# Is Geo Change That Big Of A Deal?



## RideEverything (Jul 25, 2008)

During fork compression the geometry of a hardtail changes. The more travel a fork has the more the geo changes as it gets closer to using full travel.

The main focus of the question is Head Tube Angle (HTA).

As hardtails seem to be a hot topic, at least in the communities that I'm involved in and the mtb media I consume, the geo change with fork compression on a hardtail seems to be something that has been debated a lot lately. 
My current take away is that it is almost impossible to ride a hardtail with a longer travel fork because of the drastic change in HTA from full extension to fully compressed. From what I've read it seems that you might actually spontaneously combust once the fork reaches bottom out!

Is it really that big of a deal?
Or, is it the mtb internet nerding out too much?
Or, is the mtb media pushing some sort of weird hardtail agenda?

For context I'll describe my experiences of riding hardtails for a reasonably long time.

Whether I've had one bike or multiple bikes at a time one has always been a hardtail. I started back in the late 80's on a glorified road bike that was rigid with fat tires. And, have moved on from there. Moving into suspension forks and slowly slackening front ends as geometry has matured.
I went from 26" straight to 29" about 10 years ago.
In the past 20 years I've lived and ridden in what is arguably the mecca of mountain biking, Whistler, BC.

My current steel hardtail would be classified as an Enduro HT. (Whatever happened to the All Mountain category?)
The numbers are:
160mm
HTA at full extension - 62°
HTA at full compression - 67°

With that context I can say that I personally haven't felt the drastic geo change that has been described when the fork compresses through the travel. It hasn't made it harder to control the bike, it hasn't made me feel like I was going to eject over the front of the bike because the HTA is suddenly steeper, I just haven't felt the discussed dreaded geo change that will make it impossible to ride what I ride. I hold that opinion/physical sensation regardless of the 26" and 29" wheel sizes, whether it's cornering, doing drops, jumps, and riding through compressions.

I don't believe that I am somehow a super human biking pro. But, I've never felt that with the compression of the fork on a hardtail it throws me out of whack when riding.

I know that the geo does change on a hardtail when the fork compresses. However, I do not think that the opinions I've read and watched about this topic are as drastic as those people want me to believe.

I actively use my arms and legs when riding which means that I can control the bike through changes in orientation as it rides the terrain. Maybe having skill negates the split second of the geo changes when the fork compresses? It is, after all, a split second of geo change.

What do people think?

Am I an anomaly because I don't feel the split second change in geo effecting my bike control? (I am sensitive to geometry between bikes and the subtle differences in ride feel)

Dare I say that the change in geo when the fork compresses only affects people who aren't that skilled? Or, is it something else?

Is it just bike nerds going too far down the rabbit hole and and only riding their bikes on the internet?

TL;DR
I think the geo changes in a hardtail when the fork compresses are way overblown!


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## Reaperactual (Apr 20, 2020)

Yeah TL;DR: I skimmed your post. No one needs super human powers to ride a hardtail, the vast majority of riders have two arms and legs they also use as suspension, you're definately not an anomaly or over sensitive to geo change any more than anyone else but it does sound like you're 'nerding out' just like these 'virtual internet riders' whatever that is? 🤓😉


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## Whiterabbitt (May 16, 2020)

Also skimmed, hard to follow a simple thought direction…

my takeaway is you have a 160 fork on a seriously aggressive HT that at full compression is slacker than my cannondale super V, and you think it rides great.

my thought: if it climbs OK, rock on, dude. The rest of the stuff you are reading is just words on the internet. Mostly from schmucks.

maybe you need a 180 dual crown fork


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## RideEverything (Jul 25, 2008)

Reaperactual said:


> Yeah TL;DR: I skimmed your post.





Whiterabbitt said:


> Also skimmed, hard to follow a simple thought direction&#8230;


lollers!
Gold star for trying, I guess! ⭐


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## justwan naride (Oct 13, 2008)

Indeed that has been said over the years, both from designers and users. My ht comes with a 130mm fork , I've tried up to 150, ended up on 140mm. My two thoughts on the subject are 1st, humans are able to easily adapt and 2nd, bike design is about compromises. 

