Custom Building a Modern Mountain Bike

This was a dream bike build for me and lots of readers share the dream, so here goes:

Build or buy?
Building means you specify all the components. Even $5K bikes often come with pretty lame wheels, crank sets, cassette etc and you will not get to choose tires, seat, shifters, calipers, bars etc. It was a no-brainier to build, and I am happier with this ~$2,500 build up than most (all!) $4K stock bikes. Why the cost difference? I could hunt down discounted parts. E.g. the shocks, wheels, and frame are not 2009 models.

If you are returning to mountain biking look in the ~$700 range for an off-the-shelf bike with front shocks and disc brakes, any less and you’ll not enjoy the sport. Getting semi-serious means $2K+ on a full suspension bike. Regulars I see again and again at local mountain bikes trails are mostly riding $2,000-$3,500 machines with maybe 10-20% spending even more. The sticker shock takes a few weeks to get over. If you do buy off-the-shelf look at the specs to see if any parts are ‘custom’. Custom generally means it is a non standard size, and replacement/ re-use on another bike will be hard or impossible. Another good reason to build. At the end of the day this sport is more about the rider, but go too cheap and parts will soon break costing you more in the long run.

Tools needed?
Quite lot of tools are needed, probably at least $400 worth. In rough priority order:
. Allen key set (~$10)
. Allen key sockets (~$15)
. Torque wrench (~$50)
. Cable/ Housing cutters (~$20)
. Bottom bracket tools (~$30)
. Cassette whip/ remover (~$20)
. Decent work stand (~$200)
. Headset press ($50->120)
. Crown race setter (I use a $3 tube from a DIY store)
. Star nut setter (~$10)
. Pipe cutter (~$20)
. Chain link splitter (~$10)
. White lithium grease (~$3)
. Several misc DIY tools you should already have

Where to start
Stripping and rebuilding your old bike is a great learning experience; it should you take a day or two. You’ll be annoyed how expensive new cables/ housings are, but will have a slicker bike at the end of it.  I bought an $89 Sette 16″ frame and rebuilt an old bike into one the correct size for my wife, it came in at ~22.5lbs which is amazing for an $89 frame and $300 shocks.

Hunting down the Dream Bike
Boy, this took me many hours online – scouring reviews, price trade-offs, forum postings etc. The most useful resource is the mtbr reviews forum – for each part I looked at the bad reviews, and also got a good idea of what everyone was buying for that component. This way I found some parts that I am really happy with, e.g. Odi Ruffian removable grips and the Thompson Elite seat post.

Search lots of bike sites as prices often differ widely, for each high value part use comparison shopping sites like Froogle – this found me XT cranks at over $100 off when everywhere else wanted MSRP.

Below I will try to discuss the trickier choices made; in general I tried to distinguish between parts I may upgrade and parts I should never need to replace on this bike. E.g. ‘cheap’ mechanical BB7 disc brakes vs. the Thompson seat post. In some areas you probably want to check out lower-end parts before splashing out, I put a Manitou R7 fork on my wife’s bike and rode it for a while before justifying $800 Fox forks.

Parts Arrive
This bike comprised of eight or nine boxes of parts from five different suppliers. As I said there can be HUGE price differences between retailers, so the extra shipping costs are more than worth it.

BMC Trailfox 2.0 Frame under wraps
This is a unsold 2007 found for $499, MSRP for a 2009 model is $2,149.

If this does not excite you then you are dead.

Avid BB7: My first disc brakes and they rock. No longer am I locking up/ skidding after being airborne + doing endos etc is very controllable. Be sure to use Avid speed dial levers so you can adjust the lever pressure required.
Fox Talas 140 RLC: When downhilling it is immediately obvious that these work better than my Manitou R7 MRD and I loved the Manitou. The 100-120-140 adjustability is great, I run 120mm for XC and 140mm for DH/ light FR. 100mm feels plain weird on the BMC frame so stays unused. With hindsight the 150mm Talas model would have been a better choice, but these things were expensive as-is. If buying a Fox fork be aware that adjustable compression is only on the RLC models and adds a lot more to the base price. Add the QR15 option and you are close to $1000 for shocks alone!
Thomson Elite Seat post: Brilliant! It has machined groves which stop the post slipping and must be about as light as the carbon EC70 post that slipped so often on my old bike.

