Converting an MTB to single speed

seamus

Going to buy a new bottom bracket for my road bike over the weekend I had an epiphany. Commuting on a half-decent road bike is expensive. It needs more maintenance, more parts needs replacing, and my 18 month old Trek is looking very sorry indeed, not least after having 3 or 4 pretty hard falls, all while commuting.
My main criteria for a bottom bracket was that it was cheap - Tiagra or less - because I know I'll be replacing it again in 9 months time. I also saw shards of glass and slices in my 4 week old tyres. It's a just a complete feckin pain when it's supposed to be my "good bike", but new parts look old in a matter of weeks, and I'm scrimping on costs because of the frequency of replacement.

So I remembered my old MTB that I built from scratch 15 years ago, is sitting in my brother's house. And I like the idea of a singlespeed, less maintenance, hack bike that I'm not too concerned about, and with parts that I won't shed a tear about it they hit the deck or get covered in salty grime from the roads.

So I'm really looking for tips on the best way to go about it. My plan is to do it on a phased basis, so I can get the bike working as my commuter in the short term, but do the switchover in a matter of 6 months or so. I'll get pics up when I manage to go collect the bike.

It's a solid Reynolds 531 frame, fairly standard MTB of its time - vertical dropouts, 1" headtube. My plan is first off to put a singlespeed conversion kit on the rear. It's an old XT 8 speed rear hub, the wheels should still be fairly solid on it.

Then I'll change the crankset. Singlespeed cranksets seem expensive enough. Would I be better off putting on a triple or double crankset and removing the other rings, or is there a way of fitting a BMX crankset to an MTB frame? (I know the BB sizes are way different).

Then the frontend. At present it has a very old pair of Marzocchi suspension forks on it. The upside of these is that they have a replaceable steerer tube. The downside is that I imagine Marzocchi has long since stopped making them. Plus the legs are magnesium and flex so much while standing that the tyre rubs off the fork legs. I'll have to convert the whole front end to aheadset, so I'm thinking carbon or chromo forks and standard drops, caliper on the front and cantilever on the rear. Or perhaps a short-travel pair of shocks, if the price is right (or would that look ridiculous?).

Long-term then I'll probably replace the wheels with a flip-flop hub at the back, and maybe (maybe) get the frame stripped down and repainted, but I don't think that's necessary.

Any tips/pitfalls, etc?

gman2k

I'd get rid of the front suspension altogether and go rigid.
It's unnecessary weight and there is nothing to be gained from it for commuting.
You may need a chain tensioner as the mtb has vertical dropouts.
Otherwise, run with the conversion kit and don't bother with flip flops!
Finally, you should probably ditch the front chainset (Prob a triple) and get a single ring upfront. Lose the front mech and shifters also!

If your are stuck for a single ring crank, gimme a shout - I have a new cheapo 'Mighty' single speed lying around somewhere - you can have it for what I paid for it! (Or do an Ebay search for it)

Morgan

In these difficult economic times could you not use the existing chainset?

Some useful info here:
http://www.mtbr.com/ssfaqcrx.aspx

TinyExplosions

You could pick up a crank for 80 quid from On Track (they're Brick Lane Bikes ones, and look good as well as being decent quality), and you'll need a BB (about 12 quid)

Other than that, the conversion kit would work fine and you'd be up and running.

The only unknown is that it doesn't say on CRC what width the sprocket is. If it's 1/8" (standard for single speeds) you could use the existing triple crankset, but the chain would be a little loose at the front and may make some noise (never mind the headache of chainline and the size of the chainring)

Your best bet is to get a cheap track crank!

Morgan

TinyExplosions wrote: »

You could pick up a crank for 80 quid from On Track (they're Brick Lane Bikes ones, and look good as well as being decent quality), and you'll need a BB (about 12 quid)

Other than that, the conversion kit would work fine and you'd be up and running.

The only unknown is that it doesn't say on CRC what width the sprocket is. If it's 1/8" (standard for single speeds) you could use the existing triple crankset, but the chain would be a little loose at the front and may make some noise (never mind the headache of chainline and the size of the chainring)

Your best bet is to get a cheap track crank!

The DMR sprocket will be 3/32".

You could run into clearance issues if you attempt to use a track chainset on a mtb frame - you might need a longer BB to accommodate it. I'd use a standard mtb chainset and fit a 42 or 44 unramped ring in the outer position.

seamus

gman2k wrote: »

If your are stuck for a single ring crank, gimme a shout - I have a new cheapo 'Mighty' single speed lying around somewhere - you can have it for what I paid for it! (Or do an Ebay search for it)

I found a link to one of these yesterday which I've lost now. Something ridiculous like €15 new. Maybe a bit too cheap, but I do have a new square taper BB at home that I otherwise have no use for, so no harm to use it to get up and running and I can swap it out for a proper one when the BB dies.

