Improved Front Geometery with Sierra Uprights

[sullayton]

Wow, from what you've all written I must be a driving god to have kept it on the road for this long, joking Ha Ha.Thats it then everyone is saying the same thing about castor. Just one thing fellow techies, did I do right by measuring castor with a camber guage and 20 deg lock right - measure camber, 20 deg lock left - measure camber, subtract smaller value from larger value to arrive at castor angle? Is that accurate or a trackside check.

[Darkspeed]

Depends on the type of gauge but with that sort of measurement the 20 degree turn angle needs to be accurate and on turn angle slip plates.

I know I am generalising but typically he less involved the measurement the less accurate its likley to be.

Andrew

[mrwibble]

Is it the consensus that any chassis using sierra uprights will have less than optimal geometry?

[RobMsport]

I'm sure someone will shoot me down but in my oppinion yes . Manufacturers only changed from Mac struts due to lack of availability . The best cheap solution if billet purpose made are too expensive is Triumph uprights . SSC changed to these when they didn't like the result of using Sierra one's .

[mrwibble]

hmm... wish i'd listened when someone voice d scepticism at the start of my build. ah well you live and learn. might be a pair of cleaned painted, with new bearings on ebay sometime in the future.

[JohnEM]

At the Exeter Kit Car Show yesterday and had a chat about this with Martin from RAW.
He say nothing wrong with Sierra uprights as long as they are set up correctly, Settings are as follows;-
Castor 5.5 Deg, Camber 1.5 Deg with 1mm of toe out.
He did say that you should also check that the rear of the car is following the front no more than 5mm out (he uses a long piece of metal to check alignment)
At the rear Camber 0 to 0.25 deg positive and 2-4 mm of toe in, in total.
Rake 1/2 inch lower at the front.
He emphasised that the rear does affect the steering feel and handling and both need to be close to those settings to get the best out of the car.
RAW now sell adjustable wishbones for both front and rear of the Striker, the rear wishbones adjust toe and camber,they will of course set car up for you.
He also pointed out that each chassis would be slightly different even each side of the chassis. He thought that the steering rack was fine where it was and did not think that they had changed that since Sylva made it.
hope that helps, it does me, off to get some measurements taken.
John

[mrwibble]

At the Exeter Kit Car Show yesterday and had a chat about this with Martin from RAW.
He say nothing wrong with Sierra uprights as long as they are set up correctly, Settings are as follows;-
Castor 5.5 Deg, Camber 1.5 Deg with 1mm of toe out.
He did say that you should also check that the rear of the car is following the front no more than 5mm out (he uses a long piece of metal to check alignment)
At the rear Camber 0 to 0.25 deg positive and 2-4 mm of toe in, in total.
Rake 1/2 inch lower at the front.
He emphasised that the rear does affect the steering feel and handling and both need to be close to those settings to get the best out of the car.
RAW now sell adjustable wishbones for both front and rear of the Striker, the rear wishbones adjust toe and camber,they will of course set car up for you.
He also pointed out that each chassis would be slightly different even each side of the chassis. He thought that the steering rack was fine where it was and did not think that they had changed that since Sylva made it.
hope that helps, it does me, off to get some measurements taken.
John

interesting post, what exactly do you mean the rear is following the front no more than 5mm out?

[RobMsport]

Centre line of rear exactly inline with front centre line ( axles that is) . If you put a straight ally or steel angle in front of your car then mark the chassis centre on it with tape ----- repeat same at the rear then measure/mark a distance from that centre tape a few inches beyond the outside of the car ----- repeat on each corner at the exact same distance . Tie string between each front and rear ally angles , pull tight and fix on blocks or something .
Now measure the distance from string to wheels all round . This will show up any discrepancy with the rear axle following the front plus give your toe measurement at the front --- rear too if independant .

[JohnEM]

Thanks Rob couldn't have put it better!
Yes it's the alignment of the chassis ensuring that the car is not going down the road crab-wise.
John.

[RobMsport]

A very dear friend of mine explained how to '' string '' a chassis , way back in 1999 when mine was at the build stage . He worked on the carbon chassis for Mclaren or sticking and glueing as he described it !! It was his Stylus that I attempted to match when building mine although didn't quite manage. Cancer took him away at 45yrs old but not before he'd taught me a little.
John , did you do Odiham