1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Supergranny?

Discussion in 'Bicycle Mechanics and Repairs' started by Over The Hill, 24 Feb 2008.

  1. I have a Felt F85 racing bike with a 3 ring chainset. smallest is 30T.

    I got this bike after a year on a Mountain Bike with road tyres. While it is great in many ways I am not as happy with it going up a steep hill as I was with the Mountain Bike.

    I tend to be happy chucking revs at the hill but am old and have dodgy knees so do not stand up in the pedals for hills.

    My question is, how can I best get the Felt to be more like the mountain bike for a hill?

    Can I change the small ring for something smaller? or can I change the chainset or all the rings to go down a bit in size? (Perhaps swap for a mountain bike range??)

    If I do mess around with the rings or chainset will I still be ok with the gear change or will I mess that up? I am thinking with smaller rings it may need to be moves closer.

    I am fairly OK on mechanical things but have not had much experience with bikes.

    I got the Felt second hand and so do not know much about it. Taking it apart today it has a square stem that the chainset fits to. and five allen bolts to hold the bigger two rings in place and then a second set of five to hold the smaller ring.

    From a spec I have found I think I have:
    Crankset
    Felt aluminum, 30/42/52 teeth
    Front Derailleur
    Shimano Sora Triple, clamp-on


    I guess the other way is make the back ones bigger rather than the front ones smaller.

    I am happy to lose a bit of the top end (dropping top gear down a bit) as I rarely get up to that sort of speed. I use it for leisure cycling and plan a 100 mile run but nothing against the clock.

    Has anyone got any advice on the best way to do this????
     
  2. RedBike

    RedBike New Member

    Location:
    Beside the road
    Your crankset probably wont take anything significantly smaller than a 30tooth chainring.

    The easyist option will probably be to fit a MTB cassette to the rear. (You may need to swap the rear mech depending on which cassette you go for / what you've currently got)

    BTW, the F85 is quite a high end bike. It shouldn't have the like of Sora parts on it as standard.
     
  3. simoncc

    simoncc New Member

    You could also swap the chainset for a touring chainset with 46/36/26 teeth. This should work with a road front changer with STI levers. Whatever you do it will be impossible to get your gearing down to MTB levels on a STI road bike. I've often wondered why Shimano don't produce a lower geared set up for road bikes suitable for the less fit and the not so young. In the summer I see dozens of middle-aged men struggling on flash road bikes that are too highly geared for them.
     
  4. vernon

    vernon Harder than Ronnie Pickering

    Location:
    Meanwood, Leeds
    There's several avenues that you can explore with the gearing.

    I have a Sora group set on my road bike and the front chain rings are more or less the same as yours. I looked at the possibility of getting a smaller granny ring and found that they were not available. I had considered than fitting a moountain bike chain set like the one I have fitted on my Dawes Galaxy - 48-38-28 Shimano Deore and sometimes I fit a 26 if I am touring in very hilly areas.

    In the end I fitted a 12-28 rear cassette which does the job more or less to my satisfaction. It's cheaper and my rear mech could cope with the gear diameter of the 28 tooth.

    You could go the whole hog and fit a MTB cassette though you will have to fit a new rear mech. The indexing will be the same as a road cassette. I don't think that indexing is preserved if you change to an MTB chain set at the front which could make things difficult if you have STI levers.
     
  5. Steve Austin

    Steve Austin The Marmalade Kid

    Location:
    Mlehworld
    I would try a 12-27 cassette first. No need to change mech or anything else so its worth trying this.
    a 30-27 gear should get you up everything on the road
     
  6. vernon

    vernon Harder than Ronnie Pickering

    Location:
    Meanwood, Leeds
    Not if you are as porky as I am :biggrin:
     
  7. simoncc

    simoncc New Member

    MTB chainsets these days are 42/32/22 or something similar. These won't work with STI levers. Touring chainsets like Shimano Deore or Stronglight Impact do, and these are usually 48/38/28 or 46/36/26.

    One way to get MTB gearing is to ditch the STI lever for the front mech, fit a conventional brake lever, a bottom pull MTB front changer operated by an old-style down tube shifter or a bar end shifter, and an MTB 42/32/22 chainset.

