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What geometry measurements dictates a funner bike?

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What geometry measurements dictates a funner bike?

Old 06-18-20, 11:58 AM
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simonsez
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What geometry measurements dictates a funner bike?

Hi guys, as I continue to learn about bike geometry and fitting, curious to know what can make one bike more fun than another when looking at their respective geometries?

I understand this can be very subjective......is it the seat and head angle? Wheelbase and chainstay length? Rake and trail? So confusing........I assume it's probably a combination of all of them?

Any insights or opinions would be great?
Thanks!
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Old 06-18-20, 12:02 PM
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Depends on how you define "funner". Some people like quick handling bikes, I think they're "twitchy" and prefer more stable handling bikes, which some people describe as slow handling or dull. I like a long wheelbase and long front center for stability, and have no problems going fast on a bike with that style geo.
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Old 06-18-20, 01:12 PM
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Short chainstays = lively acceleration feel
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Old 06-18-20, 01:38 PM
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Originally Posted by simonsez View Post
What geometry measurements dictates a funner bike?
For me, a chainstay that is 430mm or shorter and a trail of 65mm or less will feel more fun than a bike with 450mm chainstays and 80mm of trail.

The more fun bike will feel a bit livelier and quicker to steer- which is how I measure fun.
A bike with 450mm chainstays and 80mm of trail will feel slower and more stable. Thats great for some applications and for some riders so there are valid reasons to have higher trail and longer chainstays.

Thing is- the chainstay length I mention really isnt short, its just middle of the road.
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Old 06-18-20, 03:17 PM
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I got a bike that puts a huge grin on my face and makes me want to go out and have fun because it is agile and accelerates well.

The posts above are accurate.
Mountain bikes goal is to be stable going fast down hill on technical courses. Gravel bikes that follow this pattern of long/low/slack are also very stable, but I find them sluggish and a bit booring. I'd choose that for a week long bike tour (or maybe even an 8 hour day).

Fun is the opposite of long low slack. Specifically:
Short chain stays (as mentioned above). 425 is good, but you can't get much shorter than that and fit gravel tires.
Low. Really, bottom bracket height is almost irrelevant - or at least over blown. Personally, if its too low, I have pedal strike. If its too high I'm more likely to go over the handlebars mountain biking. Although a low bottom bracket makes it easier to sit on the saddle and put my foot on the ground. Is any of that relevant to you? You decide.
not slack. For a medium sized bike (54cm), a head tube angle around 72 - 72.5 degrees (medium frame) is fairly aggressive and agile (i.e CX bike). Depending on the bike, it can go below 70, but 70-71 is typical for gravel. 'course that is what a hybrid has, and no one ever said they were fun. Trek checkpoint has a steepish headtube angle and a long wheelbase which makes it both stable and agile (to a point) which is exactly what you need for loaded touring.

Trail. Yeah, this is directly related to head tube angle (and fork rake), although you can change it a little by changing your tire size. I'm not really sure everyone is measuring this the same and in a way you can easily compare between manufacturers. Its good to see it being used a little more though. An aggressive CX bike is going be around 62mm in a 54cm. Keep in mind these numbers (except chain stay) are going to vary a lot just based on frame size.
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Old 06-18-20, 03:26 PM
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What's fun? Gravel bikes are generally pretty much just road bikes with big tires. The fun is where you go.

This is some (very opinionated but backed-up) food for thought:
https://www.peterverdone.com/some-bi...l-than-others/
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Old 06-18-20, 04:11 PM
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Originally Posted by chas58 View Post
Mountain bikes goal is to be stable going fast down hill on technical courses.

Sigh. This is the goal of downhill mountain bikes - and the bulk of the all-mountain and trail bikes that might as well be downhill bikes. They're enormously unfun to climb with or steer around things with (which makes up the vast majority of my mountain biking time since I don't tend to take ski lifts or van shuttles to the starts of my MTB rides). It's comical and sad that "MTB" is now synonymous with "DH." Sure we're all aware that gravel bikes are effectively the new XC, but show me a gravel bike with a proper front and/or rear shock, that can take a high knob 2.3" tire with mud clearance, has powerful and effortless 180+mm brakes, etc. I've ridden sub-20lb XC racers that have all that. They have the same geometry the rest of your post details. Oh well, before long this segment of fun-to-pedal, fun-to-steer MTBs will be dead and forgotten, so I guess this is off-topic.


Anyway that's a nitpick of a great informative post. There are some 420mm chainstay gravel bikes (I have one), fits a 700x40 / 650x47 and 2X just fine, though the market seems to have dictated that Thou Shalt Fit 650x2.1" / 700x45 so 420m will be gone soon too. Maybe in another 10 years we'll all have long-low-slack full-suspension drop-bar gravity sleds, MTBs will just be pedal-assist motorcycles, and someone will invent yet another category that is fun to pedal again
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Old 06-19-20, 11:27 AM
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Originally Posted by chas58 View Post
I got a bike that puts a huge grin on my face and makes me want to go out and have fun because it is agile and accelerates well.

The posts above are accurate.
Mountain bikes goal is to be stable going fast down hill on technical courses. Gravel bikes that follow this pattern of long/low/slack are also very stable, but I find them sluggish and a bit booring. I'd choose that for a week long bike tour (or maybe even an 8 hour day).

