Geometry & Numbers

[Oddjob]

I didn't worry too much about numbers when I bought my first dualie (and current bike).
I reckon that's prolly the case for many people.
At the time the biggest factor for me was value for money (and still is). I hate paying extra for intangible brand cred/wank.
I do remember checking/comparing HTA & the Trance was best v.f.m. AND close-to slackest HTA in that category, at that time.
The bike has been great for the last few years - done everything well. Easy to upgrade as I improved too.

And then I went to Maydena.

Nothing brings the geometry numbers into focus more than a full day of death-grip, holy-shit, arse-off-the-back flat-out descending.
Nothing shows up a bikes' (and riders) weaknesses more than "expanding the envelope".

Would the OP take the Satori to Maydena if he/she had a burlier bike in the shed? I'd argue, no. That's because the numbers matter.
Would the OP enter a local XC race on a 160+mm, slack Enduro sled, if they had a stiff, short, upright 100mm travel bike? Prolly not. Wrong numbers, yeah?

When you can only own one bike, shit yeah the numbers matter. I've been studying them like a nutter lately. If that makes me a car park wanker, so be it.
F@ckin' oath I'll dismiss a bike because of a particular number. No apologies. Have I ridden it? No I haven't.
But you try getting a demo ride on an XL frame from a boutique manufacturer....in Tasmania.
You'd have more luck finding Tasmanian Tiger shit on the footpath. When you can't demo bikes (because the distributors don't give a shit about demos) you have no choice but to study the numbers & try to narrow it down. The numbers are your only clues. I don't have the luxury of riding lots of different bikes & just going by the "feel".

My next bike will be my best attempt at choosing the ultimate all-rounder. I'm unapologetically looking for The Unicorn. I will be ruthless about numbers. I can't afford to own it for 3 or 4 years and hate the seat tube angle or fight with the stand-over height etc etc

These bikes that we love so much are some of the most over-priced things on the planet (when you try to look at them in isolation vs other things in life).
When you're handing over thousands & thousands of dollars, why wouldn't you be ruthless about a degree here or there....or a less-than-competitive spec...?

If the numbers didn't matter, and TrekSpeshGiantScott knew everything about bike design, then old mate Leo wouldn't have sold a single Pole & no one would care about his bikes & influence. He would have made no impression & been laughed outta town.
But he's doing well. He's selling bikes & ruffling feathers. People are really interested in his numbers.

You took a Giant Trance to Maydena? Holy shit balls. Respect!

You're in good company though. I did the 2009 Peru Megavalanche which was won by a guy on a 140mm bike. The 2012 Megavalanche was won on a singlespeed hardtail.


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[born-again-biker]

..... The 2012 Megavalanche was won on a singlespeed hardtail.

Are you farking serious ?!!

 

[hifiandmtb]

I had to Google that:

https://www.bikemag.com/news/guy-wins-megavalanche-division-on-singlespeed-hardtail/

Only "Challenger Master" class.

 

[caad9]

And then I went to Maydena.

Nothing brings the geometry numbers into focus more than a full day of death-grip, holy-shit, arse-off-the-back flat-out descending.
Nothing shows up a bikes' (and riders) weaknesses more than "expanding the envelope".

Would the OP take the Satori to Maydena if he/she had a burlier bike in the shed? I'd argue, no. That's because the numbers matter.
Would the OP enter a local XC race on a 160+mm, slack Enduro sled, if they had a stiff, short, upright 100mm travel bike? Prolly not. Wrong numbers, yeah?

Maydena is an extreme example. It seems as though the majority of the riding population were taught a lesson in what's actually steep down there.

In fact, when purchasing my bike, I used Maydena as the specific example where the Satori wouldn't cut it. Not based on geometry, but based on the fact it's lacking in travel for that terrain.

So for my maybe once a year trip to Maydena, I'm perfectly content in hiring a bike.

Also, as noted above with the megavavlanche reference, the geometry doesn't necessarily mean things can't be done. If you were at Maydena and had the option of a bike with the wrong head angle by one degree or no bike, I know which one you are taking, every day of the week.

 

[Oddjob]

I had to Google that:

https://www.bikemag.com/news/guy-wins-megavalanche-division-on-singlespeed-hardtail/

Only "Challenger Master" class.

Bah nitpicking, he got second outright and got all the press that year.

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[Mr Crudley]

Designed squarely for the "Now!" generation who want to bomb down shit straight out of the shop door without having to waste time on irrelevant stuff like actually learning how to ride.....

