[Nim]

Will you really notice a difference in MTB climbing between tires, say with similar compounds and tread patterns where one weighs 600 grams and the other weighs 750 grams - a difference of 0.33 pounds per tire?

 

[fred3]

I wouldn't, but a racer might.

 

[tlg]

Will you really notice a difference in MTB climbing between tires, say with similar compounds and tread patterns where one weighs 600 grams and the other weighs 750 grams - a difference of 0.33 pounds per tire?

Probably. That's a considerable difference of rotational weight.
Take a 600g weight and tie it to a string. Spin it around 50 times. Then switch to a 750g weight and spin it 50 times. See which tires out your arm quicker.

 

[bitflogger]

Will you really notice a difference in MTB climbing between tires, say with similar compounds and tread patterns where one weighs 600 grams and the other weighs 750 grams - a difference of 0.33 pounds per tire?

For sure if the light weight gets a pinch flat, and less so otherwise. Less rotating mess is better up to a point. You should consider your riding terrain in the equation and make sure that saving weight will not have a penalty in terms of reliability. YMMV, but I've only had pinch flats on small and light weight tires.

Good luck.

 

[Chester]

Please, I can't listen to this analogy one more time

Probably. That's a considerable difference of rotational weight.
Take a 600g weight and tie it to a string. Spin it around 50 times. Then switch to a 750g weight and spin it 50 times. See which tires out your arm quicker.

Is there such a thing as "rotational weight"? Yes

Is it anything like spinning a weight on a string around and around with your arm? NO

The weight on a string is only in one postion......the weight on the tire is spread evenly all around the tire. Completely different.

Rotational weight is no different than normal weight UNLESS the bike is accellerating.
On a normal cross country race rotational weight as a "negative" is greatly over rated.
In certain pure climbing situations where the bike is down to about 2 mph than quickly up to 8 mph and back and forth over large rocks and roots etc. rotational weigh will have a bit more effect, but in most riding situations there is very little difference between normal frame weight and rotational weight.

Rotational weight vs other weight is perhaps the most exaggerated concept in biking.
Focus on weight of all parts and forget about rotational weight.
A ligher tire is superior regarding weight because it is lighter, no so much because of rotational weight.
Thinking about rolling resistance instead of rotational weight is much more important when thinking about tires IF both of them have adequate grip for your use.

 

[tlg]

Rotational weight is no different than normal weight UNLESS the bike is accellerating.

Ok, you try riding your bike with a 100oz filled camelbak, then try dumping that 100oz into one of your tires (they're about the same volume) and tell me you don't notice the difference.

I don't know about you, but when I ride, I'm always accellerating/decellerating. Your theory holds true if you're perhaps road riding at a constant cadence on a flat road.

In certain pure climbing situations where the bike is down to about 2 mph than quickly up to 8 mph and back and forth over large rocks and roots etc. rotational weigh will have a bit more effect,

You did read the original post... right?

Will you really notice a difference in MTB climbing

 

[Blue Shorts]

Completely agree with Chester....especially the point about rolling resistance being more important.

 

[Blue Shorts]

Ok, you try riding your bike with a 100oz filled camelbak, then try dumping that 100oz into one of your tires (they're about the same volume) and tell me you don't notice the difference.

I don't know about you, but when I ride, I'm always accellerating/decellerating. Your theory holds true if you're perhaps road riding at a constant cadence on a flat road.

You did read the original post... right?

Now that's just a silly comparison. If YOU read the original post, the question had to do with a difference of 5.3 ounces...not 100 ounces.

5.3 ounces is not a big difference in weight. Rolling resistance is a big factor when comparing it to small weight changes...like in this case.

Your 100 ounces of water in the tires is a good way of illustrating that rotational weight definitely has an effect. It's just a horrible example to show the magnitude of the effect when increasing the weight of a tire by a few ounces.

 

[tlg]

Now that's just a silly comparison. If YOU read the original post, the question had to do with a difference of 5.3 ounces...not 100 ounces.

Absolutely not. You said "Rotational weight is no different than normal weight". If it's no different, then it's no different. You wouldn't notice it whether it was 5oz or 100oz.

So now, obviously it IS different.

 

[B R H]

100 fluid ounces of water is over 6.5 pounds!

I'm sure the difference would be quite noticeable.

 

[Chester]

Give me an ratio........1.1 to 1........or 4.o to 1....?

Ok, you try riding your bike with a 100oz filled camelbak, then try dumping that 100oz into one of your tires (they're about the same volume) and tell me you don't notice the difference.

I don't know about you, but when I ride, I'm always accellerating/decellerating. Your theory holds true if you're perhaps road riding at a constant cadence on a flat road.

You did read the original post... right?

"Ok, you try riding your bike with a 100oz filled camelbak, then try dumping that 100oz into one of your tires (they're about the same volume) and tell me you don't notice the difference."

