Compact cranks 50/34 question

I have a set Shimano Hollowtech II cranks [FC-R700] with the standard 50/34 chainrings.....but they won't give me quite the gears i would like.....How would 49/36 work.....i use downtube shifters with a 9 speed cassette....in index mode.....The front mechs is a Shimano Ultegra and the rear mech is Shimano 105 both 9 speed versions.......If i change what would be better TA or Stronglight Zircal rings...or are jusr as good?.....Any advice would be appreciated.

Should work alright. I've got a Tiagra standard that I changed to 47/39 (9spd setup), and a 105 compact that I changed to 50/38 (10spd setup). The 47t is a Gebhardt, and the 38t is some kind of generic/no-brand thing I can't remember.

Both work fine, though due to the stock 34t on the compact being dished towards the big ring, and replacing it with a non-dished item, I did have to angle in the rear of my front mech cage a little to retain crisp shifting and stop the occasional incidence of the narrow 10spd chain skating between rings on downshifts.

If going from 50 to 49, you might not even need to move the front mech down.

you can get 36/52 which is a good ratio

Other then the obvious change in gearing and as long as you lower your mech slightly to maintain the required gap with the smaller chainring everything will be fine. You may even notice a slightly quicker front change with 49 / 36. A standard road front mech capacity is generally quoted as 16T, but the less teeth difference the less the chain has to 'climb' the ring to make the change. I use 48 / 36 on one bike and 48 / 38 on another bike. Shimano cross crank set ups are standard 46 / 36 ..

As for the rings .. Take your pick. The Stronglight ones are made by TA. Personally I prefer TA or Stronglight CT2. For Stronglight CT2 try http://www.xxcycle.com/

you can get 36/52 which is a good ratio

I was riding 50/34 this summer but found I never used the 34, have now swapped to 52/36 which seems more useful, I would make sure you have a 11t at the back though.

I use a 48 on my hack bike as there's never time to get up to any speed between lights in London but I wouldn't recommend it for open roads, IMO.

As for aftermarket chainrings I always use TA and recommend them.

I am going to use 46/34 and give that a go....the 46 is a Shimano CX ring and the 34 is already shimano.

Adam T.....why won't you use it on the road.......87'' is more than enough for me......so my smallest sprocket will be 14T

I am going to use 46/34 and give that a go....the 46 is a Shimano CX ring and the 34 is already shimano.

Adam T.....why won't you use it on the road.......87'' is more than enough for me......so my smallest sprocket will be 14T

Just personal preference I guess, I've used a 53t big ring for years with either 12-23 or 12-25 so even trying a 50t ring felt a bit strange, hence the swap to 52t. I found myself in the 50t all the time searching for the right sprocket at the back on hills. I've never really thought about gear inches I just know what feels right for the riding I do.

53/39 + 12-25 just feels like a great all round combination, I decided to try 50/34 + 11-25 this summer as I went to a part of wales with a lot of climbs but I didn't really get the hang of it.

If you change your mind and go for a 48t I've got a nice surly chainring I'd sell if it's any use.

If you can push the big 53 / 52 gears then I've got no quibble. But for me 48 is plenty big enough on the open road and also means I'm generally in the middle of the cassette giving a nice chain line .. 48 - 12 at 90rpm is about 28mph ..

I think different bikes suit different ratios also- and maybe different times of year as well.

I've been perfectly happy with 46/36 and 11-32 recently.

I ran out of gear very early for sure, but given the state of the roads I didn't really want to go any faster- and 46/11 can still punt you along at a decent clip.

The nice thing as Oswald says is that you can use more of the block.

On my (much) lighter/faster bike I've had 53/39 with an 11-25, and tend to stay toward the larger sprockets most of the time (in the big ring).

This summer I'm going to try 52/36, not that I climbed anything last year that required such a low gear- but this year I want to climb some real mountains, 22%+, so being able to chuck a 12-27 on the back with the 36 up front has significant appeal.

I would happily change my 'fast' bike back to a proper 53/39 (i have the rings and spider to do so) but I do take my bike to Wales on a regular basis and the steep, long climbs there force me into 34/23 on a regular basis so basically I can't be fucked. Screw long cage mechs and 27 sprockets.
I'm not racing and I have nothing to prove :) even when riding with stronger riders I hardly ever find myself spinning out.

