Mavic R-Sys

Stone Glider

IIRC G66? usually responds to enquiries about what bike to buy by remarking that everyone always recomends the last bike they had bought. It seems that this thread has gone along similar lines. "I bought it, it must be good" As a matter of general enquiry, is there anyone out there who, having read this thread, is going to buy them?

AllTheGear

I won't be buying them.

Right now I use Aksiums. I'm looking for something a bit more upmarket, although I am not under any illusion they will make me any faster.

There are alloy clinchers that are in the same weight class and are more aero and cost about the same or less, made with conventional spokes. I don't understand the point of R-Sys. Maybe there is a stiffness / ride quality advantage?

I'm considering Easton EA90 SLX, Reynolds Solitude, Open Pro handbuilts etc.

EDIT: I just checked the prices. They are £1000! You can get big name branded, similar weight, more aero wheels for half that, or less.

chriskempton

Have to agree with Stone Glider. The 2 things that stick out from this thread are:

1. Under no circumstances would I buy R-Sys wheels, or possibly even accept them as a gift.

2. Some people on this forum just can't/won't be objective about a product once they've bought it. There's a number of nuggets I could choose, but I'll go with just this one:

Gavin Gilbert wrote:

If the tendancy is for the R-Sys to break in a crash, then that's the tendancy of the wheel. I'm not happy about it, but it's a high-end cutting edge design and I'll have to live with it.

A high end, cutting edge design, so it should inherently be more susceptible to catastrophic failure? :?: :shock: Would a Ferrari owner say the same thing if their brand new motor had just disintegrated whilst doing 70 on the M4?

Pokerface

AllTheGear wrote:

You were riding Ultremo R's and R-Sys?

Glad you're ok!!

Fortunately no. Ultremo's were on my Cosmics.

Gavin Gilbert

Stone Glider wrote:

IIRC G66? usually responds to enquiries about what bike to buy by remarking that everyone always recomends the last bike they had bought. It seems that this thread has gone along similar lines. "I bought it, it must be good" As a matter of general enquiry, is there anyone out there who, having read this thread, is going to buy them?

I was rather thinking it was an arguement between the Evidence versus Preconception.

But had the story broke before I purchased my pair I think I would of held off. As it is I'm not mounting tubs on them until the picture becomes clearer.

In terms of function, there is a lot out there for similar money but I was hoping the R Sys would be a better bet for hilly rides, simply because of the stiffness. I'm 94kg of beefcake and when I'm out of the saddle I can flex most wheels.

AllTheGear

I'm only 62kg so a heavier rider may appreciate a stiff wheel. I guess they are the stiffest in their weight class then?

Pokerface

I have a question...

If a plane crashes due to some sort of mechanical failure - would you never fly again because of that? What if they didn't know where the failure occurred? But the plane virtually just drops out of the sky...

But not ALL planes are dropping out of the sky. Not even a lot of them. Maybe just the one...


Does this analogy apply in any way to the R-Sys problem before us? We are faced with one (currently) unsubstantiated failure of an R-Sys wheel. No proof (yet) as to why it happened, the root cause, additional factors, etc. So far - just the one failure that is being reported - not like every other new R-Sys wheel is falling apart...

Yes, I'm slightly blinded by the fact I have a set. If I didn't own them I wouldn't ride them right now. But I can't afford to throw £500+ worth of wheel away on a whim.

If they get recalled again I shall demand a full refund somehow. Until then I guess I'm taking my chances with the friendly skies. I mean roads.

always_tyred

Gavin Gilbert wrote:

Stone Glider wrote:

IIRC G66? usually responds to enquiries about what bike to buy by remarking that everyone always recomends the last bike they had bought. It seems that this thread has gone along similar lines. "I bought it, it must be good" As a matter of general enquiry, is there anyone out there who, having read this thread, is going to buy them?

I was rather thinking it was an arguement between the Evidence versus Preconception.

But had the story broke before I purchased my pair I think I would of held off. As it is I'm not mounting tubs on them until the picture becomes clearer.

In terms of function, there is a lot out there for similar money but I was hoping the R Sys would be a better bet for hilly rides, simply because of the stiffness. I'm 94kg of beefcake and when I'm out of the saddle I can flex most wheels.

Stiffness - I think this is the real motivation for the design. Even then, though, why not save up another £500 and get some Lightweights?

Evidence vs. Preconception.... mmm..... it would have been preconception if it was the first time. Given that its happened before, and given that the design fundamentals are the same, the better "scientific method" would be to look for reasons why the cause might be different, with the assumption that the cause is the same, rather than assume the causes are different unless they can be demonstrated to be the same.

You get a flat tyre. You take the tube out. It has a hole in it. You put another tube in, pump it up, and it goes down. Question - same bit of glass in the tyre, or some random failure in the both tubes?

Stone Glider

@ Gavin Gilbert

The Evidence is that the wheels can break.

The Preconception is that a product chosen by you is fit for purpose.

Have I got it right?

Gavin Gilbert

Stone Glider wrote:

@ Gavin Gilbert

The Evidence is that the wheels can break.

The Preconception is that a product chosen by you is fit for purpose.

Have I got it right?

Nope. Learn how to read posts and then come back.

lost_in_thought

Blimey!

I'm pleased to read in the velonews article that my ksyriums don't use those carbon spokes!

