Supercompact 46-30 Chainset on Road Bike

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NickJP
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Re: Supercompact 46-30 Chainset on Road Bike

Post by NickJP »

TheBomber wrote: 26 Aug 2022, 8:27am
NickJP wrote: 25 Aug 2022, 10:01pmSpa sell 94BCD TA chainrings in 29 or 30 inner and 42-50 outer. The RO2 isn't cheap, but it's very nicely made and very pretty.
Nick - what chain speed are those TA rings being used with? I have a similar setup to the one the OP is looking for - Middleburn RO1 40x30 on a 10sp bike. I had trouble finding suitable 10sp 94bcd chainrings and noted that the TA ones are only described as 9sp. Eventually I found Middleburn rings that were described as 10sp but got chainsuck problems when shifting down at the front.
The chainrings say 9/10 speed, but I'm using them with 11-speed chain and cassette. I've never bothered about what speed chainrings are intended for, and I think it's really not an issue. Leanard Zinn at Velonews seems to agree, see https://www.velonews.com/gear/tech-faq- ... -answered/. I think that if you're getting chainsuck, that's not the cause of the problem. At the moment I'm using a Deore XT M737 crank and some old Sugino chainrings, both dating from the days of 8-speed chains/cassettes, with an 11-speed chain and cassette, and no shifting problems there. Ditto with an XTR M900 crankset (also 8-speed being used with 11-speed chain/cassette) on another bike.

The only mixture I encountered problems with was a Sugino PX crankset with TA Cyclotouriste chainrings, where an 11-speed chain tended to skate between the chainrings when changing down (unsurprising since the outer width of an 11-speed chain is about 2.5mm less than that of the 5-speed chains in use when those chainrings were designed. I fixed that problem by replacing each of the the ~4mm thick washers that spaced the chainrings apart with three 1mm thick washers, to bring the chainrings closer together, and no more front shifting problems.
TheBomber
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Re: Supercompact 46-30 Chainset on Road Bike

Post by TheBomber »

Vaughan wrote: 26 Aug 2022, 8:39am I think there is a corrosion action between carbon and aluminium which affects the aluminium in preference.
Presumably it’s actually between different grades of alloy - the rivets and the hanger? When attaching fittings to an aluminium mast of a yacht it is normal to use ‘monel’ rivets to avoid corrosion problems. They’re harder to use than aluminium jobbies but it’s still possible with a basic rivet ‘gun’.
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Cugel
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Re: Supercompact 46-30 Chainset on Road Bike

Post by Cugel »

NickJP wrote: 26 Aug 2022, 8:19am
BTW, if you ever decide on a smaller large chainring than the adjustment on a frame's braze-on derailleur hanger allows, Sugino and Wickwerks both sell adapters that allow the derailleur to be mounted lower than the braze-on hanger on its own allows. If you have a look on the image in my previous message, I used the Sugino adapter to get the FD down to the correct height for the 42t chainring. Here's a better photo of the adapter on one of my wife's bikes that has a 39t "big" chainring:
IMG_20180102_144900.jpg
Hello Nick,

I'm after two or three of those FD lowering gubbins myself (to replace 50t rings with 46t rings, with the recommended 1-3mm height gap of front mech cage above big chain ring teeth). There seem to be three manufacturers: Sugino; Wickwerks and IRD.

The Wickwerks can only be got from the USA Wickwerks website at the moment (no European distributors) and they themselves say this will increase the cost ($45) dramatically, as well as be likely to go missing in the post!

The Sugino appears to be available from only Dolan in the UK, at price of near £60! This feels like a rip-off for such a simple and tiny thing. Am I willing to pay? Only with a gripe, moan, whine and several other unhappy noises. :-)

The IRD is sold by SJS Cycles but they have no stock at present.

Do you know of any other sources for any of these? If so I'd be very grateful for any links.

Cugel
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes
slowster
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Re: Supercompact 46-30 Chainset on Road Bike

Post by slowster »

Cugel wrote: 26 Aug 2022, 10:34am The IRD is sold by SJS Cycles but they have no stock at present.

