[Closed] Advice sought - Alloy Hardtails and Ride Quality

Finally, once you go full-suss, does frame material only really matter for weight reasons?

Yes no maybe 😉 The skill is to get the right properties in the right place in the frame to make it do what you want it to. Sometimes that is steel or alu, carbon arguably gives the builder/designer more freedom to get the properties where they want it.

As for the HT, what rubber do you have on the back and what pressure?

As for the HT, what rubber do you have on the back and what pressure?

2.5” Aggressor at around 19psi - after playing around with it this seems the best balance of comfort and grip. It’s a V2 non-boost Zero so tyre clearance is limited to 2.5”

It depends on the frame and the tyre sizes, no? My old 26" Mmmbop felt it was made from solid bars of alloy rather than hollow tubes. My Sonder Transmitter has a much more comfortable ride, but then it's on 2.8" tyres and has a flat / bladed top-tube that supposedly is more compliant.

You can still make a harsh frame from ti or steel. And you can make a softer riding alloy frame, but it will likely crack relatively quickly thanks to the extra flex. But yes, steel and ti frames tend to ride softer. Then again, if you stick whopping great tyres on anything, it's hard to tell what's down to tyre volume and what's frame material and design.

I've ridden broadly the same design of bike - original Ragley 26", Blue Pig, Mmmbop and Ti - and the Mmmbop was light but super harsh, the Pig was heavy but had a nice, supple sort of ride. The Ti was both light and rides beautifully. Some of that was because the various frames had been designed with the strengths and weaknesses of the materials in mind, so the Mmmbop used tubes like drainpipes and the steel / ti ones were much smaller bore, but yes. Of course, if you you'd built the steel frame from huge tubes, it would probably have been harsh and incredibly heavy. And if you'd made an alloy frame using thin tubes, it would ride softer, but as above, be likely to crack, probably.

With full sus, broadly, yes, sort of. I've seen titanium full suspension frames with lots of lateral flex that you can feel when riding because of the give in the tubes. But broadly yes, assuming the frame design isn't overly noodly, mostly it's weight

Never felt alu hardtails I've had have been overly harsh but good steel (my current hardtail is a Stanton Sherpa) is cushier. Mike makes a good point about tyre size and pressure.

As above. Tyres make the biggest difference. I can’t believe that you’re feeling too much of the harshness in the frame running a 2.5” tyres at 19Psi.

You can feel it in roadbikes/gravel bikes. I’ve got a Niner RLT9 with box tube rear stays in alu and it’s a proper bum basher. By contrast, my Tripster using the same wheelset is almost a magic carpet.

Both logic and experience say that the flex of a metal triangle is quite small compared to the deflection of an MTB tyre. So I think that compliance differences between MTB frames can most optimistically be described as small. I think the flex of the seat post can have an effect, whilst seated of course

In a hardtail, when you're seated, vertical compliance from the front triangle would need the seattube to compress or the top tube to either compress or bend. The amount of compliance in the handlebars, stem, saddle, seatpost, tyre and wheel will be much larger than any flex in the front triangle. Seatstays are a different matter, but you will still be getting most of the vertical compliance out of the back tyre. That's not the same as damping though, different materials and frame designs will damp vibrations differently and this may be quite noticeable.

With suspension bikes, the rear suspension will massively overwhelm frame flex for vertical compliance. There is a theory, based on Moto-GP bikes, that twisting of the top-tube provides damping when the bike is leaned over at extreme angles and hits a bump, so steel frames provide Breathing With the Trails because they are springy. The evidence for this in mountain bikes is basically zero, and even if it were measurable, you need to have the bike leaned over beyond 45 degrees for it to start to outweigh the effect of the suspension movement so it's not a vertical compliance effect anyway.

My Zero AM feels about the same in terms of comfort as my Cotic Soul 26” did, so what it lost in frame compliance it gained back from the bigger wheels smoothing things out.

All bike frames twist when being pumped, pushed and pulled through rough corners, it’s inevitable when you consider the magnitude of the forces vs the frame stiffness and the sensitivity of humans to vibration.

OH's got a 26" ally 140mm HT that's really nice to ride but the (similar age) 26" Slackline 631 I had for a bit was ace but harsh.

I did get the 'some hts ride harsh' comments, some of the more hardcore hts like the Stiffee were built pretty solid. Ive a Scandal 29er and that doesn't feel harsh....helped by all the other variables like tyres & pressure. Also run a 27.2mm carbon seatpost shimmed on the Scandal and, given also the fairly high exposed amount of post, its a lot more forgiving when riding seated than say when i have a 31.6 thomson or dropper post on there

It seems then from the discussion so far that the harshness I’m feeling is simply hardtail harshness and having a different alloy frame is not going to make a huge amount of difference.

I find sustained, rocky descents the toughest on my calves/lower back and I think the only real solution is a full squish. A Ti frame might do the job I suppose. Those Vendettas do look nice...

Rear triangle tube section and shape make very little difference as the triangle is an inherently rigid structure when loaded as a rear triangle is.

Front triangles, whilst triangular aren’t actually loaded like rear triangles. I think someone said they are actually loaded like a truss. So what happens in a front triangle is the fork is basically trying to rip the head tube off, basically kind of rotating about the top of the downtube.

This means that the top tube bends. And you can feel it or see if if you get really sad and glue bits of cotton thread to the midpoint of the top tube.

