I got ti456 with a ti post and saddle. It replaced a Chameleon with a Thomson post. Helped my back enormously 🙂

Stays are triangulated, relatively short and consequently flex is very small compared to other things be that tyres, seatposts even the frame main tubes which you can visibly see flex.

I’m not disagreeing, a large back tyre, a saddle with flexy rails and a long thin seatpost will make infinitely more difference than a frame designed to have a bit more flex.

Obviously if you made stays thin/narrow enough they’d provide lots of flex but it’d be crap under power and fatigue could be a problem too so just not practical in the real world.

If you make it out of aly, yes fatigue is going to be a problem. With steel, or certainly ti, I don’t think you’d ever stretch/bend/compress a stay in any way shape or form enough to push it past its elastic limit. So fatigue shouldn’t really be an issue.

As to wavy stays, because there isn’t significant flex in the rear triangle, it’s pretty irrelevant.

I’d always assumed more to do with mud clearance issues, or just to look nice to be fair, but if bendy enough (a la Whyte 19 steel or ti) they could make a bit of difference probably.

I should probably add that I did some stress analysis on this at uni as part of a project and that’s why I’m confident it’s right.

Fair enough, I would agree with you that it’s nowhere near as important as some people make out, but it can make a difference. Have you ever ridden a really flexy, noodly titanium hardtail? You can’t question its strength as the material is inherently strong, it’s just quite a flexible material compared to ally or even steel. If you look at something like a first generation Cotic Soda (known to be pretty flexy, I’ve seen one visibly bend a lot at the BB/chainstay area) compared to something with much beefier/stiffer stays from the outset… It’s actually visible. OK, the flex may literally only be a few mm (so less than a 2.3″ tyre would deflect under load by some margin), but there is a difference.

Haven’t read the the entire thread, so it may have been suggested already.

Get a steel frame – it has a magical zing property that will make it exactly like a full suss frame but without losing any of the hardtail benefits.

I’d have thought that the single most important thing would be riding position which is probably going to mean higher bars.

Not necessarily at all… I suffer from back pain a bit, sometimes it comes on whilst I’m riding.

The way I’d combat it on a bike would be to ride a bike 2 sizes too big for me, with a negative rise stem and flat bars… To stretch me out and stop any curvature occuring in my back.

A shorter more upright position is great for control, but not so great for my back at all!

b r & wippersnapper – your thoughts on the 2nd Gen 456Ti? Is it stiff out back or does it give? (I had the 1st Gen and it felt super springy).

Mboy – reread my post 🙂

I didn’t say frames don’t make a difference as I’ve ridden lots and there clearly is a difference but I don’t reckon it’s down to the stays but rather the frame as a whole and is significantly influenced by the top tube and interestingly, frame ‘splay’ where the wheels move apart (fork plays a large part in this).

Tubeless + Rubber Queen 2.4 at the back, run about 20psi and you’ll have a noticeably more compliant hardtail, regardless of which frame you go for. Works really well in my experience.

Deevass, I forgot to say, mine is the old one too.

Speaking as someone who has always ridden a HT and then suffered from a prolapsed disk (Then having surgery to correct) I would suggest a suspension seat post. I had a cane creek one that really helped. I know they look ugly and they add weight etc but from a comfort point of view it really helped my back.

I now have a full sus, partly due to the kind of biking I do but even for general XC stuff, crunching miles etc i don’t come home feeling like I need another MRI to see if my back has gone again.

Don’t suspension seat posts **** up your pedaling when they compress?

Only if you set them up too soft

Didn’t Brant say that some FEA or other modelling suggested that the chainstays (or seat or both, can’t remember) counterintuitively tended to ‘want’ to flex horizontally rather than vertically under load? So if you were to flatten them in the opposite direction to what you’d think, i.e. pinched from the sides rather than the top and bottom, it would have the greater effect in increasing what we refer to as ‘vertical’ compliance? Not sure what this would do for ‘lateral’ stiffness or the tendency of the rear wheel to move relative to the headtube, but that might also have a counterintuitive effect!

