So I can see how the wider headtube might make a larger contact point for welding and a stiffer frame, but how does the taper add stiffness to the fork? Should the bigger headtube with a non-tapered steerer be the same in terms of stiffness then?

Can anyone explain?

TIA

Wider tubes are stiffer. The top of the steerer tube remains the usual size for stems plus theres little flex at the top.

Fork is a big (canti)lever.
Base of steerer is near point of maximum bending moment.
As a big simplification – there is more to be gained in terms of stiffness by increasing the diameter of a tube compared to just making a small tube thicker.
The headtube probably makes less difference than the steerer (it is just bigger to fit the fatter steerer).

Magura dual braces are much more effective at adding stiffness…

Magura dual braces are much more effective at adding stiffness…

Torsional stiffness – yes.
Fore / aft bending stiffness under braking – no.

What’s the reason for tapered, and not just straight 1.5?

1.5 has been and gone – significantly heavier for minimal gain – for most applications more metal where not needed and also needs non standard stems.

The extra stiffness is needed (? disclaimer – I actually still run a standard steerer) at the point of maximum bending – not at the top of the head tube.

I am an engineer (a proper one, not that that means much) and I agree with Mick! Max bending moment is in the region of the lower headset cup, and stiffness is best gained by increasing tube diameter, within constraints.

1.5 has been and gone

It hasn’t, not at all, would take a 1.5 over tapered all day.
Would be more than happy to accept the insignificant weight gain over tapered for the freedom of choice in headsets, in fact 1.5 should be the standard for all headtubes imo.

Significantly heavier, thats a bit dramatic, I’d estimate 50 – 100 gram penalty over taperd, something like that?

triangles aint it. Which one is most likely to fall over in a storm? The Pyramids or the PO tower?

Significantly heavier, thats a bit dramatic, I’d estimate 50 – 100 gram penalty over taperd, something like that?

Bigger steerer, bigger bearing, bigger headtube and all where it isn’t needed – I’m sure if you’re designing a frame saving 100g is a big deal.

A proper engineer will tell you its stiffer – but you wont notice it. Its a tiny difference that you can measure / calculate, but I would be very surprised if you can feel it.

Marketing sells stuff.

If I were cynical I’d say it was to ensure that most decent frames and forks prior to 2011 are now obsolete and all the new “better” performance standards are to ensure you’ll be needing a new bike or at least a major part of one each “season” (I bike all year round but now there’s a season, apparently). Another bit of me says it was for sound engineering principals that we all benefit from like 29/650b, 1 x 10, external BB etc etc etc. It’s probably a bit of both. I have to say increasing sanction width seems a better way of improving fore aft stiffness but I’m no engineer..

Bigger steerer, bigger bearing, bigger headtube and all where it isn’t needed – I’m sure if you’re designing a frame saving 100g is a big deal.
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On a XC bike yeah, on a 30lb trail bike the weight penalty wouldn’t make a blind bit of difference, would be happy to incurr weight penalty for wider choice of headset.

Fore / aft bending stiffness under braking – no.

can’t see that is true if you have the fork legs in the equation – the dual bracing is going to reduce the legs bending, making it more likely that the fork will act like a piston, and so therefore less torsion at the crown.

I have two 120mm XC forks and the 1 1/8th QR Magura is much more piston like when you hit something in front of you than the tapered, 15mm RS.

increasing sanction width seems a better way of improving fore aft stiffness

It is useful but if you keep stiffening the stanchions and lowers w/o changing the CSU you just get more stress at the crown where the leverage is highest. Overall fork stiffness is largely about keeping the lowers from flexing and binding so improving suspension performance.

Ah! Not considered fore/aft movement – was concentrating on rotational stiffness for tracking accuracy not thinking it all through! Really helpful, thanks

I read that tapered partly won of plane 1.5 as it meant we didn’t change the stem standard as well

I thought the change was mainly about making the frame stiffer/stronger in a major stress area

But as mincer its just a pain. Although with a wheel size change as well everything is doubly obsolete

So why don’t they taper the stanchions?

So why don’t they taper the stanchions?

because they are sliders

A proper engineer will tell you its stiffer – but you wont notice it. Its a tiny difference that you can measure / calculate, but I would be very surprised if you can feel it. but you’d never feel it
Marketing sells stuff.

This x1000

bigrich – Member

So why don’t they taper the stanchions?

because they are sliders [/quote]

Why not taper the sliders too then?

😯

😛

the stiffness increase is c30%. you will notice the difference more if you have a stiff fork, wheel, axle as well.

The front of my folks’ tandem is scary. It’s a very obscure variation of 1″ with integrated races to take larger bearings yet keeping the 1″ steerer. Under braking there’s enough flex in the steerer to make it feel like the headset is chronically loose. Stationary there is no play at all in the headset. I don’t like riding it.

A proper engineer will tell you its stiffer – but you wont notice it. Its a tiny difference that you can measure / calculate, but you’d never feel it
Marketing sells stuff.

Back in 2005-06 I had some manitou minutes, which at the time were light but would now be about average for a 130mm fork. New taper forks are definitely stiffer for the same weight!

The steerer flexed so far it wore against the top edge of the head tube cups!

And look at older non-tapered Pikes of a similar vintage, the steerer is practically a solid where it mounts in the crown, and they weren’t light as a result!

