# Tag Info

## Hot answers tagged geometry

44

Nothing happened or changed. It's just your observational bias coupled with different demographics preferring different bike capabilities. Many children's bikes have relatively relaxed geometry, which makes them stable which has benefits for kids. Bikes built for adults usually aren't as stable, because stability and maneuverability are at odds with each ...

28

This is a common problem, but really not a big deal. I've usually heard it called "toe overlap". I have it on all my bikes. Basically, it's a bit shocking the first time it happens, but you get used to it. It's no big deal. If you're simply aware that it can happen at slow speeds, you'll avoid it easily enough. Since it can only happen at slow speeds, it's ...

18

there's a good write-up about this here: http://www.calfeedesign.com/tech-papers/geometry-of-bike-handling/ In general the steeper the angle the more agile the steering. If you like steeper you might say "quicker, more response", if you didn't like steeper you might say "twitchier". A 1/2 degree difference is probably not going to make that much difference ...

18

I thought this was an interesting question, so first of all, +1. First off, the sloping tube (your second image) is known in cycling parlance as a compact frame. I found an article on the Giant web site about the advantages of a compact frame. When I say "advantages" - this is Giant's word not mine! The full article is here, but to summarise it: the ...

16

Offset primarily affects your mechanical trail - that is, the distance between the imaginary straight line going through your head tube down to the ground, and your tire’s contact patch. Normally, the contact patch is behind the steering axis, hence the nomenclature “trail”. Image from Wikipedia Increasing the fork offset will bring the contact patch ...

15

I think there's a large element of selection bias, combined with changes to roads and traffic rather than bikes. When you were a kid you used to ride with kids who rode a lot, probably on fairly quiet roads. Kids probably ride less than they used to, especially on roads with traffic. Now you ride as an adult, you see fewer kids riding, and pay less ...

12

The trend towards compact frames goes back to the early 90s and an Englishmen named Mike Burrows. Burrows helped design several time trial frames which featured a radically lowered (but not sloping) top tube and a very long seat post. During this time most time trial bikes had top tubes that sloped from the seat DOWN to the head tube (the opposite of what we'...

11

All else being equal, longer chainstays equate to a longer wheelbase, and the rear wheel trailing further behind you. You are correct in your assertion that as wheel size increases so too does chainstay length, though many manufacturers have put considerable effort into minimizing this and as such the increased chainstay length is not directly proportional ...

11

The S shape allows for: stronger head tube and bottom bracket welds without the need for gussetting. You'll find this on more trail focused bikes (such as AM, FR and DH). wheel clearance for long travel forks wheel clearance for the front wheel (ie. 29er's) Still allows for room for a water bottle within the front triangle

11

Much of this is due to UCI regulations. They specify what shape and size of frame can be used. It is not allowed to add extra parts just for improving aerodynamics. See the UCI document Technical Regulations For Bicycles - A Practical Guide To Implementation (PDF) which covers most of this. As it says for Article 1.3.020, the frame elements must be tubular,...

11

Where should pedals be located (relative to the rider)? Wherever its most comfortable for you. It's a matter of personal preference (*). What works for person A won't necessarily work for person B, even if they have the same measurements and/or similar bikes. Your riding position relative to the pedals will change depending on the type of bike, terrain, ...

9

I think you answered your own question when you stated "I don't race." I know many in our club who enjoy the Roubaix. I personally prefer riding my steel Soma ES over my carbon race bike for most things, including fast club rides. Don't get me wrong, a twitchy race bike is great in a crit, but the other non-race bikes have had their design optimized for ...

8

in my experience. BB height affects stability of your ride, but mostly while standing on the pedals since you weight is then directly on the BB. but raising it 7mm may or may not make a difference in your ride. however, raising it ABOVE the axle height will make a dramatic difference in stability. BMX bikes are incredibly nimble (aka unstable) due to them ...

8

TL;DNR - The bike you will ride most often is the bike that will get you fittest. Fitness and power transfer are unrelated. Your bike fitter is presuming you want to make the most of the power you have, so is suggesting an aggressive position is needed. This is possibly because people who pay for bike fitting tend to also be competitive riders who want to ...

8

You might be able to fit a suspension fork on your bike, depending on frame geometry, but I think it’s likely you will not be able to. Frames designed for suspension forks locate the head tube higher to allow for the extra length of a suspension fork, and to provide somewhere for the top of the wheel to go when the suspension compresses. In the early-mid ...

