Topic: Front end a bit bouncy CB550

[prov431]

I've got new Avon Road Riders in stock size on my bike and I feel they are quite grippy and confidence inspiring, however I'm not sure if I have a front tire or front wheel issue; I'm getting a bit of bounce in the front at different speeds. I had the wheel trued and static balanced - didn't seem to get it (and I'm going to have it done again as I can see a little movement in it while driving) I pulled the fork caps and checked the oil in the forks...got oil. There are also new progressive springs in the tubes. Not sure what else to check...I tried 30 psi and 25 psi and the rotation is correct, steering bearing are new tapered and there isn't any play - any ideas?

[Retro Rocket]

Your tire pressure is a bit low, try 32PSI to 36PSI in the front and see if that makes an improvement. What is the recommended tire pressure for your tires..?  Its on the sidewall...  If you've just put new springs in the forks what weight fork oil are you using..?

[Stev-o]

I agree with Mick, pump em up. And do you have enough oil in the forks?

[prov431]

Well coming from sport bikes and past club racing, I've always run my tire pressures low(er) than what any manual states (typical) - so perhaps this is an issue - I've never had a tube tire with the exception of bicycles.
The Honda service manual states to run 25 psi which when initially read it was fairly suprised - but then again that was for the stock tire back in 1976.
The fork has I believe 30w oil in it..which would be in agreement with the manual. The fork has smooth travel which is why I don't think it's the fork.

So my question is this - what kind of tire pressure are you guys running / recommending on the CB550's with new age rubber?
I will look at the tire sidewall in the morning and see what the max is - but I'm not planning on putting it up that high.

[mono]

this was (and is) my exact same experience after putting Avons on my 550 last spring!  been chasing the dragon on it.  a good suggestion from someone was to deflate/reinflate the front tire in case there was a slightly pinched/misaligned tube.  i did this (a few times) and it seemed to help a bit, although it may be psychological.  My "bounce" comes at betweeen 35-40 MPH -- you?

[scottly]

Bouncing at speed, on a smooth road, is usually related to:
1. wheel is out of balance
2. Wheel is out of true
3. loose spokes: the wheel is statically balanced and true, but with weight on the axle, the wheel becomes out of true in a radial direction, and also out of balance.

[Retro Rocket]

Well coming from sport bikes and past club racing, I've always run my tire pressures low(er) than what any manual states (typical) - so perhaps this is an issue - I've never had a tube tire with the exception of bicycles.
The Honda service manual states to run 25 psi which when initially read it was fairly suprised - but then again that was for the stock tire back in 1976.
The fork has I believe 30w oil in it..which would be in agreement with the manual. The fork has smooth travel which is why I don't think it's the fork.

So my question is this - what kind of tire pressure are you guys running / recommending on the CB550's with new age rubber?
I will look at the tire sidewall in the morning and see what the max is - but I'm not planning on putting it up that high.

The pressure on the tire is the MINIMUM, not the maximum {unless stated either way}, if you carry more weight then add more air, if you have raced you should know this..?  When racing you ALWAYS go down slightly more on the rear than the front, the rear always gets hotter,  on the street the tires never reach racing temps, hence the different compounds..

Bouncing at speed, on a smooth road, is usually related to:
1. wheel is out of balance
2. Wheel is out of true
3. loose spokes: the wheel is statically balanced and true, but with weight on the axle, the wheel becomes out of true in a radial direction, and also out of balance.

Also check that the tire is beaded equally all the way round the rim, if uneven  it can produce a bounce or up and down feeling when riding...  I use slightly heavier oil in the forks, stock is never thick enough for me and since there is no rebound adjustment on these bikes, heavier oil slows down the rebound...

[prov431]

Yes, 35-45 mph. I just had the wheel trued - and static balanced. I ended up yanking the 1/4 ounce of weights that the guy put on to see if that helped. I spoke to the guy who trued it and he said it was spot on, but offered for me to take it back to him and re-check.
I wonder if perhaps when he mounted the tire back on there was a dot on the tire that was supposed to be lined up with the valve stem and he missed it.....it's definitely in the tire or wheel though, everything else is new & tight....and there was a notable difference before & after he true / balanced it.
I will check the bead to see if perhaps it's not seated perfectly - other than that I think I'll have to take it back to the guy and watch him true it and balance again.

[scottly]

With the wheel off the ground, "ring" the spokes with a small wrench, and see if they produce the same pitch.

[prov431]

I plan on checking the spokes, although like I said earlier the wheel was just trued...so the spokes better be right!

[crazypj]

  Its on the sidewall... 

 THAT IS MAX PRESSURE FOR MAX LOAD - Not the recommended pressure so don't use it
Modern tyres usually require slightly higher pressures, 32~36.
Check tyre is 'beaded' properly, I haven't had any issues with the AVON's I've fitted although the AM21 race tyres are reall 'stiff' to bead out
30wt is WAYYYYYY  too heavy for fork oil, it just makes the fork pack down, 10~12wt would be about right even with stiffer springs
 Instability around 35~40 is pretty common on 70's bikes, forget reasoning, Tony Foal (plus others) wrote several articles about it, BMW had a video showing weave @37~38 mph

[Retro Rocket]

  Its on the sidewall... 

