SUN XCD and other super compact chainsets

[jamesld8]

I`m looking to reduce double inner ring size and one way forwards seems to be to use a super compact chainset. From google searches there seem to be a few available now  eg Sugino OX601, Velo Orange and Sun XCD. The latter two look very much like the old TA chainsets but I wonder how they`d function with a `normal` Campag front mech, are the rings offset too far from BB to work well  ? I`ve seen a Sugino OX601 and it looked quite good, nice narrow Q factor, maybe a better choice?

ta

[rogerzilla]

Have you considered a normal 53/39?  Unless you ride up mountains, 39 x 25 should be enough for a lightweight bike, and many have a 28T on the back anyway.  If it's a tourer, a triple is still traditional.  I don't think compacts work if your normal cruising speed is 18-20mph and you spin reasonably quickly - this means you're always in that horrible double-shift zone.

[andrew_s]

The latter two look very much like the old TA chainsets but I wonder how they`d function with a `normal` Campag front mech, are the rings offset too far from BB to work well  ?

With square taper, you just choose the right BB length to get the right chainring offset (113 mm seems to be recommended).

The problem with genuine old TA Cyclotouriste or 49D chainsets was that the crank arm was too close to the big chainring for modern indexed front mechs, and the crank arm would bash the mech every pedal rev. Equivalently old front mechs had narrower cages, with the expectation that you would trim them using your non-indexed shifter if you got chain rub.

The VO version has a larger gap than original, suitable for modern mechs. I'd expect the XCD to be similar, but you'd need to check.

[andrew_s]

I don't think compacts work if your normal cruising speed is 18-20mph and you spin reasonably quickly - this means you're always in that horrible double-shift zone.

That may be the case with a standard 50/34 compact, but I'd guess the OP is looking at 44/28 or similar, in which case he'd do all his non-hill riding on the 44.

[jsabine]

I don't think compacts work if your normal cruising speed is 18-20mph and you spin reasonably quickly - this means you're always in that horrible double-shift zone.

That may be the case with a standard 50/34 compact, but I'd guess the OP is looking at 44/28 or similar, in which case he'd do all his non-hill riding on the 44.

Yes. I like triples, but find I'm almost always in the middle ring. I didn't get on with a standard compact at all well, and keep meaning to try something like a 44-28 or 42-26.

I really don't think I'd miss the top end at all.

[jamesld8]

I don't think compacts work if your normal cruising speed is 18-20mph and you spin reasonably quickly - this means you're always in that horrible double-shift zone.

That may be the case with a standard 50/34 compact, but I'd guess the OP is looking at 44/28 or similar, in which case he'd do all his non-hill riding on the 44.

Yes I`m thinking something like 46 / 30 with a 12-34 cassette (IRD campag one) ---currently have a 46 outer on campag and it works very well as the normal cruising along gear range chainring. Maybe even a 44 /28.

[P Walsh]

I don't think compacts work if your normal cruising speed is 18-20mph and you spin reasonably quickly - this means you're always in that horrible double-shift zone.

That may be the case with a standard 50/34 compact, but I'd guess the OP is looking at 44/28 or similar, in which case he'd do all his non-hill riding on the 44.

Yes I`m thinking something like 46 / 30 with a 12-34 cassette (IRD campag one) ---currently have a 46 outer on campag and it works very well as the normal cruising along gear range chainring. Maybe even a 44 /28.

Put something like that on a bike for my wife, just using cheap Spa Cycles triple cranks with the outer space occupied by a chain guard ring (black). Looks okay, in an old school sort of way. Shimano UN 55 bb. Chain rings of your choice, down to about 24 if you really want it. About £100 for the lot.

[Bruise Willies]

I'm just about to embark on something similar. I was going to get the SunXCD, as I believe it does away with the old problems associated with the TA cranks (e.g. crank clearance, threads etc.) I think the Q-factor is still good and perfectly useable with 9-speed (maybe 10) chains.
I ended up getting a set of the older Sugino PX, as they came up at a good price, just a more modern looking crank arm.
I had been using a compact double with 34-46, and there just wasn't enough of a gap between the tooth sizes.
I think Velo-Orange are also testing an Ultra-Compat double right now, similar to the Sugino OX. 

[Cudzoziemiec]

I'd never heard of SunXCD but their cloverleaf chainset is rather gorgeous.


Shame it's £210.

[Mr Larrington]

Long before "compact" chainsets were A Thing I used to use a 42/28 Stronglight 99 with a 6-speed 13-32 block.  I was a Penniless Student Oaf and couldn't afford a triple.

[psyclist]

I've been eyeing up a super or sub compact chainset. Currently I'm running 50/34 and 11/32, which is fine for rides in the south east but as soon as I hit the really good hills in Wessex and up north, I run out of gears low enough.

