Sam's build thread

[sambb]

Ok. Yep Ringwood is a bit of a lock in each year so I'll see you up there then. I'll be happy not to race until then anyway. I was hammering the strips yesterday and now my noisy droplink is completely shagged and my noisy CV is now a very noisy CV so I have a few things to do before I get back on track. So yeah Tamworth no, but Ringwood yes.

[seangti]

Nice write up Sam and great results. Shows the development you've put into the car and your driving.

[sambb]

Thanks Sean. I'll put up a vid a bit later. I accidentally left the GoPro running and used up all the cards space so I'm left with a giant vid that needs editing and not much actual track footage.
Question for Gary..... So I'm in a bit of a bind as to what to do about the front end. As I said this was the first time i've run up to temp semis with the softer/standard front bar on a circuit. While it was great for cold tyre runs in hillclimbs it did feel like it was overloading the outside front and I was finding it harder than usual to get good hard drive off the corners and was missing apexes.
You've mentioned in the past that if for instance you use bump adjustment in dampers to 'add' roll stiffness, that it will only help initially but then the front will progressively give up the longer the loads last for. Well I definitely found that.
For example the left hander that goes up the hill in front of the pit straight, I would turn in and it would do so nice and sharp and the back would rotate nicely but then the longer I'd move through the corner and really needed to be getting on the throttle, it'd start to understeer out wide. Good initial response but then the front right felt like it was getting buried the further I moved through the corner. Adding rear damper helped a bit, but it felt like it was a front issue and maxxing the front dampers changed things the most and improved the turn in side of things more than corner exit. This was despite running fresh 215 fronts as opposed to nearly 5 year old 205's that I had on the front last time with the stiffer front bar. Also after the back straight when you'd nail the brakes after being in 4th gear I struggled to trun in accurately there and kept missing the apex - is that because the braking compression had used up all the damping bump time and when I went to turn in I was just too soft in the front, cos it felt like it?
So when the best solution turned out to be setting the front dampers to their absolute max setting, is that saying that I was benefitting from the initial extra bump (I could get it turned in well enough) but then the damper couldnt maintain that extra bump through to corner exit and points to the need to go stiffer with roll reasistance at the front again? Given that the dampers went best maxxed out though I'm guessing doing it with a jump in spring rate from 7kg/mm to 8kg may not be on the cards since I seem to be running out of front damper adjutment? So go back to the Whiteline 22mm front bar? The only reason I baulk at that is that it rides ****ty hillclimb surfaces much better on the soft bar than it did on the stiff one. Seems to upset the wavetrac diff less, but then again the plate diff will be going in soon anyway.
In an ideal world I'd buy some Bilsteins but dollars are in non-supply so I need to find the best setup that works around the existing MCA's.
anyway, any advice welcome cos not sure if I need mostly better front dampers, stiffer front springs or go back to the stiffer front bar?

[seangti]

[sambb]

cool. that looks fun. How does it go compared to the equiv RWD and AWD cars on such a tight circuit?

[Sydneykid]

Thanks Sean. I'll put up a vid a bit later. I accidentally left the GoPro running and used up all the cards space so I'm left with a giant vid that needs editing and not much actual track footage.
Question for Gary..... So I'm in a bit of a bind as to what to do about the front end. As I said this was the first time i've run up to temp semis with the softer/standard front bar on a circuit. While it was great for cold tyre runs in hillclimbs it did feel like it was overloading the outside front and I was finding it harder than usual to get good hard drive off the corners and was missing apexes.
You've mentioned in the past that if for instance you use bump adjustment in dampers to 'add' roll stiffness, that it will only help initially but then the front will progressively give up the longer the loads last for. Well I definitely found that.
For example the left hander that goes up the hill in front of the pit straight, I would turn in and it would do so nice and sharp and the back would rotate nicely but then the longer I'd move through the corner and really needed to be getting on the throttle, it'd start to understeer out wide. Good initial response but then the front right felt like it was getting buried the further I moved through the corner. Adding rear damper helped a bit, but it felt like it was a front issue and maxxing the front dampers changed things the most and improved the turn in side of things more than corner exit. This was despite running fresh 215 fronts as opposed to nearly 5 year old 205's that I had on the front last time with the stiffer front bar. Also after the back straight when you'd nail the brakes after being in 4th gear I struggled to trun in accurately there and kept missing the apex - is that because the braking compression had used up all the damping bump time and when I went to turn in I was just too soft in the front, cos it felt like it?
So when the best solution turned out to be setting the front dampers to their absolute max setting, is that saying that I was benefitting from the initial extra bump (I could get it turned in well enough) but then the damper couldnt maintain that extra bump through to corner exit and points to the need to go stiffer with roll reasistance at the front again? Given that the dampers went best maxxed out though I'm guessing doing it with a jump in spring rate from 7kg/mm to 8kg may not be on the cards since I seem to be running out of front damper adjutment? So go back to the Whiteline 22mm front bar? The only reason I baulk at that is that it rides ****ty hillclimb surfaces much better on the soft bar than it did on the stiff one. Seems to upset the wavetrac diff less, but then again the plate diff will be going in soon anyway.
In an ideal world I'd buy some Bilsteins but dollars are in non-supply so I need to find the best setup that works around the existing MCA's.
anyway, any advice welcome cos not sure if I need mostly better front dampers, stiffer front springs or go back to the stiffer front bar?

