Any question answered...

Son won schools Rollapaluza competition,
(just 250m mind but 13.07s).
Good excuse to get him his first fixie to let him train for the forthcoming
inter-school competition.
Rolla Junior spec is 48:16, (easily done),
but,
125mm cranks!
Any suggestions?

Mike Burrows, amongst others, can cut cranks down. Don't know what's available OTP

125mm cranks!
Any suggestions?

Pricy option?

http://bikesmithdesign.com/
Mark is meticulous and a very smart guy, and I think quite reasonably priced.

You can get crank shortner to shorten the cranks, so you can adjust the length as he grows.

125mm cranks!
Any suggestions?

Look in a BMX shop, there are a number of options from cheap to bling for nippers, mostly aluminium square taper 110mm PCD so they are easy and cheap to use on a track bike.

The problem with most shorteners is that they increase Q by quite a bit, something which isn't going to help little legs which already find normal road cranks to be like riding a shire horse. That also applies to BMX cranks, of course, but to a lesser degree.

I'm looking into the possibility of grafting a chainring onto some 'Zero Q' Unicycle cranks to get short cranks with a narrow Q, at £14 these are cheap enough to allow for experimentation.

Many thanks to the five of you for answering.

I also found the Unicycle option, but floundered at how to get a chain ring attached.

The shortened cranks look promising, as do the shorteners,
but,
it may be rendered a bit moot.

He is just 14, 66kgs and 171cms tall,
and with a bit of saddle adjustment can ride my bikes, (54, 92 kgs, 6'1"),
so apart from this specific application has no need for for adjustable cranks.

I will have a look in a couple of BMX shops,
but it may just be he has to HTFU,
(in a softened, loving father kind of way).

I'm guessing the shorter cranks allow faster leg speed?
So training on a fixed wheel, 48:16 with 170mm cranks,
will make the 48:16/125mm cranks seem harder or easier?

It's all about gain ratio

Shorter cranks have a higher gain, so the same gear ratio feels harder (because it needs a higher force at a lower foot speed to get the same wheel speed)

When you are artificially limited to a low gear ratio, you can change crank length to get the gain ratio you would regard as optimal for the exercise in question, and with a bit of time to adapt you end up doing the speed you would with the same gain achieved with 'normal' cranks and a higher gear ratio.

Is the Rollapaluza rule that they have to use 125mm cranks, or that nobody can use cranks shorter than 125mm? The latter sounds like a more sensible rule, there's no advantage in restricted-gear events to using long cranks, so there's no reason to prohibit them, whereas short cranks favour the strong, which is what they are trying to avoid by restricting the gear ratio in the first place.

The Rollapaluza RoadShow rolled into his school, largely unheralded.
As one of the few kids who regularly cycles to school,
and has coped with gradually increasing distances,
(nothing Audax-y, just Ruislip -Ealing, Ruislip - Staines),
he was nominated by his classmates and put up the best time.
Entry was restricted to Y7 & Y8 pupils.

The 'bike' omits the frontwheel, removing the need to balance,
leaving the rearwheel to spin a roller. Adial indicates when the target 250m
has been achieved.
The gearing is 48:16 freewheel with no foot retention.

With the new school year starting, I contacted the Rollapaluza guys to find the
Junior spec and had the short cranks confirmed.

As far as we know the inter-school competition will use the same set up,
(even though he is now in Y9),
so as a supportive father I started to assemble the required equipment,
(Elite Supercrono Power Fluid trainer, old frame with 48:16 on a flipflop hub),
to let him train/practise, but found 125mm cranks a poser.

Thank you for the link to Gain Ratio.

This gain ratio stuff is legit, I've beaten Tester in MG events the past two years and he put 20 seconds into me this year on 140mm cranks.

What valve extension will work with a Vittoria Pista CS tub? It has a removable valve stem, but not one which works with my no-brand extension or my red Vittoria ones. That's three different valve types on 3 Vittoria tub models I've had, which is nice.

Many thanks

Are

https://www.google.co.uk/shopping/product/13359834686700572268?q=campy+record+pista+hubs&safe=off&espv=2&biw=1185&bih=647&bav=on.2,or.r_cp.r_qf.&bvm=bv.76247554,d.d2s&ion=1&tch=1&ech=1&psi=gMEmVIDBMI7daIzDgegC.1411826048988.5&ei=jsEmVK-4Io7VasSDgbAC&ved=0CKEBEKYrMAQ

and

http://www.ribblecycles.co.uk/sp/road-track-bike/Campagnolo-Rear-Record-P-Track-Hubs-small-flange-32H/CAMPHUBT350?utm_campaign=Googlebase&utm_medium=organic&utm_source=Googlebase&gclid=CjwKEAjwwJmhBRC56KOelNOXhxUSJAB_w2uNlf1-l1jYNbZET9jExzO7Vz_asmnoA_TcJxdWvbkJ4hoCfh7w_wcB

slightly different?

Ribble is listed on Google Shopping as being the cheapest, but the image on their website is not the one pictured elsewhere...

Shiny bikes now seems to be the cheapest.

I wish they'd roll into my sons school, all his friends ride bmx or scooters yet he wants one like mine.

Get him in the forum youth club, always recruiting haha

is not grooming

Don't know about that I was browsing anti porn earlier and he peeked over my shoulder and said nice, nice yeah I'd ride that

@craftybutcher
Pretty much the same at mespilus minors' school.

Single speed bmx or sub-stunt bikes,
Halfords mountain bikes,
although a couple of the 6th formers, (in old speak), Y12/13 in modern parlance
have fixies or singlespeeds.

He normally rolls to school on his Schwalbe Marathon shod Trek 7100,
(LB Hillingdon has poor road cleaning),
but when Dr Bike showed up he insisted he took his Reynolds 653,
which was the only bike Dr. Bike positively commented upon.

Have you tried emailing isla bikes? They defo have that length cranks and you'd imagine would have spares for repairs, although might not fit normal bike...

Or something like this:
http://www.jejamescycles.co.uk/trek-kids-dialed-127-152mm-42-34-24t-crankset-black-id84416.html

Can anyone suggest an emergency plumber in Kew?

Cannondale CAAD 8 headset -

Will something like this fit?
http://www.chainreactioncycles.com/fsa-orbit-is-2-cc-headset/rp-prod6183

I'm assuming that it's a pretty standard drop in style integrated HS?

Cheers, I've ordered one and will see how it turns out.

Cannondale CAAD 8 headset

There are 3 main dimensions for integrated headsets, inner race chamfer angle, outer race chamfer angle and outer race diameter. Almost any combination of the three has been done, but the two really common ones are FSA 36°-45°-41.0mm and Campag 45°-45°-41.8mm. I have a feeling Cannondale use 45°-45°-41.8mm headsets on CAAD8 and other integrated head tubes with 1⅛" steerers