So yes, geo changes as the fork compresses and you can feel this, and also yes, you get used to it. It also depends on the fork and how it's set up. If a 160mm fork eats easily through it's travel you're going to feel the effect more. If it has decent mid stroke support it's going to feel less obvious. Others have said that the steepening of the head angle and shortening of the wheelbase is beneficial during turns. 

Personally I feel 140mm is the right amount for me. I lately tend to add a couple of psi more than I used to plus a click of LSC because I feel the bike is more stable this way, with little loss of small bump sensitivity. Last weekend after having the fork serviced I did another round of experimenting with settings and ended up exactly where I started.


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## Reaperactual (Apr 20, 2020)

RideEverything said:


> lollers!
> Gold star for trying, I guess! ⭐


Just skimming cost me 30 seconds I'm never getting back. Well done on your riding skills and being able to cope with those front end geo changes Superman. 🦸‍♂️


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## IPA Rider (Aug 24, 2008)

RideEverything said:


> mtb media pushing some sort of weird hardtail agenda


This...definitely this...so nefarious


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## Gumby_rider (Apr 18, 2017)

I ride a long travel HT and don't think geo change is a big deal. My personal take is that, unless your fork got packed down because your rebound is too slow, the fork is always in the slack end at first contact with the obstacle, and this is what really matters. On the other hand, I'm also an insensitive bastard so I might not feel the geo change people are talking about.


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## RickBullottaPA (Mar 4, 2015)

If it feels good, ride it. Sounds like it works well for you, so that's really all that matters. But...

I'd be more concerned about snapping your headtube off. Unlikely that your frame was designed to handle that geo, it puts a significant amount of force on the headtube/downtube junction when you land it hard. Keep an eye out for cracks. And keep your dental insurance up to date just in case.


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## OldSchoolMBer (May 25, 2013)

RideEverything said:


> Is it just bike nerds going too far down the rabbit hole and and only riding their bikes on the internet?


99% of the internet is a rabbit hole


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## RideEverything (Jul 25, 2008)

I've asked this question because I am curious about what others think about this and their experience as to whether or not they notice it.

The geo change on an HT when the fork compresses has been a topic I've come across regularly lately. As I stated in my OP I personally haven't noticed any negative effects in all the years that I've been riding a hardtail. However, the opinions that I have come across in regards to this seem to be that it's a serious negative especially with a fork that has more travel.

A video I watched recently really stuck with me because it left me with the impression that this geo change would ruin everything about riding a hardtail if you went above a 130mm fork! (This impression could have a tad bit of hyperbole! 😆)

With that in mind over the last few weeks I've been trying to notice any changes in handling and balance over the bike when the fork cycles through the suspension. And, personally, I haven't noticed any negatives whether it's big or small compressions or whether I'm moving fast or slow.

Something that has been raised here in a couple of the comments is fork setup. A poorly setup fork will definitely play into an ugly feeling ride. It'll be magnified more on a hardtail. I think that sensation is the fork rather than the geo change causing the issue.
I run my fork slightly stiffer on my HT because I ride the front of the bike more. So, yes(?), I guess I do notice the geo change if the fork is riding lower than I like? But, I'd be more concerned that I'm not getting the proper support out of the fork rather than the sensation of a slightly steeper HTA... I guess?

Yes, yes, I've (un)ironically created my own rabbit hole! 😂

All things being equal and assuming proper bike fit having your fork setup correctly and riding with a proper body position over the bike with some moderate skill I'll make the assumption that most people won't notice the geo changes on an HT when the fork cycles through its travel.
Yes?

*Edit - If that is case then where is this idea that the geo change on an HT as the fork cycles through the travel being a negative or something to watch out for coming from?

I'm open to different ideas and other's experiences.


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## dysfunction (Aug 15, 2009)

Other than I tend to set up hardtails to have a slightly shorter reach, nope.. not really an issue.