True, No one is in it for the expedition or climb anymore. It is the short buzz of fun now that seems to get MTB marketing people excited. They did run out of things to talk about in fairness.

I guess this partly comes from the US trail access issues where hikers, equestrians and other wilderness folks have always locked horns with MTB'ers and have gradually moved to groomed man made MTB parks. These have been more flowing and DH focused hence the bikes have also been designed towards this way.

The swing back to water bottles is another one. Hydration packs that carry up to 3l of water with a bunch of food and tools are made more for big days out opposed to a shorter ride dedicated park IMHO.

There is a place for both but I think one of the biggest fun parts of MTB'ing is getting out to the boonies definitely has the back seat. Also takes longer to get there too I guess which many people don't have the time to do.

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[The Reverend]

Geo definitely matters for me. As has been stated earlier when you're tall the numbers seem to get a little wonky for some bikes.

The focus on front centre is my main concern. As the bike gets bigger, only the front gets longer so you get a more rear biased weight distribution. Some folks love short chain stays but I feel that it's optimised for medium.

It's very apparent on some bikes and when I rode the SCHTLT in XL, the rear was too close behind me for comfort. Sure it works for some but just not for me.

Suitably sized demos are rare and hard to come by so one can only use the geo charts.

 

[ianganderton]

The focus on front centre is my main concern. As the bike gets bigger, only the front gets longer so you get a more rear biased weight distribution. Some folks love short chain stays but I feel that it's optimised for medium.

This is the problem with taking just one number and focusing on it

The trend has been for longer fronts on bikes generally I don’t think it’s just front centre. Slacker moves the front wheel out and longer reach moves the riders weight forwards too

Interesting to note that my 2017 Strive CF Race (20mm longer reach than std) with 50mm stem has the same seat post clamp to stem handle bar clamp as my 2005 Specialized Enduro with 70mm stem

Bars are 20mm wider and HTA slightly slacker and travel slightly longer (20mm front, 10mm rear). This all means I feel a lot more centred on the bike but also that it’s not actually a huge difference.




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[The Reverend]

This is the problem with taking just one number and focusing on it

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Which is the reason it's only one of my concerns, not the priority. I look at stack, reach STA and HTA along with other elements.

I do look for balance on my bikes and having ridden or bought bikes with a specific figure flavouring the entire ride I stay mindful of this.

Santa Cruz interestingly stated on a Pink bike Q&A that addressing size specific rear centre was something they wish they did and gave kudos to Norco for it.

Ultimately, I'd demo everything but this is an effective way to thin the long list into something better. It worked out well with the Banshee Prime I just landed on too.

 

[Mywifesirrational]

Are you really that precious that 15mm is the difference between a "barge" and a zippy and agile bike?

As for the BB, it's not terribly difficult equation; your pedals go around in a predictable circle, and depending on the gear you're in, the bike will move forward at a predictable rate. If you're smacking your pedals on rocks, it's rider error.

And even if it does affect clearance, the pay off in the corners when you have a ice stable wheelbase and low centre of gravity is totally worth it. View attachment 344675

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If you don't notice the difference in 15mm chain stay length... I can't help you, that's a fairly extreme change in geometry. I've got bikes with 405, 425, 433 and 445mm chain stays, cornering, jumping and manuals take progressively more effort as stays get longer, playful vs stability, depends what you want from your bike, if you only own one bike for everything, you must make some concessions in performance. Mate bought a Pole a while back (455mm stays), interesting to watch him battle with tight steep corners / hairpins, up or down, however on a 'flow trail' its effortlessly fast.

I also notice bar height (spacers) changes by 3-5mm, or stem length changes by 5mm, makes a massive difference in technical riding, but not so much in general trail riding.

Smacking pedals is not rider error, we have some enjoyable steep technical climbs around here (heading up the technical section of junction track is suitably challenging), when you BB is fashionably low, you have to ratchet your pedaling to clear obstacles whilst climbing, you lose your momentum and come to a stop. You either don't climb anything rocky and technical, have a high BB bike, an e-bike, or are the worlds best technical climber if this doesn't occur to you.

 

[Zaf]

If you don't notice the difference in 15mm chain stay length... I can't help you, that's a fairly extreme change in geometry. I've got bikes with 405, 425, 433 and 445mm chain stays, cornering, jumping and manuals take progressively more effort as stays get longer, playful vs stability, depends what you want from your bike, if you only own one bike for everything, you must make some concessions in performance. Mate bought a Pole a while back (455mm stays), interesting to watch him battle with tight steep corners / hairpins, up or down, however on a 'flow trail' its effortlessly fast.

