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Have just built up my 11yr old daughter's first 'big' bike to replace her Frog 69 from bits lying around the garage. She loves it to ride but it's obvious she needs shorter cranks than the 175's I've fitted.
I've had a look online without any luck - any ideas? Ta muchly.
Spa cycles is usually good for this sort of thing, I.e
https://www.spacycles.co.uk/m8b0s109p3752/STRONGLIGHT-Impact-Kid-Cranks
I use 165s. Fairly readily available from Shimano (and others). It's a normal adult size, not specifically for kids. Not bought any recently but they shouldn't be too hard to find.
SJS is the other place that is likely to have shorts cranks. Pick your budget from £18 to £200
https://www.sjscycles.co.uk/cranks-cranksets/?length=165
I've always got 165s from CRC/Wiggle/Merlin (although IIRC my current 165 SRAM ones came from the Germans). Does sometimes limit your choice of cranks though.
Thanks Kilo I'll give SPA cycles a ring tomorrow. Have checked CRC, Merlin and Madison etc without any joy (not for the price I want to pay anyway!)
i'd even think going shorter. SX/NX available in 155mm.. or even 145/152 from the likes of Vpace
Worth the money as you cant put a price on knees/hips
I'm sure there was a chap who would shorten cranks if your old ones weren't hollow tech or relieved on the back.
Might be worth trying to find him.
Worth the money as you cant put a price on knees/hips
While I would agree that shorter cranks would be more suitable (and I ride 165 as a 178cm adult) I think that statement is a bit dramatic. I was riding/racing a BMX a lot (hours a day as was obsessed with it) from age 10 - 18 and used 175 cranks the whole time. Have also ridden fixed gear for most of my riding in last 20 years and my knees and hips are still fine at 52...
While I would agree that shorter cranks would be more suitable (and I ride 165 as a 178cm adult) I think that statement is a bit dramatic. I was riding/racing a BMX a lot (hours a day as was obsessed with it) from age 10 – 18 and used 175 cranks the whole time.
perhaps you weren't pedalling for hours sat down
@faz71
What is her outside hip measurement?
She need to be huge for 165mm.
I tend to go by eye now based on seated pedalling from a shorter set but my (just gone) 11yr old is only about 5'2" / 157cm. (Not bothered measuring him but his gran is 5'1 1/2 and he's just taller than her)
I just moved him from 145mm (on his FS) to 152mm (on a new HT).
I could have gone up to 155mm at a stretch but as I use the same bike/ cranks I wanted to leave more material between his pedal holes and mine.
His BMX and the DJ are just at 170 as they are not pedalled sat down.
I'd get smaller cranks than 165mm for your daughter unless she is particularly long legged.
SJS so a range of thorn cranks that are smaller.
SPA are ace for this stuff. I wanted different ratios to the ones listed. I phoned Wednesday and and they built it for me and i had it Friday
Hopefully they have a bottom bracket for MTB chain line of that is what is need
My kids are riding on Suntour XCR Jr 152mm cranks, square taper bottom bracket but they've been flawless. They come with a triple attached but it's standard 104BCD so is trivial to replace with narrow-wide + bash rings.
About 20 quid on Amazon when we got them.
Thanks for everyone's help. Had very helpful chat with SPA and as Kilo suggested they do shorter cranks but intended more for road use with a 110 BCD which may limit chainring choice.
My daughter's old Frog 69 mtb has 140mm cranks which they sell separately (in various lenghs) for a bargain £20 but are 9speed only (current set up is 1x11).
Just had a look on Amazon at those Suntour cranks and at the moment they seem the best option.
Hope 165 cranks are really good
These any good? 140, 150 or 160
FWIW an 11 speed chain will run on a 9 speed chainring - the internal width of the chain is the same
https://kidsracing.co.uk/blogs/bikes-components
Mostly CX but do some MTB stuff too. And very helpful.
Have you measured her outer leg?
Before you go to the time/expense why not find what size is most suitable?
Plenty of 104 BCD options good to a 30T and if you want to go smaller 96 BCD
Have just ordered the cranks suggested by igm - thanks again.
I haven't measured her leg length Steve but she is about 5'2" as well, so going from what you said earlier I've gone for 150mm.
@faz ... those are a pretty good price ... and 104 BCD 😀
If you need to switch BB then the Shimano UN55's are great. (lighter than most not silly money (Ti/Carbon) and will outlast the bike.. and possibly still be around when the earth is swallowed by the sun)
@Steve - you've just answered my next question! Was looking at the UN55 - now ordered.👍
In the same boat here - got the cranks and just need to work out what axle width I need. I've forgotten all the square taper stuff I used to know.
How do you get the right axle lengths again? Can anyone enlighten me? For ref it's a Brand X hardtale frame. 135mm qr rear end. Standard stuff.
Cheers in advance!
Just checked the frame before I ordered and looks like the frame (Cube hardtail) has a press fit BB with a 90mm length shell, not a threaded one - so what size will I need?
@faz ... oops
@neilforrow
Is it for you or kids?
You can sometimes get away with a shorter axle... (frame/chainring dependent) which gives a better Q factor.
I know I managed a 113mm down to a 110.5mm but didn't know till I tried it really.
Chainline was acceptable ... but I may have mounted it outboard (can't remember)
Press fit...I'll refer you back to vpace.
They are 24mm spindle so 100% press fit compatible.
Or 155 SX/NX
Or some press fit to English BB adapter and God knows what size square taper BB.. but sounds easier to go to a 2 piece crank.
@stevextc - it’s for my lad. F’k knows what sq taper axel length to get and there is a massive range. She’ll width; easy.
Relatively expensive to just try...
@neilforrow
sorry bit of a rush ...
You can theoretically measure it and eyeball.
If you take the current sq taper out it will either have the length on or you can measure.
You can then work out how many mm you can go closer (or not) holding the cranks to the frame...
Obviously the chainring needs to clear the frame and the chainline will change a little.
@neilforrow
Does the Sheldon Brown article on chainline help or it it too out of date? Might give you a hint at where to start.
https://www.sheldonbrown.com/chainline.html
@stevextc - cheers. The old bb got tossed ages ago. Got an external bb on it at the moment with 175s hence having to go back to basics. Been a while since I’ve used the older stuff!!
@slowol - cheers. Had a ward but it’s all a bit cryptic.
Guess I’ll measure up - just want to check there wasn’t a default way of doing it
Cheers
The BB length is specific to the cranks - see for example https://www.velodrome.shop/track-chainsets/sugino-sg75-black-crankset/ and https://www.velodrome.shop/track-chainsets/miche-primato-advanced-track-chainset/ which specify 111mm ISO and 107mm JIS BBs.
If you've bought BMX cranks I guess BMXs might have a different chainline to an MTB so you'd need to adjust that specified BB length to suit.