[Closed] MTB frames and their maximum fork length versus the fork length you actually run

it'll be fine

(running 180mm domains on a dialled alpine)

120mm in 100mm Lynskey for a few months and it rode a lot better for it.

160mm on a hardtail frame is probably a bit pointless. unless you're bottoming out the 140mm you'll not see much benefit. running longer forks will also straign the head tube welding a bit more than intended - how you ride will determine if this is trouble or not.

It can break your frame

The original Giant Trance was a lot better on a 130mm fork than the 100mm supplied/recomended.

If your frame's still in warranty, I'd think twice but other than that I'd crack ( 😉 ) on.

If your frame's still in warranty, I'd think twice but other than that I'd [b]crack[/b] ( ) on.

It's a Commencal, so I may be tempting fate!

I ride an Alpine with Lyriks, but very rarely use them at full travel. If you have u-turns there is no reason why you can't run them at 140mm or 150mm. Unless you are pointing downhill the handling gets worse the longer your forks get.

can't really see the point in running 160mm in a hardtail frame TBH.... if it's rated to 150, I imagine it'll be ok with 160, but there will obviously be a warranty issue and you'll slacken the front up quite a bit.

If you put Lyrik u-turns in it, you can always dial them down to 145 or something, but then you may as well stick with the pikes for that.

Assuming your Pikes are 20mm axle, can't remember if they all are or not, I don't think there's much point in changing unless you're pushing the limits of your pikes and botteming them a lot (a number of times during each ride) as said above.

cynic-al - Member

It can break your frame

Will it tho? its such a small % increase in the leverage and there must be a safety margin. So unless you are hooning off huge jumps and weigh as much as wales then I don't buy this argument.

The frame is safe for a 100 mm fork - thats A-C of what - 450 mm (ish)

Go to a 130 mm fork thats 480mm A-c - an increase of 7% in length so 7% greater leverage. Thats not a lot. 7% greater forces.

stooo - Member

if it's rated to 150, I imagine it'll be ok with 160, but there will obviously be a warranty issue and you'll slacken the front up quite a bit.

I run a bike designed for 80 mm forks with a set of u turn pikes at 95 - 140

At 95 it rides just fine. at 110 the weight shift backwards is starting to effect things - it doesn't climb well but the steering is still ok. At 140 mm it is only any good for steep downhills and is totally wheelietastic and a bit sluggish steering

I suspect it was a steep angled sharp steering frame originally.

Would love to hear mike@dialled, brant or cy's view on this

I replaced 435mm a-c rigid forks with 545mm a-c 150mm travel suspension forks.

[url= http://sphotos.ak.fbcdn.net/hphotos-ak-snc3/hs322.snc3/28736_432218652149_544582149_5704431_2398962_n.jp g" target="_blank">http://sphotos.ak.fbcdn.net/hphotos-ak-snc3/hs322.snc3/28736_432218652149_544582149_5704431_2398962_n.jp g"/> [/img][/url]

noticeably higher at the front but by god it makes the bike a much better ride 😉 I am running about 50% sag though 😛

I expect manuals are easier now nbt...

TJ - I said it "can" break your frame - soulrider did exactly this.

As to whether it will, that depends on numerous factors in the OP's riding that you and I know nothing about. It's clearly not just about fork length % increase. The fork will likely be most compressed at maximum stress. Folk will tend to ride more hardcore on a longer fork and it is likely to be stiffer, transferring more force to the frame.

As TJ aludes to its all about the A-C lenght. Take my bike, i am running the 2010 Revelations on my P7 which at 150mm are supposed to be too long for my frame (max 140mm) but the A-C length on the 2010 revs is the same as the 140mm 2009 model...

Don't buy the stiffness of the fork having any significant impact, most modern trail forks are a lot less flexy than the used to be and even more so with bolt thru axles. I reckon she`ll be right 🙂 , with the appropriate amount of sag the real length of fork will be less anyhow.

Folk will tend to ride more hardcore on a longer fork

I'm guessing thats the critical factor - not the increased fork length putting more stress on the frame but the harder riding that becomes possible.

I put the pike on mine as an experiment and was fascinated by the apparent results - in that the slackening off of the head angle made little difference that I could feel in terms of the steering ( perhaps because of the decreased trail??? or steep angle to start with) But the alteration in the centre of gravity was very noticeable. The weight going backwards and higher alters the feel remarkabley.

