Rear suspension droop/Travel/shock length?

[JamesH]

Originally Posted by Al Weyman

No not allowed at all the mods they did, they were Group 2 ours are Group 1 based or Group N. What happened to my link? Here it is again. http://www.youtube.com/watch?v=XC4p74p65YA Caltracs are for drag racing and IMHO would hurt the cornering even more. As I said it doesnt tramp off the line anyhow.

Looks like you have to use the Force to keep that on the track in left handers!

There was one bit that looked very odd though - braking for Maggots, it looked like the back of the car bounced up and down a bit - was the axle winding up and unwinding? (the opposite of tramp under acceleration?).

Anyway, it looks much worse in left than right handers as you said (although it looked twitchy round Luffiend as well), like the grip was just turning on and off. Does look like you are hitting the end of a travel range somewhere.

[Lancsbreaker]

Having viewed that clip it is obviously really wayward on right-handers....which given that most of our tracks are run clockwise is something of an issue....

Wouldn't be at all surprised if your right-hand rear shock is lifting the rear wheel - even if only slightly, you'd lose grip, so your planned mod will be good enough to check the theory, although having the shocker pivot above the axle line isn't ideal. I'm sure you could get shockers of the correct length for your required ground clearance and axle articulation but valved to the required damping.

BTW - I reckon if the Beemer driver had engaged second at the right time the first time he passed you, rather than when he was 3/4 of the way through the corner he'd have left you then

[Al Weyman]

Nah I can out power the CSL no problem, we usually swap around who finishes in front it was his day this time! I have done the mod and it looks good, I now have three inches drop and the leaf spring reaches its lowest point and I still have about half inch of travel left in the shock. I have also lowered the right rear (viewed from behind) down 10mm as it was high when I was sitting in the car. iit may effect it worse on left handers but as has been said its predominately right handers we have to deal with. Funny enough I couldnt find any shockers longer than the 23" fully extended Koni's infact most were shorter. This is the yankee solution to the problem probably more for drag racing but I didnt fancy it and recon the bolts look prone to bend or rip out http://www.summitracing.com/parts/MRG-1290A/

Here is my solution.

[GORDON STREETER]

Originally Posted by Al Weyman

Here is my solution.

Got a few pigeons around there Al

[Al Weyman]

It may not be pretty but its strong Gordon trust me the whole thing is 1/4 plate! And the shocker sits in there lovely.

[Chris Wilson]

It's DEFINITELY not pretty It CERTAINLY looks hefty

[Al Weyman]

My car is so close to the minium weight I may as well beef it up than carry ballast! I could have made it look prettier with a grind but whats the point it is only weakening the weld and no one is gonna see it! Its a race car not a show car.

[Chris Wilson]

He says, publishing a photo of it on the `net No excuses now, that's awful, and hanging ballast on the axle is not the "normal" way (or is that weigh...) to do it....

[Al Weyman]

Its not awful at all, Ok I get a hand grinder and clean it up a bit and paint it matt black is it going to go any faster, no of course not. The bloody car weighs so heavy and I have to meet a huge and somewhat unfair minimum weight on the thing because its 5700cc so what the heck, a little extra unsprung weight will make sod all difference you or I would never notice it and thats a fact, a shocker lifting a wheel however will and I would rather something overkill that wont break than the extended stud idea which to me looks like those old wheel spacer kits without the spacer! You obviously never worked on Stock Cars lol! Anyhow on its day it can still show 100k's worth of CSL a clean pair of heels and should be even better now. .

[phoenix]

Originally Posted by Al Weyman

Its not awful at all, Ok I get a hand grinder and clean it up a bit and paint it matt black is it going to go any faster, no of course not. The bloody car weighs so heavy and I have to meet a huge and somewhat unfair minimum weight on the thing because its 5700cc so what the heck, a little extra unsprung weight will make sod all difference you or I would never notice it and thats a fact, a shocker lifting a wheel however will and I would rather something overkill that wont break than the extended stud idea which to me looks like those old wheel spacer kits without the spacer! You obviously never worked on Stock Cars lol!

Al, looking at the Silverstone video it obviously wasn't clear that the inside rear was being lifted from the track, buut it is obviously a possibility and what you gave done to correct the problem is a good thing (whether it's pretty or not is not so important!).

However, the rear did look a bit high, which I see you have corrected as part of your latest mods, and it also looked like it might be a bit too stiff compared to the front. The other thing I thought was maybe the diff is working in a strange way - locking/releasing - giving the 'threepenny bit' effect. I can certainly see why you don't like hairpins! Being able to steer on the throttle to effect a nice smooth, controllable powerslide like in the Baby Bertha picture in the 'hairpin' thread is what you are after. If the car is too stiff at the rear - or too soft at the front since upgrading the rear springs - you maybe have too much oversteer in the chassis to be able to achieve that.

I guess once you have tried/tested the latest mods you have done you will know whether you have effected a cure or if some of these other possible causes need investigating.

[Al Weyman]

Funny you should say that a friend of mine who races a very powerful SD1 asked me if I can steer by the throttle and the fact is I can't it will either push on when I apply power or it will just break at the back and spin, a smooth transition and holding it on the throttle is very hard to achieve. My mate was convinced the travel problem is not helping at all and reckons on 4" either way on the big Rover.

