Got a bike question?

Well, do ya? I'm a bike mechanic so I figured, why not ask?

Anything from repairs to storage to efficiency, I will do my best to respond.

We've been wanting bikes again...is there anything you would recommend for mostly gravel/dirt roads with some pretty steep hills for under $200? Thanks.

Hi Judith.

Well, for the type of terrain you are describing I would definitely recommend a bike with low gears and relatively fat tires.
Low gears:
A large number of teeth on the rear cassette (the gears attached to your rear wheel) combined with a small number of teeth on your chain rings (the gears attached to your crank arm/pedal) will work together to let you do less work... kinda. You actually do the same amount of work but over a longer period of time. It's the difference between trying to sprint up a hill or walking; both move you to the top of the hill, but I think most would agree that walking is easier.
Most mountain bikes of the last 10 years or more will have 18 to 21 "speeds". This means that there are 21 different combinations of cassette gears and chainrings that you can shift between. This is slightly off topic, but be aware that a number of these combos are actually so similar as to not feel any different to the rider. If you are interested in this kind of stuff we can have a discussion about gear ratios and a user-error phenomenon called "cross-chaining".
The up shot of this is that bikes designed for going up hills (ie: mountain bikes) are going to be geared lower to facilitate you getting up those uphill sections of your ride!

Fat tires:
On gravel or loose surfaces you are going to want the extra traction and the extra comfort that a wider tire provides. Again, Mountain bikes usually come standard with a 2.1" wide tire. Unless you are riding on loose sand or snow, this will be wide enough for you. The number one thing with tires is: KEEP THE AIR PRESSURE HIGH. Most people run their tires well below the proper pressure and this can make you work much, much harder. Up to 1/3 harder... thats 33.333%. On the side on every bike tire is a minimum and maximum pressure in PSI (pounds per square inch). Keep it at the max. You will get fewer flats, work less hard (or go faster!) and have better control. You will need to pump up your tire weekly... takes approximately 30 seconds if you keep the pump handy.

There is one other type of bike you may want to look at if you are looking for a super efficient ride. They are called cyclocross bikes. In Europe they use these things for off-road racing though mud, gravel, up mountains etc. They have drop handlebars like a road-bike, so your body positioning is much better for getting energy to the pedals, plus you are much more aerodynamic against the wind. The majority of long-distance bike tours are done on this style of bike.

Now we come to the crux of your question. My honest answer is: you cannot get a (quality, efficient, or reliable) bike for $200. Now hear me out.
Yes, I am a bike geek, but I am not a bike snob. I don't care, per say, that your bike came from Wall-Mart or Sears and not some fancy down-town bike boutique. But there are limits.
Most of those limits have to do with reliability. If you want a bike that will cost you more than the original purchase price in repairs within the first two years, then buy a bike for less than $400. Seriously, the worst bikes to work on as a bike mechanic are department store bikes because they don't hold a tune and will just be back the next week (along with their frustrated owner) with something else wrong. They also use such cheap material in all of the components that in many cases they can not be repaired and have to be removed and replaced. They are not built to be serviceable, they are built to be disposable. For most people this works, because honestly, most bikes get parked in the suburban garage and ignored after the first year. Probably because they have been ridden with under-inflated tires and the owners suddenly find riding "too hard". There are new bikes on the market for the $200 price range I know, but there are over 300 moving, engineered and manufactured parts on a bike. The only way I know to build that kind of machine for so cheap is to use slave labour (most cheap bikes are mass produced in China) or to build in the most environmentally filthy manner possible (again, most cheap bike are made in...). Don't be fooled by the hype: bike manufacturing is NOT a green industry. It's dirty. I have toured bike factories in Asia... it completely blew me away.

So: if you are going to buy for less (and I totally understand that sometimes the $ budget is not flexible) I would recommend used. I would not recommend the department store brands nor the mass production brands. There are still a few bikes made in Taiwan and Japan. They tend to be of better quality. Bring any bike you are thinking of purchasing to a bike shop to get a quote on work that it needs. All used bikes need work. Often I find it's cheaper to buy new.