The latest carbon frames seem to have really narrow but not flattened seatstays to increase ‘vertical compliance’, wonder if that allows this horizontal flexure to occur more easily? Empirically, I’ve been unable to feel much in the way of frame differences that couldn’t have been saddle, seatpost or tyre differences, apart from a Specialized Roubaix which seems genuinely a lot ‘softer’ than the steel frame and forks it replaced – and it has the same saddle, tyres, a fatter diameter seatpost bars and stem (all of which should increase stiffness), same rear wheel, tyre pressures etc. If I could find a carbon XC frame that did the same I’d be all over it – tempted to try the new Scotts and Cannondales that advertise low weights AND high ‘comfort’…

Haven’t read the the entire thread, so it may have been suggested already.

Get a steel frame – it has a magical zing property that will make it exactly like a full suss frame but without losing any of the hardtail benefits.
Well if you did bother to read the thread you’d notice that people are shooting down that theory! Remember we’re talking about real compliance to bumps here (compared to a full-sus, sus post or fat soft tyres), not some “magical zing” property of the frame.

If you make it out of aly, yes fatigue is going to be a problem. With steel, or certainly ti, I don’t think you’d ever stretch/bend/compress a stay in any way shape or form enough to push it past its elastic limit. So fatigue shouldn’t really be an issue.

Except that you don’t need to stress steel or ti past their elastic limit in order to fatigue them (if you did that would be yield rather than fatigue). Whilst they do have a “fatigue limit”, that’s well short of the elastic limit, and designing the stays to flex sideways enough to give any sort of suspension effect is very likely (I’d say almost certain, but can’t be bothered running the numbers to back that up) to put them over that. There is a lot of misunderstanding about this “steel and ti don’t fatigue” thing, with some lightweight steel/ti bikes flexing enough that they will fatigue, whilst many alu bikes are sturdy enough and well enough designed that they’ll last a lifetime of normal use.

FWIW I did some calcs on frame flex a while ago (for “fun” rather than a uni dissertation), and came to pretty much the same conclusion clubber did, that any vertical frame flex was down to “splay” in the main triangle, rather than flex in the stay area. Though it’s still a very minor effect compared even to a normal rear tyre or a saddle, and most splay is due to fork rather than frame flex.

Haven’t read the the entire thread, so it may have been suggested already.
Get a steel frame – it has a magical zing property that will make it exactly like a full suss frame but without losing any of the hardtail benefits.

That was a tounge in cheek comment, surely?

I had a similar dilemma years ago, had a HT frame that I really liked but it did give me a sore back, a big tubeless tyre and a saddle and seat post with a bit of give were much better additions than the cake creek thudbuster I got.
Where as the big tyre and seatpost/saddle make the bike feel just the same (or better) but with a little more comfort, the thudbuster made the riding experience awful.
Maybe they have improved since I used it but it was the single most horrible thing I have ever used, no matter what I did it had a horrible top out and the seat position changing all the time was like riding a rocking horse. A full sus is although a lot more cash, is a much better answer than a suspension seat post, they might be a different riding experience but at least they still feel like a bike!

Sounds like you had it much too soft. It should be set so that it doesn’t move at all while pedalling on normal reasonably smooth trails. It should only move on the bigger hits which are what actually hurt your back.

*takes aracer off the hook and pops him in the keepnet*

I’ve had a bad back on and off for the last 15 years following a bad accident.. My 456 was a huge improvement on the previous giant entry level thing I was using.. which I can almost definitely put down to riding position..

I hurt my back again earlier in the year during a week of heavy lifting.. after some recovery I started riding again but the 456 suddenly was agony.. I fitted a new stem to lift the bars a couple of inches and it’s lovely again..

bar height etc is the key

Would have been better if you said 853 is magically more betterer too 😉

Thudbuster LT….Works so well you don’t really notice it – until you put a rigid post back in again and you then realise what a great job it’s been doing…..

Ditto

And stretch your hamstrings daily.

