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Well worth 20 minutes of your time as the guys from PB put a massive change from current geometry on the hillside. No spoilers from me.
Saw that yesterday, not disappointed after the long wait for the video.
Watched it last night - ace!
Shame this was done by an online publishing team rather than a multi-million pound bike company, but fair play to them, and also the factory that made it.
Just the right amount of stupid! 🙂
I like that saying "we've stumbled across the right amount of stupid".
Snap!
It is an interesting idea but the shape just looks all wrong - how that frame hasn't snapped at headtube is impressive...it just looks all wrong. The fork is almost angled so the traditional seals and bushings aren't going to run smoothly as they aren't really going up and down but sliding at a forced angled.
I've not seen the video yet but will watch it - the above is just my uneducated thinking - especially watching the amount of flex produced in the slow-mo bottoming out videos of suspension bikes.
An interesting idea, but looks like it will fail dramatically. Hopefully the video proves my thinking completely wrong!
It's brilliant, highly entertaining and i really like Mike L, a bike nerd who see's the funny side of being a bike nerd
edit: quick someone copy Dick's comment before he watches the video
Who else wants a bottle 'oldeer now?
It is an interesting idea but the shape just looks all wrong
Would you have said the same thing ten years ago about today's bikes? I would have....which is kinda the point of the experiment.
It is an interesting idea but the shape just looks all wrong – how that frame hasn’t snapped at headtube is impressive…it just looks all wrong. The fork is almost angled so the traditional seals and bushings aren’t going to run smoothly as they aren’t really going up and down but sliding at a forced angled.
I’ve not seen the video yet but will watch it – the above is just my uneducated thinking – especially watching the amount of flex produced in the slow-mo bottoming out videos of suspension bikes.
An interesting idea, but looks like it will fail dramatically. Hopefully the video proves my thinking completely wrong!
Certainly one of the most STW posts ever.
Singletrack have previous in this area of course - they made their own bike years before this.
Bollocks to the bike, I want the mini at the start!
Interesting vid, wonder on the side loading on the fork bushes...
I wonder if dropping the head tube height to help pick up the bb height slightly would help
It's very good at one thing seemingly.. As Yoaan says, you wouldn't want it as your everything bike (or words to that effect)
Everything is a compromise for a bike that performs well everywhere. They could just as easily make a frame that excels at climbing,but is rubbish downhill....maybe.
Cool experiment and I'm glad they did it. It'll be interesting to see what we are actually riding in 2030.
The guy testing it reminded me of the scuba instructor from Along came Polly.
An interesting idea, but looks like it will fail dramatically. Hopefully the video proves my thinking completely wrong!
Are you so sceptical of bridges, aeroplane wings not snapping and the existence of helicopters?
Grim Donut huck to flat about 3 mins in.
I feel like the Trust fork might actually come into its own with a bike like that.
Levy does like his Trust fork. Hmmm.
I could be wrong but I think the Grim has already had a Trust on it, just for extra Ugly.
It's really entertaining, I don't think for a minute they actually thought it would be any good, and YB's comments were super interesting. Also I shall be referring to it as a bottle older from now on.
I could be wrong but I think the Grim has already had a Trust on it, just for extra Ugly.
Only in photoshop IIRC
I enjoyed Yoann's laugh when he saw his time - genuinely contagious, I found 🙂
Very entertaining and I’m amazed it worked as well as it did. Some of the comment from both mike and yoaan are brilliant
Nope, I trust the engineers that have spent the time learning and working out the right stuff...but as this has been done without all that (from what I can see from the various videos and articles on it), then I'm more sceptical.
Side loading was the terms I was after not the up and down bit.
Video looks good...does support Chris Porter's chat about longer bikes being faster as well, that bike seemed to make a decent dent in the 'standard' bike time on that run they filmed.
As I said, it doesn't make sense to me, but I'm not trained or skilled in this area (I have enough problem trying to get my leg over the bike!), so happy to see it being ridden and used, but the front end does look like it'll be ripped off without much impact!
Noticed Chris Porter's name in the credits too.... he actually did this for real (albeit bit more seriously) five years ago.
The issue with too much side loading isn't going to be an issue all the time, how often do you huck to flat. Surely the head angle will mean the fork can compress backwards more and "get out the way" of oncoming obstacles, kind of like the theory behind high pivot points for rear suspension
Only in photoshop IIRC
Makes sense, there has to limits after all...
