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wheelhopper

Looking for suspension info from the pros

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Glenn

100lb rate change is massive for the rear. I make 25lb jumps in my 4th gen Camaro. Try going up 50lbs from where you are just to see if the car will turn even better than it does now. Loose is fast. As your driving skills increase, your set-up will change and that likely means up'ing rear rates.

 

The point is the bracket the change. You did good dropping the rear alot to make sure your adjustment direction was good, but now you have to wonder if 50lbs would have been a better change, or 75lbs, vs 100.

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Tom P

Glenn, I agree with what you are saying. Since the oversteer was extreme I wanted to take extreme actions the opposite direction. I already had the 200 pounders when I started CMC so it was the easiest, cheapest mod to make.

 

I thought the most risky alteration would be removal of the sway bar. Adam G. stated some drivers like it or hate it. Right now I like it. If nothing else, all of the changes provided a driveable car and at a better starting point for future improvements.

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BADVENM

You mention the shocks on the soft setting but then mention that they are firm (the fronts). Which one is it?

 

I have the same shocks and have them all as firm as they'll go.

 

I'm hoping to maximize our track width before the end of our race season while also adding 17x9.5 wheels and 275 Toyos. We'll be at the same tracks we were with our current nearly stock track width, hopefully the lap times will lower.

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MHISSTC

Dave:

 

Front:

Tokicos, firm setting.

 

Rear:

Tokicos, soft setting.

 

Tom, Are these the Tokico D-spec shocks and struts?

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CMC#11

Tom, what tire pressures are you running front/rear?

The 200 lb. rears are incredibly soft combined with the fact you are running no rear bar. Also, what diff are you running?

 

Another thing to consider is the car might be balanced, but it could still be balanced and faster with a differenc setup. I previously tried a spring change on my car to 850/250 springs. The car was very balanced but slower. When I switched back to 950/300's it was much faster.

 

I prefer the theory of:

1. Get the car as wide as possible front and rear. (for better stability)

2. Then adjust your spring rates and tire pressures to your specific preference.

 

Everyone has their own theory but I shoot for hot tire pressures of 31 lbs.

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Tom P

I'll try to answer some of the questions.

 

Struts/ shocks are Illuminas. Not sure if they are the same as D spec. 5 adjustment settings. Don't know if the settings really make a difference.

Before this change to a softer rear end, rears were always on firmest. And with 275- 300 springs. Liked it a little on the loose side.

 

Once the longer front control arms were added, everything went out the window. The rear end had zero traction. One example was rounding Turn 1 at Mid-Ohio, simple cornering produced a 540 degree spin, facing backward on pit exit. It was like driving on oil. Same with the keyhole, valley and carousel. That's why I decided on the radical softening at the rear.

 

I've tried tire pressures across the board this year. This past weekend I liked 30 front / 28 rear, cold. though I've also tried everything 24 - 32 psi. This particular weekend the 30/28 worked best for me. These are 16" 255's.

 

I'd like to increase the rear width by 2 inches but it will cause some major body interference issues I'm not prepared to deal with right now.

 

At this point I'm just happy I can drive the car without looking like an idiot. And surprised it can handle so well. It's been a frustrating season to have to go so slow to avoid sliding off the track or spinning within it!

 

I'm temporaily satisfied. Undoubtedly changes will evolve.

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Tom P
Also, what diff are you running?

 

A tired Trac-Loc with 3:55's.

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Adam Ginsberg
Everyone has their own theory but I shoot for hot tire pressures of 31 lbs.

 

Wow.....interesting. Hot pressure of 31? On my car, that would produce allot of push. I shoot for 37-39psi hot pressure.

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CMC#11
Everyone has their own theory but I shoot for hot tire pressures of 31 lbs.

 

Wow.....interesting. Hot pressure of 31? On my car, that would produce allot of push. I shoot for 37-39psi hot pressure.

Yup, usually go out 23-24 psi cold. I have tried the higher pressures in the past but the car just falls off so quick with anything above 35 psi.

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Adam Ginsberg
Yup, usually go out 23-24 psi cold. I have tried the higher pressures in the past but the car just falls off so quick with anything above 35 psi.

 

I used to run those low starting pressures, but found I wasn't gaining enough PSI during the race. While working to dial out the front push, I added some pressure, and it's made a world of difference. Figured it out at the 2010 MMP Nationals, and lowered my laptimes by a full second (while also removing the rear spoiler).

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Tom P

I'm hoping to maximize our track width before the end of our race season while also adding 17x9.5 wheels and 275 Toyos.

Would you update us once you get done on any mods needed to the rear quarters?

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BADVENM

Just an update regarding air pressures after reading the past few posts from Adam and company.

 

This past weekend at High Plains Raceway I knocked as much as 2 seconds off my previous best lap time which was set back in May. Looking back at my notes from our May event at this track I started with cold pressures of 31.5 in the front and 29.5 in the rear Saturday. I eventually went to 27 in the front and 26 in the rear (Sunday) which is where I set my best lap time (at that time). The shocks were at full stiff setting. What also helped was that the weather on that Sunday was much cooler.

