15mm through axle vs QR for 29er?

[lock]

So who is doing the epic on a DH rig now??? Bliksem...

 

Anyway...gents I think both of you have a small peace of the puzzle...tire flex is real...so too is wheel flex...if you use the crappy rims that came with you rocky V in 1990 and pump the tires to 6bar...it is going to feel a little more responsive or stiff...same goes for the hectic awesome bling bling stiff almighty wheelset...if the tire pressure is less than say 6 bar...(Thumb suck) the tire flex will be noticeable..the question was...is it necessary for the epic...NO, screw the weight advantage or disadvantage..is it necessary for AM and DH, yes cause you are bombing the crap out of the rig down a silly slope full off rocks and ruts...will you notice the difference on your xc rig? Yes..for that 0.0009% where you pushed the QR past its limit...if your wheel moves..fasten the damn QR you wuss...

 

And where are the engineers..what about spoke lenght? You will gain loadsa more stiffness by just chopping 3inches off...hat coat door...I need to finish some work...

[covie]

So who is doing the epic on a DH rig now??? Bliksem...

 

Anyway...gents I think both of you have a small peace of the puzzle...tire flex is real...so too is wheel flex...if you use the crappy rims that came with you rocky V in 1990 and pump the tires to 6bar...it is going to feel a little more responsive or stiff...same goes for the hectic awesome bling bling stiff almighty wheelset...if the tire pressure is less than say 6 bar...(Thumb suck) the tire flex will be noticeable..the question was...is it necessary for the epic...NO, screw the weight advantage or disadvantage..is it necessary for AM and DH, yes cause you are bombing the crap out of the rig down a silly slope full off rocks and ruts...will you notice the difference on your xc rig? Yes..for that 0.0009% where you pushed the QR past its limit...if your wheel moves..fasten the damn QR you wuss...

 

And where are the engineers..what about spoke lenght? You will gain loadsa more stiffness by just chopping 3inches off...hat coat door...I need to finish some work...

 

Ok im not even going to bother anymore, the only way you will know is to buy a bike with thru axle, once you have had enough experiance on QR. If you like it or not, thruaxle is a vast improvement on QR, the only reason why QR was in place is because outdated thruaxle systems took too long to remove, now that this problem has been sorted out get ready to have 15mm thruaxle as a XC standard as it exploids the disadvantages of QR.

[Johan Bornman]

Marketing K@K!!!

 

All this talk about having too low tire pressure and all. HOGWASH!! the big reason for going big wheels is to get an even lower tire pressure.

 

I sincerely doubt that's the reason behind bigger wheels. I suspect it is marketing but...we can post-rationalise this forever and never find the reason.

 

Bigger wheels don't protect you from the perils of low tyre pressure - bump through.

 

 

 

 

So do the math, the lower the tire pressure the more the sidewalls will flex, period!

 

 

Of course that is true, but weaving that into bigger wheels makes it scientifically difficult. You seem to want to do the math, go ahead, do it. I'll give you a hint, you're looking for the relationship between a larger surface area at the contact patch and the pressure in the tubular structrue.

 

 

 

Another example [of marketing hogwash] is the "....." from Fulcrum Wheels with 2:1 spoke lacing. WTF! More spokes, heavier wheels, and why? is the drive side and/or the braking side not attached to the hub which will evenly distribute the force across the hub's width. Or do the "new through axles" make the hubs weaker so that there is now a twist some where???

 

 

Torque, from braking and/or pedalling, is NOT evenly distributed through the hub. The reason is simply that the hub is not infinitely flexible. Lightweight hubs with small centre diameter are very poor at distributing torque across. There is definitely twist in there. However, I'm not disputing your diagnosis marketing hogwash, just questioning your flawed reasoning for saying it is hogwash.

[Johan Bornman]

 

Question is is the surface area of a 29" tyre the same as a 26" tyre?

 

This analogy may help you - Ask yourself whether the area of grass to mow on a 400m althletic track is more or less than that on a 3km horse racing track?

 

If I knew how emoticons worked I would have posted one of a tonque-in-cheek oke.

[Dicky DQ]

I sincerely doubt that's the reason behind bigger wheels. I suspect it is marketing but...we can post-rationalise this forever and never find the reason.

 

Bigger wheels don't protect you from the perils of low tyre pressure - bump through.

