psychologist Posted April 1, 2006 Report Share Posted April 1, 2006 Hey Guys, i've been into trials for a little while now but still dont really understand how geometry affects the ride of a bike.For instance what effect does the rise on the stem have on the bike and the bb height, how does that effect the ride?Any help would be awesome, dont leave out anything because its obvious, im dumb Quote Link to comment Share on other sites More sharing options...
joe_eyre Posted April 1, 2006 Report Share Posted April 1, 2006 (edited) Hi thereThe geometry is all to do with the design of the frame e.g. Gu's have a 60mm+ bb. this means that ur actually riding 60mm higher than on any other frames Also geometry is to do with the length from the bb to the headset and the length from the drop outs to the bb. e.i. have a longer rear end etc... I dont fully onderstand it but it doesnt really bother me. I just think of it as if i ride a frame and it feels nice its got good geometry Hehehe..Cheers joe Edited April 1, 2006 by joe_eyre Quote Link to comment Share on other sites More sharing options...
mr_gubike Posted April 1, 2006 Report Share Posted April 1, 2006 Also geometry is to do more with the angles of the frame eg: angle of the sloping down tube. Quote Link to comment Share on other sites More sharing options...
Gavyn. Posted April 1, 2006 Report Share Posted April 1, 2006 (edited) actually riding 60mm higher than on any other frames Cheers joe as far as i understand it, it is 60mm from the floor to the centre of the bb shell when the frame and forks are sat upright.if it was like you said it the gu would have a 11111111110000010001010001mm bb rise because you would have to add on the height of each frame that came out bb rise Edited April 1, 2006 by Gavyn L Quote Link to comment Share on other sites More sharing options...
the judge Posted April 1, 2006 Report Share Posted April 1, 2006 as far as i understand it, it is 60mm from the floor to the centre of the bb shell when the frame and forks are sat upright.You're right as long as the frame and forks don't have any wheels in. I don't quite know if this is what you're getting at but bb rise is how much higher the bb shell is than the imaginary line between the front and rear axles. Quote Link to comment Share on other sites More sharing options...
Krisboats Posted April 1, 2006 Report Share Posted April 1, 2006 Yeah bb rise is from the imaginary line between youre axles, or very real line if you stick a long ruler from one to the other. BB rise will also make the bike feel more responsive on the back wheel but can be almost cancelled out with longer chainstays to make the bike feel relatively normal.The headtube angle defines how responsive the front end is and a slacker angle will give a longer wheel base but will make turning slower so on a trials bike a slack head angle is good on a jump bike a tighter angle is needed for faster response between jumps.The length of your chainstays defines how the bike will pull onto the back wheel. For example shorter stays will allow the bike to leift easier and will generally make it feel more flickable where as longer chainstays will make it feel slower and hard to bunnyhop.The length of your seat-tube obviously gives you more or less clearance for sidehops.The length of the toptube will give a longer or shorter cockpit so will make the bike more suitable for taller or shorter people.As far as i'm aware thats all correct.hope it helps Quote Link to comment Share on other sites More sharing options...
psychologist Posted April 25, 2006 Author Report Share Posted April 25, 2006 Sorry forgot about this topic. Yeah what you've posted so far it awesome guys thanks alot. What affect does having short or long chainstays have? Quote Link to comment Share on other sites More sharing options...
the judge Posted April 25, 2006 Report Share Posted April 25, 2006 Shorter chainstays generally means greater control when on the rear wheel, easier to manual as well I think. Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted April 25, 2006 Report Share Posted April 25, 2006 longer chainstays allow gapping to be easier, but makes the bike feel slugish, and crap on the rear wheel.no offence to all the revell owners. Quote Link to comment Share on other sites More sharing options...
bikerboy16 Posted April 25, 2006 Report Share Posted April 25, 2006 when you have bb rise it will give you more back wheel control and help when you are getting up stuff cause it does not hit so early Quote Link to comment Share on other sites More sharing options...
poopipe Posted April 25, 2006 Report Share Posted April 25, 2006 a bike is just a big lever with an idiot on it. Anything you do to improve one thing will negatively affect something else.ie.short back end means less weight on the front end which means the front comes up easier but the bike is more inclined to loop out underneath yousteep headtube angle means quick steering but the bike is less stable- particularly at speedhigh BB means that when you're on the backwheel your weight is more centered over the pivot (rear hub) - meaning its easy to stay on the back - the bad side is that your weight is higher up which makes the bike more unstable when not on the backshort front end makes the bike more spinny and easier to lift but you lose leverage and the bike is less stableif we're talking stock there's all sorts of weird shapes and sizes going around but with mods I think im safe in saying most (not all) conform to this sort of arrangement...wheelbase: 1000-1030 ish mm (according to the manufacturers - not real life obviously)headangle: 72 ish whatsitschainstays: 360 ish mmbb rise : 50 ish mmthe only real factor to consider with a mod is how long you like itif you want a decent illustration in real life, compare the geometry on a flatland bmx with the geometry on a dirt jumper and think about what they're used for. Quote Link to comment Share on other sites More sharing options...
psychologist Posted April 26, 2006 Author Report Share Posted April 26, 2006 Ok guys thanks for your help, could anyone if possible do what poopipe did but for 24"? Quote Link to comment Share on other sites More sharing options...
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