Wandering steering

Chat about anything to do with sidecars and outfits. NOT BMW specific - all welcome

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stevedowling1
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Wandering steering

Postby stevedowling1 » Sat Jan 17, 2015 5:54 pm

I'm currently restoring a K100RS and Hedingham SS outfit. It is now on the road and I'm fettling some poor running issues before getting it resprayed. The problem is the handling. I have had several sidecar outfits over many years both with and without leading link forks (Unit and Wasp) but not with 15 inch wheels and car tyres as fitted to this outfit but I haven't experienced handling quite like this. it feels very uncertain (twitchy) at the front end and is easily deflected from the path I've chosen by the smallest irregularity in the road surface. The front forks are Wasp which, from previous experience, tend to give light steering but over 60mph this outfit doesn't inspire confidence. In strong cross winds I have to really hang on to keep it straight. I'm reasonably sure this is not an alignment issue. I replaced the subframe with an identical one from Wasp. The original was damaged. I have renewed the sidecar suspension bearings and damper. The rear shock on the Bike is Hagon for sidecar duty. I have an as new steering damper (hydraulic) fitted though the steering feels like I haven't! I have a standard BMW front wheel which I may try for comparison but I would be interested to hear views from others with a similar set up.
Thanks
Steve
Regards
Steve

1994 R100RT with Monza Sidecar
1995 MZ 250cc Saxon Tour (nice little runabout)
1970 MZ 250cc Supa Five (in bits)

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keiththeoutfitter1
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Re: Wandering steering

Postby keiththeoutfitter1 » Sat Jan 17, 2015 6:14 pm

Hi Steve,
it is my understanding that 15" car tyres will always give twitchy handling on an outfit, particularly by following white lines or overbanding on the road surface. That's why on mine I stuck with the standard K1100RS wheel on the front with a Dunlop D404F front tyre - heavy duty, as used on the big Harleys.
Keith t.o.1
R1200RT
K1100RS + EZS Rally Sidecar
Kawasaki Versys 650

Twisty

Re: Wandering steering

Postby Twisty » Sat Jan 17, 2015 6:22 pm

Many, many years ago we had a R80/7 outfit with EML forks and 15" wheels. I just remember good, light (but not too light) steering

:cool:

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stevedowling1
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Re: Wandering steering

Postby stevedowling1 » Sat Jan 17, 2015 6:45 pm

I'm wondering if links with a longer trail would help. I think Wasp forks are set at around 20 to 25mm so maybe heavier steering might tame them.
Regards
Steve

1994 R100RT with Monza Sidecar
1995 MZ 250cc Saxon Tour (nice little runabout)
1970 MZ 250cc Supa Five (in bits)

Nabsim

Re: Wandering steering

Postby Nabsim » Fri Apr 03, 2015 5:14 pm

I have 15" Citroen 2CV tyres (I think they are) front and back on my outfit and I wouldn't say it was twitchy at all. Only think I notice is it pulls one way when I keep speeds high but this will be because it needs aligning.

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keiththeoutfitter1
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Re: Wandering steering

Postby keiththeoutfitter1 » Fri Apr 03, 2015 5:30 pm

If it pulls to the left at high speed it could be the wind resistance of the sidecar.
Keith.
R1200RT
K1100RS + EZS Rally Sidecar
Kawasaki Versys 650

Nabsim

Re: Wandering steering

Postby Nabsim » Fri Apr 03, 2015 5:41 pm

If I hold a constant 70+ on motorways for any length of time to starts to et painful Keith. It has needed setup/alignment checking out since I have had the outfit but the size of it all has put me off. If it had been my old XS11 and Squire it would have been done ages ago but this Gemini is more like a caravan. I suppose the size of that could also be a factor

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keiththeoutfitter1
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Re: Wandering steering

Postby keiththeoutfitter1 » Fri Apr 03, 2015 5:50 pm

If it's Gemini then wind drag will certainly be an issue and it may need setting up to pull a little to the right at low speed. Those sidecars were designed in the days when an outfit would be happy at a steady 45 or 50 mph!
Keith.
R1200RT
K1100RS + EZS Rally Sidecar
Kawasaki Versys 650

Nabsim

Re: Wandering steering

Postby Nabsim » Fri Apr 03, 2015 5:52 pm

Are you perchance in Sheffield Sidecar Club Keith, I know thats South Yorkshire not East. I got the outfit off a chap up Whitby way a few years back and its been to Hull and Barton Bike night a few times

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keiththeoutfitter1
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Re: Wandering steering

Postby keiththeoutfitter1 » Fri Apr 03, 2015 6:15 pm

No, I'm not in that club. The problem is that their events seem mainly based around camping rallies and I'm afraid that I now like my creature comforts too much to go camping!
Regarding Barton Bike Night, I'm not far from there but was always working abroad when it started up and now it has become a victim of its own success and it's virtually impossible to get into (or out of) the place when it's on.
Keith
R1200RT
K1100RS + EZS Rally Sidecar
Kawasaki Versys 650

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Sofa
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Re: Wandering steering

Postby Sofa » Sat Apr 04, 2015 10:18 am

Before altering anything else do this.
Check the pressure in the front tyre.
Reduce it by 2 psi.
Go and ride it.
Reduce by 2psi.
Ride it again.
Continue until it stops getting better and gets worse then go back to the previous pressure and you should have the problem solved. Honestly it may be that simple. I have lots of friend with outfits and many with 15" and even 14" wheels and they all say that. You may even get down to 12 or 14 psi. This seems completely wrong but let me explain. The tyres you have on the outfit will be for a car, therefore they are constructed to take the weight of a car with certain sidewall strength, number of plys etc. Even a heavy outfit's front tyre will barely come near to the design loads of a car tyre so needs much less air pressure. As a rough guide find a car with the same size tyres on and when inflated correctly look at how much they bulge out at the bottom, you need your outfit tyres to bulge out about the same amount. I would hazard a guess your front tyre pressure is certainly over 25 psi at the moment as none of my "little front wheel" friends have any more than 22 psi.
Just try this first before getting spanners out. You may save a lot of time and money.
Whatever you do don't fit the standard BMW wheel, the links will have been made for the 15" and the geometry will be completely (possibly dangerously) wrong. Might be worth checking with Wasp that the links are for 15" wheels if you don't know the history of it.
2003 K1200GT Hedingham HUB Sidecar. RSP Top Yoke, RT bars, ABS/Servo removed, Klicktronic. EZS subframe, trail reducing kit and rear wheel. Wheelchair rack. Previous BMWs R80RT mono, R1100GS, R80RT (added a sidecar), R100RT sidecar, K75, K100 sidecar x2, K1100 sidecar, R1150R.

PhilO
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Re: Wandering steering

Postby PhilO » Mon Mar 07, 2016 11:57 pm

My K100 16v handles very well on Wasp l.l. forks and standard wheels and tyres. It has a hefty steering damper to mitigate any instability.
Agree with Sofa regarding car tyres which ruin the ride and make things very twitchy. OK they are a lot cheaper and look cool but the cost of the 15in wheels is prohibitive and reduce the gearing unnecessarily.
Trail difference because of fitting smaller wheels is insignificant. Wasp have tried various distances over the years and they told me it made very little detectable difference.


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