Do you know of any other sources for any of these? If so I'd be very grateful for any links.
https://southerndistributors.co.uk/prod ... n-adaptor/
slowster
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Re: Supercompact 46-30 Chainset on Road Bike

Post by slowster »

Vaughan wrote: 26 Aug 2022, 8:39am And as for my hanger, yes it is held on with pop rivets. It came with these and I have had to replace them a couple of times over the eight years since I got the bike. I think there is a corrosion action between carbon and aluminium which affects the aluminium in preference.
The internal surface of the seat tube should have a layer of glass fibre mat where the rivets will be installed, and the rivets should be installed 'wet' with resin on the surfaces that will be in contact with the carbon fibre. The same applies to bottle cage bosses. Some frame manufacturers do this, but not all.
TheBomber
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Re: Supercompact 46-30 Chainset on Road Bike

Post by TheBomber »

NickJP wrote: 26 Aug 2022, 9:43am The chainrings say 9/10 speed, but I'm using them with 11-speed chain and cassette.
Well that's good to know - but I am a little confused as the ones in your photo from earlier clearly say '9 speed'? This accords with what I found from TA's website and what others (eg SJSC) seem to say. Spa don't state a chain compatibility at all.
NickJP wrote: 26 Aug 2022, 9:43am I've never bothered about what speed chainrings are intended for, and I think it's really not an issue.
The trouble with deviating from what is stated (eg 10sp chain on 9sp chainrings) is it is all fine until it isn't. Then when your chain stay is loosing 'skin' on every ride, I start to get a bit anxious that the problem is self inflicted.

Thank you.
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Cugel
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Re: Supercompact 46-30 Chainset on Road Bike

Post by Cugel »

slowster wrote: 26 Aug 2022, 11:13am
Cugel wrote: 26 Aug 2022, 10:34am The IRD is sold by SJS Cycles but they have no stock at present.

Do you know of any other sources for any of these? If so I'd be very grateful for any links.
https://southerndistributors.co.uk/prod ... n-adaptor/
Thank you.

Cugel.
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes
GideonReade
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Re: Supercompact 46-30 Chainset on Road Bike

Post by GideonReade »

TheBomber wrote: 26 Aug 2022, 9:52am
Vaughan wrote: 26 Aug 2022, 8:39am I think there is a corrosion action between carbon and aluminium which affects the aluminium in preference.
Presumably it’s actually between different grades of alloy - the rivets and the hanger? When attaching fittings to an aluminium mast of a yacht it is normal to use ‘monel’ rivets to avoid corrosion problems. They’re harder to use than aluminium jobbies but it’s still possible with a basic rivet ‘gun’.
But if the rivet's "mandrel break force" is increased because of the harder monel rivet material, then it may cause problems crushing the relatively soft CF layup? My speculation, not knowledge.

When I was replacing corroded ally rivets on canoe as remarked above, I looked at stainless steel rivets. But the mandrel break force, ie the compression applied to fix the rivet, was double that for ally. I think it would have been way too much for the polythene canoe. Finally I used ally peel rivets, which are designed for low compression applications. Eventually turned out so did the OEM. I'm not sure what CF would require, though I note remarks above about applying "wet". I suppose with the right jig and access from seatpost hole, one might manage to fit a backing washer inside (but curved?).
slowster
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Re: Supercompact 46-30 Chainset on Road Bike

Post by slowster »

Carbon fibre is conductive and will cause galvanic corrosion of aluminium in contact with it. Fibre glass is not conductive, and a layer on the inside surface of the cabon where derailleur hangers and bottle cage bosses are attached will help to electrically insulate the metal from the carbon fibre.

Examples both of frames where fibre glass insulation is present and of frames where it is missing can be seen in Raoul Luescher's videos of cut up carbon fibre frames.

https://www.youtube.com/c/LuescherTeknik/videos
TheBomber
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Re: Supercompact 46-30 Chainset on Road Bike

Post by TheBomber »

slowster wrote: 26 Aug 2022, 6:02pm Carbon fibre is conductive and will cause galvanic corrosion of aluminium in contact with it.
Every day is a school day. So where does it sit in those tables of susceptibility to galvanic corrosion? I’m guessing at the top, meaning it contributes to corrosion in attached metals but never suffers itself?
GideonReade
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Re: Supercompact 46-30 Chainset on Road Bike

Post by GideonReade »

I understand that carbon fibres are conductive. But made into a tube, bicycle, canoe, Airbus or whatever, how conductive is the bulk material? The resin used is epoxy based isn't it, which IIRC is often used as a potting compound to seal electronics, which would make it an insulator. Since the resin should thoroughly wet, ie coat, the fibres (one of its jobs being to stick them together), that would suggest the exposed faces of a CF product should insulate. On the outside, there may be or not a finishing fibreless later, like gelcoat. Which I'd expect to insulate too.

