Blyton Track Day 15th April

[stylussprinter]

Rob (Stylussprinter)18st is near enough 250lbs, the damper/ wheel ratio on a Stylus is near enough 1:1 all round so 250 lbs is enough to depress one of his rear springs by 1" or both by 1/2"so even allowing for the majority of the drivers weight being distributed over the rear wheels I wouldn't expect the ride height to change by more than about the 3/8" (10mm) Rob (CMA) is seeing.

If the front feels nicely planted and the rear loose then softer and or lower at the rear is the way to look. Did I read right that you have 250lbs all round? most people seem to run the front about 10%-20% harder than the rear so it might be worth looking at 200 or 225lbs for the back.

Bikenuts

You haven't twigged my own spec -- springs250lbs/own weight 81kgs/spring deflection 15mm's----- which is ' actual ' figures. These advised settings etc come from 12 yrs competition and continuous testing. If my weight on those spring lbs deflects 15mm's in my 600kgs car ---- there has to be another explanation for his figures , particularly as his Stylus may well weigh more

I started off 12 yrs ago with the exact same spec as every body else 180lbs front 130lbs rear and AVO 13/90's shocks on 9inch springs. The factory then very slowly caught up with my development of moving through 200 , 225 , 250 then 285lbs fronts and ARB. Same at the rear , 180 , 200 , 225 , 250lbs plus testing '' rake '' to control balance --- all for my car and my weight , measured by my lap times at various tracks for 12 to 15 events per year .
The factory only changed to dipped rear links after Tim arrived and convinced Pete of the real cause for rear links bending ---- me having said the same for years before ie. piston travel/shocks not enough.(but then Tim could drive )
Point I'm making is that my advice to others isn't theoretical -- it comes from a lot of work and money spent finding out. If I can help people to avoid that process , especially if they don't compete , then I'm pleased to do it.

[CMA]

You haven't twigged my own spec -- springs250lbs/own weight 81kgs/spring deflection 15mm's----- which is ' actual ' figures. These advised settings etc come from 12 yrs competition and continuous testing. If my weight on those spring lbs deflects 15mm's in my 600kgs car ---- there has to be another explanation for his figures , particularly as his Stylus may well weigh more

Surely the weight of the car is irrelevant in this test. The only difference is in the deflection of a 250lb spring with your weight in it of 15mm and a 250lb spring with my weight in it of 10mm. The fact the car weighs 600kgs or 650kgs would not make any difference to the amount the height changes with my additional weight?

PS for reference I don't run the dipped arms just straight ones. Could this have an impact if Rob (Stylussprinter) is running dipped?

[stylussprinter]

You haven't twigged my own spec -- springs250lbs/own weight 81kgs/spring deflection 15mm's----- which is ' actual ' figures. These advised settings etc come from 12 yrs competition and continuous testing. If my weight on those spring lbs deflects 15mm's in my 600kgs car ---- there has to be another explanation for his figures , particularly as his Stylus may well weigh more

Surely the weight of the car is irrelevant in this test. The only difference is in the deflection of a 250lb spring with your weight in it of 15mm and a 250lb spring with my weight in it of 10mm. The fact the car weighs 600kgs or 650kgs would not make any difference to the amount the height changes with my additional weight?
Correct , but I was also commenting to the ' poster ' on how much piston room was available during weight transfer ie. cornering --- which was where you and I started this thread.

PS for reference I don't run the dipped arms just straight ones. Could this have an impact if Rob (Stylussprinter) is running dipped?

Only if you run out of piston travel , hence my caution on just advising you to lower the ' rake ' as Matt/previous poster has done . This , if the real problem was actually lack of piston travel under cornering , would make it even worse plus could be very dangerous(the shocks become momentarilly solid items/no suspension at all)

The dipped arms allow a longer shock and still be able to lower the car ---- and longer shocks have longer piston travel which gives you more room to play with set-up.

[CMA]

Quite interesting all this

So 2 issues here then:

Why does my spring only deflect 10mm compared to your 15mm? I will be reassembling and double checking my deflection.

And if I lower my ride height to get 10mm of rake I will be lowering the rear by 12mm this would mean there is 48mm of shock travel left without me in it. And assuming it all still drops 10mm when my fat ass gets in then this would leave 38mm of suspension travel.

Would you say 38mm is enough?

Or perhaps I need to get these dipped arms and longer shocks/springs to achieve what I need...

[stylussprinter]

Quite interesting all this

So 2 issues here then:

Why does my spring only deflect 10mm compared to your 15mm? I will be reassembling and double checking my deflection.
This is the first most important question

And if I lower my ride height to get 10mm of rake I will be lowering the rear by 12mm this would mean there is 48mm of shock travel left without me in it. And assuming it all still drops 10mm when my fat ass gets in then this would leave 38mm of suspension travel.

