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Discussion Starter #1
Why is it that cross country and race mountain bikes do not use modern geometry such as steep seat tube angle and longer top tube reach as is common in modern trail bikes?
 

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Elitest thrill junkie
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Why is it that cross country and race mountain bikes do not use modern geometry such as steep seat tube angle and longer top tube reach as is common in modern trail bikes?
The seat tube on longer travel bikes that sag when you sit on them is steepened to replicate how it already is on shorter travel bikes. Reach has increased, seat tubes have steepend, but the seat tubes especially are not as dramatic on the longer travel bikes for the above reason. You also already have a good # of weight on your hands due to the shorter travel and steeper HA, what the radical geometry enduro bikes are not great at is all-around flat-terrain riding geometry, going up is decent because of the new changes and going down is ok because of the dropper post, although some are arguing the steeper seat tube puts too much weight and pressure on their hands, but in any case, these changes aren't going to be as radical for XC race bikes. To put it simply, unless it's going to make you faster, there's no point.
 

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Formerly of Kent
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Why is it that cross country and race mountain bikes do not use modern geometry such as steep seat tube angle and longer top tube reach as is common in modern trail bikes?
Because they have less travel AND run less sag than trail bikes. So they don't sink nearly as far backwards when going uphill.

A 77-78 degree STA on a 160mm trail bike running 35% sag will be similar, when you're actually on it, to a 74 degree STA on a 100-120mm XC bike.

As Jayem said, XC bikes are optimized for uphill speed and overall handling. Not just the ability to go downhill fast, while suffering up the hill. I've ridden modern trail and enduro bikes, and despite what some will claim, they are still garbage at going uphill compared to a proper XC bike. Different league entirely.
 

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Discussion Starter #4
As Jayem said, XC bikes are optimized for uphill speed and overall handling. Not just the ability to go downhill fast, while suffering up the hill. I've ridden modern trail and enduro bikes, and despite what some will claim, they are still garbage at going uphill compared to a proper XC bike. Different league entirely.
Hmm. I notice that my V4 Ibis Ripley seems to have better more comfortable climbing geometry than a Pivot les 29 I have ridden. 76 degree sta Ripley vs 72 degree sta on les 29. I felt I needed to push the seat forward on the les 29 to get it to feel similar after I was accustomed to the Ripley. And when I look at other manufacturers bikes for cross country /race (Specialized, Orbea, Scott, etc,) the geometry seems quite similar. Sta has little effect on downhill prowess. As one is typically not seated.
 

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Elitest thrill junkie
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Hmm. I notice that my V4 Ibis Ripley seems to have better more comfortable climbing geometry than a Pivot les 29 I have ridden. 76 degree sta Ripley vs 72 degree sta on les 29. I felt I needed to push the seat forward on the les 29 to get it to feel similar after I was accustomed to the Ripley. And when I look at other manufacturers bikes for cross country /race (Specialized, Orbea, Scott, etc,) the geometry seems quite similar. Sta has little effect on downhill prowess. As one is typically not seated.
I just read 73.5 for the Epic hardtail. That's a long way from 76 IMO. The Pivot is 1 degree slacker, except for the small, which is only half a degree slacker.

What are you smoking?
 

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The STA on the V4 can be hit of miss for some people. There are a number of people saying that its too steep and the reach isn't long enough...therefore putting too much pressure on their hands. I rode a V4 vs a V3 LS...and the V4 didn't really blow me away. Found a good deal on a V3 and went with that.
 

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I think that steep seat angles and climbing ability is a weak correlation at best. There is a lot of reasons a modern trail bike tolerable to climb on, seat angle might be a contributing factor but I think modern suspension design is the biggest factor.

My current XC bike is a 2019 Orbea Oiz. The seat angle on it is 75 degrees, 1 degree steeper than my old XC bike. I have some minor benifits and draw backs of the steepened seat angle. I do find that on steep climbs it take less effort to get into an optimal position. However, on flat ground I find I am a bit further forward then I like and just not as comfortable. It isn't intolerable but I suffered with sore wrists this year a lot more than in the past.
 