Flat top tubes do make this flex more. Skinny top tubes too.

Though compared to a fat tyre it is minimal, it’s certainly perceivable and also it’s effectively moving the bars relative to your hands too.

I find sustained, rocky descents the toughest on my calves/lower back and I think the only real solution is a full squish.

Ride more.

Do some strength and conditioning training.

Or buy a full suspension bike. Then you will just ride faster until you get the same problem.

I find sustained, rocky descents the toughest on my calves/lower back and I think the only real solution is a full squish.

I have a hardtail and a couple of suspension bikes that I ride on the same rolling descent that takes me about 7 minutes on a good day. My calves and lower back suffer the same regardless of the bike. Might be different for a proper
DH or enduro bike though.

Got a Whyte 900 series with the swoopy seat stays. With the wheel out, the dropouts flex a lot. The rear triangle has no bracing either. It feels pretty compliant but that's probably more down to 19psi in a 2.8" tyre and my weight forward due to the long geo.

Maybe I’d be better off with a new frame simply to accommodate 2.8” tyres.

Or, as mentioned, I could just toughen up and ride more 😉

I had a Stif Morf for a bit and I swear o could feel the seatstays flex (in a good way), but it was probably in my head. One of the best steel hardtails I’ve ridden. A proper hooligan, but also a very nice feel. Regret selling it

Interesting comment Brant, are you suggesting that top tube design is the key differentiator in ride feel on alu hardtails? Or are there other factors (in the frame)? How about chainstay length?

WRT the OP - Bird Zero vs Sonder Transmitter - the main difference here will be the big fat rubber on the Sonder. Will muffle any difference in frame feel.

It seems then from the discussion so far that the harshness I’m feeling is simply hardtail harshness and having a different alloy frame is not going to make a huge amount of difference.

Correct. If you were using 23c tyres at 110psi then you may be able to feel some differences but in my experience even then it is small.

Thanks for the insight all; appreciated

Went from Sonder transmitter (alloy)to Cotic Solaris max (Steel). Both 2.8/3.0 tyres & hope wheels, same forks. Solaris so much smoother, less harsh and.......Fast!

I don’t think another alloy hardtail is likely to make much difference. Maybe a steel or Ti frame may have a marginally different feel (more damped?) but with a soft 2.5” tyre already I don’t think you’re going to see a huge difference.

I can ride my full suss hard and legs are fine all day on an uplift day. Yet a few months back I did a half day at Flyup 427 uplifting on my hardtail and by lunch my legs were ruined. Had a fantastic time - and the hardtail tips on corners but over frequent drop offs etc you can’t beat a fs.

I've got Procaliber 6 that has a bit of flex in the seat tube while your seated.

Interesting comment Brant, are you suggesting that top tube design is the key differentiator in ride feel on alu hardtails? Or are there other factors (in the frame)? How about chainstay length?

If you look at a carbon road bike you'll see that there some have a lot of top tube flattening for this reason

But I never really believed in vertical compliance then I read the article below. Now I just don't belive that people can feel the flex vertical flex difference for MTB frames. Remember this is about road bikes with thin tyres. I'll start with a quote then the link

"During the 303 Roubaix development, we broke the entire bicycle system into component stiffnesses to try and determine the relative contributions of things to ride quality. We were shocked to find that the entire difference between the special, longer wheelbase, layup optimized, cobble specific frame, and the standard road frame (which everybody could tell you was WAY too stiff to ride on the cobbles) equated to a whopping 4psi of tire pressure."

https://www.slowtwitch.com/Tech/Thoughts_on_science_perception_4571.html

having a different alloy frame is not going to make a huge amount of difference

Having ridden some light alloy hardtails (and some cheap heavy ones, like yours), I'd disagree.

That was a few years ago on 2" tyres are higher pressures tho.

That article was very interesting - I can certainly see how our preconceptions of what should be more compliant would make us feel like that was the case.

I’d be interested in reading a study centred around MTB descents and comfort; where you’re not sat but stood. Vibrations are coming straight up from your feet and effecting your whole lower body; i’d be interested to know if frame material had a bigger influence in this case.

Wouldn’t fancy a blind test on an MTB descent though 😉

Going from 'sprightly' Sanderson 26" steel to 27.5" alloy Marin.

Absolutely depends more on psi, tyres, wheelflex, saddle and seat post flex so much more than frame. That said, seat post made the Sanderson comfy seated and I could see wheel and frame deflection on that bike when stomping or railing bumpy turns.

The only time I've ever thought that a frame was stiff is huge rocky Cairngorm like descents, occasionally at Laggan, or descending from Swiss border back to Lindarets - and that was on steel frame...

I've got a double butted retro steel bike, with skinny tyres on it. I've also got an alloy 4x do it bike with a machined yoke and bigger tyres. The steel bike is massively different in harshness even with skinny offroad tyres ( 1.8 ) although it was built before the new standard of testing. I've also got an alloy framed offroad ht and this is much harsher than the steel bike, even again with bigger tyres ( 2.1) I know they are different bikes, but the material makes a massive difference to me although mostly I think it's how it has been built.

A few years back I bought a Mondraker Vantage frame to check out the forward geometry concept. I liked the bike but, the ride was a bit harsh. I sold that and finally got a Pipedream Moxie. While not a direct comparison the Moxie has a much more compliant ride with similar sized tires than the Vantage.