Mountain Biking general thread

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ZedLeg
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Re: Mountain Biking general thread

Post by ZedLeg »

Jobbo wrote: Tue Jun 15, 2021 10:08 am
Rich B wrote: Tue Jun 15, 2021 9:51 am
Jobbo wrote: Tue Jun 15, 2021 9:46 am
Absolutely right - I do wonder what a cromoly framed MTB would be like if anyone made one now.

Frame design should suit the material it's made from. I'm not a massive fan of aluminium; CF is just a more appropriate material since you can make a frame stiff and strong without adding lots of wall thickness.
Alu is a great material for bike frames - light, strong, cheap, stiff, repairable, not too brittle, etc....
Castings are brittle. Not sure it's that stiff or repairable either - not like steel.

That Santa Cruz video breaking alu and CF frames was an interesting comparison.
Just looking for an argument this morning Jobbo? :lol:

There's a reason that all high end mtb frames were made from Alu until cf became more mainstream, it was the best compromise of all the factors at the time. CF is better in a lot of ways but it's still very pricey compared to alu and while the Santa Cruz video was interesting they're putting forces through the frame that ware way beyond what most people would expect. Personally alu is still the best compromise of how I like the bike to feel and how much I'm willing to pay.
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Jobbo
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Re: Mountain Biking general thread

Post by Jobbo »

Gavin wrote: Tue Jun 15, 2021 9:55 am My only mild concern is the Orbea is on 29" wheels and I have only ridden 27 or 26 way back when. As a not very tall bod, I am hoping that won't make a ball squishing difference to crossbar height on a medium.
I'm a proper shortarse and have the smallest Orbea frame on my Wild FS - which I think is basically the electric version of yours with similar geo with 29" wheels - and the standover height is just about acceptable. The dropper post makes it perfectly usable. I didn't try a medium to compare though.
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Re: Mountain Biking general thread

Post by Gavin »

Jobbo wrote: Tue Jun 15, 2021 10:14 am
Gavin wrote: Tue Jun 15, 2021 9:55 am My only mild concern is the Orbea is on 29" wheels and I have only ridden 27 or 26 way back when. As a not very tall bod, I am hoping that won't make a ball squishing difference to crossbar height on a medium.
I'm a proper shortarse and have the smallest Orbea frame on my Wild FS - which I think is basically the electric version of yours with similar geo with 29" wheels - and the standover height is just about acceptable. The dropper post makes it perfectly usable. I didn't try a medium to compare though.
Ah, the heady days of going to a bike shop and simply trying various sizes to see which suited.... :lol:
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Jobbo
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Re: Mountain Biking general thread

Post by Jobbo »

ZedLeg wrote: Tue Jun 15, 2021 10:13 am There's a reason that all high end mtb frames were made from Alu until cf became more mainstream, it was the best compromise of all the factors at the time. CF is better in a lot of ways but it's still very pricey compared to alu and while the Santa Cruz video was interesting they're putting forces through the frame that ware way beyond what most people would expect. Personally alu is still the best compromise of how I like the bike to feel and how much I'm willing to pay.
Not particularly looking for an argument - I just spent a lot of time cycling while doing my engineering degree, where my tutor was a specialist in materials science. And I didn't have the money to buy bikes made of interesting materials back then; now I've had alu and CF bikes it just interested me.

As for the forces Santa Cruz put through the frames; frames do break in use, so they aren't that unusual. Direct comparison of equivalent alu and CF frames was interesting.

The reason for alu was twofold; it's lighter (less dense) than the traditional steel, and steel is best in tubes. Tubes aren't necessarily easy to form into shapes which suit full suspension; aluminium can be extruded into assymetric profiles which are stiffer and stronger in specific directions. CF has material properties which are simply better than alu so provided it's a frame optimised for CF and it's made properly, it should be a win-win. Yes, it's pricier; alu bikes were pricier than steel at first. I think potentially we're getting to the point where CF is not much more than alu for a frame though.
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dinny_g
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Re: Mountain Biking general thread

Post by dinny_g »

Never ridden a CF bike but is there a noticeable difference to Alu ?? Hypothetically, if 2 identical frames were made, one from CF and one from Alu, would you notice the difference - flex etc ?

My Specialized is Alu - quote old now (2007) but I loved the construction and the way the size of the tubes changed in size and shape at key points to add rigidity or structural strength.

As a kid who grew up coveting anything with a Reynolds 531 tubular steel frame, I remember when the first Cannondale's arrived with their Huge thick frame tubes and being mind blown - the bike that floats on water... :lol:
JLv3.0 wrote: Thu Jun 21, 2018 4:26 pm I say this rarely Dave, but listen to Dinny because he's right.
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Re: Mountain Biking general thread

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They feel different as materials. CF doesn't ring like metal so has a more dull sound. I don't know whether we can perceive the stiffness difference in normal use with an up to date alu design; I'd love to see some slow-mo footage of how they deflect when landing jumps. You wouldn't make the same frame design out of both materials anyway; if you did the CF frame would be unnecessarily thick and heavy, but probably strong enough for a troupe of elephants to ride.
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Re: Mountain Biking general thread

Post by drcarlos »

dinny_g wrote: Tue Jun 15, 2021 10:56 am Never ridden a CF bike but is there a noticeable difference to Alu ?? Hypothetically, if 2 identical frames were made, one from CF and one from Alu, would you notice the difference - flex etc ?

My Specialized is Alu - quote old now (2007) but I loved the construction and the way the size of the tubes changed in size and shape at key points to add rigidity or structural strength.

