For those of you running 17's with big, meaty tires

[Massive Lee]

Because E30s have lovely steering, arent generally prone to understeer when set up correctly and too big a tyre doesnt help anything really. Find me an example of a high performance RWD car which wears the same tyre size front and rear, especially one which wears 245s on the front of an 1100kg car.

I beg to differ. The e30 understeers by nature and the suspension must be worked so that it reduces understeer. Using same size tires on all four corners is one of the ways to achieve this. You can also stiffen up the rear springs, but not the rear sway bar.

Using narrower front tires will plague the car with even more understeer.

[330icrazy]

I beg to differ. The e30 understeers by nature and the suspension must be worked so that it reduces understeer. Using same size tires on all four corners is one of the ways to achieve this. You can also stiffen up the rear springs, but not the rear sway bar.



Using narrower front tires will plague the car with even more understeer.

I agree and the steering rack blows. Took like 4 turns lock to lock felt like I was driving a tractor. So I swapped it out for the e36 m3 rack from a 95.


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[Massive Lee]

BTW as much as I appreciate people collecting data off the internet, such as tire sizes for off-the showroom street-driven cars, I think that it doesn't beat real life experience on the track.

The e30's suspension set-up is pretty simple. Same size tires on all four corner. Lots of front camber (as much as you can get). Stiff front springs and swaybar. But even stiffer rear springs but soft swaybars if you intend to be back on throttle as soon as possible after a corner. If you use a stiff rear swaybar, you will have to wait forever until you can apply full throttle because that stiff sway bar will lift the inner rear wheel, while BOTH rear wheels should be applying power on the ground.

I even suggest to tune the e30 so that it oversteers. It will allow you to steer the car on throttle. ON or OFF with minimal steering wheel input. This is when the car gets fast because the straighter the steering wheel, the more throttle you can give. This is the ABC of track driving. ;-)

[LowR3V'in]

^ i just run stiff ass rear springs w/ no sway.
super predictable and neutral

btw. how the heck do u guy run wide tires
i had to smash the body in 2'' just to get my little 225s to lock without rubbing.
is that super structural do u guys need to cut it out?


No more rubbing by jet jones, on Flickr

[e30davie]

In response to Massive Lee, How stiff we talking for that rear spring?

I have a set of aftermarket springs and the front feels nice and composed, but the rear has an annoying bounce to it. Needs to be stiffer. it is around 400lb/in. (new Koni yellow shocks btw)

[LowR3V'in]

davie, i know ur not asking me but mine are 650 rear they are a good street stiffness
with koni sa all the way soft. doesn't squat when you put the power down and roll isn't bad at all.
i'm an old man and have been driving the e30 everyday recently. Even took it off roading today.
Start with 650 imo. 400 is more for the front.

[e30davie]

thanks for that. its about the rate i was going to aim for based on some research. I picked up a set of "king springs" here in Aus for really cheap, the fronts are only 220 and the rears are 400ish., too soft me thinks. i have to run the konis at about 30% from zero to get them to stop bouncing. it rides ok but its nothing special, too soft all round i think.

I am not sure what options i have for springs in aus, might have to look at buying overseas. what brand do you recommend?

I am not a young hooligan, but i dont mind stiff suspension. I just hate incorrect suspension.

[alistairolsen]

Like I said, if there's a genuine proven need for it, with data to support that the tyres are actually working, then great! It would appear that's the case here.

There are so many 'trends' in car mods that are utter bollocks it pays to stop and question things once in a while!

As for the car not being 1100kg, as you pointed out there arent any, and if there were, there probably wouldnt be quite so many E30 enthusiasts, but the cars shown cover a range of weights 500kg either side and power above and below. Driveline layout is largely irrelevant if the weight distribution and intertia are similar. The E30 is a little longer but something like a Z3 and an elise is largely swapping the engine and the passengers

[alistairolsen]

Like I said, if there's a genuine proven need for it, with data to support that the tyres are actually working, then great! It would appear that's the case here.

There are so many 'trends' in car mods that are utter bollocks it pays to stop and question things once in a while!

As for the car not being 1100kg, as you pointed out there arent any, and if there were, there probably wouldnt be quite so many E30 enthusiasts, but the cars shown cover a range of weights 500kg either side and power above and below. Driveline layout is largely irrelevant if the weight distribution and intertia are similar. The E30 is a little longer but something like a Z3 and an elise is largely swapping the engine and the passengers

[Massive Lee]

btw. how the heck do u guy run wide tires
i had to smash the body in 2'' just to get my little 225s to lock without rubbing.
is that super structural do u guys need to cut it out?

96+ e36 m3 control arms with its increased caster and/or offset lollipop.
they move the wheel forward

[Massive Lee]

Like I said, if there's a genuine proven need for it, with data to support that the tyres are actually working, then great! It would appear that's the case here.

There are so many 'trends' in car mods that are utter bollocks it pays to stop and question things once in a while!

As for the car not being 1100kg, as you pointed out there arent any, and if there were, there probably wouldnt be quite so many E30 enthusiasts, but the cars shown cover a range of weights 500kg either side and power above and below. Driveline layout is largely irrelevant if the weight distribution and intertia are similar. The E30 is a little longer but something like a Z3 and an elise is largely swapping the engine and the passengers

Trend? Car mod? We're discussing track set-up here. Not making points at car shows...
Do you track your car regularly? Do you time yourself? What works best?

[alistairolsen]

Well no, the thread was a generic discussion about big wheels on E30s ;-)

I've tracked several, not the E30 yet.

I've also seen trends for allsorts with no supporting data, E36 M3 5 stud conversions for a start (I'm yet to be able to find any back to back lap data, or any geometry data beyond static alignment sheets), wildly excessive spring rates, cars run so low the suspension motions are all wrong, forum preferences for a certain tyre based on nothing but collective anecdotal "they're good".