All that being said there are some amazing shops out where dedicated volunteers have salvaged bikes that I would never touch. In Vancouver, that shop is http://pedalpower.org/our-community-bikes/ . You may have a similar shop in your nearest urban area.

Please let me know what you end up with! If it does need some work done and you are keen to try your hand, I can assist you as much as is possible though these forums!

Thanks, Chris, for the really informative answer...sounds like we'll be checking out a not so local bike shop next time we are near by...it also sells used ones.

Chris

Thanks for your offer! That was a great overview and now I have the followup Q: Would it be possible to get a list of the more likely "quality" bike makers out there? Leave out any don't sell below, say, $800 and the maybe/maybe-nots and the list probably isn't that long. I'm a decent mechanic but totally unfamiliar with bikes these days and if such a list is possible, it'd save me time and help to not overlook a good brand.

I guess the Q after that is what one should expect to get as the price goes up. From your recommendations above, I'd guess that a "good" basic bike could be had retail for about $450-$500, which I assume would consist of 2 wheels, handles bars and seat and not much else.

Where I'm coming from: I biked a LOT 40 years ago (10 miles a day minimum, 30-40 miles/day 2-3 days a week), but not at all for 35 years and now I don't race, don't trail ride (mostly) but I have come to appreciate a healthy and not-sore butt after a few hours ride; right now I might put in 10 miles a week max but hopefully that will go up. A more telling admission might be that I find the upright position attractive in many situations such as neighborhood cruising after dinner and such. I've ridden a (probably cheap) trail bike a few times recently and I don't find the narrow straight bars especially comfortable, although maybe I'm just out of it after so many years; when I rode with rams horns I usually rode hands on top.

I might add that I find the many-gears-syndrome extreme over kill and sometime a real pain. Seems to me that 95% of bike riding can be handles by 10 gears and if you're around hills, make the low gear lower.

Cheers

Rufus

Judith Browning wrote:We've been wanting bikes again...is there anything you would recommend for mostly gravel/dirt roads with some pretty steep hills for under $200? Thanks.

Hi Judith!
I of course am a lover of bicycles so I do have an opinion on the bicycle you may like, it is called the Africa bike made by Kona
they have really reasonable prices and I believe any bike shop can order one in, part of the price of the bike goes to provide bikes in other countries.
I think they are a little more than 200 dollars, maybe a used one would be at that price mark but if you think of the bicycle as an investment and pay a little more you will get a bicycle that literally will last you the rest of your life, and function as a work horse.
The step through frame (formerly knows as a girls frame) is the only kind of bike I love now after owning a couple, because when you have the back rack loded down with stuff you do not have to swing your leg up and over it to get on. I just wind up knocking the bike over and looking like a doofus at the store if that happens. The step through frame lets me just set through and get to peddling on my way.
An internal three speed hub is really nice as it alows you the option to gear down on those long hills and to gear up on the down side.

I encourage you to do a little research on these bikes, here is a starting place.
http://worldbicyclerelief.org/pages/the-bike

I am not an expert by any means but I do have to many bikes and wont get rid of any of them, but when I decide I have to have one more it will be an Africa bike.

I have seen a couple at bike stores and I think that some of them were about 350 bucks.
but you get wonderful things like fenders that keep the water spray off of your shoes and the back of your jacket or your cargo that you are hauling on your rear rack and the front basket, some even come with a tool kit to help keep things all working right!

Good luck with your new investment in you and your future!
Cliff

Chris Sturgeon wrote:Well, do ya? I'm a bike mechanic so I figured, why not ask?

Anything from repairs to storage to efficiency, I will do my best to respond.