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Discussion Starter #8
I just read 73.5 for the Epic hardtail. That's a long way from 76 IMO. The Pivot is 1 degree slacker, except for the small, which is only half a degree slacker.

What are you smoking?
PivotLES
SL Carbon Race XT Mountain Bike

Tech SpecsGeometry
100mm Travel Fork
SMLXL
a Seat Tube16in17.75in19in21in
b Effective Top Tube22.9in23.9in24.5in25.5in
c Stack23.96in24.13in24.83in25.64in
d Reach15.57in16.29in16.66in17.43in
e Stand Over28.5in29.2in29.6in29.7in
f Head Tube3.85in4in4.45in5.5in
g Head Tube Angle69.369.569.570
h Seat Tube Angle7372.572.572.5
i Bottom Bracket Height12.1in12.1in12.1in12.1in
j Bottom Bracket Drop
k Chainstay17.1in17.1in17.1in17.1in
l Wheelbase42.58in43.27in43.9in44.74in
Find your size
More LES builds
 

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Xc bikes have to perform well on positive, negative and zero gradients.
trail bikes are built to perform best on negative gradients and be decent on the ups and flats. As mentioned previously, sag influences the seat tube angle so longer travel bikes should have steeper sta.

If you focus on geometry charts to make a purchase decision then you will likely not end up with the best bike for your xco race needs
 

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Elitest thrill junkie
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PivotLES
SL Carbon Race XT Mountain Bike
My bad, 72.5 for the Pivot, except the small at 73 and 73.5 for the specialized.

My point still stands.

It's a long way from 76 and what are you smoking?

The geometry is in no way what you are making it out to be in your original post. The SA is one degree or less apart, so your point isn't based on reality.
 

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aka Taprider
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The PivotLes is a hard tail, so the seat tube will get steeper with fork sag; whereas, a long travel trail bike might get a slacker seat tube with suspension sag. So might be equal within the limits of seat rail travel.
 

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Discussion Starter #12
My bad, 72.5 for the Pivot, except the small at 73 and 73.5 for the specialized.

My point still stands.

It's a long way from 76 and what are you smoking?

The geometry is in no way what you are making it out to be in your original post. The SA is one degree or less apart, so your point isn't based on reality.
"76 degree sta Ripley vs 72 degree sta on les 29."

My claim was that a Ripley (Which I was merely using as an example) had a 76 degree seat tube angle, optimized for climbing. Many have called these modern geometry parameters for a 29er trail bike. Many cross country bikes have much shallower seat angles and even somewhat shorter top tubes / reach. I was wondering why many hard tails do not use the same modern geometry parameters as modern trail bikes are using. These following geometry claims are copied from the Ibis website. Not "A long way from sta of 76 degrees." But 76 degrees exactly. I respectfully rest my case.



  • [*=center]66.5° Head Tube Angle
    [*=center] 76° Seat Tube Angle
    [*=center] 17" / 432mm Chainstays


 

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I think the segment of consumers who will buy race bikes are probably very different from the segment who buy trail bikes. The racers are probably good enough bike handlers, on average, relative to the weekend warrior that going fast up, down, and on flat takes priority over worrying about whether you are going to endo on your next trail ride with your buddies on a blue trail. On top of that, for most casual riders, going down is the main goal and the climb is meant just to get to the cake. XC racers often prioritize climbing as fast as possible and aero advantages on flat from a lower cockpit. Modern geometry also takes weight off the front end making it harder to corner fast on flat corners while running low rolling resistance XC tires.
 

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Discussion Starter #14
Modern geometry also takes weight off the front end making it harder to corner fast on flat corners while running low rolling resistance XC tires.
A steep seat tube angle puts more weight forward on a climbing bike. Climbing semi steep (to steep) trails with older geometry bikes, one had to slide very far forward on the nose of saddle to keep the front tire on the ground. If one stood on the pedals the back tire would probably slide out. The steep seat tube angle bikes do not require much saddle maneuvering on the steep climbs. Just keep on pedaling. Steep seat angle aids in climbing. And has little effect on down hill handling. Aero dynamics, which are less of a concern on mountain bike than road bike, is probably more a factor of stack height and handlebar width.

