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I can crank it up at the back to get more rake, but as you say I want to see what this base line feels like first. Probably will be able to get out on Thursday or Friday if the roads are dry and I have sorted the sticky throttle cable. I can reduce the camber but its a pain unbolting the bottom rose joint.....Quote:
Originally Posted by john
When checking toe in/out at rear what are the best reference points on a Transformer? The longitudinal chassis side rails??
id suggest putting a string line down the centre, front to back to get an accurate datum then check that to the longitudinal rails.
How do I know where the centre is??
Run a string between the rear wishbone inner mounts, marking the same position on each side, the spacer washers are suitable, remove the string, fold in half to find the midpoint and mark that, put it back on the car checking the outer marks match where you started. Then repeat at the front. This allows you to run a third string front to back that will determine the centre line of the chassis from which you can take measurements.
Guy
So a bit of an update.
Using the parallel tub and straight edge of the rear wheel and some school boy trig I found OSR had 1 deg toe in and the NSR (in the photo!!) had zero!
So a bit of a fiddle on the nice adjustable trailing arms I got c0.4 degree toe in one both rear wheels.
Set the tyre pressure to 18 front 22 rear ground clearance front of tub (which is essentially a flat plate) 160mm, rear of tub 169mm so not pointing up!
Went for my 20 mile check run and the rear felt really planted, but am still not getting a stable front end at speed in a straight line. Steering and cornering so far feel fine but not exploring that. It needs constant input on the steering at ehem speeds in a straight line (like it is tram-lining all the time), not as bad as previously, so more toe in or less, and more caster (I am near the limit of the geometry already at around 5 degrees). I did not notice any bump steer problems.
Any chassis experts out there??
If I read your post correctly then 0.4 degrees per side is too much toe in IMHO, as stated in an earlier post rear toe wants to be in the region of 20 minutes total (10 minutes-1/6th of a degree per side)
The front of the chassis I would suggest to be 20 to 25mm lower than the rear of the chassis, normally measured at the front of the floorpan to the rearmost cross member.
I think you will always get some tramlining as the rear track of a GP4 is wider than the front track so the rear wheels will always follow a different section of the road. the wider the rear tyre the more I think it will show itself, I see you have the 295 TB15's though which shouldn't be too bad.
Constant movement of the steering wheel can be either bump steer or rear end tramlining, if you are happy that you have no bump steer then I would think that you are correct in the assumption that the rear is causing the issue.
Where are you with negative camber now?
do you have any play in your front suspension ball joints and track rod ends?
Craig
Castor is set to 5 degrees at the front.
Camber is 1.1 degree neg front both sides, and 0.5 degree neg. - at the rear having said that after the run the rear nearside in only 0.2 neg (yes I did keep rolling the car back and forth to settle the suspension while adjusting).
So I need to go back and check this. I can also dial out the rear toe in quite easily but I note the original had a Toe out!!!! (of 2mm - which equates to 1.6 degrees toe out per side....)
The "tram-lining" feeling seems more front driven than rear but early days. Would a slightly higher tyre pressure make this worse or better??
The Transformer build manual said ground clearance 130mm but this was for 14 inch (and 205 70 tyres?) so with 15 inch wheel this will be higher, and the original Strato's had a ground clearance of 170mm at the rear of the floor plan. I dont feel it as aero lift problem but will ponder this.
Any pointers as I need to "sign Shades off" so I can get on with some other winter tasks. I hope for a few more test days in coming days to enable this.
Absolutely none. They are less than 5k miles old and were jiggled comprehensively by my MOT guy last week. Apart from the bottom suspension joint and track rod ends it is mostly rose jointed and quite quiet....But that would be a good place to look if the car had miles on it. There is no play in the steering either.Quote:
Originally Posted by strat24v
Rear camber on group 4 tyres i run 0 deg due to width of tyre, one thing to check on the front end does the steering rack have any tight spots when jacked up with the weight of the wheels. On my Hawk the steering rack platforms had distorted due to welding and was putting a bow effect on the rack body when the clamps were tightend, I over came this by maching the inside of the clamps to a width of 3mm
Regards Ken
Even with a 345 tyre I would still run with 0.5 degrees of negative. There is so little camber gain on the strut type suspension that as soon as the car rolls in a corner then the wheel will go positive so any negative you can introduce statically IMHO is an advantage. Clearly you would also not run with 1.5 degrees of negative on the road.
Unless you had to because some jerk ordered the wrong struts of course.......