May get myself a 110bcd 52 if I decide to ride some tt's on the s-works though. Maybe.

^^how can you 'run out of gear very early' with a 46/11? That's 110", so even at a modestly cruisey 100rpm it's nearly 33mph. I only ever use my 50/12 (roughly the same) if I want to continue pedalling over 40mph for any great length of time.

How many people here never learnt to pedal properly on restricted gears as youngsters, FFS.

Exactly, any moderately large hill and you are into frantic spinning territory if you want to go faster.

40mph is ~125rpm - that's frantic for a snail or sloth maybe.

It would take a brief burst to reaccelerate, and then you may as well concentrate on getting a good aero tuck to maintain speed. I've 'sat' on the top tube and coasted past people who bemoan their lack of an 11t despite weighing less than them. I've also *gracefully *pedalled past them on medium gear fixed, but that's another story.

Due to my colossal, chair shatteringly enormous thighs my maximum cadence is 40 rpm.

My maximum cadence is my age - in dog years.

125rpm is bouncy for me. Getting better though

Maximum speed from yesterday was 38.96 mph, maximimum cadence was 120.

These thrilling numbers brought to you by the colour yellow.

There's a difference between the 'bouncy' cadences at your slow-twitch ceiling on the flat, and the kind of fast-twitch stuff that kicks in on fixed descents.

My max speed was just over 35mph, so my max cadence was around 170rpm, with Sade-like levels of smooth operation (not Marquis De).

My "natural" cadence range is ~70 to ~120 I think, I tend to average in the high eighties to low nineties on the flat, when fresh.

I noticed in the run up to Christmas that as fatigue increased I was unconsciously choosing a higher gear and pushing it at a lower cadence.

I have gone for a 46/34 combination but the front mech is meant to be used with a 50T ring.....The rings are both Shimano , the rear mech is a 9 speed 105 and the shifters are downtube Shimano DA SL-7700. Any suggestions as to which front mech i could get?....My choice would be the Shimano CX70 mech but the blurb says best with STI shifters....Would this 10 speedfront mech work with 9 speed DT shifters.....if not any suggestions for a suitable front mech....does even need to be Shimano?

I'm using a front mech that was originally paired with a 53t. It works fine with a 47t. Have you tried using what you've got?

What BMMF said .. You really don't need anything special. i'm using a Red on one bike and Dura Ace on another bike both with 48. If you haven't already tried it .. do so! I'm assuming you'll have moved the mech lower on the seat tube so that the cage is spaced the correct distance from the outer ring and adjusted your cabling to suit.

As for the CX 70 mech .. It will work with your down tube shifters as your front shift, if I remember correctly from running them shifters myself in the past, will be a friction shift? Just make sure if you go that route you get the correct pull for your bike.

BMMF/Oswald....Many thanks for your input.

Firstly BMMF....yes i have used what i have and it works but not very smoothly to be honest.....the mech is about 5-6mm above the outer chainring.....hardly ideal.

Oswald...the mech is at its lowest point on the front mech boss on the seat tube. Regarding the CX70 and the downtube shifters.....yes the left hand [front] shifter is friction....the pull on mine would be down pull.

Life would be easier if i needed a band on front mech as that be lowered to suit!

5-6mm is way to high .. I guess I don't need to tell you but it should be about 1-2mm. The CX70 isn't going to sort that issue for you I'm afraid because it will mount roughly in the same place. You need to get the mech lower .. or go up slightly on your tooth count.

Another couple of ideas ..

1 - take a round file to the bottom of the braze on and remove a small amount of metal .. go slow and trial fit mech between files. I don't think this will get you 3mm!
2 - file some material off the mech mount bolt only where it goes through the braze on of the frame so it can sit lower. You'll have to measure carefully the position and reduce the dia all around so as it tightens it doesn't move back up. Again I don't think it will get you 3mm but a combination of the two may be enough?
3 - not sure if this will work .. but Sram have two mounting points in the front mech so the 'upper' point may allow the mech to drop low enough. If you can find a lender mech before you buy it would be best

Or, the nuclear option:

1. Grind the front mech post off the frame, and use a band-on front mech/adapter.