    If only Shimano would make an STI brake lever that correctly shift MTB chainsets.
     
  8. andrew_s

    andrew_s Veteran

    Location:
    Gloucester
    A standard road triple chainset like you have will be 130/74 bcd, and will go down to 24/38/48 smallest chainring sizes (with the 24 & 38 the smallest that will physically fit around the bolts).

    Are you 10-speed or 7/8/9 at the rear?
    Mountain bikes haven't gone 10-speed yet, so the largest cassette will be 12-27T.
    Fitting an MTB cassette will allow up to 34T, but for 34T or 32T you will also need an MTB rear mech, and 30T will require careful fiddling to use the existing road mech.

    You may well find that it's just about as cheap to buy an entire new chainset (eg Stronglight Impact) as it is to buy a set of 3 rings. However, a new chainset may need a different length bottom bracket.

    The trouble with STI shifters and compact MTB chainsets (42/32/22) is that you have to use a road front mech to match the STI shifter, but that all road front mechs are designed for 48-53 big chainrings, and 42 is just too different for the mech to work well.
    MTB front shifters pull more cable than road (STI) front shifters, so if you try an MTB mech it won't move far enough to make the change.

    I'd suggest 48/38/28 (or 46/36/26 if you get a new chainset) and an MTB rear mech and cassette (12-32)
     
  9. Thanks for all your responses guys!

    Yes I am that fat middle aged bloke struggling along - I did not know the bike was "High End" I just could not afford a new one and it is silly buying entry level stuff secondhand. It was £140. All seems OK on it and it polishes up nicely. Looks like new. Touring bike would problaby be more my type but they are not around so much second hand and go for a lot of money. As you have guessed I do not really know what I am doing.

    I have had a look at the bike and it has Sora on a lot of the parts - but not on the gear shifters Rear one says Shimano RD3300.

    Thanks for your advice on the options and on your help with what will fit or not with the STI shifters. I find them a bit odd but am getting used to them. Other info on the bike I missed off (just been to the shed to look)....

    I only have spec from a web site for a 2002 model but I do not know how old the bike is. It only has 8 cogs on the back but they are 12-23 teeth.

    So options I have are..
    I can go for a touring chainset which will get me down to 28 or 26 from the present 30. Any more and I have to lose the STI
    and/or
    change the rear casette from the present 12-23 to 12-27 (I think the concensus is that it will go on without changing anything else. or if I go bigger I have to start swapping other parts.

    The mountain bike was a Half***s special supposed to be road/hybrid thing so it probably is not too highly geared. I will check the difference between the two bikes tomorrow to see how far out they are over a pedal turn, that should give me an idea of how much I need to get out of the Felt.

    I got up Ditchling Beacon on the MTB last year in the L2B and would really hate to now have to get off my bike for a hill.

    Thanks again guys.
     
  10. P.H

    P.H Über Member

    Yes, but the only part you'll need to change is the rear derailleur and they're easy to swap and cheap. Less than £20 gets you a Deore one which is probably an upgrade over Sora.
    Changing the rear to 11-32 and leaving the front alone will reduce your bottom gear to the equivelent of about 3rd gear on a typical MTB. The lighter bike and higher pressure tyres will probably compensate for the loss of those two gears.
    When you come to do it the Park Tools website has simple clear instructions;
    http://www.parktool.com/repair/readhowto.asp?id=64
     
  11. Steve Austin

    Steve Austin The Marmalade Kid

    Location:
    Mlehworld
    P.H. talks sense.
    but i would still go for the 12-27 and gurn oop them hills
     
  12. TheDoctor

    TheDoctor Man-Machine Staff Member

    Location:
    Stevenage
    Using standard Sora triple gears I am successfully running 24-38-48 on a 13-26 chainset. Honestly, that's silly low gears. I can pedal quite happily at 2 mph (except for a bit of wobbling!)
    As other posters have said, 24T is as low as it goes on 74PCD or road triple inners. Rings available from Spa or byercycles among others. Alloy ones will be lighter than the steel Sora rings too.