Tandem Cycling - Child stoker - can I have holes drilled to shorten the cranks?

Just purchased my first tandem, a 1996 Cannondale MT1000. The frame is a XL-M (22"/18"). The stoker is my 8-yr-old daughter (9 in one month), who is 4'-5" with a 25" inseam. Replacing the suspension seatpost with a regular one and cramming it all the way down, my daughter can reach the pedals on the downstroke. Problem is, on the upstroke, with the 175mm cranks, her legs go pretty high. I am concerned about the range of motion.

I've checked into crank shortners and cannot find them locally nor online * (postings see to say they cost $100). One LBS told me all they could do is put on a child stoker set, at $210 + tax, which is more than 1/3 the price I paid for the whole bike! I have decided against the child stoker kit route because of the cost, I think it will make the bike that much more top heavy, and she pretty much fits the bike, I just need shorter cranks.

So as the title says, how easy is it to find someone to drill another set of holes in the rear cranks and tap it for the pedals? Who normally does this type of work? Is it possible to find a mechanic at a LBS who can do this, or do I need to go somewhere else?

The cranks are Sugino Fuse 300 Tandem, 28/38/48 teeth, and being from 1996, I assume they are solid and not hallow. They have a slight curve to them, but otherwise seem to be a uniform size. (I can take a photo if you want to see them.) I was thinking if drilled 30mm closer to the BB that would give an effective crank length of 145mm, which should fit my daughter rather well. Plus, when my wife wanted to ride as stoker, it would be a matter of simply moving the pedals.

I plan to call a few bike shops on Monday, but would like a little feedback before I do.

*EDIT: Apparently I didn't search the web well enough, because I did end up finding them online in the $90 range, of all places, Amazon.com!

Picked mine up on ebay for about $60.

Some companies will drill additional pedal holes, it depends on the width of the crank.
http://www.highpath.net/cycles/special/shortcranks.html

I have done this on two different sets of cranks. The first was a child stoker kit for my 2.5 year old, where I wanted to shorten even the kid size cranks. I took those cranks off and, mounted them in a vise on a mill, and drilled two extra sets of holes. I found my local bike shops were not interested in doing the drilling for me. However rather than tap the holes myself, I brought the drilled out cranks to my local bike shop and they used their taps to tap the holes. I would have done it myself, but I did not want to buy the taps. I think I paid the LBS $25 to tap the holes I drilled. The tap sets cost about $40 on line, so you could own a set and do the whole job yourself. Mine worked out great. Recently my 9 year old made the move from the child stoker kit down to the regular stoker cranks, and I was in the same boat as you. In this case, I did not feel I wanted to tear apart the drive train, so I carefully made a guide and brace and drilled the cranks while they were still on the tandem. This meant I used a hand drill, and that is a bit hard to do since the standard holes are over half an inch, before tapping. I did manage, and the same shop tapped those holes for me, but it was much harder. Probably I should have taken the crank arms off the bike in retrospect. The other idea that came to me later was that many kids bikes use 1/2" pedals rather than 9/16, so if I had planned on that, I would not have needed to drill the hole out even to 1/2" and that would have been easier. Another idea that I did not try would be to buy MKS EZY PEDALS, such as used on folding bikes, which are especially easy to remove, with no tools, so you can pop the pedals between the smaller and larger diameter circles on the cranks.

Hope this helps! Clearly a local frame builder could do the whole job for you, but my experience is that regular bike shops can tap the holes if you find a way to drill them.

I do think that if you have it done you will be happy with the results. I have been.

DMT

Santana Arriva, Cannondale Road Tandem, Santana Quad

Thanks for the replies.

LWaB, the website you link is in the UK; I'd rather stay local, or at least in the states. Shipping costs and times would be a big negative. I'm a novice mechanic and would not be real confident even taking the cranks off my bike! :o

tie dye, thanks for your comments. I don't have a vise so wouldn't want to do any drilling myself. I do appreciate you sharing your experiences.

I ran across a website for a shop called House of Tandems in Spring, TX, about a 50 min drive from me. Obviously selling tandems is a high dollar business, but I'm just a guy on a shoestring budget with a used tandem trying to find a low-cost solution. The shop owner was very courteous and worked with me. They carry the crank shortners, for $115. :( I asked about drilling new holes and tapping, and he said he does that, and assuming my cranks were good to drill into, that he could drill and tap them for me for $45. :thumb: Since the tap sets are $40, this is a heck of a deal in my book. The owner suggested I bring my daughter with me, so I plan to make an appointment for next Saturday. (Don't want to drive clear across Houston in traffic during the week and double my travel time). I'll post back when the job is done.