 

 

 

 

Of course that is true, but weaving that into bigger wheels makes it scientifically difficult. You seem to want to do the math, go ahead, do it. I'll give you a hint, you're looking for the relationship between a larger surface area at the contact patch and the pressure in the tubular structrue.

 

 

 

 

Torque, from braking and/or pedalling, is NOT evenly distributed through the hub. The reason is simply that the hub is not infinitely flexible. Lightweight hubs with small centre diameter are very poor at distributing torque across. There is definitely twist in there. However, I'm not disputing your diagnosis marketing hogwash, just questioning your flawed reasoning for saying it is hogwash.

 

Hi Johan, sorry my layman's terminology is probably wanting, as is my logic and experience. However, all I was getting at is:

1. Though axle technology does not provide any perceived benefit over QR

2. Tapered headset does not provide any percieved benefit over normal

3. 2:1 spoke lacing does not provide any percieved benefit over normal lacing

 

Because, now with bigger wheels with more rubber and the opportunity to run lower pressures it all seems to be negated by the additional (flex, movement, whatever in the tire.)

 

Just my observation...... Not scientific, measured etc. All that I know is the 26" tire with QR "moves less side to side" and thus feels More "safe/secure/rigid etc. but that is just me.

[sometime]

In your physics calculations... Which surface area are you going to put into your formulae? The circumferential surface area (around the outside perimeter) or the cross sectional area (if you cut through across the tyre)?

 

The contact surface area

[Dicky DQ]

Anyway fun was had on the keyboard instead of on the saddle, excuse the pun Johan.

[NotSoBigBen]

There you go

 

[sometime]

Covie the whole discussion around the relative surface areas of 26" tyres and 29" tyres is actually very interesting so it's a pity that instead of engaing in an interesting discussion from which we all can learn, you chose to not answer my question by asking a rhetorical one.

 

For shoes to support a person's weight the upward force exerted by the shoe, opposing the weight, much be equivalent to that weight. So for a woman's heel measuring 1 square inch in surface area to support 100kg (=220 pounds), then that force opposing the weight would be the equivalent of 220 pounds per square inch (psi). However for a man's shoe with a surface area of say 44 square inches the force would reduce to the equivalent of approx. 5psi. That's why we run 10 bar in our road tyres and 2 bar in our MTB tyres - the surface area is vastly different.

 

So once again (phew!) do we know if the surface area of a 26" tyre is less than that of a 29" tyre?

 

From my perspective I'm running much lower pressures on my 29er than I did on my 26er but I'm running high volume Schwalbe 29x2.25 vs. low volume Maxxis Larsen 26x2.0 and 2.1 so the comparison is pointless for the purposes of this discussion.

Edited May 9, 2012 by sometime

[covie]

Covie the whole discussion around the relative surface areas of 26" tyres and 29" tyres is actually very interesting so it's a pity that instead of engaing in an interesting discussion from which we all can learn, you chose to not answer my question by asking a rhetorical one.

 

For shoes to support a person's weight the upward force exerted by the shoe, opposing the weight, much be equivalent to that weight. So for a woman's heel measuring 1 square inch in surface area to support 100kg (=220 pounds), then that force opposing the weight would be the equivalent of 220 pounds per square inch (psi). However for a man's shoe with a surface area of say 44 square inches the force would reduce to the equivalent of approx. 5psi. That's why we run 10 bar in our road tyres and 2 bar in our MTB tyres - the surface area is vastly different.

 

So once again (phew!) do we know if the surface area of a 26" tyre is less than that of a 29" tyre?

 

From my perspective I'm running much lower pressures on my 29er than I did on my 26er but I'm running high volume Schwalbe 29x2.25 vs. low volume Maxxis Larsen 26x2.0 and 2.1 so the comparison is pointless for the purposes of this discussion.

 

I am always open to a discussion, sometime, but that needs to then be a descussion based on fact and not fiction as was the case here. Put it to a previous poster that thinks its all marketing, is there a need to create thruaxle to make more money, no there is not you will still sell the same amount of bikes that contain the same amount of wheels. selling the same amount of stock. The stiffness ratios are measured through years of practical and scientific tests. And he claims he knows better and can dispute this wthout having any factual evidence to back up his statements. Thats not a debate thats a comedy.

 

Anyway scientific principles aside, look at a DH bike vs XC bike, a DH bike will have 2.4 inch high volume tyres, for traction or and grip and they pay the penalty of rolling resistance.

