Corsa Pro vs GP5000 STR - tread width

[warthog101]

not sure if i'm included in that but FWIW i do ride motorycles, track and road so i do have personal experience of this.

each to his own but when i corner on a bicycle i employ the movement of my upper body to the inside of the corner same as i do a motorcycle. this enables me to keep the bike more upright through a corner at a given speed. feels safer to me at least

Apologies. I just disagree then.
Plenty of experience on both too.
There is just so much difference for all of the reasons I listed, I see it as a crap comparison.
I will stay out of the thread.

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Fair enough fella

I agree on the differences, you're spot on. But I also think there's similarities with weight distribution. Would love to know what a pro thinks. Anyone know any??

Back to the OP. Seems like they were using the sidewall part of the tyre when cornering. My solution to this on the same tyres would be using my weight inside the bike to keep it more upright when cornering. Another solution would be using tyres with a wider tread width as mentioned.

[GaBa]

We are off topic here but I started listening to a podcast with Matej Mohorič (in Slovenian though) where he is saying cornering with motorbike or bicycle is "complete opposite" (my words), he says you lean more lighter object while heavier one stays more upright, i.e. you lean more bicycle in cycling and rider in motorbiking.

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Interesting! Wanna hear more about this topic but maybe it needs its own thread

[Hexsense]

(still off topic about lean).
I now realize people don't corner the same way as how I do on bicycle, which is to stay as close on top of the tire as possible to reduce lateral load on the tire (by keeping CG less off center) to reduce chance of washing out. Since the bike angle inward, and I want to be on top of the tire, I naturally lean the bike more than the rider.

Here is a 10 minute video show exactly how I turn. Yes, it's mtb-focussed video. But Pidcock is an exceptional XC rider. So I'm pretty sure he have all these in his bag of techniques.


Regardless, the point on my initial post is just that, bicycle should have wider thread to casing ratio than an average motorcycle. Some motorcycle style lean a lot too. But that's not the norm.

To OP: since you notice that your cornering style lean enough to use every last part of your tread. Just get tire with wider tread to casing ratio in the future. There'll be plenty of people out there who don't lean the bike as much as you. And they'll be fine with tires having narrower tread.

[Mr.Gib]

would genuinely like to hear what the serious racers on this board make of this discussion and I wonder if anyone's asked Tom himself?

No need to ask, the photo of Pidcock says more than any answer that could be given. But the guy in the pink jersey above? He looks like he's trying to ride a motorcycle. But if the side of the tire has no grip (as per the original issue), maybe he's got not choice, but I doubt it. Maybe he's moving slowly and just starting to initiate his turn. Kinda looks like he's headed straight for the barrier on the opposite side of the road.

Pidcock's saddle is nestled under the base of his right (inside of turn) thigh, and his ass is well behind the saddle as well - seems to be common to the fastest guys. The guy in pink has his ass planted on his saddle - you don't want to follow him literally or figuratively. Reminds me of Thibault Pinot descending - not good.



@ads, if your slide out was a total surprise, consider whether like Pinot, you had weight on your saddle. If so that can be a traction killer. Any little bump, roll, hump, etc. in the surface and rider and bike will unweight momentarily. If that happens when you are leaning with lateral g-force building, things can go bad fast. Happened to Pinot often - hence his terror.

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According to this videos both points are accurate in some way: you put your weight insinde on the handlebar and outside on the pedal. Your bum is slightly up from the saddle and outside.

This is great ref and super useful to theorise it like this. That second vid explains it well

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would genuinely like to hear what the serious racers on this board make of this discussion and I wonder if anyone's asked Tom himself?

No need to ask, the photo of Pidcock says more than any answer that could be given. But the guy in the pink jersey above? He looks like he's trying to ride a motorcycle. But if the side of the tire has no grip (as per the original issue), maybe he's got not choice, but I doubt it. Maybe he's moving slowly and just starting to initiate his turn. Kinda looks like he's headed straight for the barrier on the opposite side of the road.

Pidcock's saddle is nestled under the base of his right (inside of turn) thigh, and his ass is well behind the saddle as well - seems to be common to the fastest guys. The guy in pink has his ass planted on his saddle - you don't want to follow him literally or figuratively. Reminds me of Thibault Pinot descending - not good.



