Like Tree14Likes

Droop

Old 10-26-2017, 08:46 AM
  #16  
Tech Regular
Thread Starter
 
dvaid852456's Avatar
 
Join Date: Aug 2010
Posts: 372
Default

Originally Posted by snuvet75
Maybe this is the most important aspect we never listen to
Must go faster!!!

Great replies by everyone - thanks!

I'm starting to understand the theory better now and I think I have it sussed why reducing front droop takes away front grip. Due to the unladen inside tyre losing grip by lifting and the outside tyre not receiving 100% of the additional grip due to negative side effects of weight transfer.

Roll is a result of weight transfer.

The amount of weight transfer is determined by CG height, track width, and weight of the car.

The only point (or so I believe) I am still stuck on is..... why does the Hudy setup guide and others advise to INCREASE front droop to increase weight transfer to the rear under acceleration, increasing F to R roll to increase rear grip under acceleration thus reducing over-steer. Yet the opposite is in fact true?

Is it because I am simply cornering too fast and cocking a wheel and that aspect of REDUCING front droop takes precedence over the effect of weight transfer to the rear. If I was to corner slower and not lift the inside wheel would, as the setup guides say, increasing front droop give more rear grip?

Years ago I used to struggle with my HB Cyclone on carpet and found the only setup cure to over-steer was to increase rear droop by changing the down stop setting from 6mm to 3mm. Simply so when I was cornering the inside rear wheel would not lift. This went against all setup guides as increasing rear droop should only affect FRONT grip under braking.

It does seem droop settings have more of an effect on the end you alter than the opposite end as many setup guides state.
dvaid852456 is offline  
Old 10-26-2017, 09:55 AM
  #17  
Tech Master
iTrader: (16)
 
snuvet75's Avatar
 
Join Date: Apr 2011
Posts: 1,589
Trader Rating: 16 (94%+)
Default

Originally Posted by dvaid852456
Must go faster!!!

Great replies by everyone - thanks!

I'm starting to understand the theory better now and I think I have it sussed why reducing front droop takes away front grip. Due to the unladen inside tyre losing grip by lifting and the outside tyre not receiving 100% of the additional grip due to negative side effects of weight transfer.

It may or may not happen. It's all dependent on your rest of the set up and how much droop you put in relation to your car's corner speed and lateral force. It is all about finding balance between setting parameters.


The only point (or so I believe) I am still stuck on is..... why does the Hudy setup guide and others advise to INCREASE front droop to increase weight transfer to the rear under acceleration, increasing F to R roll to increase rear grip under acceleration thus reducing over-steer. Yet the opposite is in fact true?

The opposite it NOT true. More front droop means the front will lift more on acceleration, right? Hence more weight is transferred to the rear meaning more grip in the rear (understeer).


Is it because I am simply cornering too fast and cocking a wheel and that aspect of REDUCING front droop takes precedence over the effect of weight transfer to the rear. If I was to corner slower and not lift the inside wheel would, as the setup guides say, increasing front droop give more rear grip?

again it's all about balance. It's easy to say but it takes time and experience. Overdoing it is very easy.

Years ago I used to struggle with my HB Cyclone on carpet and found the only setup cure to over-steer was to increase rear droop by changing the down stop setting from 6mm to 3mm. Simply so when I was cornering the inside rear wheel would not lift. This went against all setup guides as increasing rear droop should only affect FRONT grip under braking.

This is why people say different things all the time. Speaking from their experience. It doesn't mean they are all right. Bad set up can be compensated by making another bad change. No I should say bad set up can be masked by making another bad change. The true way is to understand what does what from proven experts and see bigger picture. Yet I'm still talking lol.

It does seem droop settings have more of an effect on the end you alter than the opposite end as many setup guides state.

May or may not be true like I said above. If you overdid it, then yes.
If you did it just right, not true and you will have the desired effect that the book says.
see above.
snuvet75 is offline  
Old 10-26-2017, 12:58 PM
  #18  
Tech Addict
 
Join Date: Mar 2002
Location: New Zealand
Posts: 609
Default

People have all these theories about roll and weight transfer etc which may or may not be correct, but the simple fact is, less rubber on the road less grip at that end. This happens when the inside wheel suspension arm hits the stop.

