[Matt Arruda]

Hi guys I'm very green when it comes to chassis tuning so please bear with me. I currently have a BMW e30 with a solid axle ladder bar setup and strange spindle mount front struts combo. The car currently sits with the nose raked down. As most of you know the strange front struts don't have a lot of travel so I don't have much adjustment to get more front ride height out of the coil over. I would like to raise it up because I only have 2" of trans pan clearance and its a pain in the ass to load the car on the trailer and drive over the smallest bump (god forbid if it ever wheelies it would be a mess) The car currently has 22" front runners and I just purchased a set of 24" fronts in hopes to get more ride height. My question is how bad am I going to throw off my current setup by going to this taller 24" front tire and not changing anything else? What should look over or readjust in effort to keep my 60's in check. Granted I'm not cutting the best 60's (1.33 on 26x8.5) I just don't want to go backwards.

 

[The Metal Man]

Maybe it's just the angle of that second pic but it really looks like when you put the 24 on there you're gonna hit the front of your fenderwell/bumper because the tire is gonna be 1in taller all the way around from where it is now... Why is the tire so far forward in the wheel opening? Did you move in forward putting the struts in?

 

[Matt Arruda]

Maybe it's just the angle of that second pic but it really looks like when you put the 24 on there you're gonna hit the front of your fenderwell/bumper because the tire is gonna be 1in taller all the way around from where it is now... Why is the tire so far forward in the wheel opening? Did you move in forward putting the struts in?

I already measured that and it's just going to clear, we did move it forward in effort to increase wheel base.

 

[jonestre.]

In my opinion if it don't rub you'll be fine . You will gain 1/8* of caster ---Trevor

 

[Matt Arruda]

In my opinion if it don't rub you'll be fine . You will gain 1/8* of caster ---Trevor

That's not a bad thing i'll take that, these short wheel base cars need all the help they can get.

 

[hostile]

You will also reduce Antisquat by increasing the CG height in the front end.

But you can easily adjust that by moving the front of the ladder bar up if you need it.

 

[MiNdErAsEr]

Hey Matt,

Two things that come to mind (one of which hostile mentioned above - CG change). The other is higher front end lets more air under the car.

1.) CG - while you can adjust the ladder bar as mentioned, you are raising the CG which could also make the car less stable on the top end if it moves around (higher CG).
2.) Raising the front end allows more air under the car which can also lead to stability issues on top end.

If I recall correctly, your running pretty high MPH and so you will want to watch these two things and comp accordingly. JMO

Good luck.

 

[Matt Arruda]

Hey Matt,

Two things that come to mind (one of which hostile mentioned above - CG change). The other is higher front end lets more air under the car.

1.) CG - while you can adjust the ladder bar as mentioned, you are raising the CG which could also make the car less stable on the top end if it moves around (higher CG).
2.) Raising the front end allows more air under the car which can also lead to stability issues on top end.

If I recall correctly, your running pretty high MPH and so you will want to watch these two things and comp accordingly. JMO

Good luck.

Thanks Mike, I'm hesitant to change the ladder bar as is it's already going slightly uphill. I'll be running x275 on the 12th at NED hopefully I can get some good 60' data. I made a lot of changes to the car since it's last outing and I don't want to change anything else until I know what affect these made. Since the last race I've put the taller 24" front tires, loosened the converter and changed my turbine housing. All these things combined are probably going to have me out in left field somewhere lol. If your not doing anything you should come up I need experienced chassis guy to help

 

[Matt Arruda]

This weekend went good I made 6 passes and each run resulted in a new personal best. The best 60 of the weekend was a 1.29 and the best run was
1.31 60'
3.67 330'
5.675 @ 123.2
7.39 1000'
8.857 @156.9

We started the day running 1.36 60' and only changes to achieve the 1.29 60' was tire pressure stated at 12 psi ended at 10 (going to raise it back up next time out) and lowering the power on the hit. The more power we took out the faster it went. We started the day leaving with 37 PSI 7200 rpm and ended at 30 psi 6500 rpm.

Tires are 26x8.5 Hoosier C11 compound
Ladder bar set slightly uphill
Strange single adjustable rear coils
Strange double adjustable spindle front struts

Please help critique my launch any help is appreciated. Here is the video from this past weekends runs along with some slow motion launches

 

[Matt Arruda]

Here is one more angle in slow motion

 

[voodoo1]

Damm that moves!

 

[hostile]

Those front struts don't let much happen in the way of weight transfer. Is the extension setup pretty loose in the front?

Were the springs spec'd out for your exact weight?

That e30 is 101 wheelbase? 32 inch ladder bars?

Do you know the weight and front to rear weights?

 

[Matt Arruda]

Those front struts don't let much happen in the way of weight transfer. Is the extension setup pretty loose in the front?

Were the springs spec'd out for your exact weight?

That e30 is 101 wheelbase? 32 inch ladder bars?

Do you know the weight and front to rear weights?

Yes Chassis Engineering spec'd out the spring rates I know the rear is 90 lbs I forget what the fronts are ill check tomorrow. We used the outlaw 36" ladder bar kit. I haven't had it on the scales in a few years I don't recall the front to rear. hoping to scale it soon. I will keep you posted.

 

[MiNdErAsEr]

Looks Good Matt!

I agree with Hostile. Front end suspension is not helping (comes up and right back down) which is unloading the rear tires and probably causing the 60' to suffer. Tough to say without seeing all the time slips and incrementals. I'd recommend you stabilize the car with de-tune (as you are doing), then work on the suspension tune. My first reaction is to tune the rear suspension and get it to hook with more power - this should help plant the car on the back tires and drive through the launch under traction. My car doesn't have a lot of front travel in the strut either, but the rear hooks (obviously much easier with my size tire) and carries the front tires 6"-8" for 80-100ft. I think the key is getting it to hook with more power so it doesn't want to nose down and unload the rear tires.

Now that being said, I have a big tire car philosophy. I hear a lot of small tire guys talking about letting the front suspension travel to force the rear to hook. I know it works for some, I'm just not crazy about letting the front end raise do to instability on top end (air under the car and higher center of gravity - car may move around).

You may want to move to ladder bars in more of a level to downward angle...then start adding power and track the 60', then repeat the process to fine tune.

JMO.
Mike