Timeline for What are the pros and cons of front and rear suspension?
Current License: CC BY-SA 3.0
29 events
| when toggle format | what | by | license | comment | |
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| Mar 28, 2018 at 13:37 | comment | added | Fatalize | BMXs almost always have only one gearing, which is probably not ideal at all. Riding more than short distances on a BMX is quickly tiring. | |
| S Mar 26, 2018 at 14:24 | history | mod moved comments to chat | |||
| S Mar 26, 2018 at 14:24 | comment | added | jimchristie♦ | Comments are not for extended discussion; this conversation has been moved to chat. | |
| Mar 23, 2018 at 2:58 | comment | added | Criggie♦ | @BlackThorn physics.stackexchange.com/questions/394975/… Spotted :) | |
| Mar 22, 2018 at 19:49 | comment | added | Deleted User | Monkey Wrench: Suspension actually increases braking power in rough terrain because it can keep the wheel in contact with the ground and reduce bounce. Probably not applicable for the OP, but hey. | |
| Mar 22, 2018 at 18:58 | comment | added | Criggie♦ | Assuming you're comparing an unloaded bike+rider with the same bike+rider+load, then it will weigh more loaded. So stopping with the same pressure, from the same forward speed, will require dispelling more momentum on the loaded bike. Thus will take longer to stop. Simple physics. | |
| Mar 22, 2018 at 15:29 | comment | added | BlackThorn | My question for you is how heavy does your bike have to be before you can no longer squeeze the brakes tight enough? If you have a good brake system, you should be able to stop it even if your load is quite heavy. | |
| Mar 22, 2018 at 15:27 | comment | added | BlackThorn | @DavidRicherby yes yes, I know, but you don't have to lock the wheels to exert the same amount of stopping power. Anyway, if you feel so strongly about the physics of this, weigh in here: physics.stackexchange.com/questions/394975/… | |
| Mar 22, 2018 at 15:25 | comment | added | David Richerby | @BlackThorn I read what you said, and I explained why it doesn't apply to bicycle braking. You don't stop a bike by locking both wheels so, in any actual bicycle braking situation, the braking is controlled by the brake-wheel interface, not the wheel-ground interface. There is a limit to how much force you can apply to the wheel through the brakes (the strength of your fingers plus the mechanical advantage of the system) and that limit is independent of the weight that's being stopped. | |
| Mar 22, 2018 at 15:17 | comment | added | BlackThorn | @DavidRicherby Guys just read what I said. If you are not limited to how tight you can squeeze your brakes, meaning that you are capable of locking your wheels, then you can generate exactly the same amount of stopping force as you can with a lighter bike. All that matters after that is how you are balanced and whether you will fly over the handlebars, not how heavy your bike+cargo is. This is really simple physics, folks. | |
| Mar 22, 2018 at 11:00 | comment | added | David Richerby | @BlackThorn Sorry, but you're wrong. Extra mass does increase the stopping distance, because it doesn't increase the frictional force between the brake pads and the wheel rim or disc that they're acting on. Your claim that the extra friction at the ground exactly compensates the extra mass is only true if you've locked both wheels and are skidding to a stop, but that's simply not possible on a bike -- you'd go over the bars. (OK, it would also be true if you were only using the back brake and had locked the back wheel, but rotating wheels brake more effectively than skidding ones anyway.) | |
| Mar 22, 2018 at 10:08 | history | edited | Criggie♦ | CC BY-SA 3.0 |
Minor clarifications
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| Mar 22, 2018 at 6:58 | comment | added | Chris H | @BlackThorn you say "over the back wheel" and that's absolutely not the case here. You're not even scaling up the mass in the same place, when your comment would be correct. Any assertion that didn't take into account the mass distribution is oversimplified. A demonstration of when you're correct is riding with a rear child seat. 20kg over the back wheel and you can use the back brake as hard as you'd normally use the front. | |
| Mar 22, 2018 at 2:07 | vote | accept | CommunityBot | ||
| Mar 21, 2018 at 23:46 | comment | added | BlackThorn | @ChrisH yeah, you aren't going to go full on the brakes, that's my point. Braking power isn't the bottleneck, it's the tipping forward that does it. Insofar as the added weight starts to tip you forward, your ability to stop is lessened. Added mass doesn't do that, change in center of gravity does. Front suspension changes the center of gravity, so you may not be able to stop quite as fast. If you had extra weight over your back wheel, you would be able to stop just as fast. It's an issue of balance, not mass. | |
| Mar 21, 2018 at 23:40 | comment | added | ChrisW | @mattnz Is that because you have disk brakes rather than rim brakes? | |
| Mar 21, 2018 at 23:39 | comment | added | mattnz | Most of this answer is over simplified to the point of incorrect, Unfortunately the arguments lead to a correct recommendation making the flawed premise look valid. I am not a betting man, but I put $1000 in it I can stop my full sus MTB quicker than anyone here on a road bike. | |
| S Mar 21, 2018 at 22:36 | history | suggested | Michael come lately | CC BY-SA 3.0 |
Minor grammar improvements. Fix typo.