OK.......adding 100 ounces.....about 6.33 pounds to ONE tire would cause more problems than a 6.33 pounds to your camelback......in part because the sloshing water falling to the bottom of the tire at slow speeds would cause tremendous friction rolling around in the tube rather than just because of the weight alone.

You deal in the absurd. The guy is asking about 600g vs 750g......net 150g spread out over the entire tire and NOT sloshing around. Once that 150 grams gets up to a moderate climbing speed, the "normal" small and relatively slow changes in speed from
4 mph to 5 mph and back to 4 mph will have "relatively" little impact since the amount of total accelleration over the time in seconds involved is small. The situation would be different if the weight were larger OR if the accelleration were great. So if you had two tires, each with an extra 222 grams or one full pound difference AND you were doing constant accellerations from 1.5 mph to 15 mph, then slamming on the brakes back to 1.5 mph and instantly doing full accelleration to 15 mph and repeating over and over.

But the amount of accelleration found in most climbing is, if tested, not nearly as much as most riders think NOR as fast as most riders think. Small amounts of weight, doing relatively small amounts of accelleration over a longer period of time will yield only small amounts of detrimental "rotational weight" effects. Much smaller than most people think.

Having said all of that, the lighter tire is still better (if it has sufficient grip) but mostly because of its weight and having very little to do with the "rotational weight" aspect.
Further, in almost every case the better tire whether it be 600 grams or 750 grams will be the one with the best rolling resistance (as long as it has sufficient grip)

In other words, I would easily choose the 750 gram tire with better rolling resistance characteristics, over the 600 gram tire if both had sufficient grip.

One last question..........if you think "rotational weight" is so extra inportant compared to regular weight, the please give me the ratio that you think expresses this.
Is it 1.1 to 1, or is it 1.5 to 1, or is it 3 to 1 ( only during accelleration)?.............Please give me some figure so I can tell what you are talking about when you focus on rotational weight.

Lastly, YES I know the orginal post was about a "climbing" tire.

 

[tlg]

OK.......adding 100 ounces.....about 6.33 pounds to ONE tire would cause more problems than a 6.33 pounds to your camelback......in part because the sloshing water falling to the bottom of the tire at slow speeds would cause tremendous friction rolling around in the tube rather than just because of the weight alone.

Semantics. Fine, freeze the water so it does't "sloch" around. And gelitin and solidify it. My point is simply rotational weight is different than normal weight.

You deal in the absurd.

Duh. It was to prove a point. (see above) And it wasn't in response to the original post.

Once that 150 grams gets up to a moderate climbing speed, the "normal" small and relatively slow changes in speed from 4 mph to 5 mph and back to 4 mph will have "relatively" little impact since the amount of total accelleration over the time in seconds involved is small.

You have scientific data to support this, or is it just your opinion from experience?

But the amount of accelleration found in most climbing is, if tested, not nearly as much as most riders think NOR as fast as most riders think.

If tested?

One last question..........if you think "rotational weight" is so extra inportant compared to regular weight,

Ummm, where exactly did I say it was so extra important?

 

[jrm]

All things other than weight being the same

Will you really notice a difference in MTB climbing between tires, say with similar compounds and tread patterns where one weighs 600 grams and the other weighs 750 grams - a difference of 0.33 pounds per tire?

yes, because it will take calorie output to drive a heavier tire with a larger contact patch and higher rolling resistance..

 

[shiggy]

Will you really notice a difference in MTB climbing between tires, say with similar compounds and tread patterns where one weighs 600 grams and the other weighs 750 grams - a difference of 0.33 pounds per tire?

Will you notice? Maybe. It can be easier to maintain climbing speed with a lighter tire. Whichever tires you use you will get use to the feel of the weight.

For me tire weight is more noticeable in the handling of the bike. Light wheels/tires react and steer quicker than heavy wheels/tires.

 

[Chester]

Well give us a relative ratio.....or we are talking about nothing

Semantics. Fine, freeze the water so it does't "sloch" around. And gelitin and solidify it. My point is simply rotational weight is different than normal weight.

Duh. It was to prove a point. (see above) And it wasn't in response to the original post.

You have scientific data to support this, or is it just your opinion from experience?

If tested?

Ummm, where exactly did I say it was so extra important?

Look if you only think the ratio of "rotational weight" on a wheel is only 1.01 to 1 compared to other weight (frame, camel back, etc) then we are talking about nothing.
But if you think the "rotational weight" on a wheel is 3 to 1 compared to other weight, then we are talking about something.
I certainly don't deny that there is some extra effect....... I only argue that the effect is usually way over rated by most riders and by those trying to sell tires and wheels.
All things being equal I would choose lighter tires and wheels.