I notice a difference, but it's subtle. I have my Honzo's chainstays out at their longest at the moment and don't have a problem doing any of the technical skills I usually would on the bike compared to when they're slammed in at 415mm.

Smacking pedals is not rider error, we have some enjoyable steep technical climbs around here (heading up the technical section of junction track is suitably challenging), when you BB is fashionably low, you have to ratchet your pedaling to clear obstacles whilst climbing, you lose your momentum and come to a stop. You either don't climb anything rocky and technical, have a high BB bike, an e-bike, or are the worlds best technical climber if this doesn't occur to you.

You know I live in Alice Springs? It's all rock, and sand, and loose at that.
I ride a Stumpjumper S-Works, Kona Honzo and Trek Slash with 175mm cranks; all notoriously low slung bikes; (the Honzo has a 65mm bottom bracket drop). If you're not ratcheting, it ain't technical!

 

[Paulie_AU]

My cranks are a fucking mess...

 

[Nerf Herder]

If you have time ... Worth a watch, it's a little nerdy but meh.

Really answered a few questions for me ... Look at the bits about trail vs stem length vs hand position ... And long front + short rear vs centred re: cornering.

I've ridden Stromlo several times in the past. but never could rail the corners on luge as an eg. Always found my front washing out on bikes I had thought were fairly slack. Always blamed it on the loose over hard trail surface.

But my last trip on long/ low / slack really blew my mind.

The bit about stem length and having the hands behind the trail ... The bit about being centred and having the pivot point around me as opposed to being in front. All makes sense now. All my bikes previously had 70mm stems and relatively short stays.

I don't think it's so much the slackness any more as my Pole is about the same HA as my Antidote. I think similar reach but not 100%. I corner way faster / more confidently / in way more control on the Pole. Which has to be the longer chain stays + the pivot thingy.

I've never really been a geo or numbers kinda guy ... have always been more about feel ... But this shizzle has me pretty interested again which says a lot as I've been pretty burnt out re MTB

 

[Halo1]

I listen to the pod cast and it is awesome but I am even more confused now on what size bike I need. I really wish I could demo some cotic bikes.

 

[born-again-biker]

I listen to the pod cast and it is awesome but I am even more confused now on what size bike I need. I really wish I could demo some cotic bikes.

Yeah I know what u mean.
I think we're at a bit of a pivotal time (pivotal...geddit?) for bike design.
I think everyone understands the benefits of longer reach and slacker HA.
.... But I think the "new school" chain stay length is still being tested/figured out?
Mr Pole reckons longer CS is better... but others point to the playful character of short CS...

Has anyone on the forums recently owned a long, slack bike with relatively long CS?... And then a long slack bike with short CS?... And could offer a real world opinion?


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[ianganderton]

If you have time ... Worth a watch, it's a little nerdy but meh.

When Cy talks you'd be daft not to listen (as long as it doesnt get to nerdy and the mists of 'not understanding' flood in)

 

[Zaf]

Not sure if it's as common in other places, but how often do you guys hear people talking about the weight of a bike as it's limiting factor?
Might be because Alice Springs has a pretty solid contingent of XC people who all count the grams, but I definitely find that my bikes don't sell locally because I put a bias on reliability and and construction than being light.

I'm guessing the average bike weight of everyone here is somewhere in the 12-13kg mark. Do you factor in weight when building a bike? Is it not something you focus on?

 

[ianganderton]

Weight is definitely one of the numbers that folks take into account. For different people it carries different value


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[Oddjob]

Weight is relative. 200 grams off wheels is more important than 200 grams off somewhere else. Personal weight cones into it too. Not much point spending a gazillion to save weight on the bike when you can do some dieting.

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[ianganderton]

Weight is relative. 200 grams off wheels is more important than 200 grams off somewhere else. Personal weight cones into it too. Not much point spending a gazillion to save weight on the bike when you can do some dieting.

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I think personal weight comes into play in a different way too

200g on the bike has a different amount of effect for a 60kg person compared to a 100kg person

Bike weight has much more effect on lighter riders because they typically generate less power. I’ve seen watts per kilo as a metric for a rider. If a rider is 60kg and their bike weights 13kg it equals 73kg system weight. The bike is 17% of the system weight. For a 100kg rider the bike is 11.5% of the system weight. So about 30% difference. By my maths this means that 200g for a 100kg rider has the same effect as 300g for the 60kg rider

They generate massively different amounts of force/stress on the bike.

A set of fox 36 forks is going to have a very different feel and impact on the energy used for the 100kg and 60kg example riders


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