Interview: Chris Porter – ‘The bicycle fork is so close to its design limit’

An interesting read, would like to see what his idea of a perfect fork would end up being and the associated cost and weight!

-Products like the intend stifmeister would appear to be fixing a problem that does exist (https://www.pinkbike.com/news/intends-new-stem-actually-improves-cockpit-stiffness-review.html)
-Replacing bushings with Linear ball bearings (see lefty), as used in WRC dampers?
-Wonder if there has been any data logging of the fork during field testing, identifying where the flex comes from
-Can a chassis (including wheels) be too stiff? (Moto GP a good example: https://motodna.net/flex-or-not-flex/)

I’m always interested in what he has to say. CP has spent so long looking at suspension that you’d be foolish to dismiss his opnions. On the other hand the counter arguments for tele forks are well established, the technology is understood, the products work acceptably for a good percentage of folk, and by and large they are reliable.

Also:
-Why does STW think I want to watch videos rather than read articles?

Shame the questions aren’t a bit more probing on the fork thing.

If we take his word that the main drawbacks of current single-crown forks are bushing binding as they flex, why not just make them a bit heavier again like the old Marz RC3 ti – rather than piss about bodging expensive dual crown “solutions”?

I’m sure those Marz forks (55 and 66 anyway) were more fluid AND stiffer than current stuff. Though the new Debonair spring in the Lyrik gets a fair bit closer, TBF.

I think he argued well why “bodging solutions” rather than continually binning and buying a replacement design has its place.

New Z1 takes the heavier stiffer approach (and also has fewer controls/features and goes back to relying on the shim stack instead, as I think he was suggesting).

I appreciated having the video… I listened to it in the bath yesterday morning… might not have got around to reading a full interview for ages, if at all.

legend

-Why does STW think I want to watch videos rather than read articles?

They did kindly go to the trouble of transcribing the interview for you, in addition to providing the video.

That’s a good point actually, if someone’s already dropped close to £1,000 on a Fox fork, it might make sense.

I suppose I can’t relate that easily as my limit is about half that, then I tend to sell on after a year or two when I see another bargain.

And I’m lucky I’ve not had any forks end up as scrap. Kudos to CP and Mojp for helping people avoid that situation, if that’s what he’s on about.

If we take his word that the main drawbacks of current single-crown forks are bushing binding as they flex, why not just make them a bit heavier again like the old Marz RC3 ti – rather than piss about bodging expensive dual crown “solutions”?

Because, we’ve all be conditioned to believing we need a 170mm travel trail bike to ride round Swinley forest, which weighs under 30lbs.

A 3kg single crown fork, isn’t going to allow for that.

(The axle thing is still stupid… we should have gone fatter, not thinner, and properly clamped at both ends.)

I remember an interview with Fabien Barel back when he was racing endruro, testing, the then new Fox 36, with a 15mm axle and saying it was a stupid idea to have more travel and a less stiff axle. He didnt win with fox though as they wanted us to all buy new wheels and forks to meet the stupid new stupid standard.

its not rocket science to see why. My old dual headshoc, while the damping was shit and it had its own personal gravity it was so heavy, the suppleness of the fork was bonkers in the chattery stuff – it couldnt bind. the needle bearings (for the first run when they were set right) were amazing.

The problem witha floating bushing is that it need to run on something and fitting all that inside a fork leg would be hard – Kashima the inside of a fork leg? an USD fork with a smooth steel upper tube to run the bushing on is probably the way forward. untill you dent it.

Because, we’ve all be conditioned to believing we need a 170mm travel trail bike to ride round Swinley forest, which weighs under 30lbs.

A 3kg single crown fork, isn’t going to allow for that.

Won’t a dual crown enduro fork be 2.5kg or more anyway?

More than one way to skin a cat I suppose, and I guess CP is focusing on what he can achieve and offer as a product.

Yep, but like he said, it’s not the right answer, but it is an answer nevertheless.

All one big balancing act I figure. Much like riding a bike!

honourablegeorge

Member
They did kindly go to the trouble of transcribing the interview for you, in addition to providing the video.

Nothing loaded beyond the video first time…..i’ll blame the “upgrade”

chakaping

CP is focusing on what he can achieve and offer as a product.

