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Frame Geometerys


Mr Motivator
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Ok, dont really know how I'm going to start this so I'll just get on with it..

Chainstays: Back in the day when trials was ridden on XC bikes the stays would have been around 410mm, nowadays they are mostly 380, 375, 365mm. Having short stays makes it great to get up on the backwheel and control when your up there, but I think it also has some major disadvantages. I think slightly longer stays of around 390 or 385 are more benificial for gaps and ups as they give you more leverage.

BB rise: Again, back in the day, we were looking at -20bb, now on most frames we see +10, +20, +30, +50, +80. This, I feel, has a great advantage for control on the backwheel and makes everything feel smaller as your up higher, but I also think it has some major disadvantages, such as you cant drop the front as much in gaps, so you loop off, the fact that it makes the bike ride shorter so you can end up being more hunched on a bike with a longer wheelbase.

Headtube angle: 71 or 72 seems to be the most popular, but why? To make the bike FEEL shorter yet RIDE longer, hmm is this a good thing? I dunno, but I think steeper angles would have more advantage, they would bring the backend up quicker in sidehops, ups to front wheel etc.

Wheelbase: Short = flicky, long = more control for static power moves. Cant really say much more for wheelbase to be honest.

So I wrote this kinda quick, but maybe you understand?

All this might sound silly but I recon there is truth in it.

So, MY ideal frame would have to be;

Wheelbase: 1065mm

Head angle: 73.5deg

Chainstays: 390mm

BB rise: +5mm

OR, you could just get on a bike and go ride and not worry about all this tripe B)

Sam

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Headtube angle: 71 or 72 seems to be the most popular, but why? To make the bike FEEL shorter yet RIDE longer, hmm is this a good thing? I dunno, but I think steeper angles would have more advantage, they would bring the backend up quicker in sidehops, ups to front wheel etc.

Yeah, I love my 74 head angle. Sidehops, ups to front wheel, front hops, squeakers etc are ALL better with a steeper head angle. There are downsides though - Can't bridge as far, and probably more importantly the bike doesn't like to roll/tap up stuff so much. It's much easier to hit the front wheel and do a comedy stop (usually followed by going over the bars) when you try to tap on a bike with a steeper head angle. Like everything else in trials though, it's all a compromise - There is no perfect geometry.

OR, you could just get on a bike and go ride and not worry about all this tripe  B)

Bingo :P

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yo sam,

mopst of what you have put there though seems to affect trials bikes alot more than what your thinking. chainstays would b ok i dont think thats much of a problem.

b/b rise does make a difference i feel, -20 you always used to feel as though the back end would never come up when trying to bunnyhop or that might just have been me being crap B)

headangles again slacker is deffinatly better and tighter can make the bike fractionally feel shorter BUT long toptube if you get what i mean.short wheelbase but with long top tube as its steeper it feels though your reaching out more but your front wheel is more under you.

Waynio........................

i think my ideal bike would be:

1075 wheelbase

71 degree headangle

375mm chainstays

+20 b/b rise

going off what i have got at the mo i think that is near perfect geometry........for my small little self.others will be different.

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"RADICAL MAN"

it was th old skool megamo radical frame :huh: :D sweet as heel that was int day that was a "long" bike as it had 1050 wheelbase. but if you want one i know where there is a red one for sale???? if your interestd???

Waynio........................

they had a nice head angle too. dunno exactly what it was but it wasnt too steep i think it could have been 72????

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Hi!

Interesting thread :huh:, I agree with most of the points you raised :D

My (hopefully, seeing as it is being made as we speak) frame geometry is:

Headtube: 74 (or whatever is standard on a Leeson)

20mm BB rise (24inch bike though)

1020mm wheelbase

380mm chainstays

I prefer fairly short bikes myself even though Im quite tall - my old cannondale used to be really short - not sure on the numbers but it was tiny, and my Santa Cruz (although not used for trials) had a short top tube (but not wheelbase I wouldnt have thought with the long forks)

~Gaz

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Yeah, I love my 74 head angle.  Sidehops, ups to front wheel, front hops, squeakers etc are ALL better with a steeper head angle.  There are downsides though - Can't bridge as far, and probably more importantly the bike doesn't like to roll/tap up stuff so much.  It's much easier to hit the front wheel and do a comedy stop (usually followed by going over the bars) when you try to tap on a bike with a steeper head angle.  Like everything else in trials though, it's all a compromise - There is no perfect geometry.

yeah dude 74 degree rocks , i like tighter headangles , makes the bike feel more agressive on two wheel, there are definate advantages to slacker ones though!

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I ride an 04 control:

chainstays:385mm

bb rise:+20mm

wheelbase:1085mm

headangle:71 deg

ideal frame would be similar.. hmm

chainstays:380mm

bb rise:+10

wheelbase:1075mm

headangle:71deg

i'm not sure if there's a frame that matches my 'ideal' geo, but if there is let me know :huh:

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I wonder how much other factors make a difference, for example the flexy Echo rear ends for "more bounce" etc. Or frame material - U6/"normal" alu/Steel/Ti etc. Hard to know, but I bet the secret to an amzing frame isn't simply amazing geometry.

