Climbing and bb height, low gears

[Andrei Petrov]

I confess that wet, imperfect tarmac over 10% steep is still a challenge. I run 28 mm tyres (true size 29 mm) on the Silvio 2.0 at 60 psi front, and have tried both spinning and mashing - but both eventually result in wheelspin. Mashing is better, but is much more work)

This actually limits my biking range considerably. Other than gaining more cruzbike-specific power in the legs for more mashing, I was wondering whether bottom bracket height might have an effect on front wheel traction. At the moment I am set up with a 150 mm chain stay extension, which gives me a boom nearly parallel to the ground. This was the only extension at the time of my order. I am planning to try out a 100 mm extension by the end of summer, too, but have not got my hands on it yet.

Does anyone have any first-hand experience whether reduced bb height improves front wheel traction?

Any other suggestions on how to improve climbing/traction? Yes, I have read the forums)

I wonder if a loaded frame bag in the front triangle would make a noticeable difference.

In my case, lack of traction makes lower gears pretty much unusable on tarmac. I run 11-36 cassette with 52-39-30 triple, and only really used the lower 4 gears when I was learning to ride, on a grass field with some incline. To the few champions of triple rings out there, how useful do you find them on your rides?

 

[LMT]

imo I think a 10% hill which is wet would result in most riders (myself included) having a few issues with wheel slipping.

For me your front tyre needs pumping up, 60psi is too soft, whilst I appreciate it would give better traction the increased power needed would outweigh this I think. Have you run the tyre at 100psi?

 

[MrSteve]

Keep your baggage low and centralized. An under seat bag would be best.

Mounting a loaded bag in the front triangle would give you some handling headaches, dealing
with both the heavier, slower handling and with side winds.

My triple front rings are useful. I learned to use them well: your bike will teach you to spin smooth circles and make
smooth power.

I'm sorry, LeeTaylor55, but you're mistaken.
A bigger contact patch, a larger footprint, will help to minise slip.
When the tire is softer, less inflated, it will conform more easily to the road surface.
Bike tires are little and the difference can be small but it is there and every little bit helps.
A large soft tire will probably have better grip uphill than a little high-pressure racing slick would.

Sitting upright in your seat will put more of your weight over the front drive wheel and
will also help your balance at slower speed.
Try this... it works.

The height of the bottom bracket is pretty much a personal thing.
If it works for you, then fine.
If not, try something else.
B.. height, by itself, has very little to do with front wheel traction uphill.

Hope this helps,

-Steve

 

[LMT]

Keep your baggage low and centralized. An under seat bag would be best.

Mounting a loaded bag in the front triangle would give you some handling headaches, dealing
with both the heavier, slower handling and with side winds.

My triple front rings are useful. I learned to use them well: your bike will teach you to spin smooth circles and make
smooth power.

I'm sorry, LeeTaylor55, but you're mistaken.
A bigger contact patch, a larger footprint, will help to minise slip.
When the tire is softer, less inflated, it will conform more easily to the road surface.
Bike tires are little and the difference can be small but it is there and every little bit helps.
A large soft tire will probably have better grip uphill than a little high-pressure racing slick would.

Sitting upright in your seat will put more of your weight over the front drive wheel and
will also help your balance at slower speed.
Try this... it works.

The height of the bottom bracket is pretty much a personal thing.
If it works for you, then fine.
If not, try something else.
B.. height, by itself, has very little to do with front wheel traction uphill.

Hope this helps,

-Steve

I'm not mistaken at all, please read again what I posted.

The point I was making was the trade off in the increase in power needed to push what is imo an under inflated tyre compared to one that is inflated to 100psi, hence my question to the OP about pumping up the tyre. I want to see know how this compares against the potential extra slippage from the tyre to the power needed to drive the bike.

 

[MrSteve]

I see.
There are trade-offs and compromises.

 

[ratz]

Let's see.... issue at play which I can see you understand but for newbies' passing by.

• Power-to-Weight Ratio versus Torque and Traction at Grade is all that maters.
• Little gears give more leverage, impart more Power as Torque to the contact patch
• If you break the surface tension of the tire you slip.
• Recumbent have the weight biased to the rear wheel when going up hill.

Only fixes

• Pedal Slower
• Use a bigger gear
• Sit up more
• Loose total weight engine or bike
  
• stickier tire compounds

Adding weight to the nose would pose other issues. Low slung weight at the butt region will help but that's also relative to the steepness of the grade; the steeper the grade the less it helps. The lower BB will only help with the Pedal Slower; Use a bigger gear if it allows you to situp more and generate more power that's an individual thing. I would help me, but there are the aero trade offs

 

[RojoRacing]

I don't get wet roads too often but 10% is an easy climb in my area, I often get above 15%. Traction is going to come down to power applied. Given certain conditions your only going to be able to apply so much power(watts) to the ground before breaking traction. If that number is 150 watts then you need to keep it under 150. On steep climbs you get tired and start to pedal is not so perfect circles so there are high and low spots in your applied power. If you avg power per revolution is 120 watts but your peak power is 170 then your going to spin the tire. If your average power is 140 with a peak power of 145 then your going to smoothly get up the hill and faster to boot.

Your mentality going into a climb where your concerned about traction is important. If you rush your mind you rush your body and things become less fluid.

Aside from adding more weight which I think would hurt you more with fatigue then help with traction in the long run. You need to focus on what'll take to keep smooth constant power. For most riders it's short enough gearing that they don't tire and struggle to pedal smoothly. Some riders will attack leading into a steep section at say 400 watts then try and maintain 200 and further reduce as they continue along at what they feel is the limit of traction as they continue to drop in speed hoping to reach the top before they stall. As always the stronger you are the faster you can climb and the faster your climbing the higher that traction power value is.