That’s exactly it – he can’t afford to design something liek that Dave Weagle fork with his small operation.

The problem witha floating bushing is that it need to run on something and fitting all that inside a fork leg would be hard – Kashima the inside of a fork leg? an USD fork with a smooth steel upper tube to run the bushing on is probably the way forward. untill you dent it.

Plasma coat the liners, although being the mtb industry, they’d do a shit job of implementing/validating it.

Without going to a dual crown fork (which makes fitting in a back of a car tricky and turning tight corners):

-1.5″ straight steerer
-Intend stifmeiester (no point having a stif fork, if the system is a flexy mess)
-20mm axle with pinch bolts
-Linear bearings
-Decent amount of oil in the lowers, 10ml is a pitiful amount!
-Luftkappe debonair system, coil is an option (but more weight….)
-Shim stack system with adjusters that are used for polishing the damping
-Mudguard mount on the fork lowers
-180/200mm post mount, kill of this adapter nonsense (see system stiffness)

arnt we just forgetting that a bike isnt stiff.

The issue is that it effects function so you could stiffen up or change the way in which it guides to solve that issue.

these look interesting.

https://www.bikemag.com/news/introducing-the-message/

The axle thing is still stupid… we should have gone fatter, not thinner, and properly clamped at both ends

Spesh E150

Presumably as head angles get slacker this problem gets worse as the bump force is hitting the fork at a shallower angle than before. Does this not mean that more of the force is not along the plane of the fork that the suspension move along

Plasma coat the liners, although being the mtb industry, they’d do a shit job of implementing/validating it.

therein lies the problem – Quality control and costs. you actually want something simple to implement and mass produce.

The current system is easy and allows for a bit of tolerance but forgoes outright performance. But who gives a toss about performance when you can ‘design’ a new one paint it red and charge a grand for it and still sell loads! we as consumers are muppets.

we as consumers are muppets

There used to be in the glory days factory race teams etc with stuff of dreams budgets

Nowadays as long as you look factory its ok

Watch the huck to flat videos on the new Pinkbike video reviews. Jesus, single crown forks are bendy!

Statement 1

“Suspension damping on a bike must be progressive because there is no chassis weight, the sprung weight vs the unsprung weight is almost the same. Digressive damping is bollocks. Progressive damping is really difficult to do with valves that give you an adjustment”

* First of all, the unsprung weight vs the sprung weight is clearly not almost the same. An average rider weighs, what 180lb? So that’s about 20 times heavier than the unsprung weight. I’m not sure that the argument that a lighter chassis needs a more progressive damper setup holds weight either, Baja trucks and rally cars have crazy progressive suspension setups to deal with the huge forces imparted by the tonnes of metal flying around.

* The speed sensitive dampers can be made to be digressive during the transfer from low speed to high speed or progressive surely? See https://www.pinkbike.com/news/tuesday-tune-ep-5-high-and-low-speed-damping-part-1-2016.html Most high speed adjusters are based on preloading the shimstack, in reality your shimstack offers no extra benefits that a adjustable preloaded shimstack does not, they are exactly the same – one has a little more adjustability. Twin tube shocks are a little different, but these still have speed sensitive main piston shimstacks. The EXT shock is positionally progressive, as it works in a similar fashion to WRC and Baja truck internal bypass shocks. The damping ramps up towards the end of the shock stroke. This has nothing to do with the speed sensitive dampers, of which EXT offers just as many external adjusters as a DHX2.

Statement 2 “The fork twists due to the separate functions of the legs”.

* Can we see the data that shows this effects what goes on in the real world? The MX race forks are all separate function forks, eg the Show S.F.F. Do they not have the same issues because they are overbuilt?

Statement 3 “Forks are too flexy”

* Dual crowns have always made sense to me – long travel single crowns seem silly, forks as rightly Porter insinuates aren’t burly enough. But that doesn’t mean to say that some flex isn’t good.

5/10 for the interview – Porter knows his stuff but he shot himself in the foot in the first half of the interview IMO.

pretty much all of that is irrelevant to me – I’m such a crap rider that I wouldn’t be able to tell the difference.

“e speed sensitive dampers can be made to be digressive during the transfer from low speed to high speed or progressive surely?”

