I think Geex might be right about the dual crowns to be honest, he just put it badly and rather meanly towards you there Northwind tbh.

A lot of issues would be solved if those on long travel single crowns gave up the ridiculous notion of having a 170/180mm fork in a 2kg package and then wondering why the crown debonds and creaks. You get lower axle to crown lengths with ducal crowns as well.

If durability of the product is important to people we shouldn’t be riding single crowns.

I actually like Chris. The first time I met him he gave me a shock bolt from an intense M1 at the bottom of a muddy Welsh DH track back when he was their importer to sort out my bike. I’ve had a laugh with him and a mutual friend a few times since but he’s one of those guys that came from motorbikes so sometimes has worse bike handling ideas than silly old TJ.

I quite like him as well, I just think he’s bonkers, I never know quite where he’s at with his thinking – he’s a bit hit and miss sometimes.

Porter is right. The telescopic fork is a kludge – a highly refined kludge, but nonetheless a kludge.

Everyone is used to its characteristics so the flaws tend not to be commented on.

One big one is brake dive. It’s possible to minimise it and then your fork does not need so much travel, and so can be lighter. So why isn’t it done? Probably because brake dive is seen as a feature now and not a bug.

You can’t cut down travel because you’ve eliminated brake dive. All forks and shocks pack down to an extent in repeated hits, even when rebound is setup properly. If you cut down the travel the fork will not be as comfortable or as grippy, period. There is no replacement for displacement when it comes to off-road suspension. Steve goes into detail about rebound, pack down and fork harshness in his videos – watch them.

The problem with linkage forks is that no one has managed to get a good axle path that mimicks the rearward path of a telescopic fork on a bike with a slack head angle, in a package that is stiff enough, has an equal amount of travel for a given axle to crown, is not crazy heavy and is reliable. Axle path matters – Commencal have shown that, Steve at Vorsprung knows it as well and bought a Deviate (as has our own TomHoward).

Someone one day will do it, but I had Antonio at Linkagedesign knock me up an axle path analysis of that linkage fork mentioned in the interview. It’s rearward for the first half and then vertical – not great for attenuating hard hits that go deep into the travel that are not directly upwards. I’m sure the STW journos will sing it praises when they ride it for 2 days in Spain or wherever though….some of them might even buy one and will then be seen a year later skipping about on telescopics again after they realize it’s shit.

Aye, right. The intended users are the paying public, rockshox and fox only care about top 20 wc racers and the like for marketing, not as actual users. And likewise Porter couldn’t care less about them, and he surely doesn’t expect to influence them through this video.- he’s after Bob Slowlaps’s credit card details.

Sorry dude. missed your reply.
There was no contradiction. My point was that 99.9% of punters don’t need a DH bike or a DH fork. DH racers do. (And I don’t mean Bob the eventist but racers who live and breath DH aiming for success). Same as Bob Sliceshot doesn’t need phase one blades to play half a round on a Sunday with his old mate Wullie Sandtrap but it doesn’t stop the two of them popping in the Pro shop to deek at them and splaff shit about them in the bar and end up buying a set when they see an offer they can’t refuse in golf monthly or a PSA on http://www.Golffairwayworld.com

Ps. poor Bob.

Porter had me run my DHX2 almost closed on the low speed rebound an wide open on the high speed rebound once.

Yes, I didn’t get on with his rebound settings at all. They obviously work for him, and he thinks they make him quicker (a lot of his stuff comes from stopwatch timings rather than feel).

on a DHX2 he was advising LSR of 4-9 (against fox 17-19). I was fiddling with LSR and HSR without ever being completely happy until I used a shockwiz in the end and got to 16. Other settings were close to Chris’ recs.

Likewise for the 36RC2 He was recommending rebound at 14-17 (against Fox 7 and my current 9)

geex

Member

My point was that 99.9% of punters don’t need a DH bike or a DH fork. DH racers do. (

Sure, and I agree- but since the 99.9% are the market that makes it possible for Fox and Rockshox to make dh forks (and for Chris Porter to sell Geometrons) and the 0.01% aren’t buying what he’s selling or probably watching his videos, it’s kind of irrelevant. And I think it’s pretty bloody obvious that when I talk about myself I’m part of the 99.9%!

“You can only use your weight like that on low frequency inputs, on high frequency chatter you essentially become a rigid mass and the suspension does the work.”