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## RideEverything (Jul 25, 2008)

RickBullottaPA said:


> If it feels good, ride it. Sounds like it works well for you, so that's really all that matters. But...
> 
> I'd be more concerned about snapping your headtube off. Unlikely that your frame was designed to handle that geo, it puts a significant amount of force on the headtube/downtube junction when you land it hard. Keep an eye out for cracks. And keep your dental insurance up to date just in case.


The HT I'm riding already started with a slack HTA. I've helped it get a bit slacker with an angleset. I'm not concerned about frame integrity. (Hopefully I didn't just jinx myself! 🤞😮)
Thank you for your concern though!

Not that I want to get hurt but if I do I'm covered medically here in Canada. That's the benefit of living in a socially democratic country, socialized medicare! I won't go bankrupt going to the hospital. (I've probably used an incorrect term here. Please don't take it to heart.)


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## RideEverything (Jul 25, 2008)

Reaperactual said:


> Just skimming cost me 30 seconds I'm never getting back. Well done on your riding skills and being able to cope with those front end geo changes Superman. 🦸‍♂️


Uh oh! How unfortunate!
Here's a non-redeemable Participation Award to make up for your lost time!
🏆


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## singletrackmack (Oct 18, 2012)

If your bike starts off (unsagged) with a something like a 69-71* HTA like all mtb used to be, then I think the hardtail “effect” is more noticeable as the HTA starts to get above 73* or steeper when compressing. I don’t like that when going down something fairly steep and braking as it feels really twitchy. Combine that with the short front end and long stems like we used to have for a super sketchy feeling.
Modern geo with the slacker HTA, longer front end and shorter stem keeps things feeling much more stable.


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## michaelandk2 (May 15, 2019)

I'm all about my hardtail(s) but imo its the second biggest downside going from my FS bikes to my hardtail (traction being the obvious one). When you hit something hard then get stuck down by successive hits or w/e, it just feels much less safe(and therefore slower) than on a similiar hta FS bike. 

Those two things may or may not be worth the downsides of a FS bike though (efficiency/directness of input, weight, cost, maintenance being the biggest ones). Under the right circumstances, they are pretty obvious differences in my opinion.


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## Reaperactual (Apr 20, 2020)

RideEverything said:


> Uh oh! How unfortunate!
> Here's a non-redeemable Participation Award to make up for your lost time!
> 🏆


Hey Superman! 🦸‍♂️ As a mere mortal rider I'm awe struck by your depth of knowledge so I must be using sarcasm as a defence mechanism.


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## 93EXCivic (Mar 12, 2018)

RickBullottaPA said:


> If it feels good, ride it. Sounds like it works well for you, so that's really all that matters. But...
> 
> I'd be more concerned about snapping your headtube off. Unlikely that your frame was designed to handle that geo, it puts a significant amount of force on the headtube/downtube junction when you land it hard. Keep an eye out for cracks. And keep your dental insurance up to date just in case.


There are more then a few hardtails designed to take 160mm+ forks.

Sent from my LM-G820 using Tapatalk


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## RickBullottaPA (Mar 4, 2015)

93EXCivic said:


> There are more then a few hardtails designed to take 160mm+ forks.
> 
> Sent from my LM-G820 using Tapatalk


Totally. Some DJ's and some burlier frames out there for sure. But if the frame was original designed around a 120mm fork, I have a feeling that the manufacturer is going to be "uncomfortable" with someone running a 160 or 170.


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## RideEverything (Jul 25, 2008)

Reaperactual said:


> Hey Superman! 🦸‍♂️ As a mere mortal rider I'm awe struck by your depth of knowledge so I must be using sarcasm as a defence mechanism.


Oh, that's what you've been trying to do. 
Sarcasm without wit is hard. You'll get there eventually. 
Top marks for the effort at least! 👍


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## Reaperactual (Apr 20, 2020)

RideEverything said:


> Oh, that's what you've been trying to do.
> Sarcasm without wit is hard. You'll get there eventually.
> Top marks for the effort at least! 👍


A gold star, ⭐ a trophy,🏆and now full marks for trying. Thanks Superman! 🦸‍♂️


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## cookieMonster (Feb 23, 2004)

singletrackmack said:


> If your bike starts off (unsagged) with a something like a 69-71* HTA like all mtb used to be, then I think the hardtail "effect" is more noticeable as the HTA starts to get above 73* or steeper when compressing. I don't like that when going down something fairly steep and braking as it feels really twitchy. Combine that with the short front end and long stems like we used to have for a super sketchy feeling.
> Modern geo with the slacker HTA, longer front end and shorter stem keeps things feeling much more stable.


