Chainsets and Bottom Brackets?

[MacB]

Been doing my usual trying to understand what works with what and how it all hangs together and gotten confused. Even finding Sheldon Nrown hard to follow on this subject. anyone give me an idiots guide to:-

BB's - I understand the threading etc but what about the types, lime sealed cartridge, hollowtech, isis, square taper and so on? what are the pros and cons and, more importantly, are any heading for oblivion?

Chainsets - all the standard configs don't seem to match what I want, was looking at the Middleburn Duo RS7/8 options where I could make a compact double to suit my needs. They give ISI or square taper as an option but are only a 3 bolt fitting, so I would need to use Middleburn rings only?

 

[PpPete]

Hi Al
I think Shimano would like to consign Square Taper to oblivion....but IMO it has no significant disadvantage over other systems unless maybe you are looking at absolutely top-end performance ... and still widely available from other manufacturers.

Can you change the rings on the existing cranks? Wide range of Stronglight rings here for example.

Or this for a complete & customisable square taper chainset. Double check their recommended BB length though. I've known them to make mistakes.

I've heard bad things about the splined interfaces (ISIS & Octalink) but, touch wood, I've not had any probs so far with mine. Again as far as Shimano are concerned, this is history.

All the quality end components now seem to be outboard bearings...about which I nothing, other than I'll need yet another new tool if I'm ever to fit one

 

[andrew_s]

The spiders on Moddleburn RS7/RS8 are replaceable, so you should be able to get
chainsets in 5 bolt standard road, compact road, old MTB triple, compact MTB triple, 4-bolt MTB or whatever.

Splined BBs (Ocatlink, ISIS) and the various external cup BBs have a bit of a reputation for not lasting very long compared with the old square taper BBs (which are good for 20,000 miles or so, generally).

If I wanted a compact double, I'd probably be a cheapskate and get a Stronglight Impact. I've been using one for several years, and unlike RS7, XT or TA Zephyr, it's refained from breaking (so far).

 

[MartinC]

I think the way the market is moving is this:

Cup and cone BB's have almost disappeared and soon will even on the cheapest bikes.

The square taper cartridge will remain where cheapness and reliability count.

Octallink and ISIS are a failed experiment and will disappear (anyone remember Helicomatic hubs?).

Outboard BB's (Hollowtech II, Ultra Torque, etc.) are pretty much the de facto standard now for quality bikes and will stay for a while.

BB30 use will grow steadily and eventually replace outboard standard size BB's.

Someone will invent something else and we'll revise this list.

I could easily be wrong.

 

[MacB]

thanks guys, the Stronglight was one I looked at, it ticks all boxes just a concern over the BCD and available chain rings. I had been trying to create a compact double where i could have an outer in the low 40's and inner in the mid-high 20's. For example:-

Stronglight do the Oxale Two which is 94 BCD and comes as 44/29, married with a 12-26 9 speed cassette that gives me the road gearing I'd like. I can also create the same, or similar via the Middleburn ones.

The Stronglight Impact double has a BCD of 110 so my understanding is that you can't go smaller than a 34 inner ring.

What I want to achieve is a 9 speed compact double where I mainly use the big ring, all 9 gears available, and have the inner ring as an overdrive. I'm happy to stick with square taper and want longevity over weight savings.

 

[PpPete]

.. a 9 speed compact double where I mainly use the big ring, all 9 gears available,

that's going to be a bit of challenge on chainline isn't it?
I can see why you might want this kind of gearing...but easier & cheaper to put a bog standard MTB triple on?

 

[MacB]

that's going to be a bit of challenge on chainline isn't it?
I can see why you might want this kind of gearing...but easier & cheaper to put a bog standard MTB triple on?

I know Pete I'm just toying with ideas here, it's based on my existing road style triple of 30/42/52. I can reach all 9 gears from the 42 and just don't use the 52. I got thinking after reading the post from JohnyC here:-

http://www.cyclechat.co.uk/forums/showthread.php?t=29436&highlight=gears&page=7

I could almost do what I want with a single chainring but it would mean a wide range cassette. Certainly for the Karate Monkey build I'm looking at a single ring and 8/9 speed cassette.

 

[jay clock]

Firstly, I had an ISIS one on a new and very pricey Cannondale MTB and it creaked and clunked so badly I had to remove it within a very short time. ISIS get really bad reviews.

Stronglight Impact is an excellent chainset. I had a triple with something like 24 34 46 and it was perfect for touring. I would call Spa Cycles for a chat as they are the masters in this brand. I would avoid buying a Stronglight BB as it has a special tool (similar to a Campag cassette tool) and when mine went wrong when touring it was a massive pain

Finally if you do end up down the Hollowtech route, I think they are great. You may (or must) get the outsides of the BB housing "faced" (ie aligned 100% parallel with a special tool. But I am also happy with square tapers and they are easier to fiddle with on tour

 

[NickM]

Stronglight Impact is an excellent chainset. I had a triple with something like 24 34 46 and it was perfect for touring. I would call Spa Cycles for a chat as they are the masters in this brand. I would avoid buying a Stronglight BB as it has a special tool (similar to a Campag cassette tool) and when mine went wrong when touring it was a massive pain

Stronglight Impact chainsets are indeed very good, and as they are in fact Sugino XD cranks rebadged they are JIS taper and work perfectly with Shimano UN54 cartridge bottom brackets.

