Tyre Pressures and static sag

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

Moderator: Moderators

Forum User
Posts: 145
Joined: Thu Sep 14, 2006 2:04 pm
Location: Preston, Lancs

Tyre Pressures and static sag

Postby brunocrossley » Wed May 24, 2017 11:00 am

It's taken a while, but my R100 bitsa and Velorex combination are almost ready for the road. I've gone through the geometry and tried to set things to be a average of several recommendations with regard to lead toe-in and lean etc.
I'm now looking at things like suspension and tyre pressures as a benchmark.
I've wound the Ikon rear shocks up to maximum preload and the third of four settings on the damping. I have other options with shocks. At present the K100RS sport front forks have slightly lighter than standard K springs. (I reworked the forks when I fitted them for solo use) I could put the standard springs back. I'm not sure what to aim for though and not having ridden an outfit before, I'm wondering if there's a rule of thumb? As a solo I'd normally start with static sag at about a third of the total travel.
The tyres are currently Avon Roadriders on the bike; 100/90x18 and 120/90x18. The chair has a Mitas 3.50x16. Any suggestions as initial pressures to try?
On another tack, if the bike was solo and I fitted longer rear shocks and/or dropped the forks through the yokes, I would steepen the fork angle and quicken the steering. With an outfit, and assuming that the the other geometry settings were readjusted to suit, would doing these alterations have the effect of lightening the steering?
Fingers crossed, it's off to the garage this weekend for an MOT.

Thanks in advance, Mark
You do not have the required permissions to view the files attached to this post.
Cheap bikes never are.
78' R100RS
14' R nineT

Forum User
Posts: 107
Joined: Mon Aug 24, 2015 10:04 pm
Country of Residence: Havant, England

Re: Tyre Pressures and static sag

Postby Richard(Sande)Sanders » Fri May 26, 2017 7:15 pm

I've always used the standard pressures on the bike as a starting
point, & normally found them to work well with a chair fitted, on
the chair wheel I start at about 25 psi & adjust by a few psi until
the outfit rides to my liking. Final pressure depends on load &
use, but is always a bit of trial & error.
Static sag I've kept to around the 1/3 mark.

Tony the Skin
Club Member 12
Posts: 583
Joined: Mon Jun 02, 2014 11:38 am
Country of Residence: England
Location: Bury

Re: Tyre Pressures and static sag

Postby Tony the Skin » Fri May 26, 2017 10:25 pm

Tyre pressures should be set according to that advised by the tyre manufacturer. If it is not on their published website phone and ask them. Avon are very good on this.
BMW R75/5
BMW R75/7
BMW K75 Sprint
MZ 251
Suzuki GT750A

Membership No. 672

Forum User
Posts: 1
Joined: Fri Jun 02, 2017 11:53 am
Country of Residence: england
Location: Stoke on Trent

Re: Tyre Pressures and static sag

Postby xsfool » Fri Jun 02, 2017 12:00 pm

Have to say my r100/velorex combo has a contigo on the back and Continental expect you to use the bike manufacturer's recommended pressures. Totally dodging the issue imo. Got an Avon on the front tho :-)

Return to “Sidecar Chat”

Who is online

Users browsing this forum: No registered users and 1 guest