Nailed it. It is not an issue with modern geometry, but also fork setup plays into it as well. I ride pretty much all the same stuff on my Honzo ESD as I do on my enduro bike, and have never once noticed the fork compressing too much and making the bike feel unstable. That said, that bike starts out with a 63 degree head angle, lol.

Thinking back to my old Santa Cruz Chameleon, that bike did have the undesired effect we're talking about. I had it setup as an "all mountain" hardtail, as we referred to them in those days, with a 130mm Marzocchi Z1. Anyway, in retrospect, I never had the right springs in that fork, as it was overly soft (yet soaked up even the smallest of pebbles). Combine that with the quite steep HA (maybe 68-69 degrees?), and always running quite a ways into the travel, it wasn't the most confidence inspiring bike on the steeps. On my Honzo ESD, I'm running a 140mm new Z2, which has awesome midstroke support, so it doesn't really dive that much during hard braking. I'm going to up the travel to 150mm if the air spring upgrade ever becomes available again. Either that or I'll get a 150mm Z1, but I digress.

On another note, what is with the hate toward OP? I found this to be an interesting topic, and his original post was detailed and well-explained. I guess reading comp. is difficult for some.


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## Fleas (Jan 19, 2006)

I just recently installed a 140mm fork. Prior to that I've ridden rigid. For me, the fork feels great as long as it stays in the top half of its travel. With tokens, and ~25% sag, it never bottoms out (don't tell me how to run a fork ). And it's not the head angle that bothers me - it's having more weight forward during compression; it's brake dive; it's losing support on slow, steep, sketchy stuff.

Also, with a long-ish travel fork on a HT, the fork compression/geo change manifests in a steering trail change as well. Usually steering trail is a non-issue on a HT, but if you are used to being all slacked out, it may feel like twitchy crap when your fork gets compressed beyond a certain point. This shouldn't matter compared to a shorter fork, but it just feels weird.

Just as an exercise, I would almost suggest letting [most of] the air out of your fork and see at what point it feels bad. Maybe just slightly higher bars will make it better.

-F


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## RideEverything (Jul 25, 2008)

singletrackmack said:


> If your bike starts off (unsagged) with a something like a 69-71* HTA like all mtb used to be, then I think the hardtail "effect" is more noticeable as the HTA starts to get above 73* or steeper when compressing. I don't like that when going down something fairly steep and braking as it feels really twitchy. Combine that with the short front end and long stems like we used to have for a super sketchy feeling.
> Modern geo with the slacker HTA, longer front end and shorter stem keeps things feeling much more stable.





cookieMonster said:


> Nailed it. It is not an issue with modern geometry, but also fork setup plays into it as well. I ride pretty much all the same stuff on my Honzo ESD as I do on my enduro bike, and have never once noticed the fork compressing too much and making the bike feel unstable. That said, that bike starts out with a 63 degree head angle, lol.
> 
> Thinking back to my old Santa Cruz Chameleon, that bike did have the undesired effect we're talking about. I had it setup as an "all mountain" hardtail, as we referred to them in those days, with a 130mm Marzocchi Z1. Anyway, in retrospect, I never had the right springs in that fork, as it was overly soft (yet soaked up even the smallest of pebbles). Combine that with the quite steep HA (maybe 68-69 degrees?), and always running quite a ways into the travel, it wasn't the most confidence inspiring bike on the steeps. On my Honzo ESD, I'm running a 140mm new Z2, which has awesome midstroke support, so it doesn't really dive that much during hard braking. I'm going to up the travel to 150mm if the air spring upgrade ever becomes available again. Either that or I'll get a 150mm Z1, but I digress.


I do agree that modern geometry does limit or completely hide the negative effects of the change in geometry. That being said it is literally a split second that the fork is down that low and making the HTA steeper.