I had no idea this would be such a contentious thread.
 

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I wasn't trying to be contentious so I hope I didn't come across that way. I can't speak for the others.

I have never had problems with front end lift even on a 74 degree seat tube and I ride some pretty steep stuff. Wind resistance is the primary form of resistance above 12mph and nowadays, many XC track average speeds are above that. Look at the local Cat 1, national and Word cup races. People are generally wearing very tight fitting clothing with aero helmets
 

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A steep seat tube angle puts more weight forward on a climbing bike. Climbing semi steep (to steep) trails with older geometry bikes, one had to slide very far forward on the nose of saddle to keep the front tire on the ground. If one stood on the pedals the back tire would probably slide out. The steep seat tube angle bikes do not require much saddle maneuvering on the steep climbs. Just keep on pedaling. Steep seat angle aids in climbing. And has little effect on down hill handling. Aero dynamics, which are less of a concern on mountain bike than road bike, is probably more a factor of stack height and handlebar width.

I had no idea this would be such a contentious thread.
A quick question for you. Do you own a modern XC bike yourself?
 

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“Modern” trail bike geometry is all about optimizing descending with saddle dropped. Longer reach and slacker HTA opens up the hips and puts you behind the front wheel on steep descents.

Then, given these design parameters, the question is: how do you make a bike that climbs OK? Steep STA lets you reach the bars on your long-reach geometry and keeps that slacked out front end on the ground when climbing. This, more than sagging into suspension, is what let to steep STAs.

Bikes with these designs are pretty awesome for Enduro-type riding, I.e. grinding through ups to reach downs. They climb acceptably and are fun as hell downhill. My Ripmo is a great example.

BUT, it kinda sucks on level ground. That steeper STA puts a ton of weight on the hands. Reminds me of my old TT bike from my triathlon days. I would not enjoy riding either bike for several hours on flatter terrain.

True race bikes need to work without a dropper, as many very high-level WC types still don’t run them. They also need to be balanced enough to let you hammer away on a rolling course for a couple hours without losing all feeling in your hands.
 

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IMO people/marketing focus too much on HA, STA, and reach. Yes, they can give a good picture of what a bike will feel like but they aren't the whole story.

Marketing has made people feel like they can't ride downhill without a slack long bike, and now you can't climb without a steep sta.

There are many different sizes, dimensions of people, different riding preferences, skill set, etc. They make a difference in what bike you rode and is good to you.

For example, the steep sta on the Ripley didn't really feel more comfortable to me than a slacker hardtail, even though I'm over 6' and it's supposed to be a revolutionary thing for tall people. Didn't make a difference to me either, I'm still faster on the hardtail. I noticed the suspension platform more than the seat tube. Doesn't mean it's bad or someone's wrong, our bodies and preferences are different.

Luckily there are a lot of bike manufacturers that make a lot of different sizes, styles, and dimensions to fit everyone.
 

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Discussion Starter #19
I wasn't trying to be contentious so I hope I didn't come across that way. I can't speak for the others.

I have never had problems with front end lift even on a 74 degree seat tube and I ride some pretty steep stuff. Wind resistance is the primary form of resistance above 12mph and nowadays, many XC track average speeds are above that. Look at the local Cat 1, national and Word cup races. People are generally wearing very tight fitting clothing with aero helmets
I guess at 74 degree seat tube angle, you are getting closer to the sweet spot. This post has seemingly has turned into a me against the world argument. I should probably reluctantly assume that the world is right. But dammit, not without first putting up a good fight.
 

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This post has seemingly has turned into a me against the world argument. I should probably reluctantly assume that the world is right. But dammit, not without first putting up a good fight.
Nothing wrong with asking the question.

Race bikes are always conservative (this is true for XC, DH, Enduro, Road, and CX). A high level racer is very in-tune with their bike and any change to it is going to initially make them slower. Consequently changes have to happen slowly, any big swing is going to be rejected out of hand.

Seat angles have steepend on XC bikes. Not as quickly as they have on trail bikes but the trend is towards steeper seat angles. I am not sure where they will end up. I suspect the sweet spot on FS bikes is somewhere around 75.
 
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