Marketing sells stuff

Yep, but it’s nowhere near as effective as bullying purchasers into buying ‘upgrades’ by making their existing kit obsolete due to unavailabilty or compatibility issues.

It’s not the marketing that winds me up, marketing bullshit is easily debunked. It is enforced obsolescence that is the naughty bit.

The difference in fore/aft flex between tapered and non-tapered forks is very noticeable.

I have 2 sets of 150mm Revelations – a straight 1 1/8″ set on my Bfe, a tapered set on my Rocket. Both bolt through axles. The set on the Bfe is WAY twangier – I can actually see the fork bending backwards under hard braking (and that’s with 10stone me on board), especially on steep ground when all my weight is on the fork.

I also prefer tapered forks to 1.5″ as you can then run an internal top headset cup in a straight 1.5″ or 44mm headtube and keep your bar height vaguely sensible. Especially applicable to those of you running clown wheels as your fork will be longer due to the big wheels.

You can buy an old Cannondale and still fit today’s latest forks, ahead of their time those blokes.

Which one is most likely to fall over in a storm? The Pyramids or the PO tower?

How would you know if a pyramids hadn’t already fallen over? Which way up were they to start with?

I’d completely agree that the stiffness thing is maybe not something everyone will actually notice.

Very simplified, it is more to do with lightweight long forks = bigger bending moment so more stiffness = less deflection = less strain (strain is basically a measurement of localised deflection) = less stress = less fatigue = less snappy steerer = less hospital.

But it all has to be balanced – durable structures have nice gradual stress gradients and the last thing you want is something that suddenly changes in stiffness (or it just breaks at that point).

Stanchions aren’t tapered (forgetting the slider functioning bit) because there are two of them working together (so straight away double stiffness) and already well over 30mm diameter.

The other big problem is the range of riders and usage – I’m a 64kg so could probably ride a 150mm 1 1/8″ fork and never break it. Some riders are twice my weight and huck off jumps with varying levels of finesse…….

Turnerguy – you aren’t comparing the same thing. You need to compare 2 x Magura or 2x RS forks with different steerers (everything else being equal).

Look straight down over your bars and grab a handful of front brake, you can then see how much your forks flex… or get a face full of dirt.

On a more serious note… with slacker head angles and longer travel single crown forks being in high demand, any opportunity to stiffen the forks without too much of a weight gain needs to be taken.

I’m convinced tapered forks and the large head tubes which accommodate them are an improvement.

http://chrisking.com/files/pdfs/Int20HeadsetsExplained.pdf

On a XC bike yeah, on a 30lb trail bike the weight penalty wouldn’t make a blind bit of difference, would be happy to incurr weight penalty for wider choice of headset.

Most 30lb trail bikes weight 32-35lb anyway…
If you want to make a frame to a weight you have to do it incrementally over the entire frame, make the savings where they can be made and work from there.

It allows angle adjuster headsets let’s not forget

Edit: sorry that wasn’t an answer to the question

I have 2 sets of 150mm Revelations – a straight 1 1/8″ set on my Bfe, a tapered set on my Rocket. Both bolt through axles. The set on the Bfe is WAY twangier – I can actually see the fork bending backwards under hard braking (and that’s with 10stone me on board), especially on steep ground when all my weight is on the fork.

I have a few bikes with setups similar to that and each time I ride the bike with straight through inch and an eighth (20mm bolt thru), it feels a trickier bike up front to ride and control than the bikes with the tapered fox and pike (both 15mm bolt thru)

It’s not really fore and aft stiffness I’m noticing as something I’m benefitting from, it’s the ease of steering it where you want to go. whether it be locked into mud or fighting rocks/roots. The damper in the old pike along with the 20mm axle would make you think that it might balance things out but it doesn’t stop there. It’s the torsional stiffness of not only the steerer and fix point in the crown, also (and I’m wondering if it’s more so) the stiffness of the size of the top and down tubes as they flare out and meet up with the headtube. I think it’s the torsional control you have up front of the tapered headtubed frames that is as much the part of the overall package. Long live tapered headtubes. I just wish we could fit them to some of the lovely old frames we have kicking about!

“What’s the reason for tapered, and not just straight 1.5?”
The use of 1 1/8″ stems. Not just for availability, but you can go shorter, or rather you don’t have to go longer. IIRC you can only go down to a 50mm stem with a 1.5″ steerer. Maybe you could get down to a 45mm, but its no 35mm that you can get down to on a 1 1/8″ steerer

I suspect the added weight of a full 1.5″ steerer, headset, headset spacers and 1.5″ stem put together over a tapered setup (including frame) would be a bit more than you’d think

1.5 isn’t dead – at least not on my bike. Its the obvious choice that was ditched for God-knows-what reason.

Not only id the steerer tube stiffer than tapered its lighter too. The wall thickness of a 1.5 is much thinner than the thickness of the 1,1/8 portion of a tapered tube. Not only that but the steerer stem interface is much better on a 1.5 as there is a bigger contact area. Also 1,1/8 stems look silly small and naff on a tapered head tube IMO.

OK so you may increase weight ever so slightly in the headtube and upper headset of a 1.5 but since the steerer is lighter to start with it really is in the noise. Also its much cheaper to manufacture a straight headtube over a tapered so the cost savings could go into making the frame even lighter!

Its just fashion and I eagerly await the return of 1.5 so I can upgrade my forks 🙂