I knew it would probably work well!
I’ve made a business from ignoring convention and pushing the boundaries with audio products. People are just so stuck in their ways!
Regarding the forces on the fork, we ride our bikes forwards so impacts are rearwards most of the time - that’s why high pivot rear suspension works so well. With that 57 deg head angle you’ll have 20% more leverage on a huck to flat than with 63 deg HA. Is 20% a big deal?
Look what Paul Aston has built after 15 years of pushing the boundaries with non DH bikes:
https://m.vitalmtb.com/features/Ultra-Long-210mm-Travel-Enduro-Machine-Is-This-the-Ultimate-MTB,2947
57 Degrees!!
That was a fun video. Its a really cool idea.
If they dial back the stupid just a touch they might really be onto something.
Ultimately though, you really need to be a good rider benefit from that style of bike.
I'm on a LLS trail bike with a 65 degree HA and I keep having to remind myself to get my weight more forward.
If I rode the Grim Donut I'd be spat out the side on the first corner.
That's a highly entertaining video, Mike Levy's enthusiasm is properly infectious - don't think I've ever spent 20 mins watching a review of a bike I've no interest in owning!
Been waiting for this video for a while, love ridiculous projects like this!
Bollocks to the bike, I want the mini at the start!
I mentioned to Levy in the PB comments about how ridiculous that bike would look carried by the Mini and we got into a conversation about how it wouldn't fit on his rear mounted rack. Ended up talking about Mini's for a bit and about how strap-on racks can separate the roof from the rest of the car, he spotted the tell-tale signs of that on his car and now he has a seasucker as in the vid!
My little claim to fame.
It is an interesting idea but the shape just looks all wrong – how that frame hasn’t snapped at headtube is impressive
It certainly doesn't look conventional! But in terms of the headtube, not really, you have to consider which way the forces are acting, unless you slowly hit a huge huck to flat, then it'll be fine.
Genius. Loved both of those videos.
“I’m on a LLS trail bike with a 65 degree HA and I keep having to remind myself to get my weight more forward.”
You wouldn’t if your bike had longer chainstays!
“unless you slowly hit a huge huck to flat, then it’ll be fine.”
As I said above, 20% more leverage than with a 63 deg head angle. It’ll fine full-stop.
Crumbs. Never occurred to me it was possible for the chain to slap the ground on landing.
The grim tagnut?
the head angle means that flat hits (like the huck to flat) there's a lot of sideways load on the bushings - so they perform badly - but whilst riding along and hitting a log the force comes from the front - it could easily be that angles like that are more perpendicular to the force hitting the wheel and thus actually work better (same for the force going through the headtube)
but as this has been done without all that (from what I can see from the various videos and articles on it), then I’m more sceptical.
They did the FEA and the rig testing on it according to the vid.
Im sure Cy talked about it in his lectures at Sheffield (10 years ago?). The loading in the CEN test for pulling the fork forward is actually mimicking a landing so hard your legs would buckle.
Podcast discussing it here
https://www.pinkbike.com/news/the-pinkbike-podcast-episode-23-grim-donut-2-is-live.html
Here you go,
The CEN test is 1200N pulling horizontally away from the rear axle, 50,000 times.
At 2012 geometry (yes slacker will be a bit less) that was 50,000 9G landings to flat.
Not just forward - it loads in both directions alternating 1200N fwd and 600N rwd iirc.
The loads are set to get a balance of short (cheap) test without overdoing it (plastic failure). Fatigue cycles add up - if you want to test at smaller loads then crack on but it might have to run for a million cycles. Mixed load cycles would be best but that needs more complicated rigs and control. It is basically a stake in the ground to show you've tried to makes a safe bike.
I would like to see someone try to separate length from head angle. That wheelbase looks long enough to have a normal head angle and the bars far enough behind the steering axis to be connected by a backwards stem. Then it would be interesting whether that behaved well or whether a remote steering linkage would be required.
A backwards stem would cause quite a lot of steering instability.
I know some brands like Nicolai are pushing the limits of whats available but it's good to see what PB have done.
I think the industry just likes to do incremental changes for their next model bikes so they can do the same again for the next model. rinse repeat.
