Is this necessarily true? Doesn't the seesawing motion allow you to use more of your body to drive the pedal stroke? So that instead of just using longitudinal motion through your legs to drive the bike, you can use your upper body through the bars as well?
Q-factor and DH bikes (or is a wider BB really better?)
- Thread starter Pslide
- Start date
Try and imagine a pistn in an engine going up and down on an angle. Doesn't work all that well. SAme as your legs. This is why they drill trackies into staying straight. That way all the muscles line up better and yu get a more powerful drive.
Isn't the sesawing more a result of letting your legs power get lost by letting them lean the bike. Holding the bike upright, you can notice the extra power put down(or so I though I could feel).
you also find it easier to maintain a smoother and more powerful pedal stroke.
When everything lines up you can recruit more muscle groups
Most dh thesedays doesn't really have any extended sprinting. Well most...
I find it silly tho that more riders don't practice starting/standing sprints. Especaiily given how tight races can be.
Get thee to a velodrome or a bmx track.
When everything lines up you can recruit more muscle groups
Most dh thesedays doesn't really have any extended sprinting. Well most...
I find it silly tho that more riders don't practice starting/standing sprints. Especaiily given how tight races can be.
Get thee to a velodrome or a bmx track.
And if a rider rides flats i seriously dubt he has his feet in the exact same place on his pedals every run and the entire time of it and if he has them .5 of cm from the that place he has lost or gain the diffrence from 73 to 83 shells. So in reality out on the track it wont really mean to much but for xc or road riding were you usally run spds, which keeps your foot in the same place and pedal for extend periods of time Q-factor is definetly relevant to factor into a frame.
Just my 2c
Just my 2c
I have nothing scientific to contribute to this thread but on my last 2 downhill bikes I have needed a wider q factor simply for frame/shoe clearance with the rear triangle. On my 303 with gen 1 saints on it, my shoe was pretty damn close to the rear triangle before the shock was compressed, perhaps 1mm. Im pretty sure there was contact with my shoes going on as i am missing the last side tread bumps on my 5.10 mid soles on the left and the right.
that's a design flaw with the 5.10s, imho; the rear end of the shoe is too damn wide. I have the same issue with frame rub.
I don't see why a DH shoe needs to have side tread.
I don't see why a DH shoe needs to have side tread.
Well other than Specialized, the Orange 224 is also runnning a 73mm BB with a135 mm rear.
With regards to foot placement and riding width, an easy way to test the effect might be be get some custom pedal axles made up that are slightly longer.
Actually come to think of it are all pedals spaced out by the same amount or is there some variance there as well ?
With regards to foot placement and riding width, an easy way to test the effect might be be get some custom pedal axles made up that are slightly longer.
Actually come to think of it are all pedals spaced out by the same amount or is there some variance there as well ?
pedal length/width varies
foot placement varies with flats and clips
foot placement within the shoe varies
Demo uses an effective 150 rear (56mm chainline) not sure why it keeps coming up
Pedaling comfort is a personal thing based on individual physiology. I don't at all buy into the idea that a norrower q-factor is the end-all be-all even on fixed cleat, long distance, seated road riding.
When you move to cycling that involves shorter ride times, much of it standing, much less agressive shoe and pedal interface, stability and traction issues, highly variable lean angles and techniques, jumping, etc...
There is a reason that the people that make a big deal out of listed Q factor are also the same people the spend their time in the weight weenie forum, arguing about the mass of cable crimps vs solder.
As for the weighting and turning issue, you simply need to draw a quick little diagram, to understand where the foot (and thus its application of force) moves with changes in crank length and foot offset from centerline.
foot placement varies with flats and clips
foot placement within the shoe varies
Demo uses an effective 150 rear (56mm chainline) not sure why it keeps coming up
Pedaling comfort is a personal thing based on individual physiology. I don't at all buy into the idea that a norrower q-factor is the end-all be-all even on fixed cleat, long distance, seated road riding.
When you move to cycling that involves shorter ride times, much of it standing, much less agressive shoe and pedal interface, stability and traction issues, highly variable lean angles and techniques, jumping, etc...
There is a reason that the people that make a big deal out of listed Q factor are also the same people the spend their time in the weight weenie forum, arguing about the mass of cable crimps vs solder.
As for the weighting and turning issue, you simply need to draw a quick little diagram, to understand where the foot (and thus its application of force) moves with changes in crank length and foot offset from centerline.
People got pretty excited about low profile pedals...and that is only a matter of mm, both for clearance and lower CG. Understood that pedal clearance is a pretty tangible benefit though.
exactly.
talking about pedal efficiency is pointless on an 8" travel dh race bike running 165mm cranks and flat pedals.
...
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Crap, there goes all the threads on new shock tech and low speed compression damping too...
Wow that post did end the thread.
I have been trying to find info on Q-Factor for DH cranks for 68-73mm BBs but there is very little info out there. I think the new Saint cranks are 182mm in the shorter spindle length which is pretty wide for a bike(hardtail) I want to be able pedal all day.
