Gravel Roads

[denill]

Jackrat started a thread: http://www.kiwibiker.co.nz/forums/showthread.php?t=2836 on gravel roads which probably would be best in the road bike stuff.

There is some good advice there and let's face it, whether you like it or not, sooner or later we are required to ride on gravel. Even if only on road works.

[pete376403]

Your bike has three big gyroscopes that, if spinning fast enough, will do their best to keep the bike up (the crankshaft* and the wheels) so in theory, the fast you go the more stable the bike should be.

*(this doesn't apply to non-F650 BMW, Guzzis, Pan Europeans and other north-south crankshaft bikes)

[Cajun]

i lived on a gravel road, 2 kms of gravel before i could even get my drive way, and going backwards and forwards over it every day, the only time i ran in to problems was when they went over it with the grader which was like riding on marbles for a couple of days after that was nothing, i use to be able to 130+ on my gravel road. on a road bike

[wildfire1]

You are Soo right dude... gravel roads are normally O.k on most bikes (with a bigger than 16 inch front wheel). The only time I have had any real problems has been straight after the road has been re graded.
I learn't a valuable lesson from a very experienced rider once - in gravel, if in doubt - accelerate! (using common sense of course!) It changes the dynamic of the steering and gives you the ability to change your line on the fly.

[Cajun]

yeah and its great fun spinning the rear up on gravel feel the bike loose tracton and stuff.

[Kickaha]

Your bike has three big gyroscopes that, if spinning fast enough, will do their best to keep the bike up (the crankshaft* and the wheels) so in theory, the fast you go the more stable the bike should be.

*(this doesn't apply to non-F650 BMW, Guzzis, Pan Europeans and other north-south crankshaft bikes)

Didn't stop me seeing 140kmh on my R75/7 on a gravel road though,low centre of gravity and narrow wheels it was a good gravel road bike and the Darmah that followed wasn't bad either.

[merv]

Gyro effect should be there no matter what way the crankshaft is aligned as the basics of a gyro is all about inertia and resisting change.


Wildfire1 says "if in doubt accelerate" and that's about it, the trick on gravel is keeping up momentum and good throttle control and this relates to my comment on the other thread about this when I said on straight gravel roads I shift my weight back on the seat as the aim is too keep the front as light as possible so its less inclined to follow the ruts and gravel mounds. So yeah if you're digging in at the front give it some herbs to lift it out and help it go straighter.

[pete376403]

I wasn't saying you can't go fast in the loose on a BMW (Ask Hubert Auriol or Gaston Rahier about that ), just that the spinning crank isn't adding to the gyro effect of the wheels.
And for those who doubt his, hold up a wheel by the axle and get someone to spin it up - see how much effort it takes to shift it out of the plane it's rotating in. Consider how much greater the effect would be for a wheel turning at a good road speed, or a crankshaft turning many 1,000s of rpm.

[Motu]

As I mentioned in the other thread - the way to maintain control of the front is to loose control of the rear...if the rear wheel is spinning under power the front carries no weight,if the rear is sliding under braking the front is in control.This is the foundation of Kenny Roberts rule of ''you'll never loose the front if you are on the gas'' he learnt it on the dirt track and applied it to road racing.Watch a speedway race - that rear wheel is spinning the whole time,the skinny front wheel is never stressed at all,if the rear wheel hooks up they are in big trouble,no one gets on the gas earlier than a speedway rider.Hard to do,but if you loose the front,punch the gas.As others have mentioned speed is a key,go too slow and it's wobble and fight time.21in front wheels save the day.

[pete376403]

Gyro effect should be there no matter what way the crankshaft is aligned as the basics of a gyro is all about inertia and resisting change.

Hmmm - I never considered that.

[Kickaha]

Gyro effect should be there no matter what way the crankshaft is aligned as the basics of a gyro is all about inertia and resisting change.

But in something like the BMW or MotoGuzzi wouldn't you have effectively have two gyroscopic forces at 90 degrees to each other,the wheels being one and the crank being the other.

I think technique is the main thing to be able to ride confidently on a gravel road and every road bike I have owned has spent some time on them,I only ever worry about what way the front is pointing and don't worry to much about the back.

[DEATH_INC.]

Fast and smooth is the way to go.....and yep,spinning up the rear helps with turning for sure.sliding the rear in helps too.
I've had the ZX12 doing well over 200kph two up on the gravel no worries,but you have to remember it takes ages to slow down for corners,cows ect.....

[Wenier]

yea in blenheim they are some gravel bits i go over all around the place, our drive way the road to a mates(damn long) etc. i havent had a problem ridin along em at speed and of course u gotta play silly buggers and spin it up.

[phil_elvey]

I went up the the wind farm the other day (a tight, winding, hilly track with a mainly clay base) on the ZX with a pillion on the back. Good fun!

[denill]

Yeah, surface does make a big difference. Just as in a 'good' spedway track surface.

I reckon that I can ride gravel OK, but my bluff was called one day riding the inland route from Kaikoura to Hanmer. The road was freshly graded and the shingle was THICK, specialy where it wasn't wanted. ie. on the inside of l/h corners.

No matter what technique I used it, didn't work. Specially the - if in doubt, open out !!!
Talk about tank slappers.......

So I was reduced to just wobbling along at low speed, only partly in control.