Geo ... Whats It All About?

[r2wtrials]

Right... no doubt this has been asked many times but i would like the up to date thinking.

I am just starting to think about a new frame... be it custom made or off the shelf there is one thing i have no idea on, geometry!! Back in the old days, when i started riding, you just had a frame you liked and went with it. There weren't many trials frames out there and most were converted small frames from cross country or jump bikes.

No i see you lot all going on about bottom bracket height, length of top tube etc etc.. For an old bloke who hasn't kept up with it all can you explain what is good, what isn't and why as far as geometry goes.

And what difference it may make to the riding... is it easier to get onto the back wheel or up onto rocks etc

Obviously i am a low level rider that can just about get onto the back wheel and up onto a 3 foot rock (just!) and i tend to ride sections rather than just concrete hop off one ledge... is short or long, low or high what i would need?.. if it is any help i am a tad under 6 foot and weigh far too much (14 stone) !!

Whilst we are at it... front or rear freewheel?

cheers

[N.Wood]

Well geometry is clearly a very personal thing, so I can only give my view and you can then take pointers from there.

I'm 6'1", and ride very UCI style natural and street.

I ride a Czar which has a wheelbase of about 1090, chainstays of 385 (I think!) and bottom bracket rise of 25.

Higher bb: Easier to stay on rear wheel. More pogostick style. More ground clearance. Eaier to wheelswap/sidehop. Can make you fall off the back of objects when you land on them. Harder to tap

Shorter chainstays: Stays on rear wheel easier. Longer give more leverage for gapping

Longer wheelbase: Better for UCI style riding, easier once on backwheel. Bad for manuals/bunnyhops!

So thas just a list I compiled off the top of my head, there will be bits i missed but hopefully i covered some key points.

[JonMack]

I would imagine something like an Echo Control/Pure would suit you Heath, around 385 stays, 1080 wheelbase and 15-20mm bb rise I think would be good. A reach (center of BB to top center of headtube) of around 660 would probably be good and suit your height quite well.

Nick has done a good job of describing the geometry basics, so I'll leave you to ponder.

EDIT: Front freewheel is good, but will mean you need new cranks and such, sticking to a decent Hope rear hub will be fine!

Edited August 27, 2008 by Mark King

[psycholist]

What geometry suits you depends mostly on what sort of moves you like in trials. If you're a fan of spinning, big bunnyhops, street/skate park style riding and manuals, short reach frames will probably suit you better. If you like TGS (Tap, Gap, Sidehop) riding and natural stuff, a longer reach frame with a higher BB will probably suit better.

The shorter the chainstays are, the easier it is to lift the bike onto the back wheel, but on a long reach frame it will still feel quite difficult initially, especially for manuals, but the bike will feel very comfortable on the back wheel once you're actually up there. 26" frames have their minimum chainstay length dictated by the wheel size, so 375mm is about as short as they get.

The feel of a bike will be dictated to quite a degree by the handlebar/stem choice though (This sets the length of the frame and the perceived BB rise and can completely change the feel of a bike), so if you want to make your bike feel more comfortable at speed and easier to manual, fit risers and a short stem, if you like sidehops and gaps (And natural/competition riding), low handlebars and a longer stem are usually better.

What height you are, your body proportions etc. will also come into play. Pretty much any frame with the right rider can do pretty much anything you'd expect from a trials bike, so this is a general rather than a hard and fast set of rules...

[ogre]

front/rear freewheel, comes down to budget and preferances, the best front freewheel is an eno, 72 engagements means you get a click every 5 degrees, it's more than enough and sturdy as sin. as for rear it's down to a pro2 or king, for stock, or profile r king for mod. i've used an eno and a pro2 and a few acs claws in my time, the pro2 hubs by hope have truley blown me away, f**king incredible sound; 48 engagements, is more than enough engagements, [i've never stuggled to find my biting point like with an ACS claw] but the sound, i've said already it's so re-asuring it's the same with an eno. but th pro2 feel far stiffer. but it's downto budget, £80 on a freewheel and 40-130 on a hub or £130 for a pro2 and then £20 for a sprocket. i don't have much experiance with kings and i couldn't justify £300 on a hub. but i'd advize a pro2 if you can afford one.

[Greetings]

Since it's all been explained very well, here's some practical advice. Don't get a GU TP, don't get a Pure Short. They are really horrible frames, obviously they have their followers, but the majority will probably agree with me here.

