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Old 03-03-2014, 08:08 PM   #61
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Originally Posted by Robbob View Post
This looses me - I thought I understood it but then some locals convinced me opposite.

So thinner rear diff helps take steering out of the car?

My thought about it - thicker would make the car oversteer because it would be tougher for the tire underload (outside tire) to diff out/slip causing the car to drive off it more.

The locals convinced me that lighter would let the tire underload/slip and the front pull the car around, less drive off that tire.

I havent tested heavy vs light but plan too just to feel myself but like to know which theory is correct.
It is understandable that you hear both answers, because both are true depending on if you are off power or on power while turning.

When you are off power and turning a lighter rear diff oil will give you more steering because the diff does not resist the outer rear wheel from turning at a higher rate of speed than the inner rear wheel. So if you have a heavy rear diff oil then you will have less steering off power.

When you are on power the lighter rear diff oil allows the diff to "diff out" more easily meaning that the rear tires are not driving the car forward as much. When you are on power a heavy rear diff oil will keep the rear more locked causing the rear tires to have more forward drive collectively and producing more wheel spin against the driving surface causing the car to be more loose.



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thanks Martin for your reply, much appreciated.

Cheers
Karl
no problem!

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Thank you very much Martin!

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Sub'd

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Wow great thread. Subscribed!!!! This should be a sticky on top!!

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brought both your apps Martin, thanks.

How about 1/12th scale?
1/12th scale is not something I spent a lot of time racing. I think I raced 1/12th scale about 5 times in total So I am not that knowledgeable about 1/12th scale. Having said that if a top driver wanted to share some knowledge I would be happy to include it in the app.

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How do you control tire temperatures, mostly in the context of modified touring?

For example:
- Getting heat into the tires quickly in low ambient temperatures, or high grip carpet where the car isn't sliding much, or the compound is just a bit too hard for the track temperature.
- Keeping tires from overheating, like when the compound is a bit too soft for the track temperatures.
- Balancing heat between front and rear so that the balance doesn't change through a run

-Mike
I don't think my thoughts here is anything new, but here you go..

Getting tires up to temp -> well tire warmers are a good thing with low ambient temps. Also during my warm up lap(s) weaving back and forth helps a little.

Keeping the tires from overheating -> This really is about...

a) A well balanced setup that is not too loose or too tight
b) looking at tire wear, and managing things like rear toe, static and dynamic camber etc, to ensure I am not over using/wearing a portion of the tire. For example I expect to see a fairly even wear across the entire width of the tire.
c) Being disciplined and not getting too greedy with throttle and braking. In some races where overheating the tires is an issue due to track conditions etc, I will purposely drive less aggressively during the race and only push it when it may result in a pass or defending a pass.
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Old 03-03-2014, 08:18 PM   #62
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Hi Martin,
Perhaps your insight could help.

Car is stable at speed, understeers slightly on power at high speed and understeers off power at speed. The rear end is very well planted at medium and high speed.

Car feels well balanced at corner entry (could use a touch more initial steering) at medium to low speed.

But the car is a touch twitchy at low speed mid corner and the rear end suddenly breaks traction. The car is hard to control hard and to control at low speed corner exit on power.

Track is smooth high grip asphalt.

Front spool, rear diff 2k, caster is 2 deg, rear toe in 2.5 deg. I think springs, shocks and bars are in the ball park (kit setup and they feel about right).

I have tried 2 different bodies and a different wing. Bodies didnít have any effect but a smaller wing improved high speed steering a touch with very little difference at low speed.

I was planning to change the rear toe to 3.0 deg and lower the rear roll center. Pending on results I may adjust the rear wheel base moving the rear wheels closer to the center of the car. But after reading your posts I might be better make adjustments to the front roll center.

What would you suggest I look at first.
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Old 03-03-2014, 08:22 PM   #63
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Martin, what is front bump and rear bump mean?
THANK YOU
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Old 03-03-2014, 09:07 PM   #64
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Just purchased Martin's subscription. I encourage others to do the same. It's a cheap way of saying thank you for his expert knowledge and time taken to aid others. FYI I do not know Martin personally... just thankful for the information.
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Old 03-03-2014, 09:22 PM   #65
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Hi Martin,

I was wondering if you could elaborate on Arm Sweep? I hear alot of people using it however, there isn't much information about it anywhere and I get mixed answers about. Any help you could provide would be great. I have your App's and your book, both have taught me alot!

Thank you!
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Old 03-04-2014, 07:53 AM   #66
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Originally Posted by Martin Crisp View Post

Yes it will give you more lateral grip, but the car will also feel less smooth in its transitions.

Hello Martin

Thanks.

wish is the best option to run in low grip situations .

raise the suspension arms or lower the suspension arms ??