The corners on that circuit layout are long enough to "G force" through the damper's increase in bump rate. Keeping in mind that the rebound damping will most likely increase (as you adjust) between 2 and 3 times as much as the bump damping. So that will tend to hold the front down (compressed springs) for longer. It's why we use dampers with separate bump and rebound adjustment. We can add bump damping to compensate for slightly too soft spring rate or not enough anti roll.

Without that you're stuck, so you either have to up the spring rate or the anti roll rate. Going from 7 to 8 kg/mm may well be enough and for the front of a FWD car it's almost always the better choice as it doesn't tend to lift (unload) the inside wheel (more) as happens with more anti roll does. That's around 350 lbs/inch at the tyre, which is close to the upper limit for A050's in 15" or 16".

I wouldn't be concerned with insufficient damping, as per above, the rebound damping increases 2 to 3 times as much with adjustment. Plus, being hydraulic devices dampers are velocity sensitive, so they dampen more as the speed increases. Which is what an increased spring rate does, makes them rebound faster. As a result they will "self adjust" to some extent.

The question is can you stand that spring rate on a daily basis?

Cheers
Gary

[sambb]

What you describe is exactly what it felt like turning left into the chicane at the end of the back straight. The car nose would compress down under hard braking and it felt like it stayed there when I'd turn in. I kept missing that apex which was then costing me through the chicanes and onto the pit section. It didn't help that it was really wandering around under brakes there too.
Glad that it sounds like I wont have 'run out' of damping adjustment. Im quite happy to try out 8kg fronts for science and also because I'd rather do that job than wrestle a bar in/out of the subframes which is a complete PITA on my car. Poor kids.... they cant get a drink bottle or any food into their mouths when they are in my car, its just too jiggly, but they enjoy the ride!
So is a progressive rate front spring not on the cards? Slightly softer at turn in and then hardens up under extended G loads. I imagine it'd make it more difficult to set up the dampers for a spring like that with 2 way/fast and slow but is that something to consider for my setup, or is linear the way?

[seangti]

cool. that looks fun. How does it go compared to the equiv RWD and AWD cars on such a tight circuit?

This event had mostly trailered race / road rally style cars on slicks, a few street cars and a handful of Excels/Accents. My best was 57.1s. A Focus RS who was fastest attendee last round did a best of 55.9. Fastest of the day by a long shot was a mental R35 on slicks doing a 51, next best was a 54, then a handful of 55's. I was a top 10 / top 1/3 (30 odd entrants).

This is my second time running in this event. First back in March was stinking hot and my best time was a 57.4. I'm now chasing a 56, just not exactly sure how/where to clean up my lines to get it. Those video's were runs in the high 57 / low 58's. From dirt on track to over driving, i had to regroup and focus on smooth, and was back into mid/low 57's again.

I'm still on the same Federal RSRR's tyres as last year as I haven't tracked much of late and don't drive it much as I've bought a better suited daily driver.

[sambb]

I think you've probably seen my vids of the Ringwood Hillclimb circuit which has corners as tight as yours. The main thing that helped there was as much rear roll stiffness as possible ie springs or bar. You could also run the rear a tad higher to get its roll centre up and pump up the rears so it'll rotate a bit more. Should help you in being able to get on the power earlier.

[Sydneykid]

What you describe is exactly what it felt like turning left into the chicane at the end of the back straight. The car nose would compress down under hard braking and it felt like it stayed there when I'd turn in. I kept missing that apex which was then costing me through the chicanes and onto the pit section. It didn't help that it was really wandering around under brakes there too.
Glad that it sounds like I wont have 'run out' of damping adjustment. Im quite happy to try out 8kg fronts for science and also because I'd rather do that job than wrestle a bar in/out of the subframes which is a complete PITA on my car. Poor kids.... they cant get a drink bottle or any food into their mouths when they are in my car, its just too jiggly, but they enjoy the ride!
So is a progressive rate front spring not on the cards? Slightly softer at turn in and then hardens up under extended G loads. I imagine it'd make it more difficult to set up the dampers for a spring like that with 2 way/fast and slow but is that something to consider for my setup, or is linear the way?

What you could also be experiencing is bottoming out on the bump stops, which results in savage increase in the effective spring rate (what the tyre feels). It could go from 7 kg/mm to 30+ kg/mm depending on the bump stop design. It feels like turn, grip, roll, grip, roll some more, grip, roll some more, then the roll stops and it washes out. We run fairly progressive bump stops, but even they jump from, ~15 kg/mm to ~30 kg/mm in 10 mm or so of travel.

Can't remember if I suggested it before, but just in case, on cars without suspension travel data recording I use cable ties (tight) on the shock shafts to show the maximum travel. Just jack it up after a run and see where the cable tie ended (pushed) up on the shock shaft. If it's getting severe bump stop contact the cable tie will be embedded up into the bump stop. Worth trying.

True progressive rate springs are hard to tune the dampers for because they change rate with even a small amount of travel. Some fairly sophisticated valving is required. Most progressive springs aren't really progressive at all, they have a few sacrificial coils that bottom out just from the weight of the car. So they run at high rate all the time while driving.

Cheers
Gary