front mechs, advice please

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Gari
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front mechs, advice please

Post by Gari » Thu Jun 11, 2015 12:12 pm

I am looking to get a front mech for the WTF. Smallish rings; 24/6+34/6 double, 30-11 cassette. I am using 105 triple front shifter. 105 med rear mech to be used.
I haven't used a front mech so long I can't recall, I assume that the throw for road shifters and mtb shifters differ somewhat, but I also assume that it is possible to get something to work, given the growth in "adventure" bikes on the market with touring gearing and drop bar shifters. So collective, what should I buy?

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StuartG
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Re: front mechs, advice please

Post by StuartG » Thu Jun 11, 2015 12:44 pm

For shimano, road shifters will work with a road FD and a MTB/Road RD. If you are on drops, then you could try bar ends and they will work with anything.

I am not sure about MTB shifters or SRAM as I only use drops.

jameso
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Re: front mechs, advice please

Post by jameso » Thu Jun 11, 2015 5:50 pm

I think it'll be a minor bodge Gari but road STIs and MTB mechs can work, the throw is different though. I'd try to match the FD cage size to the rings first to get the plate ramps in roughly the right place, so one of these http://www.shimano.com/publish/content/ ... ntain.html for ex, 9spd for a double. Or the 10s version. It may not line up quite right per STI click but it will shift better ime than a road FD on smaller rings. For a double its a lot easier to get working than a triple anyway. One issue used to be getting triple STIs (and road FDs, edit/added for clarity) to work MTB triple set ups with hollowtech 2 cranks as the FD wouldn't go far enough over for 50mm chainlines, but doubles or square-tapers with 45-48mm chainlines are usually OK - been a while since I did that though. Even just taking one BB spacer out and fitting a 1mm instead can help, or tolerating chain rub in some gears (unf usually the lowest if you need the STI-limited mech throw of the MTB FD to shift onto an MTB triple outer ring -edit for clarity). I really like bar-end shifter set ups with wider-ratio rear blocks and doubles, especially on more relaxed riding position bikes. It gets rid of all the FD faff.
I also assume that it is possible to get something to work, given the growth in "adventure" bikes on the market with touring gearing and drop bar shifters.
I wish it were easier .. SRAM have sort of got it right with wide-ratio single ring set ups like CX11 but I've gone back to either bar-end shifters for full gearing/mech choices, or 10s STIs using slightly smaller chainrings 32 or 34 and 46 or 48, std road FDs, 9s Shadow mechs (got a pile spare!) and 11-36 rears. Too much emphasis on perfect shift actions and constant cadences for ideal-conditions, predicted-use bikes I think, but that's what they do well. Middleburn's Incy chainsets are worth a look - narrower chainlines are possible with the square taper versions and there's loads of ratio options, at a price.
Last edited by jameso on Fri Jun 12, 2015 6:46 am, edited 1 time in total.

Gari
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Re: front mechs, advice please

Post by Gari » Thu Jun 11, 2015 9:24 pm

Cheers James, exactly the kind of info I was after. I am actually running a Spa XD2 at present on my Tricross, with 105 10spd STIs, which is roughly the drive train that will go on the WTF. Works well at the back, but won't work on the FD that came with the bike at all, which is what led me to ask this question. I will probably run either a MrWhirly with the inner and middle, or this spa on the same basis with 24/32. My understanding was that 10spd STI would work with 9spd mtb mechs(r) as long as they were non shadow, if this is not the case then I could run bigger rings at the front with a larger cassette, as I have some shadow mechs around here too. Enough to give an aspirin a headache all this "compatibility" stuff!!
To recap then: A Bigger rings out front, 32/44 outer-middle say, and run a road mech. B Smaller rings, inner-middle, run an mtb mech and fiddle 'til it works..... I don't like bar end shifters so that's out. I thought about the Gevenalle CX shifters but couldn't find a uk/eu dealer, shame as they have a friction shifter for the FD.

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Re: front mechs, advice please

Post by jameso » Fri Jun 12, 2015 6:44 am

10s STIs with 9s FDs, I've not tried that combo. The 9s rears work ok, shadow or std. Same pull.

It is a headache and I hope i've not got something wrong in all this ... Like MTB shadow mechs having no cable adjuster, that stumped a build a while ago. I'd try the MTB mech / STI combo with an old mech if you have one before spending on the 'right' one as it'll probably mean cable fixing / leverage faff. There's also the Shimano CX FDs, CX70, forgot about those. That may be a better cage size for the 28-40 sort of MTB double?

Just found this while looking for something more concrete re front shift ratios -

http://en.wikibooks.org/wiki/Bicycles/M ... Dimensions
.. an MTB pulls 9.75mm of cable for a front shift whereas a road shifter pulls only 6.75mm; some 3mm less than the MTB.
That's the difference that makes setting up a road STI + MTB FD a faff for triples but more possible for doubles with some adjustments, ie cable fitting spacing to create a bit longer lever arm on the FD, tolerance of some increased rub in certain gears to enable a fairly reliable shift, etc.

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Re: front mechs, advice please

Post by u02sgb » Fri Jun 12, 2015 8:38 am

I've no experience with road stuff but to throw something in from left field - I've used front grip shift with good results mixing triple, double and 8,9,10 speed front mtb.

The grip shift has small steps so lets you trim and might fit on the drops. Also, cheap off eBay, little to go wrong with them and quite lightweight. I'm using 9 speed Sram x0 which were less than 20 quid.

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Zippy
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Re: front mechs, advice please

Post by Zippy » Fri Jun 12, 2015 8:43 am

jameso wrote: Just found this while looking for something more concrete re front shift ratios -

http://en.wikibooks.org/wiki/Bicycles/M ... Dimensions
Thanks for the Jameso - I'm sure I came across something similar but this looks better than the info I found a while back, cheers :-bd

FWIW, on top of the info already mentioned on this thread, I reckon if you're running a double, the front mech should be in either "top" or "bottom" locations, and you just have to make the shifter pull that.
I almost made a MTB FD shifter work with a road FD on a flat bar road bike build, it almost worked - I just couldn't do the "trimming". So what level of bodgery required will depend on your trimming requirements I reckon.

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