How Does Geometry Effect The Ride?

[somberlaine]

Hello,

This is the another post asking for frame advice! But I don't want to ask which one to get becuse it's a pointless question. Instead I am asking how changes in certain aspects of the frames geometry effects the ride, and how the advantages and disadvantages of that change. (i.e. longer frames are easier for tapping and gapping but shorter are better for sidehops)

Basically, I have been riding for about 7 years (but am only intermediate), but still have my pashely 26mhz from ages ago and have not kept up with changes in frame design. I don't ride with anyone to get advice or to try out frames with different geometry. I ride street but have a 'classic' natural style.

I guess I need to consider top tube length, wheel base, stem length and rise, bb rise and anything else you think is important! If there are any websites I can go to for an answer then let me know, I have tried to research this before I came here.

I have about 350 pounds to spend on the frame.

Thanks in advance.

Michael

[basher]

Im guessing by classic natural style you mean flowing with manuels and bunnyhops that kinda of riding. If so you want to be looking at a shortish frame with low bb that should suit your style alot better. Id also say something with longish chainstays not something with shorts ones that make the backwheel control good. Im sure someone will give you a decent explanation with abit more experience than me and more detail but thats my say on it.

[somberlaine]

Sorry, no I meant the style that is in no way streety. So no manuals and flowy stufff. (i.e. in no way like you'd imagine a leeson rider to be)

Chars,

Mike

[call_the_police]

Right... If you're looking for a decent frame for a decent price which is in no way streety I'd most likely go for either the 07 Zoo Pitbull or the Echo Control.

As you asked in your question the geometry of a new school frame is simple 72degree head tube to give a comfortable head-angle, unlike streety frames which are usually less to make the bike shorter for manuals, bunny hops etc. A nice set of long chainstays on the frame eg 375mm, increases the control on the back wheel for gapping etc and finally the BB rise, well I'm not sure what this does really but as on the Control it's +20mm.

I ride a Mod and I don't really know too much about the specification on Stock's but what I've put above I do know a bit about so hope this helps mate!

John

[Tomm]

Top tube length isn't really used any more, cos it gets very confusing with these new-fangled frames with multiple tubes etc, and it depends on the seat tube length. Occasionally people use a 'reach' measurement (BB to stem) but it's not really that widely-used. Wheelbase is kinda obvious, I'm sure you don't need that explaining to you. I don't think short frames are better for sidehops really - at least not frames that are less than 1060 (for a stock). Any shorter and you hit your thighs on the bars all the time.

The head angle is the next most important thing IMO, and it's intrinsically linked with wheelbase. If you keep the REACH constant, altering the head angle by 1º changes the wheelbase by about 1cm (very roughly). So as you can imagine, a 1060wb bike with a 74º angle would FEEL much longer than one with a 70º head angle.

Head angle affects taps and rolling down things, slacker head angle (I.e. less degrees) = better for taps (less likely to faceplant) but does make the bike feel more barge-like as the front wheel gets further away from you. Steep head angle is probably better for front wheel stuff - hops, spins etc. Of course it's a compromise between these two things - most (trials) frames are between 70º and 74º. And it does depend slightly on the fork you use, too.

For a long time, it was thought that chainstay length was really important, and that less was better. But if you have the stays too short, it can be harder to load power into your gaps (harder to manual, too). Too long and the bike is hard work on the back wheel, harder to pull up etc.

BB height is again a compromise. But I'll let someone else answer than because I've never owned a high BB bike.

[Ali C]

Right... If you're looking for a decent frame for a decent price which is in no way streety I'd most likely go for either the 07 Zoo Pitbull or the Echo Control.

As you asked in your question the geometry of a new school frame is simple 72degree head tube to give a comfortable head-angle, unlike streety frames which are usually less to make the bike shorter for manuals, bunny hops etc. A nice set of long chainstays on the frame eg 375mm, increases the control on the back wheel for gapping etc and finally the BB rise, well I'm not sure what this does really but as on the Control it's +20mm.

