mountainfun Posted January 28 Share Hi My kid has long cranks on his bike (175) and I'm keen to shorten to 140-145. Any suggestions whom to contact? I previously posted on my carbon cranks needing shortening and can happily say that I've crossed over to shorter alu ones (RaceFace Atlas) and am super happy! Thanks for all the comments on that thread, really appreciated the feedback. Best JL Link to comment Share on other sites More sharing options...
Jewbacca Posted January 28 Share I did a set of Lyne 1st gen alu cranks. Measure, mark, measure, mark.... cut. Reduced them from 175 to 145. You need a drill press and some one who has a pedal thread set, which will be a lot of bike shops and a grinder. You need to make sure you are using solid alu cranks, not shimano hollowtech II or other hollow cranksets for obvious reasons. It's not a big job. If you have a local engineering shop, they could do the drilling for you in a matter of minutes but the pedal thread size and the reverse thread die in that size is even less common, so phone around your area for a theadset. If you do the shortening and the drilling, cutting the threads in the workshop will only take a few minutes, pay them for their time and tools use. If you want someone to do it for you, my advice would be to contact Kevin Wilkinson, used to be a bike tech at BMC, now has several engineering/fitting/turning containers with which he does on site work. He is based daily at the airport industria. DM me and I can send you his number. tjommies3, Nickyr, Prince Albert Cycles and 3 others 4 2 Link to comment Share on other sites More sharing options...
DJR Posted January 28 Share Agree on Kevin Wilkinson - 082 466 4565 (been a while since I needed him, but hopefully the number is still functional. Otherwise Google is your friend.) He's done all kinds of small precision engineering stuff for me on a number of bike builds. Always came out great. Nice guy too. Edited January 28 by DJR mountainfun, Sepia and Jewbacca 3 Link to comment Share on other sites More sharing options...
quade Posted January 28 Share Following this thread Is there a rough guide on age/height and crank size ? My 12 year old is riding 175's and was looking at shorter options Not sure how small they go off the shelf ? Link to comment Share on other sites More sharing options...
Jewbacca Posted January 28 Share 55 minutes ago, quade said: Following this thread Is there a rough guide on age/height and crank size ? My 12 year old is riding 175's and was looking at shorter options Not sure how small they go off the shelf ? I don't think there is an age formula, more a height/inseam fitting that 'should' be considered by everyone on a bike. Most people on 175s should be riding shorter cranks. Thanks to E-bikes, anything from 150mm can be had off the shelf these days, but they are pricey. A set of 2nd hand shimano deore solid alu cranks can be shortened for relatively cheap The Lyne or SRAM 3 bolt cranksets are also a really good option as you can fit a 28 tooth narrow wide DM chainring while a 30 is the smallest you can go with a 104mm spider. Link to comment Share on other sites More sharing options...
Kuys Posted January 28 Share My kids (7 and 9) have these cranks on their bikes in 140mm https://prevelo.com/products/heir-direct-mount-crank?variant=32105296167014 uses standard Shimano BB and has SRAM direct mnt interface so they can run 28t chainrings. Jewbacca 1 Link to comment Share on other sites More sharing options...
mrcg Posted January 28 Share Sorry for the highjack. Have a set of carbon cranks (left crank) where the pedal insert has been stripped. Would you guys recommend a helicoil insert? Needs to be reverse thread. Bike shop didn't find anybody who could provide a reverse thread helicoil. Any recommendations for who could assist? Much appreciated Edited January 28 by mrcg Typo Link to comment Share on other sites More sharing options...
Prince Albert Cycles Posted January 29 Share 6 hours ago, mrcg said: Sorry for the highjack. Have a set of carbon cranks (left crank) where the pedal insert has been stripped. Would you guys recommend a helicoil insert? Needs to be reverse thread. Bike shop didn't find anybody who could provide a reverse thread helicoil. Any recommendations for who could assist? Much appreciated Try Nils at Woodstock Cycles mrcg and DJR 1 1 Link to comment Share on other sites More sharing options...