One of the most important elements in a bikes geometry in my opinion is the head tube angle. I can ride a frame with 10mm bb rise or 60mm bb rise, but I can't ride a frame which has a 71 deg. head tube. It makes the front wheel stick out really far and that feels awful, especially if you have a heavy wheel/forks.

Good all round modern frames I'd reccomend are the Czar long, GU ST and the Ozonys Cannibal. They've all got slightly longer chainstays, a fair bit of bb rise and a nice wheelbase. There's also the short Pitbull 07 which is a frame with pretty oldschool geometry - so that's something to consider.

[Ben John-Hynes]

Since it's all been explained very well, here's some practical advice. Don't get a GU TP, don't get a Pure Short. They are really horrible frames, obviously they have their followers, but the majority will probably agree with me here.

He's right there.

The short pure is horrile to ride.

[JonMack]

I'm pretty sure Heath is thinking of getting something made up by MarinoBikes, so suggestions as to geo/frames to copy would be much appreciated, such as Inurs

Also check out http://www.r2wtrials.co.uk/html_files/cycletrialsaug08.html to see what kinda riding the OGC get upto

Edited August 28, 2008 by Mark King

[Mark W]

I don't really get the point in getting a custom frame if you don't really have custom geometry you want to have it made up to? There's a hell of a lot to think about, even if you know your onions when it comes to geometry (Side note: I've never used the phrase 'know your onions' before), so why not just go for an 'off the peg' frame instead? As you're not a short dude, go for the 'long' version of whichever frame tickles your fancy, but yeah, I'd go with something like that, then if you think "Hmm, it'd be better if <insert geometry> was <insert better geometry>", you can think about getting a custom frame made later on. It just seems a bit odd to go to the trouble of having to spec all the geometry on a frame if you yourself don't know what you're looking for. Geometry can also affect the strength of a frame to a certain extent, so yeah, I'd just stick with something more proven then go with it. You'll basically learn to ride whatever you get in the end anyway - if you're still relatively early on in terms of learning moves for trials, you probably won't even have much of a preference. When I first started riding and getting into it all, I could basically ride anything with any setup because I didn't really know any better. As time moved on I gradually learnt what I liked, but it was only after a good few years of riding I could confidently say which sort of geometry I prefered, and even then I'd often be pleasantly surprised when I tried other frames and found out they felt pretty good. People seem to place a hell of a lot of emphasis on how they know exactly what angles 'n' stuff they like, but then seem to forget that the ride of a bike isn't just dictated by the angles of it, but also by the weight distribution, stiffness, centre of gravity and so on. So when people think they know what they like, they can often be slightly wrong. You could put the angles of a Coust on a Control (Or whatever...) and the Control wouldn't ride like a Coust.

But yeah, I'm waffling - all I'd say is just get a frame with a relatively low BB, 385mm-ish stays, and 1080 or so wheelbase and you'll probably get on with it fine, or learn to get on with it fine. I wouldn't bother getting a custom just because specing everything is hassle, and you don't really know how well the frame will work with that geometry, so you may as well spend your hard earned money on something more proven.

[ogre]

high bb = good for non bmxy/similar noobs

low bb = good for anyone who's f**ked around with bikes seriously in the last few years?

just for the sake of ease...

[JonMack]

I don't really get the point in getting a custom frame if you don't really have custom geometry you want to have it made up to?

Before reading your post, which I will do tomorrow cos I'm f**ked and am crap at staying up late...

Marino, steel, £65 + £40ish shipping. If it breaks, can hand it to anyone and get it welded

Echo/Koxx/Ozonys/etc, alloy £350-400+. If it breaks, new frame time really.

[Mark W]

With the greatest respect to these guys though, I doubt they're going to be putting the same stresses through their frames as the latest fashionable TGS guy though? So I doubt they'd break many of the frames out at the moment, realistically speaking?

[Jason222]

Good all round modern frames I'd reccomend are the Czar long, GU ST and the Ozonys Cannibal. They've all got slightly longer chainstays, a fair bit of bb rise and a nice wheelbase. There's also the short Pitbull 07 which is a frame with pretty oldschool geometry - so that's something to consider.

+1

This man knows of what he speaks.

Edited August 28, 2008 by Jason222

[JonMack]

With the greatest respect to these guys though, I doubt they're going to be putting the same stresses through their frames as the latest fashionable TGS guy though? So I doubt they'd break many of the frames out at the moment, realistically speaking?