An exagerated example is a motorcyclist doing a stoppie. The rear droop setting had no effect on the front end.

Another example is a top fuel dragster lifting a wheel under acceleration. The front droop setting had no effect on rear traction.

Last edited by ixlr8nz; 10-26-2017 at 01:14 PM.
ixlr8nz is offline  
Old 10-26-2017, 02:47 PM
  #19  
Tech Master
iTrader: (16)
 
snuvet75's Avatar
 
Join Date: Apr 2011
Posts: 1,589
Trader Rating: 16 (94%+)
Default

Originally Posted by ixlr8nz
People have all these theories about roll and weight transfer etc which may or may not be correct, but the simple fact is, less rubber on the road less grip at that end. This happens when the inside wheel suspension arm hits the stop.

An exagerated example is a motorcyclist doing a stoppie. The rear droop setting had no effect on the front end.

Another example is a top fuel dragster lifting a wheel under acceleration. The front droop setting had no effect on rear traction.
I don't see why you mention droopie and wheelie as they have nothing to do with droop setting just like you said yourself.
snuvet75 is offline  
Old 10-26-2017, 04:22 PM
  #20  
Tech Addict
 
Join Date: Mar 2002
Location: New Zealand
Posts: 609
Default

Those are the two most obvious examples that show droop has no real effect on weight transfer front to rear.

The only real argument to go against this, is the fact that the suspension becomes unsprung weight when the droop stop is hit and a wheel is lifted. This is however generally very light in comparison to the car weight, so the effect would be minimal.

back to the subject, a rear wheel lifted can really make a car really hard to drive on a high speed corner. Of course the type of diff/car you have also makes a difference to how it reacts.
ixlr8nz is offline  
Old 10-26-2017, 07:00 PM
  #21  
Tech Master
iTrader: (15)
 
BadSign's Avatar
 
Join Date: Feb 2002
Location: Franklin, IN
Posts: 1,267
Trader Rating: 15 (100%+)
Default

Originally Posted by dvaid852456


Years ago I used to struggle with my HB Cyclone on carpet and found the only setup cure to over-steer was to increase rear droop by changing the down stop setting from 6mm to 3mm. Simply so when I was cornering the inside rear wheel would not lift. This went against all setup guides as increasing rear droop should only affect FRONT grip under braking.
You have to remember that droop also affects from side to side as well as front to back. By giving the rear more droopl, you allowed that wheel to stay on the ground and maintain some traction. When you're in the middle of a corner, droop is affecting front-rear roll and side to side as well.

If you don't have it, go buy a copy of "Tune to Win", it will explain a tremendous amount.
snuvet75 likes this.
BadSign is offline  
Old 10-26-2017, 07:58 PM
  #22  
Tech Regular
iTrader: (21)
 
two shoes's Avatar
 
Join Date: Dec 2015
Location: Rockies
Posts: 255
Trader Rating: 21 (100%+)
Default

Originally Posted by BadSign
If you don't have it, go buy a copy of "Tune to Win",
Going to look this up...
two shoes is offline  
Old 10-26-2017, 11:01 PM
  #23  
Tech Master
iTrader: (16)
 
snuvet75's Avatar
 
Join Date: Apr 2011
Posts: 1,589
Trader Rating: 16 (94%+)
Default

Originally Posted by BadSign
You have to remember that droop also affects from side to side as well as front to back. By giving the rear more droopl, you allowed that wheel to stay on the ground and maintain some traction. When you're in the middle of a corner, droop is affecting front-rear roll and side to side as well.

If you don't have it, go buy a copy of "Tune to Win", it will explain a tremendous amount.
Didn't bother to mention it. Well said.
snuvet75 is offline  
Old 10-27-2017, 02:15 AM
  #24  
Tech Elite
 
Skiddins's Avatar
 
Join Date: Feb 2006
Location: Windsor, UK
Posts: 4,952
Default

I don't think the dragster example is very good at all, they have huge power to weight ratios and (comparatively) all the weight is at the back to begin with.

