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PostPosted: Sat Nov 10, 2018 6:45 pm 
Old School Grand Master

Joined: Mon Feb 11, 2008 9:42 am
Posts: 3117
Yes, there are, a full on race bike will have less stack and more reach (longer/lower) then your all day hack bike will have more stack and less reach (shorter/higher) and even bikes within the same broad category will vary depending on the manufacturers ideas about geometry.
So once i know what stack and reach i need, i can find out what frames will give me similar handling and fit to what i am used to, given a couple of other numbers (head angle and fork rake pretty much covers it.)


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PostPosted: Sat Nov 10, 2018 7:01 pm 
Old School Hero

Joined: Tue Aug 21, 2018 3:43 pm
Posts: 244
Location: Cambridgeshire - flatlands (the horror, the horror)
Hmmmm.....in here there is definitely rumbling of 'it all depends on the purpose of the bike' and I think that was what I was getting at in the first post - that norms seem to being taken from one bike class and then being put on another, without really tight application of what is needed in which class. If I had use the sizing chart given, I would have wound up with a bike which was too small. Definitely. This happened in the 90's where I was advised between two Klein Adroit frames, and ended up being recommended the small one....which was way too small, in the end. I built it up, put on the 140mm stems which were typical of the time, and boy did you have to watch ruts on the South Downs, or you were over the front bars in an instant. Pushing the saddle back on the rails just messed up the climbing ability of the frame, which went from excellent to pants. I did learn from this at the time, and went LOOOONG - so over to 15 inch Team Marins and Team Titanium Marins which had very long top tubes. I then ran much shorter stems (90-110) and was able to have in-line posts with the saddle nicely set in the middle, giving a great climbing rate, given the short rear triangle on these frames. They were really dialled and REAALLLLLY long frames - I kick myself losing the Prestige Team Marin which I had. Grrrr. Some friends who are a lot taller and running 'old geometry' bikes seem to have a really big problem, since proportionally their top tubes do not seem to grow enough as the sizes progress, and retailers push the saddle back on already heavily laid-back seat posts, and then whack a huge stem on. Which gives a really scary looking and inefficient setup.


Last edited by 2manyoranges on Sat Nov 10, 2018 8:35 pm, edited 1 time in total.

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PostPosted: Sat Nov 10, 2018 7:59 pm 
GOLD | PoTM | Rider | rBOTM
GOLD | PoTM | Rider | rBOTM
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Joined: Tue Feb 26, 2013 6:26 pm
Posts: 23007
Location: 54 Festive Road Winchcombe GLOUCS Yarp...
Do you want to see it? the old chestnut? the big one? yes that one, the really big one......


oh all right then.


Image

So it's still a no from me. :P


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PostPosted: Sat Nov 10, 2018 8:31 pm 
Old School Grand Master
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Joined: Thu Nov 26, 2015 7:29 pm
Posts: 4433
Location: peak district
^^^ love this, and that they actually made it :D


130/140 stems arent really long stems. If you felt like you were going over the bars then the frame was too small. The reason a Marin feels bigger is that a Marin 17.5 frame is actually a 19" frame


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PostPosted: Sat Nov 10, 2018 8:50 pm 
Old School Grand Master
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Joined: Thu Nov 26, 2015 7:29 pm
Posts: 4433
Location: peak district
surely you know what size bike you ride by now. I look at the top tube length on bikes when i buy, knowing what length is too long even with a short stem and which is too short, even with a long stem. And then the stem becomes a different addition then, one for adjusting the steering response, as opposed to trying to make a frame fit. I have always liked low frames, coming from bmx, so always go for brands with sloping top tubes.

Trail bikes like the cotic are long and low as are most trail bikes, xc bikes have different sizing, as do dh bikes, all for different reasons, they dont cross over like you say.

get to a shop or demo day and try some different bikes, but work out what you want to do with it first, then find the right fit for that.


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PostPosted: Sat Nov 10, 2018 9:11 pm 
Old School Grand Master

Joined: Mon Feb 11, 2008 9:42 am
Posts: 3117
2manyoranges wrote:
Hmmmm.....in here there is definitely rumbling of 'it all depends on the purpose of the bike' and I think that was what I was getting at in the first post
Nope, didn't appear to last time either. A 90's XC bike was designed around roadie style, as most racers were also roadies, so they liked it. I'd guess a lot of the designers were roadies too, and using roadie tubesets and roadie lugs and roadie jigs. So they weren't good at going downhill. An XC bike of 2018 is probably more capable Downhill than the earliest of the Downhill bikes (mid 90s?). Probably longer, lower and slacker. (and more travel)
2manyoranges wrote:
retailers push the saddle back on already heavily laid-back seat posts, and then whack a huge stem on. Which gives a really scary looking and inefficient setup.
Get better retailers. That's pretty much in class 101 of how to fit a bike. (and also, stop buying bikes that don't scale properly)
mkone wrote:
surely you know what size bike you ride by now. I look at the top tube length on bikes when i buy, knowing what length is too long even with a short stem and which is too short, even with a long stem.
You'd be amazed. The number of even quite high end shops and experienced riders STILL think seat tube length/stand over is the be all and end all of frame sizing........


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