7

First off, understand that the geometry of the bike affects stability, especially the "marriage" between head angle and fork rake. Adjusting these parameters (which can really only be "adjusted" by the frame builder) has a very dramatic effect on stability. Beyond that, the hand position has an effect in a couple of ways. First, if the hand position is ...

7

As for sheer maneuverability, seat tube angle may in some (rather extreme) cases affect wheelbase, which affects stability at variety of speeds. Also seat tube angle will have some minor effect on the position of rider's centre of gravity making it slightly easier to descend with smaller seat tube angle... I guess it would be an unnoticeable difference ...

7

The biggest influence on how a bike steers is 'trail'. Trail is the distance that the contact area of the front tyre on the ground trails behind a line drawn through the steering axis to the ground. (see the Wikipedia on bike geometry) It would be interesting to find if 'trail' lengths have changed over time, and thus the ease of riding hands-free has ...

6

A lot of people commute on cross bikes just fine (and even prefer them to conventional road bikes). He's full of it - the amount you'd need to forget to have issues is roughly being confused enough to think you're an onion (and if you're this confused, well, you're screwed anyway!), especially at commuting speeds. There are different bicycles for different ...

6

Its all about inventory and stock levels. Historically frames came in increments of 2 or 3 cm. So one model might be stocked in 48/51/54/57/60 cm or 48/50/52/53/56/58/60 By having more adjust in the seat post, the supplier can stock three frame sizes of small/medium/large and make up the in-between sizes with longer or shorter seat posts, which will fit ...

6

As others have said, just because the bike shop says it's a good fit, doesn't make it so. Their incentive is to sell a bike off the floor so they'll find the one that fits best and sell it to you. I got a custom fit and I have longer thighs than most people. This meant that to get the seat position right, I had to have my saddle further back from the pedals ...

6

No, it is not. Different bikes in the same class (mountain, cross, road, etc.) may even have different bottom bracket heights even among comparably sized bikes. It is a per manufacturer design decision where to place the bottom bracket. Mountain bikes need higher bottom brackets to clear obstacles vs road bikes or cross bikes, for example.

6

I think you are totally over-thinking the geometry. Don't look at the numbers, go test ride the bikes. First make sure you are looking at the correct size in each model for you. If you don't have enough stand over, either go a size smaller of rule that bike out. Consider the riding position of each bike, get a feel for what you want in terms of aggressive ...

6

TLDR; Essentially the same answer as Argenti Apparatus, but with more background explanations. Which among the two is a more performance oriented geometry and which one is more comfortable? It depends what you mean by "comfortable", if you are referring to fit then geometry that works well for one body proportions may not work well for another. I ...

6

Circa 2000 a Blast had 80mm travel and 26" wheels on 1.90" tires, compared to a modern Blast -27.5" wheels, 100mm travel, on 2.25" tires. The crown height on the modern Blast is significantly higher than its ancestors, necessarily raising the top tube height at the front. The seat tube with modern geometry has been shortened. Among other things such as ...

5

Regarding MTB: The taper allows for a bigger lower bearing while keeping the upper bearing smaller. The lower bearing receives a greater part of the load as most of the time it carries all the weight applied to the headtube and transmits it to the fork. The upper bearing mostly deals with side forces that try to "bend" the fork, i.e. cornering and braking ...

5

What would be some good examples of test cases to assess the impact of these parameters? Build a testbed bike that has adjustable parts covering the different parameters you care about. Instrument it appropriately and measure the changes to the factors you care about as you vary the parameters. This is necessarily vague because there are upwards of 10 ...

5

Endurance geo tends to be shorter reach with a higher stack, but variation on the recipe between brands. Cyclocross bikes are race bikes (although years back they were often marketed as do all bikes, which gravel/all road have now taken over). Race bikes tend to have a lower longer cockpit for a given size, with variation between brands. So it isn’t far ...

5

That bike is what it is, a great urban and light trail machine built to a price point. You got what you paid for. Get out and braap. Most worthy upgrades like wheels, drive train, brakes and suspension will cost the same or more than you paid for the whole thing originally. So don’t spend any more than you need to cover breakages/maintenance. The limiting ...

5

Don't just look at the stack and BB drop, consider the steering geometry as a whole (chainstay length, BB drop, head angle, front-center [BB axis to front wheel axis]) which will affect how the bike handles; and the cockpit geometry (stack and reach) which will affect your position. Cockpit geometry and steering geometry are interrelated obviously, a bike ...

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