However, if you can't use the rings you want with them that's not much help. CTC types used to use the Stronglight 99 or 100 chainset (BCD 86mm, ISO taper) or good old TA Cyclotourist cranks (also Stronglight 49D) as a double with 45/28 (or, for ladies, 42/28) rings in the sort of setup you describe, MacB. eBay may be your friend...

 

[MacB]

Stronglight Impact chainsets are indeed very good, and as they are in fact Sugino XD cranks rebadged they are JIS taper and work perfectly with Shimano UN54 cartridge bottom brackets.

However, if you can't use the rings you want with them that's not much help. CTC types used to use the Stronglight 99 or 100 chainset (BCD 86mm, ISO taper) or good old TA Cyclotourist cranks (also Stronglight 49D) as a double with 45/28 (or, for ladies, 42/28) rings in the sort of setup you describe, MacB. eBay may be your friend...

thanks Nick, I seem to keep working out what I want and then finding that it was fashionable many years ago....maybe that should tell me something. There do seem to be some options around a BCD of 94mm which allows down to a 29t ring. Think I'll avoid the 86mm BCD as I don't want something I can't easily get parts for.

There does seem to be a fair demand for compact doubles in these ranges. The 94mm BCD ones I've found are aimed at other markets but often have comments along the lines of 'surprisingly popular with touring cyclists'.

 

[NickM]

Aha! These cranks fit the bill, if you can live with their dedicated chainrings.

Rather expensive - but perfection never comes cheap when you aren't the average sheep

 

[MacB]

Aha! These cranks fit the bill, if you can live with their dedicated chainrings.

Rather expensive - but perfection never comes cheap when you aren't the average sheep

Aha, now we're talking, glossing over the eye watering price tag for a moment, they look superb. The idea of a slotted, as opposed to drilled, outer ring seems childishly simple. Bloody clever some of these design types.

Now onto further info requests I've spoken to a couple of shops and they've been very non-comittal about which deraillers would work with the sort of setup I'm envisaging. I've also failed to get a decent idea of what will give the correct chainline etc. I was kind of thinking for this setup, with my intended use, I'd want the outer ring in line with the 4/5th cog of a 9 speed cassette.

I know I'm being a pest, one of these days I'm going to get round to collating all this stuff onto one spreadsheet for easy reference.

 

[NickM]

You could consider using 8 sprockets from a 9-speed cassette, losing the rarely-needed top sprocket and putting a spacer behind the cassette on the freehub body. An SLX cassette, for example, gives you (11)/12/13/14/16/18/21/24/28.

Assuming the standard double chainline (43.5mm), this will allow occasional use of the big ring with both the biggest and smallest sprockets without accelerated wear. The chain deflection will never be greater than that anticipated by a 9-speed setup (in which the big/big combination is avoided).

Ring choice (perhaps 44/26 or 46/28) might then depend on what tyre section you prefer.

Front derailleur: almost any should work happily (double chainsets are easy work for front mechs), but one designed for a compact double, with its smallish big ring, would probably be best. It will be positioned somewhat lower than the designer envisaged, which is good because it means that the chain is unlikely to drag on the bottom/back part of the derailleur cage when in the small ring.

 

[MacB]

Aha, makes sense, found a few more 94mm BCD sets, cheapest of which was £270 and FSA have a nice one at £460

I can just about get what I want with a cheapo Shimano MTB triple, 22/32/44 coupled with an 11-23 9 speed cassette, this is a 4 bolt 104mm BCD setup. But I'd effectively be riding in the 44 ring and have two inner rings as an overdrive. Whereas if I could set it up without the 22 ring and somehow move the 32/44 rings over, can you do that via axle length? Then 32/44 coupled with a 12-27 cassette would be fine. So that would be:-

Shimano FC M-442 square taper chainset - £40
12-27 cassette - £30

Much more palatable pricewise, and steel rings so hopefully a bit more durable as well.

 

[NickM]

...if I could set it up without the 22 ring and somehow move the 32/44 rings over, can you do that via axle length?

Yes - with the caveat that the right-side crank must clear the chainstay (but this is unlikely to be a problem).

Standard Shimano triple chainline = 43.5mm. You want to go inboard of that by half the width between two chainrings - needs measuring, but say 3mm.

MTB bottom brackets are symmetrical; I think that this includes current UN54 ones. So you would want a b/bracket (say) 6mm shorter than whatever comes as standard with the triple setup.