No one seems to do any empirical data collection and just work out what is actually fastest.
I like the grim donut though.
A backwards stem would cause quite a lot of steering instability.
Aft of steerer mounted bar pivot point with linkage to steerer needed then....
Problem for me is there was no A-B-A type test.
Watching the video,there are several very significant sections where on the second run (on the GD) that YB is hitting much faster / straighter lines. However, without a second run on his normal bike, we don't know if he was able to hit those lines due to additional familiarity (due to it being his second run) or actually because the long/slack bike ENABLED him to hit those lines without crashing........
A backwards stem would cause quite a lot of steering instability.
out of interest, why? the steering geometry itself would be the same (for the same frame), just the arc in which your hands move would change (I think?). As we've moved from 150mm stems to 40mm stems, that arc has changed quite a bit already, why would it all go wrong if we went backwards (say) 40mm?
I think the article says it's a track he knows well. Sure, it's not a double blind randomised trial, it is interesting and it is entertaining, and I don't doubt the result.
We've been hearing for a while that many manufacturers don't make the enduro bikes that racers would like.
I wonder how commencel feel about it 🙂 To be fair they have probably won more world cup DH and EWS rounds than most other brands so i doubt to bothered .
I can see Yoann asking Max to knock up a 60° head angle prototype.
“out of interest, why? the steering geometry itself would be the same (for the same frame), just the arc in which your hands move would change (I think?). As we’ve moved from 150mm stems to 40mm stems, that arc has changed quite a bit already, why would it all go wrong if we went backwards (say) 40mm?“
I wrote a reply but the internet ate it...
It’s because most destabilising inputs to a MTB cause deceleration. And that causes the rider’s mass to apply a forwards force to the grips. The longer the stem, the more that force has a self-centring effect on the steering. A negative stem will do the reverse unless both hands are equally weighted.
I thought that was amazing. And there is no way I’d be mincing down that track. But the bit that I found most impressive was not the bike. No, it was the calm cool commentary on both runs. Just remarkable. Bike seems like it could compensate for even my skills deficiencies.
Not just forward – it loads in both directions alternating 1200N fwd and 600N rwd iirc.
The loads are set to get a balance of short (cheap) test without overdoing it (plastic failure). Fatigue cycles add up – if you want to test at smaller loads then crack on but it might have to run for a million cycles. Mixed load cycles would be best but that needs more complicated rigs and control. It is basically a stake in the ground to show you’ve tried to makes a safe bike.
If you watch the video he makes that point. 600N seems like a high number, but achievable in the real world.
1200N pulling has no real world application and broke the original Soul in about 1/4 the required cycles (and everyone elses frames it seems).
No, it was the calm cool commentary on both runs. Just remarkable.
Yeah - and he calmly says at the start he'll be going about 80% of capacity and then proceeds to shoot down it at unreasonable speeds and takes 15 seconds or something off the Strava KOM 😐
Yeah – and he calmly says at the start he’ll be going about 80% of capacity and then proceeds to shoot down it at unreasonable speeds and takes 15 seconds or something off the Strava KOM 😐
Have a look at some of Yoann's other videos...
Rides tech like he's riding to the shop for a pint of milk.
There's an unrelated Finn Isles vid this week where he's training too, again, the same...flying down, destroying the trail like he's strolling for a sandwich.
My <b>35kg</b> kid has been playing with a measured static 62.1 deg HA on a correspondingly long frame for his size and 142mm cranks.
Goes downhill VERY fast... uphill ... a bit of a pig. Seatpost is very slack though.
It’s because most destabilising inputs to a MTB cause deceleration. And that causes the rider’s mass to apply a forwards force to the grips. The longer the stem, the more that force has a self-centring effect on the steering. A negative stem will do the reverse unless both hands are equally weighted.
that interesting, I hadn't thought about it.
Based on this - if I flipped my 35mm stem (I'm not actually going to..) - that would have a similar difference from going to that 35mm stem from a 100mm stem - that is to say, it would be gradually less stable, rather than suddenly unstable? on a 35mm stem and a bit of backsweep, the riders mass is applied pretty much in-line with the head tube?