Think of an 'average' road car, from standstill if it pulls away hard the front will lift up (more so if it's FWD) and dive when braking. This is the weight transfer in action.
The front will keep trying to lift until there isn't enough downward force on the tyres to produce traction and it either wheel spins or the traction control cuts in.
Sportier versions, sometimes of the same model of car, will come with harder front and rear suspension which help to reduce this transfer.

As they don't have adjustable droop, the dampers and springs are tuned to changed the transfer. We have the benefit of set screws in the wishbones so we can separate some of the this transfer from having to change the springs etc.
Obviously we use a combination to allow us to tune the car for all area's of the track.

Another reason you may loose rear traction with more front droop is that the camber gain at the rear (and/or combined with what the camber was to begin with) is too great and as the rear compresses down to contact patch of the rear tyres is reduced.

Sometimes simply reducing the static rear camber can increase rear traction.

As every setup guide and book keeps telling us, you cannot make a setup change without it, in turn, having an effect on another setting. We're trying to find that ultimate sweet spot for our cars, for each track in each condition.
Skiddins is offline  
Old 10-27-2017, 03:11 AM
  #25  
Tech Elite
iTrader: (1)
 
Join Date: Sep 2010
Location: My house.
Posts: 3,569
Trader Rating: 1 (100%+)
Default

My 0.02€.

As someone rightly wrote, weight transfer only depends on CG height, track width (or wheelbase if you are calculating braking and acceleration) and acceleration (speed a that moment). Having no suspension doesn't matter to weight transfer, it's the dragster example. That car uses the weight transfer of everything past the engine to help plant the rear tires. That length is tuned so it barely lifts the front wheel (zero weight on the front wheels,everything on the rear) but not so much the car is upset aerodynamically (front pointing up) or has to ride on the wheelie bar adding another point to take load of the rear tires.

More droop means more chassis motion which can be good up to a point, different droop front-rear means one end will provide more weight to the other, the one with more droop of course.

Droop is good that doesn't make the suspension stiff during most of the travel. Have you imagined your 1:1 car ridding on the bump stops every turn?
30Tooth is offline  
Old 10-27-2017, 03:49 AM
  #26  
Tech Regular
Thread Starter
 
dvaid852456's Avatar
 
Join Date: Aug 2010
Posts: 372
Default

Thanks for replying snuvet75 I really appreciate the input.

"May or may not be true like I said above. If you overdid it, then yes.
If you did it just right, not true and you will have the desired effect that the book says."

I started with JJ Wang's carpet setup which is not a million miles from the standard TCXX carpet setup. This had 8.75mm front down stop setting. I only increased this to 9.5mm and saw a reduction in over-steer, 9.5mm is often used by Team drivers according to online setup sheets so I don't think it is overdoing it.

I just wonder if the setup theory is fine for full size cars but perhaps with model cars due to the much faster cornering speeds it doesn't always apply 100% of the time?

I will have a play and try increasing front droop but I'm pretty sure it will make the over-steer worse or not reduce it.
dvaid852456 is offline  
Old 10-27-2017, 03:55 AM
  #27  
Tech Regular
Thread Starter
 
dvaid852456's Avatar
 
Join Date: Aug 2010
Posts: 372
Default

Originally Posted by 30Tooth
My 0.02.

As someone rightly wrote, weight transfer only depends on CG height, track width (or wheelbase if you are calculating braking and acceleration) and acceleration (speed a that moment). Having no suspension doesn't matter to weight transfer, it's the dragster example. That car uses the weight transfer of everything past the engine to help plant the rear tires. That length is tuned so it barely lifts the front wheel (zero weight on the front wheels,everything on the rear) but not so much the car is upset aerodynamically (front pointing up) or has to ride on the wheelie bar adding another point to take load of the rear tires.

More droop means more chassis motion which can be good up to a point, different droop front-rear means one end will provide more weight to the other, the one with more droop of course.