If you think bolt-through axles are relevant, you haven't thought this through have you?

160 lyriks on an old (03ish) rocky ridge frame, have done for a while. Given the franky pisspoor way I ride I'm most concerned about the chainstays.

Not so much relevant, just in relation to stiffness. All modern forks are stiff as hell unless you go for XC specific. I was saying that i'm not so sure the forks stiffness (i asume u meant lateral stiffness) is a significant factor in the forces on the frame. Certainly not in relation to the leverage of the fork itself as the majority of impact will be inline with the frame from the wheel hitting obstructions in the trail, thats why gussetng sits on the down tub surely.

Go to a 130 mm fork thats 480mm A-c - an increase of 7% in length so 7% greater leverage. Thats not a lot. 7% greater forces.

Yes, but if we're talking fatigue damage is it necessarily a linear relationship?

I was saying that i'm not so sure the forks stiffness (i asume u meant lateral stiffness) is a significant factor in the forces on the frame.

I mean back and forth stiffness. A lyric is going to deflect way less than a 32mm fork for instance. Lateral stifnfness is irrelevant.

130mm menja's on a 456 so still 20mm off the 'maximum'.

I tried 150mm once on a hardtial, the problem is as TJ said, the bigger forks push weight back, and make it harder to put weight on the fork and off the unsuspended rear wheel. With 130mm-140mm forks I can get the bars low enough to keep weight on the front wheel, any more and I start to wish for some rear suspension.

Ever since the favourite buzzword in magazines became "slack" there seem to be a lot of people who are convinced that bike designers don't know what they're talking about. I once put 100mm forks (with no preload to maximise sag) on my old Kona - after the honeymoon period I was forced to admit that it wasn't better, and in fact was quite annoying, because you had to get all over the front of the bike to get it to turn.

I prefer a neutral handling bike that you can drive from the middle, pretty much like the designer had in mind in the first place.

I'm running a '03 100mm Superlight with 130m Revs. It has made going down much more fun but climbing is more difficult. No cracks yet.

Longer forks push seat angle back, as well as head angle backwards, so you're sat further over the back wheel, which makes the bike wheelie more on climbs.

It also lifts the BB, which in most cases, isn't really what you want to happen to maintain nice handling, and also means the bike is more wheelie prone.

Frames designed for long forks (hopefully) have things in the right place when those long forks are fitted.

I can see how shorter riders can struggle with the height of the front of a long travel hardtail, but there's not a lot anyone can do about that. Suggesting perhaps a shorter fork, and slacker head angle is one, but... For a small rider wanting a great ride, the On-One Summer Season with an 100mm fork is still a standout buy.

To answer the OP, it'll probably be fine. I agree with Cynic-al's sentiments about

Folk will tend to ride more hardcore on a longer fork and it is likely to be stiffer, transferring more force to the frame

Yay! I wuz right!

Anyway, a 10mm longer fork (for the same A-C) isn't actually 10mm longer, as you'll have 30% of that as sag, so it's more like 7mm longer. If that makes a difference I'll be surprised.

cynic-al - Member
Yay! I wuz right!

lol, nothing like only reading what you want to read al! 😀

How so tree?

if a fork has the same a-c but has 10mm more travel won't it actually be 3mm shorter than the other fork with 30% sag dialed in?

not sure it matters, as I rarely slam the front end of a bike into things when sitting at sag, normally fully extended or fully compressed when i crash 😀

i ride 140 pikes on an Intense meant for 100 mm forks not died yet. Wind them down for all but downhill and they have a lot of sag as well so possibly only 20mm longer than 100mm not dies yet.

Al

To answer the OP, it'll probably be fine. I agree with Cynic-al's sentiments about

[i]Folk will tend to ride more hardcore on a longer fork and it is likely to be stiffer, transferring more force to the frame[/i]
,[b] but the change from a tough 150mm fork to a tough 160mm one isn't too reat.[/b]

Aye well the design guru/hero quoted me, so I am taking it as my victory

Anyways soulrider recently broke his soul running wound down lyrics so there has to be [i]something [/i]to it.

Anyway, a 10mm longer fork (for the same A-C) isn't actually 10mm longer, as you'll have 30% of that as sag, so it's more like 7mm longer. If that makes a difference I'll be surprised.

