Handling (Butchered parcel shelf)

[edb49]

The last guy who had my new baby (325i sport) put a pair of 6x9s in the parcel shelf and butchered through the firewall/bulkhead (not sure of the name) with a jigsaw or similar.

Was wondering if this would affect the handling much? If so, would it be worth getting a strutbrace to sort it?

I'm going to get the car's handling sorted, my current plans are:
1) Polybush all round
2) Springs+shocks from these guys: http://www.205challenge.com/BMW/index.htm
3) Front & rear strut braces
4) Brakes?
5) 16" wheels and lower profile tyres?

I'm not sure on the last two, I'm trying to get it handling as tight as possbile, I don't care if it's an uncomfortable pain in the **** to drive. Any other suggestions on worthwhile mods to get the handling more on the ball? (It's pretty good as standard mind you!)

Advice greatly appreciated

Thanks

Ed

I'm not sure on the last two

[Brianmoooore]

It'll handle better on 15" wheels. Big diameter wheels are for posing or accomodating large brakes.
The parcel shelf/ rear bulkhead is structural and is important to the roll stiffness of the shell, but unless most of it has been removed I doubt if it'll make any difference.

[astondg]

It'll handle better on 15" wheels. Big diameter wheels are for posing or accomodating large brakes.

Going to 16" isn't a problem. I went from 15" with 205/55/15 tyres to 16" with 205/50/16 tyres and I didn't notice any difference in hanling at all. My lap times stayed the same too. The lower profile tyres will help handling because there will be less sidewall flex, if you go too low with the profile it can upset the handling on bumpy roads but something like 205/50 should be fine. The one thing that will affect handling is the increased unsprung weight that a bigger wheel could have, except that my 16" wheels weigh less than the 15" BBS.

Aston

[edb49]

I forgot about the unsprung weight issue

The main reason for getting bigger wheels is to reduce sidewall height. I used to have an E36 and there was an *epic* difference going from 17" with 35 profile tyres to 15" with 60 profile. The 17s made the car feel a lot sharper, but downside was it would dig in to potholes/ruts etc.

[astondg]

Yeah, definately should be better with less sidewall height, except over bumps. Like I said though I didn't notice any difference going from 55 profile to 50, 15" wheels to 16", and going to about 2kg lighter wheels (each wheel) all at the same time for either handling, ride, or lap times. So 15" to 16" should really be fine. 17" might cause problems though, especially if they are fairly heavy compared to the 15".

The E36 might have handled bigger wheels a bit better than an E30 because they actaully came as options from the factory or standard on the E36 M3.

Aston

[edb49]

re: wheels/tyres I'm going to put some new tyres on the front with reinforced sidewalls, and pump up the rears to 40psi to give them a bit more rigidty. I think I'll stick with the standard 15" wheels tho.

[JimmyC]

soft fronts and hard rears will produce a mass of over steer- 40 psi seems excessive to me- especially if you are talking cold temps.

Side wall flex is a good thing in moderation.

I run my exige @ 20F/22R cold.

I know different cars, wheels tyres etc but I would have thought with that pressure you'll be getting dizzy.

interested to hear what the view is on this as I haven't even driven my E30 yet, let alone started testing.

I'm going for powerflex bushes, strut braces, full welded cage so I should be rigid as can be, i'll be sticking to 15" wheels too.

Undecided on shocks but looking at GAZ at the mo

[Karan]

i run 35 on front, 40 on rear...... seems ok to me.....

[Karan]

oh yeh using 205 50 15s.... ive tried loadsa sizes on 15s and i like these the best

[edb49]

Jimmy - I prefer a car that is balanced towards oversteer but predominately neutral, so the 40psi at the rear is intentional. I'll drop it down to 35psi if it is ridiculous.

Cage is probably out of my budget to be honest, but it would be nice to make it even more rigid.

Chucking carpets and rear seats out isn't out of my price range though! I've got one with manual windows but an electric sunroof, so I may chop the sunroof out and rivet a sheet of steel in place. All weight saving/strengthening can only help.

[JimmyC]

Still trying to get my head round those pressures, but until I start playing i'm in no position to comment or judge.

I'll prob start around Karan's figures and take it from there.

My sunroof is coming out too and getting a panel welded in place, itching to have a drive now

[astondg]

TYRE PRESSURES: I have Toyo Trampio R1R tyres that are a semi race type tyre, although they still have tread blocks, and I use about 35psi hot on the race track F & R. More than that (but still even at all tyres) and it understeers too much. I haven't actually tried more at the rear than the front but with even pressures it seems to be nicely balanced, I don't want an oversteery car when I am trying to go fast. I tried about 38psi hot in all tyres and I was about 1.5 sec slower per lap. All the race tracks I go to reccommend at least 40psi for road tyres on the track but I have never used that much.

WEIGHT SAVING: I have recently done a dirt circuit race and a bitumen track day in my 323i, which at the moment has no door trims, no front passenger seat and no rear seat, and it didn't feel any different to when all that stuff was in it. I also did about the same lap times. Taking all of that out probably only saved about 30kg, the back seat and door trims don't weigh much, so not a big difference and I could easily have removed that advantage by having a different amount of fuel in the tanks than last time.

Aston