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| Mar 21, 2018 at 22:27 | comment | added | Chris H | also to come back to the effect of front suspension -- the added weight is in exactly the wrong place to help stop the back lifting, being directly over the front wheel axis. | |
| Mar 21, 2018 at 22:25 | comment | added | Chris H | @BlackThorn that assumes you dare brake at maximum -- so your front brake is on to the point where the back wheel is lifting. Then you hit a crack in the road or a patch of oil. Bad things happen. In most riding you want some margin before hitting that point, but in a car the back will never lift completely and you won't notice one wheel hitting a dodgy patch of road. The first-order physics is the same, but first-order physics doesn't do a very good job of non-ideal situations (that's engineering, and I've been on both sides of the physics/engineering divide) | |
| Mar 21, 2018 at 22:20 | comment | added | Chris H | The low seat suggests something with a low BB to me, for better ergonomics -- that might push more towards a hybrid than a rigid MTB (going by the limited sample size that is my collection) | |
| Mar 21, 2018 at 17:05 | comment | added | BlackThorn | @AndyT cars work on the exact same principle. Typically your squeezing power should be enough to lock up the wheels, just like in a car, at which point we are now working with the maximum friction the tires can generate against the road. | |
| Mar 21, 2018 at 16:14 | comment | added | AndyT | @BlackThorn - In a car your "added mass doesn't increase stopping distance" might add up, as in a car your stopping force is limited by tyre>road friction. On a bike you're often limited by either brake pad>rim friction or not-going-over-the-handlebars; neither of these is increased by increased bike mass. | |
| Mar 21, 2018 at 15:42 | comment | added | BlackThorn | Just to be nit picky here, physics actually says that added mass does not increase stopping distance. The extra mass added to momentum is exactly cancelled out by the extra mass added to the frictional stopping force. Look it up. That being said, your stopping distance will increase at high speeds because the shocks will make your weight will tend to go forward faster, meaning that you have to back off on the brakes to avoid spilling over the handlebars. | |
| Mar 21, 2018 at 14:45 | comment | added | David Richerby | @James The extra weight of front suspension is a factor, since the OP's profile says they live in San Francisco, where there are a lot of hills. | |
| Mar 21, 2018 at 14:01 | review | Suggested edits | |||
| S Mar 21, 2018 at 22:36 | |||||
| Mar 21, 2018 at 13:58 | comment | added | James | The performance-related cons of front suspension would be a factor if OP is planning to participate in the Tour de France | |
| Mar 21, 2018 at 10:36 | comment | added | David Richerby | But I'd avoid the hugely knobbly tyres shown in the photo, for riding only on the road. Knobbles flex against the ground and sap energy. | |
| Mar 21, 2018 at 10:25 | history | answered | Criggie♦ | CC BY-SA 3.0 |