Mavic Crossmax ST:Good wheels are must, try finding these stock on anything less than $5K. These can run tubeless tires but as with hydraulic brakes they seemed an unnecessary complexity I did not want to deal with. Perhaps a future upgrade?

The Build Begins

Rule one: never clamp anything but the seat post, tubing on modern higher-end frames can be crushed otherwise. Install the seat post and mount in your stand.
Rule two: Weigh everything before it goes on the bike. You will want this info when shopping for upgrades.

Pressing in a headset: This BMC came with one pre-pressed but this is the tool you should use – a headset press. Almost all headsets these days are threadless and press in, instead of screwing in like they used to. This is a much better system as a headsets coming loose was common in the 80s and 90s.

Attach the cassette– needs a lot of torque and the special tool is called a cassette remover. This is a 9 speed cassette I had laying around; it will be a PG990 soon.

Attaching brake discs to wheels– use a torque wrench if possible. These are my first disc brakes so BB7 mechanicals were ideal; $46 each for 2009 models is a bargain. Rotor size was copied from a Sepcialized Enduro at 203mmF, 185mmR. With hindsight this is total overkill and they will soon be swapped for 160mm front and rear. Unless you weigh 250lbs and shuttle ski runs I cannot see 160mms overheating.

Pressing the crown race into place. That is a $3 piece of plastic piping which almost everyone uses – no other special tools are required.

The other headset parts. This can be confusing for a beginner so make you download the relevant pdf. These are sealed bearings; don’t bother saving a few pennies on the old bearings-in-a-cage variety. Note: I missed the compression ring form this photo.

Mounting the wheels getting ready to size the steerer; use something to prop it up. Put the headset parts, stem and spacers (max 30mm) in place.  Measure twice, cut once. Do not cut a steerer too short as the repair will be expensive.

Cutting the steerer– the pipe cutter is just a plumber’s tool. Debur using the tool’s deburrer and then smooth off with a metal file.

A star nut setter: Star fangled nuts are easy to bash it in with a hammer and I have done that before, but not on an $800 fork. The setter tool is only ~$10 so why not use one?

Depth of start nut varies on who you ask, from 4mm to 20mm. I set this one to 10mm. It should not matter since the star nut is only used to preload the headset bearings, the stem bolt holds things together.

Leave a gap from the top of the spacer to the stem since you are going to preload the bearings in a minute. The star nut bolt does not need to be very tight, just enough to stop play in the headset. I put the bike on the floor and tighten the steerer nut until steering becomes tight, then back off a little. At this point you should tighten the stem bolts.

Disc brakes and Hollowtech cranks are next. Both being new to me it is time for lunch.  There is no point rushing and I want a clear head especially for that expensive crankset.

Putting a caliper in place– very simple but you will need a mounting bracket that matches your frame and the rotor size. There are three different standards out there so do some homework on this or expect a trip to the local bike shop to find the correct mounting hardware. Avid brakes come with a cool auto-alignment system (CPS) that works much like the curved washers from v-brakes. This mitigates having to face brake mounts.

Hollowtech cranks: The scariest component. MSRP is $305 but all affordable cranksets seemed to have bad reviews. Hollowtech means outboard sealed bearings and very few parts + look bulletproof. The black spacers are for use with a 68mm shell like I had – another plus, this a one-size-fits-all deal.

Of course they needed a new tool. A torque wrench cannot be used with this tool so I used the torque wrench on my car’s wheel nuts to verify what 50Nm feels like. You do not want to strip BB threads!

This side requires very little torque and simply preloads the bearings. Tightening the crank on is done with two allen bolts at 90 degrees to the crank – they come with a stack of warnings so I doubt you’ll get it wrong.

