I bought an old mountainbike from my dad and while riding it recently, a branch hit one of the gears of my crank set. The gear is now slightly bent and this has been causing the chain to come off when it's on that gear. I brought the bike to a repair shop, they kept it for two weeks, then told me they couldn't find a replacement for the crank set. I brought it back home and couldn't find it online either but that's because I have no clue what I'm searching for! The guy was talking about a 12mm something something?
Last week I went to Decathlon and they gave me a crank set that does fit.. but the gears are 1 cm farther away from the bike than on my old crank set. The new gears are flat, but the old ones have a curve towards the bike which puts them closer to the bike. I've tried adjusting the wire thing (derailleur?) but it barely goes out far enough to hover over the biggest gear, but not far enough to actually push the chain on. The space in between the three gears of the new crank set is equal to that of the old crank set.
Old crank set specs: cyclone precision al7, 3 gears, 41?/34/24
New crank set specs: Miranda 175, 3 gears, 44/32/22
Other specs: it was a bike bought from Aldi like 10 or 15 years ago. It says the brand is Curtis. It's got 3 front gears and 8 back gears.
Questions: what do I search for online to find this? What do I do if I can't find a replacement? Should I just buy a new bike at that point?
PLEASE HELP! I haven't exercised for 5 weeks and I can feel my spirit slowly fading.
Help! Searching for a crank set, haven't been able to ride my bike for 5 weeks, going crazy!
byu/iliveforhugs inbikewrench
by iliveforhugs
12 Comments
I would have just bought another cheap bike on about day two of your experience. unless you have a storage deficiency, I highly recommend just getting another bike. fix this one too if you want, but don’t let your riding practice wait.
Looks like a Shimano FC-TY501… Just order the Shimano it’s dirt cheap and looks like it would fit
https://preview.redd.it/nzeunqxeia2g1.png?width=1440&format=png&auto=webp&s=45f736ea15f5ce379b9964adb02c15b3244a5be2
> the gears are 1 cm farther away from the bike than on my old crank set
You need a bottom bracket that is approximately 20mm narrower than your current one.
Go to the bike shop, ask them to check to length of the bottom bracket spindle. Once they’ve done that, tell them to get a bottom bracket with a spindle that works with the Miranda crankset. Basically a shorter BB is what is needed. My guess is that you have a 121mm or a 118mm BB, when you need a 110mm or 107mm, possible even a 103mm.
Go take a look here, this will give you a much better idea of what you’re looking for.
https://www.sheldonbrown.com/bbsize.html
The new crankset likely needs a shorter bottom bracket spindle. Check in with the Bike Shop again (or a bike shop, I don’t know Decathlon sorry) and explain the issue. They should be able to sort you out.
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BTW my guess is that the shops are you are going to aren’t very good with older bikes.
It is likely difficult to replace a crankset that is 20-30 years old with something new, but a vintage shop dialed into used parts should be able to find a crankset, or least be able to evaluate exactly what you need.
When you went to Decathlon, you should have left the bike for them to install a new crankset. It’s the perfect place to take a crap bike, which is what you have. Take it there and see if you can get a refund on the one that doesn’t fit.
A cheaper and easier fix could be to un-bend the chain ring on your old crankset.
However your mileage may vary considering it’s not possible to remove the chainrings on the old set.
[relevant info](https://www.sheldonbrown.com/straighten-chw.html#:~:text=Bent%20chainrings%20can%20sometimes%20be,will%20often%20do%20the%20trick.)
You may want to consider if u want a power meter. There are some cranks that are as good and light as Ultegra, then you could get Ultegra or an equivalent SRAM set of chainrings.
You may want to consider if u want a power meter. There are some cranks that are as good and light as Ultegra, then you could get Ultegra or an equivalent SRAM set of chainrings.
Where are you ? I have a bin full of doubles off old racers and triple crank sets from hybrids and mountain bikes. You are welcome to pick out a set for your bike.