Would you say 38mm is enough? This is not relevant until the above question is answered --- I don't believe you would only deflect the rear springs 10mm's if all is as you say plus shocks are ok

Or perhaps I need to get these dipped arms and longer shocks/springs to achieve what I need...

Don't spend any money until the root cause is clear

It's a great shame you're so far from me or I'd sort it for you

[pigeondave]

Quite interesting all this

So 2 issues here then:

Why does my spring only deflect 10mm compared to your 15mm?

Could it be that the initial valving is harder than Robs? I believe that you can get the shocks built with different valves and then you are able to adjust.

http://www.neileverett.madasafish.com/m ... ampers.htm

The last paragraph says about the valves

[CMA]

Interesting reading, and mentioned in that article is the "droop" or amount the axle drops ("Rebound Travel") .

I looked at mine the other day and I jack the car up on the diff housing and then axle stand it under the chassis. When removing the jack the axle only drop 10-15mm before it sits on the panhard rod (not measured exactly yet). Could this be having an impact on the suspension travel?

[pigeondave]

When removing the jack the axle only drop 10-15mm before it sits on the panhard rod

Dude, this doesn't sound right.

I was going to have that problem if i fitted the adjustable panhard rod that Rob made me. For now its sitting on the shelf until i can get round to doing this

download/file.php?id=621&mode=view

form this thread
viewtopic.php?f=15&t=818&p=6717&hilit=+panhard#p6717

Im not a big enough geek to get the image to display correctly so I posted the URL

[CMA]

Oooooo that would be a nice mod to make. Shame I don't have the skill to make something like that

[pigeondave]

Now, im not too sure but I think that lowering the panhard rod in this way affects the roll centre at the rear.

If you'd like to get into the geometry this is an interesting read.
http://www.super7thheaven.co.uk/

http://www.super7thheaven.co.uk/Glossary

and his blog is interesting too.

Sorry for taking this off topic.

[Bikenuts]

Rob (CMA) are your dampers Topped out without you in the car? I ask because if you have no initial sag from the weight of the car some of your weight may be overcoming the pre-load before the suspension starts to compress.

Dropped a bollock in my previous post; the dampers are mounted part way along the bottom arms so the leverage ratio is more like 5:4 - 5mm at the wheel will only compress the damper 4mm so a 250 lb inch spring will give a wheel rate of 200lbs inch so CMA's figurer of 10mm does seam a little low - see above for a possible cause.

The other Matt D's solution for lowering the panhard rod mount is worth looking at; viewtopic.php?f=15&t=818

[stylussprinter]

Rob (CMA) are your dampers Topped out without you in the car? I ask because if you have no initial sag from the weight of the car some of your weight may be overcoming the pre-load before the suspension starts to compress.

Dropped a bollock in my previous post; the dampers are mounted part way along the bottom arms so the leverage ratio is more like 5:4 - 5mm at the wheel will only compress the damper 4mm so a 250 lb inch spring will give a wheel rate of 200lbs inch so CMA's figurer of 10mm does seam a little low - see above for a possible cause.

The other Matt D's solution for lowering the panhard rod mount is worth looking at; viewtopic.php?f=15&t=818

That's a ' mod ' that Tim Benbow did on the factory car with me following suit (2003) --- I then described it with measurements for Matt to do the same. The idea being , not giving the car a helping hand shifting the body across the axle during lefthand cornering with the chassis pick-up being higher than the axle pick-up. As a bonus the Panhard doesn't contact the drive line.

[CMA]

Rob (CMA) are your dampers Topped out without you in the car? I ask because if you have no initial sag from the weight of the car some of your weight may be overcoming the pre-load before the suspension starts to compress.

I will drop the panhard off after reassembly and check the drop without it. I think from memory the panhard is stopping it dropping as much as it could.

Ideally I would love PeteC's panahard mod but my welding skills are not to be trusted on critical suspension parts so thats a no go (unless someone with more skill would like to?).

[DH2]

Ideally I would love PeteC's panahard mod but my welding skills are not to be trusted on critical suspension parts so thats a no go (unless someone with more skill would like to?).

Rob, just fabricate it yourself, tack it together, then take it to local engineering shop or get a mobile welder to weld it up for you.

Dave

[stylussprinter]

Rob/CMA , I could make you an adjustable Panhard(in fact got one in stock made but cancelled) and make a bracket to be welded to the underside of the passenger seat very far left corner (as the '' Tim '' factory mod I did ) Car needs to be on a ramp for part of the welds BUT I pop rivetted the small bracket in place with a very fat rivet , just to hold it in place for easy welding then welded the outside short weld before getting underneath to do the other 3 short welds.
PM if that will help