But still, £65 beats £400 every time.

What I'm saying is... why spend £400 when you can get the same basic thing for £65.

Edited August 28, 2008 by Mark King

[craigjames]

How can you justify spending £400 to yourself or the wife if you dont ride the bike that often, i think the marino bike idea or even buying second hand would be the wiser choice......

[Greetings]

How can you justify spending £400 to yourself or the wife if you dont ride the bike that often, i think the marino bike idea or even buying second hand would be the wiser choice......

Well, it's his money so I'd keep such arguments out of this dicussion and concentrate on the main point.

I agree fully with OBM, a custom frame isn't something you're going to benefit from if you don't really know what you like. You could really mess your bike up unless you decide to base it on an existing design. IF you decide to get a used frame, may I recommend the older Deng frames which were made from Ultra6 - like an 05 Echo Control, those are amazing frames.

edit (@ post below): Think they're no longer U6 due to the cost of that tubing. Might be wrong though so lets wait for Mr. Read to verify that.

Edited August 28, 2008 by Inur

[ogre]

thought all deng frames were U6 anyway? surely getting a steel replica of any popular frame would be his best bet? good geo + good price = win.

[psycholist]

With the steel frame there might be a trade off in terms of rear tyre size vs. chainstay shortness. The CNC'd frames get around this with lots of fancy machining around the BB, but a steel frame of this money won't have those features. The other way of looking at buying a more expensive production frame is that it'll last forever and still be sellable if it's only getting occasional use, so it's not exactly money down the drain and you're getting a guaranteed sorted bike...

What's the reliability like on the Merino frames? The price seems a little too low to be trusted - if the frames were that good everyone would be using them (Or the other manufacturers would have dropped their prices lots to stay competitive). Steel fails a lot more safely than Al though (It will creak, flex and rust before failing and fail by bending, so you have loads of warning), so it's not a big worry.

[r2wtrials]

Cheers for all the input... and thanks for pointing out our crap riding john

As was said above... 100 quid for something made to whatever i want is cheaper than a 300-400 off the shelf model. Something i forgot to mention in my first post was how much i used to be a fan of steel over Ally... they seem to ride smoother, which is good for old and knackered joints!! I had Sunn and Rocket frames as my previous two bikes years ago. And with my lack of skill i may not be jumping off big things but crashing or heavy landings will happen... to be able to weld it up myself would be ideal as i have access to welders.

... of course there is the other thing, if you have seen my motorcycle trials bike you will realise that i like something different. I blinged it up to make it stand out when stood against a tree at an event with all the other Beta's. So the hand made one would be a one off.

So something like a Kamel frame geo with 25mm bottom brkt height... that be ok. I would like to feel more confident up on the back wheel.

I will have to build this up from stuff i have already and then improve when money available... i have a hope rear hub at the moment but do like the front freewheel idea. I have Onza cranks at the moment with a screw on echo guard... not sure if a front freewheel will fit on that?. See, said i was a newbie with all this modern stuff

Cheers again.

Edited August 28, 2008 by r2wtrials

[JonMack]

Haha man you've no idea how much I'd love to ride with you guys, you look like you have so much fun, and that's what it's all about!

Yeah you do have a thing about standing out dont you I reckon kamel styling but with the geo said in here 380/1080/+25 would be pretty good.

You could fit a freewheel to your cranks, I assumed you had 'burns for some reason, but yeah you could do it. Eno on the front with any fixed rear hub would be good.

[r2wtrials]

The rock ring still fit with a front free-wheel... never even looked

I still have my old middleburns as well

... i am still running Mavic 121 on the rear almost vintage now!!

[Mark W]

It's only vintage if it's a 521 before they became the 721, and if it's un-ground and in that gun-metal grey finish, whatever it was called... CD?

[monkeyseemonkeydo]

It's only vintage if it's a 521 before they became the 721, and if it's un-ground and in that gun-metal grey finish, whatever it was called... CD?

121's were well before 521's... Old skool baby!

[Mark W]

Ah, yeah, just Google'd that shiz. Assumed it was a typo, my bad! But yeah, 521CDs were pretty much the symbol of trials for quite a while...

[r2wtrials]

It has been with me for around 8 years that rim

... I haven't decided for deffo on the marino by the way, just exploring options and what to look for. A good cheap deal comes up and i may be on a Ally frame! What was the Echo HiFi like? ..

Edited August 28, 2008 by r2wtrials