# What Does Slack Mean?



## asulli (Apr 10, 2008)

I searched this but couldn't find anything. What does it mean when people say a bike is very Slack or has a Slack head angle?


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## pdh (Jan 20, 2004)

If a bike's head angle is too slack it is slow to steer and hard to turn.
If it's too steep it can be too twitchy when up to speed.


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## Madman133 (Apr 25, 2006)




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## asulli (Apr 10, 2008)

If it is to slow to turn then why do people review bikes and say "They are nice and slack"?


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## SHIVER ME TIMBERS (Jan 12, 2004)

Madman133 said:


>


ha ha...where did you get that pic of me??


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## SHIVER ME TIMBERS (Jan 12, 2004)

asulli said:


> If it is to slow to turn then why do people review bikes and say "They are nice and slack"?


that's the trick

you want the fork slack so you can ride over rock gardens easier without going over the bars or riding down steep stuff....but not so slack that it slow when turning


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## asulli (Apr 10, 2008)

So it all about finding that happy medium in a head angle? If the head angle is too steep then it will feel good on the steeps but not be stable a high speed?


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## darkest_fugue (Sep 25, 2007)

NOOO, let me try and put it another way, think of slack as the the front wheel being further out in front of you when you ride, this means going downhill its more stable in front because that wheel is out in front of you more and can save you going over the bars etc, a steep head angle means the front tyre is more under you than out in front of you so its not as controlable down steep terrain and theres more chance of you going over the bars, downhill bikes and freeride bikes have slack head angles and xc bikes have steeper head angles, thats as simple as i can put it


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## huntandride (Sep 29, 2007)

if it helps i'd aim for somewhere around 65deg.


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## Jekyll_Jockey (Aug 31, 2004)

asulli said:


> So it all about finding that happy medium in a head angle? If the head angle is too steep then it will feel good on the steeps but not be stable a high speed?


The slacker the bike (its going to have a smaller HT angle) the more stable, at high speed, through the steeps and the rocks, but it will feel "slugglish" or "turn slow" at lower speeds.


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## NoManerz (Feb 10, 2006)

Slack bikes get a little bit tricky to maneuver at slow speeds. Most all dh bikes will be slacker than fr bikes. Fr bikes tend to be a little bit steeper to aid in slow speed north shore style stunts.

I climb my slack 64 degree head angle up hill and it wanders all over the place and can be tricky sometimes.


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## asulli (Apr 10, 2008)

Thanks I think im getting it.


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## pinknugget (Jan 21, 2007)

You were right when you said it is a balance. As has been mentioned a steeper head angle will make for a better turning bike, slacker will give you more control in the steep and nasty. Finding the head angle that is right for your style of riding is a matter of balancing the two.


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## Berkley (May 21, 2007)

Choppers, like the green one pictured have a very slack head angle. If you've ever ridden one, you know they are difficult to steer. A steeper angle is easier to steer. In the attached image, the head angle is illustrated as "A." (This is the geometry for a Trek Fuel EX by the way, and it is 69 degrees)


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## dft (Apr 9, 2004)

once you go slack, you don't go back!!
even all mountian bikes are tending to become more slack, its just more fun. XC geometry blows unless you race XC or something. there are some good 6 inch bikes with 66 degree HA, nice! (especially with adjustable forks, you can mash down for the climbs fi you want)


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## C.M.S (Aug 28, 2009)

Hate to resurrect a dead thread but is there a huge difference in going 1 degree either way ? My frame is set up slacked and I could flip the shock link ( FSR frame) and go 1 degree steep and also raise the BB 5mm . Worth doing ??


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## cookieMonster (Feb 23, 2004)

Another aspect that hasn't really been mentioned is that slack head angles (62-65 degrees) require very little input on the handlebars to steer at high speeds. You steer more simply by leaning. They can be a handful at slow speeds, however, and definitely not ideal for climbing.

Conversely, steeper head angles (67+ degrees) are better for climbing technical ascents because they track more precisely and you're not fighting to keep your front tire on the ground. Slacker head angles tend to wander all over the trail when climbing, since at slow speeds a slight input or lean will send the bike off your line very easily.

My current bike has about a 65 degree head angle, and I compensate while climbing by moving my seat all the way forward on the seatpost and making sure it's level. That way my center of gravity is more forward which helps keep the front tire tracking where I want it to go. The tradeoff is worth it to me, because at 65* it's amazing on the DH sections.

**Edit -- woops, didn't see that this was an old thread. C.M.S. - -there is a noticeable difference in 1 degree. Flipping your bike to the steeper setting would probably help on climbs, but reduce downhill performance. By going steeper, you'll feel a little more "on top" of your bike than "in the cockpit" so to speak. It won't be a huge difference, but it will be there. If you changed it by 2 degrees it would be a huge difference.


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## C.M.S (Aug 28, 2009)

cookieMonster said:


> Another aspect that hasn't really been mentioned is that slack head angles (62-65 degrees) require very little input on the handlebars to steer at high speeds. You steer more simply by leaning. They can be a handful at slow speeds, however, and definitely not ideal for climbing.
> 
> Conversely, steeper head angles (67+ degrees) are better for climbing technical ascents because they track more precisely and you're not fighting to keep your front tire on the ground. Slacker head angles tend to wander all over the trail when climbing, since at slow speeds a slight input or lean will send the bike off your line very easily.
> 
> ...


Sounds good 
My frame may have odd specs though compared to new .

70.5 (steep) H.A
69.5 (slack) H.A


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## cookieMonster (Feb 23, 2004)

Oh my. By all means, put it in 69.5 mode and throw away the allen wrench you used to do so.