 THAT IS MAX PRESSURE FOR MAX LOAD - Not the recommended pressure so don't use it
Modern tyres usually require slightly higher pressures, 32~36.
Check tyre is 'beaded' properly, I haven't had any issues with the AVON's I've fitted although the AM21 race tyres are reall 'stiff' to bead out
30wt is WAYYYYYY  too heavy for fork oil, it just makes the fork pack down, 10~12wt would be about right even with stiffer springs
 Instability around 35~40 is pretty common on 70's bikes, forget reasoning, Tony Foal (plus others) wrote several articles about it, BMW had a video showing weave @37~38 mph

Sorry, i have car tires here mixed up with Bike tires, most if not all bike tires have a maximum load rating with a pressure of 42psi, that is the maximum pressure that the bike tire can take, and thats fully loaded, in Aus we have "recommended"tire pressures on our car tires and it is the minimum you should run...  Generally with stiffer springs you should run "slightly" thicker oil as the rebound force is increased or faster, the thicker oil slows the rebound effect equaling everything out, thats the simplified version....

[becken]

http://www.avonmoto.com/fitment-results

Avon website recommends 33 front, 39 rear. Might be a good place to start.

[crazypj]

Sorry, i have car tires here mixed up with Bike tires, most if not all bike tires have a maximum load rating with a pressure of 42psi, that is the maximum pressure that the bike tire can take, and thats fully loaded, in Aus we have "recommended"tire pressures on our car tires and it is the minimum you should run... 

Did not know that.
Can you get a ticket for running less than minimum pressure on car? (I think you can in Britain, vehicle in unsafe condition?)
USA doesn't have minimum pressures on tyres (I just checked)

[Retro Rocket]

Sorry, i have car tires here mixed up with Bike tires, most if not all bike tires have a maximum load rating with a pressure of 42psi, that is the maximum pressure that the bike tire can take, and thats fully loaded, in Aus we have "recommended"tire pressures on our car tires and it is the minimum you should run... 

Did not know that.
Can you get a ticket for running less than minimum pressure on car? (I think you can in Britain, vehicle in unsafe condition?)
USA doesn't have minimum pressures on tyres (I just checked)

You probably could if it was visibly obvious and deemed dangerous but i have never heard of it here.

[bjbuchanan]

It is pathetic what will pass as 'safe' in the US. I'm sure you are familiar with our 'parking' err I mean driving licenses. As long as DMV gets that registration money hit the open road.

Put a little more air in those tires. I know it has been mentioned but what about toying with fork oils. Also maybe the springs in there are shot. Too heavy of weight and it will be stiff and bouncy

[prov431]

http://www.avonmoto.com/fitment-results

Avon website recommends 33 front, 39 rear. Might be a good place to start.

Thanks for the link - I went to the Avon site but couldn't locate that!
I put 38 F/R and took it for a spin - that made an improvement, to the point where I think I might just live with it rather than pulling everything back off. I think I expect too much from this old bike.

[Stev-o]

No, your not expecting too much from your old bike. I have fairly new Bridgestone BT45's and it is very smooth.  Something is wrong.

[Blackhole]

Make sure you don't have a nut on your valve stem on the inside of the rim by the tube....should only have the cone washer there.  Been there done that and it did just what you are describing. Good luck

[scottly]

No, your not expecting too much from your old bike. I have fairly new Bridgestone BT45's and it is very smooth.  Something is wrong.

1+

[prov431]

Make sure you don't have a nut on your valve stem on the inside of the rim by the tube....should only have the cone washer there.  Been there done that and it did just what you are describing. Good luck

I don't recall seeing the nut at the base of the valve stem, however I do have a hefty Dime City Cycles "piston" valve stem cap on there......might as well pull that off and see if there's a difference.
I forgot to mention, I did verify the bead seat lines are equal all the way around on both sides of the tire and the stamped max cold psi for these tires is 42 psi.

[bwaller]

I've heard about tire pressures increasing with some of the new tires available. Just for the info I race with an Avon AM26 front. It's a different compound but I run +-28psi in the dry. The thing to watch for is that it doesn't build more than 10% pressure when fully up to temp.

But that's a long way from 42psi. I think I'd start mid 30's and work up.

If the tire is seated correctly having a big lump on the stem may well be your issue. Let us know, because I agree, the wheel needs to be dead smooth up front.

[becken]

http://www.avonmoto.com/fitment-results

Avon website recommends 33 front, 39 rear. Might be a good place to start.

Thanks for the link - I went to the Avon site but couldn't locate that!
I put 38 F/R and took it for a spin - that made an improvement, to the point where I think I might just live with it rather than pulling everything back off. I think I expect too much from this old bike.

Go to http://www.avonmoto.com and use the tire fitment guide. If you haven't changed the fork oil yet, you may want to try that also. The oil, especially non-synthetic, will break down over time. A friend with a Z-1 back in the day was having some weird problems and I checked the front and rear suspension and the steering and only noticed not much damping in the front forks. He changed the fork oil and cured all his problems.

[crazypj]

Eve when static balance is correct, when the fork oil is too thick the suspension pretty much stops working so the tyre has to do all the work.
As it compresses and rebounds where it meets the road it can set up a resonance which causes instability.
You may be able to find the info on Continental Tyres website (European, not USA)

[prov431]

I took the whole bike back to the guy who trued the front wheel - he took the wheel off the bike, removed the rubber and tube and put it back in the trueing stand. It was out pretty good. I watched him do the entiire process - he stated that when he did it the first time he believes the pin didn't seat on the wheel bearing for the true stand - so it wasn't straight in the stand.
I also watched him static balance it....perfectly.
So, the end result is, I still have a small bounce in the front end, no where near what it was...but it's still there. I'm running 30 psi. I suppose the only thing left is to drain the fork oil (which looked like motor oil, honey brown in color) when I checked the tubes the other day. Does anyone think the fork oil is my issue now that I'm positive the wheel is tracking straight? What are you guys using in the fork and what are you using to flush out the old stuff?
BTW- I have new progressive springs installed and the rubber is new Avon Road Rider - 100/90/19 Front and 110/90/18 Rear
Thanks for the replies!