Chris, I am glad you ask! I put together a bicycle for my wife as a fun little run around town to the library and such bike, I bought a lot of the parts off of eBay to do the build, which included a 700 c rear wheel with a Schimano SGR 20 8 speed hub.
The problem she is having is it seems to grind like the gears are not engaging correctly in 5th gear, I went through the procedure to adjust the shifter by going all the way to low then to high and then back to 5th gear and lining up the marks on the hub.

I have the replacement guts to put in the hub if necessary but I really am hoping that I may be doing something wrong and it is a easier fix than that.
The shifter is is a schimano twist grip, maybe it is not compatable?
when she is riding it she can adjust the cable length at the shifter to make it quit grinding but then it seems to do it in an other gear.
or maybe my cable housing is to tight of a bend at the hub?
Thanks a ton!
Cliff

Q: Would it be possible to get a list of the more likely "quality" bike makers out there?

what one should expect to get as the price goes up.

Hi, Rufus. The list of quality bike makers is indeed a long one. This is a very fractured and competitive industry. Bikes are a passion for many, and many truly passionate folks get involved by starting niche shops and brands. This is great for us because we get to choose between all these small business people's offerings and we get to support their passion as well! Look around and see if you have any local-ish frame-builders or designers. Because they don't mass-produce their product is oftn a bit more expensive, but you can get a custom work of art to ride to work everyday... how cool is that.

Bigger brands that I have liked, owned or worked on as as follows:
Navara (REI)
Mountain Equipment Co-op (great value here)
Kona
Rocky Mountain Bicycles
Norco
Old Schwinn (pre-2002) (was American made)
Specialized
Giant
But there are many many more. Anybody else have a good bike experience that they can share? I mostly trend toward the Canadian brands!

All of these brands make a more upright postured commuting bike. This is a comfortable (but way less efficient) option for many folks who don't feel the love on a more "aggressive" frame geometry.

As the price goes up on bikes one thing that you will get is what's called a "groupo". A groupo is shorthand (Italian I think) for the level of interchangeable components. Mostly this is your shifters, brakes, derailuers, chain rings, cassette and hubs. Sometimes it includes wheels, cranks, pedals and/or chain. Shimano has 7-8 different levels of groupos for mouantain bikes: they start (at the top) with XTR, middle is Deore and bottom barrel is Accera. Road bikes have their own heigharch starting with Dura-Ace. Generally, the higher end this groupo the better functionality, weight and reliability you get. For commuting I usually recommend the Deore level as it is a great compromise of price, performance and durability. There are other component manufacturers doing good stuff in the last few years: SRAM is an other good choice.
Basically, the more you spend on a bike (to a point) the easier it will be to ride for longer with fewer break downs. Mind you that prices on groupos tent to escalate exponentially between levels! I know musicians that would leap at a chance to buy a Les Paul original electric guitar for many thousands of dollars, where as a noodler like me is happy with a $200 (or less used) flat-top noise box. I tend to upgrade my bikes over the years and have found/traded/or purchased some XTR componentry for my mountain bike. It's sweet!



Hi, Cliff. I agree with your assessment of Kona. Good bike, fair price, cool company. I own a Kona Dawg dual-suspension mountain bike that I use for downhill rides and snowy winter slogs. Mind you, I've swapped out pretty much everything but the frame at this point.

re: internal hub. Good for you for putting together a bike! Internals can be tricky because it's hard to see what's going on. That being said, because all the works are not exposed to the elements, they can give years of trouble free service, especially in wet environments. Sorry to hear that's no the case for you.
Since it is a middle gear I don't suspect that it is the limits of the accuatur (the part on the hub that gets pulled by the cable). Miss-tuned bikes tent to have issues at very top or very bottom gear, not the middle. So your basic tune is probably solid. I know this is too basic, but double check that your shifters and hub are built to shift the same amount of gears. Shimano builds shifters in 7, 8,9 and now 10 speeds. They don't play well together.
Make sure you tune the bike in a stand (this eliminates torque from your problem and makes problem solving easier). Shift upward toward the lower gears one at a time. Put your ear right next to the hub and listen for any little chatters, rubs or skips. If you hear any use the barral adjuster near the shifter to slowly increase or decrease cable tension until the weirdness stops. Then go up one more gear and do the same. Repeat, repeat, repeat... ad nausea. Now do the same thing descending back down to the highest gear. Now go for a test ride and see if the problem come back under torque. Sometimes I've had to do this three or four times to find that sub millimeter sweet-spot in the cable tension.
If this doesn't work I would recommend contacting Shimano about a warranty, if they offer such a thing on Ebay parts. Parts bought at a reputable bike shop will always come with a service warranty, and often a free tune-up to boot! There may be a reason this particular hub was being sold on-line. Unfortunately, as with many things, cheapest is not always the best value.