 

An XC tyre will usually be 2.1 or 2.2 for less rolling resistance and less grip. The contact of the surface area is much more pronounced in the width and the volume of the tyre than it is due to the diamter of the tyre.

 

Hence the diamter has a negligable influence between 26 and 29 inches, since your surface area will not substantially increase sinc4 your tyre volume and width still remain constant. Theres a small change but a negligable change and that does not mathematically translate into the abiltiy to support yourself using lower tyre pressures.

Edited May 9, 2012 by covie

[covie]

but tyre flex aside since it has abosulty nothing to do with a QR vs thruaxle, since on both you will be using rubber. Fact is that Thruaxle is stiffer and in the world of mountainbiking the aim is to loose as much weight and gain as much stiffness or rigidity as possible. And that is what ThruAxle offers over QR the gains in rigidity outweighs the weight penalty hence it will become the new standard. Weelsize and rubber is a different debate.

Edited May 9, 2012 by covie

[Iwan Kemp]

...if you use the crappy rims that came with you rocky V in 1990 and pump the tires to 6bar

...your tire will explode in one very epic looking Jeanne Claude van Dam way when you hit the first big rock or root and send you flying like Captain America can only dream of.

 

...if the tire pressure is less than say 6 bar...

..it will still explode, but more in a Twilight meets Jackie Chan kinda way.

 

[dev null]

OK, reading through this thread I am now confused. I have a very nice Fox F32 with 9 QR on my BMC FS02 26er. I am planning to use Easton EA70XC (UST) tyres on it.

 

From the general consensus (sic) it is not really a benefit to upgrade my Fox F32 to 15 QR, even though such an upgrade does exist. For a 26er the cost of the upgrade does not justify any benefits?

 

Yes, agree, if I were to buy a new Fox fork today I would not hesitate to get the 15 QR.

[Iwan Kemp]

OK, reading through this thread I am now confused. I have a very nice Fox F32 with 9 QR on my BMC FS02 26er. I am planning to use Easton EA70XC (UST) tyres on it.

 

From the general consensus (sic) it is not really a benefit to upgrade my Fox F32 to 15 QR, even though such an upgrade does exist. For a 26er the cost of the upgrade does not justify any benefits?

 

Yes, agree, if I were to buy a new Fox fork today I would not hesitate to get the 15 QR.

1. Easton EA70XC (UST) is not a tyre model. That's a wheelset.
   
2. Regardless of wheelsize there benefits and gains to having a thru axle but it is very much RIDER dependent.
   
3. On most 100mm XC bikes it's not probably not worth the upgrade just for the sake of. If however you are buying in any case then go fot it, yes. Just remember taht not all hubs can be converted which will only add to the total cost of the upgrade should you have to upgrade hubs or complete wheels.
   
4. There are better ways to spend upgrade money
   

[PhilipV]

Here is how I see it.

The QR vs TA is one part of a whole system. The stiffness gained will be percieved when the other elements in the system remain the same (tire pressure, spoke and rim stiffness.)

If however you run lower tire pressure, you will feel tyre flex, and that will mask the "feeling" of the increased stiffness of the TA.

Same if your TA wheel flexes more than your old QR wheel. Or vice versa, if you had a QR wheel with a bit of flex and you compare it to a stiff TA wheel the difference in stiffness will be in the axle interface and in the wheel.

 

I say "feeling" as it needs to be felt out on the trail. If difference can only be measured in a lab or with maths and feels the same on the trail, it is pointless.

 

Wrt to the 26vs29 contact patch: both are the same size, but the 29 will have a longer, narrower contact patch compared to the 26, but that is only if the tyre pressures remain the same.

 

I reckon the TA will feel stiffer, but that it needs to be seen in context of the bike as a whole.

If it gives you more confidence when bombing the trails, go for it. At the end of the day you need to ride what you like, and what gives you more enjoyment on the trails.

[Iwan Kemp]

"At a claimed 1555g, the Spline XR1450 29 is one of the lightest aluminium 29er wheelsets on the market. As with most DT Swiss wheels, it will be available with a quick-release or thru-axle. The company believe that quick-releases are already dead on 29ers and will soon go the same route on 26in wheels, as even cross-country riders accept the 50g or so penalty for the extra security and stiffness a 15mm thru-axle offers."