Author Topic: Choosing a chainset  (Read 1867 times)

Choosing a chainset
« on: August 31, 2018, 02:07:36 pm »
The description:
The bike in question is a 531 Raleigh road bike with forward facing dropouts. My current setup is built on a bargain bin stronglight chainset and a square taper BB. It came with a 42,52 setup,and I've run the 42 (in conjuction with a 3/32" 16 tooth Dura Ace sprocket) for a long time. However, the 42 tooth ring and the 16 tooth sprocket are worn and need replacing (the sprocket is shark toothed, the chainring seems to have peened over on the edges). I switched to the 52 tooth ring for my TT experiment - I enjoyed it, but want to go back to 42ish for winter (and hilclimbs!). The BCD of my current chainset is obsolete (122), so chainrings are not plentiful and seem to be mostly in the bigger sizes.

The questions:
1.   How do I choose a chainset (preferably one that will last a long time)?  eBay has "track/singlespeed" ones from 15 quid to 200.
1a. How do I ensure that the chainline will be bearable?
1b. I assume BCD of 144 or 130 is fine - any benefits either way?
2.   What are the benefits/downsides for going 1/8th? (I currently have 2 NOS 1/8 sprockets kicking about, but a 3/32 chain installed)
2a. A half link would probably help keep things inside the dropouts - are they reliable, and is there any benefit to having a half link chain?

What am I missing?
As you can tell, I'm over-thinking this massively, but I've had this bike for ages (in a triggers broom sense) and I want to get it sorted so I can use it properly again.

Cheers
Duncan

Re: Choosing a chainset
« Reply #1 on: August 31, 2018, 06:35:46 pm »
You haven’t said what your current chainline is and whether there’s scope for tweaking it with spacers at the hub axle. There’s a list on lfgss of chainlines you get with various chainset BB combinations so you can get an idea what might match your hub.

Consider using a double crank set rather than a track one, with one ring on to give the option of putting it on either side.

1/8th is more rugged and generally longer lasting. But it is also more sensitive to chailine particularly if you use a chain with bushings. You should be fine without a half link with horizontal drop outs, even short ones. Don’t even consider a full half link chain, they are just bling for BMXers.
Quote from: tiermat
that's not science, it's semantics.

Re: Choosing a chainset
« Reply #2 on: August 31, 2018, 07:00:17 pm »
I'm not sure what my current chainline is. The frame is a 126oln frame that's just clamped together, and there are a couple of spacers between the cog and the hub, but the chainline is still a bit iffy. The ring is on the outside of the (double) crank at the moment with single ring bolts. I have 2 wheels I want to use - one is a Halo track hub with a worn carbon/alloy rim on it, and the other is a System Ex flip flop with an Open Sport. I figured they would have the same chainline - is that not necessarily the case?

I'll check out lfgss

JonB

  • Granny Ring ... Yes Please!
Re: Choosing a chainset
« Reply #3 on: August 31, 2018, 08:42:18 pm »
Some of the online suppliers give the chainline for various cranksets sets in combination with their recommended bottom brackets, Velodrome suppliers (https://www.velodrome.shop/index.php?p=home) are quite good for this but I think Velo Solo do for a lot of their cranksets as well (http://www.velosolo.co.uk).

My Dave Marsh sounds similar to yours with 126 OLN and horizontal dropouts but they're not as long as track ends and I found a half-link situated the wheel nicely in the dropouts for my gearing of 42*16. Never had any problems with them, I used KMC and I can't remember the other make but it was the one that Velo Solo supplied. Don't bother with a half-link chain, as Pickled Onion says all about bling and very noisy. There are probably more options for chainrings, chains and cogs with 1/8.

If you're on the outside of your double ring then you probably have a chainline around 47/48mm (Sheldon Brown has the data for this) which is probably why you have got spacers on the back hub. The hubs you've listed will probably run standard track chainline of 42mm so this is what you should be aiming for in your crankset, plenty of these around at various price points. The Stronglight track 2000 looks pretty good for £50 at Planet X at the moment (https://www.planetx.co.uk/i/q/CSSTTR2K/stronglight-track-2000-crankset).

Rogerzilla has a great write up on chainline here https://yacf.co.uk/forum/index.php?topic=104960.0

Re: Choosing a chainset
« Reply #4 on: August 31, 2018, 09:00:56 pm »
I used a Stronglight 2000 on a couple of bikes.   The matching BB from Planet X is also pretty solid.

There seems to be a better choice of 1/8th chainrings for 144BCD.   

I have moved from square taper to one piece now and have a Miche from velodrome shop on the race bike and a Sugino on the audax bike.   Both were a bit more spendy, though.

Re: Choosing a chainset
« Reply #5 on: September 01, 2018, 10:15:05 am »
First check your current chainline is good with a 2 foot steel rule.  Drop the chain off and hold the edge of the rule (NOT THE FLAT) against the outside face of the chainring, avoiding the bolts, and see if it lines up with the outside face of the sprocket.  If not, note how much it is out and which way.  Then measure your existing front chainline (from seat tube to centreline of chain, and add half the thickness of the seat tube, usually 14.3mm) and I'll suggest something.