I'm going to try some Profile Elite Cranks first off and will go to Saint if I have to.
I have been trying to find info on Q-Factor for DH cranks for 68-73mm BBs but there is very little info out there. I think the new Saint cranks are 182mm in the shorter spindle length which is pretty wide for a bike(hardtail) I want to be able pedal all day.
I'm going to try some Profile Elite Cranks first off and will go to Saint if I have to.
Since sustained pedaling is kept to a greater degree minimal for a DH bike in a Race Run -- compared to XC- or Enduro-type runs -- this thread is a psychological battle at best. The greater stability offered by an 83mm BB would give more time for fast-twitch and stabilizer muscles to anticipate movement, where a narrower BB and Q-Factor would use too many stabilizer muscles in order to distribute better weight.
Ride what is comfortable first then you can only do the fine tune.
Ride what is comfortable first then you can only do the fine tune.
Ok, I'm going to avoid the pedalling aspect - mostly because I believe that it has more to do with individual physiology, hip width, etc. My beliefs are also pointless as this point can be measured with various power meter devices, in controlled circumstances and data and proof is slightly better than e-speculation.
On the subject of cornering, while I can feel the effect of pushing an inside handlebar I think that the whole idea of weighting a pedal is fairly irrelevant. Let me explain, pushing a handlebar moves the front tyre relative to the rear wheel and affects the physics of turning a two wheeled device. Weighting an outside pedal doesn't change the position of c of g relative to the tyre contact patch by itself, hip movement has a much greater effect. It's position of c of g relative to the tyre contact patch and lines of force due to centripetal action that affect total grip.
If I'm right then Q factor makes f-all difference in cornering.
The way this may change is if a narrower q-factor enables greater lateral movement of the hips and allows you to have a greater effect upon c of g.
The moto gp cornering style vs motox/exaggerated bike lean is about how far a moto gp bike can be leaned - the limit of clearance and tyre edge is reached before the limit of grip. A motox or Dh bike can be leaned over much further - but we don't have the grip to hold it there without a rut or berm. Hence the exaggerated lean gets the tyres onto the part we want to use to get the bike to turn without steering the bike around the corner with the handlebars, while keeping the line between c of g and tyre contact patch at or near the maximum available angle for the grip available and the amount of cornering force that can be generated. More grip, more cornering force, move more towards the inside.
On the subject of cornering, while I can feel the effect of pushing an inside handlebar I think that the whole idea of weighting a pedal is fairly irrelevant. Let me explain, pushing a handlebar moves the front tyre relative to the rear wheel and affects the physics of turning a two wheeled device. Weighting an outside pedal doesn't change the position of c of g relative to the tyre contact patch by itself, hip movement has a much greater effect. It's position of c of g relative to the tyre contact patch and lines of force due to centripetal action that affect total grip.
If I'm right then Q factor makes f-all difference in cornering.
The way this may change is if a narrower q-factor enables greater lateral movement of the hips and allows you to have a greater effect upon c of g.
The moto gp cornering style vs motox/exaggerated bike lean is about how far a moto gp bike can be leaned - the limit of clearance and tyre edge is reached before the limit of grip. A motox or Dh bike can be leaned over much further - but we don't have the grip to hold it there without a rut or berm. Hence the exaggerated lean gets the tyres onto the part we want to use to get the bike to turn without steering the bike around the corner with the handlebars, while keeping the line between c of g and tyre contact patch at or near the maximum available angle for the grip available and the amount of cornering force that can be generated. More grip, more cornering force, move more towards the inside.
IMO, motorcyclists have to lean more because they have a counter the gyroscopic effects of a rotational mass at high speed than an MTB to contend with. Note what happens when they don't get the lean right, or something goes wrong: they often get high sided as the bike stands itself upright again. If they lean too much or lean and go too slow, they can counteract the grip and the bike+rider falls over.I think road racing motorcyclists do it (lean themselves more than the bike) because they want to be able to open the throttle as soon as possible when exiting the corner, and that requires the bike to be as upright as possible to maximize the rear wheel traction.
Or that's what I've heard, never ridden a motorcycle myself
From the get-go, MTBers in flat corners have to lean the bike instead so the their weight doesn't counteract the amount of grip available, which they maximise by keeping their CoG over the contact patch of the tyre with the ground. If they lean to the inside, they have a higher likelihood of losing grip upfront and washing out than high siding.
Motorcycles can put multiple orders of magnitude more power to the rear wheel than can bicycles. Street and race bikes also have tires sticky enough such that lean angle is limited by peg/foot/bodywork clearance with the ground. This is why it's ideal to hang off the inside of a street motorcycle in corners, to get CoG maximally medial for a given motorcycle's lean angle.
Mountain bikes don't have this kind of traction, thus we can do whatever the hell we want with regard to bike/rider angulation.
Mountain bikes don't have this kind of traction, thus we can do whatever the hell we want with regard to bike/rider angulation.