Compact double road

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Si
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Compact double road

Postby Si » 13 Jun 2018, 5:07pm

Never had one before but my new road/gravel bike has one. I'm far from convinced.

I think I've only used the big ring about twice. The little ring is OK for road work but struggles at lower end off road on the steeper loose stuff. I'd imagine that it would also struggle on road fully loaded in the hills.

To my mind they've done it the wrong way around: rather than replicating a middle plus a big chain ring of a touring triple they should have done a middle plus a grannie. When I use my touring triple I rarely use the big ring, mostly in the middle but a bit in the grannie. I seem to spend all my time in little chain ring but on the smaller sprockets which is a recipe for wearing stuff out quicker.

But then I'm old and broken.....I remember when all I needed was a 52/42 and a big sprocket of 26....seemed to get me up the local Shropshire steep hills OK.

Might have to swap the chain rings for something smaller.

Bez
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Re: Compact double road

Postby Bez » 13 Jun 2018, 5:20pm

Can you go smaller? Most come with a 34 (some a 36) which is as low as you'll go. On the bright side, the current trend for big cassettes might solve your problem, albeit at the slight expense of closeness of gearing.

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Si
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Re: Compact double road

Postby Si » 13 Jun 2018, 5:24pm

probably can't go smaller on the current cranks, but could swap for an mtb triple and leave the big ring off I guess. Although one redeeming feature of the current double is the noticeably narrower Q factor.

Not sure if a change of cassette would help both issues - would certainly give a smaller bottom gear, but most of the time I'd still be cruising on a small sprocket and wearing it out faster than if my default was a larger sprocket with more teeth to spread the load.

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Re: Compact double road

Postby Bez » 13 Jun 2018, 5:47pm

What about one of those new-fangled MTB doubles? Not that they're new since 1x showed up, but they're newer than all my MTB kit ;)

Not sure what your ideal chainring sizes are, though…

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Si
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Re: Compact double road

Postby Si » 13 Jun 2018, 6:36pm

Must admit that new tech developments have left me behind. Will investigate mtb doubles thanks.

I'd like a bottom os 22inches and a normal cruising gear of about 55- 60inches, plus a few in between!

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Re: Compact double road

Postby reohn2 » 13 Jun 2018, 7:12pm

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Si
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Re: Compact double road

Postby Si » 13 Jun 2018, 7:40pm

Nice, and it uses a proper BB too!

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Re: Compact double road

Postby reohn2 » 13 Jun 2018, 7:57pm

Si wrote:Nice, and it uses a proper BB too!

:wink:
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LinusR
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Re: Compact double road

Postby LinusR » 13 Jun 2018, 8:10pm

Si wrote:Might have to swap the chain rings for something smaller.


You can fit a 33 inner ring on a compact, not as if it gains you much... On my road bike I replaced my Campag 50x34 with 48x33 TA rings, but I'm limited to 13-29 with a Campag 10 speed cassette. I'd prefer to have a 32 rear cog as I'm now heavier and older. For my gravel bike I have Shimano 46x34 with 11-34, also 10 speed.

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foxyrider
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Re: Compact double road

Postby foxyrider » 13 Jun 2018, 8:57pm

Pretty sure that my first dabble with a compact had a 48 outer, not sure when it grew to 50.

Given I tour on a 50/34 and 12-29 i'm probably not the best one to talk but I agree that for a gravel bike a 50 outer sounds rather optimistic. (I did inadvertently do some 'gravel' riding on my roadbike at the weekend mind, that has 52/34 and no clearance for even 25mm tyres!)
Convention? what's that then?

Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

slowster
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Re: Compact double road

Postby slowster » 13 Jun 2018, 9:04pm

Si wrote:Nice, and it uses a proper BB too!

I too have found that a 46/36 chainset with an 11-28 10 speed cassette is too highly geared on a gravel type bike fitted with 40mm On One 'Gravel Road BSC' tyres, and am planning on getting a Spa Super Compact, probably the 40/24.

What I don't know is whether the chainset and chainrings Spa supply are 9, 10 or 11 speed compatible (ideally I would like the rings to be 10 and 11 speed compatible, but I suspect it's more likely to be 9 and 10 speed compatible).

Another thing that puzzles me is that Spa recommend the following axle lengths for their TD2 chainset:

Ordinary Double -110mm
Triple - 113mm
Super Compact Double - 115mm

Since the Super Compact Double is effectively a triple with the outer ring removed, I am puzzled why a longer axle is recommended than for the triple (albeit only 2mm longer).

I also don't know how well a standard road front derailleur would work with such small inner rings, i.e. not only is the shape/curve of the derailleur designed for much bigger rings, I suspect some standard road front derailleurs would foul on the chainstay (and/or the mudguard) when lowered on the seat tube for the smaller rings. I have read that some people have been able to address this problem by replacing the front derailleur with the Shimano FD-CX70 front derailleur, which is designed for 46/36 cyclocross chainsets.

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Re: Compact double road

Postby Bez » 13 Jun 2018, 9:18pm

I am puzzled why a longer axle is recommended than for the triple (albeit only 2mm longer).


Because with fewer chainrings you tend/need to use a wider range of the cassette in each one. Normally you'd align the middle of the set of chainrings with the middle of the cassette, which would normally demand a 5mm longer BB spindle if you used the inner and middle of a triple, but I assume Spa felt that would spread the pedals a bit wide and that the extra 2mm is a compromise. In practice there's usually a bit of leeway to play with.

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Re: Compact double road

Postby Valbrona » 13 Jun 2018, 9:32pm

LinusR wrote:On my road bike I replaced my Campag 50x34 with 48x33 TA rings, but I'm limited to 13-29 with a Campag 10 speed cassette. I'd prefer to have a 32 rear cog as I'm now heavier and older. For my gravel bike I have Shimano 46x34 with 11-34, also 10 speed.


I think Interlock Racing Design might do a Campag 32.
I should coco.

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Re: Compact double road

Postby dragonrider » 13 Jun 2018, 9:44pm

Met a chap the other day who seems to have solved this with a 40 tooth cassette. He texted me and these are the details he sent -

“The brand name for my cassette is Sunrace (mine is 10 speed MX3 11-40) the link/dropper for rear mech is Wolf Tooth Road Link. Both were from Spa Cycles.

First time used this morning but I was really impressed mechanically with both range & smooth changing.”

So info passed on and not my own experience but he is a sensible chap and it seemed worthy of following up. I guess the above would cost £60 or so in parts.

I will certainly look at this option myself as if I buy a new road bike I can then retain hydraulic discs with a double standard compact chainring. Can’t do that with a triple as as it would then have to switch to mechanical discs.

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Re: Compact double road

Postby peetee » 13 Jun 2018, 9:55pm

I am itching to get my new off road creation back from the spray shop. It's a Nigel Dean 753 touring frameset which will be decked out in Dura Ace 7800 triple group, Mavic A719's and 30c Schwalbe CX Pro's with a low gear of 30x25. Should be ideal for blats round the New Forest.
I don't like the big step of modern double crankset. My everyday bike has 8 speed set up with 48-39 and 12-25. I am pushing 53 and that's enough to get me up a short length of 20%.
Current status report:
Latter side of fifty and feeling less than nifty.
Too many bikes on pegs and too few miles in the legs.