So to understand your postion.........Please give us your ratio........and whether you think it ONLY affects the performance during accelleration.
Ratio please.............if you will, so we can understand what you are talking about.

 

[tlg]

Look if you only think the ratio of "rotational weight" on a wheel is only 1.01 to 1 compared to other weight (frame, camel back, etc) then we are talking about nothing.

My position was simple. Rotational weight is different than normal weight. You can argue all you want and play symantics with ratios.

If you've got test data on ratios, let me see, then perhaps we can have a discussion.

 

[Blue Shorts]

Absolutely not. You said "Rotational weight is no different than normal weight". If it's no different, then it's no different. You wouldn't notice it whether it was 5oz or 100oz.

So now, obviously it IS different.

Try to pay attention. I said that it "definitely has an effect", but the effect is small

I never said it had no effect.

Also, try to stay on track with the original topic. The topic is about the effect of a 5.33 ounce increase.....NOT a 100 ounce increase. In the 5.33 ounce case, the rolling resistance will have a greater effect than the effect of increased rotational mass.

 

[tlg]

Try to pay attention. I said that it "definitely has an effect", but the effect is small

Yes, try and pay attention. Message boards have numerous topics and threads. You jumped into a different thread. Sorry, you didn't say "Rotational weight is no different than normal weight". But my response (which you jumped into) was regarding that. NOT the original post.

 

[Blue Shorts]

My position was simple. Rotational weight is different than normal weight. You can argue all you want and play symantics with ratios.

If you've got test data on ratios, let me see, then perhaps we can have a discussion.

If the effect (try to follow me here) in the REAL world is negligible, then who the heck cares? ....besides you, that is.

You seem to be pontificating to see yourself in print.

Following your logic....When a butterfly flaps it's wings, it will have an effect on the weather..and when you step on an ant, you will change the eco system.

Do you even read what you write?

 

[Chester]

here is the best I've ever seen about ratios

My position was simple. Rotational weight is different than normal weight. You can argue all you want and play symantics with ratios.

If you've got test data on ratios, let me see, then perhaps we can have a discussion.

As usual most people who discuss don't really have more than a vague idea about the ratio.
After all, if rotational weight is ONLY 1.01 to 1 then it is meaningless.......but if it is 2.0 or 7.0 to 1 as many suggest then it would be a much more important.

Sadly you choose to not even guess making all your arguments meaningless.
After all, 1.01 times the 150 grams in question would only equal 1.5 grams difference and then only when accellerating.....

OK.........here is the best I have on the subject........

From a long involved thread on this subject.......a post by Boj who as a physics student has investigated it more then either you are I ever will.
------------------------------------------------------------------------------------------------------------------------
It is a fact that rotational weight on wheels influences acceleration of the bike but in case of MTB this is greatly exaggarated within this community. Commonly quoted is that gram saved on wheels is worth 2 grams. Here are the actual numbers where a gram saved is worth this much on a particular part (and only for cases of acceleration):

hub 1.0007
spokes 1.2043
rim 1.7006
tube 1.8723
tire 1.8723

wheel overall

front 1.563
rear 1.467

Most important thing to note is that this is only the case for acceleration which is not an important performance parameter in MTB as rarely you are accelerating and most of the time going at constant speed grinding up a hill or on a flat. My point is that saving rotational as opposed to static weight has only very small theoretical and no actual real world advantages. In line with that I'd advise you to save weight where it gives you the best gram saved/$$ ratio regardless of weather its rotational or static mass.

http://forums.mtbr.com/showthread.php?postid=10566#poststop

Chief point to remember when using these ratios is ONLY WHEN ACCELERATING!

AND you are NOT accelerating "all the time" as so many are prone to think.
NO, you are NOT micro-accelerating with every pedal stroke

So the 150 gram difference would equal about 75 grams, but ONLY when actually accelerating......meaning "under" acceleration....not steady, not slowing down, not some the change in speed over some root or rock which you go up and over. When you further divide up a climb into the actual time you are accelerating in any significant way, then that brings the 75 grams much lower via divison.......
To use an exaggerated example.....Suppose you were accelerating 1/3 and steady 1/3 and decelerating 1/3 of the climb, then the difference of that 150 differential would be
1.5 minus 1.0 for normal weight giving you 75 grams divided by 3 or ending up with a extra penalty of 25 grams..........

Now the reality of climbing is that most of it is done at either a fairly steady pace or the changes (acceleration0 are done rather gradually (interms of our formula)............
What I mean by this is that even if one did constant acceleration over 30 feet but only went up 2 mph, there is not much affect on the over all penalty.
Actuall acceleration, minus deceleration is not all that great relative to what most riders think. Especially if considers over an entire cross country course instead of one single difficult section of one climb. Remember also that the speeds involved in the climb are slow and as such the accelerations are minimal..........most of what you are experiening is just the difficulty of normal climbing and not acceleration.