I am driving a Yamaha fj1100 with Kenna sidecar,Unit front fork,165x15 rear wheel and 16" motorcycle front wheel .In hard lft turns the frontwheel chatters(jumps,skids) outwards.Would a cartype front tire
improver handling noticably?Could it relate to springs or dampers?
Ther is relatively little weight on front wheel( 230 lbs).Any comment would be appreciated.Thanks
Gary
Gary,
If you are still using a sports type front tire on the bik, it may be a case of too small of a footprint.
I have had a similar effect with a FXLR Harley/Sputnik rig with a springer front end and a 70/90x21" front tire. Also with a V65 Magna/URAL rig with a narrow front Metzeler tire. I don't remember the tire size on the Magna but any amount of throttle would drag it sideways in an agressive left turn.
Perhaps a flatter tread (K block?)tire might be tried before going to the expense of converting to an auto rim/tire setup.
Just a thought,
Lonnie Cook
Northwest Sidecars
(Now in Boise, ID)
I agree with Lonnie on this one, but would add that an automobile style front tire might not be the answer.
When my rig was first set up, I had the same tires on all three wheels and agressive left turns would find the front end slipping - especially in wet weather. With a telescopic fork the contact patch of the front tire got radically smaller the sharper the turn.
First mod was to ditch the large front tire and go to a motorcycle tire (designed for the rear of a solo bike) and that contact patch didn't shrink so much, but the bike really just wanted to go straight.
The final mod was to replace the telecsopic front end with a leading link and a smaller auto type wheel. Now it steers like a dream and the contact patch doesn't change much on turns.
YMMV!
I've experienced similar slippage on my Honda GL650/Dneper. I tried reducing the trail which helped steering in general, but not the chatter in the lefties. I still have the motorcycle rim, so I tried a Dual Sport Bridgestone tire. Not much better, except on snow. Now I have a cheap Cheng Shin on the front and it's no better or worse. The only thing that really had any effect on the left hand turns was when I moved my 20 pound tool box from behind the sidecar seat to the sidecar frame between the sidecar body and the motorcycle. My sidecar wheel has 15 inches of lead so the toolbox was outside of the tipping line between the rear wheel and the sidecar wheel. Now my weight is distributed better and if I pull myself up towards the gas tank just before the turn, I can break traction on the rear and steer with the throttle on dirt and snow.
Much has to do with the tires as related to trail and the camber changes that come when steering input is made. Much also has to do with weight distribution and traction , or lack therof, when under acceleration. Mark's rig has an exceptional amount of wheel lead at 15". This will add stability in left handers as far as keeping the rear wheel down but it will also increase the chance of understeer in some cases. What works for one may or may not work for another in trying to keep the front end hooked up.
If the tire 'chatters' and does not Break traction gracefully more air pressuRe may be one solution. Yes, this may do noting to help traction but if it makes the transition into undesteer smoother it may be a more controllable situation. Learning to ride with a controlled understeer can be tricky as there is a fine line between being in control and havingto back off totally to regain control. With a lot of lead one can many times 'induce' oversteer going into a turn but this technique can also get you on your head if you are not careful and your rig is not up to it.
My newly set up K100/motorvtion FII rig has about 2" lead. also a Unit LL front fork with a 4.00 X 18 Block K tire on the front, and a 165/80 X 15" car tire on the rear.
It is very steady and level on turns...left or right, with no tire plowing or sliding at all. even with a passenger.
