Hi there

I am happy to advise that, not only have I just joined your forum but I have just purchased a second hand Spot Brand Frame, and now have the task of building a complete bike. It is a John Deery Single Speed frame and I have decided to build it from the bottom up. So my first set of questions centre around the Bottom Bracket:

What type of BB should I buy, I have read about eccentric?

What measurements do you recommend (it is 68mm on the frame) and manufacturer, although I am on a tight budget.

What advise do you have for the crank set?

Any help would be beneficial as I am just searching the net at the moment. If anyone can reccommend any guides, on line or books, that would be really beneficial. I am based in the UK, not that it should matter :-)

- Singlespeed Smee, single on the road and soon to be off.... 

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Single Speed on the road, soon to be off.

before you get a BB you should choose a crank.  That will determine what BB you need, type and size.  Is your bike 68 or 73 mm bb shell?  Do you want a light weight racer, count every gram type thing or reasonable weight, built to last forever bike.  Or do you want strength to be the first priority?  Do you like new and trendy or cool retro?  Is the frame SS capable or will you need to use a tensioner/eccentric BB/ rear hub?  As for a start, its hard to go wrong with a good old pair of Race face turbines (square taper will even be ok fo XC purposes) or XTR cranks.  Both are light and stiff enough when you will be grunting up a hill at full torque load.  As far as new products go, the sky is the limit.  Nearly anything will do the job.

Thanks for that, good questions (points I missed out).

It is 68 BB shell.

It has horizontal dropouts so no need for a tensioner, I think?

I want to do XC stuff, so looking for strength first then weight. Sorry, what is a square taper is that the join from the BB to the crank?

I will look up Race Face.

If I buy the crank, should I get a crank set? what is the best teeth recommendation (64 million dollar question I know), all XC events I attend are hills, and more hills so easy to start with then I can change the rear sprocket as I go.

I appreciate any help.
 

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Single Speed on the road, soon to be off.

For new cranks there are a few cheap yet very usable sets from truvative.  Square taper is the older style of crank/bb interface.  New stuff will generally either be shimano octalink or ISIS drive.  Either will work fine.  I prefer ISIS as there are more crank options for my tastes.  (I prefer strength to weight up to a reasonable point).   Race face has a few off shore built sets for some good prices these days.  Some of the newer higher end stuff will have the BB included as part of the crank.  If your drops are horizantal, you will not need any sort of fancy "turn your old bike into a SS" gizmo.  Congradulations! You have a real SS bike!

 

Oh yeah, 32t seems to be the norm up front, 16 or easier (rear) if you ride lots of hill.   I run 28/15.  Plenty of hills where i'm at, and I keep up with fthe geared folk

Cheers for the info, already looking on the internet. I didn't realise that Amazon sold bike bits, they stock Truvative but not Race face. Seeing as my budget is limited I think I might go for the Truvative. Looks like it is quite a bit more expensive on this side of the pond.

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Single Speed on the road, soon to be off.

As someone already mentioned, the horizontal dropouts are key and will save you some problem solving for chain tensioning. I'd never go back to a tensioner except for maybe an eccentric hub, but only if I really had to.

I have some old square taper LX cranks on my bike that seem to be fine. I like being able to have room for multiple rings so I can put a bash guard on. I like the bash guard and mine has some good dings in it. If you think about it, it's more important on a SS because if you smash your ring, you don't have the option of just shifting to another.  

 

thanks for the info, if you are interested I have uploaded some quick photos of my frame. I will try to upload photos as progress is made, if you are interested (sure to be asking you more questions :-) ).

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Single Speed on the road, soon to be off.

"I am happy to advise that, not only have I just joined your forum but I have just purchased a second hand Spot Brand Frame, and now have the task of building a complete bike."

Hi.

 I advise trundling over to ebay.co.uk and checking out charlie the bike monger http://stores.ebay.co.uk/Charlie-The-Bikemonger . he is a singlespeed specialist, and has loads of useful stuff. like half links, chaintugs and decent chainrings. Plus when you buy stuff there's always a sweety stuck in the packet with the goods

 

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"Get a bicycle. You will not regret it. If you live." Mark Twain.


The follower of singlespeeding
is at one with his bike.

Welcome Smee, and hello again Adam. We're all 'Englishers', which is great! The British are coming!!!

If your terrain is moderate (like anwhere within riding distance of anywhere that can be termed 'London'), I'd go for a slightly higher gear - like, say 55" - that's 34x16 or 32x15. This will get you up short, steep hills, but still allow spinning along at 18 or 19mph when necessary - and general cruising at a comfortable 13-16mph. As you are new to this do take Adam's advice and look at Charlie The Bikemonger. He's a great chap from Swanage, and has a site with loads of SS info and useful stuff for sale. When I bought my White Industries freewheel, he incvluded a lolipop - just like Adam said! Then you'll need to slope off to www.sheldonbrown.com. Sheldon is THE MAN for really practical information on everything bicycle. gearing, chainline, chains, conversions, building bikes from 'junk', parts compatibility, etc. I worship Sheldon.