Great questions! Hope this helps!

Chris

Thanks for the list of major manufacturers. And now I know a bit more lingo - groupo! Sounds a little like going from a Chevy to and Olds to a Caddy, but applied specifically to the drive train components.

Rufus

Rufus,

Sounds a little like going from a Chevy to and Olds to a Caddy

Ha! More like from Caddy to VW to Tesla in my opinion. Ha ha!

Hey Chris,
Thanks for the offer. I started another thread but I'm not finding the answers I'm looking for: https://permies.com/t/19273//build-BIG-bike-trailer#163221

I'm looking to build a tank of a bike trailer. Something that can haul 500 pound loads. I saw some in one of Pauls' videos about RMHs in Montana so I know they exist and work. What I'm looking for is someone who's built one so I can get some details. I'm figuring on welding parts of a couple of bikes together to make a four wheel system. Four wheels puts the same weight per axle as a 250# rider, which seems reasonable.

Thanks,
Greg

I do have a bike question. how did you know?

I've got a new (used) threaded fork I want to swap in, but my quill stem is bound in my current fork. I've already tried a whole lot of Boeshield trying to loosen it up with no luck. I also loosened the stem bolt just a bit and then whacked it with a mallet. that, unfortunately, only succeeded in bending the bolt without freeing the stem.

any ideas?

Hi Greg and Tel. Sorry for my tardy reply. I've been away (in Junuea) for a spell.

Greg, I don't know. That's a huge trailer for a bike to haul. How do you plan on peddling that kind of load? I would certainly suggest using for wheels in dually formation and an oversize rim. You will also want to protect the pull-bike's frame from torque. I'd probably suggest some king of rear-load tri-cycle with an intergraded cargo platform. It's going to be a beast... gear it LOW! Good luck!

Tel, What you have there is a classic case of molecular bonding. The real cure is prevention (sorry to be didactic). When you get that rusted bad-boy out and put in your new stem, be sure to coat the threads, quill, and anything else that touched with a molybdenum (white) grease. If there is any titanium on steel, steel on aluminum, or Ti on Al; be sure to use a copper buffer grease. At this point your best bet is a bath of penetrating oil (I like Tri-Flow, make sure you give it lots of time to capillary in... like a couple days) and mechanical force... but it sounds like you've tried that. A weighty iron bar used as an oversized punch and a 3 pound hammer. You can also try heating the lower steer tube a bit to ease the passage, but watch out so you don't scorch your paint! Of course make sure that the frame is clamped and secured in such a way as you don't tress the welds or impact the tubes as you do this gut-wrenching wrenching.

Hi Chris

Thanks for opening up this topic on the forum. I concur with your opinion on mega-store/cheap bikes-they are simply not worth the money and time lost through repairs.

I too am looking for a bike that can pull a trailer, handle rough roads, and a few hills, but I have a slightly more generous budget than one of the previous posters (hopefully under $1500). I've been racing time trials and triathlons (purely amateur) on skinny tires for the last 15 years so although I spend a good part of every week on a bike, I don't have much experience with other types of bikes.

So here are my questions:
I'm looking for something versatile but I don't know if a cyclo-cross bike could pull a trailer or handle a lot of potholes.

If most time is spent on pavement, are drops or mountain style bars better?

