Rainier Posted May 28, 2015 Posted May 28, 2015 Hi I have a Specialized Epic Comp 29er with standard Roval wheels. I do about 330km of XC riding per month max. I got a pair of ZTR FLOW EX wheels for a bargain. Apparently its strong wheels and more suitable for AM riding. My main concern is that the ZTR's are much wider than the Rovals. Correct me if I am wrong, but wider rims will put more rubber on the ground and will improve handling, especially in single track, but at the same time increase rolling resistance. Will I improve my riding or not? Is this a upgrade or not? I am not planning on keeping both sets, one must go. Thanks in advance
Josh0 Posted May 28, 2015 Posted May 28, 2015 The Flows are great rims, they are more for All Mountain/Downhill use though. So they might weigh somewhat more than the Rovals. They are wider, so they will give more volume for your tires. Some say that wider rims are the shizniz, I am yet to upgrade to wider rims. Definitely on my upgrade list. I wish they where 26", then I would have been interested to take them off your hands. Cheers
Captain Fastbastard Mayhem Posted May 28, 2015 Posted May 28, 2015 Correct with your thoughts, except the rolling resistance bit. Lower pressures will decrease rolling resistance, up to a point, as your tire is more likely to absorb the undulations in terrain rather than deflecting off them, which results in a tiny loss in speed. It will improve the characteristics of the bike, improving handling characteristics and improving the profile of the tyre. It won't improve your riding, as that's skill related, but it will make it easier to progress in your skillset. They're also far lighter.
Mathieu_Schneuwly Posted May 28, 2015 Posted May 28, 2015 Flow ex rims: Pros: bigger tire volumeLower pressure possibleImproved grip, handling rough terrain better Cons: more weight (I think)More rolling resistance due to larger tire profile. I stand to be corrected.
Captain Fastbastard Mayhem Posted May 28, 2015 Posted May 28, 2015 The Flows are great rims, they are more for All Mountain/Downhill use though. So they might weigh somewhat more than the Rovals. They are wider, so they will give more volume for your tires. Some say that wider rims are the shizniz, I am yet to upgrade to wider rims. Definitely on my upgrade list. I wish they where 26", then I would have been interested to take them off your hands. CheersRoval Control 29er wheelset weighs more than 2kg according to the reviews online. Flows will be lighter than that for sure. Even if they aren't, they're far wider... Roval has an external width of 24mm, so internal is likely to be 18/19mm. Flow EX internal width is 25.5mm - at least 6mm (33%) wider than the Rovals. No brainer, really.
Captain Fastbastard Mayhem Posted May 28, 2015 Posted May 28, 2015 Flow ex rims: Pros: bigger tire volumeLower pressure possibleImproved grip, handling rough terrain better Cons: more weight (I think)More rolling resistance due to larger tire profile. I stand to be corrected.This is offset due to the behaviour of a wider tyre at lower pressures having less rolling resistance than a thinny tire at higher pressures over the same terrain. Ergo - wider rims increases volume of the tire, allows you to run lower pressures, reduces overall rolling resistance whilst also increasing grip and lateral rigidity. Google the studies, if you wish.
Josh0 Posted May 28, 2015 Posted May 28, 2015 Roval Control 29er wheelset weighs more than 2kg according to the reviews online. Flows will be lighter than that for sure. Even if they aren't, they're far wider... Roval has an external width of 24mm, so internal is likely to be 18/19mm. Flow EX internal width is 25.5mm - at least 6mm (33%) wider than the Rovals. No brainer, really. Damn, them Rovals are heavy. Flows FTW!
Rick Sanchez Posted May 28, 2015 Posted May 28, 2015 What hubs are the Flows built onto?If they weigh less than the Rovals, and they are wider, then definitely go with the Flow (see what I did there? ). I think they will also have better resale value than the Rovals and in my opinion the Flows look much better, which is all that really matters, right?
droo Posted May 28, 2015 Posted May 28, 2015 If they're on Hope hubs, go for it. Stan's hubs are a bit under-specced in the bearing department so will need plenty of maintenance, particularly on the rear. But still an improvement on the Rovals. If they're properly built the only way you'll break them is by driving over them.
Steven Knoetze (sk27) Posted May 28, 2015 Posted May 28, 2015 This is offset due to the behaviour of a wider tyre at lower pressures having less rolling resistance than a thinny tire at higher pressures over the same terrain. Ergo - wider rims increases volume of the tire, allows you to run lower pressures, reduces overall rolling resistance whilst also increasing grip and lateral rigidity. Google the studies, if you wish. El Capitan, I am not doubting you but do you have any substantive, scientific, proof of this. I'm battling to wrap my head around your statement in bold above. My understanding is surely a squishy tyre, regardless of terrain will have more rolling ressistance? Wider rim with a higher volume tyre running low pressure aids grip, grip only aided because there is a large contact patch between tyre and ground. So, therefore, on the same given terrain, a thinny, low volume and higher pressure tyre would roll easier. Logically speaking that is.