@ads, if your slide out was a total surprise, consider whether like Pinot, you had weight on your saddle. If so that can be a traction killer. Any little bump, roll, hump, etc. in the surface and rider and bike will unweight momentarily. If that happens when you are leaning with lateral g-force building, things can go bad fast. Happened to Pinot often - hence his terror.

Agree Tibot's position does look bad there. Not that I'd ever criticise a pro lol.

Some interesting techniques have surfaced in this thread. Admittedly some I didn't know and have def learned a few things

@Mr.Gib it wasn't me that had the accident. OP was mikehhhhhhh

[spartacus]

would genuinely like to hear what the serious racers on this board make of this discussion and I wonder if anyone's asked Tom himself?

No need to ask, the photo of Pidcock says more than any answer that could be given. But the guy in the pink jersey above? He looks like he's trying to ride a motorcycle. But if the side of the tire has no grip (as per the original issue), maybe he's got not choice, but I doubt it. Maybe he's moving slowly and just starting to initiate his turn. Kinda looks like he's headed straight for the barrier on the opposite side of the road.

Pidcock's saddle is nestled under the base of his right (inside of turn) thigh, and his ass is well behind the saddle as well - seems to be common to the fastest guys. The guy in pink has his ass planted on his saddle - you don't want to follow him literally or figuratively. Reminds me of Thibault Pinot descending - not good.



@ads, if your slide out was a total surprise, consider whether like Pinot, you had weight on your saddle. If so that can be a traction killer. Any little bump, roll, hump, etc. in the surface and rider and bike will unweight momentarily. If that happens when you are leaning with lateral g-force building, things can go bad fast. Happened to Pinot often - hence his terror.

OK but you can't tell from that picture whether his weight is actually on the saddle or mostly on his outside foot, not to mention a still snap of a dynamic moment is hard to analyze.

[Mr.Gib]

@Mr.Gib it wasn't me that had the accident. OP was mikehhhhhhh

Oh ya, sorry 'bout that.

OK but you can't tell from that picture whether his weight is actually on the saddle or mostly on his outside foot, not to mention a still snap of a dynamic moment is hard to analyze.

I see some ass squish, looks pretty much like he's planted solidly. And besides, I've watched Pinot enough - it's what he does. When the road is wet it's hard to watch.

Notwithstanding how much trouble we can get into with good tires, the issue of narrow treads on wider rims is a serious one if indeed it is leading to surprise wipe outs. Nobody riding for pure recreation should be crashing on descents, and yet I see it every summer when I am in the mountains. I like to lean the bike a lot. The sidewalls of all my tires are scuffed, but so far no ugly surprises. It could be just some good luck a critical moments. I plan to dial it back another notch on my 28mm Michelin Power Cups on 21mm internal (clinchers though, which I hear are not as bad as TLR).

[Hexsense]

OK but you can't tell from that picture whether his weight is actually on the saddle or mostly on his outside foot, not to mention a still snap of a dynamic moment is hard to analyze.

Yeah, but for most people on a light weight bicycle, the center of gravity is around their belly button. And look where that is, his CG is not close to be on top of the tire. It's so far on the inside which create more lateral load on the tire than it needs to be. Due to his position, he just require more lateral grip out of his tire than someone who stay more on top of where the tire or the bottom bracket is. So, just keep the ass on the saddle rather than off center to the outside is suboptimal, even if he don't put weight on the seat.

[Mr.Gib]

OK but you can't tell from that picture whether his weight is actually on the saddle or mostly on his outside foot, not to mention a still snap of a dynamic moment is hard to analyze.

Yeah, but for most people on a light weight bicycle, the center of gravity is around their belly button. And look where that is, his CG is not close to be on top of the tire. It's so far on the inside which create more lateral load on the tire than it needs to be. Due to his position, he just require more lateral grip out of his tire than someone who stay more on top of where the tire or the bottom bracket is. So, just keep the ass on the saddle is suboptimal, even if he don't put weight on the it.