Best regards:
Pedro Silva
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Old 03-04-2014, 08:03 AM   #67
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Originally Posted by frozenpod View Post
Hi Martin,
Perhaps your insight could help.

Car is stable at speed, understeers slightly on power at high speed and understeers off power at speed. The rear end is very well planted at medium and high speed.

Car feels well balanced at corner entry (could use a touch more initial steering) at medium to low speed.

But the car is a touch twitchy at low speed mid corner and the rear end suddenly breaks traction. The car is hard to control hard and to control at low speed corner exit on power.

Track is smooth high grip asphalt.

Front spool, rear diff 2k, caster is 2 deg, rear toe in 2.5 deg. I think springs, shocks and bars are in the ball park (kit setup and they feel about right).

I have tried 2 different bodies and a different wing. Bodies didnít have any effect but a smaller wing improved high speed steering a touch with very little difference at low speed.

I was planning to change the rear toe to 3.0 deg and lower the rear roll center. Pending on results I may adjust the rear wheel base moving the rear wheels closer to the center of the car. But after reading your posts I might be better make adjustments to the front roll center.

What would you suggest I look at first.
Hi,

I would change from 2 degrees caster to 4 degrees caster. That should help the push feeling you have at speed. It may even help with the low speed twitchy feeling you mention. I think the low speed on power twitchy feeling you have could also be a result of the rear toe not being enough...so moveing to 3.0 rear toe will help keep the rear planted on hard acceleration out of low speed corners. I also think you are on the right track about potentially lowering the rear roll center, but try the rear toe first and then add the lower rear roll center.

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Originally Posted by vivo quevas View Post
Martin, what is front bump and rear bump mean?
THANK YOU
If you are referring to shocks, bump simply means the compression of the shocks. It is fairly common to say, I want to increase the bump meaning that you want to increase the resistance to bump through the shock oils and pistons. Also this is something called fast bump which is when the shock is compressed very very rapidly by going over bumps or chicane dots etc.

Here is an excerpt from my app..

Slow Dampening v.s. Fast Dampening

There are two different types of dampening, one is called slow dampening and the other is called fast dampening .

Fast Dampening is what happens when a tire goes over a bump and there is a very quick force put on the shocks.

Slow Dampening is what happens when your tuning into or out of a corner or accelerating or braking. the forces are not as sudden as a bump.

The size of the piston hole has a larger effect on fast dampening than slow dampening, due to the high velocity of the shock oil. The smaller the piston hole in a fast Dampening scenario the more "pack" is created as the high velocity oil can't fit through the hole as easily as slow velocity oil, making the shock very stiff, causing the car to bounce more.

To reduce this bounce effect under fast dampening, make the piston hole bigger.

But damper adjustments for balance have more to do slow dampening , which occurs at turn in, and turn exit. It needs to be noted that dampers effect on handling is contingent upon the suspension being in some state of transition. Once the car takes its set (ie: in a steady state sweeping turn) the dampers have no affect on handling until we supply a steering input that gets the suspension moving again.


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Just purchased Martin's subscription. I encourage others to do the same. It's a cheap way of saying thank you for his expert knowledge and time taken to aid others. FYI I do not know Martin personally... just thankful for the information.
Thank you Yeah...I don't make much money off the app...so I appreciate the support. So far this LearnSetup.com app has generated a whopping $294

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Originally Posted by Robertcooper88 View Post
Hi Martin,

I was wondering if you could elaborate on Arm Sweep? I hear alot of people using it however, there isn't much information about it anywhere and I get mixed answers about. Any help you could provide would be great. I have your App's and your book, both have taught me alot!

Thank you!
To be honest I have not done much research and testing on arm sweep. there may be some people that have done a lot of testing that can comment on this. It is supposed to add more steering, by adding arm sweep. But as I think through the dynamics of what this change would do,...if you were to widen the distance between the front portion of the arms and keep the rear portion of the front arms where they were, this would actually push the connection point of the shocks on the lower arms further apart, making the front shocks have a higher spring rate, but also be more progressive. That increase in spring rate should make the car push more I would think, but maybe because the shocks are now more progressive they are initially softer...not really sure to be honest. The other aspect at play here is the angle of the hinge pin is now point outward towards the front of the car. This to me would increase the resistance of the arm pivoting on the hinge pin from the forces as you enter a corner. But at the same time the front wheels are just a little bit further back towards the rear of the car, which would decrease their leverage against compression, making the front softer.

So it seems to me there are some aspects of sweep that would make the front softer and others that would make the front harder. I don't know what the net effect would be.