 

I went back to cold front tire pressures of 31.5 pounds and 29.5 in the rear for this past weekend. This is on the 255's. Hot pressures were between 37.5 and 40 in the front and 34.5 to 35.5 in the rear. I had the Tokico shocks dialed back to neutral. On Saturday it was much cooler then it was yesterday (Sunday). Saturday is when I set my new best lap time. Sunday was about 10 degrees hotter (around 90) and my times were about a second or so slower.

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MHISSTC

Adding to Dave's post above, tire wear across the face of the tread on the front has improved by leaps and bounds after we upgraded from the fox to the SN95 parts this year. Negative camber and caster is pretty much maxed out, but even on both sides. This is with a set of MM CC plates and no enlarging out of the hole the strut rod passes through.

 

The uneven wear across the tread of the rear tires is much more noticeable now with the outer shoulders showing much more rounding than the inner shoulders. We are running fox length rear axles. It is clearly time to flip the tires on the rear wheels while it does not appear to be needed in the front. I'm thinking the uneven wear we are seeing on the rear tires could be helped by some cambering of the rear axle. However, we feel there are other priorities we need to work on before that, like maximizing tire width and track width and doing the associated body work to accommodate it, dealing with a nasty mid-throttle hesitation and stumble we haven't figured out yet, and a possible Trac-Loc upgrade that may be the source of the noise during hard cornering mostly on one side we haven't been able to track down yet. After we figure all that out, we'll likely have to play with the rear spring rates and then maybe we'll look at cambering the rear axle camber.

 

On a side note: during the past couple of events, the Rocky Mountain Region drivers have offered to swap cars during the race warmups just to get a feel for the strengths and weaknesses of the different platforms and the individual cars so we can figure out how to bring everyone's cars up to the same level. We've had long term GM drivers drive SN95s and Foxes, long time Mustang drivers drive the 4th gen LS1 cars, and fox drivers drive SN95s. The open sharing and feedback has been phenomenal! Thanks to everyone who has been willing to share and provide input on how to make all of our cars better.

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MHISSTC
Would you update us once you get done on any mods needed to the rear quarters?

 

We are going to be ordering a single 17x9.5 6mm offset wheel along with a 275 RA1 today to trial fit to the car to finalize our plan before we attempt any serious fender modifications and before we commit to at least one complete set of new tires and wheels. We measured multiple times to be sure, but the following is what we came up with on the car right now.

 

We have 16x8 (25mm offset I'm pretty sure) MB comp wheels with 255s on it right now with a fox width rear axle and SN95 setup in the front. With NO spacers, the rear track width is 68 1/8" and the front track width is 70 1/2". We found a pretty cool wheel offset calculator online and used that along with the dimensions of the RA1s on the Toyo website to calculate the effect of changing the width of the wheels and tires with different wheel offset.

 

Overall by going from the 16x8 MB Comps with 255s to the 17x9.5 wheel with 275 RA1s we push the outer dimensions out by exactly 1" on each side. Added to our current front track width above, that puts us at 72.5" which is 1/4" less than the maximum allowed. In the rear, our track width will expand to 70 1/8", which we figure allows us to run another 1" spacer on each side to bump it out to 72 1/8", which is still 5/8" short of the maximum track width allowed.

 

We measured that against the body and figured we need to do some serious cutting of the rear fender and we need to add a good 2" fender flare. In the front, we've already modified the fender some to gain some clearance, but need another 1" worth of width to accommodate the different setup. We figured if we started with an unmodified front fender, we would also need a good 2" fender flare and we would have to clearance the front and rear portions of the front fender wheel openings by about 1" to accommodate the wider tire through the range of steering.

 

I'm really itching to try my hand at making some fiberglass flares that can be attached to the car with rivets in order to make quick and easy repairs if needed. Plus we figure the car would look wicked cool with a set of black 2" flares over each wheel arch that extend up a little bit further on the car...sort of like the poor mans version of the Tiger Racing fender flare that doesn't need to be smoothed into the bodywork, or something similar to the old school Datsun Z flares.

 

Sorry for the big pic. It's the only one I could find of the fox Tiger Racing flares I could link to. The Tiger Racing web site isn't around anymore, but they do have a FaceBook page.

 

fox_flares.jpg

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CMC#11

http://www.camaromustangchallenge.com/forum/viewtopic.php?t=3546&postdays=0&postorder=asc&highlight=mustang+flare&start=0

 

I still prefer the way I did my front track width mods a few years ago. They give more than enough room to alter spacers / side for each track and actually give good protection in case of an accident. Earlier this year I had a competitor slide into my passenger side and the stretcher bar I have pushing out the fender didn't move at all and saved my front suspension from any damage.

 

I still need to done some extensive work on the rears to get even close to max track width. I am still looking at all options available to get the cheapest, easiest, and least offensive flares on the rear.

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Alien

What effect with squaring off the car have on handling? Won't making the rear track width equal to the front hurt the turn in? I also thought Mustangs have a tendacy to understeer. Wouldn't having a narrower rear track width than the front reduce understeer?

 

Something to think about; sometimes just because the rules allow something, doesn't always mean it's the best/fastest.