My advice is read what I wrote then reflect on your climbing technique. I suspect refining your technique along with maybe a different choose in gearing will get you the best results. Sadly there is always going to be a great limit on a wet climb with a Cruzbike then others so you have to maximize what you can do and pick your battles wisely.

 

[SamP]

Pedal smoother. Variations in force applied mean at some points you're applying more force than others, the high force spots in your pedaling stroke are where you are most likely to overcome static friction and cause wheel slippage.

 

[Andrei Petrov]

Good points. The reason I brought up bb height is that with my current set up the power stroke is directed forward. With the lower bb, it would be angled towards the ground, and will result in additional force applied downward on the front end.

Yes, I started at higher pressures with 90 psi. I am riding a fairly wide, supple and soft Hutchinson Secteur 28, which on my rims actually measuruse 29 mm, tubeless. 90 was an overkill, 60-70 psi front/rear are my preference.

Wet and gravel on the road make a world of difference for climbing traction, that's what I am trying to solve for.

 

[ratz]

Good points. The reason I brought up bb height is that with my current set up the power stroke is directed forward. With the lower bb, it would be angled towards the ground, and will result in additional force applied downward on the front end.

Yes, I started at higher presdures 90 psi. I am riding a fairly wide, supple and soft Hurchinson Secteur 28, which on my rims actually measuruse 29 mm, tubeless. 90 was an overkill, 60-70 psi front/rear are my preference.

Wet and gravel on road make a world of difference for climbing traction, that's what I am trying to solve for.

One thing that slipped my mind; I get better up hill traction on the Vendetta than I did on the Silvio with the shock. Try testing both higher and lower pressure in the fork shock an see if that has any effect on your traction.

 

[MrSteve]

The big reason the Vendetta goes up hills more efficiently than the Silvio is
that the wheelbase of the V is longer than the wheelbase of the S.
I'd explain why, but I trust your brain!

 

[ratz]

The big reason the Vendetta goes up hills more efficiently than the Silvio is
that the wheelbase of the V is longer than the wheelbase of the S.
I'd explain why, but I trust your brain!

Man ..... now I have to go look that up. I bet it will be fascinating though, math nerd is ashamed not to know that one off the top of my head.

 

[ccf]

I think it is the lower CG of the Vendetta that produces better traction. Longer wheelbase makes it easier to have a lower CG.

-Cliff

 

[ccooper]

The big reason the Vendetta goes up hills more efficiently than the Silvio is
that the wheelbase of the V is longer than the wheelbase of the S.
I'd explain why, but I trust your brain!

Here is what my brain determines is a reasonable explanation.
The distance of the rider's center of mass from the front wheel is approximately the same in both bikes, and is determined by the front triangle plus leg length. But if the wheelbase of the V is longer, then the front/rear distribution of weight is heavier in the front compared to the S, given the same rider. More weight on the front means more traction, and less slippage.

To make this easier to visualize, imagine Bike #1 with a wheelbase of 100 meters, and Bike #2 with a wheelbase of 1 meter, both MBB/FWD. Bike #1 has nearly all of the weight in the front, where Bike #2 is more evenly distributed front/rear. Bike #1 will have better traction going uphill, all else being equal.

 

[ccf]

My understanding is that both bikes have a 50-50 weight distribution (depends a bit on the rider). If that's true, then it is the difference in the height of the CG that produces better climbing traction for the Vendetta.

 

[super slim]

Good points. The reason I brought up bb height is that with my current set up the power stroke is directed forward. With the lower bb, it would be angled towards the ground, and will result in additional force applied downward on the front end.

Yes, I started at higher pressures with 90 psi. I am riding a fairly wide, supple and soft Hutchinson Secteur 28, which on my rims actually measuruse 29 mm, tubeless. 90 was an overkill, 60-70 psi front/rear are my preference.

Wet and gravel on the road make a world of difference for climbing traction, that's what I am trying to solve for.

if you weigh 80 kgs then, with a 50% F/R wheel loading of the Silvio or Vendetta, a 28 mm tyre should have 70 psi in the Front or rear
http://www.adventurecycling.org/default/assets/resources/200903_PSIRX_Heine.pdf

 

[RojoRacing]

Really you guys are missing the simplest solution to this problem. All you need to do is convert to fixed gear and ride uphill backwards.

 

[Rick Youngblood]

The big reason the Vendetta goes up hills more efficiently than the Silvio is
that the wheelbase of the V is longer than the wheelbase of the S.
I'd explain why, but I trust your brain!

This was one of the first notable differences I found between the the S and V. The rear wheel is further behind your body weight, placing more weight towards front drive wheel vs the rear wheel, thus more traction, like leverage.

 

[RojoRacing]

This was one of the first notable differences I found between the the S and V. The rear wheel is further behind your body weight, placing more weight towards front drive wheel vs the rear wheel, thus more traction, like leverage.

But with the 20 deg seat angle our big head will follow the rear wheel in its extention so you gain negligible front wheel weight bias.

 

[RAR]

This was one of the first notable differences I found between the the S and V. The rear wheel is further behind your body weight, placing more weight towards front drive wheel vs the rear wheel, thus more traction, like leverage.

Rick, Have you actually weighed front and rear of both to verify the difference ?
My Silvio with me on it is 92 lbs. front and 98 lbs. rear. About 49% F 51% R