At the end of the day, the best thing to do is to experiment and see what it does. This applies to all setup changes, as I mention in my app, there are times when a setup adjustment will add steering and when that same setup adjustment will remove steering, as setup is the sum of its parts, and you can take setup changes too far. For example in general going softer on the springs at the front of the car will give you more steering. However if you go too far, it will take away steering.

On a related note... In my posts I have been saying that you will want to use a stiff chassis on high grip tracks and a flexible chassis on low grip tracks. This morning I was talking with Paul Ciccarelo and his testing with the serpent 411 at the snowbirds and at the gate seemed to produce the opposite results for him. He found that by removing screws in the upper deck the car was smoother and easier to drive and did not traction roll as easy. Where as in my testing last Saturday at a medium grip track here in Ontario when I took screws out of the upper deck the car started to traction roll and was very twitchy. So although there are some general rules of thumb, you can't forget that setup is the sum of its parts and you need to always be experimenting and testing to see what works with the collection of setup options you have on your car at any one point in time. Perhaps the serpent chassis and upper deck has different flex points than the CSO v2 car I ran last weekend and these different flex points caused different handling behaviours, which would explain why Paul got different results than me.

Anyway...this is what I love about the art and science of setup. If it were easy, then what fun would that be

Cheers.
Martin.
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Old 03-04-2014, 08:09 AM   #68
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check out this thread... christian tabush of Reflex racing explains it very well...

lets talk about arm sweep and its effects
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Old 03-04-2014, 10:14 AM   #69
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check out this thread... christian tabush of Reflex racing explains it very well...

lets talk about arm sweep and its effects
and heres the other one i started
http://forum.teamxray.com/viewtopic.php?f=8&t=13756
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Old 03-04-2014, 11:02 AM   #70
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I will have to do some testing and research with sweep to better understand what it does.

According to Hagberg on that thread it makes the car turn in harder but increases risk of traction roll. Not sure I like either of those attributes

By the way...made some more updates to the app today

http://learnsetup.wpengine.com/march...setup-com-app/
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Old 03-04-2014, 01:28 PM   #71
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Originally Posted by Martin Crisp View Post

On a related note... In my posts I have been saying that you will want to use a stiff chassis on high grip tracks and a flexible chassis on low grip tracks. This morning I was talking with Paul Ciccarelo and his testing with the serpent 411 at the snowbirds and at the gate seemed to produce the opposite results for him. He found that by removing screws in the upper deck the car was smoother and easier to drive and did not traction roll as easy. Where as in my testing last Saturday at a medium grip track here in Ontario when I took screws out of the upper deck the car started to traction roll and was very twitchy. So although there are some general rules of thumb, you can't forget that setup is the sum of its parts and you need to always be experimenting and testing to see what works with the collection of setup options you have on your car at any one point in time. Perhaps the serpent chassis and upper deck has different flex points than the CSO v2 car I ran last weekend and these different flex points caused different handling behaviours, which would explain why Paul got different results than me.

Anyway...this is what I love about the art and science of setup. If it were easy, then what fun would that be

Cheers.
Martin.
Now we just need you to get back to racing more so we can compare notes on the same track and possibly the same car

Its strange on how we all get different results, I'm sure some of it also has to do with how we approach the corner with our line, speed or manipulate the wheel in certain parts of the turn. That could go with any setup change.
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Old 03-04-2014, 01:42 PM   #72
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Now we just need you to get back to racing more so we can compare notes on the same track and possibly the same car

Its strange on how we all get different results, I'm sure some of it also has to do with how we approach the corner with our line, speed or manipulate the wheel in certain parts of the turn. That could go with any setup change.
REEDY RACE

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Old 03-04-2014, 02:03 PM   #73
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Now we just need you to get back to racing more so we can compare notes on the same track and possibly the same car
You never know what the future will bring.

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Its strange on how we all get different results, I'm sure some of it also has to do with how we approach the corner with our line, speed or manipulate the wheel in certain parts of the turn. That could go with any setup change.
I agree...there are so many variable from tires, to tracks, to chassis flex points, to driving style etc etc...that's what makes setup something you chase, and rewarding when you get it right.
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Old 03-04-2014, 02:21 PM   #74
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I have your app and I love it. Today I decided to go ahead and subscribe to learnsetup.com

This may be asking too much but if you every get the chance to blog, maybe do a quick writeup on droop setup and clarify the difference between using blocks and over ride height method.

I do both according to manufacture, on my xray I use the block method as recommended and my Tamiya I measure to the pin of the arm, on my yokomo I measure orh. When I actually go measure droop on each car I find myself between 2-5mm depending on conditions. To make sure it short, is there a squash all method of measuring droop?
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Old 03-04-2014, 03:05 PM   #75
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Hi Martin,

What handling characteristics make you decide that a car needs harder or softer shock oil? Same question for rebound?

Thanks!
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