So like I say, if it's needed, and proven with data, then there is the answer to my question - but I dont feel the need to apologise for asking it ;-)

[iansane]

Like I said, if there's a genuine proven need for it, with data to support that the tyres are actually working, then great! It would appear that's the case here.

There are so many 'trends' in car mods that are utter bollocks it pays to stop and question things once in a while!

As for the car not being 1100kg, as you pointed out there arent any, and if there were, there probably wouldnt be quite so many E30 enthusiasts, but the cars shown cover a range of weights 500kg either side and power above and below. Driveline layout is largely irrelevant if the weight distribution and intertia are similar. The E30 is a little longer but something like a Z3 and an elise is largely swapping the engine and the passengers

You talk in circles. YOU were the one that came up with an 1100kg criteria. Drivetrain layout is most definitely going to affect tire sizes. A modern base Carrera uses a 235 up front and a 295 in the back. Hell, on the atrocious front wheel drive Pontiac Grand Prix from the early 2000s GM used a 255 in front and a 225 in the rear. Concessions have to be made on some cars.

I don't think you're going to find a lot of "proven data" other than hearsay and lap times with regards to the e30 chassis and max tire size choices. Up until recently this was a cheap chassis to race. Cheap racers go race and see what works and what doesn't.

[LowR3V'in]

so basically alistairolsen is saying it's stupid to run a square setup because lotus doesn't do it that way.
that's what i was trying to figure out
so one word answer for that. understeer.

this guy ran a various combo of 225 to 285 on his bmw and gave a really good detail on
what he was feeling and actual lap times. the squared setup did the best.

https://www.youtube.com/watch?v=Bgz0qF3CuNA

[alistairolsen]

You talk in circles. YOU were the one that came up with an 1100kg criteria. Drivetrain layout is most definitely going to affect tire sizes. A modern base Carrera uses a 235 up front and a 295 in the back. Hell, on the atrocious front wheel drive Pontiac Grand Prix from the early 2000s GM used a 255 in front and a 225 in the rear. Concessions have to be made on some cars.

I don't think you're going to find a lot of "proven data" other than hearsay and lap times with regards to the e30 chassis and max tire size choices. Up until recently this was a cheap chassis to race. Cheap racers go race and see what works and what doesn't.

No I didnt, I pointed out that an E30 weighs 1100kg, and that there are no 1100kg RWD cars with 245 front tyres that I'm aware of, nothing more. Someone else said there were a lack of similar car for comparison, which I agreed with, but looking at a range to either side of that weight still provides a general trend. The only car in my list wearing 245s is 300+kg heavier.


I'd firmly doubt a Pontiac Grand Prix has a weight distribution anywhere near 50:50 and the driven wheels are at the other end. Most front drive hatchbacks run a square layout. The question raised was the comparison between front, mid and rear engined and in small cars, thats a question of whether the driver, seat, pedalbox etc sits in front or behind the engine, the outcome is still generally very close to 50:50.


Indeed, hence asking what people have found to work. The answer to my original question need only have been "I ran 215s last season and they overheated" or "I back to backed the same brand of tyre in two widths and the 245 was faster" - but no one seems to have that.

so basically alistairolsen is saying it's stupid to run a square setup because lotus doesn't do it that way.
that's what i was trying to figure out
so one word answer for that. understeer.

this guy ran a various combo of 225 to 285 on his bmw and gave a really good detail on
what he was feeling and actual lap times. the squared setup did the best.

https://www.youtube.com/watch?v=Bgz0qF3CuNA

No, I'm saying why do it because no one does it that way. Yes I agree most road cars are designed to be understeer biased, but I find it hard to believe a KTM Xbow is.

We must be watching different videos, because what he actually said was that the wide square setup was ok, but probably only due to the lack of power and he'd recommend stock sizes, or the 255/285 staggered upgrade (in the dry, which is what matters most). What the test clearly demonstrates is that the stock 3 series chassis is fairly nicely balanced, but a 320 doesnt have enough power to trouble the rear tyres. Upgrading the fronts improved laptimes in the case of both 255/285 and 255/255, but the upgrade to the rear wasnt worth anything (no power). In fact downgrading the rear to a 225 (small square setup)resulted in only a very small reduction in laptime compared to the stock sizes.

In the wet, the times for the stock stagger and both square setups was basically the same and he discussed the advantages in steering feel in various stages of the corner, so again, no advantage to going square and definite disadvantages to going too wide all round (but then if you're racing, youd be running wets, in a different size, so not really relevent. Also worth pointing out that "wet" in that test is standing water, the asphalt is glossy - far wetter than the average race.)

He then goes on to say that the balance is important, he liked the square setup, but only because it made the rear more lively with the limited power available and finally, his entire test was based on a road car, running a single set of tyres in all conditions.

Which aligns with exactly what I've been saying. If you have a powerful E30 that you're racing in the dry then it obviously makes total sense to max out the rear tyre size, but then what front do you pair it with? That depends on the data you'd get from a similar test. What he wasnt able to test was 285/285 due to fitment, which is the area you're running into with 245s on the front of an E30 (they dont really fit), but the trend is that wider tyres are quicker, a 30mm stagger in that test gave good balance, square was ok with limited power, but worse than the wide stagger.

To me that means if you have 245 fronts on your E30 and you're actually using all of the grip that provides, then you really want 275 rears and cant fit them, not that a square setup is best - Which is what I said at the end of post 28.

That said, if you've spent the time on smaller tyres and have proven data of them overheating beyond their working temperature range, evenly across their tread (i.e overloaded whilst working correctly) then sure, they're obviously warranted and you are in fact under-tyred at the rear, limited by bodywork.