Calculating the gear ratios in inches (I'm running 700C with 35mm tyres), I have a range of 124 - 43 on the big chainring, and 84 - 29 on the smaller one. If I were to reduce to 46/30 chainrings, those ranges would become 114 - 39 and 74 - 26. This is equivalent to losing my small cog at the back, and gaining an additional big cog. In practical terms that works out fine, as I doubt that I have ever used 50:11, but I could certainly have used a 30:32 in the Lake District.

Aside from whether I can get compatible chainrings (may need new cranks) for my Campag 11sp setup, my question to myself is whether I should go even lower, with say a 44/28. It is so difficult to determine the most suitable setup when living so far from the extreme climbs which beckon.

[Biggsy]

I say go directly to the smallest chainset you think you'll ever need.  If it turns out to be too low for now then you can change the cassette to compensate - an adjustment that can be done and reversed relatively cheaply and easily.  There may be some loss of mechanical efficiency from smaller cogs all round, but this is arguably less important than being well prepared.

I gradually lowered my gears in many small steps until I arrived at what I wanted - which I now realise was too cautious.   In my case I was just changing the inner ring of a triple* rather than the whole chainset (like you will need to with a Campag compact double to get smaller than 34T).

* 34T originally, so had loads of scope, ended up with 26T.

[mzjo]

Long before "compact" chainsets were A Thing I used to use a 42/28 Stronglight 99 with a 6-speed 13-32 block.  I was a Penniless Student Oaf and couldn't afford a triple.

In the days when cheapskates used single rings and cotter pins I had a 44/24 double made by brazing a 24t rear sprocket (off a Cyclo 5sp block) onto a Nicklin chainset. The 14t sprocket off the same block was used as a spacer with crank brazed one side and 24t sprocket the other. Some tea leaf went and pinched the bike just as I was getting to feel the benefits.

[jamesld8]

I'm just about to embark on something similar. I was going to get the SunXCD, as I believe it does away with the old problems associated with the TA cranks (e.g. crank clearance, threads etc.) I think the Q-factor is still good and perfectly useable with 9-speed (maybe 10) chains.
I ended up getting a set of the older Sugino PX, as they came up at a good price, just a more modern looking crank arm.
I had been using a compact double with 34-46, and there just wasn't enough of a gap between the tooth sizes.
I think Velo-Orange are also testing an Ultra-Compat double right now, similar to the Sugino OX.

I`ve ended up getting a SUNXCD 46 / 30; it`s a beautifully finished crankset with TA vis rings. Although there`s a `disclaimer` about being only 6/7/8 speed it works well on 10s and the seller also tells me that he`s sold similar to someone using 11s. Yet to be used in real anger, but lined up for Barmouth Blvd next w/e and joys ( ?) of Trawsfynydd Mtn Rd and Bwlch Y Groes so a real testing in store

[Samuel D]

I would be very interested to know (a) what bottom bracket you’re using with the SunXCD (pronounced “exceed”) cranks and Spécialités TA chainrings and (b) what the resulting chainline is.

I have these cranks, but with the 110 mm BCD spider. They’re very light and pretty. Not as stiff as Shimano’s hollow cranks and bottom bracket spindle, but I don’t know if that practically matters at all (it may even be beneficial!).

I considered getting a pair of perfectly sized Pro 5 Vis chainrings for them, but the considerable price and confusion around the ideal bottom bracket length put me off. I may yet do so.

[jamesld8]

I`ve used the recommended 118 mm square taper; it was almost a direct swop in chainline terms for the Campag UT compact they`ve replaced, ie apart from lowering front mech position the front mech setup was spot on from Campag setup. In terms chainline 46 T ring looks to be a straight run to 5th / 6th sprocket.

I may though try a 113 BB to reduce Q factor... which I`d expect make chainline straight to maybe 4th sprocket

Hope this helps

[Samuel D]

Thanks! Which 118 mm bottom bracket is it? I don’t think they’re all quite the same.

Sometime when it’s least hassle, it would be great if you could put the chain on the inner ring and measure the distance from the side of the down tube to the middle of the teeth on the outer ring. Then say how wide your down tube is.

I have successfully used a 113 mm Shimano bottom bracket with these cranks and the 110 mm BCD spider (but I’m not sure if that places the rings in the same place as the Pro 5 Vis chainrings). With my Spa Audax, the cranks even work with a 107 mm Shimano bottom bracket, albeit barely and with an unusually narrow chainline.

[jamesld8]

a cheap ex Genesis BB, which does measure 118mm across ends

Seatube dia 29 mm, centre chainring - edge seatube 34 mm, so C-C distance is 48.5 mm; so chainline to centre cassette lies 11.5 mm inside RH rear dropout face (130 mm hubs) on a 10s setup

[Samuel D]

Thanks! That’s still slightly too outboard for my preference, but a shorter bottom bracket would probably work.

It is differences in asymmetry between different bottom brackets that concern me, not whether they are exactly their stated spindle length (they usually aren’t but are close enough).