Glad we get another season of awesomeness! Can't wait until you're putting together dynamic case interactions with suspension tune, because that's the magic... and you're one of the few people who can make a useful explanation actually digestible.
Finally someone touching on it being nonsense to compare isolated reach values. Quite literally the only way (or at least with VERY few exceptions) bike geometries have been described and compared by bike media for the last three years and its just not very smart imo... keep it up, one of my favourite series on youtube
This is soooooo eye opening! Finally, it makes sense now not only in my head that reach is critically related to stack height, something I noticed right away when I bought my Mondraker: plenty of reach coupled with a too low stack height, resulting in an unbalanced riding feel, mainly on the steeps, so did some work to bring the stack up (riser bar + 160mm travel from 140mm) and make the bike feel more balanced. I can hardly wait for episode 2. Cheers!
lee mccormack talks about RAD(rider area distance) which is exactly the same thing as your 'spread.' pretty interesting how you both noticed how important this measurement is to bike feel.
Yep - when considered with bar/stem config taken into account (which we'll delve into next week) it basically defines how big the bike feels when standing. It also determines how much leverage you have over your own body weight... which again will be covered in part 2. We came up with the term "spread" to describe it, but until the bike industry comes to some consensus on a particular term to use, there'll be a million different ways to cover it. Some guys back in about 2003 were using downtube length as some approximation to this too.
@@VorsprungSuspension pretty cool! if you get a chance, talk to lee mccormack, he's got some metrics and equations on how to find your RAD/Spread and a few other bike fit related things.
When you vectorize that (distance, and angle from BB) it becomes a pretty comprehensive measurement in terms of bike size and bike intent (if designed appropriately). I suspect that's a lot of what's coming up.
He uses RAD for arm strength while hopping/jumping while the bike is near vertical. In this video is calculated for COM and hand weight, but there should be a magic number for your limb lengths
Hi, can you please analyze further the differences on handling between the following senarios? terrain considerations, your personal preference etc... 1. long & slack (pole, geometron) 2. moderate long & slack (banshee, unno) 3. long & moderate slack (mondraker) Cheers!
It seems to me MTB manufacturers are are doing a lot of RnD that's already been done by motorcycle manufacturers in terms of front end geometry. Right now everyone's obsessed with long low and slack but I haven't seen 1 manufacturer list the trail of their bikes, which is the main factor in how stable vs quick a bike feels, and the product of HA, fork offset and wheel radius. The manufacturers slacked HAs off to gain stability, then forks had to increase offset to get trail numbers back in line (think early 29ers with low offset and slow steering). That also increases brake dive. Another thing to consider is fork response. Slacker HA makes a fork feel more responsive over square edged hits, at the expense of increasing binding and decreasing responsiveness on big landings to flat. I think things have gone a bit too slack at the front end for trail bikes and its a bit harder to lift the rear over obstacles, especially as most of the bikes weight is biased rearwards with the shock, swingarm and drivetrain all concentrated there.
Speaking of CoM, why can't we have a curving dropper seatpost/seat tube, so that when it's down it's positioned towards the rear of the bike and when it's extended it's positioned towards the front of the bike?
It would be complicated to balance travel and shape of the post. It would have to be curved obvs. Then they would also need to start curving the seat tube, in the frame, which may have strength issues...?
Curved telescoping parts are incredibly hard to make. Simpler would just be a seat tube angle that's steeper and with less (or negative) offset from the BB.
No idea if you're reading comments to old videos but an answer/comment to this would be awesome. Since you made this video MTB geo has progressed one or two stages, HTA has got way slacker, reach has extended, chain stays have somewhat stayed the same, seat tube angle has steepened up. My question is this: Has mtb genre (XC, enduro, DH etc) geo reached optimum yet, or is there progres to be made? I know the industry as a whole wouldn't tell us, as they always want to keep selling frames and components for those frames. But how much recent geo change is technically required as opposed to manufactured to sell new bikes? (Downcountry as a manufactured geo/genre is a prime example)
Surprised you didn't mention the affect of BB drop and the subsequent moment around the axles/contact patch and how that effectively lowers the angles mentioned. The extra drop of 29" is one of their biggest advantages IMO, far less pitch sensitive.
