Servi handling

Stiff and twitchy

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70 servi
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Servi handling

#1

Post by 70 servi »

I already know that servi's aren't built for speed or handling. Mine has 3 motorcycle tires with about 22# each. It is stiff and tippy and twitchy. I have read that 12# is recommended, but that just seems very low. I would like to know about anybody's experience with psi and tire differences like car tires (?)
To make any improvement, just in case I need to make a sudden, evasive maneuver without trashing this thing. Thanks in advance to the more seasoned professionals!
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Re: Servi handling

#2

Post by panhead_kicker »

70 servi wrote: Mon Aug 01, 2022 12:53 pm I already know that servi's aren't built for speed or handling. Mine has 3 motorcycle tires with about 22# each. It is stiff and tippy and twitchy. I have read that 12# is recommended, but that just seems very low. I would like to know about anybody's experience with psi and tire differences like car tires (?)
To make any improvement, just in case I need to make a sudden, evasive maneuver without trashing this thing. Thanks in advance to the more seasoned professionals!
It's just the nature of the beast. My 65 doesn't care to be sporty either. I have Avons on it, and run around 20 in them. 12 Does sound too low, but it boils down to what the tire manufacturer states are safe ranges, and what risk you're comfortable with. And I think you've already been advised that for handling and safety, the front fork on a servi is in a permanently raked position, similar to that of a side car equipped big twin of the era.
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Re: Servi handling

#3

Post by Pascal »

The WLA/ WLC was recommended with 1.8#...maybe it helps your Servi to be less bouncy..?
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Re: Servi handling

#4

Post by 70 servi »

I will try less psi, i was hoping to hear that somebody is running bias ply car tires on back, yes the fork is in the longer position, all good there, after finding the stem nut detached! I dont find the rig bouncy and when i can spend more miles riding than testing, i will get more tolerant of the handling.
No wonder we dont see any "Trike Races".
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Re: Servi handling

#5

Post by RUBONE »

Car tires work on trikes and sidecars because they never lean so there are not issues with sidewall flex, etc. Trikes are inherently bad handling beasts. they worked fine for meter maids at 10MPH but are really stressed at 50MPH on an open road. Low pressure in the front tire will make the handling even heavier. A functioning steering damper is a must.
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Re: Servi handling

#6

Post by panhead_kicker »

RUBONE wrote: Tue Aug 02, 2022 12:47 am Car tires work on trikes and sidecars because they never lean ...
Putting the square profiled Shinko on the back of my sidecar rig has made flying the car a bit trickier...
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Re: Servi handling

#7

Post by 70 servi »

Follow up: on my latest local test ride loop i ran 18# in all 3 tires. Much less oversteer, and handling is improved, and on my next drive, after gas tank lining and clutch repair, I will experiment more with the PSI.
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Re: Servi handling

#8

Post by kitabel »

Two choices for the fork (using OEM parts)
1. Fork stem not parallel to the tubes (permanent in G, adjustable in sidecar)
2. Everything else (stem and tubes parallel)

1. Reduces steering effort by shortening trail, which is the self-centering characteristic. Result is less stability at speed, like a shopping cart.
2. Require more shoulder muscles to operate but more stable at cruising speed.

Raking the neck increases both stem angle and trail, steering becomes very heavy, very large turning circle.

A combination of a raked neck plus raked trees can give close to normal handling with severe fork angle.
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Re: Servi handling

#9

Post by Mark44 »

Pascal wrote: Mon Aug 01, 2022 4:16 pm The WLA/ WLC was recommended with 1.8#...maybe it helps your Servi to be less bouncy..?
Typo? Surely you didn't mean 1.8 PSI...
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Re: Servi handling

#10

Post by RooDog »

Mark44 wrote: Mon Aug 29, 2022 5:46 pm
Pascal wrote: Mon Aug 01, 2022 4:16 pm The WLA/ WLC was recommended with 1.8#...maybe it helps your Servi to be less bouncy..?
Typo? Surely you didn't mean 1.8 PSI...
1.8 Bar?
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Re: Servi handling

#11

Post by Buster »

I run around 22 lbs in rear and whatever the tire calls for in front. Now running 36lbs in front on modern Dunlap.
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Re: Servi handling

#12

Post by Buster »

Also, are you are running a steering dampner .
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Re: Servi handling

#13

Post by kitabel »

A certain minimum psi is needed in the rear tires to combat wear, oversteer and high temperature, but since the entire chassis is unsprung (rigidly mounted to the axle) any bump at all throws the axle up in the air, and you with it. Use the lowest safe pressure.
In addition, the higher the psi in the rear the worse a single-wheel bump, which makes the bike dart to one side, in extreme cases it will try to change lanes.
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Re: Servi handling

#14

Post by 70 servi »

Thanks Buster and Kitabel for any and all info, the steering damper is in place and so far I havent needed to turn it downward. My original concern, while having too much psi at that time, was the firmness of the ride especially while in a turn, which is improved with less psi. I believe the manual says to use 12#, which just seems wierd to me but then again so does the 18# i am running. It will be a while before I take another ride on my usual test loop, which is hilly and curvy.
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Re: Servi handling

#15

Post by RUBONE »

70 servi wrote: Tue Aug 30, 2022 10:22 pm Thanks Buster and Kitabel for any and all info, the steering damper is in place and so far I havent needed to turn it downward. My original concern, while having too much psi at that time, was the firmness of the ride especially while in a turn, which is improved with less psi. I believe the manual says to use 12#, which just seems wierd to me but then again so does the 18# i am running. It will be a while before I take another ride on my usual test loop, which is hilly and curvy.
Be aware that the 12psi is for old style rayon cord tires in use at the time, which had very stiff sidewalls. Nothing at all like modern production tires. Get modern ones soft enough and they will fail when in a most inopportune time, like the middle of a turn.
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