Isla 24" geometry for a bamboo build

[willpom]

Who's daughter/son has an Islabike Beinn 24"?

Would you take some measurements for me please as Isla are the bees knees when it comes to kids fit? Last year I built a bamboo bike for my son using a paid for custom design from the kit providers. It wasn't right, the BB was way too high, the same as an adults and there was toe overlap. I've been sent a new kit and am attempting to design one in RattleCAD, the free BikeCAD won't load in any of my browsers. I'd like to compare with an Isla geometry.

I'm after:

BB height (centre to floor)
Wheelbase (dropout to dropout)
Chainstay length (centre BB to rear dropout)
Effective horizontal toptube length (horizontal line between centre head tube and seat tube)
Handlebar clamp height (centre to floor)
Crank length (centre BB to centre pedal spindle)

(I'm guessing most in this section know how to measure those but just in case)
Any help would be much appreciated.

The current frame
BB height
Toe overlap

[martinn]

Hi Will,

Not a Benin 24, but my daughter has a Luath 24. your welcome to come round and take whatever measurements you need, if that's any use to you

Regards

Martin

[willpom]

Cheers Martin I will. Going to build him a fast audax bike as well

Will drop you an email. About Steam Express as well

Will

[willpom]

PS I'm still after the Beinn dims as I'm unsure if it is the same frameset used with different components.

Thanks

[Brucey]

suggestion; would not both problems be mitigated if narrower tyres were fitted to the extant frame?

Also, judging from the saddle height, a 24" wheeled bike of any kind is probably a bit of a push...?

cheers

[willpom]

Find me some narrow 507 tyres. 40mm was the smallest I could find and they are no longer made in that size (Schwalbe Kojak). FYI 520 rims with 23mm tyres have a 7mm smaller diameter = 3.5mm lower BB.

The saddle is higher now, kids grow, quick. But not quick enough to compensate for a BB that is so high that when his saddle is in the correct position there is still 45mm from his toes to the floor

[Brucey]

https://www.amazon.co.uk/CST-TYRES-SLICK-507-32-REFLECTIVE/dp/B01LWJAA3X

also

https://www.felt-stuff.com/parts-spares/road-cyclocross/forks-wheels/1299/f24x-tire-kenda-happy-medium-24x1.125-32-507

not in stock but this is temporary (they say)

any good?

cheers

[willpom]

Nice work! I was looking at the higher end stuff as he's been doing big distances.

But still, I've just given the boy a sizing. His saddle is set right for the cranks (he's grown so they can go +10mm) and I added wooden blocks for him to get his toes down. 45mm as previously stated. Narrower tyres will not solve the problem.

[RickH]

Here's a radical suggestion - have you tried emailing Isla Rowntree herself?

Having met her recently on the Wayfarer Centenary weekend (she was riding a 1920s bike in tweed kit), she seems a friendly enough lady & the frame dimensions are hardly going to be a state secret. It wouldn't surprise me if she would happily send you the full dimensions.

You could also check if the forks fitted are unusual - possibly extra offset so you can use a shallower head angle (I think I've got that right), which helps avoid toe overlap. She might sell you a set if they are different & you ask nicely.

[Brucey]

I appreciate this is perhaps a radical suggestion in this day and age, but since plenty of adult riders have to slide off the saddle before they can get a toe down (and are happy to do so, there isn't enough cornering clearance if the BB is lower) then it maybe isn't the end of the world if a child has to do the same thing?

cheers

[zenitb]

Download a side view and print it

Measure the frame angles using a protractor

Read off the various tube lengths and scale them up. You know the ETRTO size of a 24" wheel.

Job done?

[Brucey]

there is a very useful program called 'MB ruler' which allows angles etc to be measured accurately on the screen. IME such measurements are pretty good provided the photo hasn't been taken with a very short focal length lens.

cheers

[Mick F]

Comparing the Bamboo and Isla, the Bamboo's chainstays are too long, and so are the seatstays.
Shortening both will move the cranks rearward.

[amediasatex]

What length cranks are you currently using?

[martinn]

Hi Will,

If your still looking I found someone with a 24" Benin

Martin