I think you’ve got four main systems providing stability to a bike:
1. Trail
2. Jacking (head tube rising when you turn the bars)
3. Gyroscopic
4. Handlebar weighting
Trail and jacking increase stability with decreasing head angle and offset. Gyroscopic stability increases with rim+tyre mass. Jacking has the same effect at all speeds, the other two increase with increasing speed.
The handlebar weighting (tiller) stability does nothing if the grips are in line with the steerer (typical bars and 30mm stem). As the stem length increases it adds stability. As the stem length decreases it deducts stability. It isn’t proportional to speed but is to input force.
so if you have enough trail and jacking (by using a 58 deg head angle) - the instability caused by reversing the stem could (maybe) be offset (no pun intended)?
I still can't get my head round how decreasing offset increases trail.
Does anyone have a diagram 😉
Watching all those SIDs waggle around on the huck to flat is, er, educational.
Did anyone else think the Commencal looked really short after seeing the Donut?
I would like to see someone try to separate length from head angle. That wheelbase looks long enough to have a normal head angle and the bars far enough behind the steering axis to be connected by a backwards stem. Then it would be interesting whether that behaved well or whether a remote steering linkage would be required.
I don't think that would work very well. If you were tall enough to be able to weight the forks straight down through the steering axis it might but for anyone shorter than ideal it wouldn't be very nice to ride. I have no idea in reality, it's just a gut feeling that it wouldn't be quite 'right' for some reason.
Are you so sceptical of bridges, aeroplane wings not snapping and the existence of helicopters?
Speaking of... I'm still awaiting the Brighton i360 to blow over....
Now I'm no structural engineer, but I'm not fick or nuffink...and it just looks 'too thin' to be safe.
So there. If it blows over, they should have listened to me.
DrP
we don’t know if he was able to hit those lines due to additional familiarity
It was explained that it's one of his regular test tracks, so not an issue there.
We’ve been hearing for a while that many manufacturers don’t make the enduro bikes that racers would like.
We often hear that racers don't want the longer, slacker bikes that some of us punters are moving towards.
Watching all those SIDs waggle around on the huck to flat is, er, educational.
I got hooked on the huck to flat videos to see forks flexing then I looked at the rear suspension and now can’t take my eyes off the chains and rear mechs flailing around
That wheelbase looks long enough to have a normal head angle and the bars far enough behind the steering axis to be connected by a backwards stem. Then it would be interesting whether that behaved well or whether a remote steering linkage would be required.
I'm not sure what to make of the "Dangerzone" theory, but surely, someone, somewhere must have tried it.
https://www.pinkbike.com/news/exploring-the-relationship-between-handlebar-vs-stem-length.html
I'm a big fan of slacker head angles and balanced rear stay length but less so of much longer reaches & lower BBs.
I could see myself getting a frame with 60 degree ha in a few years.
Speaking of… I’m still awaiting the Brighton i360 to blow over….
Now I’m no structural engineer, but I’m not fick or nuffink…and it just looks ‘too thin’ to be safe.
So there. If it blows over, they should have listened to me.
have you seen it up close? its all perforated so the wind just goes straight through it. The really crazy thing is how it was built - they built the top section, lifted it up, then built the top-but-one section underneath it, lifted that up, and so on..
I think the article says it’s a track he knows well. Sure, it’s not a double blind randomised trial, it is interesting and it is entertaining, and I don’t doubt the result.
It's still pretty odd that he smashes the KoM (which presumably includes many of his own runs) on his first go that day
We often hear that racers don’t want the longer, slacker bikes that some of us punters are moving towards.
Yeah, there's a mix for sure. The PB video speaks to a bike company, which says that racers are conservative. And to Arron Gwin, who I would say is one of the conservative riders too.
Jordi at fox has mentioned before how some enduro riders alter their sag front and rear to effectively reduce HA. And I think one of the main drivers for racers trying 29er front ends on their 27.5 bikes was to slacken the HA a bit.
Really like Paul Astons’s bike. Looks great and is probably perfect for what he does.
RE the i360 being built that way...look..you're right...
But... I wouldn't have done it like that. I'd have lay all the pieces down on the beach.. got Norman Cook to have DJ'd a cracking set whilst workers/ravers bolted it all together laid down.. then hired a crane for the afternoon, pulled it up in one go, and then post-creted the base in.
But like I say..no one asked me, so hey ho..
DrP