I spend a lot more time standing on an mtb, so geometry is less of an issue

Aaarghhhhhh!!!! 😉

I guess I think about BB height/drop, wheelbase, chainstay length, front-centre, reach, stack, seat angle (actual, effective and offset), head angle, suspension sag, suspension behaviour, tyre diameter, stem length (including bar backsweep), bar width and ETT. But I’m an engineer and product designer. If you can actually understand geometry at this level of geekiness and you’re not working in a similar field then you should probably consider a career change to better utilise your talents!

Wasn’t at all until recently. Then, before getting my new bike, i dabbled a little, got lost and confused and bought a bike i liked the look of (colour, lines, material and suspension design). Only took an interest to begin with as i knew i wanted a bit more room between the seat and bars than my previous bikes.

I didn’t like the geo / handling of early 29er “norms”, so I made my own frame – does that count?

Some of us ride MTBs for more than 5 hours. 😆

Having ridden a few bikes I went through a few geometry charts to work out what I like best and had Brant build me a frame that matched that.

Jon Taylor – Member
So none of you have drawn out your frame geometry in CAD?..

I would love to do this, but have zero knowledge of CAD. Can anyone recommend a good program for a CAD-newbie to play around with bike geo in?

I tried the online BikeCAD thing, but couldn’t get it to run properly on my mac, even with the help of actual IT people.

Sort of ex-geometry geek here. More of a ride-feel geek now, prefer to judge the end result by riding it. If we’re talking about welded frames, alu in particular, I think mass-production reality makes worrying about 0.5 degree +/- on paper between 2 bikes seem less important. Also, we can adapt to different geometries really well if we get over the idea of muscle memory familiarity meaning ‘right’.

Some of us ride MTBs for more than 5 hours.

Yes yes, what I meant was you could arguably get a feel for an MTB’s handling in a 15 minute test ride outside the shop, but if you’re buying a road bike for it’s (lack of) stack and reach, you’ll only really know after five hours on the road and whether your back and neck are hurting. I can get on a slammed racing bike and ride it round the car park and it feels awesome, doesn’t tell me much about how it’ll feel at the end of a long day.

I’ve not progressed to the stage of spreadsheet yet but last night was spnt comparing reach, ETT, HA and hedtube of two well known steel hardtail manufacturers on print outs from their respective websites…. 😳

I didn’t used to be like this but knowing what I like and what I think I want has made me this way…

Colour, although vitally important, is definitely secondary. Whilst I want to admire it in all its glory it doesn’t really matter when I’m rattling along a tech bit going ‘oh shit, oh shit….’

Not a geek but I know what I like, so tend to try & stick to stuff in that relative area.

Here’s what I made to play about and help choose my new road bike:

I do the same thing as robertgray05.
Mainly because the last bike I had was the perfect fit, so when I fancied something new it had to be as close to it as possible, but slacker and longer travel. I had about 15 bike in excel with all the geometries and then scored each component of the geometry, as well as overall. Funnily enough I ended up with another Whyte and it fits like a glove.

With road bikes, is geometry mostly a case of fit or is there much variation in handling too?

I look at the geometry table, then realise head angle is the only one I’m that bothered about, then realise that sag is probably not taken into account in the same way by different manufacturers so just take a punt on things.

This a great game for people into geometry
http://www.euclidea.xyz/

Is this normal? Do you check geometry before buying, or just say ‘I’m a Medium’, and buy that?

Check geo. Always.

How reliable are the published geo’s? I know in the ski world, even pretty straightforward measurements like ski length go through the marketing department before being published.

Also, as some have said above, I can make my mtb handle like a POS if I change the setup, so it’s all done by feel. I didn’t test ride my last new bike, but it’s generally well regarded, and was an especially good deal. Is it perfect? Don’t know, but it got me through Swiss Epic in good shape and I had lots of fun doing it!

I pay a lot of attention to top-tube length and BB drop – those number make the biggest difference to me.

How reliable are the published geo’s

Depends on the manufacturer. There are two issues – sometimes there’s a communication issue between the engineers and the marketeers, and with any welded frame there’s a certain amount of manufacturing tolerance. On a decent alloy or steel frame you’ll have about 0.5 deg tolerance on the head angle but some will be more like 1 deg.

I’ve measured my Banshee and Bird as best I can and they seem to be very close to the charts, within 0.1 deg or so. Tube lengths should always be pretty bang on and as seat angle and BB drop are constrained by two triangles they should be very close to spec.

Some of my geometry obsession came out here: http://singletrackworld.com/forum/topic/bird-zero-am-review-warning-bicycle-content

The key thing is to know that when it feels right and makes you comfortable and confident then it is right!

I haven’t used it but this looked full on geek to me…
comparison tool

top 3 website –

stack & reach calculator

Massive geek, i’ll dismiss a well regarded bike on HA alone.

I like to know the angles of what i’m buying first….then i know it’ll do the job i want or the type of riding i do….then i can make it fit with little tweaks like bars, stems, seatposts, saddles etc.

Its the main reason i have no interest in a 29er Enduro, didnt Dirt Mag have to fit the 650b linkage, use offset shock bushings and a neg rise stem to get it working as you’d hope a 3k bike would straight from the box?!….bugger that.