I’m only a few rides in on mine, but try an ebike and you’ll immediately see (feel!) that that’s wrong – it’s quite remarkable how much better the suspension works!

I agree with Chris that telescopic forks the way they’re making for MTBs are a bit of a bodge – they’re fine for someone like me but I shouldn’t be the target audience. I also agree that he a has long history of contradicting himself!

on a DHX2 he was advising LSR of 4-9 (against fox 17-19). I was fiddling with LSR and HSR without ever being completely happy until I used a shockwiz in the end and got to 16. Other settings were close to Chris’ recs.

Yeah, I have a Geometron with a Float X2. Chris’ recommended way more LSR than Fox’s recommendations. I started with Chris’ recommended settings and I’ve been gradually winding out the LSR and the bike, to me at least, keeps feeling better. I’m sure he has his reasons, but interesting that you found similar to me.

“You can only use your weight like that on low frequency inputs, on high frequency chatter you essentially become a rigid mass and the suspension does the work.”

I’m only a few rides in on mine, but try an ebike and you’ll immediately see (feel!) that that’s wrong – it’s quite remarkable how much better the suspension works!

I agree with Chris that telescopic forks the way they’re making for MTBs are a bit of a bodge – they’re fine for someone like me but I shouldn’t be the target audience. I also agree that he a has long history of contradicting himself!

I’ve ridden a lot of HEAVY downhill bikes, with good suspension (either coil or very well looke after air) I’ve never thought that the suspension was working better because of the weight. The bikes simply get thrown off line a little less because of the weight.

Granted, E-bikes can still be a bit heavier than those! So I can’t be certain of my own experience compared to yours Chief!

I’m not sure the answer to suspension woes is to add 10kg to a bike anyway or for us all to jump on e-bikes, a better response would probably be to run coils and improve coatings and seals.

99.9% of punters don’t need a DH bike or a DH fork. DH racers do. (And I don’t mean Bob the eventist but racers who live and breath DH aiming for success).

Yes and no really. People who race DH for fun* would probably find that they were quicker and enjoyed it more with 8 inches of travel, but the only bikes in that sector are DH bikes designed for the fast end of the field. Ideally they would like a different bike. But nobody is making bikes and forks for the slow end of the field so it’s hobson’s choice.

* presumably they still do and haven’t all gone enduro? When I raced (slow old git category) DH, enduro didn’t exist, and although racing on my trail bike was OK, a DH bike was more fun and faster. But I got a secondhand one, I wouldn’t have splashed out on a complete brand new bike**.

** would have been something like an Iron Horse Sunday.

“I’ve ridden a lot of HEAVY downhill bikes, with good suspension (either coil or very well looke after air) I’ve never thought that the suspension was working better because of the weight. The bikes simply get thrown off line a little less because of the weight.”

If you were an engineer or physicist you’d see the contradiction in your statement. 😉 Every time you hit a bump that bump tries to throw the bike off line. If that impact is perfectly elastic then it’ll be moved off line the same amount regardless of the mass of the bike – in the case of hitting large rocks then anything which absorbs or damps the collision will be part of the bike, mostly the tyres and suspension (obviously there’s a small amount of wheel and frame flex too).

If a heavier bike is thrown off line less then that means the tyres and suspension are adding additional compliance by working better. QED.

Good point.

Are we sure that some of the difference, is that a little bit of extra mass holds speed better as well? I’m still not convinced that a bit of extra weight overcoming seal friction makes the huge difference that everyone claims it does when they move to a heavier bike. Or whether something else is going on with the ride quality that they are feeling?

If weight improves the ride quality of the suspension, then surely lowering friction by moving to coil would have the same drastic effect that everyone talks about with e-bikes – or even just reducing the spring rate. But moving to coil doesn’t have a drastic change on chassis balance during hard repeated hits, you just get a little bit more grip and midstroke support, along with a bit less harshness through the bars.

Then again, as you rightly point out I’m not a physicist or an engineer, I’m good with maths though – so if you send me a link I could get my head around it.

I’ve ridden a lot of HEAVY downhill bikes, with good suspension (either coil or very well looke after air) I’ve never thought that the suspension was working better because of the weight.