Morgan wrote: »

In these difficult economic times could you not use the existing chainset?

I definitely could, and that's my plan initially. But I know the existing chainset has been removed and reattached so many times that the hole is now warped and they creak like a bastard, so they'll need to replaced soon enough.

TinyExplosions wrote: »

The only unknown is that it doesn't say on CRC what width the sprocket is. If it's 1/8" (standard for single speeds) you could use the existing triple crankset, but the chain would be a little loose at the front and may make some noise (never mind the headache of chainline and the size of the chainring)

Yeah, I was thinking that. Standard BMX chain will work, right? Just that standard MTB rings are much thinner than the chain?

Thanks for the help guys, all links and tips are appreciated!

Holyboy

Sturmey archer make a nice cheap single chainset its 4 bolt 104 bcd and has a double chain guard to keep your trousers clean:)think it retails about 35 but im sure you could pick it up cheaper online.

021CRETE01

Hi Seamus,
Just read your conversion plan and wondered how you got on?

Lumen

seamus wrote: »

Long-term then I'll probably replace the wheels with a flip-flop hub at the back

According to the maths, a 700c/29er wheel with skinny road tyre has just about the same rolling circumference as a 26" wheel with a fat MTB tyre.

I did some reading around recently as part of research for a similar* project and there are a few people running 26" MTBs with 29er wheels on them in this configuration - there should be enough frame clearance.

* similar but stupid

4li5t4ir

I've got a commute on a bodge job fixed gear that I made out of an abandoned Raleigh lady's bicycle. It's nice to commute on a heap of junk (that works perfectly) as you don't have to worry about it getting robbed or wreaked. I tried to put a single speed crankset on it but it hit the chainstay, so I used the double crankset that came with it. I didn't even remove the second ring. You can use 9 speed chains on a single speed, they are defiantly strong enough, but if you want 1/8" chain it will run just fine on multi speed cogs and chainrings you just can't use 1/8" cogs/chainring with a 9 speed chain. As for the vertical drops you should really get a tensioner if you can't find the "magic gear", or an even cheaper option would be to use a floating chainring. I've always wanted to see one work in real life.

seamus

Haven't actually started yet :pac:

The good weather has made me happier about commuting on the road bike. Also was waiting for finances to get a little better. I'm going to pick the bike up today and see exactly what needs to be done. I suspect the hardest part is going to be finding and fitting a 1" rigid MTB fork with an AHead steerer tube.

Interesting to know about the wheels, Lumen. My problem though is if I want to use V-Brakes, I'll need to stick with MTB wheels cos that's where the canti mounts are.

021CRETE01

Hi Seamus,
Yes, Lumen is right about the road wheels fitting the MTB frame.I just measured my own bikes.I have an alloy frame approx 3.20lbs with PACE RC31 fully carbon rigid forks 735grms (Disc specific).The frame is v-brake compatible but I ran it with disc brakes using an adaptor.My frame (KLEIN Attitude Race) without fork is on E-Bay at present.If you have too much trouble with the 531 and 1" fork issue, and if you have to resort to purchase,please give me a shout.I also have a choice of flat bars and stem lengths + saddle.I would do a good deal.Besides all that ,"Good Luck" with your project anyway.
021CRETE01

Lumen

021CRETE01 wrote: »

Lumen is right about the road wheels fitting the MTB frame.

Just to be clear, I'm only saying that there is probably sufficient frame clearance. Frame spacing is another issue.

seamus

OK. Overall, needs an overhaul, like I thought. Surprisingly though the core parts seem OK despite having not been touched for ten years. New cables, new tyres and a lick of oil and it would actually work just fine.

Suspension forks are fairly screwed, they'd need a complete strip down. I don't have the expertise for that, and I doubt the parts are available any more.

I'll have to wait until I've stripped it completely before I know what the frame is totally like. First order of business is to remove the old MBUK stickers all over it. The only bit of rusting appears to be on a cable stop for cantilevers. I might just dremel that off completely. The paint on the frame appears to be a very thick lacquer, maybe 1.5mm of it. Still debating if I should go ahead and get it repainted completely. Is that expensive?

Surprised by the wheels. They're a little out of true, but the rims seem fairly unworn and the hub and freewheels bearings feel fine. Strip them down, service the hubs and true the wheels, and they'll do fine for a while. They're 15 years old, but I think they've seen less mileage than I've done on my road bike in the last 12 months.