I've felt that bikes with front suspension rob too much power. What are your thoughts?

Would you recommend 26" wheels over 700c?

What is your opinion of the Surly brand?

I'd also like something with sturdy components that uses readily available parts. I can fix almost anything, but the older 7-speed mountain bike I converted to a commuter only lasted two winters since I kept breaking hard to find parts.

Thanks and sorry for all the questions,

Rich

Chris Sturgeon wrote:Tel, What you have there is a classic case of molecular bonding. The real cure is prevention (sorry to be didactic). When you get that rusted bad-boy out and put in your new stem, be sure to coat the threads, quill, and anything else that touched with a molybdenum (white) grease. If there is any titanium on steel, steel on aluminum, or Ti on Al; be sure to use a copper buffer grease. At this point your best bet is a bath of penetrating oil (I like Tri-Flow, make sure you give it lots of time to capillary in... like a couple days) and mechanical force... but it sounds like you've tried that. A weighty iron bar used as an oversized punch and a 3 pound hammer. You can also try heating the lower steer tube a bit to ease the passage, but watch out so you don't scorch your paint! Of course make sure that the frame is clamped and secured in such a way as you don't tress the welds or impact the tubes as you do this gut-wrenching wrenching.

I greased the shit out of everything when I put it in. used the phil wood green stuff, though, not anything white. I've given up for the time being, but I hope to get back to it before long.

Just a quick idea for penetrating oil to loosen stuff up. Even stuff that has been near salt water is a 50/50 mix of regular ATF and acetone. It's a cheap mix that works extremely well. I learned it from an old boat mechanic.

Robert Ray wrote: Just a quick idea for penetrating oil to loosen stuff up. Even stuff that has been near salt water is a 50/50 mix of regular ATF and acetone. It's a cheap mix that works extremely well. I learned it from an old boat mechanic.

sounds pretty nasty, but so does drilling out my very nice stem. which means I'll give it a try.

Hi Rich, I find cyclo-cross style bikes are a great compromise between on-road efficiency and off/rough-road sturdiness. But they are a compromise. Depending on your local conditions results may vary
Drop vs. flat (or riser) bars are mostly a question of personal preference of rider position. Many folks who spend time riding in traffic are more than willing to give up the aerodynamics and efficient body extension that drop-bars are designed for in order to achieve the more upright and face-forward positioning that comes with straight bars. Trail and down-hill riders need the faster steering and shock buffering (due to arm positioning) that comes with the straight bars. There is also the question of components, in that mountain bike style brake levers and shifters will no fit on drop-bars and vice versa. My favorite further hair-split is a compromise of a compromise: a flat bar on a light xc-mountain style frame, purposely sized a little too large to achieve efficiently stretched out body positioning... just watch your junk if you aren't proficient at a free-wheel track stand!

Suspension is also a case of being designed for certain environments, but not all. Properly tuned suspension will increase your efficiency. Most people think of it as a system for reducing vibration or impact... I tend to think of it in reverse... in the same ways that F1 race car designers do. Your suspension pushes your tire down into pot-holes, drops, and other un-even road surfaces, ensuring that you always have contact with the road to get good grip and forward motion. On the front, of course, it also softens the jarring of sharp transitions and allows you to roll-through rough terrain. Depending on the environment that you ride through this will either assist your being able to keep forward momentum, or will rob a bit of efficiency due to weight, bob and sag. For trailer hauling I would suggest a hard-tail with possible light-weight air-shocks (Rock-Shack Sid or Argyle) tuned to the stiff side or with a lock-out.

On road I would usually suggest 700c or 29er wheels as they have better rolling characteristics. However, depending on rim and tire, they can have more rotational weight. Ever notice how econo-box cars have smallish wheels and tires? There's an efficiency to not spinning all that weight, and there's a exponential increase in energy required to get it up to speed. In stop and go conditions small wheels are more efficient, in long steady speed conditions, use the fly-wheel and smoother roll of a larger wheel.