That really is one heck of a wheel failure. Clearly, I wasn't there and have no idea what actually happened, but mavic's response seems to be clutching at straws a little... Is there a picture of the un-damaged fork? My net nanny loves to hide pictures...

il_principe

I'll not be buying the R-Sys. I accept that things fail occasionally but I have a general rule about steering clear of products that I know have had a recall at some point. I do this simply as cycling kit is expensive (generally) and I don't want to spend money on something that *might* fail catastrophically when there are products on the market that have had no reported issues, perhaps I don't deal well with disappointment. I know that this is basically illogical, but there you go. I don't like Mavic anyway - I have no reason for this other than a deep rooted mistrust of French engineering (and the fact that my Mavic using mates prefer my Fulcrums) - again illogical and perhaps prejudiced but there you have it (incidentally I love France!)

I'm no engineer, but it does seem to me that there is something inherently problematic with the the R-Sys design - I thought that compression spokes went out along with the horse drawn cart. I'll be sticking with Fulcrum wheels for the forseeable, break a spoke on those and the chances are you're gonna get home ok.

jimmcdonnell

A slightly tangential question (no pun intended), but can someone explain the concept of 'compression spokes' to me?

Am I misunderstanding something - the way I visualise spokes working is that the rider/bike weight is transferred through the hubs to the spokes, and ordinarily will effectively hang from the spokes on the top of the wheel at any given point in its rotation; and therefore at any moment the spokes on the lower half of the wheel will be (if not actually compressed) under less tension?

What's structurally different about these ones that means they're actually compressed instead of just relaxed a bit?

I have no intentions of owning a set of these wheels, I'd just like to know what I'm not understanding properly here.

(Edit) OK, forget I asked, I've just done what I should have done in the beginning and found out on the Mavic website myself. Interesting concept, and chapeau Mavic for thinking outside le boite, but I wouldn't ride them day-to-day; which isn't what they're for, I guess. I assume they tested thin-wall metal (Ti?) tube for the spokes instead of carbon? I suppose you just to work through the (benefits of lightness/stiffness)/(risk of catastrophic failure) maths for yourself.

AllTheGear

You're right, normally all the spokes are under tension all the time, and when riding the ones at the top are under (very very slightly) more tension. The change in tension as the wheel rotates is tiny compared to the static tension.

The R-Sys spokes are not tensioned up in this way, the ones at the sides of the wheel are relaxed and the ones at the bottom go into compression. They have to be thick to avoid elastic collapse.

lost_in_thought

AllTheGear wrote:

You're right, normally all the spokes are under tension all the time, and when riding the ones at the top are under (very very slightly) more tension. The change in tension as the wheel rotates is tiny compared to the static tension.

The R-Sys spokes are not tensioned up in this way, the ones at the sides of the wheel are relaxed and the ones at the bottom go into compression. They have to be thick to avoid elastic collapse.

So... wait, I still don't understand... are the R-Sys spokes not under tension, so the hub is essentially sitting on the lower spokes without a pulling support from the upper spokes?

AllTheGear

The hub is pulling on the spokes in the top of the wheel, and pressing down on the spokes in the bottom, at the same time.

lost_in_thought

So what's the difference between that and a normal wheel...? Specifically, the difference that makes it a compression thingy?

AllTheGear

In a normal wheel all of the spokes are in tension. The hub is pulling on all of the spokes. The force is large on every spoke, so when you sit on the bike nothing changes much.

This also applies to the rim, in a normal wheel the rim is in compression, like an archway. In R-Sys the rim will go into tension in the lower part of the wheel.

Because the loads are very much less in R-Sys (in the spoked and rim) they can be built with less material.

jimmcdonnell

An old party trick may help here (I never got invited to the best parties) - if you get a potato and a drinking straw, by carefully holding the straw and quickly & decisively prodding it straight at the potato, it will stab right through the offending spud without breaking.

http://www.youtube.com/watch?v=PV5Qk6La8F4&feature=related

Quite a neat trick if you can get it just right. The structural properties of a tube make it very rigid when force is only acting directly along its length - any hint of bending and it collapses.

I assume what they're getting at here is that unlike on a regular wheel where the changing tension of the spokes is designed-in, on R-Sys wheels the spokes stay rigid all the time - regardless of the tension/compression forces exerted on them by the normal rolling of the wheel and the transfer of weight as a spoke moves from top-side-bottom of the wheel.

Seems to me, if trees were 100% rigid, they'd snap and fall in a gale. Controlled bending can be advantageous. Rigid spokes might be great, but when they go...

biondino

If the R-Sys spokes aren't under tension, does that mean that they effectively act as suspension and give a smoother ride?

AllTheGear

biondino wrote:

If the R-Sys spokes aren't under tension, does that mean that they effectively act as suspension and give a smoother ride?

Materials tend to have very similar elastic properties under tension or compression, so a material in tension works just as well as a spring, as in compression.

The R-Sys spokes are very thick, and carbon fibre is a very rigid material. The wheels are billed as being rigid. I doubt there's much suspension effect...

jimmcdonnell

The spokes appear thick but they're hollow. In any case, since the rigidity is the USP I assume any 'suspension' (eg the tiny amount you'd get from the flex in normal spokes) is absent. Assuming 115psi+ tyres, the analogy to wooden wagon wheels is probably very apt here too. Not a wheel to be ridden without a good dentist on call to replace fillings shaken out...

Stone Glider

@ GG

Nope.