Changing inner ring on triple 30T to 26T

[reohn2]

I never feel the need or want to pedal at anything over 30mph.

thecycleclinic
50x11,20mph + average,several miles I'd have let them go or I might have needed a cyclistclinic myself

[Ayesha]

Some books describe the cyclist's power curve to be much like a steam locomotive. Virtually constant power up the rev range until it spins-out due to gas transfer speeds.
Others reckon the cyclist has a 'sweet spot' cadence.

I follow the latter. For me, 90 rpm is 'sweeter' than 80 or 100.

Gearing for a TT is 53 x 15. 90 rpm at around 25 mph. It goes up and down a bit with gradients.

Gearing for an Audax is 36 x 17, 90 rpm at 15 mph. That leaves the 15, 14, 13 and 12 sprocket for when I want to get a move on. 90 rpm in top is 21 mph, which is 300 Watts. Not the kind of 'all day' power output I'm capable of.
Sometimes I amble along on 36 x 15 at 80 rpm. 15 mph with a tailwind.

A cyclist has a 'sweet spot' cadence. He/she also has a Functional Threshold Power ( max output for 60 minutes ). 55% of FTP is known as "taking the bike for a walk" because this is an 'all day' exertion. When you find your 'sweet spot' cadence, chose a gear that rolls you along at a speed appropriate to 55% of your FTP ( according to the touring bike W vs mph calculator ) spinning the cranks just below your 'sweet spot'.
You will be surprised to see the high gears you don't need to ride a bike all day

[BigG]

I use the 50/11 sometimes on the flat. Came in useful on a club ride when I had to stop but the others did not hear and carried on at a 20+ mph average. I had to use that gear over several miles to catch them all up. That was hard work. So most of the time it is useless but sometimes it is handy but I do ride in the flatlands alot.

I believe that Mark Cavendish can push a 53/11 on the flat for at least 200 metres! I am not as fast as him and find 48/14 quite high enough.

[ossie]

OP here :

It seems its not an issue to drop it in, however with my set up it equates to 21.7 gear inches. I did this beast last year amongst others fully loaded http://www.bikeroutetoaster.com/Course. ... rse=263671 (see summary top left) with the 30t granny ring and ended up walking on a couple of occasions near the summit. If I am being honest the Pyrenees and my knees had a bit of a fall out.

I am doing the same again as its my preferred route from Spain to France and then cycling over to Ventoux. I am wondering if its worth going lower than 26t...I guess I would then struggle with my current chainset but changing that would mean expense that I cant really justify at the moment.

[Malaconotus]

I am doing the same again as its my preferred route from Spain to France and then cycling over to Ventoux. I am wondering if its worth going lower than 26t...I guess I would then struggle with my current chainset but changing that would mean expense that I cant really justify at the moment.

You can fit a 24T to your current 74BCD inner. Question is whether it will be too industrial a shift, whether it will be more prone to dropping the chain, and whether you will get chain rub on the front mech in too many of the gears. Essentially the three issues I listed earlier may be exacerbated. I went with 26T because I already have a 32 on the back and this is a bike normally loaded only with my own considerable bulk plus a saddlebag, and 22 inches should be low enough a gear to winch up anything without a touring load. If I were crossing the Pyrenees loaded, I'd want 24:32 or 24:34, and beggar the troublesome shift and cadence issues.

You can buy both a 24 and a 26 from Spa for £14 total... http://www.spacycles.co.uk/products.php ... b0s149p244 Why not try them both out?

[reohn2]

FWIW,I've run a 24 inner ring with a 39 middle and 48 outer on one of the tandems with 9sp STI's without issue.
I do use an N-gear jumpstop to stop any chance of unshipping the chain when changing down to the inner ring.

[Valbrona]

I never feel the need or want to pedal at anything over 30mph.

Same here. My top gear on my road bike is 42x11. Pedal over 30mph for an hour and you can set a new world hour record.

[Edwards]

CJ has a system for measuring the min small chain ring. If I remember correctly it is something like this this.

Engage the lowest gears on both front and rear.
Then measure the gap between the chain and the bottom of the front mech.
Allow 2mm for every one tooth reduction in the size of the chain ring.

I think that you would find the drop from 30 to 26 on the front to much. This is because when you do drop down to the small ring the gap will be such that you would lose that much forward momentum it will feel like you have stopped. Also when changing up you will be spinning out and then your legs will feel like they have almost stopped when the 48 engages.
I use a 28 38 52 on a Sora and this can feel bad enough.
On another bike I have an Alivio that the small ring is 26 replacing the 28 this also seems a big jump at times.

The cheapest thing to do is replace the whole front to keep all the gear ratios closer together.

I also have an 11 on the back, the reason is because of the cost as these do come out the cheapest. I do use the highest gears going down hill for fun. It enables me to not work to hard and just push gently on the pedals whilst not having to spin fast.
Great fun when playing on the lanes of North Wales.

[ANTONISH]

My touring bike has 46-34-24 with13-32 (this will be changed to 34 shortly). My audax bike has 48-36-26 with 13-32.
I tried fitting a 46-36-26 to the audax bike but the braze on front road mech didn't work well with it. My touring bike has a mountain bike front mech which works with the smaller rings very well. I find when touring that 46 x 13 is perfectly adequate and the same is the case of 48 x 13 for audax (that's almost the same as the 52 x 14 most of us including professionals had for racing fifty years ago). We have already covered in another thread that when descending at speed trying to gain an extra 2 or 3 mph by pedalling requires a very large power output and isn't particularly useful (given that some spinning is a good idea to improve the blood flow in the legs during a long descent).

