Sam's build thread

[sambb]

Yep that was the plan - sunbake the tyres between runs. Sitting them on a black trailer will do the trick. I'll take the set of softs and then a pair of mediums. If they are diabolical on the first run up the esses and don't seem to have potential to grip on the front then I'll revert to the softs.

Hi mate - no wont be doing Ringwood. I got moved to afternoon shifts all weekend which writes off days and nights basically so no can do. I'm going to have to lay out the whole hillclimb calender and work out what i'll be doing this year. I'm pretty much a sure thing for the Tamworth and Ringwood state hillclimbs because they are my best bet of a really good result. The 3 lap sprints of the Tamworth track would be good too. Wakefield simply has to happen again but probably at the end of the year. But if any other 2 lappers come up at Ringwood then let me know cos I can do that as a day trip which doesn't skyrocket the costs too much. Let us know how you go up there.

[sambb]

I recently finished my toe alignment plates and gave them a go today. I'd fitted eibach shims shooting for zero toe and to square up my rear cambers. If I survive Bathurst there wont be many fast circuits for a while and then i'll shoot for 2 degrees neg rear camber and 2mm rear toe out.
Because toe measurements in mm's vary depending on what size rims you have or what width you are measuring across on the toe plates (only angular degrees can be used as a constant when comparing toe), from what I can tell there is a fair bit of trigonometry to do to convert your toe plate measurement to a mm toe number for your rim size.
My 600mm plates hold the front and rear tape measures 580mm apart. My total rear toe came in as 1mm wider on the back measurement (F: 1628 vs R: 1629). Assuming both tyres are toe'd in equally for the sake of calculation, you then take that as 0.5mm toe in on each side. If you have 0.5mm laterally along a 580mm length and do school trig: inv Tan of 0.5/580 you get a toe in angle for each side of 0.05 decimal degrees. To convert that into mm terms for a 15in (381mm) rim you go: Tan(0.05) = x/381. x = 0.328mm toe in on each side. Times that by two and I have 0.657mm total toe in on my rear beam. The shims have taken it from +5.5mm toe in to +0.657mm toe in.
And you can feel it. It turns in so much more readily now. I'm glad the calcs bore out what I felt and that it wasn't placebo. By the feel of it I think Gary is dead right. With so much toe in at Wakefield the tail needed to be sliding/tyre slipping to get it to turn with little lifts and brake dabs to help it but now it just WANTS to rotate and rails through. It will be very interesting at 2mm toe out with an extra 0.5 deg of rear camber next time around at Wakefield.
I cross checked this method against the fronts that were set to 3mm toe out 3 weeks ago and it came in at -3.12mm toe out so it looks to be accurate enough.
Of course to make the calcs work you have to halve your total toe, do some calcs and then put the number back into total toe number applicable for your rim size. This final total toe number is correct but it still could be that one side has more and one side has less actual toe and to find that out you'd need to string line or get laser treatment. So i'll get it checked properly to confirm this. But at least now I can eg change out struts, alter ride height, change cambers and be pretty much assured I can toe check it afterwards.
Cant load pics from work but many to come.

[sambb]

great early 80"s F1 technical doco - ground effects, our World Champ Alan Jones, 3.0L V8's vs 1.5L turbos (V8's not so much), the birth of anti-lag, Villeneuve still alive and prost/piquet on the up.

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[metalhead]

Nice work.

P.s. Because it's a straight line change, no trig needed for converting toe measurements unless you want it in degrees. Just multiply your measurement by (tyre diameter/toe plate length). I.e. 0.5 x (381/580) = 0.328mm

[Sydneykid]