You want to be within 1mm to avoid lopsided sprocket wear, even if it runs quietly with a bushingless chain.
Never tell me the odds.

Re: Choosing a chainset
« Reply #6 on: September 01, 2018, 11:53:22 am »
The chainline is about 1mm out currently (sprocket more inboard than chainring). The 2 spacers are different thicknesses - I think one is 2mm and one is just 1mm. I can measure this stuff accurately if it makes a difference, but I figure it makes more sense to aim for the regular track setup and then space the sprocket if necessary.
The measurement from edge of seat tube to middle of chain is currently: 27.5mm
The seat tube seems to be about 28mm, (parallax error permitting), so that sounds like it's the standard seat-tube size.

Re: Choosing a chainset
« Reply #7 on: September 01, 2018, 12:26:50 pm »
144BCD Andel track cranks (Hubjub) on Tange 110.5 BB gives a 42mm chainline - you currently have about that.  If you can remove a 1mm spacer from under the sprocket it will be perfect.

I would go 1/8".  It's not stronger but it lasts much better.
Never tell me the odds.

Re: Choosing a chainset
« Reply #8 on: September 01, 2018, 12:45:45 pm »
I'm not sure what the current BB length is, I just remember that it's a Shimano one. If it's 110mm, I assume that would be good with the Andel cranks (I can't see any branded Andel - I assume you mean these: https://www.hubjub.co.uk/single-speed-fluted-cranks-only-189-p.asp )?
If I have to change the BB anyway, is there any benefit in choosing those (as opposed to the Stronglight and associated BB or the Sugino on hubjub and a 103mm BB)?

I guess I need to strip the cranks and measure the bb now - it's just a straightforward end-end measurement, right?

Thanks for the help on this - I appreciate it. I'm trying to keep to a budget - sadly I would have probably been better off just buying a secondhand track bike by the time I'm finished!

Re: Choosing a chainset
« Reply #9 on: September 01, 2018, 01:03:32 pm »
Yes, those are the cranks.  They are basically a Campag Pista copy and give "track" chainline on a normal length BB as well as a narrow Q-factor and a vintage track look.

I don't know if your existing BB is suitable as some are not symmetrical.  The Tange one is known to work (I have that setup).
Never tell me the odds.

Re: Choosing a chainset
« Reply #10 on: September 01, 2018, 01:25:31 pm »
I measured the BB and it's 107 end-end, but irritatingly it's a bit offset (1 or 2mm) toward the drive side.  I guess if I want to be super precise that means I should probably just get another BB to make life easier.

Options:
1. Andel cranks £45, Andel ring £28, Tange 110.5 BB £22
£95
2. Stronglight cranks (with ring) £50 - needs 107mm BB, but can maybe keep my existing one?
£50

The Sugino I saw had a 44mm chainline on a 103 BB, so that's probably ruled out (would need a new BB and isn't the ideal chainline anyway).

Have you tried the Andel cranks with other chainrings - the hubjub write-up says that they might need a bit of filing to make other brands fit?

Thanks
Duncan

Re: Choosing a chainset
« Reply #11 on: September 01, 2018, 01:53:15 pm »
No, I bought the Andel ring too.  I don't have any other 144BCD rings; my "real" track bike has TA track cranks and they're 130BCD.  TA always do their own thing!
Never tell me the odds.

Re: Choosing a chainset
« Reply #12 on: September 03, 2018, 09:00:54 am »
I've gone for the Stronglight on the basis of cheapness. Hopefully I can make the chainline work - I guess I will find out in a few days when it arrives. Also ordered an 18 tooth sprocket (48x16 is too heave for general riding and especially hillclimbing!), and a new chain.

Thank you for your help on understanding my options. Even if I didn't quite take the advice, it was still useful in terms of working out what I needed to achieve.  :thumbsup:

Re: Choosing a chainset
« Reply #13 on: September 10, 2018, 09:05:29 pm »
Well the stronglight chainset arrived, and it looks really cool. Sadly, when I put it on the BB, the chainline is miles away. With the spacers as currently fitted, it lines up really well with the edge of the lockring (which is 5mm thick), not the sprocket. I guess I need to change the BB or the frame. Being that far out makes me wonder if the frame is straight - how can you tell? It's a 126mm steel rear triangle, with a 120mm hub, so there's going to be some spring.

I'll see if I can take it into the broken spoke workshop on the weekend and make sure the BB shell is faced properly - I guess paint might explain why the current BB is a bit offset towards the drive side. Unfortunately I doubt it's going to get me more than a mm or 2, and I could really do with 5. If I can clear some paint off and pull the chainline in a couple of mm, will a 103mm BB then do the rest? That should be 4mm narrower than the current 105, which I assume will mean 2mm narrower on each side?

