I can understand that reducing head angle and lowering the bottom bracket will make a bike more stable at speed (in a straight line), but does it actually increase the range of things that you can get down?

I’ve always assumed that, if you want to ride steeper, more technical stuff, then you want a slacker head angle (with consequently longer forks). But now I’m not sure so sure. The difference in head angle is pretty small compared with the variability in the terrain (if a 30% hill feels like a 28% hill does that really make an difference?) and the longer fork is a bit harder to put where you want.

So, I’m just wondering, do any of you find that a slacker head angle gives you the confidence to go down stuff that you wouldn’t attempt with a steeper angle, or does it just let you go down the same stuff faster?

No, don’t worry about it.

Low BB = better cornering. Probably helps on steep stuff a bit too.

It’s about caster angle and stuff. It’s not about the angle relative to the hill.

You’ve been reading to many magazines.

Yes – to both questions

Steep => go faster
Steepest => becomes possible

I feel more comfortable with low and slack on steep stuff , but my 29er Salsa Spearfish also felt great on steep techy stuff , very low BB on that bike, but not slack , me no understand , I think alot has to do with the whole bike not just some of the angles.. Brant will be able to explain , far better..

Thanks. No reading involved this time though.

I have a Trance (69 degree HA) and a 2006 Five. I’ve just put an angle reducing headset and offset bushings into the Five. With the Revs at 150mm that gives a (static) HA of 66 degrees. So, based on like for like measurements, the Five is three degrees slacker than the Trance and has 25mm more travel up front (seat angle and rear travel are pretty much the same, as is BB height). It’s still early days for the testing, but so far I’m stuck by how much more stable the Five feels going down smooth fast straight trails, but I wouldn’t say that it’s made technical stuff any easier.

The technical stuff (steering etc at slower speed) may actually be slightly worse due to a longer wheelbase. I’ve just fitted offset bushes to my 6.6 (2 degrees slacker1/2″ lower BB) and found that it was so much quicker and smoother on the fast descents but didn’t steer quite as well on really tight/slow turns. We’re only talking a very small change in steering but it was noticeable..

The steeper the head angle the more over the back wheel you have to be. On really – really – really steep stuff it may be possible to get down in a straight line but if any turns are required you will find you have unweight the front wheel to the point where when you turn the bars you just go straight on.

I know this as there is a certain suicide descent (with a nasty turn around a tree) at my local riding spot. I can just about ride this on my big slack bike but every time I attempt it on my hardtail I go straight on into the tree on full lock resulting in a big unpleasant crash.

A slacker head angle creates more castor, which is what self centres the steering. This helps with downhill stuff and straightlining rock gardens etc. Typically these bikes are a touch longer in the wheelbase which also adds stability but also robs low speed manoeuvrability.

Main thing is not to take one figure out of context though, it’s the balance of the whole bike that matters.

All IMHO…

There are lots of variables, as you mentioned steeper bikes (well, modern ones anyway) tend to have less travel than their slack chums. Slacker, longer travel bikes require a bit more body language to do what you want but this is a good thing when it comes to cornering and the like. Once you adapt to being more dominant and dynamic on the bike you can deal with the thing in more awkward situations. Equally the same can be said for riding a steep, short travel bike on steep terrain as you have to keep it in contact and absorb deflection.

I think the added oomf you need to give the longer travel bike is equal to a broader range of control as you have more degrees of subtlety to achieve the same thing. Rather than a twitchy ride with a narrow range of response which invites smaller inputs, like a track bike for example. A twitchy bike on deflective terrain (rocky/rooty etc descent) will be harder to control, it doesn’t help that bars are often narrower on these bikes!

I can’t put my preferences down to HA or BB height alone. I ride a Blue Pig X and like it’s slackness without a low BB (medium I’d say). Slack feels good to me, but I’m sure there’s a tipping point where it becomes unwieldy. Having a 150/130mm Rev means I can steepen and lower for climbs, it rides well like this too.

+1 what oldnick said. You want a good balance for all the terrain you ride.

I rode a 456 Summer Season once (66? deg HA, so slack) and it was fine smashing through rock gardens at speed but steered like a barge everywhere else. I’d trade a small amount of stability for nimbleness any day. Having said that, old school frames with 71 deg head angles are rubbish on proper steep/fast stuff.

Personally, I find anything slacker than 67 deg is too slow for my liking, but then I’m an old bmxer so don’t mind it steering quickly.

Low + slack = your weight is down and back, a good place to be on steep stuff.

Fashion victims! Bet none of you go any faster or ride anything steeper since buying your new low, slack bikes

If only GW was here to help…….. If only

Placebo effect.

It’s about caster angle and stuff. It’s not about the angle relative to the hill.

+1

Or in english it where your weight is and how that interacts with your front wheel’s contact patch. A low BB and lack HA/long fork pushs the front wheel forewards and your weight down, so the angle from the front wheel to your COG is lower (and less likely to pitch you over the front). The slack angle and offset of the fork mean that the steering tends to self center more which makes it stable.

none of you go any faster or ride anything steeper since buying your new low, slack bikes

DH tracks are certainly less scary on my Pitch. And anything more ‘all mountain’ is certainly faster.

Tight XC singletrack is a harder and slower though compared to the Swift with it’s 72deg HA!

Fashion victims! Bet none of you go any faster or ride anything steeper since buying your new low, slack bikes

I haven’t ridden steeper stuff but the steep stuff I do ride I am definitely quicker on (or my mates are getting slower) as we’ve done the same route for the last few rides and I’ve been waiting for longer @ the bottom..

