ThermionicScott 

Please explain how any of those things help. Shilling for companies selling bikes doesn't count.

Rolla

"The shorter the stays the closer the rear wheel's contact patch will be to your center of gravity. This increases traction when you need it most – when climbing and in conditions with poor traction – snow, mud, sand, and loose gravel."

https://www.sevencycles.com/chainstay-philosophy.php (no affiliation)

ThermionicScott 

From what I can tell of the OP's bikes, they don't have excessively-long chainstays. So I don't know how any of Calsun's post is actionable for him. He doesn't need to buy ****, he just needs to climb more hills.

Rolla

I don't know anything about the OP's bike; I was just pointing out that Calsun's statement about shorter stays helping climbing is generally accepted as true, especially on the "mainly loose dirt/gravel" that the OP rides. Likewise the tubeless tires suggestion.

Not sure why you accused Calsun of "shilling," but you seem to be in a mood so I'll leave you to it.

ThermionicScott 

It's not a bad mood per se , we just seem to be straying further into things that are so marginal that they could become distractions from the goal. People can climb just fine with long chainstays and tubes in their tires; that's not what's holding the OP back.

But there is always the chance that throwing money at the problem could make the experience a little better, and inspire him to ride more, so I will end my protests here.

ColonelSanders

I wish it could be quantified how much more energy it takes, because when left unspecified, I suspect most people assume a greater amount of extra energy is needed, than the actual amount for a given weight.

Rolla

Agreed. I'm sure it's one of those "forum phenomena" where the effect is both hugely significant and utterly undetectable.

unterhausen

This is one of those battles that was fought viciously for years on the usenet news group rec.bicycles.tech and I imagine you can go find some evidence of that in the archives. It would also submit to sophomore-level engineering dynamics calculations. Which may be taught in high school physics nowadays, I'm not sure.

Fentuz

@OP, you stated that your other bike is much faster with lighter wheels and groupset etc... but, you did not mention the tyres. Have you try a better tyre on the gravel bike?

I rode last summer and autumn on G-One ***** and Ultra ***** (I mean Bite and Ultra Bite) and they were slow and horrible, going up hill was not pleasant (but good to improve fitness)... I swapped back to conti RaceKing and CrossKing and they are much faster; on the fitness/test loop (20k) I am 5 to 10 minutes faster and I can climb the same hills on 1 or 2 cogs harder.
When checking the rolling resistance on the website with a similar name, the G-One were about 30-33W and Race King was about 19-22W. ~33% less rolling resistance which you can feel.

May be check your tyres there: https://www.bicyclerollingresistance.com/ and see if you could find something with less resistance which will help up hill.

Fentuz

That was the story of my short racing period...

Fentuz

That's not easy to quantify as a general statement because you don't know all the variable. You would need to calculate kinetic and potential energy which is doable but dependant of the weight variations and distributions but you also have to consider the gearing because they impact the torque/moment and the level of frictions... like i said, can be calculated but not easy to get all the data.

I can tell you that when I was racing (same car, same tyres, same circuits, similar conditions), you could feel the difference between a standard flywheel and a "ultralight" flywheel and same went for std alloy rim vs light forged rims... but, the kinetic gain happened mostly in 1st/2nd and 3rd gear. In 5th gear, it did not make much impact...
The advantage was off the line and coming out of a corner (especially hairpin) accelerating much much faster.

The same goes for bike however, I think that at the level we are talking about, the 90%, I cannot see 70g being very significant compared to rolling resistance...

jonathanf2

I'm running 32c tires on my other bike with GK semi-slicks. I use this bike mainly as my road bike but can occasionally handle hard pack dirt and paved fire roads. One thing I notice with my full carbon bike is that for seated road climbs, I can stay in the big front chainring longer without having to drop into the small front chainring. On out-of-saddle climbs I can stay in the big chainring and attack the hills without losing momentum. Muscle fatigue is noticeably less as well. On the single track climbs I do with my alloy gravel bike, I'm in my small/small the whole time due to the steepness of the trail. So I don't think rolling resistance will matter much on those trails which are predominately used by MTB'ers.

Also I mainly do climbing, in fact I'm not particularly fast on the flats! So it's not like I brought up this thread because of any deficiency in my "human" motor, I just want to explore options that might help improve my performance.

Badger6

I think I've suggested the best way to do that.

I have an SL7 (7kg) and a Mk1 Diverge (9.2kg), both geared almost identically (Diverge has an 11-34 cassette, the SL7 an 11-30, both driven by a 52/36 chainset), and the SL7 definitely "feels" easier to climb. But, Strava says the difference is strictly based on how many beers I've had the night before. Both have carbon hoops on, though the wheelset on the Diverge are a touch heavier with 32mm slick tires on, but the SL7 is wearing 30mm right now. My point is that the minimal differences in weight we are talking about are really not going to make it "easier" to climb. Gearing will do more for you in that respect. Even then, there are limits, lower gears might be easier to turn but could end up requiring more work (effort over time), and then you have to ask yourself "Was the climb actually easier?"

Bottom line: I don't think 650b is going to get you "easier" climbing.

jonathanf2

Thanks Badger, my carbon bike didn't seem noticeably better until I swapped to carbon hoops, so I'll probably do the same with my alloy GRX bike. Also I remember you've offered plenty of reasonable comments that haven't diverged too much off-topic! On a side note, awhile back I did start a thread about implementing an 11-42t cassette on my 2x GRX equipped bike. I have it tuned now to where shifting is smooth (comparable to my friend's Ultegra bike) and only needs a a slight barrel adjustment after a fairly bumpy ride. It's not within Shimano spec, but being able to ride fast on tarmac and still climb with MTB'ers has made my bike incredibly versatile.

Badger6

Thats great! I definitely tend to say, to that specific setup, "Don't do it." Only because that is pretty far out of spec, not specifically because it is "impossible." I'm glad you were able to get it tuned. As someone who rides pretty much only carbon hoops now (the only bike without them is my fatty, and it might eventually get them), changing from aluminum to carbon and proper climbing gears will definitely make climbing "easier."

That all said, 650b has it's place, really shining on the rougher stuff (in my experience), and as I stated above, because they just seem to spin up faster.

chas58

Jonathan, I guess you got your answer then.
My gravel bike climbs like a scalded cat, but it is light & stiff (in the right areas) - short chainstays, stiff BB, very efficient power delivery).

Most people putting 650b tires try to match the rolling diameter of a 700c wheel, so there is no effective difference (other than overall weight, and of course cush from lower PSI). You can lower you CG and gearing with 650b wheels and smaller tires, but that is going to change your geometry (and possibly take your bottom bracket lower than you want). And, if the overall diameter is getting too small, you will change the rollover characteristics of the tire (bigger tires have a shallower approach angle and roll smoother (ceteris paribus).

The MTB industry has struggled with this for years. 26" tires to 29" tires - that wasn't ideal initially, then down to 27.5" - now they have settled down on 29" tires because the bigger tires and wheels are faster when the going gets rough (once you can design a frame to handle the way you want it to with bigger tires).