Budget CX for girl/teen
 

Hi bike peeps -1st post -eek! :thumb:

Need to get my daughter a bike - she goes to the local bike club that does CX, and although she can hire a bike from them, i want to get her a bike for her birthday in a few months that she can also maintain,go to school with and use at the club.

As most teen CX start at about £400-500 and i don't have that sort of money(as well as London not being a good place for expensive bikes).... i'm looking to build one.

What's bike model is good to start with ?
-Hybrids are often shorter and have better clearance as well as having 700c wheels - so looking for that to start with(as ebay has no cheap CX bikes but loads of of hybrid ex.commutes).
-Alu, mass produced and a few years old - (basic components ok -can upgrade as they break)
-Small size 15"-17"
-£100 -ebay

Then what would i add?
-Short reach breaks/sti shifter? + Tektro top mount levers (made for women/child?)
-Aluminium drop 'bar, short reach, shallow drop? (made for women/child?)
-Cyclo Cross Race tyres (Continental ?)

-good/bad idea?

advice please?
ta. .r

The most expensive part of a CX conversion is usually the brifters. If you're willing to settle for bar end shifters instead then things get a lot cheaper.

Omega FSA seem to the compact bars that most people like (personally I like my extra wide Salsa Bell Laps - the Moto Ace is a cheaper version.)

The biggest thing for you to worry about is fit and especially reach and top tube length. I'd suggest using this:

http://www.competitivecyclist.com/za...LCULATOR_INTRO

as a start, choosing the Eddy or French Fit results. Ideally, get a bike that matches the suggested top tube length, but which gives more standover. Of course ideas on fit vary a lot - if you have a hire bike that your daughter is happy with, then trying to clone that should work well.

Warnings:

1. Do NOT use cross racing tyres for commuting! Or at least use only carefully selected ones. Tyres with side knobs for cornering in mud can lose it if cornered hard on tarmac when the knobs squirm. Tyres with a mud pattern on the main surface of the tyre often have poor braking traction on tarmac. Go to Schwalbe's site (the US one, not the UK) and read the info they provide on their tyres carefully - the detailed ratings will help you understand how surface specific tyres are. One answer would be to go for TWO sets of affordable wheels, so that you can keep one set up for cross and the other for road. A lot depends on what sort of conditions your daughter will be racing in.

2. A lot of crossers have poor front brakes. Partly because they're not set up right, partly because getting brake clearance for racing in mud requires trading away braking power. I wouldn't let my daughter (if I had one) ride in traffic with such a bike. The simplest and most foolproof solution is to fit a v-brake and a travel agent (a v-brake compatibility adaptor) at the front. Keep the canti at the back - TAs tend to jam with mud there. The other option is a low clearance mid-profile canti with a fork mounted hanger and carefully tuned straddle cable. A vee is easier.

Read:

http://www.active.com/cycling/Articl...oss_Brakes.htm

Some people might disagree with me on wide profile cantis, clearance and road use; listen to what they say closely, especially how they tune the brake if they do get good road stopping power - which for me means that you can keep your weight on the saddle and still brake so hard your rear wheel will lift slightly.

3. Wait: a hybrid will come with vee's... Ahah! If you fit bar end shifters then I believe that there are cheap v-brake compatible single speed brake levers available - so you wouldn't need TAs.

Speaking as an ex-messenger, any bike that is going to be ridden in urban traffic has to be set up with riding in traffic as its first priority. Yes, you can get away with a bike that isn't, but you're trusting to luck. I prefer to trust good engineering and sensible equipment choice.

4. Some hybrids have stupidly small clearance for wider tyres. It's only a very few, but make sure you avoid these models.

Re. interrupt levers: I'm thinking of fitting them myself and have been doing some research. Do NOT follow the advice some people give to use compressionless gear cable housing! This makes getting a path that won't reduce braking power easier, but gear cable housing isn't designed to take the higher strain of braking and can suddenly rupture - which, of course, is most likely to happen just when the brakes are needed most. There is such stuff as compressionless brake cable now. If you have problems, search some of this stuff out.

