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Rear dérailleur ok?

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smegballs
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PostPosted: 17:56 - 03 Dec 2012    Post subject: Rear dérailleur ok? Reply with quote

http://i.imgur.com/lVW0Y.jpg

Just put a megarange freewheel on my old tourer-stylee bike to help out on the hills. I read that I might need a different rear mech due the big rear sprocket. Currently it shifts up onto the 34 OK doesn't slip, just looks a bit spacky (to me at least).

Need to get a new derailleur or does it look OK?
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stinkwheel
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PostPosted: 18:56 - 03 Dec 2012    Post subject: Reply with quote

Shocked

Is the jockey wheel hitting the sprocket? Looks like it from here.

What was wrong with a smaller granny ring?

And how steep exactly are these hills? Assuming you have a normal sort of gear range, I'd have imagined that gear would be pretty much unuseable/irrelevant on any road I'd be comfortable physically pedalling up without it being quicker to get off and push anyway.

I'm just intreagued now. What gearing are you running at the front? What size wheels?
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smegballs
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PostPosted: 19:07 - 03 Dec 2012    Post subject: Reply with quote

stinkwheel wrote:

I'm just intreagued now. What gearing are you running at the front? What size wheels?


Wheels: 27 x 1 1/4
Chainring: 42/52

I live in cornwall/devon so come across some pretty steep hills. 34/42 doesn't actually feel as low as I thought it would. I'm planning on riding around spain, fully loaded up with camping gear, in the summer so want a pretty low gear for the mountains, I might try getting a mtb triple up front by then.

Sheldon says:

http://i.imgur.com/Nsdoa.png
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D O G
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PostPosted: 00:38 - 04 Dec 2012    Post subject: Reply with quote

Looks fine to me - the real test would be to put it on the big ring on the front too, see what the extension is like then.
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D O G
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PostPosted: 00:44 - 04 Dec 2012    Post subject: Reply with quote

42 is a pretty evil 'little ring'.

I think your wheels are a smaller diameter than 700c road bike wheels, but typically modern roadbikes come with the 'compact' *cough, gay, cough* chainrings which are 50/34.

Non compact is 52/39.

Cassettes then generally 26-28/13-11.

So the lowest gear on a normal roadbike is probably about as low as what you've generated with your massive rear sprocket.
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smegballs
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PostPosted: 01:35 - 04 Dec 2012    Post subject: Reply with quote

D O G wrote:
42 is a pretty evil 'little ring'.

I think your wheels are a smaller diameter than 700c road bike wheels, but typically modern roadbikes come with the 'compact' *cough, gay, cough* chainrings which are 50/34.



I believe 27 x 1.25 (630mm) is just a touch bigger than 700c (622mm); close enough that you can normally whack 700c wheels in a 27" bike, drop the brake-pads down by a few mm and drive on.

The weird and wonderful world of bicycle tyre sizing does seem to be completely arbitrary and made up on the spot. Scratch that, bicycle dimensions, threads etc etc seem to vary between massively, sometimes even two of the same model will have different threading Shocked Laughing

Jockey wheel isn't touching sprocket, altho it is damn close, maybe only 5mm or so of clearance.
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D O G
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PostPosted: 01:41 - 04 Dec 2012    Post subject: Reply with quote

Well then your 42 small chainring is going to be pretty difficult on the sort of gradients you will get down there. If your next smallest is a 24 then fair play for you even getting up them before you fitted the extra large sprocket!
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stinkwheel
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PostPosted: 09:30 - 04 Dec 2012    Post subject: Reply with quote

I agree with others, that's a pretty nippy "granny ring" (although does it count as a granny ring when there are only two?).

Aye, the roads in Devon and Cornwall can be pretty steep going, especially round the coast.

I've got 23/18 gears on my single speed mountain bike running 700c wheels and 175mm cranks. That gives me 34.7 gear inches and I only just made it up some of the hills without luggage (although that is on horrifically knobbly tyres that had no business being on the road).
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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