Derailleur Alignment Tool: I am not sure how accurate the tool is, but all three bikes I used it on had misaligned hangers. Misaligned in different ways so I assume the tool is correct. Use the tool to check Up, Down, Left and Right – lightly bending the hanger until it is within 4mm on any measurement. I have to say that my shifts are pretty smooth and maybe this helped?

The spoils of XTR components. The front mech comes with a helpful guide to set the correct distance from the chainrings. If you are buying XTR you can probably eyeball this measurement.

New SRAM chain. Note the removable link which means the chain can easily be removed in the future. The other tool is a chain link splitter which is only needed to remove links from the chain if it is too large.

Put the chain around both large cogs and allow for two extra links. I have ran with zero links before and had no issues – actually I might do the same on this bike to reduce chainslap on rutted downhills. With a tight chain running the extremes of gear combinations is the only issue, but that is a no-no anyway.

It is looking like a real bike now.

Cables: … ugh, not hard but it takes a while. You must use a specific cable cutter or expect frayed cables. Housing and cables are different for both brakes and gears, also these days we run continuous housing from the levers to brakes – use tiny zip ties or special clips to attach the brake housing to the frame. Zip ties are my preference.

Initially I am using an old set of bars/ levers but wanted to dump the old grips. Push a WD40 tube as far as you can, spray in oil and twist. These came off totally intact with little bother.

I had never used these bars and they were incredibly wide. It was cool to see preset cut-down points. Again a few twists of a plumbers pipe cutter and deburring is all that is required.

Removable grips: What an awesome idea for people that love swapping out components. My hands grip really, really well with these – possibly the best part on the whole bike!

Six hours later it is complete (cables were tuned the next morning). It came in at 27lbs 8oz which for a ~$2,500 5″ travel all mountain bike is not bad at all. It should drop about a pound when replacing the old bars, shifters and oversized brake discs. Those tires are 2.6lbs too, yeah, yeah weight weenie.

The Results?

Time and money very well spent. The brakes in particular are changing my riding style, locking up is now almost a thing of the past, especially when scrubbing off speed after time in the air – especially when a corner is almost immediately after landing. Having full suspension makes rides so much less fatiguing and landing misjudged takeoffs much safer.

For a brand that is almost unknown in the US it attracts a lot of attention and questions – everyone so far seems to approve.

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22 Responses to Custom Building a Modern Mountain Bike

  1. Phil Ammann says:

    Looks like a magazine article for DIY!

  2. Paul Lockwood says:

    Thanks Phil, I have been reading Popular Mechanics lately so maybe it rubbed off.. next blog post: build a Submarine out of a Chevy Nova..

  3. Atosark says:

    I wonder with what nuts you downhill with this fork, shock and tires, but ok 🙂
    Nice XC/AM construction though.

  4. Paul Lockwood says:

    DH is all relative right.. what seems crazy here in Atlanta is probably a walk in the park for someone who regularly shuttles at whistler

  5. Atosark says:

    For AM/XC I’d rather go for Continental Vertical ProTection 2.35 rear and either Kenda Nevegal 2.35 front or Continental Explorer 2.1/2.35 front.
    Also for breaks, get AVID Juicy7 with ~180 front and ~160 rear. They are definitely worth it.
    The fork is ok. But why SRAM chain with Shimano mechs? Either get Shimano mechs+chain+cassette+controls combo, or jump for SRAM.

  6. Paul Lockwood says:

    Thanks for the tire tips, when swap-out time comes I intended to try something else.

    One tricky thing writing posts is how much detail to include – this was write-up aimed at non-cyclists mainly. This build was a starting point re-using many components from old bikes, since last August I’ve spent over $6K on the hobby so took it ‘slowly’ 🙂 It should be just wear items for the next two or three years, I hope!

    The BMC now has SRAM x.9 rear mech + triggers, PG990 cassette and PC971 chain. I kept the XTR front mech as it works well. With new bars too weight now ~26.25 lbs – not bad for an AM setup.