That's a bit of a complex issue - BB drop doesn't directly affect the looping/endo angles at the limit conditions when pedaling (climbing) or braking (descending) because torque is transferred from the contact patch through the brake to the rest of the bike. It does indirectly affect it though (once you've actually exceeded the limit condition) from the perspective that the contact patch shifts relative to the rest of the bike once one wheel leaves the ground, and the curve along which it shifts is obviously dependent on the wheel diameter, so a larger wheel size with the same CoM height (ie same BB height above ground, same rider) which has more BB drop will see the contact patch shift a bit further out from the CoM. Dynamic motions that don't involve pedaling or braking however (eg pulling a manual) are very much influenced by BB drop, ie it's harder to manual a bike with a BB below the axle line than above it. 29ers in general tend to have longer wheelbases with longer FCs (due to the longer offset) and RCs (due to the larger wheel size limiting min CS length) so those angles are frequently shallower than the 27.5 equivalents. Bigger wheels also have far better rollover capabilities, lower shaft velocities and less hangup on larger impacts, all of which also improve the ability to smash through stuff without getting pushed around as much. However, on say a seated smooth climb, if the wheelbase is the same and the CoM location is the same (F/R location between wheels and height above ground level being the same), the BB drop won't affect that limit condition in any meaningful manner, because even though it appears you're rotating around the axle, the instant centre is actually the contact patch, so you'd have the front wheel beginning to lift off the ground on the same gradient irrespective of 26" or 29" wheels.
Finally a valuable MTB video without "shredding" and "gnarly" bullshit! You have some serious teaching ability dear sir.
Glad we get another season of awesomeness! Can't wait until you're putting together dynamic case interactions with suspension tune, because that's the magic... and you're one of the few people who can make a useful explanation actually digestible.
Finally another Tuesday Tune!
Christmas came early this year!
Finally someone touching on it being nonsense to compare isolated reach values. Quite literally the only way (or at least with VERY few exceptions) bike geometries have been described and compared by bike media for the last three years and its just not very smart imo...
keep it up, one of my favourite series on youtube
bad luck reach + stack + head angle + some basic trigonometry knowledge is what you really need to get an idea of how a bike will fit
Good to see you back making vids
This is soooooo eye opening!
Finally, it makes sense now not only in my head that reach is critically related to stack height, something I noticed right away when I bought my Mondraker: plenty of reach coupled with a too low stack height, resulting in an unbalanced riding feel, mainly on the steeps, so did some work to bring the stack up (riser bar + 160mm travel from 140mm) and make the bike feel more balanced.
I can hardly wait for episode 2.
Cheers!
Glad you got something out of it!
The thing is stack is easy to change but with reach you are stuck
@@zyoungson215 you can shorten reach by putting spacers in.
Glad that the series is back. Happy Holidays
lee mccormack talks about RAD(rider area distance) which is exactly the same thing as your 'spread.' pretty interesting how you both noticed how important this measurement is to bike feel.
Yep - when considered with bar/stem config taken into account (which we'll delve into next week) it basically defines how big the bike feels when standing. It also determines how much leverage you have over your own body weight... which again will be covered in part 2. We came up with the term "spread" to describe it, but until the bike industry comes to some consensus on a particular term to use, there'll be a million different ways to cover it. Some guys back in about 2003 were using downtube length as some approximation to this too.
@@VorsprungSuspension pretty cool! if you get a chance, talk to lee mccormack, he's got some metrics and equations on how to find your RAD/Spread and a few other bike fit related things.
@@useport80 shall do! We'll discuss some maths related to the spread in part 2 of this, particularly how it's relevant to bike handling.
When you vectorize that (distance, and angle from BB) it becomes a pretty comprehensive measurement in terms of bike size and bike intent (if designed appropriately).
I suspect that's a lot of what's coming up.
He uses RAD for arm strength while hopping/jumping while the bike is near vertical.
In this video is calculated for COM and hand weight, but there should be a magic number for your limb lengths
Your channel is great man. So interesting.
Never stop nerding!
Good to have you back, the simplest things are the hardest to understand usually....
Excellent explanation! Love this stuff. Thanks for posting. Keep it up.
Great job. Looking forward to more knowledge bombs.
