[Closed] Why not linkage forks?

Pushbikerider - not necessarily - using double wishbone you can tailor the fork to have any path you want. My BMW had 7" of travel.

[i]Plus you have the fun of dealing with lots of little bearing[/i]

But you have that at the back of full sussers anyway and everyone seems to get on with it quite happily.

IMO the conservatism of the consumer and probably most importantly thay cannot go on conventional frames ( apart from leading link which misses someof the advantages)

i would love to see something like a hossack system on a mtb. a friend of mine raced a hossack supermono and he claimed it provided huge confidence in the front end, especially on the brakes. i am imagining a 6" travel bike with a ccdb

Fashion to some extent.

Plus there is a greater body of knowledge on how to make a telescopic fork work nicely.

There's nothing wrong with the idea of a linkage fork, but many of the early linkage forks were poorly made with inadequate bearings (but so were the telescopics). However the suspension unit can be replaced with something more modern to improve them.

For the modern market the amount of travel would need to be greater so the linkage designs would have to be beefed up. Although you don't need as much travel on a linkage fork if you have it set to anti-dive, you still have to satisfy the market about having so many inches of travel.

Don't know if [url= http://www.parafork.com/ ]Parafork[/url] are still going, but their fork looks ok.

[img] [/img]

I've got a set of the amp ones- they are steel, light as, and work pretty well for xc.

If they worked better than telscopic forks, they'd be used in racing.

There is the agument that when motorcycle production was big, just after the war, when they had alot of machines for producing tubing (gun barrels) the most effective and cheapest way to produce the forks was make telescopic ones using the skills and machinery from the war effort, development went down this path and has stayed like that.

I don't necessarily agree with either of these statements mind you 😉

teej has it I reckon, too hard to get a foothold in the market place, and forks work pretty good..

I had a pair of AMP forks on a Merlin ti XLM they were not to good I remember reading the instuctions and thinking this is so wrong " if you get a squeaking sound from the bushes just spray your bidon over them'' !!!!! 😯 Thats after nearly 20 years and I still can't get that out of my head. I sold them on soon after getting them.

everyone who ive ever heard about the PRST-1 from said the fork dived deeper and faster than..... (insert poor taste joke here) and was therefore a complete nightmare to stop yourself going over the bars.

they do look good on some bikes;

[img] [/img]

just mainly not bicycles.

http://www.hossack-design.co.uk/

worth a read

The forks epicyclo posted above are compromised to allow them to fit on conventional frames - the BMW / Hossack system the wishbones and shock do not turn with the steering

[img] [/img]

Where do USE SUB forks com in? Kind of halfway between a leading link and telelever setup.

I always thought the problem was no one knows what the 'ideal' front axle path would be, do you go back then up to absorb impacts (which telescopic forks do quite well) but gives you sharper steering as the suspension compresses, or do you go verticaly upwards, giving a nice constant wheelbase as the axle path matches the rear better, but doesnt absorb impacts so well?

What I dont get is why fork stanchions are always parralel tot he steerer tube, surely they're missing a trick to slow the steering down a bit by making them more vertical so for the same static rake/trail figures the steering would slow down as the suspension compresses.

It is much easier to come up with a bad design for a linkage fork. 🙂

I would prefer something like the Vincent Girdraulic to a tele.

TJ - you're right; you can get a much better axle path with a frame designed around the forks and longer links, I was thinking more about the self contained design needed to retro-fit to a conventional frame.

That Para fork does look rather good mind, unfortunately I was involved with making these instead 🙂

[img] [/img]

thisisnotaspoon - Member
...What I dont get is why fork stanchions are always parralel tot he steerer tube, surely they're missing a trick to slow the steering down a bit by making them more vertical so for the same static rake/trail...

The more vertical the fork tube is the more likely it is to stick. There's a sweet spot of headangle for teles - too much slack and they bind, too little and they bind. Fortunately the sweet spot has a reasonable range. Also with larger diameter tubes being used now, it is less of a problem. The shorter the fork the lesser the problem.

Suntour FTW!

[img] http://www.srsuntour-cycling.com/gateTools/scripts/binary.php?BinaryCodeID=1723&convert [-resize]=400x600[/img]

there must be, oh, several whole milimetres of travel on those suntours.

I think the telelever single wishbone type have potential for mountain bikes. Simple system, not too many bearings needed, direct mount handlebars, natural antidive while allowing bump absorption so yo can have soft springing without it plunging under breaking

[img] [/img]

I my mate had some Girvin Vectors when I had RS Mag 20s and his were far more reliable than mine. I'd still love a set of linkage forks but then I'd also love a belt drive IHG full suss as I'm odd like that.

One of the issues with linkage forks has nothing to do with the suspension, they'll only fit a certain maximum headtube length so they end up being made long to accommodate all sizes and can as such look a bit odd

The limiting factor on the Whyte (and you can see it on mine (apologies for posting the picture on a 2nd thread) is that the top linkage swings up towards the handle bars; limiting the maximum travel available by the height of the front end. It feels a little high with the travel available as it is; if you were to up it to 140 or more than it would get ridiculous.