Thread Hijack!!Quote:
Originally Posted by john
& Paul used to speak so highly of you!!!!
Hee hee,, well I'll butt into anyone's conversation. Somebody used to speak highly of me? Oh, that Paul... Now I know you're kidding!
Update and back to chassis tweaking. Just went out again for another bit of excitement. Car is rock steady at speed but very sensitive to steering input with minimal self centering. I tried going up to 20 psi on the fronts which gave a v small improvement in self centering but not much off line. Under dynamic steering it feels great / just fine etc etc.
I have not stiction in the the steering and no wear. I also have upgraded rose jointed 131 uprights so dont think that geometery is at fault. I am coming round to the fact I am running Michelin race tyres TB15 215's on the front that have a very flat and sticky profile so will follow were they are point more than an ordinary tyre.
131? They should be 132 items.
What's your bump steer like?
Do you have a split alloy column bearing fitted?
Typo yes 132! Bump steer how does one check this on the road? I hit a few bumps both cornering and straight at c70mph and the car was quite well behaved.
re column bearing are you referring to the top of the steering column?
Bump steer is something that you need to reduce or eradicate while setting up your suspension. It's probably more important to fix than any other part of your chassis setup. If you have the hawk build manual, there is a section in there in how to fix it, if not I'm sure someone on here can give you a link to it.
The split alloy bearing is fitted on the intermediate steering shaft. Owners generally replace them with a proper bearing of some kind.
I have the build manual and have read this up.
What are the symptoms of bump steer?? as all I am trying to dial out is the straight ahead sensitivity at the mo. Car was built by the legendary Bob Pilot rip so with all the shimming evident I think it is fair to say I will not touch yet.....
anyone shed any light on this upgrade?Quote:
Originally Posted by strat24v
Unpleasant straight ahead.
The split alloy bearing is just two halves of a block with a semicircle cut out such that it clamps around the intermediate column and is bolted to the chassis. Sometimes it's a little tight and just grips the shaft and restricts it's ability to rotate. There are two alternatives that I've seen. First involves splitting the intermediate shaft and sliding a standard bearing over the shaft before re-welding the UJ back on. After that's done you need to make a suitable bearing carrier and support. The alternative involves splitting the shaft and fitting a Rose Joint and re-welding the UJ. This is the simpler solutions the threaded Rose Joint gives you a lot more adjustment height wise and almost as little restriction as a full bearing. Unfortunately RHD cars can't do away with the intermediate and adaptor shafts as the column routing falls between the brake & accelerator so it has to stay high to avoid feet fouling it. LHD cars can have a lower column route as the shaft passes between the brake and clutch pedals.
If you can measure your intermediate shaft length between the two UJ's I'll compare it to a spare I have here that has a bearing fitted already if you decide you want to try that mod.
Guy
Car steers straight with no hands, just sensitive to hands!! Ie no Ackerman effect.....
Guy I have just checked and have the split alloy bearing but it is fine and not providing any issues so I think I will pass on any work here.
Guy, what were your car's symptoms before you decided to wind on a lot of castor? Do you now have good self centering, or just a little bit or none at all? Did you find you had a bump steer issue with so much castor? I assume by the name, bump steer means the steering is affected by bumps??
Hi Tim, the first thing I did when setting up the car was wind on as much castor angle as I could get away with. The tyres just clear the bodywork on full lock/compression/droop. The first time I drove the car there was some self centering which improved as the mileage grew. (I'm back to some now with the new LHD rack but expect it to ease as the rack beds in). The first time I drove it the bump steer was terrible. I got as far as the MOT station and back. At which point I stripped the shocks off and set the rack height to eliminate the bump steer. Easy enough to do but time consuming. And essential if you want to be able to relax, relatively speaking, behind the wheel.
The symptoms of bump steer are finding the the car darts to one side if you hit a pothole or a bump in the road. It can be quite violent and you'll know if you;ve got a problem with it already! I'd be amazed if it hadn't been dialled out at build or by Gary during use.
Guy
Going in the garage and twiddling the steering wheel and reporting no issue isn't really a way to solve you're issue. Rather than listening to tales of other people's wonderouss car building skills, I'd be inclined to forget them, go back to basics and eliminate all issues others besides myself have mentioned. I have only seen two professionally built models in all my time that I'd consider good enough not to have to strip and start again.