I ride a Mod and I don't really know too much about the specification on Stock's but what I've put above I do know a bit about so hope this helps mate!

John

streety frames have a steeper head angle but usually a shorter wheelbase to keep the reach within reason. 375 chainstays are not long! lol, they are short (too short imo) 380 chainstays have the perfect comprimise of rearwheel control, gapping power and manual/bunnyhopping efficency.

just an example of how geo can change a bike.....My old ashton had a 1055 wheelbase....pretty short in todays frames BUT it had a 73 degree head angle which made the reach the same as a 1080 control frame. So theres a lot more to a bike than wheelbase.

PS, DONT get high bb frame (+30 or more) they are gash unless you like exspensive pogosticks and ride tgs style.

[somberlaine]

OK, thank you very much to all who replied. That was very helpful. I pretty much only ever gap, tap, front-to-back (pigeon?) and wheel swap and certainly never manual or do standard rolling bunny hops up stuff.

So would I be right in thinking that I'd want to look at frames with around 375mm-380mm chainstays; 72mm-73mm head angle; bb rise less than or equal to 20mm; wheelbase unsure.

A few questions: Who or what is tgs style? How does bb rise effect the ride of a bike? How does stem rise effect the ride of a bike (that may sound like a stupid question but i've only ever ridden the same stem for 6 years now and on the few occasions in 7 years where i've ridden someone elses bike, they were using different frames so I didn't know what effect stem rise was doing to that bike in isolation)

Michael

[somberlaine]

Just checked out tarty bikes. I guess I'd want a long frame. The contenders then would be; ZHI Z1, Zoo Pitbull, Adamant A1, Echo Control, Onza Limey 2, KOT MS2, Simtra ST1, BT Rave 7.0 (pretty much all of them!)

[Ali C]

I consider the simtra to have the best geo out of all of those!

[Ash-Kennard]

get either the zhi z1, the simtra or the adamant IMO. they are my personal favourites

the limey 2 would be good too, but i just dont like it to be honest

TGS style=taps, gaps, sidehops

[duane]

Good topic, with good answers, but can some one shed some more light on BB rise, I know that everyone seems to agree that anything over +30 limits a bike to certain styles, but what is the benefit of +20mm (Control 07) over 0mm (pitbull 07) if any ?

Thanks

Duane.

[chrishayton]

Good topic, with good answers, but can some one shed some more light on BB rise, I know that everyone seems to agree that anything over +30 limits a bike to certain styles, but what is the benefit of +20mm (Control 07) over 0mm (pitbull 07) if any ?

Thanks

Duane.

07 pitbul has plus 20

[FoxRacer]

I was recently rather thinking about bb height:cs lenght ratio. As longer chainstays give you better leverage = more power, but also worse control on back wheel. On the other side we have bb height which defines ease of control on back wheel (higher bb = better control on back) and overall balance on a bike which is slightly harder on a high bb bike. So my conclusion was (after consultation with deng)... That actually perfect geo (in my vision of how bike should ride) would be the new czar's one, which should be in sale soon. It should give you great power and still really good control on back wheel compared to all those 375ers. Deng also says that bike should be easier to tap because of CS lenght.

What do you think about this?

[Ray_Ray]

Don't take this as definitive, but I'm going to attempt to shed some light on the effect on BB height. I recently went from a Leeson, which had a low BB to a Zona Zenith, which to my knowledge has a +25mm BB.

What I basically found was that you feel as if you are riding higher on the bike (and you are) and things that you're attempting feel smaller, which is a good thing. It also helps rolling down stuff as you bash has got more clearance. I reckon it amplifies it the effect of shift in body weight, as your body weight is higher and the effective pivot point is higher. I reckon it makes the bike feel more reponsive, but too much BB height makes the bike feel unbalanced and twitchy.

What I'd reccommend is have a look in the rides part of the forum and go along to a ride and ask to have a go on a few different people's bikes.

[somberlaine]

Ok, thank you again to everyone who has replied. I think I have a reasonable idea of what to look for.

Michael