DJR Posted January 29 Share 28 minutes ago, Prince Albert Cycles said: Try Nils at Woodstock Cycles Nooooooo, don't go near that place and don't talk to Nils and do not use words like Eroice, Classic or Tour of Ara! Every time I go there to buy something small, like bartape, I see something else that I MUST have. A frame for instance.........and then it starts another bike build. Or, if I really resist, I buy something innocent, like an old derailleur.......and then it starts another bike build. Even just buying a saddle inevitably leads to another bike build. I tell you, that is a dangerous place. My house is overflowing with bikes, I think if I get one more skelmpie, my wife is going to kick me and all my bikes out! Ps Y'all seen my tongue firmly in my cheek? Edited January 29 by DJR Nickyr, Chadvdw67, BuffsVintageBikes and 6 others 1 8 Link to comment Share on other sites More sharing options...
Jewbacca Posted January 29 Share 8 hours ago, mrcg said: Sorry for the highjack. Have a set of carbon cranks (left crank) where the pedal insert has been stripped. Would you guys recommend a helicoil insert? Needs to be reverse thread. Bike shop didn't find anybody who could provide a reverse thread helicoil. Any recommendations for who could assist? Much appreciated Nils might still have a few inserts. There is a kit you buy with standard and reverse thread sleeves that are also threaded on the outside. So you drill the original hole out, tap with the supplied tap and then epoxy in the threaded insert. New pedal threads in 10 minutes! You can order the kit off E-bay for a few hundy too mrcg 1 Link to comment Share on other sites More sharing options...
mountainfun Posted January 29 Share Thanks, it's incredible how useful this community is! Amazing!! Now smiling!! Link to comment Share on other sites More sharing options...
bebnin Posted January 29 Share can agree with all the above, I've shortened some al cranks doing exactly this (drill & tap with the right tap set) - if you're in woodstock often, let me know and I can help you out. Link to comment Share on other sites More sharing options...
quade Posted January 29 Share 13 hours ago, Jewbacca said: I don't think there is an age formula, more a height/inseam fitting that 'should' be considered by everyone on a bike. Most people on 175s should be riding shorter cranks. Thanks to E-bikes, anything from 150mm can be had off the shelf these days, but they are pricey. A set of 2nd hand shimano deore solid alu cranks can be shortened for relatively cheap The Lyne or SRAM 3 bolt cranksets are also a really good option as you can fit a 28 tooth narrow wide DM chainring while a 30 is the smallest you can go with a 104mm spider. Thanks This link seems to have some interesting info https://thebikedads.com/kids-cranks/ Jewbacca 1 Link to comment Share on other sites More sharing options...
mrcg Posted January 29 Share 15 hours ago, Jewbacca said: Nils might still have a few inserts. There is a kit you buy with standard and reverse thread sleeves that are also threaded on the outside. So you drill the original hole out, tap with the supplied tap and then epoxy in the threaded insert. New pedal threads in 10 minutes! You can order the kit off E-bay for a few hundy too Thanks for the details. Question: is the epoxy strong enough for such a high torque spot? Anyway, will hit up Nild and see what he says. Thanks again Link to comment Share on other sites More sharing options...
Jewbacca Posted January 30 Share 7 hours ago, mrcg said: Thanks for the details. Question: is the epoxy strong enough for such a high torque spot? Anyway, will hit up Nild and see what he says. Thanks again Bear in mind the epoxy is being used more as a thread lock than anything else. No more torque on those threads than there are in your pedal spindle threads which you definitely don't epoxy in place...... I have done thousands of KM in one of these on my BMX, which is also home done shortened cranks, so it definitely works and is neater and more user friendly than a helicoil when you change pedals. Link to comment Share on other sites More sharing options...
DJR Posted January 30 Share 8 hours ago, mrcg said: Thanks for the details. Question: is the epoxy strong enough for such a high torque spot? Anyway, will hit up Nild and see what he says. Thanks again Locktite is just an epoxy. And remember that most modern airliners are held together with epoxy these days............enjoy your flying. Link to comment Share on other sites More sharing options...
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