69.5 is still what I would call "steep," but at least it will handle a little better on the downhill than before. It will still be just fine on the climbs. As I said, I climb with a 65 degree head angle -- it's not ideal, but it gets the job done.


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## C.M.S (Aug 28, 2009)

cookieMonster said:


> Oh my. By all means, put it in 69.5 mode and throw away the allen wrench you used to do so.
> 
> 69.5 is still what I would call "steep," but at least it will handle a little better on the downhill than before. It will still be just fine on the climbs. As I said, I climb with a 65 degree head angle -- it's not ideal, but it gets the job done.


That's how it was ( 4 yrs and still is ) , didn't know if going 70.5 would be overall better .
But the 69.5 slack spec is for factory 120mm susp fork , I have a 140mm !( so I guess the angle is slacker than the 69.5)(although with U-Turn adjust ) so I can mash it all the way down to 110


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## boardjnky4 (Nov 20, 2014)

20mm of travel is roughly equivalent to -1 degree on the HTA. So you're probably closer to 68.5. That setup makes for a pretty good "all mountain" bike.


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## ustemuf (Oct 12, 2009)

What's slack? My new bike....62.5 degree HA stock  That's whats slack! Now I just need the frame to get in my hands so I can test said slackess on the mountain!! ahhhhhhhhhhhhhh


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## mykel (Jul 31, 2006)

63.5 on the Podium, what are you on for 62.5?


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## ustemuf (Oct 12, 2009)

mykel said:


> 63.5 on the Podium, what are you on for 62.5?


the new pivot phoenix stock at 62.5 ha.. i think the 650b wheels lets them get away with it.


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## NWS (Jun 30, 2010)

66 = almost slack
65 = barely slack
64 = kinda slack
63 = slack
62 = pretty slack
61 = very slack
chopper = ridiculously slack

(I totally made that up. But I think it's about right.)

A lower (slacker) head tube angle makes the steering less sensitive, which is a good thing at higher speeds. A little more awkward at lower speeds, but that's a reasonable tradeoff if you like fast trails. 

If you're into snowboarding, it's similar to sidecut radius: tight radius = responsive at slower speeds, but loose at higher speeds, large radius = awkward at slower speeds, but locked in at higher speeds. 

And as noted above it moves the front wheel further forward, which lowers the odds of going over the bars, especially in the steeps.

A change of 1 degree is pretty subtle. One's brain adjusts quickly. Don't worry about it.


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## C.M.S (Aug 28, 2009)

When building a bike , and in search of a frame fist off , is the HA spec the first thing y'all look at ?


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## keen (Jan 13, 2004)

C.M.S said:


> When building a bike , and in search of a frame fist off , is the HA spec the first thing y'all look at ?


No. Determine what type of terrain and then find a frame bike to suit ie. XC, trail, AM, FR, DH. Most HA are based on the intended use. A XC might have a 70* HA to emphasize quick turning and stable climbing. A DH bike might have a 65* HA to aid high speed stability. Within a category, ie. DH, HA may range from lets say 63-66* if you have a choice look @ all the geometry spec's as a whole and choose based on intended use. HA's can also be modified using custom HS's / anglsets.


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## C.M.S (Aug 28, 2009)

keen said:


> No. Determine what type of terrain and then find a frame bike to suit ie. XC, trail, AM, FR, DH. Most HA are based on the intended use. A XC might have a 70* HA to emphasize quick turning and stable climbing. A DH bike might have a 65* HA to aid high speed stability. Within a category, ie. DH, HA may range from lets say 63-66* if you have a choice look @ all the geometry spec's as a whole and choose based on intended use. HA's can also be modified using custom HS's / anglsets.


It would be AM type application


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## keen (Jan 13, 2004)

C.M.S said:


> It would be AM type application


 When I purchased my last AM frame I first decided how much travel I wanted. Then I compared all the different suspension] designed offered. When I had choices I compared the geometry spec's. Most AM frames had similar HA spec's around 67*. The overall geometry narrowed my search. Then it was review reading time and if possible (can be important) demo demo demo.


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## NWS (Jun 30, 2010)

C.M.S said:


> When building a bike , and in search of a frame fist off , is the HA spec the first thing y'all look at ?


It might be the last thing. Most bikes for a given style of riding (AM vs XC vs DH) are within a degree or two, so the differences will be pretty subtle and so not likely to be a deciding factor Plus you can use an Angleset to add or subtract a degree or so, if you're really picky.


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## Trasselkalle (Sep 5, 2014)

It's not like there is one measurement to first nail down, then the next, and so on. One degree more or less is nothing to fuss about if the reach, chainstay length, wheelbase are all looking like bikes you have liked previously. From bikes with similar geo (and this doesn't quite apply to you as you are building up from a frame), I'd easily pick based on the spec, reported strong customer service and longevity, as well as of course price point over a particular measurement. 

FWIW, over all different bike types I have (including CX), I think reach is probably the one that most seems to affect my own comfort with a bike - particularly with bikes I sit and pedal on a lot. Nothing beats riding many different bikes for a while before figuring out what you like and don't like from a riding position point of view, so try to do that over theorycrafting too much.


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## TravellerSeko (Aug 11, 2021)

darkest_fugue said:


> NOOO, let me try and put it another way, think of slack as the the front wheel being further out in front of you when you ride, this means going downhill its more stable in front because that wheel is out in front of you more and can save you going over the bars etc, a steep head angle means the front tyre is more under you than out in front of you so its not as controlable down steep terrain and theres more chance of you going over the bars, downhill bikes and freeride bikes have slack head angles and xc bikes have steeper head angles, thats as simple as i can put it


Year 2022 and this explanation still saves life 😂 cheers mate 👌🏻


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