Yeah. but you’ve missed the glaringly obvious difference between a 50lb DH bike and a 50lb Ebike.
Let me spell it out for you.
a 50lb DH bike has a 13lb tops frame incl cock shock a heavy fork, heavy wheels, tyres and tubes, heavy components. so that weight is distributed fairly evenly. Without ading weight somewhere intentionally there’s no other way to get a DH bike over 46lb
Whereas a 50lb Ebike has a 21lb frame with much lighter wheels, tyres and components.
But that’s not the whole story.
DH frames are overbuilt throughout with heavy coil shocks sat centrally (say 1lb heavier than the Ebike’s air shock)
(using shimano steps as example as it’s the lightest Ebike motor system by a fair way) Ebike frames also have the shock weight positioned centrally but also have 14lb of motor and battery mounted low and centrally.
Weight distribution makes a huge difference.

This summer I had been riding my Ebike far too much and neglecting some of my other bikes. I had a holiday to the Alps booked so took my DH bike out for a shakedown/get aquainted again uplift day the weekend before the trip and it felf crazy light. (it’s 35lb, the Ebike is 47)
As a little experiment on the first day in the alps after the first mornnings riding I put a Dakine hotlaps bag filled with spares and DH tube onto the DH bike below the BB. the bag weighed 2.5lb. The increase in stability and improvement in grip and suspension was instantly noticable. I’m a cynical bastard and wouldn’t have believed it if someone had told me this.

The thing is I would have re-calibrated my riding to the lighter DH bike anyway. and as it happens the Dakine bag was hit by a rock on a highspeed section of DH track 4 days later and split so I ended up riding the DH bike again without the extra low weight just fine.

I owned 48-51lb DH bikes for well over a decade and rode the shit out of them so I know very very well how one handles. it’s NOTHING like my 170mm 47lb Emtb handles. And I’m talking about when descending with no assistance or pedalling UPHILL with it switched off.

Running the same tyres my 47lb Emtb is more stable and offers more grip than either of my 35lb DH bikes but is far far more nimble, easier to popt and lay over in the air than those old DH bikes of around the same weight were . For me. the sweetspot for Emtb handling would be something around 42-45lb in weight. Everything is a compromise but that sort of weight for me would offer the best mix of nimbleness and stability. There are already Embts aroind that weight but they either aren’t burly enough or use less powerful motors and smaller capacity batteries.

FWIW I think when Emtbs get much over the 50lb mark they start to handle more and more shit all round too. Stable though obviously.

God damnit, I want a **** e-bike now.

Look at what you’ve gone and done.

So, any high pivot e-bikes out yet? 😀

Edit

The Bergamont still has one of my favourite suspension systems on an eMTB, and I thought we would see more designs like this, but it turns out that Haibike have a patent for high pivot idlers on e-bikes and they are featured on many machines in their range.

Aghhh!

Hahahhaha 😀

sure as day every time Chris Porter opens his mouth in public discussion ensues, wallets open and money gets spent elsewhere.

Lucky he has his music and art

a 50lb DH bike has a 13lb tops frame incl cock shock

Is that a special thing that provides extra knob fiddling?

raybanwomble
You can’t cut down travel because you’ve eliminated brake dive. All forks and shocks pack down to an extent in repeated hits, even when rebound is setup properly. If you cut down the travel the fork will not be as comfortable or as grippy, period. There is no replacement for displacement when it comes to off-road suspension…

I’m not going to argue that’s there’s no replacement for displacement. That’s a given.

But if your brakes are diving, you’re using up displacement that could be used for suspension.

IN many ways it’s a shame that cartridge forks became so popular. In the 70s, I used to tune motorbike forks for myself and mates by fiddling around with shims, drilling ports, and making up magic potions for suspension fluid. It’s amazing what a few small adjustments can make, and they can be done for pennies if you don’t mind getting your hands oily, ie accessible to any mechanically competent rider.

Epicyclo, the Grip 2 damper cartridge would be great in that regard if Fox UK were actually willing to provide the spares for home servicing – as it self bleeds!