Time to start doing some pricing. Everything except the wheels and maybe the seatpost will need to be replaced. Definitely looks like the 1 inch ahead forks are going to be the hard part. I'll need to ring around some LBSes.

gman2k

Nice bike Seamus, looks like the chain is junk though, better to cut it off and fit a new one.
You also might find some corrosion on the wheels where different metals are meeting.
You could just fit a rigid fork, if you are going the single speed route there is no need for a heavy front end!

seamus

Got down over the weekend to strip this down...mostly. The stem bolt is round and seized, so it's not coming off. I managed to remove the fork, thanks to the changeable steerer, but I couldn't get a hacksaw in to fully remove the crown race, which would let me remove the steerer vertically. So I'll need to get the dremel down to it. Thankfully the steerer appears to be alu, so it'll cut like butter.

Frame is solid, no dents or cracks, but the paint job is screwed, pitted, scratched and dirty. Really couldn't be bothered repainting it myself; I've stripped the paint off a bike before, it's labourious, boring and dirty. So I've fired off an email to a crowd in Ballymount to see what it would cost to strip and repaint it.

I have less that I can salvage than I thought; wheels, frame and BB are the only things that seem worth saving.

As predicted, sourcing forks seems to be the hard part. Rothar, my main hope, don't have any.
They're not cheap either:
http://www.carboncycles.cc/?s=0&t=2&c=82&p=887&
http://www.bike24.net/p214017.html

I like that both give me the option for a disc in future, but my gut tells me that the square, "rigid suspension" style of of the Carboncycles forks will look ridiculous with drop bars and 32mm tyres.

Aiming for October/November delivery of this, keeping money and weather in mind!

seamus

€90 for a repaint. Decisions, decisions.

seamus

Finally got it completely stripped down, had to get a dremel at it and basically cut off the headset. Peeled off the stickers too after taking the below image.

Anyway, the paint has come away in plenty of places, as can be seen below, so I have no choice but to get it resprayed. €90 is the cheapest quote I've gotten. But I've looked at the option of doing it myself and I'll easily spend €50 on gear and paint before I even start. Then there's the painful process of removing the old paint and the inevitable mess I'll make of spraying it. So I've come around to thinking €90 is a small price to pay to get it done right.

Also placed an order for the first few bits today....

SomeFool

Working on a similar project myself Seamus - what chainset did you decide to go for, it's the only job I've left and am a bit unsure of what to get!

seamus

Went with this in the end:
http://www.chainreactioncycles.com/Models.aspx?ModelID=65427

Mainly cos it's cheap and it goes with the all-black theme I'm going for. I'm concerned that I'll need a longer BB axle, but I won't know till I get it.

seamus

Right, everything's in!

Got the frame resprayed last week at Tallaght Powder Coat. €90 for a gloss black finish, came out very well.

Got Kona P2 rigid forks from bikeman.com for a very reasonable price.

The bars I got are a little narrower than on my Trek (38cm -v- 44cm). I didn't think it would be a huge difference, but looking at them now they're tiny. I'll give them a whirl and if they feel uncomfortable I'll get something wider.

Black is definitely the theme. Everything's black. Except the wheels.

The only thing I've overlooked is that there's no fine adjustment on the brakes or brake levers. So I'll need to get my hands on some in-line adjusters, which I've heard work fine. Hopefully someone in Dublin stocks them. I might drop by thinkbike this evening.

I'll start the build on Saturday, but I want to do it neatly and carefully so it could take the whole day. I also need to service the wheels, so that takes time. I'll take pics as I go along.

Final bill is €460 including the respray and shipping of parts, and I haven't really skimped on parts, just been frugal

SomeFool

seamus wrote: »

Right, everything's in!

I'm the same, just waiting on a tensioner to arrive from chainreaction. Stick up a pic when you're done!

seamus

Done!

Well, not entirely. Got the last pieces today - some 1" headset spacers that I couldn't source anywhere in Dublin, so had to buy online. Fitted the headset, and promptly broke the plastic top cap. So now I've to wait on a replacement aluminium top cap. Still though, done

Haven't decided whether to switch the battered old pedals from my road bike onto it or buy new ones. They're cheap enough. I also originally had a setback seatpost, which I think looked a whole lot better, but idiot here bought one that was 0.4mm too wide. It's a recurring problem with me, I think my next major purchase should be a set of vernier calipers. So I might invest in a setback seatpost in the future. Note that the saddle is probably way too high, I haven't had a chance to fit the bike properly yet

I'll need a back wheel soon enough. The current one has a properly warped rim, I've gotten it to within 2/3mm of straightness so it'll do for the time being.

I'm almost loath to bring it outside and let it get dirty