Good point.

However, one to watch is that manufacturer tolerances on forks are quite wide- Fox for instance spec +/-5mm for length on their forks! I only found out as I mentioned to Cy that rear shocks have +/- 2mm on their length (which is quite a lot at a 3.25/1 ratio!

ps - cynic-al - I can now use this quote about myself 🙂

design guru/hero

[b]Bottom line: If the longer fork rips the headstock off, would you be happy just buying another frame? 'cos you'll be out of pocket.[/b]

Yes: do it!

No: relax, don't do it.

Its that bottom line that's stopped me putting pikes on my tandem and 160mm forks on my 5-spot.

160mm Lyriks on a Dialled Alpine

140mm Pikes on a Meta 4.2

180mm 66s on a Spesh Pitch

No snapped headtubes so far

Anyways soulrider recently broke his soul running wound down lyrics so there has to be something to it

ADH - having used the term "headstock" I can no longer take you seriously in technical matters. See also "cross-bar"

brant - Member
ps - cynic-al - I can now use this quote about myself

If you credit me (as internet fan-boy), I will allow it.

Setting aside the frame breaking, surely the best reason to not bother is that it is unlikely to be better? If the designers worked out all the angles, built and tested prototypes and in all likelihood based the design on tried and tested previous years' models, how likely is it that they got all of that wrong?

Personal preference may mean someone prefers a different set up to the designer's.

As for statistics - I've not heard of any soul breaking there (if at all), and all I ever said was that it was possible.

i was joking - you did see the wink didnt you? I would be certain it makes it marginally more likely as you are outside "normal " tolerances but the increase/difference is marginal and the small increase in risk is acceotable IMHO.

Braking frames is probably more due to rider style/terrain than fork length per se. A mincer will never break a frame where as a balls our rad to the sic jumping god will be far more likely even if they are smooth

ADH - having used the term "headstock" I can no longer take you seriously in technical matters. See also "cross-bar"

Oh lordy, there really is no hope for me now. I must end it all forthwith 😐

Would it be the head[b]tube[/b] that cracked/split/snapped in half though? Or would a weld pop, or would a [b]top[/b]tube and/or downtube split? Bend? Deform? Ripple? or would a headtube reinforcing ring ovalise, or pop?

Ergo: headstock.

:finger:

Quite soon there will be an anti-slack backlash. People will start saying how good it is to have a bike that flicks into turns without having to be hauled and manhandled.

If you think your riding style favours a slacker beefier bike then buy a slacker beefier bike, is my recommendation. That way the seat angle, bottom bracket, front centre and frame strength are optimised for that kind of work. If you slap a big fork on an all-round xc/trail bike you are just piling compromise on top of compromise and are not likely to get the same well researched blend that the manufacturer offers off the shelf.

when fork brands vary by about +/- 10mm in stated axle-to-crown measurements for the same travel, i don't see why you should limit a bike to a travel setting. max static fork length makes more sense. a bike can run fractionally lower with a 140mm fox than with a 130mm rockshox if sag % were the same, so longer doesn't always mean higher / worse handling.

ADHD no idea WTF you are on about but stay off the coffees I was only kidding.

So was I really 🙄

[img] [/img]

I suppose my point was that fitting longer forks wouldn't necessarily just bugger the headtube, it could be anything that end of the frame that fails.

glenp - my frame was a steep angled old skool but nice frame - the longer forks make it a bit slacker and give more travel - and unless I wind it out to ridiculous lengths dont damage the handling that I can tell.

Whats not to like? Can you get 80m good modern forks? or as it rides fine with 110 on it is that not acceptable?

Not really talking about keeping an old frame going, TJ. And anything is acceptable with your own money I suppose. I'm just railing against this whole slacker must be better thing, which is ill thought out (in my opinion).

Some people are putting good money into brand new forks which chopper-out their previously sweet handling bikes. And since several hundred pounds of hard-earned have gone into it perhaps they are reluctant to admit that they might not have done the best thing. Trail bikes these days are already well designed for all-round fun riding and more travel is not necessarily better.

I did it partly as an experiment - hence the u turn fork - I was surprised by the results in that the slacker head angle made little obvious difference but he alteration in weight distribution did make a huge difference.