Bar end shifters might cost you £40 new, much less used if you are lucky. Single speed levers £20, the bars £20-30, £15 for a stem. Add in some cable and a use bike, tyres (£50-£100) and ideally Kool Stop pink or dual brake pads.

If you go for STI levers, new Sora 8 and 9 speeds are £100 a pair, plus you'd need two sets of TAs (£10) each to make the v-brakes work. Or decent cantis are £25 a wheel new. Obviously you can save money used, but the supply of used STI levers is small, and if a used Shimano lever goes on you it is almost impossible to repair beyond replacing the Big Spring. (Unlike Campag levers.)

Another problem with STI is compatibility with the existing powertrain: bar end shifters can always be persuaded to work (at least if they have a friction mode) but STI is fussy. So make sure that the hybrid has a ROAD power train, not an MTB one, as well as the right number of speeds. (Unless you want to do a "Shimergo" bike, which could actually be a very good idea - Campag shifters and Shimano MTB powertrain. But then you're into stuff I've never done, so you'll have to google. Just make sure you can get a large enough MTB outer chainring.)

Other alternative:
Classic steel touring frames last forever and have the clearance and brake mounts you need. Go to retrobikes.co.uk for advice.

Oh - and if you want to make a bike theft repellent in London:

- Cover the frame in uncool highly recognizeable stickers. Thieves hate having to pull them off. If your daughter has a favourite boy band, this is their hour! Adding bits of reflective SOLAS tape will make the bike show up better at night too.

- Use a locking technique that prevents the use of bottlejacks:

http://www.sheldonbrown.com/lock-strategy.html

- If you're not using a cable through the wheels religiously, then fit the road wheels with security skewers.

- Put hot melt glue and a tiny bb in any allen key bolt that holds expensive hardware. You can get them out with a minute or two of chipping and a strong magnet, but thieves hate this. Not great for components that may need fast changes in a race though.

- Extreme but effective: attack brand names on any expensive components with a dremel, then slosh them unevenly with pink paint. Advanced paranoids first dribble epoxy in carefully selected places to create rivlets and bumps.

Sounds like a fun little project.
If you want it on the cheap, I would stay away from STI/ergos. One good fall and $200+ down the tube. Barcons all the way.
How good is craigslist out there? Can you find a lot of the stuff used?

You can always get an older touring bike and convert it.
Surly makes a cross check in 47cm i think?? This is a great all around bike.

also.. tektro r100 brake levers are the shorter reach versions of the r200 meant for smaller hands??

Cross Checks are about £900 for the basic model in the UK. Waaaaay overpriced. So you see very few used cross checks, and the ones that you do see are not cheap. By comparison, I'm guessing that a barcon + hybrid bike might come in at around £250.

Anyway, Cross Checks are heavy for their size and price - this is not great in a racer which has to be shoulder carried while sprinting up a hill, especially for a woman or girl. If the OP was to spend real cross bike money, then the Cross Check should probably be the last bike on his list. A Kona Jake would be much more sensible.

I bought my daughter a '94 Specialized Rockhopper with the intention of converting it to a 26" wheeled CX bike. The top-tube doesn't slope much and it already had cantilever brakes. Alas, I was unable to talk her into drop bars. It's still a pretty nice bike. Old rigid mountain bike like this are always available for around $100 (at least they are here), and I think they're the perfect place to start for a budget CX build, especially for a shorter person.

I would suggest a 12 speed classic/vintage bike from the 1980's. The bike should be light enough to be carried up a flight of stairs by your daughter, or about 23 lbs. An old-school bike should be as tough as a cyclocross bike and will accept CX sized tires.

If the bike does get stolen, it will be a smaller loss than a new bike.

My daughter has a newer CX bike and enjoys using it in Chicago. The lighter weight of the bike is a must-have.

However

- MTBs tend to be heavy, and this is a real handicap in carrying bike up a hill in a race.

- Also: 26 inch cross tyres are a pain to find. In fact, I doubt that you can find a 26 inch 32mm mud tyre.

26 inch drop handle MTBs can be great bikes, but a hybrid is lighter and a 700c wheel gives a much greater choice of cross tyres.