Ha ha.. Love that’s called “practice”,

Really? That must be the case then…but surely, if that were the case, my mates would be “practising” too – no?? So would they not be getting quicker too??

Slackening a bike rather than buying a slack one can, IMO, ruin the climbing ability with the seat angle being slackened too much. But every bike is different and some can handle it better.

Everyone’s learning curve is different

Placebo probably has a lot to do with it, as has been mentioned above.

Many people blame the bike underneath them for their riding, when it’s the rider 99% of the time…

stevied’s new ride for 2014!

Blimey, that’s funny… 🙄 good use of the word ‘probably’ there too

Yes – absolutely slack and long makes for more stability, which in turn makes it possible to go faster when on pointy down stuff, and also get down stuff you couldn’t on a steeper and higher bike.

I’m no scientist but my sister (who is) sort of explained it to me in terms of the front axle being a “pivot”, so the lower and further back the mass centre is relative to that pivot, the more stable it is.

All I can do is comment from personal experience and the changes I have made relative to my own bikes – as soon as I slacken it out (I have 2 Bionicons so can do this on the fly for real comparison), the bike becomes more stable.

As I say, I don’t really understand the theory behind it, but can definitely back up the net result, and ultimately that is all that matters.

but does it actually increase the range of things that you can get down?

This is much more to do with rider skill than head angle and bb drop. It will make a difference, but it is not as much as you might think.

Since when did the trails become so steep you can’t ride them on an older, steeper geo bike?

Have trails really changed that much in the last 15 years?

Maybe those having difficulty riding a steep H/A bike need to book themselves on a skills course? 😉

I’m neutral on the slack bikes thing (geometry-geek joke, boom-tish), but to be fair to those wanting them or liking the confidence of them, DH pros have been riding more and more raked-out bikes over that last few yrs. 66 was normal, now its 63-64 for a lot of them? They have the skills and still ride some very slack bikes.

It won’t make a difference if you can’t ride that slope on an xc bike going slower, it’s just one of those things that help people feel comfortable on the right tool for the job. Like lighter bikes, rigid vs FS bikes, 1×10 vs 3×9, fatter tyres, etc etc etc.

This:

A slacker head angle creates more castor, which is what self centres the steering. This helps with downhill stuff and straightlining rock gardens etc. Typically these bikes are a touch longer in the wheelbase which also adds stability but also robs low speed manoeuvrability.

Main thing is not to take one figure out of context though, it’s the balance of the whole bike that matters.

All IMHO…

My Bluepig is brilliant on fast DH stuff and confidence inspiring on the proper steep stuff.

However when things are flatter/twistier/slower you have to bully it about using 785mm bars and a lot of body english.

jamesco: It won’t make a difference if you can’t ride that slope on an xc bike going slower

This is the key point for me. I can see that, if you want to go fast on rough ground, slack is the way to go. But in terms of just being able to get down stuff I’m not sure it helps.

The points about having to move your weight further back and pivoting around the front axle are interesting, but doesn’t that have more to do with the front centre distance than the head angle itself? I think that this is what I’m seeing with my two bikes. The Trance is a Large (20″) and the Five a Medium (18″). The Trance also had a lower BB to start with. So the slacker Five probably puts the front wheel in about the same place as the larger Trance and the BB is pretty similar too.

The caster effect is clearly noticeable. If you are going fast the slacker Five holds its line better. But when mincing down a trail (my default mode for anything steep or technical) I’m not sure it makes any difference.

Incidentally, using an angle adjusting headset combined with offset bushings reduced the head angle by 2 degrees while keeping the seat angle the same. BB dropped by around 1cm.

I think head angle fails to make any difference once the rear wheel leaves the ground, and it’s only a matter of hand and COG position relative to contact patch 😉

Didn’t anybody on STW learn to ride (not just to the shops and back, but off-road) on a rigid with a [relative to today’s standards] steep HA??

Think my bike at the time was some Giant Boulder (weighed a tonne, steep HA and v-brakes)..

I am yet to ride a trail/track/path thinking “I couldn’t have done this with a 2 degree steeper head angle”.

Man up!

It doesn’t make a blind bit of difference to ability.

If you can’t, you can’t, it’s all in your head.

Are you still riding the Boulder?

No, it got nicked a long time ago. Only paid about £100 for it then…

My current bike frame dates back to 2000…. which amusingly was considered very slack back then…

But given the chance, I’d happily ride a rigid bike from that era on ‘modern’ trails…

Fashion victims! Bet none of you go any faster or ride anything steeper since buying your new low, slack bikes

😆

I’ve got to say that it has taken me a while to get used to the difference between the Rocket, slack & low,and the Trek,less slack more xc, but it has been very slippery since I bought it & the balance on the Rocket is excellent.

Ride it, enjoy it, generally it’s all good. Modern bikes are great, just got to ride what suits you.

Fashion victims! Bet none of you go any faster or ride anything steeper since buying your new low, slack bikes

Definitely riding much steeper stuff, much faster than 2 years ago.

For me it’s also a bit of a chicken & egg situation. Longer slacker bike has inspired confidence, so I now go for more stuff at higher speed, and in turn am constantly raising my game in terms of technique too.

duirdh – Member

Fashion victims! Bet none of you go any faster or ride anything steeper since buying your new low, slack bikes

I’ve still got my old, less slack bike- I go down stuff tons faster on my newer, slacker bike.

Head angle analogy could be: If you are pushing a wheel barrow along a stony track, you would drop your wrists to help the wheel ride over the bumps; likewise if you were pushing a unicycle in front of you, you would hold the saddle as low as necessary to allow the wheel to ride over the bumps.
I put a 1deg angleset on my Blur and it now rides over obstacles rather than hitting them.