When I have some spare pennies I'll probably put a100 / 110 mm fork on it as a decent compromise

Some people are putting good money into brand new forks which chopper-out their previously sweet handling bikes. And since several hundred pounds of hard-earned have gone into it perhaps they are reluctant to admit that they might not have done the best thing

Yep, I agree. Loads of people are stuck in self-delusion ATM.

I have a slack-ish bike which is fun for some stuff, and a very unslack bike which is fun in other ways.

The delusion is that one or other is intrinsically 'better'.

The point though, is that if you took some of the slack one and put it on the steep one that it would not make it better - or certainly it is unlikely to.

I agree completely; I fondly remember making this mistake with a kona explosif and some triple clamps. No lasting damage ensued, but said explosif currently sports the shortest rigid forks I can find and has done for the past 10 years.

However, many people are riding bikes thinking 'if this bike was a tinsy bit slacker, it's be better in scenario x, and worse in scenario y, yet I don't really care much about scenario y'.

...sticking with the Pikes.

150 Rev u-turns on my 120 Mount vision. Absolutly love it! I'm just short of 15st and 6ft, so the extra inch of travel is very welcomed, allowing me to run slightly more sag and less pressure without my lardy arse bottoming the forks out, improving both the tracking and the handeling.

perhaps climbing ability of a longer fork effects short light riders more than tall heavy ones? It sure as hell makes little difference on my bike for me 8)

I've kind of gone the other way. Gone from 130mm Phaons on my Soul to 100mm Rebas. Might be shorter fork, newer fork, stiffer fork or any combination of the above but Soul feels better for the type of riding I do on the Reba

I have 160 vans on my evil soveriegn,2010 and I have 140 vanillas on my '07 cotic soul,

the soul was supposed to be 120max and the sov is 140 max,

i spoke to evil before i brought the frame, they know plenty of peeps that run 160's, i love this bike like this, it doesn't climb as steadily as the soul, but ar5e forward on the saddle, elbows under bars,keeping the pedal load even and it will climb everything my soul climbs 😛

at connock's monkey it was a doodle to ride up all those switchback climbs and i was passing plenty of other riders who didnt have huge pogo sticks up front.

the frame seems quite happy as well, in fact it's incredibly sure footed and confidence inspiring and i don't worry about the headtube snaping and poking my eyes out 😛

[i]Quite soon there will be an anti-slack backlash. People will start saying how good it is to have a bike that flicks into turns without having to be hauled and manhandled.[/i]

my chameleon with 140mm forks is nicely flicky. Properly designed bikes is the answer not recidivism

perhaps climbing ability of a longer fork effects short light riders more than tall heavy ones

sure does My Ventana now runs a new set of Rev 150mm teams (u turns) and the extra 10mm of travel appears to have buggered up it's ability to climb. (they only drop to 120mm now as opposed to the Pikes dropping to 110)

Yesterday in Grizedale on some of the rocky steep climbs the front end would lift at the slightest hint of a step up, it did this slightly with the Pikes on before hand, but it felt awful and noticeably worse yesterday.

BTW i'm only 11 stone and 5ft 4" so I can tell you it does affect short light folk.

Now to go away and figure out what to do about it ❓

sure does My Ventana now runs a new set of Rev 150mm teams (u turns) and the extra 10mm of travel appears to have buggered up it's ability to climb.

I think manufacturers don't just say "Xmm only" coz of the A-C length and leverage but also due to how hard it's gonna get smashed into stuff.

A long time ago I put my 100mm bombers on a frame designed for 63mm forks, which is a lot more diference than 140-160. I [i]was[/i] going to say the frame lasted for years but then I remembered, the replacement frame (80mm design with gusseted front end) lasted for years, the original cracked on the top tube just behind the headtube.
Oops

and yes the handling on the flat was a bit pants and flipfloppy in corners but it was pretty good downhill and on steep (down) stuff.

edit "Now to go away and figure out what to do about it" you can swap them for my 125 revs 🙂

Yes the A-C is 10mm different, but I think the original Pike was getting close to the frame limit so the extra 10mm and the 3/4lbs less in weight seem to have made a noticeable difference in it's climbing on Rocky steeped steep stuff.

A forward seat move and drop the stem may go some way to getting the bike back to how it was.