Droop is good that doesn't make the suspension stiff during most of the travel. Have you imagined your 1:1 car ridding on the bump stops every turn?
When watching Renault Clio racing they often lift the inside rear wheel when cornering fast. They obviously don't have set screws to adjust droop but maybe shock length. You would think this was an undesired trait?
dvaid852456 is offline  
Old 10-27-2017, 04:09 AM
  #28  
Tech Regular
Thread Starter
 
dvaid852456's Avatar
 
Join Date: Aug 2010
Posts: 372
Default

Originally Posted by Skiddins
I don't think the dragster example is very good at all, they have huge power to weight ratios and (comparatively) all the weight is at the back to begin with.

Think of an 'average' road car, from standstill if it pulls away hard the front will lift up (more so if it's FWD) and dive when braking. This is the weight transfer in action.
The front will keep trying to lift until there isn't enough downward force on the tyres to produce traction and it either wheel spins or the traction control cuts in.
Sportier versions, sometimes of the same model of car, will come with harder front and rear suspension which help to reduce this transfer.

As they don't have adjustable droop, the dampers and springs are tuned to changed the transfer. We have the benefit of set screws in the wishbones so we can separate some of the this transfer from having to change the springs etc.
Obviously we use a combination to allow us to tune the car for all area's of the track.

Another reason you may loose rear traction with more front droop is that the camber gain at the rear (and/or combined with what the camber was to begin with) is too great and as the rear compresses down to contact patch of the rear tyres is reduced.

Sometimes simply reducing the static rear camber can increase rear traction.

As every setup guide and book keeps telling us, you cannot make a setup change without it, in turn, having an effect on another setting. We're trying to find that ultimate sweet spot for our cars, for each track in each condition.
Thanks Skiddins, yet more great input. To give further background on my setup, I was running 2 degrees of camber all round with little to no camber gain. After the first run I felt that the car was oversteering on corner exit when applying the power coming out of the bend. My hunch was too much front grip rather than not enough rear grip. For the second run I changed from 2.6 front spring to 2.8, went from 1.3mm to 1.4mm front roll bar. The car was better but still a little wayward at the rear so for the third run I increased the front downstop from 8.75mm to 9.5mm. This small change balanced the car, reduced the over-steer and the car felt much more balanced and gave much quicker times. I know the grip was coming up each round due to the track rubbering in and with more runs I was getting used to the track, but the setup changes definitely improved the rear of the car.

As it was the last run I went with reducing front droop as this is what I have known to add a bit of push which is what I needed. I didn't feel increasing front droop as I've tried in the past would have helped but I am definitely going to try 8mm on the second run tonight to see what effect that has. According to theory that should add more rear grip. According to my experience it won't. Tonight will tel!!

Last edited by dvaid852456; 10-27-2017 at 04:22 AM.
dvaid852456 is offline  
Old 10-27-2017, 04:54 PM
  #29  
Tech Elite
iTrader: (1)
 
Join Date: Sep 2010
Location: My house.
Posts: 3,569
Trader Rating: 1 (100%+)
Default

Originally Posted by dvaid852456
When watching Renault Clio racing they often lift the inside rear wheel when cornering fast. They obviously don't have set screws to adjust droop but maybe shock length. You would think this was an undesired trait?
That happens for a couple reasons:
-shedding rear grip (one less tire on the road keeps balance for a FWD car);
-trying to keep the front end to dip and roll too much.

You are bringing FWD cars into the mix, hope you're not getting confused because they have to do some tricks to behave well. 4WD cars like our TC sure benefit from 50:50 weight bias and less pitch motion.
30Tooth is offline  
Old 10-27-2017, 05:02 PM
  #30  
Tech Elite
iTrader: (37)
 
jlfx car audio's Avatar
 
Join Date: Nov 2007
Location: jackson,tn
Posts: 3,834
Trader Rating: 37 (100%+)
Default

Originally Posted by 30Tooth
That happens for a couple reasons:
-shedding rear grip (one less tire on the road keeps balance for a FWD car);
-trying to keep the front end to dip and roll too much.

You are bringing FWD cars into the mix, hope you're not getting confused because they have to do some tricks to behave well. 4WD cars like our TC sure benefit from 50:50 weight bias and less pitch motion.
I know this complicates this thread a little more but I tend to set our cars up with more rear weight bias by a few %. Car just feels to rotate better
jlfx car audio is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.