Do you think we could package Tom Killeens head to hub idea to eliminate bushing bind, on an mtb fork?

https://books.google.co.uk/books?id=84hF-qoR5I8C&pg=SA7-PA30&lpg=SA7-PA30&dq=telescopic+fork+that+resists+brake+dive&source=bl&ots=F-z2uGS9Lm&sig=EwfkEChpDGlkSuR1eStCtTUarbY&hl=en&sa=X&ved=2ahUKEwjV8pqK3JffAhWMqaQKHd7eCgUQ6AEwCnoECAAQAQ#v=onepage&q=telescopic%20fork%20that%20resists%20brake%20dive&f=false

Scroll down a bit to find the description. It seems like it would add a lot of complexity an weight to a bike still – and the frame would have to be designed ground up for it.

For interested parties, here’s a quote from Steve on his Pinkbike tele vs lever video

There was no need for the rectangular stanchions on that, it had the scissor link that kept everything aligned. The problem with that design was the axle path was a bit whack and didn’t follow the steering axis. Never got to ride one unfortunately but having an anti-dive characteristic alone also doesn’t guarantee that it’s actually better under brakes. What happens if you have so much anti-dive that it actually extends? What happens if you have exactly 100% anti-dive and the front end doesn’t move but the rear end rises due to the forward weight shift? What happens if that anti-squat rate varies in a particular way, does that make it more harsh or less? What if the damper isn’t low enough friction, or isn’t reliable, or blah blah… there are a ton of variables involved!

He also seems to think that an axle path that follows the steering axis is desirable as well.

Isn’t that Killeen thing basically just a McPherson strut?

Edit: Which if I’d read the next page I would have noticed that’s what it said.

RaybanW, sorry, do you have a link to the article? I wouldn’t mind reading it

https://www.pinkbike.com/news/tuesday-tune-ep-8-why-were-riding-telescopic-forks-2016.html

The comments are worth wading through as well, Steve usually delves a bit deeper when he posts on the various forums.

It’s interesting that Motion-Ride came out shortly after this video, with their own video responding directly to Vorsprung essentially stating that although their C shaped axle path was not what riders wanted now (not that C shaped axle paths are **** terrible) – they could move to a linear one on the production sample. Now it’s almost 2019 and they are rocking a slightly rearward to vertical axle path, because…..stability (totes not that they can’t design a fork worth a ****, that has sensible anti-squat values with a more linear axle path).

EDIT

To get rid of dive you basically need a linkage style fork, or a linkage on a tele. The problem with them is the links are far too short, and usually leading instead of trailing, with the result you have an axle path that results in very fast change to the steering geometry once out of the sweet spot.

But the telescopic fork, being the kludge that it is, can benefit from another kludge, assuming it is suspended on air. All that is needed is an auxiliary air chamber and a cutoff valve operated by the front brake lever. This can be tuned to vary the amount of dive to the rider’s preference. Again, something I used to do to try and get decent performance out of the dire forks fitted to 1970s motorbikes.

There was a good factory implementation of this on the H-D tourers like the Electraglide which made it surprisingly capable for hard riding.

My personal favourite is the Telelever system on the oil cooled BMW twins. The suspension does not have to be compromised for the braking. Implementing that on bicycle frames may be a problem because they are not 3 dimensional enough to get enough lateral rigidity – or do they need that rigidity?

I think they do need it, there isn’t enough rigidity in my 36 – I feel much more at home and confident behind a set of dual crowns.

To get rid of dive you basically need a linkage style fork, or a linkage on a tele. The problem with them is the links are far too short, and usually leading instead of trailing, with the result you have an axle path that results in very fast change to the steering geometry once out of the sweet spot.

I wonder if that’s partly why Motion have stated they haven’t tuned out all the dive. They don’t provide any of the numbers for anti-dive, leverage ratio or axle path on their website though (I wonder why?) – look at this video – does that look like considerable dive to you before he/she stops at the stream?

On top of that, the fork is completely unservicable by home users, we know little about how the damper works and the spring is only adjustable on preload.

But of course, STW raved about it on their 1 day test – without mentioning any of this.

I wonder if that’s partly why Motion have stated they haven’t tuned out all the dive. They don’t provide any of the numbers for anti-dive, leverage ratio or axle path on their website though (I wonder why?) – look at this video – does that look like considerable dive to you before he/she stops at the stream?

I don’t think the axle-path and anti-dive aspects of the linkage are particularly linked, so you could achieve as much as you wanted of the latter without affecting the former, if you see what I mean.

And, proponents of these forks rather play up the ability to play with the axle path. I have never quite seen why the axle path must be exactly parallel with the steering axis even on a telescopic fork. (Although of course it isn’t any way given the amount the things flex, to replicate that on a rigider linkage fork you would have to build some offset/curve in).