AMAZING VIDEO!!!!!!!
thank you for coming back
Hi, can you please analyze further the differences on handling between the following senarios? terrain considerations, your personal preference etc...
1. long & slack (pole, geometron)
2. moderate long & slack (banshee, unno)
3. long & moderate slack (mondraker)
Cheers!
It seems to me MTB manufacturers are are doing a lot of RnD that's already been done by motorcycle manufacturers in terms of front end geometry. Right now everyone's obsessed with long low and slack but I haven't seen 1 manufacturer list the trail of their bikes, which is the main factor in how stable vs quick a bike feels, and the product of HA, fork offset and wheel radius. The manufacturers slacked HAs off to gain stability, then forks had to increase offset to get trail numbers back in line (think early 29ers with low offset and slow steering). That also increases brake dive. Another thing to consider is fork response. Slacker HA makes a fork feel more responsive over square edged hits, at the expense of increasing binding and decreasing responsiveness on big landings to flat. I think things have gone a bit too slack at the front end for trail bikes and its a bit harder to lift the rear over obstacles, especially as most of the bikes weight is biased rearwards with the shock, swingarm and drivetrain all concentrated there.
welcome BACK!
Speaking of CoM, why can't we have a curving dropper seatpost/seat tube, so that when it's down it's positioned towards the rear of the bike and when it's extended it's positioned towards the front of the bike?
It would be complicated to balance travel and shape of the post. It would have to be curved obvs. Then they would also need to start curving the seat tube, in the frame, which may have strength issues...?
Curved telescoping parts are incredibly hard to make. Simpler would just be a seat tube angle that's steeper and with less (or negative) offset from the BB.
No idea if you're reading comments to old videos but an answer/comment to this would be awesome.
Since you made this video MTB geo has progressed one or two stages, HTA has got way slacker, reach has extended, chain stays have somewhat stayed the same, seat tube angle has steepened up. My question is this: Has mtb genre (XC, enduro, DH etc) geo reached optimum yet, or is there progres to be made? I know the industry as a whole wouldn't tell us, as they always want to keep selling frames and components for those frames. But how much recent geo change is technically required as opposed to manufactured to sell new bikes? (Downcountry as a manufactured geo/genre is a prime example)
It's back! Merry Christmas to bike nerds.
where did u get that mario outro track? its sick
great stuff!!
Tuesday tune here to break my brain again next ride
Looking thinner!!!!
Bike geometry tip #1... It's actually trigonometry.
New vid! :)
I think having the endo and looping angles defined from vertical is more intuitive. (Larger == more resistance to endos) Great talk, otherwise!
Surprised you didn't mention the affect of BB drop and the subsequent moment around the axles/contact patch and how that effectively lowers the angles mentioned. The extra drop of 29" is one of their biggest advantages IMO, far less pitch sensitive.
That's a bit of a complex issue - BB drop doesn't directly affect the looping/endo angles at the limit conditions when pedaling (climbing) or braking (descending) because torque is transferred from the contact patch through the brake to the rest of the bike. It does indirectly affect it though (once you've actually exceeded the limit condition) from the perspective that the contact patch shifts relative to the rest of the bike once one wheel leaves the ground, and the curve along which it shifts is obviously dependent on the wheel diameter, so a larger wheel size with the same CoM height (ie same BB height above ground, same rider) which has more BB drop will see the contact patch shift a bit further out from the CoM. Dynamic motions that don't involve pedaling or braking however (eg pulling a manual) are very much influenced by BB drop, ie it's harder to manual a bike with a BB below the axle line than above it. 29ers in general tend to have longer wheelbases with longer FCs (due to the longer offset) and RCs (due to the larger wheel size limiting min CS length) so those angles are frequently shallower than the 27.5 equivalents. Bigger wheels also have far better rollover capabilities, lower shaft velocities and less hangup on larger impacts, all of which also improve the ability to smash through stuff without getting pushed around as much. However, on say a seated smooth climb, if the wheelbase is the same and the CoM location is the same (F/R location between wheels and height above ground level being the same), the BB drop won't affect that limit condition in any meaningful manner, because even though it appears you're rotating around the axle, the instant centre is actually the contact patch, so you'd have the front wheel beginning to lift off the ground on the same gradient irrespective of 26" or 29" wheels.
Thanks for the reply. I think you have to do a video on this.