I recently finished my toe alignment plates and gave them a go today. I'd fitted eibach shims shooting for zero toe and to square up my rear cambers. If I survive Bathurst there wont be many fast circuits for a while and then i'll shoot for 2 degrees neg rear camber and 2mm rear toe out.
Because toe measurements in mm's vary depending on what size rims you have or what width you are measuring across on the toe plates (only angular degrees can be used as a constant when comparing toe), from what I can tell there is a fair bit of trigonometry to do to convert your toe plate measurement to a mm toe number for your rim size.
My 600mm plates hold the front and rear tape measures 580mm apart. My total rear toe came in as 1mm wider on the back measurement (F: 1628 vs R: 1629). Assuming both tyres are toe'd in equally for the sake of calculation, you then take that as 0.5mm toe in on each side. If you have 0.5mm laterally along a 580mm length and do school trig: inv Tan of 0.5/580 you get a toe in angle for each side of 0.05 decimal degrees. To convert that into mm terms for a 15in (381mm) rim you go: Tan(0.05) = x/381. x = 0.328mm toe in on each side. Times that by two and I have 0.657mm total toe in on my rear beam. The shims have taken it from +5.5mm toe in to +0.657mm toe in.
And you can feel it. It turns in so much more readily now. I'm glad the calcs bore out what I felt and that it wasn't placebo. By the feel of it I think Gary is dead right. With so much toe in at Wakefield the tail needed to be sliding/tyre slipping to get it to turn with little lifts and brake dabs to help it but now it just WANTS to rotate and rails through. It will be very interesting at 2mm toe out with an extra 0.5 deg of rear camber next time around at Wakefield.
I cross checked this method against the fronts that were set to 3mm toe out 3 weeks ago and it came in at -3.12mm toe out so it looks to be accurate enough.
Of course to make the calcs work you have to halve your total toe, do some calcs and then put the number back into total toe number applicable for your rim size. This final total toe number is correct but it still could be that one side has more and one side has less actual toe and to find that out you'd need to string line or get laser treatment. So i'll get it checked properly to confirm this. But at least now I can eg change out struts, alter ride height, change cambers and be pretty much assured I can toe check it afterwards.
Cant load pics from work but many to come.

Nice geometry there, Pythagoras would be proud

The toe measurements that I suggested you try are at the extremities of the tyre, from memory 205/50/15 A05's are around 590 mm diameter, +/- the width of the tape measure. So your 600 mm toe plates should give a result about the same as I suggested. As usual it's not so much about being 100% spot on accurate but more about repeatability. If it's say 4 mm and it needs more toe out, then we adjust it to 6 mm, ie; it's +2 mm that's relevant, not the 4 or the 6 mm's.

The use of toe out on rear of FWD cars is not understood by many, most wheel alignment shops freak out at the very mention of it. But it's essential if we want the car to rotate around the front. The trick is having the right amount of toe out such that the rear end movement is proportional to the amount of steering input. Unfortunately it's not linear, for tighter corners (more steering lock) we would ideally want more toe out but for higher speed corners (less steering lock) less toe out would be better. Wakefield isn't too tricky, compromise wise, as there's not really a high speed corner, the kink is more a braking zone. Hence, for example, Eastern Creek and Philip Island need a slightly different set up.

Some drivers just don't like the nervousness, instantaneous response, from the rear end so we compromise the set up to keep them comfortable. Although I have been known to sneak more toe out each time they drive it until they complain. For the 12 hour one year I started one driver off at 2 mm toe in for practise as he couldn't even tolerate zero toe. By the time the race came he hadn't noticed that I'd snuck 4 mm of toe out on it.

In regards to individual toe (per wheel) versus overall toe (accross the axle line) using toe plates, what I do is adjust one side at a time. So if it's an overall 4 mm and I need 6 mm, then I adjust one side to get 5 mm. Once I have the overall at 5 mm I then adjust the other side to end up at the 6 mm overall target. This means I only have to string line once every couple of race meetings, unless of course there is some specific reason to do it more often.


Lot's of fun to be had, setting up a race car is a journey, we never reach the destination.


Cheers
Gary

[simon k]

Cant load pics from work but many to come.

very keen to see them - I'm getting a lot out of your work and explanations

I'm sniffing at the pointy end of the motorkhana nationals (7th out of 153 last year, very happy) and rear toe is one of the things that I think will make a little more positive difference this year...

[sambb]

So here was the shim job on the rear right. You can see the blank end of the beam with everything removed. You can see the shim fitted with the cut outs snapped off to allow for the bolts and a dummy fit up of the stub axle afterwards (prior to some material at the tip being removed from the shims to allow for the ABS sensor). Main problem with these shims is that they space out the stub axle but not the calipers which still bolt to the beam. You can see some funky angles the disc was pulling through the caliper so I had to try different width washers to space the caliper in a way that matched the camber angle of the stub. Impossible to account for toe change at the caliper really so the pads will just have to bed into that. Other thing to take note of is that if you go from say 4mm toe in to 2mm toe out on one side, the rear edge of the disc will run closer to the caliper which is positioned behind the disc. This means that to fit it up you do have to wind in the piston to reposition the inner pad further in. If you don't do this you'll just be wedging the disc against the old pad position and will bind everything up when you tighten the caliper.