BTW he also reckoned my 1.25" front anti roll bar with 850lbs springs is massively over the top so I am trying a 15/16th bar next race. The front suspension is double wishbone so the 850 will not be 'seen' as the actual rate, in the states there is two opposing schools of thought on tuning these beasts one goes with heavy springs and lighter bars the other the opposite, I had both lol!

Funny enough I checked out the rear spring poundage as best I could and it wasnt that high, about 250 I think. Maybe it has the 'Nova' Arch problem, I think I may get the springs re-arched in the close season.

[phoenix]

How would you describe the balance when you are off the power in a reasonably high speed corner - oversteer/neutral/understeer?

[Al Weyman]

Cant really think of many corners like that to be honest. it tends to be better on high speed sweeping circuits like Donny where i put it on the 2nd row with a lot of opposition in the race.

[GORDON STREETER]

I can see why phoenix is asking the questions Al. Some cars because of their design will always handle better than others, a neutral handling car will always be best and with the best power should win.
Has the car ever handled any sense ? and is it worse now than it ever was ?
It's all about compromise as its difficult to make a car really good on slow and fast corners. Going to a smaller front bar will IMHO make it too "oversteery" and nervous to drive. You really need adjustable bars back and front and do a trackday to sort it out, a bad handling car is not a pleasure to drive in a race as you don't know what it's going to do next !

[phoenix]

Originally Posted by Al Weyman

Cant really think of many corners like that to be honest. it tends to be better on high speed sweeping circuits like Donny where i put it on the 2nd row with a lot of opposition in the race.

OK - doesn't tell me much. I was thinking Coram for example.

How about if you go into a corner a bit too fast and still try to hit the apex. Does it understeer or oversteer? Or should I say, does does it push or is it loose

p.s. is there anywhere on the net I can see some pics of your car in action from trackside? It might be useful if I could see some.

[Al Weyman]

Coram, not bad as it happens. can tend to get loose at the rear when pushed hard through there though, definitely not understeering through there. I have some incar somewhere.

[Al Weyman]

Here is a bit through Coram you can see its very twitchy at the rear. http://www.youtube.com/watch?v=eHoNruUTLtA

[Al Weyman]

Right I have cured that problem now I can see a further one, the rear A/R bar is holding up the axle now so I am going to have to modify the mounts big time or take it off which I am sorely tempted to do.

[Casper]

Leaf springs, that brings back memories. I tried something many years ago and it seemed to work. We took a leaf out of the middle, turned it upside down and put it on top and bolted the whole lot back together. The car got lowered and the spring rate went up and it all seemed to work. Back then if it was cheap we did it, mind you we only had the seat of the pants to tell us if it worked as we didn't race.

[phoenix]

Originally Posted by Al Weyman

Right I have cured that problem now I can see a further one, the rear A/R bar is holding up the axle now so I am going to have to modify the mounts big time or take it off which I am sorely tempted to do.

Definitely go for the softer front bar if you take the rear one off.

For the next event, can you mount the in-car camera more rigidly? It appears to be moving up an down making it difficult to interpret the actual chassis movement - unless the bonnet does go up and down like it appears to in the videos!

Also a wider angle, showing the full front screen width and the steering wheel would be good.

From the in-car videos I have watched I reckon you must be pleased every time you get the car back to the paddock in one piece - the handling looks evil!

Get the handling sorted and I think you could have won the race at Brands that I watched.

[Chris Isaacs]

Al, re. the diff behaviour - are you running a posi (clutch-type) diff, cone-type, or a locker-style one? If it is a posi, are you using straight LSD oil, or do you also use the GM additive with it?

[Al Weyman]

Posi diff with additive.

I have ended up taking of the rear bar altogether, winding another degree neggie on the front and was horrified to see I was toeing out over 1/4" something that may been the result of the crash at Lydden and wasnt checked so I set that parrallel.

Well i did three laps of Brands today in the Historic Touring car parade at the BTCC and hung back a bit so I could give her some stick and the car seems a totally different animal and felt really good and I was able to comfortable steer it on the throttle in a nice controlled fashion. I have some incar and will post it here as soon as I process it but I was very pleased with my work. The session is not fully representive as it ended so soon and was behind a pace car and i didnt want to make myself look a total pratt and go off in front of the 40,000 capacity crowd but it just felt so much better. I dunno whether to feel sick I have raced the thing off and on for 21 years or happy that at last I may have found something, I think I will settle for the later!

[GORDON STREETER]

Originally Posted by Al Weyman

Posi diff with additive.

I have ended up taking of the rear bar altogether, winding another degree neggie on the front and was horrified to see I was toeing out over 1/4" something that may been the result of the crash at Lydden and wasnt checked so I set that parrallel.

Did you check the tracking before giving it more negative camber ?

[Al Weyman]

Visually it look wrong before I altered camber and yes i agree altering the camber would have increased the tow out as the steering is before the axle line, it probably was'nt as badly out as what I suggested but I am pretty sure even with an eyeball it was not right, and nice to see you and your mates at Brands yesterday again Gordon, the old girl felt absolutely transformed in the demo laps, a totally different animal. Its staying on the trailer untouched for the long drive down to Pembrey next weekend, lets see how it goes in a race.

[Chris Wilson]

Surely adding negative camber with the steering arms in front of the hubs would add toe in?