Higher Tire Pressure = More Suspension Compliance?

[Huladog_imp]

Just wanted to run this by you guys to see if I'm nuts or not.

When the CB1100 suspension starts to feel harsh and jarring (and I start thinking of fiddling with the preload or worse, spending $ for replacement shocks) I remember to check the tire pressure.

Find out they're both maybe 5-6 pounds low, so I pump them back up to 36 front/42 rear and then the stock suspension seems relatively plush, compliant and composed again.

Seems sort of counter-intuitive if you ask me.

Higher (proper) tire pressure seems to make the ride compliant as if the road shocks are now able to be absorbed by the suspension as designed. Low tire pressure and the ride seems harsh like the road shocks don't get transmitted to the suspension although you would think the softer sidewalls would absorb road shocks.

Am I nuts?

On my previous BMW R1200RT it was sensitive to tire pressure and turn-in/handling definitely improved running higher that spec'd pressures. Before that my Street Glide needed proper tire pressure just to turn-in at all.

Just wondering if anyone else noticed something similar?

Aloha,
Huladog

[the Ferret]

Hmmm I've always felt the ride kind of stiff even though I have mine set on full soft front and rear. I was wondering if dropping a few pounds in the rear tire, especially since I never carry a passenger, might soften the ride even more. Guess not .

[CIP57_imp]

I was running 32 front 36 rear with the stock tires. They are rock hard. With my setting on one line showing on the front to decrease dive when braking. The rear set on standard 2 setting, three was much to harsh. This combo seemed to work well for me. Experiment with different setting until you feel the front reacts best with the rear.

With the new tires i have bumped up air pressure to 34/38.

[Pterodactyl_imp]

I guess it's very individual. Also riding style and road conditions affect how the suspension should be set. I have 2nd ring for the front, 4/5 for the rear (2nd hardest) and tyres at 36/42.

I think CIPs got it with:

I was running 32 front 36 rear with the stock tires. They are rock hard. With my setting on one line showing on the front to decrease dive when braking. The rear set on standard 2 setting, three was much to harsh. This combo seemed to work well for me. Experiment with different setting until you feel the front reacts best with the rear.

With the new tires i have bumped up air pressure to 34/38.

It's funny I have always regarded the CB as a soft ride. Softer (preload) front assists turn in so I go that way. I keep the tyre pressures up as I often ride loaded and some of our country roads have pot holes that would swallow a Mack truck. I hope that this will limit sidewall damage.

Cheers

[mininsx_imp]

The recommended tire pressure for a given motorcycle is so that you get the proper "footprint" from the tire and has nothing to do with suspension compliance. Personally, I think my 2013 CB is on the soft side, suspension-wise; I adjusted the front pre-load one full turn harder.

[the Ferret]

Funny thing about tire pressures

My ST calls for 42 front and 42 rear (whether single or double up)

My 750 Nighthawk called for 36 front and 36 rear .... unless carrying a passenger then 36 front and 42 rear

My FZ-1 called for 36 front and 39 rear (whether single or double up)

My Majesty calls for 29 front 36 rear (whether single or double up)

My Triumph T 100 called for 33 front and either 38 or 41 rear depending on the source... owners manual or service manual (whether single or double up)

The CB calls for 36 front 42 rear (whether single or double up)

My trailer calls for maximum 50 pounds when loaded for 1360 pounds. If I have 50 pounds in the tire and only load 500 pounds on it, it will bounce like a ball on every bump. so if I am hauling just 1 motorcycle I only run 45# per tire.

Yes I have a chart on the wall so it's easy reference when checking tires lol

Tire pressures are however "recommended" and the pressure can be safely varied within a few pounds or manufacturers wouldn't stamp "maximum pressure" into the sidewall which some people take as the "only" pressure they can use.

Tire pressure gauges can also vary...I have 3, an analog, a digital and a pencil gauge, that between them measure over a 3 pound range..one will measure 35, one 36 and one 37 pounds on the same tire measuring with one after the other.

Maybe on my CB I will put 42# in the rear but measure it with the low gauge

[AzBob_imp]

I was running 32 front 36 rear with the stock tires. They are rock hard. With my setting on one line showing on the front to decrease dive when braking. The rear set on standard 2 setting, three was much to harsh. This combo seemed to work well for me. Experiment with different setting until you feel the front reacts best with the rear.

With the new tires i have bumped up air pressure to 34/38.