@Hexsense, if my understanding is correct, at a given speed, a given radius of turn, and a given mass of rider and bike, the lateral load on the tire contact patch will be constant regardless of body position. I see the advantage of the position you advocate (Pidcock's position vs others), as enabling better use of the outside leg as a suspension member, and indeed the whole body makes a much more effective spring when you incorporate some angulation of the upper body over the tires or at least toward the outside of the turn. You need to be off the saddle to use the leg effectively, and getting off the saddle is very difficult or impossible to accomplish the in the position demonstrated by Pinot. If the enemy of fast descending is a lack of traction, then positioning to maximize traction is the goal. By my reckoning, Pidcock's position achieves this.

None of this will be novel to anyone involved in competitive alpine skiing. In skiing separating the upper and lower body in this way is critical in maintain grip on an icy race course. The reverse would be completely absurd.

[mikehhhhhhh]

Nobody riding for pure recreation should be crashing on descents,

I don't disagree, but at the same time, pushing the descents and learning is part of the fun for me.

I possibly got a little on the over-confident side and this crash certainly knocked that confidence a bit. Still seem to descend faster than most but I don't have the same trust in the bike at turn-in anymore.

Slowly building it back up, but it won't put me off having fun

[Hexsense]

@Hexsense, if my understanding is correct, at a given speed, a given radius of turn, and a given mass of rider and bike, the lateral load on the tire contact patch will be constant regardless of body position. I see the advantage of the position you advocate (Pidcock's position vs others), as enabling better use of the outside leg as a suspension member, and indeed the whole body makes a much more effective spring when you incorporate some angulation of the upper body over the tires or at least toward the outside of the turn. You need to be off the saddle to use the leg effectively, and getting off the saddle is very difficult or impossible to accomplish the in the position demonstrated by Pinot. If the enemy of fast descending is a lack of traction, then positioning to maximize traction is the goal. By my reckoning, Pidcock's position achieves this.

None of this will be novel to anyone involved in competitive alpine skiing. In skiing separating the upper and lower body in this way is critical in maintain grip on an icy race course. The reverse would be completely absurd.

Noted. And apologize for long text below. I don't understand enough to write in a concise way.
I don't know if lateral grip is the right word.
But being off center from top of the tire vs just on top of the pivot point (tires) change the force vector direction created by your own body weight (lets draw force vector from cg to pivot point, which is the tire).
If you are on top of the tire then your weight create more vertical force pushing the tire onto the ground and less lateral force trying to push or rotate the tire outside.
If you are on the inside, part of your body weight push the tire outward. Making it easier to slide or tip over.

Is it lateral grip? or does it call something else? Maybe a moment around the tire?
I don't know, it's just so easy to test that if you put the body too far inside, it's easier for the tire to slip under you.
Plus, most MTB-ers just don't want to be that far off-center from the tire when cornering on flat loose surface. Like the video that I post above.

Imagine riding on ice vs on tarmac in a straight line first (ignore lateral force from cornering for a moment). Even if you are not turning, your CG can be off center from where tire meet the road from positioning.

On tarmac, it's fine either if you are on top of the tire or being off center, hanging on the side of the bike that go straight.
The tire have enough lateral grip that you can ride straightline even if you are off balance on the the bike.
On ice, nope. You only stay upright if CG is on top of the tire.
That'd be a way to observe some friction and lateral resistance needed from the tire when CG not being on top of contact patch.

[Mr.Gib]

pushing the descents and learning is part of the fun for me.

I also love the rush of descending, so I feel you. Definitely optimize your equipment for traction, but i'd recommend to keep some margin for error in reserve. And it won't necessarily be your error. I have had cars come around blind curves on my side of the road. You don't want to be right on the limit when something goes wrong. It's moments like that when you want to trust your tires. Over the years I've literally logged hundreds of hours of intense descending, and I am starting to feel I have used up my nine lives. The Gino Mader crash freaked me out - true he was racing, but he knew that road.

Watched a guy crash into some trees on the Tourmalet this summer. First time riding in the mountains and I warned him, but the guy refused to get behind the saddle or use the drops. Decides he's going too quick to make a turn and straight runs through the turn with a locked up rear tire. Lucky bastard threaded the needle between two tight trees. 6 inches either way and he'd be dead. Bike didn't make it though. Guys in front and behind just cruised the corner - it wasn't even that fast.