I think Surley are great bikes. They keep thinks pretty simple and they have decent price points. Bikes like the Long-haul Trucker are very popular commuting bikes, up here in Whitehorse us winter commuters (-30c last week) are fans of the Pugsley or Moonwalk frames. They seem to have compromised light-weight for sturdiness, which when rolling a trailer is a good thing!

Winter is HARD on components. Many people here go for single speed steel beater-bikes in the winter, just so there's less to break. Road side repairs in sub-zero temperature just plain suck.
Hope that ramble helps!

tel,
Phil wood is OK grease for low-friction parts like bearings, but when it comes to different types of metals being static but under pressing force (quill is a great example) they will undergo electrolysis and actually transfer bits of their molecules back and forth. Eventually the parts literally grow into each other and you have molecular bonding. Moly or copper grease acts like the zinc plate on an aluminum boat hull. It is sacrificial. No matter what, these types of parts should be disassembled and re-greased every few years... electrolysis happens whether the bike is in use or not.

If you have any canned air (the type used for cleaning key boards) you can try to super cool the quill in relation to the steer tube... see if you can get it to shrink a bit. A wasteful product, but better that some nastier chemical cocktails that I've seen.

So, I got hit by a truck today.

Nudged really, no harm to me nor my steed. They guy was in a work truck and was apologetic... called me Sir. Ha ha!

My question is surrounding my reaction. I was pissed off, of course. My initial yell was a resounding "Jesus Christ!", after the guy asked me if I was OK I just said "Dude! Look both ways next time!"

Is this effective? Is this ineffective? How do you other riders react in hit or near-hit incidents?

Chris Sturgeon wrote:How do you other riders react in hit or near-hit incidents?

first time I got hit was by an articulated transit bus and the driver didn't even notice. I jumped back up and tried to chase the bus down, but it was no use. not really thinking clearly at the time, I didn't get any identifying information off the bus. felt pretty dumb about that after.

second time I got hit was by a piece of shit driving a Corvette. chap got out and started fretting over his bumper. I kept a little bit calmer in that situation and reminded him that he had just about run me over when I had the right-of-way and more than likely damaged the accordion he knocked out of my trailer. I wrote down his license plate number and asked him for his name and contact information. turned out nothing was damaged, and I was just a little shaken up, and I hope he drives a little more carefully now. no way for me to know.

I also chased down a guy that tried to run me off the road. he was not prepared to see me when he got out of his car at his house, and I was prepared to knock him in the head with my lock if he got more belligerent. it was pretty clear that he was a teenager trying to impress his friend, and he sort of apologized. I still can't decide whether I let him off too easy or should have just let it go and ridden home. probably should have called some police, but it didn't even occur to me at the time. my encounters with the local police while on my bike hadn't been very positive prior to that.

I think the most effective I was was when I kept my whits about me in the Corvette incident. I didn't scream and yell, I didn't have my hand on my lock, I didn't get in his face.

I think it would be appropriate to point out that your life is very much at stake, and that there are very serious responsibilities involved with operating a motor vehicle that people just forget about. staying calm and thinking clearly is difficult, and I know I'm not good at it.

when you're involved in an accident like that, I don't think there's a whole lot you can do that would really be very helpful. at most, you're going to change one person's mind, and that will probably wear off. working to change awareness and laws so that drivers who hit bicyclists face meaningful consequences seems likely to be more useful.

when I was in Seattle, a bike club I sometimes rode with chained up ghost bikes wherever anybody on a bike got hit. they're visible reminders of what happened.

Chris,
Question !
I have a mongoose. I went to lube the bearings in the rear wheel. Looks like they are all separate and not in a cage. Is this a normal thing to have all separate balls as bearings in the rear wheel?

Question 2
I have a 21 speed bike and a 7 speed bike.
Seems like the low of a 21 speed is so much lower than the low of a 7 speed. But when I look at them. They look the same gearing. Do you know what the difference is?