    Discs are now 160mm back and front – that shaved about half a pound from the rig 🙂 One day I’ll try hydraulics but love the BB7s and recently put them on my hardtail too

  7. Luis says:

    Hi Paul,

    Excellent blog post! Very informative.
    What saddle did you go with? Have you made the change to tubeless tires?

    Take care,

  8. Paul Lockwood says:

    Thanks Luis. Saddle-wise I ended up using an old (1999-ish) Selle Flite from my road bike and like it. It’s pretty light and comfy enough for me

    Tubeless? Maybe one day, I slashed a tire landing on rocks one ride + bought some Nevegal tires. Those tires have been so good I don’t want to change them

  9. Rob B says:

    The BB7s are perhaps the biggest short coming on what is a nice rig. Though you like them for now, if you tried some Magura Marta Sls, Formula R1s or 2011 XTRs you wouldn’t look back. Tubeless without tubelss specific tires is the way to go. The extra time setting up off the trail benefits greatly on the trail. Still nice build all up.

  10. Paul Lockwood says:

    Agreed Rob. I’ve tried good hydraulic setups on friends’ bikes and the feel is great. Right now I am nursing knee overuse issue but when fit will look at tires and brakes

    Since getting back into mountain biking I’ve learned a lot from others but still like this BMC rig. With hindsight I’ll possibly go for a fixed 120m fork to save weight. Saying that I did more FR stuff when starting out and needed the extra travel back then. As time progressed I dropped the FR and ended up being a fairly aggressive trail rider. Not sure a 100mm fork would be happy about some of the rougher lines I’ve learned the bike can handle on our local trails

  11. Tom Pantz says:

    Hi Paul,
    I bought used Rocky Mountain Fusion hardtail from a pawn shop for $50 (it’s old like 1999) and I’ve suddenly found myself taking it apart and upgrading the parts with new shifters, cassette, cables and grips. I’m a complete utter newbie but I’m discovering working on the bike is very therapeutic. Now that I found your excellent article my eyes have been opened where I’ll be throwing my savings next. Where do you recommend finding good frames? Ebay? Should I search online anywhere in particular?

  12. Paul Lockwood says:

    Tom, you should ask the question on here

  13. RobM says:

    Wow, what a great post. What stuck out to me was that there really wasn’t that many specialist tools needed. I could even borrow a few of some mates. Makes me want to build my own bike up.

  14. Tim says:

    Nice bike, after a long break from mtb (early 90s) I’m getting back in. I can’t see any value in my bikes from then so I’m thinking new carbon hardtail 29er built from parts. Some good info on your page as a bit has changed. p.s. BMC well known here after Cadel won TDF 2011.

  15. Steve says:

    Hey Paul,

    As I’m considering “building” my own custom mtb in the near future, I enjoyed reading your post about creating this awesome BMC (can’t believe you got the frame for that much!!). I’m ok with the technical side of things but I’m new to purchasing parts online, i.e. what suppliers to use, especially for international shipping since I live in Hong Kong. What suppliers did you find most useful? Hopefully they do international orders.

    Also, have you come across any other blogs written by likeminded people who have custom built their own bikes?



  16. Pat says:

    Where did you get that frame? That’s a damn good deal!

  17. Scott says:

    So very appreciative of this post. I have been out of MB for the last 20yrs. 😦 Looking to get back and have been looking for a bike. Thought I might look at building my own, (nvr done that). Googled the idea, found your post, and it is inspiring and gives me the extra nudge I needed to go forward. Was unsure of the complexity. Your post let’s me know that with my careful planning and patience, I can do this. Thanks!!


  18. Ian Burnett says:

    Great piece of writing. Helped me with my first build this last weekend – a swop over from an undersized frame to one purchased in my size. I now have a very nice winter hard tail to compliment my full susser.

  19. Ryan says:

    I’m very new to cycling but am looking to build a hybrid of sorts. The goal is to have a cruiser frame with mountain bike components. Much like a Retrotec MTB, but I’m just not knowledgable enough on the subject to know if i could even do it myself. Any comments or tips for a n00b? lol

  20. Anonymous says:

    what other frames can go with this build

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