So these are the plates. I was lucky enough to be gifted a length of stainless pre bent at the base. I cut 600mm lengths which I copied off a proprietary plate I saw on the net and added the bend along the top edge to add stiffness to it. The threaded bases are so that I can adjust the base position of the plate eg up to get above the tyre balloon on a 195/55 or down if say measuring a 225/30. The angle at the bottom works well because the threaded legs are canted and once you set the plates against the tyre the lean of them holds the plate against the tyre. They are heavy too. I did it in the wind by myself and it was all rock solid. I cut three tape measure heights but found using the lowest was the best to get under the front engine bay belly pan. Each tape measure slots in with its centre on marks 10mm in from each side which is where the 580mm length came from fro the calcs. Then all you need is two tape measures in mm's and just make sure you tension them simultaneously as you read off the front:rear measurements.
Thanks Andrew re the calc. I did think that doing inv Tan and then Tan afterwards negated one another. That'll be easier. Yeah I can tell you Simon K I haven't even gone into toe out territory, just lots of toe in to more or less zero and even at brisk street speeds it feels like a proper mod has been done, not just an angle change. Gary I was hesitant to jump straight out of 5mm toe in total to 4mm toe out total in one go especially considering the other mods that I'm still getting used to, which is why I opted for zero toe as an interim step esp with the walls of mountain straight about a foot away from my helmet in only a few weeks..... but yeah if it feels ok there, the spacers will be straight back out and in with more toe out for the rest of the year.

woops upside down but you get the idea. Added a little air dam by screwing some plastic strip to the small lip under the radiator. With the ride height up a lot of air hits the belly pans leading edge that is angled like a plane wing aligned for take off, so hopefully this'll force a bit more air to go over/around the front, instead of trying to make me do a Mark Weber at Le Mans which is what it feels like sometimes.

[sambb]

Oh and the DS2500's were sweet at Wakefield. Lots more initial bite (even on the street) compared to remsas, a firmer pedal overall and they never faded. However I never did more than 5 laps per session due to linkage dramas and was never in a position to string together <1:11's one after the other so I don't think they've been fully tested yet. But for 90% laps between 1:15 - 1:12min and some quickies thrown in, the DS2500 front, Remsa rears, fresh Textar Dot4 LV fluid and front ducts worked. I'll feel confident going there again with them without doing anything else to the brakes but no doubt something will crop up next time - that's just tracking.

[sambb]

Thanks Simon K re the comments on the thread. That's the main reason why I've done this. I've probably learnt more from car build blogs (and then checking the little titbits I want to use against other sources) than anything else. I've always loved chassis stuff mostly because I've always driven underpowered cars compared to my friends so I've been lucky to stumble across Mark Ortiz stuff ( auto-ware.com ) and had Gary take an interest in the suspension stuff while I've been doing this and the other car. One day I'll get to adding more power once I have a chassis (and driver) that can handle it. So its been good to get all the nitty gritty stuff up that others can learn from. The only thing that worries me about having a thread is that one day I'm sure I'll hit a wall/tree at a hillclimb or something and everyone will get to know about it, but hey its all a learning curve - I already think about what the next car will be if that happens which is a bit fatalistic.
Yeah I'd have thought lots of rear toe out would be spot on for motorkhanas along with narrow rears and wide fronts and a good handbrake. That's a pretty awesome standing out of such a big field. Got any pics?

[metalhead]

Sam/Gary/anyone else with experience, if I might briefly interrupt Sams thread to ask a question of my own. I ran Ringwood on semis (295/30R18 Continental Contiforce Contact, 80 treadwear) for the first time yesterday, and it sucked... I think maybe the semis I picked up might be toast, I did get them very cheap and although new, they were manufactured 5 years ago (rookie error, didn't check before buying). I had way less grip than I normally have on my (admittedly very good) 285/40R17 Continental ExtremeContact Sport road tyres (like probably about 3-4 seconds slower than I expected, based on other entrants I normally compete against). Just want to make sure that I'm not missing something before I offload them, I've never run semis before so I may have missed a trick? I'm assuming I had enough heat in them, as it was hot, I did a quick burnout, and was turning the tyres basically all around the track for a ~80 second course. 295s might take some heating, but I would have assumed that would do it? I didn't seem to have much if any more grip at the end of the run. The reduced sidewall shouldn't be a major issue should it? Any advice?

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