Advice frame sizing

Discussion in 'Mountain Biking, Trials and BMX' started by postman, 10 Jan 2008.

  1. postman

    postman Legendary Member

    Meanwood ,Leeds
    My mate brought his new bike to show me.Revolution Cullin Disc,22'' frame.I am thinking of investing in an off road bike.But i am big 6-4 and 16st 7lb.34'' inside leg.So i sat on it up went the seat post twice.But what a funny feeling.Could not extend leg fully when on the down stroke.I ride a Dawes Galaxy 64cm normally.Beautiful bike.I don't know if there was any more length spare in the seat post.wWe took some photos so i could see myself.My wife said i looked as though i was riding a kids bike.It looked stupid.Is there a bike out there that will look normal and i can extend my leg.Any suggestions welcome.I am going to look at Mongoose next or a Fisher 29er.
  2. ratty2k

    ratty2k New Member

    29er would be a good bet. I ride one (I'm 6ft) and ride a 19" On-One 29er. But as always, try before you buy.
    Whatever you do, dont let people put you off the idea of a 29er, some people just cannot admit that it may be a good idea. Plenty of people have opinions of them without ever riding one. Ignore them, I LOVE mine! I sold a little wheeled On-One456 that I loved to get the 29er.
    Mines fitted with Rebas, handbuilt Halo wheels and full Sram X9 gearing. I now ride this all the time and my Trek 5" full sus is just gathering dust in the garage.
    Check the MTBR 29er forum and you'll get far more info about 29ers.

    this is my 29er
    A few things have changed, its now sporting mudguards (Cycraguard) and the handlebar and stem havebeen changed. One thing about 29ers is a high bar, I'm running an inverted 6deg stem and flat bars. That brings it to the same height as my other bikes.
  3. fisha

    fisha Über Member

    in terms of mountain bike . . . i'd advise against trying to get a frame with as tall a top tube as you would get with a road bike.

    Its perfectly common / deliberate for mountain bikes to have heavily sloping top tubes. Basically for nads-clearance. It also helps moving the frame around underneath you out on the trail. I remember as a kid, i was pushed to go for 20" mtb frames and the like .... they were too tall for me. Now 18" and 19" frames are the way forward. That extra bit of clearance bewteen the legs has come in handy a few times. compared to a road bike, yes, they look like small frames, but they aren't really.

    You can get long seat tubes. Your pals should normally come with a minimum insertion line marked on the seatpost.

    i quite often run bikes with long seat posts - these are some old pics...


  4. 02GF74

    02GF74 Über Member

    the old rule of thumb:
    1/3 height or inner leg measumen less 10 inches = road frame

    subtract 6 inches = mtb frame

    ... but wit the advent of extended seat tubes, it can be hard to figure out the frame size.... so look at horizontal top tube length.
  5. OP

    postman Legendary Member

    Meanwood ,Leeds
    Been down to Chevin Cycles today.Sat on acouple of bikes.Think i have seen which one i like.
  6. ratty2k

    ratty2k New Member

    Do tell!!
  7. Steve Austin

    Steve Austin The Marmalade Kid

    yeh! What you gonna get?
  8. bonj2

    bonj2 Guest

    too long seat tubes are just wrong. You shouldn't be able to 'extend your leg fully on the downstroke'. it will be a weird feeling if you're used to riding a road bike, but if you just try to make it feel the same as your road bike you won't be getting the most out of it.
    With mtbing, you often want to have it higher when going uphill to get more purchase on the downstroke, and drop it down on the descents so you can get your weight back by getting your arse over the back wheel and the saddle won't be in the way.
  9. ratty2k

    ratty2k New Member

    Seat post sticking out can vary due to frame design tho' some frame have a very low standover height which means the seatpost is sticking a long way out.
    I disagree partly with "you shouldn't be able to extend your leg fully on the downstroke" as again it depends on the terrain.
    I still set the saddle height the same as on my roady (relative to the pedal) and it rarely drops, unless the trail gets really steep downhill, and then I drop it around 3 inch or so.
  10. Steve Austin

    Steve Austin The Marmalade Kid

    Ratty, you are confusing Bonj's opinion with common sense and well thought out advice. Bonj, you are once again talking nonsense.
    A seatpost for roadbikes, commuters, MTB's, in fact any kind of bike should be set up in exactly the same way, ie with your leg just off full extension at the end of the stroke for it to be at its most efficient.
    'IF' you set it up shorter, thats fine, BUT you are going against the norm and setting your bike up differently for personal preference. There is nothing wrong with this, but it is not what i would advise anyone new to cycling to do, as it is BAD advice.
  11. ratty2k

    ratty2k New Member

    :wacko: Fair enough not gonna argue with the bionic man! I must admit to reading Bonj's post and sort of thinking "whaat?":biggrin:
  12. RedBike

    RedBike New Member

    Beside the road
    Bonj is half right. When the going gets rough it is advisable to drop the saddle an inch or two. However, generally this is only on descents where you don't really pedal seated anyway.

    Assuming we're talking cross country riding I would ignore all that rubbish about not setting it up like your road bike. Pedaling around with your knees touching your chin is just making things harder for yourself.
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