Question 3
Have you ever put on Disc brakes on a bike from a parts bike? I think I could never afford a Disc brake bike. But maybe get a parts one to use and adapt.
Think its possible?
Thanks in advance for my basic questions.

Hi Jeremiah,

Great questions! And good projects to tackle... if not the easiest.

1. Bearings:
Yes, this is normal for any bike that has undergone maintenance. The first thing a good mechanic will do is throw that little bearing retainer away. The true purpose of that ring is to allow factories to slap together bikes faster... as loose bearings are a bit fiddly for mass production. The retainers can actually lead to problems like brinelling of the bearing cups. Be sure to check the cup and cone surfaces for spot friction or impact wear,
The one danger of un retained bearings is the temptation to over-pack the bearing. Be absolutely sure to leave a space between your new or re-greased ball bearings. The space should be about the size of one ball. I usually do this by completely filling the cup with ball bearings and then removing one. Be sure to use a good water-proof grease. I like Phil Wood.
One other thing about wheel bearings. The final bearing pressure is provided by the quick-release or wheel nut. This means that a properly tensioned hub-bearing assembly should have a minute amount of knock before the wheel is attached to the drop-out. This knock should disappear when the wheel is tensioned.

2. 7 vs. 21 speed:
I assume you are talking about a 7sp rear cassette vs. a 9sp rear cassette. Factors to keep in mind -other than the amount of teeth on your cassette's largest gear- are wheel size and front gear ring size. 21 speed bikes are usually a 3 chainring front gearing and a 9 ring rear cassette. The smaller the ratio of front teeth, in comparison to the rear teeth, the lower the gear. The smaller the wheel size, the lower the apparent gearing. *Fun side note- many of the gear combinations on multi-gear bikes are actually equivalent, meaning that your 21sp bike in actuality has fewer unique gear ratios than stated. This is why you should never have to cross-chain your drive-train to access all available gear ratios.* Hopefully this helps? Gears are all about ratios and there fore can get tricky, let me know if you have further questions!

3. Disc brake change-over:
This is a tough one as there are a few parts absolutely essential for disc brakes to work. The easy one is a disc-brake mountable hub. This hub will have the bolt pattern for your disc on one side and normal spoke holes on the other. Shimano has a cassette style slip-on slip-off disc bracket for their disc-ready hubs/wheels. Because the brake putts the braking force through one side of the hub -and therefore to an extent, spokes- the spoke lacing pattern on a disc-ready hub/wheel can be different from a balanced rim brake build. The good news is that all you have to do is buy a hub and correct length and re-lace your wheel, or just buy a pre-built disc-ready wheel.
The second necessity is a bit harder or conversely more expensive. You need to have a brand specific caliper mounting braze-on on your frame and fork. Basically, this is a hard-point to which your brake caliper body gets mounted. The front fork is easy enough to change out for one with a caliper mount (as long as the steer-tube diameter and length is a match), but the mount welded on to your rear-triangle is tougher. You either need a new frame with this hard-mount attached, or be a very good welder.
The third thing you need are the braze-ons that route the hydraulic lines from your levers, down your front-tube and across your and to their respective calipers on fork or rear triangle. I have, in the past, fabricated these out of old-school steel frame clamp-on style cable sockets... you could weld them onto your frame... or again a disc-brake ready frame will have them already welded in place. There is a bit of science to where they go to avoid brake-jack, pinching or steering limitations.
In all honesty, unless you are a cracker jack welder and wheel-smith (or are good friends with one), it may actually be cheaper to buy a used but good disc-ready frame and build it into a bike from your existing parts.

Fun stuff! If you need any clarification, please ask away.

Errrr... sorry, I read too fast and made a mistake above re: gearing. I was talking about a 27sp (9x3) gearing where you are actually asking about a 21sp (7x3). Other than the the two extra gears on the cassette (or free-hub on some older 7spds) all the same info applies. Sorry for the confusion!