[img] [/img]

I know Ade Ward (who was involved in the design and sometimes pops up on here) uses a 24" front wheel to help drop the front end down; though this steepens the head angle slightly. I've just swapped to some fleegles to help lower the bars without compromising the head angle change - it's a little steep by todays standards 😀

Oh; and fwiw @titusrider - I've never had an issue with that problem; but then I've only had air cans on the front of my PRST1 / 4's - It may well be a spring thing.

My thoughts are that the weight and complexity to benefit ratio isn't quite there for push-bikes, and might not be there for motos either.

It's often a more effective solution to put your time and effort into making an already relatively mature technology fit the application better (linear push-rod dampers in telescopic forks), rather than scrapping the whole system and generating entirely new sets of problems (stiffness, damping characteristics, unsprung weight etc) for a possibly marginal gain (better wheel path).

In a way, this is analogous to the single pivot vs multi-link question: by putting design effort into damper technology, stiffness and weight, single pivot bikes remain competitive despite their 'obvious' flaws. Linkage forks are the same but more-so IMO.

I also had Girvin Vector forks many years ago on a Proflex.By far the worst forks i've ever had.I swapped them for some RS Judys and even they were massively better.

http://singletrackworld.com/forum/topic/what-was-wrong-with-leading-link-forks-whyte-use-sub-girvins

the whyte is also compromised by the short top wishbone and the top wishbone being used for steering - compare to the BMW double wishbone system which has a separate steering linkage. the shock would also effectivly have a falling rate leverage ration from the angle its mounted at - presumably for a reason tho

I got into the whole 'telescopic forks are a compromise' story back in the 80's when I had a Feet Forward M/C, like these:

http://www.bikeweb.com/node/458

And I've ridden most of the old crop of various methods, but tbh none of them were as good as the mass-produced forks available on bikes at the time. I don't doubt that with some decent engineering they could be (as good?), but even those tried didn't sell particularly well (BMW excepted):

http://en.wikipedia.org/wiki/Yamaha_GTS1000

And tele-forks just work 🙂

I thought the reason behind the falling rate leverage was to compensate for the natural increase in spring rate as an air shock runs through it's travel (the overall effect being essentially linear) - not sure how close this comes to levelling out or how much this makes fitting a coil to the front (as some of the cheaper whytes) a really bad idea ...

I was following all that as well BR altho I never rode one.

the BMW telelever works really well. When you brake it dives an inch and no more to give the feel - but the fork still absorbs bumps when braking. as a result you can have a really soft spring rate for comfort without getting dive or wallowing. especially good two up. It also does not tuck or run wide when braking and turning.

I think the antidive / soft spring would work realy well on MTBs

[url= http://www.tonyfoale.com/Articles/Steer/STEER.htm ]Why not..... [/url]

i had a pair of girvin vectors - i think they were ok.

but...

they 'only' had 75mm of travel,

the damper was a bit shonky.

they looked weird.

If USE put a better bearing on the SUB it would be a world beater

I'm a bit of a linkage fork perv....

In the collection I've got:

GT Xizang with Quasar No 1's (and some of those other "shockingly bad components - Spinergy Rev X Roks !!! Oh the Horror! ) fitted to it and I LOVE them... I used to ride them everyday through my school, college & Uni years. They (the wheels and forks) had a reputation for snapping, but I've never had a problem and they've had some pretty hard hits over the years.

Excuse the Pic its a dodgy edit, and a few years old too.

[IMG] [/IMG]

I've got a PRST1 WORKS XT - LOVE IT... and ride it wherever I can.

...and a Kenisis Ultra Light fitted with some Carbon Look Fournales... check them bad boys out!

The latest steed has fox Talas 32's and somehow there not as responsive as the Whyte.

titusrider - Member
everyone who ive ever heard about the PRST-1 from said the fork dived deeper and faster than..... (insert poor taste joke here) and was therefore a complete nightmare to stop yourself going over the bars.

POSTED 4 HOURS AGO # REPORT-POST

I have written several replies to this and each time I change it,I still can't find the words for people this oh yes troll is the best term

I was going to write a considered factual reply to the reasons why we designed the Preston forks and my experience in motorbike and mountain bike suspension development my 10 patents in suspension systems but I really can't be arsed when people like this write drivel on here

Spinergy Rev X Roks

I have a photo somewhere of me gurning through the remnants of a rear wheel. TBH it is the only spinergy composite collapse incident I know of.

Ade - forgive my ignorance... did you design the PRST forks?

why we designed the Preston forks

If ya did, TOP MAN they steer and track over small & large bumps like no bike fork I've ever ridden, and I love them, they do dive a bit under braking, but not much and hey what fork doesn't !!

Nick3216 - Yeah I had heard all the horror stories, but can't find anyone that's ACTUALLY OWNED AND RIDDEN THEM HARD that's managed to destroy one! Get that photo up it'd give us a laugh!

I rode a PRSTN in the lakes for a day and offroad it was fab, but smooth stuff made it feel like a barge.

I had an Amp and it was a great bike, and good fork for xc . At the time the travel was compatible to telescopic forks of the time.

Betamax was better than VHS. It's not just if something is a better design. The whole world has to accept it. They didn't, end of.