Shake Twist or Fold?

[johno74]

Got a problem with my newly built vf750 trike, original frame loop at front with custom swingarm to accomodate reliant axle on back sprung with two bike shocks.

Fine on flat road, problems arise when the road surface has lots of shallow dips in it, so that the back wheels are at different heights to each other ie left back high, right back low then left back low right back high over and over again in quick succesion, which gives a pogo like effect.

Because its solid axle it cant absorb these undulations very well so this pogo effect is transferred to the telescopic front end as steering shake.

Do i want to increase the rigidity of the chassis or fit leading link or just move to Holland?


cheers

[growl bunnie]

move to holland :D

[Yoda]

what pressure are you running your back tyres at

[v8_trike]

Like Yoda says, tyre pressures are a good start, also fit a steering damper.

[johno74]

20 psi backs
Front is 30psi
Hows that sound?

[Yoda]

20 psi backs
Front is 30psi
Hows that sound?
what size tyres?
i would say between 12 and 20 psi depending on weight

[johno74]

195 50 17's
230kg

[growl bunnie]

too lower profile tyres to run at low pressure, go to a taller profile 65 + and run at 8 / 12 psi

[Yoda]

too lower profile tyres to run at low pressure, go to a taller profile 65 + and run at 8 / 12 psi
yep what he said, or can you get a slighty smaller rim with a higher profile tyre
i run my 445x50x15s at 8psi

[johno74]

ok thanks i will try that but what about the front tyre pressure?
ta

[Yoda]

ok thanks i will try that but what about the front tyre pressure?
ta
i would start off at 12 psi on the back, leave the front as it would be on the bike, see how much the handling changes
then just increase it by 2 psi at a time and at least this doesnt solve your problem then you have rulled this out

also how stiff is the suspension on the back end?

[johno74]

Hi Yoda,

Rear suspension is quite stiff, compresses when i sit on it but cant easily press the back end down. Were you thinking that it should be quite soft?

ta

[Yoda]

i am not an expert in this area, and can only go by problems i have experienced on my trikes
But i would say that being a bit softer might absorb more than it transfers

BUT try the tyres first as running them at lower pressure may give you the same result