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CMC#11
What effect with squaring off the car have on handling? Won't making the rear track width equal to the front hurt the turn in? I also thought Mustangs have a tendacy to understeer. Wouldn't having a narrower rear track width than the front reduce understeer?

 

Something to think about; sometimes just because the rules allow something, doesn't always mean it's the best/fastest.

Yes, there is a tendency for certain Mustangs to understeer. It is all a preference on how each car is setup. My fox is 2" wider in the front than the rear. Jerry Jordan's SN99 is 2" wider in the rear than the front. That is a 4" split in difference and both cars handling feels great. The wider rear track in Jerry's car gives it a much more stable balance through high-speed corners.

Why not maximize track width for the most stable platform and then adjust spring rates and other components to get the proper balance? Isn't that what the GM camp does? If not, then they wouldn't have a problem reducing their track width max down to the Mustang maximum of 73.75".

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MHISSTC
What effect with squaring off the car have on handling?

We don't know for sure yet.

 

Won't making the rear track width equal to the front hurt the turn in?

Maybe. We've been told our car has great turn-in right now... ...much better than a well set-up 4th gen... ...so we have room to play.

 

I also thought Mustangs have a tendacy to understeer.

Sometimes.

 

Wouldn't having a narrower rear track width than the front reduce understeer?

Possibly.

 

Something to think about; sometimes just because the rules allow something, doesn't always mean it's the best/fastest.

 

We've gone over those potential issues ourselves. We know doing this will change the car, but we don't know exactly how yet. We are willing to try different configurations to find out. One benefit to having the Fox length axle is we still have more than an inch of track width on each side where we can add or subtract wheel spacers as needed. What we know for sure is we want to put the maximum amount of rubber to the road with the widest possible footprint. That's what we'll start with, and we'll make adjustments from there.

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MHISSTC
...Mustang maximum of 73.75".

 

That is correct for front and rear of a '99-'04.

'94-'98 is 73.25 front and 72.75" rear.

and '79-'93 is 72.75" front and rear.

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Glenn
What effect with squaring off the car have on handling? Won't making the rear track width equal to the front hurt the turn in? I also thought Mustangs have a tendacy to understeer. Wouldn't having a narrower rear track width than the front reduce understeer?

 

Something to think about; sometimes just because the rules allow something, doesn't always mean it's the best/fastest.

Yes, there is a tendency for certain Mustangs to understeer. It is all a preference on how each car is setup. My fox is 2" wider in the front than the rear. Jerry Jordan's SN99 is 2" wider in the rear than the front. That is a 4" split in difference and both cars handling feels great. The wider rear track in Jerry's car gives it a much more stable balance through high-speed corners.

Why not maximize track width for the most stable platform and then adjust spring rates and other components to get the proper balance? Isn't that what the GM camp does? If not, then they wouldn't have a problem reducing their track width max down to the Mustang maximum of 73.75".

 

So narrow up the GM's to do what? Slow them down? And what do you give up to slow you down the same amount?

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ShadowBolt
What effect with squaring off the car have on handling? Won't making the rear track width equal to the front hurt the turn in? I also thought Mustangs have a tendacy to understeer. Wouldn't having a narrower rear track width than the front reduce understeer?

 

Something to think about; sometimes just because the rules allow something, doesn't always mean it's the best/fastest.

Yes, there is a tendency for certain Mustangs to understeer. It is all a preference on how each car is setup. My fox is 2" wider in the front than the rear. Jerry Jordan's SN99 is 2" wider in the rear than the front. That is a 4" split in difference and both cars handling feels great. The wider rear track in Jerry's car gives it a much more stable balance through high-speed corners.

Why not maximize track width for the most stable platform and then adjust spring rates and other components to get the proper balance? Isn't that what the GM camp does? If not, then they wouldn't have a problem reducing their track width max down to the Mustang maximum of 73.75".

 

So narrow up the GM's to do what? Slow them down? And what do you give up to slow you down the same amount?

 

Waste of time Michael. They get it but want to act like they don't.

 

 

JJ

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CMC#11
What effect with squaring off the car have on handling? Won't making the rear track width equal to the front hurt the turn in? I also thought Mustangs have a tendacy to understeer. Wouldn't having a narrower rear track width than the front reduce understeer?

 

Something to think about; sometimes just because the rules allow something, doesn't always mean it's the best/fastest.

Yes, there is a tendency for certain Mustangs to understeer. It is all a preference on how each car is setup. My fox is 2" wider in the front than the rear. Jerry Jordan's SN99 is 2" wider in the rear than the front. That is a 4" split in difference and both cars handling feels great. The wider rear track in Jerry's car gives it a much more stable balance through high-speed corners.

Why not maximize track width for the most stable platform and then adjust spring rates and other components to get the proper balance? Isn't that what the GM camp does? If not, then they wouldn't have a problem reducing their track width max down to the Mustang maximum of 73.75".

 

So narrow up the GM's to do what? Slow them down?

Yes

And what do you give up to slow you down the same amount?

Nothing, this is to just get things closer to equal.

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Glenn

Any evidence that isn't the case now?

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