New geometry and consequences for bike fit

[Nambra]

Definitely get where you're coming from @Big JD. I'm not as tall as you but you're nearly as young as me, and I don't pretend to be anything other than XC/trail in terms of both ability and where I usually ride either.

I think reach and stack are general (and useful) numbers, but they're sort of more relevant to people of average proportions. Leg/arm/torso ratios all factor into reach. ETT is more torso/arm relationship but also about weighting on the bars and general comfort.

This trend toward slacker HTA / steeper STA means that when you have your saddle up a bit and stem/bar height above the design heights, the distance between the two (ie. ETT) decreases more relative to a bike with a steeper HTA and slacker STA. It's probably only millimetres but it probably translates to an individual's arm/leg/torso measurements and ratios being more important now when choosing a frame size, or even a brand of bike for that matter.

I still like and use the old rule of thumb ETT 'test' measurement based on forearm length. Put your elbow against the nose of the saddle with your forearm toward the stem and your hand and fingers out straight. The tips of your fingers should be half way along the stem for optimum fit. There might be some anthropological relationship of forearm length to stature or torso length in support of this anecdotal gauge, or it might just be a load of pferdeshiesse.

 

[hifiandmtb]

And if you can't make it fit, I'll always buy it off you

 

[beeb]

I would suggest that the problem here could be that the bike is actually still too small for you for the steeper seat tube to work. I'm around 190cm and on an XL Ripmo (2nd time on this frame), and while I've only just got this new one - seated position (initially) seems perfect for me with a 50mm stem and ~20mm of spacers. I reckon with the modern geo bikes with steeper seat tubes the weight balance of the seated position is a lot more critical now, as it puts so much more weight on the front wheel if the bike's a bit short in the ETT.

For example- I came off a bike with a 60mm shorter wheelbase, but ETT/seated reach only around 10mm shorter as it had a ~73ish seat angle. I hated it as I felt my weight was too far back and it always wanted to wheelie, whereas the feeling on the new bike is really "sitting in the middle of a limosine" thanks to the long wheelbase. However, I wouldn't want to be too much taller than me trying to get comfortable on it as the balance would be quite front heavy.

One mild change I did compared to the Ripmo I had a couple of bikes prior (now @hifiandmtb mate's bike), was adding an -1 degree angleset to this new one. While seemingly minor - this really changed the feel of the bike, not so much in terms of the actual handling - but it really gets the front/rear weight balance bang-on for me thanks to the fractionally longer front center.

 

[Big JD]

I would suggest that the problem here could be that the bike is actually still too small for you for the steeper seat tube to work. I'm around 190cm and on an XL Ripmo (2nd time on this frame), and while I've only just got this new one - seated position (initially) seems perfect for me with a 50mm stem and ~20mm of spacers. I reckon with the modern geo bikes with steeper seat tubes the weight balance of the seated position is a lot more critical now, as it puts so much more weight on the front wheel if the bike's a bit short in the ETT.

For example- I came off a bike with a 60mm shorter wheelbase, but ETT/seated reach only around 10mm shorter as it had a ~73ish seat angle. I hated it as I felt my weight was too far back and it always wanted to wheelie, whereas the feeling on the new bike is really "sitting in the middle of a limosine" thanks to the long wheelbase. However, I wouldn't want to be too much taller than me trying to get comfortable on it as the balance would be quite front heavy.

One mild change I did compared to the Ripmo I had a couple of bikes prior (now @hifiandmtb mate's bike), was adding an -1 degree angleset to this new one. While seemingly minor - this really changed the feel of the bike, not so much in terms of the actual handling - but it really gets the front/rear weight balance bang-on for me thanks to the fractionally longer front center.

so you steepened the HA on the new Ripmo by 1 degree with an angleset headset????

 

[beeb]

so you steepened the HA on the new Ripmo by 1 degree with an angleset headset????

Nope - slackened. From 65.9 out to ~65 degree.

 

[Big JD]

Nope - slackened. From 65.9 out to ~65 degree.

you crazy rule breaker......................

 

[beeb]

you crazy rule breaker......................

It's a pretty common mod for them as it improves their front end stability for descending a lot - but surprisingly with basically no negatives for climbing. Theoretically it should be harder to climb, but it's so stable and with the more forward seated weighting it just keeps on trucking.

EDIT - I am a fair bit shorter than you and tend to ride more "winch and plummet" type trails than "just riding along" however...

 

[Big JD]

It's a pretty common mod for them as it improves their front end stability for descending a lot - but surprisingly with basically no negatives for climbing. Theoretically it should be harder to climb, but it's so stable and with the more forward seated weighting it just keeps on trucking.