LWaB, the website you link is in the UK; I'd rather stay local, or at least in the states.


Yes, just an example of a company that does re-drill cranks, as you asked. I haven't used a USA-ian company for that work, not living in that part of the world.

You could drill holes in the crank arms, but I really don't like the idea.

Da Vinci (and maybe 1 or 2 others) manufacture special cranks with 3 or 4 sets of holes, but the arms are much stronger to take into account the weaknesses created by the holes. Regular cranks don't have that feature and are weaker in the centre and they are near the end. You will probably be OK with one set of holes where your daughter needs them (say at 135 mm), as long as she uses cranks that size. But they day she is 11 or 12 and definitely needs full-size cranks, your cranks will be too weak to do the job. And if you need to use the stoker position with an adult, the cranks almost certainly will fail.

Costwise, the crank shorteners are not horrifically expensive if you figure that it would cost you 40-50 $ to have a set of holes machined in the arms. Add to that the cost of new crank arms in 2 years.

You might check out Persion Tandem
http://www.precisiontandems.com/catframepart.htm (http://www.precisiontandems.com/catframepart.htm)
Alloy Cranks 135mm w/alloy ring 38T Black - 110 bcd (http://www.precisiontandems.com/cat_pics/crchildstokerblack135mm.jpg) $70.00

Ages 3.5 and Up - Cranks only
CRANK ARM SHORTENERS - RIDE-2
Crank Arm Shorteners, shortens by 24, 41, 59 or 76mm (http://www.precisiontandems.com/cat_pics/crrd2shrtnr.jpg) $115.00

For Sugino, Race Face, Shimano Deore & XT Cams tighten against arms, 308g/pr

Crank Arm Shorteners for Ultegra, Dimension, MegaDrive (http://www.precisiontandems.com/cat_pics/crrd2shrtnr.jpg) $115.00
As narrow as 22mm and Up to 42mm wide cranks

Also Tandems East has some CHILD CRANK SHORTENERS
http://www.tandemseast.com/parts/cranks.html (http://www.tandemseast.com/parts/cranks.html)

But they day she is 11 or 12 and definitely needs full-size cranks, your cranks will be too weak to do the job. And if you need to use the stoker position with an adult, the cranks almost certainly will fail.

Thanks for that. I went out and looked at my cranks again, and they get narrower just past the pedal, so it would not leave a lot of metal if a new hole were drilled in the crank. I am not going to follow up on the drill a new hole idea.

I think I'll continue my quest for crank shortners, or may just leave her on the 175mm cranks.

You can try House of Tandems just north of Houston in Spring. http://houseoftandems.com/page.cfm?pageID=62

Ric may have some older cranks as well.

Sorry, didn't catch post #5 above.

I bought the Ride2 crank shorteners online last year from Edina Bike in Minnesota. Their price was (and still is) the lowest I found at about $90.

Edina Bike's Website search for RIDE2 (http://edinabike.com/page.cfm?PageID=62&action=list&searchtype=search&keywords=ride2)

www.bikesmithdesign.com he is the industry go to guy for crank shortening, at least in the recumbent world. He shortened some 170mm Shimano hollow tech cranks down to 147mm. Worked and looked great very reasonable price wise. He will be able to tell if your cranks are good canidates for shortening (enough meat left on the arms). Or he may have an alternative solution for you. his name is Mark.

www.bikesmithdesign.com he is the industry go to guy for crank shortening, at least in the recumbent world. He shortened some 170mm shimano hollow tech cranks down to 147mm. Worked and looked great very reasonable price wise. He will be able to tell if your cranks are good canidates for shortening (enough meat left on the arms). Or he may have an alternative solution for you. His name is mark.


+1

my daughter is at the last hole on our crank shorteners. i will check her this week to see if we can remove them altogether. then my used pair are for sale! pm me for price, shipping, etc.

Pat

just but the extenders I did last year for about $90.

Thanks for all the continued replies. Pat, I sent you a PM.

As for cutting the stoker cranks on the tandem, I don't want to do that as (1) my daughter will grow and (2) my wife may ride stoker on this bike on occasion. I'm still following up with the crank shorteners.

BTW - my daughter and I were able to ride the tandem the past weekend and I can tell we are going to have a lot of fun on this thing.