I don’t think I did have it(thudbuster) that soft, although it was years ago and can’t really remember. To say it was like riding a rocking horse is maybe a bit unfair, as it didn’t move that much on smooth surfaces/fireroads ect or under pedaling, it was more in sections were there were a series of bigger bumps (washboard) type stuff it became horrible to ride.
Personally I found that it was more the endless smallish/mid sized bumps that hurt after a while bigger bumps weren’t such a issue as tended to hop over them.
Although as mentioned before it’s, correct position, stretching and strength (and professional help) work that really makes a difference to a sore back. No amount of parts, even full sus, was ever going to make that much of a difference to me, compared to actually making an effort to stretch and do core work, that has made a difference.
Though the is obviously a difference between back pain from bad posture/bike set up and lack of strength and the pain that comes from jarring form riding off road.

Bigger tyres, tubeless and slightly lower pressure. Move saddle forward a tad. Job done.

*takes aracer off the hook and pops him in the keepnet*

Bah! My excuse is that you usually get people making exactly that sort of comment completely seriously – I’m actually quite surprised that we’re not getting challenged more by people who’re convinced by the comfort advantage of steel/ti over alu, which is normally the case when ever this comes up.

Riding my friends VN Zion Ti, I immediately noticed how springy and spritely it was under pedalling and how this translated to good rear wheel grip when technical climbing. On descending fairly smooth trails it felt muted/damped, like having a bigger, softer tyre. (I didn’t try descending at speed or anything choppy, but I expect that bike feels a bit noodly when pushed hard)

In no way does this compare to the bump flattening effect of rear suspension. But I can see why people say muting effect makes these bikes less tiring than an equivalent Alu HT.

But I still reckon it’s worth investigating cushy tyres and riding position before splashing out on Ti.

Good pointers here. I ride a short stem with high rise bars, it’s the short sharp jolts that cause me problems more than general trail buzz. I’m without a frame at the moment so I’m shelling out for something, just need to shell out for the right thing!! Thanks guys, lots of good comments.

b r & wippersnapper – your thoughts on the 2nd Gen 456Ti? Is it stiff out back or does it give? (I had the 1st Gen and it felt super springy).

2nd generation, as in the Lynskey one with the extra tube – or do you mean the Chinese copy? 😉

kelvin – Member
“Fit” is more important than “give” if you’ve got back problems.

I’m with Kelvin on this – rode a too big Spesh FS a few years ago, and always suffered, went back to the HT after a little under a year, and the back problems stopped. I can follow the suspension post theory and can’t dismiss it as I have not tried a suspension seatpost yet.

b r… I mean the one On One are selling now, I think that may be the copy :o)

Except that you don’t need to stress steel or ti past their elastic limit in order to fatigue them (if you did that would be yield rather than fatigue). Whilst they do have a “fatigue limit”, that’s well short of the elastic limit

Sorry, I actually meant to say fatigue limit, not elastic limit! Ooops…

There is a lot of misunderstanding about this “steel and ti don’t fatigue” thing, with some lightweight steel/ti bikes flexing enough that they will fatigue, whilst many alu bikes are sturdy enough and well enough designed that they’ll last a lifetime of normal use.

Totally agree. I’ve seen lightweight steel frames that will bend and flex so much over a short lifespan that they’re as good as useless after a few races… Anyone remember the Ritchey P20 XC Race bikes of the mid 90’s that were supposedly sub 3lb for a frame iirc?

And of course there are some beefy ally frames out there that will indeed never fatigue cos there’s enough material in them to make sure as good as no flex ever occurs.

It is of course, as you well know though, the inherent ability of both steel and titanium, for a given stength, to flex more than aluminium before fatiguing.

Riding my friends VN Zion Ti, I immediately noticed how springy and spritely it was under pedalling and how this translated to good rear wheel grip when technical climbing. On descending fairly smooth trails it felt muted/damped, like having a bigger, softer tyre.

I presume this is also a troll?

I have a long-term back problem. So that I don’t bend forward so much, I had a made-to-measure steel frame with a taller than normal steerer tube, by a builder who was aware of the problem. It suits me fine. A suss seatpost helps, I wanted one to take out the worst of the jolts without a lot of movement.