Yes but

-All cheap bikes tend to be heavy, and many old MTB have easily trimmed excess weight in the wheels and handlebars. I think 25 pounds is easily in reach with the right frame (e.g. Rockhopper or Stumpjumper rather than Hardrock in the Speciailized line).

-26 inch wheels accelerate better, which is obviously good for CX, and wide tires where allowed (i.e. almost all amatuer races) aren't such a bad thing and on many courses are a distinct advantage.

Nope. My used Lava Dome cost me more than my used Sirrus, but the Lava Dome weighed a ton more. This is utterly predictible - MTBs are made a lot stronger than hybrids, especially sports hybrids. The MTB has to be good to take repeated 4 foot drops, the hybrid doesn't. Strength costs weight.

Yes, you can lighten an MTB. But why bother when a hybrid starts out perhaps 4lbs lighter for the same price used on ebay? Why pay extra money (and to lighten a hard-tail MTB by 4lbs costs a lot) and do extra work (to get 4lbs off the weight you'll have to change the cranks and forks and maybe the BB) when sports hybrids that can take 32mm tyres like the Sirrus are easy to find?

I have a physics degree: don't provoke me into doing the maths! Trust me when I say that you're wrong. (The reduction in rotational energy is trivial as a part of total kinetic energy requirements - which mostly consist of rider KE - and the work that has to be done against rolling resistance during acceleration is increased - this matters enormously on rough ground.) Really, if you were right then pro racers would race crossers with narrow 26er wheels.

This may be true. But it hardly helps if the young lady wants to learn to how to handle a cross bike with a view to racing at a higher level as an adult, which she probably does. She should be learning the feel of handling a crosser, not an MTB.

No, I thought about suggesting that the OP look for a Kona Explosif frame myself, but for this use it would be wrong. His idea is the best one.

wow -great reply's thanks all. I learnt alot, including my need to get over my dislike for bar-ends and v-breaks.... Also tires and break tech links very useful - safety first!..
Can anyone recommend make/brand of a cross/road compromise tyre -or should i be using two sets? (i have a spare pair of 700c rims and road slicks)

mountain bike:
= nightmare = google 'Frankenbike' - very cool but to make it uci legal i would need converting for 700c = cost
Also ebay mtb mostly have suspension and heavy disk breaks. A old school thinner lighter mtb frame might be cool, if i replaced their heavy forks (also their top frame are flatter for carrying). Practically i don't have a garage of bike parts, time and deep pockets.

road frame:
yes i love 80's road frames, my dailly urban steed is an early allu canondale (fully camouflaged to look like a piece of ****e with a miniD lock & security skewers). 80's allu bike's are rare, desired (for urban fix'ies), and hardly ever in child/womens sizes. steel too heavy.. also clearance might be an issue (although if i swapped the cranks to a smaller (child sized) & short reach stem, it might be ok?)

hybrids:
glut of them on ebay as they were/are very popular(i.e. cheap) as commute bikes so easier to find a small or maybe even a small/wsd style. frame shape is often perfect with clearance and short sprint style frame, mostly have 700c, alu frames and V/calliper breaks. i.e. only work/cost will be replacing the cockpit & tires..

cost:
is it worth it?
I reckon it will cost be £100-£300 in total (depending if i can find parts second hand and a 'broken' ebay small hybrid).

luath700 = £499
road Decatalon Jr = £199!!! http://www.decathlon.co.uk/EN/triban-junior-172069436/
dawes Espoir = £400

that decathlon looks tempting - any reports - none on the web, i'd hate to buy rubbish at whatever price, as it will have no re-sale/cycle value?
thanks again!!!

Tyres: go to Schwalbe's US site and trust their descriptions of tyres absolutely. For they are German and engineers:

http://www.schwalbetires.com/bike_tires/cyclocross

http://www.schwalbetires.com/bike_tires/road_tires

The tech people at Schwalbe told me that the best bet in their line for dual use is the Extreme and I use it myself. It's got excellent road handling - perhaps the safest road tyre I have ever ridden because of the wet grip, although definitely not the fastest - and is good on any sort of dirt other than real mud, but it is very expensive (£70-£80 a pair!) and won't be quite as fast offroad as real cross tyres like the Rocket Ron. The Marathon Cross might be a good cheaper alternative.