I might add, by simply tuning the shimstack, as high speed adjusters simply alter the point at which the high speed circuit takes over.

I might add, do the EXT shocks really have progressive speed sensitive damping? As surely that is going to make small high velocity bumps harsh? The point of the EXT shock and internal bypass shocks on racing trucks and offroad vehicles is that the high speed can be allowed to blow off, so the vehicle soaks up small chatter but under deep impacts the compression ramps up massively?

An average rider weighs, what 180lb

I think you better take a closer look at the “average” MTB rider

Vorsprung has a much different take in terms of external adjustments or “features” as Porter likes to call them.

@10:23 “We commonly get requests from people for customer tuning stuff, which is fine – we can do that by the numbers but if you haven’t managed to get the most out of your external adjusters, we can give you something that is better than that – but it’s probably not as good as it could good be. What we really want to see from our customers is that they have made some effort to setup their suspension”.

That sounds a bit different to Porters rant about “features” and the idea that everything can be done with just shimstacks and presumably his company tuning those for you.

Starting at 07:20

“Speed sensitive damping that will give you a plush initial stroke but ramp up to resist bottoming out. So ramp up how? Is it a more progressive damper curve in terms of generating disproportionally higher forces at higher speeds, typically not because that will give you something that becomes quite harsh and very unsupportive initially or is it something that ramps up towards the end of the stroke, obviously that is impossible (for speed sensitive dampers)? You cannot use any combination of shimstack that actually gives you less resistance at the start of the stroke than at the end of the stroke (you can of course use other types of damping setups to do this, eg internal bypass shocks”.

Oooops.

I really wish that mtb journos knew enough to actually critically appraise what they are being told by people.

Well this has opened my eyes on how to really enjoy my occasional solo evening pootle when the kids have gone to bed and I’ve done all the chores.

Perhaps it’s not relevant to you.

I do think mtbers should get a bit more clued up though, I used to ride with a bunch of motorsports engineering unergrads when I was at uni – so silly bollocks annoys me.

Hmm. I used to have boxxer teams on one bike and lyric dhs on another bike- very similar forks to the point of having interchangable parts, both 35mm, both 20mm axle, one dualcrown 200mm and one singlecrown 170mm, used to ride the same things. Could I tell any difference from bushing bind through flex? Nope. Maybe I would have, had someone on the internet told me I should though.

Now I’m no pro but I can say I ride harder than most people (not that hard a target) so I figure if it’s not a problem for me it’s not going to be a problem for most people. But if it is, isn’t it a shame that Fox won the bloody stupid standards war and 15mm became the universal fitment (except ironically on Fox 36s).

Oh, and Chris Porter happily sold them for years. Call me a cynic but I doubt he’d be saying this if he was still making a living selling Fox 34s to people.

Northwind, I’ve felt for a while that there are only a few players in the industry that will go and try to give you a detailed technical breakdown of why a company is doing things the way they are and treat you as an adult instead of simplifying our spouting silly nonsense.

Darren at PUSH Industries, Steve at Vorsprung and to a lesser extent the guys at TF tuned. Steve is particularly great, it never feels like he is trying to sell you a product that he doesn’t think won’t make a difference to you (his attitude towards custom tuning is telling) and his pinkbike tech Tuesday videos are just great. On top of that, if you have more technical questions in regards to his video – you will get an essay back as a reply. He also rides a high pivot point bike, so I like him hahah! He’s also a proper engineer.

It feels like Porter is trying to sell me something, which is a shame as I quite liked the technical aspect of the EXT Arma V3 shock. Sometimes I feel like going an setting up my own mag, as it appears that no one in the UK mtb media cares for critical technical appraisal of various ideas and products in the industry.

* First of all, the unsprung weight vs the sprung weight is clearly not almost the same. An average rider weighs, what 180lb? So that’s about 20 times heavier than the unsprung weight.

You are suspended weight though, to some extent. Depends on the situation but I see what CP and you are both getting at.

Ride an E-bike or a loaded up bike and you see how much difference adding a fairly small amount to the chassis weight makes. 5-6kg has notable inertia there and builds up plenty of momentum at 15-20mph.