Captain Fastbastard Mayhem Posted May 28, 2015 Posted May 28, 2015 El Capitan, I am not doubting you but do you have any substantive, scientific, proof of this. I'm battling to wrap my head around your statement in bold above. My understanding is surely a squishy tyre, regardless of terrain will have more rolling ressistance? Wider rim with a higher volume tyre running low pressure aids grip, grip only aided because there is a large contact patch between tyre and ground. So, therefore, on the same given terrain, a thinny, low volume and higher pressure tyre would roll easier. Logically speaking that is.You're right, when looking at the contact patch in isolation. But as with all things, you cannot look at that factor alone. The long and short of it is that the increase in contact patch and the corresponding increase in rolling resistance that comes from that, is outweighed by the reduction in rolling resistance that comes from the reduction in pressure that you would be able to run as a result of the wider rim profile. Essientially, taking the same tire on the same rim, one at high and one at low pressures - the lower pressure tire will absorb and roll over undulations more easily than the higher pressure tire will. Higher pressure tire bounces off the undulations, causing incremental deflections which rob you of forward momentum... I don't have the studies at hand, but they are there.
Captain Fastbastard Mayhem Posted May 28, 2015 Posted May 28, 2015 Taking the above into consideration though, there is the law of diminishing returns, as well as weight, that comes into it if you run different tires, heavier rims, etc etc.
Captain Fastbastard Mayhem Posted May 28, 2015 Posted May 28, 2015 Oh - forgot to add above. The grip isn't only increased at lower pressures due to the larger contact area. It's also because the tire is able to mould itself to the terrain and thus GRIP better. If you're running 2 tires, one with 30PSI and one with 20PSI, which one has the most potential to form itself to the ground it's on, given a certain downward / sideways force? The one with lower pressure. Now which one has more grip? The one with lower pressure. There is the point at which it becomes a bit silly and you start getting higher RR from the lower and lower pressures though. Haven't yet seen what point that is though. Also - remember the "rolling road" tests that the labs use don't mimic MTB all that well, as it's a completely flat surface.
Lance Cruz Posted May 28, 2015 Posted May 28, 2015 "Also - remember the "rolling road" tests that the labs use don't mimic MTB all that well, as it's a completely flat surface."The frequency changes in terrain are too myriad to really make a conclusive argument. Tread blocks (size, shape, energy absorption properties) are a huge influence here and often misunderstood. 'Contact patch' is a concept often misconstrued in MTB, incorrectly borrowed from road car tyre engineering where there is very little lean and surfaces mostly ideal. A mountain bike tyre, measured on a ratio of cross-section to tread block and crucially profile to rim size, has a radically different application of the notion of said 'contact patch'. Even low-pressure tread elongation is a bit of a misnomer here, you are mostly riding on select tread blocks. Wider (not ultra wide) rims with lower pressure tyres will yield a ‘terrain moulding’ benefit, but there is a point at which XC tyres on narrower rims, on median trails, will be more efficient with lower rolling resistance than DH-type tyres on wider rims. The complexity of replicating terrain, or measuring it actively, is hugely challenging. I am not aware of a conclusive study where this has been done: even in Enduro motorcycle racing.How fatiguing is a fat bike to pedal if it is rolling carbon rims and the lightest possible tyres compared to a 650+? Perhaps a litmus test for the low-pressure=lower rolling resistance argument.Back to topic: am a Flow user. Bomb-proof rims that float tyres quite tidily.
Captain Fastbastard Mayhem Posted May 28, 2015 Posted May 28, 2015 "Also - remember the "rolling road" tests that the labs use don't mimic MTB all that well, as it's a completely flat surface." The frequency changes in terrain are too myriad to really make a conclusive argument. Tread blocks (size, shape, energy absorption properties) are a huge influence here and often misunderstood. 'Contact patch' is a concept often misconstrued in MTB, incorrectly borrowed from road car tyre engineering where there is very little lean and surfaces mostly ideal. A mountain bike tyre, measured on a ratio of cross-section to tread block and crucially profile to rim size, has a radically different application of the notion of said 'contact patch'. Even low-pressure tread elongation is a bit of a misnomer here, you are mostly riding on select tread blocks. Wider (not ultra wide) rims with lower pressure tyres will yield a ‘terrain moulding’ benefit, but there is a point at which XC tyres on narrower rims, on median trails, will be more efficient with lower rolling resistance than DH-type tyres on wider rims. The complexity of replicating terrain, or measuring it actively, is hugely challenging. I am not aware of a conclusive study where this has been done: even in Enduro motorcycle racing. How fatiguing is a fat bike to pedal if it is rolling carbon rims and the lightest possible tyres compared to a 650+? Perhaps a litmus test for the low-pressure=lower rolling resistance argument. Back to topic: am a Flow user. Bomb-proof rims that float tyres quite tidily. Agreed - which is why I was keeping it simple, and saying the same tire on a wide rim vs narrow rim etc. As soon as you bring other variables into it (different tires, different casings, different weights) it becomes a much more complex argument and cannot solely be brought down to a variation in pressure or rim width. Weight, sidewall rigidity, etc etc all form part of what is known as "rolling resistance" to many. So - your fatbike comparison would have to have the same weight wheels & tires in order for it to be an accurate comparison, and from there we should progress in either direction, in one area / variable at a time in order to get an accurate representation of what effect each variable has on the whole. As yet though - I've seen nothing like that. I want to, and I really want to read something like that but I have a feeling it'll be a long time coming. Aaaaanyway. in the OP's case, the new wheels will be both lighter AND wider AND stronger, which makes them better all around. Lower rolling resistance due to the lower pressure, less rotational weight meaning better acceleration (and the imitation of lower RR as a result of this) and better handling. On the same tires.
Mada3400 Posted May 28, 2015 Posted May 28, 2015 weight counts for more if its spinning... however, things that boost confidence count for more than things that weigh less if your bike is slightly heavier but you feel a lot more confident on it youre probably going to be faster, if youre not at least youre going to be having more fun... but meyhem says theyre lighter, and wider, sounds like a win win.
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