Using real cross tyres on the road will get expensive because they'll burn out faster than the dual use tyres (ratings like "durability" only apply inside a category - a 4 star durability cross racing tyre won't be as durable as an Extreme.)

Anyway: the right tyre choice is critical for road safety and racing speed. This is probably your trickiest area. I don't have a daughter but I do have two cats that I'm very fond of, and I wouldn't let either of the cycle regularly in London traffic on, say, Michelin Muds. If you do go for a real cross tyre, make sure it has at least a 4 star rating for "hardpack" under Grip - and even then, test it yourself on emergency braking and cornering.

Re the linked bike - it's a 24 inch wheeled bike for 7 to 11 year olds. If this is the right size for your daughter there is no way she can ride a 700c frame. Or vv. Also: it's a road bike and probably won't have the ability to run wide cross tyres - if you could find them in 24''.

About second hand parts - you almost certainly know this - don't buy second hand stems and bars. Or if you do, be very cautious. You don't know what stresses have been put on them, and alu stems and bars can snap in use; I'd only ever use a used stem to try out a particular size and angle briefly and very cautiously. About the only things that you can buy second hand and save much money on are the bar cons, it seems to me. And a spare set of wheels if you go that way.

Yes it would be a bit on the small size(annoyingly they don't give measurements).. A 16" mountain bike fits her perfectly now and with a road bike shes between a isla 17"/18".

The Decathalon jr is used as a cross bike(looking a french websites), it also has short reach bar brake levers.. tires seem available.. http://www.google.co.uk/products?q=c...es+24%22&hl=en. but yes its too small.. doh

i didn't know that about 2nd hand handle bars.. thx..

I can't believe that a bike for an 11 year old would fit her if she rides a 16" MTB. We are talking about seat tube length here, yes? Like http://www.evanscycles.com/help/bike-sizing ? My girlfriend takes a 16" MTB frame and she's 5'4''.

"Cross" as a brand name doesn't mean UCI cyclocross legal (although that might not matter - rules will be lose in junior races I imagine.) Cross tyres are 35mm tops - 32 now in high level races. Those tyres are more like 45mm.

Well, you can certainly get away with 2nd hand bars and stems - people don't change them on a new bike. (I'd suggest that they should at least pull grips and bar tape off and inspect them for small cracks.) But if you have to buy bars and a stem anyway, why not pay the extra £10 to get ones that you know haven't been compromised? Especially as they are such a safety critical part of a bike. Otoh, if you get offered a hell of a deal and can inspect what you're buying it should be ok. I'd just want to be extra cautious with a bike being ridden by a child/teenager in traffic.

Useful link:

http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3812

(I am paranoid on this: I have had parts fail suddenly on used bikes, and if the steering had ever failed like, say, the crank arm that dropped off, I might well have been road jam.)

she's the tallest in her year(short torso, long legs, huge feet - lol) the 16" is a trek mountain bike that the cycle club measured her up to use... i presume its seat tube length, its got a big sticker with 16" on it..

i will do the fit calculator link at the weekend..

How long are her legs and what is her height? I'd normally think of a 16'' mtb being a fit for around a 29'' leg. If she isn't around that size, then they are sizing their frames in some other way.

Locally here in SoCal, I've seen lots of the kids on Ridleys. They make proper CX bikes for kids all the way down to like a size 41 methinks. Not sure of pricing on your island.

Me too. See how that doesn't qualify me as an expert in bicycle science? ;)

Break out the math. Assume rider weight is constant, and disregard frame weight as it is an unknown and possibly equal. I think that means we can simplify things to just the wheel/tire combination. Figure 2" tires on the 26" wheel and 35mm tires on the 700c wheel. The larger diameter (by about 32mm at the edge of the tire) of the 700c wheel gives it a rolling resistance advantage, but the wider tire on the 26" wheel will offset that to some degree. Let's assume, for inertia calculations, that the weight of the wheel is uniformly distributed at the rim and the weight of the tire is uniformly distributed at the edge of the tire. Wheel and tire weights are variable. At some weight, I think, there will be an equilibrium between the two wheels where moment of inertia and rolling resistance give them equal acceleration characteristics. Your task is to show that the weight in question is outside the norm for real world wheels. I wouldn't be surprised if you're right, but as they say in Missouri, "Show me."