As a kid who grew up coveting anything with a Reynolds 531 tubular steel frame, I remember when the first Cannondale's arrived with their Huge thick frame tubes and being mind blown - the bike that floats on water... :lol:
Alu is very harsh feeling it doesn't absorb any bumps or vibration (as if it flexes like a steel bike does it fatigues very quickly and fails) but gives a very sharp feeling frame. CF is almost dead feeling as it absorbs the vibrations and can be made to flex where required with good resistance to fatigue.
You wouldn't build the two frames identically because of the different properties of the two materials.
You have to look at the old 80's/early 90's alu frames to see this. Where they copied steel frames without knowing how the materials would behave (good example are Manitou frames) long term the majority failed with classic points are on or around the head tube where stresses are high. This is the same for CF and Alu.
The only thing I don't like the idea of CF is that when it fails it totally fails, there is no progression, the aforementioned headtube failures would at least have got you home on an Alu frame, CF will just leave you eating dirt with a long walk if you aren't injured.
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Rich B
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Re: Mountain Biking general thread

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Jobbo wrote: Tue Jun 15, 2021 11:05 am They feel different as materials. CF doesn't ring like metal so has a more dull sound. I don't know whether we can perceive the stiffness difference in normal use with an up to date alu design; I'd love to see some slow-mo footage of how they deflect when landing jumps. You wouldn't make the same frame design out of both materials anyway; if you did the CF frame would be unnecessarily thick and heavy, but probably strong enough for a troupe of elephants to ride.
Loads of manufacturers have the same basic frame design in both CF and alu. The YT Capra is a good example of this.
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John
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Re: Mountain Biking general thread

Post by John »

I’ve been for a ride into the Peak District earlier, absolutely perfect riding conditions

Image
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Simon
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Re: Mountain Biking general thread

Post by Simon »

Looks shit. ;)
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John
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Re: Mountain Biking general thread

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Yeah, I almost turned around and came home :)
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Re: Mountain Biking general thread

Post by Jobbo »

Rich B wrote: Tue Jun 15, 2021 11:28 am
Jobbo wrote: Tue Jun 15, 2021 11:05 am They feel different as materials. CF doesn't ring like metal so has a more dull sound. I don't know whether we can perceive the stiffness difference in normal use with an up to date alu design; I'd love to see some slow-mo footage of how they deflect when landing jumps. You wouldn't make the same frame design out of both materials anyway; if you did the CF frame would be unnecessarily thick and heavy, but probably strong enough for a troupe of elephants to ride.
Loads of manufacturers have the same basic frame design in both CF and alu. The YT Capra is a good example of this.
I bet they're not very similar in cross section; they certainly won't be popping out of the same mould. But yeah, the aluminium version of my Orbea looks pretty much the same as the carbon one. Doesn't cost significantly less either.
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Re: Mountain Biking general thread

Post by Rich B »

Jobbo wrote: Tue Jun 15, 2021 3:20 pm
Rich B wrote: Tue Jun 15, 2021 11:28 am
Jobbo wrote: Tue Jun 15, 2021 11:05 am They feel different as materials. CF doesn't ring like metal so has a more dull sound. I don't know whether we can perceive the stiffness difference in normal use with an up to date alu design; I'd love to see some slow-mo footage of how they deflect when landing jumps. You wouldn't make the same frame design out of both materials anyway; if you did the CF frame would be unnecessarily thick and heavy, but probably strong enough for a troupe of elephants to ride.
Loads of manufacturers have the same basic frame design in both CF and alu. The YT Capra is a good example of this.
I bet they're not very similar in cross section; they certainly won't be popping out of the same mould. But yeah, the aluminium version of my Orbea looks pretty much the same as the carbon one. Doesn't cost significantly less either.
well you're obviously not going to be welding carbon fibre tubes together...
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Gavin
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Re: Mountain Biking general thread

Post by Gavin »

Whoop Whoop, got myself a new bike, well a 2018 but it has been ridden half a dozen times and has upgraded bits and bobs and the reviews seem to suggest a good all rounder.

It is a Vitus Sommet CR in blue and orange. My darling wife will no doubt be delighted at the £1000 odd I saved on the new Orbea too.
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Re: Mountain Biking general thread

Post by Gavin »

Has anyone changed their saddle over? It is the only thing on my bike that shows wear so I thought I would treat myself.

I don't want a dafty razor blade thing, anyone any recommendations please? The bike is sort of blue and orange so probably black.
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dinny_g
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Re: Mountain Biking general thread

Post by dinny_g »

Depends on what you want... :)

Mine had a hardcore ultra think Specialized racing saddle which I put up with for years but a few weeks ago, I accepted my 47 year old coccyx couldn't take it any more and bought a "Comfy" saddle.



It's very good and my back pain is gone but it does look like it came of a Childs bike :lol:

There are plenty of "comfortable" saddles that look a little more purposeful if you prefer...
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Jobbo
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Re: Mountain Biking general thread

Post by Jobbo »

My Orbea came with a Selle Royal Vivo saddle on it (which isn't at all pricey if you want an aftermarket saddle); it's more comfy than the similar-shaped Specialized saddle I've had for a decade but it's all down to personal shape. And wearing shorts with a decent pad in. I've never found ostensibly more padded saddles comfier, FWIW; they press in different places, yes, but not necessarily with any benefits after a few hours.
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Re: Mountain Biking general thread

Post by Gavin »

That does look comfy and I absolutely acknowledge the irony of buying a solid saddle and wearing padded shorts!

As the rear of this one is suspended I think something between solid and boingy would be ideal.
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Re: Mountain Biking general thread

Post by Rich B »

YTs come with horrific saddles that hurt after about 15 mins, I have Charge Spoons on all my bikes - comfortable, reasonably priced and strong without looking like massive gel filled monstrosities found in Halfords/Amazon.
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Re: Mountain Biking general thread

Post by Jobbo »

That's the one I was trying to remember, Rich - seems to be highly recommended whenever there's a saddle thread. Even among roadies.
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