Digging back into my memory of my first few bikes I do vaguely recall having some issues with riding some steep sections. But, as was said above, the older geometry of those bikes were really steep and very short along with the super long stems made riding anything steep a challenge!

I do understand that the terrain that is being ridden is quite different between everyone. This may have an affect on the experience of feeling geometry changes as the fork compresses.
Where I ride it's regularly steep with hard compressions (not all the time). I find that I like having a longer travel fork on an HT for that kind of terrain. With that, though, I'll admit to not feeling the geo changes effecting me when I ride terrain and features like that. Hence this topic I posted for discussion.

I like it! The discussion is going places!

I hadn't really thought about the comparison between older and newer geometries and how it would effect this.


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## RideEverything (Jul 25, 2008)

Fleas said:


> I just recently installed a 140mm fork. Prior to that I've ridden rigid. For me, the fork feels great as long as it stays in the top half of its travel. With tokens, and ~25% sag, it never bottoms out (don't tell me how to run a fork ). And it's not the head angle that bothers me - it's having more weight forward during compression; it's brake dive; it's losing support on slow, steep, sketchy stuff.
> 
> Also, with a long-ish travel fork on a HT, the fork compression/geo change manifests in a steering trail change as well. Usually steering trail is a non-issue on a HT, but if you are used to being all slacked out, it may feel like twitchy crap when your fork gets compressed beyond a certain point. This shouldn't matter compared to a shorter fork, but it just feels weird.
> 
> ...


Do you think that you have that sensation because you're used to riding a rigid fork? Do you think that sensation will disappear eventually as you ride a suspension fork more - as you adapt and become used to it?

That's an interesting experiment idea. However, if you run the fork with less air it'll sag way more and change the HTA that the person is used to riding on that bike. Doesn't this get in the way of the original idea of just a quick geo change as the fork compresses?
For me I know what it feels like to ride the terrain I ride on a steeper HTA hardtail bike (and less travel) because I've done that. It feels better with a slacker bike.


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## RideEverything (Jul 25, 2008)

Reaperactual said:


> A gold star, ⭐ a trophy,🏆and now full marks for trying. Thanks Superman! 🦸‍♂️


I know you're trying real hard but it's not quite there yet. 
Maybe change tack with the name calling as that may seem to some like you're being mean when you're not intending to.

Good luck!


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## Reaperactual (Apr 20, 2020)

No hate or anything close to it from this side @RideEverything. Think of me calling you Superman as a cute nickname.

I reckon you threw some provocative statements into your original post asking if you we're unique or special to get a response so I responded.

If the assumption above isn't correct I cannot fault your confidence and self belief that the pretty much universally used techniques you use are somehow different or more superior than the vast majority, hence the apt Superman ?‍♂ reference.

I get my comments aren't relevant to your actual question but it's all good and I'm enjoying our little back and forth.?


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## Fleas (Jan 19, 2006)

RideEverything said:


> Do you think that you have that sensation because you're used to riding a rigid fork? Do you think that sensation will disappear eventually as you ride a suspension fork more - as you adapt and become used to it?
> 
> That's an interesting experiment idea. However, if you run the fork with less air it'll sag way more and change the HTA that the person is used to riding on that bike. Doesn't this get in the way of the original idea of just a quick geo change as the fork compresses?
> For me I know what it feels like to ride the terrain I ride on a steeper HTA hardtail bike (and less travel) because I've done that. It feels better with a slacker bike.


Yes - getting used to a squishy fork is def. an adjustment. I've tried them before and never really liked them because they always seemed like a compromise: it worked at high speed, it was vague at low speed; it was "divey" under braking, or it was unresponsive... I have a Pike Select now and it has enough adjustment within the proper range that I found a happy place.

As far as does it affect handling when it's compressed? No. The new(er) bikes have corrected the problem of the steering going twitchy at full compression by setting fork rake and head angle. The best test is dropping into a tight g-out. Your fork will compress AND, because you are traveling basically in a vertical circle (until you pop out) and the ground under your front wheel is well in front of your axle, the steering angles are really messed up. So far my bike has been calm and collected.

-F


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