Thanks Chris for being the Forums Bike Doc ! Any advice for a do-it-yourselfer that wants to adjust the shifting on a 21 speed Royce Union Mountain bike? I know nothing about bike repair but think the cable is stretched and can be adjusted easily . Maybe finding a spot where the bike is in a good gear then flippin er over and pulling the slack on the cable ?

Hey Wayne, no problems with the bike doc thing; the more people using efficient transportation the better!

For tuning your mountain bike: first I'll deal with the common misconception about stretched cables.... There is no such thing.
BUT... cable housing can wear, ferrules can seat and plastic parts can abrade. All of these small factors can create slack in a once tight system, making it seem like the braided steel cable has stretched. For all intents and purposes the fix can be the same... or not. the or not depends on the shape of the rest of the drive-train system (bikes are like permaculture; all the systems are interrelated).
Simple fix: If all housings are in good shape, clean and lubricated; if the shifters and derailleurs are clean, and straight, if pulleys are not worn or dry; and most importantly if your chain is not worn beyond 75% then you have a simple cable tensioning job on your hands. I love these.
1. hang the nose of your saddle off something stable, better yet get a upright bike stand for home repairs (this is the best investment in bike tools you will ever make! I have a running joke that most bikes can be fixed with a flathead screwdriver, a hammer and a blowtorch... if you have a bike stand. )I'd recommend something like this or better
2. loosen off all the tension on front and rear shifters by dropping your chain to the smallest cogs on front chain-rings and back cassette/free hub.
3. physically get behind your rear shifter and eyeball the alignment between your pulley wheels (the small wheels attached to your rear derailleur) and the smallest cog.
4a. if they are aligned perpendicularly but offset you can adjust this with the two limiting screws on your rear derailleur. These screws are there to limit the upwards and lowest swing of your derailuer... to stop loose tension from dropping the chain off your lowest cog and to stop high tension from climbing the chain up into your spokes. They are a bit fiddly, but start with the eye-crometer (look at it) and try to line the pulleys with the cogs.
4b. if they are not inline perpendicularly then you have a bent derailleur hanger. The ghetto option is to just bend it back by hand... BE WARNED, I have seen welded hangers snap off of frames with this option even on soft steel frames. If you have a removable derailleur hanger then this is a part that is built to be replaced... time for a trip to the bike shop.
5. Once you have your bottom limit set, shift up onto your biggest rings; front and back. Now do the same limit adjustment as step 4, but for the top cog on your rear gears. Now even if the rest of your shifting is a garbled mess, your top and bottom gears on the back should run ok (so long as you are not cross chained).
6. Shift back down to your two smallest rings, front and back (cross chained ).
7. Now is when you can release the cable retaining screw on your rear derailleur and pull any obvious slack through. Re-tighten the screw.
8. Try shifting up one gear with your rear shifter. if it doesn't quite make it or skips about, DON'T adjust the cable again.
9. Use your barrel adjusters!

Sorry I must run to work... more on gear tuning in a bit!

Thanks Doc ! I will either have to bring the bike to the computer or find a way to print that off though . Thanks again.

Sorry for the two part post. I do most of my Permies surfing from work so my available time is limited.

I found a fairly clear page outlining things like chain tension, limiting screws and barrel adjustments. Check it out.

Let me know if you come across any issues. Once you get the limits set, you can pretty much tune by ear while riding... just tighten or loosen your shifter's barrel adjusters as you ride and listen for the sweet spot where your shifting makes the least amount of clatter.

Chris Sturgeon wrote:Sorry for the two part post. I do most of my Permies surfing from work so my available time is limited.

I found a fairly clear page outlining things like chain tension, limiting screws and barrel adjustments. Check it out.

Let me know if you come across any issues. Once you get the limits set, you can pretty much tune by ear while riding... just tighten or loosen your shifter's barrel adjusters as you ride and listen for the sweet spot where your shifting makes the least amount of clatter.

Chris are you still around or did you leave us?