Of course, if our rivetter then drills holes in it, fibres will be exposed, allowing conduction. At least to one fibre, presumably the woven strands touch...
NickJP
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Re: Supercompact 46-30 Chainset on Road Bike

Post by NickJP »

TheBomber wrote: 26 Aug 2022, 2:31pm
NickJP wrote: 26 Aug 2022, 9:43amThe chainrings say 9/10 speed, but I'm using them with 11-speed chain and cassette.
Well that's good to know - but I am a little confused as the ones in your photo from earlier clearly say '9 speed'? This accords with what I found from TA's website and what others (eg SJSC) seem to say. Spa don't state a chain compatibility at all.
NickJP wrote: 26 Aug 2022, 9:43amI've never bothered about what speed chainrings are intended for, and I think it's really not an issue.
The trouble with deviating from what is stated (eg 10sp chain on 9sp chainrings) is it is all fine until it isn't. Then when your chain stay is loosing 'skin' on every ride, I start to get a bit anxious that the problem is self inflicted.
The chainrings in the 1st photo only say '9 speed', the ones in the 2nd photo say '9/10 speed'. Both behaving flawlessly with 11-speed chains. In any case, I can't recall when I last got chainsuck with any combination of chainrings/chains - must have been several decades ago - so it's not something that I regard as an issue. If you are finding that the chain drops inside the small chainring and jams between it and the chainstay, that's indicative of a badly adjusted/aligned front derailleur. If your frame has a round seat tube, you can fit a dog fang/chain watcher and eliminate that problem:
Image
TheBomber
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Re: Supercompact 46-30 Chainset on Road Bike

Post by TheBomber »

NickJP wrote: 27 Aug 2022, 6:17am The chainrings in the 1st photo only say '9 speed', the ones in the 2nd photo say '9/10 speed'. Both behaving flawlessly with 11-speed chains.
Obviously if the 9sp ones are working well then that’s all good, but only the ones in the first photo are the 94bcd models that the OP (and I) would need. The ones in the second photo won’t fit the spider.

Which reminds me - the OP could get an ‘Incy’ spider for a Middleburn RO2. That uses widely available 110bcd outer rings though I forget what bcd the inner is. Incy spiders are unavailable for RO1 cranks.
mattsccm
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Re: Supercompact 46-30 Chainset on Road Bike

Post by mattsccm »

I am planning the same thing. I currently use a 28/42 combo on one bike but need something a touch higher. Thats a MTB double chainset from the short period when it was fashionable.
One small issue for me is that something like the Spa setup uses a triple with no outer ring. Works fine, looks messy and adding a chain guard doesn't solve that. Having said that most MTB doubles and even stuff like the GRX actually are based on the same idea. All they do is smooth off the step where a missing outer might go. Call me old fashioned but the outer ring should smoothly blend into the spider. :D
NickJP
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Re: Supercompact 46-30 Chainset on Road Bike

Post by NickJP »

mattsccm wrote: 28 Aug 2022, 8:05amI am planning the same thing. I currently use a 28/42 combo on one bike but need something a touch higher. Thats a MTB double chainset from the short period when it was fashionable.
One small issue for me is that something like the Spa setup uses a triple with no outer ring. Works fine, looks messy and adding a chain guard doesn't solve that. Having said that most MTB doubles and even stuff like the GRX actually are based on the same idea. All they do is smooth off the step where a missing outer might go. Call me old fashioned but the outer ring should smoothly blend into the spider.
Then go with a crank that uses the old TA Pro Vis 5 50.4 BCD chainrings. You can get outer rings from 40t to 52t and inners from 26t to 42t: https://specialites-ta.com/128-pro-5-vis. No shifting aids (pins or ramps) on the rings, though. However, if you're happy with a 46t outer, Velo-Orange make a compatible chainring in that size that has such shifting aids. The VO chainring bolts for 50.4 BCD cranks are also much superior to the TA bolts.
PXL_20210819_044625248.jpg
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