If I steepened the HA the reach would increase!!!!

 

[beeb]

Out of curiousity - Is your seat still pushed forward as in the pic in the opening post?

 

[Ultra Lord]

Yep. Beebs is on crack

 

[Big JD]

Out of curiousity - Is your seat still pushed forward as in the pic in the opening post?

No slammed back with 25mm setback post on its way. That will fark things right up!!!!

 

[beeb]

No slammed back with 25mm setback post on its way. That will fark things right up!!!!

At the end of the day the best solution is whatever you feel comfortable with. Nothing worse than riding when it all feels 'off', so if you prefer the more traditional riding position do what works for you.

 

[Big AC]

Nice new rig mate. In September we can compare new toys.........

 

[Ultra Lord]

you crazy rule breaker......................

Front centre is the measurement between bb and front axle, not reach. Slackening head angle makes this bigger.

I misread it too haha, though for sure beebs was on something.
Nope, I just can’t read very well. Am tradie after all.

 

[Big JD]

Nice new rig mate. In September we can compare new toys.........

any clues

 

[born-again-biker]

So the other day I took old mate to Wild Mersey for the maiden voyage on his new Kona Process.
It's his first dualie and the froth levels were at redline.

Large frame, medium sized bloke. So should be roomy, right?
I lift it off the ute, he jumps on and starts circling the car park.

Totally unprompted, he says,
"... It feels a bit cramped when I'm sitting and turning..." with puzzled look.
So I watched him ride around a bit and sure enough the end of the 800mm bars are pretty close to his knees when turning a sharper arc.
A plan was hatched to get a longer stem and move the saddle back a little.
I was surprised to say the least.

Personally I have found my XL Process a pretty good fit.
Not perfect, but pretty comfy /roomy. Definitely needs a bit more stack height, but not enough to make me do anything about it yet.
I did trim the overall bar width down a little. I felt too "spread eagle" at 800mm.
They're 790mm now and that seems better (small changes do have noticeable effect).

Maybe the new school geo still has a way to go?
Perhaps steep + slack + stretched ETT is the final evolution?

Sent from my LG-H870DS using Tapatalk

 

[Nambra]

Maybe our perception of reach needs to alter, or at least we need to be wary of comparing the reach of older vs newer geo bikes on a like for like basis - don’t base buying decisions on numbers that worked for you in the past?

 

[Big AC]

any clues

First new bike or major upgrade in nearly 7 years so it’s a custom build.

I did a lot of spreadsheet work before pulling the trigger, I wanted something with a big reach but had a decently high stack height, there’s not a lot out there. I wasn’t too worried about the travel number so long as it pedaled well.

I also wanted something that had longer than average CS to counter balance what would be a relatively long front centre, although I don’t need anything too extreme.

The only major parts to go are fork and dropper, just waiting for the right spec to come in stock.

 

[ozzybmx]

For 13yrs have been on a medium bike, I could have ordered a medium without looking... medium fitted me right off the shelf, medium geometry, similar ETT everything.... Now on a Large HighTower LT and it feels like it should. My medium EVIL was 5mm longer than the medium Santa Cruz and the Large SC was only 10mm more than the medium EVIL (15mm between M and L in Santa Cruz ETT), so to go a medium SC I was going 5 mm shorter. I knew I could easily like the the EVIL 10mm longer, the new L High Tower LT fits like a glove.

Also my missus is on a Large Giant Full-E Pro E-bike, shes 5'7".

Definitely modern geo is shortening bikes.

 

[Lazmo]

I’ve recently also have taken to a Kona Process.., in Medium. I’m 5’10” (178cm) and had been looking at Large bikes, as my Stumpy is a Large, although my Cotic is a Medium. Anyway I rolled around on the Process, and although I felt a bit perched up there, with the seat up, the LBS was adamant that it was the right size bike for me. I bought it, but did change the seat to my favourite, which also had more fore aft adjustment in the seat rails, and had planned a slightly longer stem and to cut down the 800 wide bars. In the end I did a bunch of other stuff to the bike but left the stem and bars as they were... and I’m glad I did now. My stumpy now feels like a long hipsters bike, and while the cotic is ok, I’m now gonna get it some wider bars.

In fact, now being perched way up there seems to make climbing feel better, and when I drop the seat, the bike feels playful and chuckable, so it’s good either way.

After I bought the Process, I initially had buyers remorse and felt like the LBS may have stitched me up, but I don’t feel like that now. I think it is the right size for me and I love it and my other bikes don’t get a look in.

Keep in mind I’m in my 60’s, so I’m not hitting stuff like you youngy’s... but I’m still glad for the slack geo, as it gives me some buffer.