[reohn2]

......I think that you would find the drop from 30 to 26 on the front to much. This is because when you do drop down to the small ring the gap will be such that you would lose that much forward momentum it will feel like you have stopped. Also when changing up you will be spinning out and then your legs will feel like they have almost stopped when the 48 engages.
I use a 28 38 52 on a Sora and this can feel bad enough.
On another bike I have an Alivio that the small ring is 26 replacing the 28 this also seems a big jump at times..........

I don't understand .
At the bottom of a climb,solo or on the tandem,I change down to the inner ring whilst changing up (smaller cogs) symultaneously to maintain a similar cadence, then work my way down the cassette(bigger cogs) as needed,when the hill levels out I do the same in reverse.
No big jumps so no knee shocks
It's one of the beauties of STI's,any change to any ratio without moving the hands from the 'bars which is useful when travelling at <5mph .

[Edwards]

The big jump is one of the complaints about the Compact Chain. I also change down or up at the rear to minimise this but going by the noise from the rear (if I/we keep the power on) feel that if you can avoid doing so is good.
I was only pointing out one of the downsides of such a big jump.

[willem jongman]

The OP has said he does not want to spend that much money, but needs somewhat lower gears. The cheapest route is if either the cassette or the small chainring need replacing anyway because of wear. If so, the cost of lower gearing per se is zero. So if you need a new 9speed cassette, get a 11-34t or even better a 12-36t. Similarly, a smaller front ring costs nothing if it needs replacing anyway, but even if not, a small steel ring costs almost nothing, and may not be a bad idea for the small ring anyway. The official range for a front triple is 22t between smallest and largest, but 24t difference will work fine, and 26t may work. So going down to a 26t inner ring should be fine, but 24t may stretch it. Be careful that if you change both front and rear now or later, that you do not exceed the capacity of the rear mech by too much.
Willem

[CJ]

CJ has a system for measuring the min small chain ring. If I remember correctly...

Thanks but not quite. It goes like this:

To measure how low you can get, engage your existing inner ring with the smallest rear cog you really need to use with inner. Lean an elbow on the right pedal to tension the chain and see what's the biggest allen key you can poke underneath it in the front mech cage. The key figure is 2mm per tooth. So if an 8mm key goes in there, you can reduce the inner ring by 4T.

With a 50 outer, you may well be able to use a 24 inner - with the inner (i.e. taller) half of the cassette at least. A Jump-Stop is always a wise precaution, even with the size of inner the chainset originally came with. And a bigger jump isn't a problem if you flick up a couple of cogs with the right hand at the same time as you drop to inner with the left. I used to double-shift back in the days of down-tube friction controls (poked the left lever forward with my thumb whilst tugging the right with two fingers) but now we have STI and Ergopower anyone can do it - so do it!

If you're planning also to reduce the outer ring, you can make a further equal reduction to the inner - assuming there's scope to move the front mech down the frame, 2mm for each tooth reduction in the outer. TA make a 38 middle to fit 130bcd, so 24,38,48 is possible on those cranks, but more cost.

As Willem rightly says, a bigger cassette may be a more economical and more effective way to lower gears. Except I guess you may be just about managing to shift that 32 sprocket with the road mech this bike came with, and 32 will be as far beyond its capacity as you can go. So: a bigger cassette will definitely need a MTB mech, which will shift fine with your STI so long as its Shimano and 9-speed.

To use the rather handy 12-36 9-speed cassette you'll need the Shadow design of rear mech. And you'll need to buy it soon, as the top class MTB groupsets where you find this design of mech are all going 10-speed this year. That's a pain because Shimano's MTB 10-speed system, which they call Dyna-Sys, has a totally different shift ratio and won't play with any other shifters made by Shimano or anyone else. So once all the 2010 model year 9-speed shadow mechs sell out, that'll be the end of the road for 36 tooth bottom cogs. I've already bought my spare XT 9-speed Shadow - for the day when I'll be needing lower gears and unable to afford new shifters on my pathetic CTC pension!

[willem jongman]

But:
1 Does this bike have a road rear mech?
2 Do you really need a Shadow rear mech for 36t? I have been led to believe that this again is one of those moments where reality is more flexible than the Shimano rulebook. But I have not tried it yet. This is what Harris Cyclery/the Sheldonbrown site says: http://harriscyclery.net/itemdetails.cfm?ID=3054
Willem

[byegad]

My current set up is a road triple 50/39/30. I used this for the Pyrenees last year, fully loaded and although I just managed there was the odd occasion when I looked down and saw nothing was left and perhaps wished there was! Cassette is 11-32.

Any Issues with swapping the 30 ring to a 26 before my next tour (Pyrenees and French Alps). My chainset is a Shimano Tiagra 4503 triple. I was thinking of dropping in something like this from Spa for the tour just for them steep mountain passes.

http://www.spacycles.co.uk/products.php ... b0s149p245

Will this give me that little extra before I have to get off and walk and will it involve much tweaking?

I have the same triple on my Kettwiesel recumbent and yes a 26 drops right in. Also consider an 11-34 cassette again should be no issue. I've swapped 11-32 to 11-34 on a few bikes and trikes over the years. I find the spacing is more even than the 11-32 which has a half set up to top compared to the other steps on that cassette.