Pre-load has no effect on compression damping (and therefore brake dive). If we had fully-adjustable forks up front, you'd want to up the compression damping to combat brake dive, but we don't, so all you're really doing is reducing your ride height and reducing your fork's range of travel. I'm not sure if we have progressive springs, but if we do, you may also be unnecessarily increasing the harshness of your ride by pushing the spring into the stiffer progressive rate sooner.

I run recommended tire pressures (36psi front), with front pre-load set for my weight (220+lbs w/gear, right at 2nd line) and experience very little brake dive.

[Pterodactyl_imp]

^^^^^. True, however I can't agree with

I was running 32 front 36 rear with the stock tires. They are rock hard. With my setting on one line showing on the front to decrease dive when braking. The rear set on standard 2 setting, three was much to harsh. This combo seemed to work well for me. Experiment with different setting until you feel the front reacts best with the rear.

With the new tires i have bumped up air pressure to 34/38.

Pre-load has no effect on compression damping (and therefore brake dive). If we had fully-adjustable forks up front, you'd want to up the compression damping to combat brake dive, but we don't, so all you're really doing is reducing your ride height and reducing your fork's range of travel. I'm not sure if we have progressive springs, but if we do, you may also be unnecessarily increasing the harshness of your ride by pushing the spring into the stiffer progressive rate sooner.

I run recommended tire pressures (36psi front), with front pre-load set for my weight (220+lbs w/gear, right at 2nd line) and experience very little brake dive.

Preload affects at what force spring compression will commence. This is also affected by the load that the bike carries. With a large pillion load the bikes rear suspension will operate at lighter (external) forces than unloaded. This will delay initial displacement but, as you say, after that damping forces become the only player. Therefore Honda (and others) recommend higher preload settings for heavier loads. I found that the bike tended to "wallow", particularly leaned over and going over small road irregularities. A bit over active. Upping the rear preload one notch has made an improvement. There are so many variables to suspension set up. Most are not available on the CB. Not needed really as it's damn good as is. Thanks for that Honda.

Cheers

[CIP57_imp]

^^^^^. True, however I can't agree with

I was running 32 front 36 rear with the stock tires. They are rock hard. With my setting on one line showing on the front to decrease dive when braking. The rear set on standard 2 setting, three was much to harsh. This combo seemed to work well for me. Experiment with different setting until you feel the front reacts best with the rear.

With the new tires i have bumped up air pressure to 34/38.

Pre-load has no effect on compression damping (and therefore brake dive). If we had fully-adjustable forks up front, you'd want to up the compression damping to combat brake dive, but we don't, so all you're really doing is reducing your ride height and reducing your fork's range of travel. I'm not sure if we have progressive springs, but if we do, you may also be unnecessarily increasing the harshness of your ride by pushing the spring into the stiffer progressive rate sooner.

I run recommended tire pressures (36psi front), with front pre-load set for my weight (220+lbs w/gear, right at 2nd line) and experience very little brake dive.

Preload affects at what force spring compression will commence. This is also affected by the load that the bike carries. With a large pillion load the bikes rear suspension will operate at lighter (external) forces than unloaded. This will delay initial displacement but, as you say, after that damping forces become the only player. Therefore Honda (and others) recommend higher preload settings for heavier loads. I found that the bike tended to "wallow", particularly leaned over and going over small road irregularities. A bit over active. Upping the rear preload one notch has made an improvement. There are so many variables to suspension set up. Most are not available on the CB. Not needed really as it's damn good as is. Thanks for that Honda.

Cheers

Preload affects at what force spring compression will commence. This is also affected by the load that the bike carries. With a large pillion load the bikes rear suspension will operate at lighter (external) forces than unloaded. This will delay initial displacement but, as you say, after that damping forces become the only player. Therefore Honda (and others) recommend higher preload settings for heavier loads. I found that the bike tended to "wallow", particularly leaned over and going over small road irregularities. A bit over active. Upping the rear preload one notch has made an improvement. There are so many variables to suspension set up. Most are not available on the CB. Not needed really as it's damn good as is. Thanks for that Honda.

Cheers Thank you p, you saved me trying to type on this iPhone

[Pterodactyl_imp]

^^^^^. No worries mate.

In addition I quote from Lee Parks: "For street riding it is very important not to stray too far from manufacture's recommended tyre pressures as tyres have been designed to provide the correct amount of contact patch and flexing at a given load and pressure". Parks knows a little bit more about motorbikes than I do so I think whatever he says is worth considering.