JonB

  • Granny Ring ... Yes Please!
Re: Choosing a chainset
« Reply #14 on: September 11, 2018, 07:37:29 am »
That's a blow and a bit strange. It probably is worth getting the frame checked for alignment and there's plenty of info on doing this via google.

The rear spacing shouldn't affect it unless when you're pulling it in to meet the hub it's moving more one side than the other, on my 126mm I fitted spacers from velo solo but it might be worth trying with a couple of washers and seeing if it makes any difference. As you say, facing the paint off the BB shell shouldn't make much difference but won't do any harm.

103mm bottom bracket sounds like it should put you somewhere handy but it would be nice to know why it's out as that crank is supposed to have 107mm for a 42mm chainline ??? Good luck and let us know how you get on.

Re: Choosing a chainset
« Reply #15 on: September 11, 2018, 05:40:11 pm »
Measure the front and rear chainline separately.  If they are the same, the rear triangle is off to one side.  You should absolutely cold set the frame to 120mm and when doing this you can get the alignment right.  Springing it in every time is a crapshoot, as the spring rates of the left and right sides are probably different.
Never tell me the odds.

Re: Choosing a chainset
« Reply #16 on: September 13, 2018, 08:12:11 pm »
The front chainline is about 48mm. I'm not sure how that happened.
The rear chainline is about 44mm (and has 2mm spacers between hub and sprocket), so that makes sense.
The rear triangle is a bit wonky - I used the string method here: http://www.mytenspeeds.com/My_TenSpeeds_1/Site%20Contents/How_To_Do_It/FrameSetPrep_5_StringingFrameSet.htm
I measured from the seat tube to the string gives me 30mm on the right hand side and 36mm on the left. Not sure what that actually means!
I need to get into the Broken Spoke, face the BB shell, reset the rear triangle and probably also fit a 103mm BB if they have one (if they don't I'll have to internet it). Hopefully I can sort it so that the 42mm chainline at the back is replicated at the front. Seeing as I'm going to be cold setting the rear triangle, would there be a problem with having the rear triangle slightly offset to the drive side (so that say a 44mm chainline at the cranks fits a 42 mm chainline at the back wheel), so long as the dropouts are parallel?

Re: Choosing a chainset
« Reply #17 on: September 13, 2018, 08:59:41 pm »
Well, the bike won't *quite* ride properly but 2mm is nothing - 4mm error is common on new frames.

Do you have an ISO crank on a JIS bottom bracket?  That would sit a few mm too far out.

No need to bother with string in your case.  First get the front and back chainline the same, measured independently, and then pull the RH side of the rear triangle to make the chain and sprocket line up with your steel straight edge.  Then just pull the LH side of the rear triangle to get 120mm spacing.  It will be spot-on then.

Ideally you need two old cup-and-cone BB cups to screw into the BB shell so you can clamp it up in a vice to do the actual cold setting.  Try not to overshoot and have to bend the triangle back - do it in one direction only.

Never tell me the odds.

Re: Choosing a chainset
« Reply #18 on: September 13, 2018, 09:07:35 pm »
It's a JIS crankset according to all the info I can find online. I shall follow your recipe for setting the rear triangle. Will I need to consider setting to get the dropouts parallel as well, or are they likely to be close enough?

Re: Choosing a chainset
« Reply #19 on: September 14, 2018, 02:46:37 pm »
It's not critical unless you're running a hub gear (these don't cope well with any bending of the axle) but put the straight edge on them afterwards and check they're not obviously out of parallel with the top tube.  Chances are that they aren't right at the moment and you have a 50/50 chance of improving them just by resetting the rear end.
Never tell me the odds.

Re: Choosing a chainset
« Reply #20 on: September 15, 2018, 05:30:20 pm »
Sorted. :)
The OLN of the dropouts is now 120mm, the dropouts are now parallel, and it's basically straight (using the alignment tool it's 3mm different from right to left). I don't know why the chainline of the cranks is 45mm (not the 42mm the website claims), but the rear triangle is sorted and with the hub spaced to 45mm the chainline is great. The workshop I was in had all the frame alignment/bending tools too, so I got to learn how to use them. :)

Thanks for all your input - it's been most appreciated.  :thumbsup:

JonB

  • Granny Ring ... Yes Please!
Re: Choosing a chainset
« Reply #21 on: September 15, 2018, 10:04:01 pm »
Good to hear you're all sorted, well done

Re: Choosing a chainset
« Reply #22 on: September 16, 2018, 08:05:34 am »
Good.  For what it's worth, most manufacturers are vague or incorrect on chainline, since no-one really cares unless they're building a fixie/SS and, even then, few frames are straight enough that it Just Works.  You nearly always have to do some tuning of the components to the frame.  However, if the frame is out by more than a couple of mm and it's steel, rhat's the best place to start because it will also ride better afterwards.
Never tell me the odds.