0

I have a Marin Bolinas Ridge 7.1, I am not happy with the front large chain ring size, I mainly ride on the road, and have an extremely limited budget. I would take it to the LBS, however, I believe that would cost at least an hours time just to find out what it is that I have.

More so than anything, I am trying to find out the specs as the ones on their website only list it as forged. I have determined that it is a 110 BCD with a tapered square. An email to the company revealed that they are not sure what is in it, and possibly riveted chain ring(s). (Bolinas Ridge 7.1 ). I also do not have the tools to pull it apart for a better idea of what I should be looking for. If anyone has changed one of these I would like to find out a lot more.

edit- original teeth are 42, i was looking to go either 48 or 50.

p.s.I have since learned that it should be a regular square taper, so I will be getting another crank. At that point, I should be able to figure out the ring.

Thank you for your interest.

  • 1
    It would greatly help if you could post the photos of the front crankset with the close-up on how the chainrings are mounted. Also - do you want a larger chainring or the smaller one? I suppose the former, but please, clarify. – Mike Jul 6 '18 at 9:10
  • 1
    How fast are you riding it? The site you linked to claims 11-34/24-32-42 gears, at 90rpm cadence thats ~45km/h top speed. – Klaster_1 Jul 7 '18 at 6:14
  • Klaster is right - sounds like you're mashing rather than spinning. Once you've worn out the chainring then consider if you want a larger one. Note that the grannie 24 could be too small, and you risk not having enough total capacity on your bike. – Criggie Jul 7 '18 at 8:07
1

Square taper cranksets are common, you can find used ones or new ones fairly cheaply with either mountain (~42t) or road (~48-52t) chainring sizes.

Some Considerations for Switching from Mountain to Road Crankset:

number of gears

Mountain cranksets generally have three gears and road cranksets usually have two. To switch to a road crank with two gears, you can just adjust your front derailleur, including the limit screws, position & cable tension, and only use two gears of your three-speed shifter.

derailleur position

To accommodate the bigger chainring size, you will need to raise the derailleur on the seat tube so that it is still 1-3 mm away from the outer teeth while shifting. You will probably also need to tighten the low limit screw quite a bit, as there is no more very low gear. Finally, you will need to reset the cable tension. Depending on how much you moved the shifter and the condition of the cable, you may need a new front derailleur cable to make this work, but that's a cheap upgrade that is usually worth it just for the sake of reducing friction when you shift.

chainring clearance

One thing you will need to be careful of is that there is enough clearance between the chainstay (the tube parallel to the chain) and the chainring. If it's pretty close to the 42t chainring now, it might not fit the larger chainring (without, that is, extending it with a longer bottom bracket, but that raises additional complications with the chainline, i.e., you want your chain to run as straight as possible). But, it might fit just fine, in which case that would be a pretty easy swap to make.

other considerations

If choosing a used crankset, make sure to find one that does not have any visual wear around the teeth (should not have an asymmetrical tooth shape) or the inside of the square taper. There should be no apparent wear in either of those places or it will lead to problems fairly quickly. Otherwise there are lots of good used options and new options in the sub- $50 range.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.