That Motion fork – my first thoughts are no thanks.

It looks like brake dive would depend on where in the arc of suspension movement the brake was applied. (I’d like to see a side on drawing of the brake side to be sure)

Reminds me of the problem Vincent Girdraulic forks used to have in racing when they had been modified for more travel. They’d go stotting off into the undergrowth on zigzags if you transitioned from full throttle to full braking instantly. What was happening was the fork was at the top of its travel (beyond factory recommendation) and the angles were wrong, so the braking force overpowered the suspension and locked it up. It only happened in those circumstances if I remember it right, so it was a puzzle for a while. Lesson: never try to outsmart Phil E Irving’s designs. 🙂

A trailing link fork is always going to be more prone to brake dive unless there is a linkage to feedback the brake forces to the non-suspended part, ie solidly bolting the brake to the fork arm is not optimum. (Eg Vespa scooters). The advantage of a long trailing link is it is easier to design for less radical geometry changes. That works to some extent for a long leading link too, and it’s easier with leading link to cancel braking forces.

(NB I am specific about long links, short is another story).

The thing is though, a lot of the anti-dive things fitted to motorcycle forks were blanked off by riders who wanted the bike to dive on the way into corners. It can be a good thing.

Exactly what Kayla said.

There’s no way I would want to switch to a fork that didn’t compress under braking after 25 years of riding one that does and knowing exactly how my fork behave under braking forces.

also. Other than these guys…

Who on earth is braking in any situation ever while their fork is using full travel?

.
And, proponents of these forks rather play up the ability to play with the axle path. I have never quite seen why the axle path must be exactly parallel with the steering axis even on a telescopic fork. (Although of course it isn’t any way given the amount the things flex, to replicate that on a rigider linkage fork you would have to build some offset/curve in).

The parallel axle path with current head angles leads to nicely rearward axle paths, that are good for most of the bumps apart from very vertical or very horizontal inputs. My opinion, is that the human body is much better biomechanically equipped to handle and offset geometry and centre of gravity changes, so we shouldn’t be moving away from prioritising bump attenuation. My Commencals rear axle path attests to that, since moving to a high pivot point bike I have been consistently quicker though regular sections – by quite a considerable margin. I simply don’t get the same harshness transferred through the bike that I have done with other designs.

The thing is though, a lot of the anti-dive things fitted to motorcycle forks were blanked off by riders who wanted the bike to dive on the way into corners. It can be a good thing.

I’ve mentioned this before, but TJ was adamant that the change of weight distribution was not down to the fork dive.

@Raybanwomble
Top tip: Stop listening to motorcycle handling advice from a man who loses motorcycle handling arguments with motorcycle riders on the internet and doesn’t actually own or ride one.

I’ve mentioned this before, but TJ was adamant that the change of weight distribution was not down to the fork dive.

They’re linked though, surely? One can cause the other and vice versa, at least that seems the case from the dozen or so trackdays and handful of races I’ve done 😉

The parallel axle path with current head angles leads to nicely rearward axle paths, that are good for most of the bumps apart from very vertical or very horizontal inputs.

Well yes, so why weren’t more rearward paths considered when things were steeper? Why stick with exactly 0 degrees when you could experiment with a degree or so either way built into your crown forging(s)? You would of course also affect trail. But you would think that the ideal trail for when you have maxed out your fork travel might well be different from when you are cruising along smooth ground. I am just curious why this doesn’t appear to have been experimented with in the field of telescopic forks. (Maybe it has?)

Change of weight distribution happens with rigid forks, dive doesn’t.

I thought they were, but maybe a physics type can educate us.

PM me if you guys ever want to go and set up your own magazine, with blackjack and hookers.

https://www.youtube.com/watch?v=RpVBYRw60m8

Well yes, so why weren’t more rearward paths considered when things were steeper?

They were, DH settled on around 63 degree head angles well over a decade ago not just for handling reasons but bump absorption as well. Steep bikes do feel harsher on steepish terrain, but supposedly once you start getting past 62 degrees then the fork starts to flex upwards and shock absorption is compromised. Santa Cruz has stated this as a reason for not going past 63.5 to 64.5 degree head angles in the past and that these numbers seemed to be the sweet spot.