Obviously, the OP isn't interested in a 26" wheeled bike, so it would seem I'm just debating for the love of mathematics at this point.

Actually, it's already largely been done on the wikipedia page for "bicycle performance" - look at the example calculation: any conceivable saving in inertial energy requirements is trivial compared to rider KE. I think their example showed ultra light wheels taking 35J off a 7000J burst of acceleration. Lets double this saving for a combined radius and weight saving - 70J. (Although most MTBs don't come with wheels as light as a sports hybrid!) I think we can assume that in a childrens' cross race, while accelerating on the flat, that at least 1/4 of work will be done against RR - that's 1700J. The difference in RR between a 26er and 29er MTB is around 10% - so that's 170J versus 70J while accelerating. After having found freakishly light but cheap MTB wheels! (Please let me know where - I want some!)

And the MTB based bike will have higher RR while cruising.

Worse, these assumptions are heavily optimistic for the 26er- in practice I think you'd see double this ratio for a moving start sprint and quadruple or more for sprinting from the start line, especially given the poor choice of MTB cross tyres.

Even if you disagree with my assumptions I don't see how could you change them enough to make up for the MTBs weight disadvantage while being carried - remember that a teenage (?) female will have a much lower ratio of upper to lower body strength, so bike weight matters much more than for an adult male. You'd need to get a HUGE acceleration advantage for make up for this. In fact, I think you could eliminate the entire rotational energy cost and it still wouldn't be enough.

Lightening a hardtail MTB down to hybrid weight is a pig of job and damned expensive. As long as the young lady can fit a 700c, I don't think that a 26er should be considered. If the bike was being used as non-racing crosser then my opinion would be different - drop handles, MTB gearing and toughness and 2'' Marathon Extremes or Duremes would make for a superb trekking bike or a commuter that come whoosh along singletrack on the weekends.

I'm having a little trouble seeing through the hand-waving on the Wikipedia article. It shows energy calculations for a rotating wheel at constant velocity and shows that the energy there is independent of radius. It doesn't say how long, given constant torque, it takes the wheel to get to that energy, which is the relevant point here. It also spends a lot of time dealing with aerodynamics, which matter much less in cyclocross than in crits.

All I'm saying here, mind you, is that smaller wheels accelerate faster than larger ones, even at the same total weight.

Yes: they take the difference between two energy states as being the acceleration energy as if the transformation is instantaneous. Which is ANOTHER biasing of the equation in your favour! (Because it neglects increased RR for a smaller wheel.) I don't see why you have problems following the calculation?

Yes, they do. It takes less energy to spin up a smaller wheel. However, the energy taken to spin up a wheel is tiny compared to the energy needed to accelerate the rider's mass. You can spin your wheels to the equivalent of 20mph with a single flick of the pedals when the back wheel is off the ground, and then braking them is instant. So a reduction in wheel energy requirements doesn't really matter a damn. Which is why folders with 20" wheels and MTBs with slicks do not out accelerate 700c bikes.

Oh, I follow the calculations. They just aren't calculating everything I'm interested in.

What I really like about the wikipedia article is the section offering explanations as to why the calculations are not in agreement with accumulated observation (a.k.a. "widely claimed benefits"). Granted, the mass perception can be just plain wrong and the existence of the claim furthers the perception, but I'm not convinced that's true in this case.

BTW, I'm also not convinced that a 700x35 tire has less rolling resistance on dirt and grass than a 26x2.0 tire, given reasonable inflation of both.

leg 76cm/30" (& long feet adds a tiny bit)
height 157cm/63"

Accumulated observation and "widely claimed" are not the same thing. An observation implies some degree of rigour; but most people are easily led idiots. Most people believe, for example, that reducing wheel weight significantly increases maximum speed. But this isn't an observation but an opinion. Which is to say that it is junk.