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Just gotta watch out too with a steeper head angle for the comedy OTB moments at the merest hint of front wheel contact :huh:

Went from a 72 or something ° head angle on my Federal Foundation to a 74° on my Parkinson, and I went OTB about 4 times when I first got it just from trying to do stupid stuff :">

The benefits of a slack head angle mean that it feels flicky, but it won't put you on your arse/face as often. So, say, for natural, you'd have a nice stable bike that'd roll over rough stuff nicely, yet it'd still fairly flicky despite the "long" wheelbase.

I went from long stays on my T-Pro to shorter ones on my T-Lite Long, and it felt really good for a lot of stuff having a shorter back end, but ups were shite :D It just felt really unpleasant, like you couldn't give it enough beans almost. Looped out too easily...

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I reckon it'll get to a point where we need different frames for different things, if you really have to go big. For example, Tunni did some huge gaps on a ?1090 Pitbull, but wanted a ?1060 to improve his bunny hops or something.

Whilst I think it's important to improve frame designs and for people to push the boundaries, I also think the majority of people could have more fun on a shorter bike :huh:

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Whilst I think it's important to improve frame designs and for people to push the boundaries, I also think the majority of people could have more fun on a shorter bike  :huh:

Word.

I really prefer shorter bikes. Just way more flicky and fun.

Even tried the "lower" thing, and that felt f**king horrible. I really don't get how people can use the ZOO! stems...

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I'm a firm believer that you can learn virtually anything on any frame. I get fed-up with hearing people saying things like 'he can only do that because he has a short bike/steep head-angle/long bike' - it's people excusing their lack of ability by suggesting their frame is limiting them.

Too many times I've heard people say 'you can't bunnyhop long bikes', etc, only to see people on videos do it. Remember, there isn't some critical length around 1070 that suddenly stops you bunnyhopping and lets you tap shoulder-height. It's as much about component choice. Just by changing the Azonic 2.5" bars on my old Justice to Koxx bars and the standard forks to Toxsin ones I could no longer ride the bike. It felt totally different. I bought a new frame that is 32mm longer and it bunnyhops better than the old one.

For the record, my choicest geometry would be around

1060mm

380mm

72 deg

+20mm

For anyone who thinks they 'need' a long bike to get anywhere, look at what Tibo/Caisso (to name 2) achieved on 1035(ish) bikes.

EDIT: Yeah, my most important consideration with geometry is.... 'Will the bike be fun to ride?'. Because it it isn't, I might as well force myself to do knitting instead...

Edited by snappel
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The only thing with short bikes is that I can't seem to gap them! On my Zoo! I was doing just over 6 anda half ft static gaps, moved onto a Zebdie and couldn't get past about 6ft gaps but found it easier to up and pedal hop gaps went huge all of a sudden. Now on a T-Rex my gaps have gone from strength to strength but I can no longer rolling gap and it took me ages to be able to up as high as I could on the shorter bikes. I seem to have more fun on 24"'s though, I sessioned a sloped wall for about half an hour just spining on and off, had fun on a set of stairs till I got told to stop, just because I could bunnyhop and spin so easily! I don't know what to do :D

James :huh: RAAAAAAAAAAAANT

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I'm a firm believer that you can learn virtually anything on any frame. I get fed-up with hearing people saying things like 'he can only do that because he has a short bike/steep head-angle/long bike' - it's people excusing their lack of ability by suggesting their frame is limiting them.

Too many times I've heard people say 'you can't bunnyhop long bikes', etc, only to see people on videos do it. Remember, there isn't some critical length around 1070 that suddenly stops you bunnyhopping and lets you tap shoulder-height. It's as much about component choice. Just by changing the Azonic 2.5" bars on my old Justice to Koxx bars and the standard forks to Toxsin ones I could no longer ride the bike. It felt totally different. I bought a new frame that is 32mm longer and it bunnyhops better than the old one.

For anyone who thinks they 'need' a long bike to get anywhere, look at what Tibo/Caisso (to name 2) achieved on 1035(ish) bikes.

EDIT: Yeah, my most important consideration with geometry is.... 'Will the bike be fun to ride?'. Because it it isn't, I might as well force myself to do knitting instead...

i totally agree :huh: - a lot of how a bike rides is to with bar/stem anyhow - and long bike can be bunnyhop (rossi can bunny his 1100 BT 6.0 higher than me)! but my bike is an easier bike to bunnyhop! But at the same time certain frame designs, lend themselves to certain types of riding, that can't be denied!

i agree with tomm, trials bikes will get more and more specialised depending on the riding you wanna do too!

mike

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but if they made a frame that was the perfect geometry and made everything easy , but  was no fun to ride  would you buy it?

if this frame did exsist then no, because if a frame existing that was great for everything then it would be awesome fun, because you could ride any style and any terrain and it would do it well and that wouldn't get boring!

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