Will this compact chainset fit?

luv2ride

Hi. I need to change the chainset on my daughter's Trek KDR 1000 junior road bike to a compact to help her with the hills. I realise these crank arms are a little long at 170mm (hers are currently 150mm) but would this be a suitable replacement?

http://www.jejamescycles.co.uk/shimano- ... 71574.html

Her current gearing is 48/38 with a 130bcd chainset, with 8 speed Tiagra cassette. Current crankset is square taper. Anything else I should be looking at?

cheers

mattv

She will probably struggle with pedal striking. 20mm longer cranks is a massive change to the design of the bike.

arlowood

Have you considered looking at swapping the cassette for one with a wider/lower range?

Shimano do an 8 speed HG41 series cassette that you can order with an 11-32 sprocket spread.

http://www.evanscycles.com/products/shi ... e-ec029599

If her current cassette is say an 11-25 or thereabouts, the above might give her the extra range without the need to swap cranksets. You might need to stick on a longer chain but that's a minor issue

luv2ride

Thanks arlowood, that cassette sounds interesting. Current cassette is 11-28t. Would the 11-32 be likely to work with the existing Tiagra RD? Ive no idea of the model number unfortunately.

Mattv: good point about the risk of pedal strike with the longer crank arm...

maringirl

a 50t ring sounds well big for a kiddy?

imposter2.0

Something like this would make much more sense..

http://www.ebay.co.uk/itm/lasco-junior- ... 257e985d88

luv2ride

OnYourRight wrote:

Have a look at the Stronglight Impact Kid. Available in a variety of crank lengths and chainring sizes, and reportedly high quality. Square taper. Compatible with 8/9/10-speed drivetrains. Example.

You will probably need a new bottom bracket whichever chainset you get (107 mm for the Impact Kid, 110 mm for the FC-2350, etc.).

That looks perfect, but why do I need a new BB? Would the cranks not fit the original square taper BB, or rather what should I check to see if they would? cheers...

skyd0g

Another thing to consider with the potential longer cranks would be possible toe overlap on the front wheel.

luv2ride

So, close to hitting the button on the Stronglight Impact Kid. Have removed the Bontrager cranks on the bike and reckon the Shimano square taper bottom bracket has a 107mm spindle. I see the Stronglight cranks are JIS standard, would this be compatible with the Shimano BB already installed? cheers....