Crank and BB choice is the most difficult aspect of speccing a SS mtb. Let me attempt to explain. There are a couple of limiting factors to be aware of: 1- Will the inside ends of the cranks clear the chainstays? 2- Will the chainring (or RH crank 'spider') clear the RH chainstay? 3- Will the chainring line up exactly with the rear sprocket to give perfect, straight chainline? If you are converting a standard cassette hub, by fitting a single sprocket and spacers, you can forget point 3, as you can move the sprocket in or out by re-arranging spacers. Point 2 also has some flexibility, as you can fit the chainring on either the outside (big ring position) or inside (middle ring position) of the RH crank's spider. Regarding point 1, you must have an absolute minimum of 4mm clearance between the back of the crank arm (by the pedal thread) and chainstay of the frame. When you ride hard the whole bike flexes. Less than 4mm and you risk the back of the crank bashing the frame - not good! Chainstay clearance has a great deal to do with the frame design. 'Snake' stays are great, allowing much more room to use a narrow BB, bring the cranks inboard, and reduce that Q-factor. Straight stays might necessitate a wider BB to give the necessary clearance. I've got a Kona Unit and I've fitted road cranks with a 39 ring (for 19 sprocket giving 55" gear). The Kona has 'snake' stays and all is fine. I also have a Genesis with straight stays. The Genesis needs a much wider set-up so that the cranks clear the frame.

Q-factor (see Sheldon Brown for more) is the effective distance between the two pedal paces of the cranks, measured across the bike - in other words, how close your feet are together as you pedal. Obviously it's not good to have your feet miles apart - like John Wayne after climbing off his horse! So, Q-factor should be kept as small as possible, bearing in mind all the limiting factors mentioned. One of the (many) advantages of SS is that Q-factor can potentially (if the frame's designed right) be greatly reduced in comparison to a triple-ringed bike.

Confused? I would be! Where do you start then? I would find a BB and crank combination that gives the necessary clearance between cranks and frame, then fit the chainring and make sure that clears the frame, then position the rear sprocket on the cassette body to get perfect chainline, so that the chainring and sproket are dead in line (same distance from centre-line of bike). If you go to a bike shop they may have some old scrap cassettes. You can take these apart to get the spacers out. Lots of small spacers allow fine tuning of the rear sprocket position. If you buy a converter kit there are usually only two big spacers. This does not allow fine-tuning the position. If you can't get old cassette spacer, Charlie does a spacer kit that is similar. I think they cost about £11.

Regarding crank/BB interface types, square taper is the 'done thing' for SS. Modern systems do not have the flexibility of the old-fashioned alternative. This is beacaue square taper BB axles are available in widths from 102 - 130+mm, thus giving mega 'tunability' when setting Q-factor and clearance. Most modern alternative systems have either a fixed width, or just a couple of width options.

The drive train is the only tricky bit. The rest of the bike should be easy peezy!!!

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STEAL WON!

That reply from Devoid ought to be a sticky top post for useful advice!

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"Get a bicycle. You will not regret it. If you live." Mark Twain.


The follower of singlespeeding
is at one with his bike.

There'll be a book one day!

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STEAL WON!

Deviod_punk, you have blown my brain, it has become this watery substance..... :-) Your advise is excellent, I shall of course spend more time looking it up on the net :-)

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Single Speed on the road, soon to be off.

Hey Smee, I'm always happy to help. When I said 4mm between cranks and stays - that's an absolute minimum, OK? It should be 10mm+ if everything works out properly.

It'll all become crystal clear as you put the thing together. The real issue to bear in mind is the fact that the SS MTB does not (necessarily have to) follow industry norms.

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STEAL WON!

Greetings,

Quality and tight budget do not mix well. I wish it did, alas you'll end up paying more in the long run. Eccentric or not, get a Phil Wood BB set-up. Great product, great support.

Cheers,

-BC-

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-BC-

most of my single speeds have been built from the spares box

simple spacers and split cassette back end washers on the front chainring get the chain straight tho i run 32/18 cos its a bit hilly

but also run 32/16 on my more road biast bike

bit of 5mm ali plate and a roller ,short mech bolt from a tourny mech and thats it

using a roller on the tensioner works better than a jockey pulley

used mostly gt frames (cos they're cheap strong light and handle well)

you may also find a larger frame is needed ,i genarally run an 18" frame but feel comfy on a 19/20" frame for a single speed

 fit o/s bars stem cheap spinner rigid forks and have a laugh

remember single speed rigids only loose out on the climbs and the flats and the down hills

and you will seriosly think about throwing away all the gears on your other bikes

 

part of the fun, is learning how many ways you can use old junk

 

i always know i can build some wierd kind of thing from my junk

 

My Urban Assault Vehicle (UAV) is designed to hoon around the city i live in. it's not for speed, it for stairs, seats, walls, carparks, malls and more

its an old non disc alloy GT frame with a disc adapter. neoprene RST spenders with air assist, half good wheels; strong but a bit heavy. Mind you, the 2.3" road slicks make it look horny from most angles

the big tyres give awesome cornering ability in towns and cities too 

paint is a textured metallic copper bronze, brass that actually looks like some kind of lumpy mud; instant mtb cred even with the slicks!

gotta have a disc brake on the front to do good stoppies; the old hayes brakes came off 4 other bikes before this one

 

this is the kind of bike i like to take overseas, a good solid fun tool that is unlikely to let me down and if it does i can improvise something from the locals

of course i've crashed many times but hey, as long as you can get up and take a bow it's all good

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Make mine from Ti please