper tt bike in a future, but first, i'd like to have a go at my first tt! :thumbsup:
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I think your idea is basically good, but a little too extreme because it misses a couple of points.
A 45x13 may well be smooth for you, but more teeth can be smoother still! Anyway, 45x13 on a triple will be rougher than 45x13 on a double due to the different chainlines (assuming you won't have a bottom bracket long enough to be suboptimal for the big ring). It's a very small difference in terms of mm, but can be enough influence gear selection. For example, middle ring + the smallest couple of rear sprockets on my bikes is useable, but doesn't feel as good as slightly larger sprockets + big ring.
Also, a smaller than 45T can be handy for moderate hill climbing - which you might value despite it being for only a small minority of the time.
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Wow, everyone has an opinion on gearing ;)
I've linked to it before but take a look at Wilko's bike (http://www.cyclingweekly.co.uk/news/latest-news/andy-wilkinsons-dolan-time-trial-bike-29431).
But if you look closely you'll see that the inner ring is unusable - the bottom of the dérailleur cage would foul the chain in the smallest chainring, with most of the rear sprockets.
Its the third most talked about subject in cycling.
Second is "Which is the worst hill?" and first is 'Jam or cream first on a scone?"
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...But if you look closely you'll see that the inner ring is unusable - the bottom of the dérailleur cage would foul the chain in the smallest chainring, with most of the rear sprockets.
As yes but ... allow for the fact that in the photo the cage is in the big ring position - over the inner ring, it would drop a bit. Then factor that he uses this machine with different wheelsets and I imagine with different rear clusters (still larger sprockets) and if low gears are wanted (touring for example) it needs only to work with say the two largest sprockets on the inner ring and it's viable, non? Hence also, the custom extra long rear mech cage, so it doesn't self destruct if he accidentally goes 'big-big'!
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zigzag:
To get back to your question about "spinning out" at speed. 2p worth.
I think the way to work it out is to consider how fast you actually want to go at your preferred maximum cadence.
For example, I am most comfortable at 90-100rpm but I can spin 120rpm downhill without too much trouble - faster is difficult with heavy legs!
Uphill, I can usually do about 15kph at 4% - 34 inches at 100rpm - or 11kph at 6% - 29 inches at 85 rpm. (~230W - I am not a racer!).
Level about 32kph - 78 inches at 100rpm (also ~230W)
Downhill depends on how steep and how fast I want to go. 120 inches at 120 rpm gives almost 70kph (180W and -8%) - plenty fast enough.
Hence my choice of a set of ratios from ~29 to ~120 inches.
With a triple in this range (53/39/30,12-27) the steps are approximately: 117,108,100,94,87,83,79,73,67,64,60,54,49,42,37,33,29 inches. 17 effective steps on 3 chainrings.
With an 11 speed compact double in this range (50/34,11-32) the steps are approximately: 120,110,101,94,88,81,78,75,69,64,60,53,47,42,38,33,28 inches. Also 17 effective steps on 2 chainrings. So far, it seems that the double shifts better and getting the right ratio is easier than on the triple.
With such a similar set of rations, the compact double seems, to my mind, the better choice.
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At the other end of the spectrum, I’m most comfortable at about 65 rpm.
This equates to 18.5 mph in 99 inches ( Top at 195 W ); 16 mph in 85 inches ( cruising at 130 W ); 8 mph in 42 inches up a 10%; 5 mph in 24 inches up a 15% ( 320 W ) and 4 mph in 22 inches up steeper.
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went for the standard set of rings 52-42-30, as larger than 42t middle rings aren't available. i'll see how i get on :)
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a quick update. i've converted my bike to triple, keeping the same 7 speed setup*. chainset is 10sp 105 with 52/42/30 rings, rear mech 10sp 105 medium cage, front mech 9sp 105, chain 8sp. shifts very well, only there's a slight chain rub at the extreme combinations (which signals the need to change a gear).
this triple setup is around 160g heavier and more embarrassing, but will provide a wide range so i can both ride steep hills and do tt's (quite looking forward to the first one!). you lose some, you win some!
* to downgrade to 10 speed, i'll just need to change the levers, chain and cassette which are waiting in a spares box