Guy thanks for this. I need to do more miles but today showed very good stability, even over bumps. Maybe the twitchy feel compared to my other Lancias goes with the territory. I am looking again at the front end and am measuring everything. This is a well put together car and nicely developed by Gary that I am proud to continue its refinement.
thanks to other contributors too as all experience welcome to add to the theory.
Slightly off-topic but there is a nice description of bump steer and how to try to dial it out in "Project Binky" episode 10 (around 23 mins onwards) and continued in episode 11, where they also go into some detail about "Ackerman" - I see that you mentioned this above so maybe you are already aware. If not - be warned! - and be prepared to invest 5-6 hours of your life watching all the episodes (addictive viewing I find).
Change of header title!!!
Just finally got Shades off Castor / tracking gauges and out for a test run
Transformed!
2mm Toe in Front
0.2 degree Toe in each side rear
4.5deg Castor front
-1.1 camber front each side
-0.4 camber rear each side
Ride height 15mm higher rear to back
Front tyre pressure 20psi
Rear 22psi
Steering slightly heavy at parking speeds but lightens up and has the twitchyness at speed has gone. Roads are too greasy to explore handling at any limits but I have a big grim on my face as IT IS SORTED!!! AND I love driving it!!!!
This is just a base line and in due course I will put it on laser rig to check my measurements done mostly with digital protractor set up.
I think the biggest contributor to getting to this point was to increase the castor on the o/sf which was a shade over 1.5 degrees before adjustment. I have yet to find any bump steer issues so conclude this was properly set up by my predecessors.
Its mentioned on here that having a proffesional outfit do a proper alignment, setup and spring rates is the best way. Good you have it sorted now.
Further transformed after a professional setup today.
Used a firm in Colchester that specialise in track hardware - mostly drifting.
The biggest change is in tyre pressure up to 28 front 30 rear from 22 all round. Castor wound back to 4 degrees, 1.5 deg camber on front, .7 on rear, and parallel toe rear and 2 deg toe out front.
Was a bit mystified until I drove it and found it delightful (not a delightful handful). We will have to see. The overall comment was nothing much is going to remove the twitchiness until I source different tyres as the super soft TB15's will always tramline due to their stickiness......
So I gave him the task of finding a set of matching tyres (there aren't any other than the Pirelli equivalents are there??)....
[QUOTE=Lancialulu;29755
Used a firm in Colchester that specialise in track hardware - mostly drifting.
The biggest change is in tyre pressure up to 28 front 30 rear from 22 all round. Castor wound back to 4 degrees, 1.5 deg camber on front, .7 on rear, and parallel toe rear and 2 deg toe out front.
.[/QUOTE]
hope you've got good insurance.......
Tim, those tyre pressures sound way too high to me. Keep an eye out for uneven tread wear, especially in the centre sections! How does the steering self centering feel?
They're not trying to get you out there drifting are they?
Guy I was surprised too but after a long discussion I thought it could be worth a try. If they get work then they will heat up and pressure will go up but on the road they will not get this work as evidenced on my return the fronts were stone cold. I have to say the ride and steering feel was better.... No I am going drifting either.... If the tyres heat up then drop some pressure...., but the self-centering is compromised by the wider than spec super sticky "race" tyre. I will look out for uneven wear though as there isnt much tread to play with to begin with! Shame Friday looks quite wet as it is my travelling day to Goodwood and I doubt I will go in Shades after my boating experience this morning!Quote:
Originally Posted by Guy Mayers
BTW what is the mph / 1000 suppose to be for a 164 12v fifth gear re tyre diametre as is seemed high c 27mph/1000?
Can't help with that Tim but suggest you try it with a Sat Nav that shows your speed? It'll give you a good idea how accurate it is. I've just had my speedo recalibrate by Speedy Cables as it was reading a tad too fast (approx 4 times I think!) but now it's spot on to the Satellite Speedo I bought to keep the "right" side of the law.Quote:
Originally Posted by Lancialulu
Guy
Hi Guy
Speedo already checked and surprisingly accurate! Not sure about the rev counter though which is why I asked?
Any idea of final drive ration in a std 12v box and 5 ratio (is it 1:1 or an "overdrive"?)? I can work out from first principles then...
Been a long day Tim..... Sorry, I don't know what the final drive ratio for a 12v box is.. The info must be out there on the inter web somewhere?
Guy
from the old forumQuote:
Originally Posted by Lancialulu
Attachment 9444
Brilliant. I calculated 20mph/1000 in 4th while on the move so that is spot on. Will do a more exhaustive test in coming days....