You are suspended weight though. You balance your weight between hands and feet, ride light and move around and have really good adjustable suspension.

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.

The only thing that I can think of that Chris might have been banging on about are the high speed rebound adjusters in twin tube shocks, which causes linear to digressive damping curves. Not quite optimal according to some including vorsprung, not a huge pain either. Steve still rides a CCDB, despite having the technical know how and kit to custom tune any shock on the market for his needs.

Sorry, I’d already edited that to be a bit less egg-suck sounding (the bit you quoted) ^

True about low/high frequency impacts being different, overall though I don’t see the rider as being a rigid mass in the same way a heavier main frame with lighter suspended ends would behave. Shades of effect rather than absolutes.

Damping curves etc to suit … I’ll happily leave that to others to think about : )

and to a lesser extent the guys at TF tuned.

Steve is particularly great, it never feels like he is trying to sell you a product that he doesn’t think won’t make a difference to you (his attitude towards custom tuning is telling)

Flooksy was actually exactly the same if you spoke to him in person. He’d completely understand what you wanted from a shock tune and why you wanted it no matter if some of those traits were completely the opposite in some respects to what was fashionable/current thinking with suspension at the time or the products he sold. I heard he’s no longer at TF though. Shame. The guy’s a true gent. I’ve no idea if TF still have a similar ethos to Tim’s having not used them in a decade.
CR has always been the opposite of that. Very absolute about what’s wrong with everything other than his thinking and tends to get his own way. Whether that’s advisng WC racers to run their rebound so slow it never fully recovers through an extended rock garden or getting punters who can barely handle their current bike onto one a foot longer that they’ll never be able to handle properly in a million years. His blinkered thinking has tripped him up more than a few times (Boxxcart anyone?) and yet folk still blindly listen to him.
The body language in that interview was made for radio.

I used to have boxxer teams on one bike and lyric dhs on another bike- very similar forks to the point of having interchangable parts, both 35mm, both 20mm axle, one dualcrown 200mm and one singlecrown 170mm, used to ride the same things. Could I tell any difference from bushing bind through flex? Nope. Maybe I would have, had someone on the internet told me I should though.

Now I’m no pro but I can say I ride harder than most people (not that hard a target) so I figure if it’s not a problem for me it’s not going to be a problem for most people.

I think you’re missing the point here somewhat. Chris was talking about the bushing bind from a stiffer dual crown fork chassis. No disrespect to you but you most certainly don’t ride harder than most people a 200mm DC fork is intended for. I weigh a lot more than you and ride harder on a 100mm hardtail than you do on a 200mm DH bike and I wouldn’t consider myself as someone who rides half as hard as the intended user of a 40 or Boxxer. (I’m talking about top 20 World Cup DH racers and Crankworks/Fest/Rampage riders incase I’m not making that clear). Bushing bind very much is a thing with the current DC forks at that level. It’s still apparent under an old guy like me who weighs 2st more than most of those riders only I just don’t happen to care about it.

For most folk bimbling down local enduro stages No. You’re right they absolutely do not need to worry about it. But that doesn’t mean it’s not present or that folk will buy a smoother system if it was put into production. Look at this forum for evidence. Consistant whining from not particularly skilled or hard riding punters about Lyriks/Pikes etc. needing improved and folk happily shelling out hundreds on top of the cost of an already overpriced fork for slightly different air shafts, dampers and coil springs. That won’t change. it’s golf.

Very absolute about what’s wrong with everything other than his thinking

Just so we’re clear, you’re talking about Chris Porter, not yourself?

I’m actually openmindedAF. I just happen to be right an awful lot 😉

Geex, Porter had me run my DHX2 almost closed on the low speed rebound an wide open on the high speed rebound once. Which would be completely the wrong way round to what Vorsprung suggest, maybe Porter was having a bad day or I misheard him?

Again, I really don’t get him sometimes – quite a few of his ideas work, quite a few don’t.

“I wouldn’t consider myself as someone who rides half as hard as the intended user of a 40 or Boxxer. (I’m talking about top 20 World Cup DH racers and Crankworks/Fest/Rampage riders incase I’m not making that clear)”

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.

You’re spot on about the golf side of it, mind. Which is weird because of how that contradicts the other stuff.