Fun is the opposite of long low slack. Specifically:
Short chain stays (as mentioned above). 425 is good, but you can't get much shorter than that and fit gravel tires.
Low. Really, bottom bracket height is almost irrelevant - or at least over blown. Personally, if its too low, I have pedal strike. If its too high I'm more likely to go over the handlebars mountain biking. Although a low bottom bracket makes it easier to sit on the saddle and put my foot on the ground. Is any of that relevant to you? You decide.
not slack. For a medium sized bike (54cm), a head tube angle around 72 - 72.5 degrees (medium frame) is fairly aggressive and agile (i.e CX bike). Depending on the bike, it can go below 70, but 70-71 is typical for gravel. 'course that is what a hybrid has, and no one ever said they were fun. Trek checkpoint has a steepish headtube angle and a long wheelbase which makes it both stable and agile (to a point) which is exactly what you need for loaded touring.

Trail. Yeah, this is directly related to head tube angle (and fork rake), although you can change it a little by changing your tire size. I'm not really sure everyone is measuring this the same and in a way you can easily compare between manufacturers. Its good to see it being used a little more though. An aggressive CX bike is going be around 62mm in a 54cm. Keep in mind these numbers (except chain stay) are going to vary a lot just based on frame size.
Hey thanks, this was a great and informative post! So I'm looking at a Topstone Carbon and that bike has an unusually short 415 chainstay and a trail of 58 so I assume this would make it "more fun" but then not as stable as others.
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Old 06-19-20, 01:19 PM
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Originally Posted by simonsez View Post
Hey thanks, this was a great and informative post! So I'm looking at a Topstone Carbon and that bike has an unusually short 415 chainstay and a trail of 58 so I assume this would make it "more fun" but then not as stable as others.
just looking at published numbers on Trail for a 54cm bike
55 is aggressive road bike
57 is typical road/endurance
62 is typical Cyclocross
67-70 is a stable Gravel bike
70+ 80+ is "hybrid" or mountain bike.

So yeah, the Topstone (@58mm) is going to handle similar to a road bike. I think I would like the topstone; as one reviewer put it, the geometry
"...makes for an overall sensation thatís more eager puppy than lazy lap dog."

Keep in mind that to do all this with wide tires, they have a unique dishing of the rear wheel (i.e. you can't just swap or buy wheels from another bike), and the Q factor is a bit bigger than normal (+10mm wider).

if you buy wheels, you can dish them pretty easily, but its only going to fit that bike.
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Old 06-19-20, 01:41 PM
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Generally within a brand, I'll look at the geometry for their endurance road bike, and maybe a cross country hard tail. These roughly bookend the geometry for gravel.

The closer it is to the endurance road bike, the closer it is going to feel to a road bike (duh), meaning its going to be more agile and responsive. Some people of course call this "twitchy".

The good thing about agility is you can steer the bike through your hips and your body position. I find with a more "stable" bike, I feel I have to force the bike to start a turn (certainly I have to be more intentional about it) and still I'm going to run wider on the turn at the same speed (i.e. I have to slow down if I don't have enough run-out).

On the flip side, you don't want to dive into a turn on dirt, so with an agile bike, I'll take extra care to be supple with my upper body and not initiate turns too fast. Still, its kinda fun on twisty smooth single track.

FYI, changing tires is going to change your trail a few mm, with 28mm tires having a lot less trail than 50mm tires (that is a difference of ~7mm trail) Which is good, as I want stability when I'm on big tires, and agility on the small road tires.
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Old 06-19-20, 01:41 PM
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Originally Posted by chas58 View Post
just looking at published numbers on Trail for a 54cm bike
55 is aggressive road bike
57 is typical road/endurance
62 is typical Cyclocross
67-70 is a stable Gravel bike
70+ 80+ is "hybrid" or mountain bike.

So yeah, the Topstone (@58mm) is going to handle similar to a road bike. I think I would like the topstone; as one reviewer put it, the geometry
"...makes for an overall sensation thatís more eager puppy than lazy lap dog."

Keep in mind that to do all this with wide tires, they have a unique dishing of the rear wheel (i.e. you can't just swap or buy wheels from another bike), and the Q factor is a bit bigger than normal (+10mm wider).

if you buy wheels, you can dish them pretty easily, but its only going to fit that bike.
Thanks again for the quick reply. Yes I'm aware of the dishing of the rear wheel (although I'm not exactly sure what it means lol). I don't see myself swapping wheels anytime soon if I go with this bike. I tell you, learning and diving into bike geometry has taught me a lot about how a bike will ride a certain way but it still remains so confusing and I'm afraid to make the wrong choice. Cheers!
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Old 06-19-20, 02:10 PM
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fun, are you Bombing down long gravel hills? Go for stability.

I won't be bombing down hills even on a stable bike, so went with a geometry with a bit more toe overlap. Fun is relative to the zone you ride in yes?

fun for me is a sliding scale, the older I get, "more safe" = "more fun"
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Old 06-29-20, 10:57 AM
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Absolutely! I'm approaching sixty years old and bombing down long hills isn't really fun anymore - too scary. Gravel is a good alternative for me since MTN biking is out of the question. I just don't have the balance and coordination that I used to have.
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