Caster angles???

Spaniard
Posts: 62
Joined: Mon Nov 19, 2018 1:06 pm
Location: Wisconsin

Caster angles???

Post by Spaniard » Wed Oct 06, 2021 8:55 pm

I recently started playing around with caster angles and was surprised that my caster was at 0 deg according to the level on my mobile phone.

I was reading on another post about adjusting the caster with shims. I have a Type 3 with the standard non adjustable upper A-arms. The only shims I could see are the washers that are next to the poly bushings. One on each side of the bushing/ 4 per a-arm. I ended up grinding back part of the upper A-arm mount so I had room for some shims to be able to shift the a-arm back thus tilting the upright back.

After doing this I have 2deg of caster and the handling is much much better. It still doesn’t have the 5 deg it should have according to the numbers I have been reading. How are you guys adjusting caster ? Are the large shims by the bushings the ones you are using to adjust caster or did you have additional shims in place that you could move around.

I think I could do the same to the lower A-arm but shift it forward to increase the caster to about 4deg. I think I need a more accurate way to measure the caster and will look into that first.

Any thoughts from you guys?

westendguzzi
Posts: 493
Joined: Tue Sep 25, 2018 7:30 pm
Location: Huntingdonshire

Re: Caster angles???

Post by westendguzzi » Thu Oct 07, 2021 9:11 am

When I originally built, I used the adjustable top wishbone which was fine with the original shockers.
I've since upgraded to the comfort spec which involved slightly longer shockers and modified bottom wishbone.
I have shimmed out with washers to give me 5deg.
Evident on the picture that it could do with a modified top wishbone which I believe is available from Al.

With 0deg caster, yours must have handled like a blind pig.
Just sayin!
Attachments
IMG_0890a.jpg
IMG_0889a.jpg

Spaniard
Posts: 62
Joined: Mon Nov 19, 2018 1:06 pm
Location: Wisconsin

Re: Caster angles???

Post by Spaniard » Thu Oct 07, 2021 1:55 pm

Well it handled nice and quick below 60mph. Over that it was a bit nervous. I am going to measure the caster again more accurately this weekend and see what the angles are. If I can get it up to 4deg I will be happy.

Thanks
Ivan

westendguzzi
Posts: 493
Joined: Tue Sep 25, 2018 7:30 pm
Location: Huntingdonshire

Re: Caster angles???

Post by westendguzzi » Thu Oct 07, 2021 4:11 pm

Ivan, you may also like to consider the toe-in dimension of 3mm.
The will affect the straight line stability at speed if not set up right.
Tony

Widdup
Posts: 15
Joined: Sat Oct 05, 2019 2:03 pm
Location: Baildon

Re: Caster angles???

Post by Widdup » Thu Oct 07, 2021 4:35 pm

I had exactly the same problem when I built my type 3. I spaced the shims equally front and back not really realising their importance. Like you the handling was fine up to about 60mph, after that if I hiccoughed it would go to the other side of the road. On investigation I found one side to be 0 degrees and the other upright was actually leaning forward. I couldn’t correct it with the shims without chopping things off but Alan supplied pair of adjustable wishbones which enabled me to get 8 degrees lean back on both sides which is as much as I can achieve. This has greatly improved things but even with 3mm toe in it’s still a bit skittish over 70mph but you get used to steering with a very light touch.

Spaniard
Posts: 62
Joined: Mon Nov 19, 2018 1:06 pm
Location: Wisconsin

Re: Caster angles???

Post by Spaniard » Fri Oct 08, 2021 2:43 pm

I just had a thought. Are the standard non-adjustable upper A-arms symmetrical? By that I mean can they be installed upside down? If they have a setback built into them and they were installed upside down then the set back would actually be set forward giving me the 0 deg caster. Just a thought. I will investigate further when I have time.

Spaniard
Posts: 62
Joined: Mon Nov 19, 2018 1:06 pm
Location: Wisconsin

Re: Caster angles???

Post by Spaniard » Sat Oct 09, 2021 12:54 am

Well after some measuring and playing around with suspension geometry I am now at 3.5 deg caster angle. I took it for a drive and it is much better. It feels much more stable at 70 mph. It may be that I got used to driving it with 0 deg caster and now at 3.5 deg is so easy to drive. I will leave it alone for now but I am sure I can increase it to 5 deg by shimming the lower A-arm forward.

For now I am going to enjoy the fall colors of the Maple and Oak trees and when winter comes I will tackle the charging system upgrade. I got my hands on a small alternator off of a MG Norge which should provide me will all the power needed for electric vests and some nice driving lights. To many deer on my local roads at night to not have good lights.

Spaniard
Posts: 62
Joined: Mon Nov 19, 2018 1:06 pm
Location: Wisconsin

Re: Caster angles???

Post by Spaniard » Wed Oct 13, 2021 2:46 pm

Yesterday I made a run in the Triking. The first after getting 3deg of caster. I can say that it definitely feels much better at 65+mph. It was worth the effort to get it there. There is a significantly more stability and the self centering of the steering has increased. I don’t think I want to put more caster than that into the uprights as the steering effort has increased. It’s not a huge amount but I don’t think I want to increase it much more than that.

Thank you to everyone who offered advice.

iant-s
Posts: 24
Joined: Sun Nov 29, 2020 8:31 am
Location: Staffordshire

Re: Caster angles???

Post by iant-s » Wed Oct 20, 2021 8:34 am

How are you all measuring the caster angles on your cars?

I have the car up on stands so the suspension is fully extended.
I have made sure the car is level using a spirit level along the floor-pan.
I have a digital angle tester (inclinometer) stuck to the flat face on the front of the suspension "upright" (the bit that has the stub axle on it) adjacent to the brake caliper.

My understanding is that the upper wishbone ball-joint should be behind the lower wishbone ball-joint. This will hold the suspension "upright" (the bit that has the stub axle on it) in a slightly tilted position leaning backwards at the top. It is this degrees of tilt that gives the positive caster angle. Is this correct?

I asked Alan about my twitchy handling and he said the standard assembly has identical and not handed wishbones, with the washers equally set holding the wishbones central to the chassis mounts. This should give 5 degrees of positive caster. If that is the case I must be measuring incorrectly. I got 0.6 degrees passengers side and 1.4 degrees positive drivers side. I don't have any shims/ washers/spacers other than the large diameter washers which support the ends of the urethane bushes. There is no space for anything more so my set-up looks just as it should.

My handling was exactly as the Lads have previously described. Fast and responsive up to 50mph - twitchy and alarming at 60mph.

Doverhay
Posts: 235
Joined: Thu Sep 27, 2018 6:43 pm
Location: TA66NN

Re: Caster angles???

Post by Doverhay » Wed Oct 20, 2021 9:36 am

Having read all the posts on this subject I can add that I’ve been through the same scenario, and as TD has explained, the camber, caster and toe in angles are critical. The most important of the three is caster and toe in, in my opinion of course. However you need to do each in sequence, my first was to get the camber angle to the desired position, next the the caster angle and finally the toe in. Playing about with the caster or camber angles will always require the toe in to be checked again before completion.
I have also had the opinion that the rake of the car has an affect on the cars handling at high speeds, hence the reason I put a wing on the front of mine which has always given amusement to my fellow Trikingsters. I feel the rake of the car, especially when you fit the 15” wheel is wrong, the back of the car needs to higher that the front to stop the air lifting the front at high speed a promoting light steering effect. Of course again this is only my opinion but with all the above done my Triking T3 seems to be stable now at all speeds.
Attachments
8126FB47-06B0-450B-A6DE-00C823896BB2.jpeg

Post Reply