Rallycross Track Width

As i refresh the suspension on my 318ti over the next year, it'd be pretty easy to widen the track with by 1 3/8" ish per side and throw some bolt on flares on. Would the extra width help or hurt me for rallycross?

My attitude is the wider the better.

I forgot to add my Datsun has a 3" wider track width than stock (road race car) and the difference is noticeable

It will probably hurt you- especially in slaloms or tight sections.  Every bit of extra track width is that much further the overall mass of the car has to go to get around a cone.

In reply to ¯\_(ツ)_/¯ :

Yeah, I was thinking that too. I wasn't sure if the added stability, if it was even noticeable, would offset that though. I know in autocross or on track it'd be great cause I could run substantially wider tires. 

I'm going to be contrary here; the car would be 2 3/4 wider I'm pretty sure that won't be a hindrance. If he were talking 6" wider then it might start to be an issue. No idea what kind of course we're talking about, we never used them at rallycorss.

On a 318ti, on dirt, I'm pretty sure I'd be planning to run 175 or 185 wide gravels or snows so it's not like you'll need the tire clearance.  Tom is right that it probably won't be a noticeable difference from behind the wheel but I would say that goes for any added stability just as much as it does any added width.  There have been a number of times where I've pulled off a fast run in rallycross due to the ability to "straight line" a section that other cars might have to turn in, and an inch might have cost me 2 seconds via a cone.

I'd suggest not adding extra width.  I added about 6" total to my ranger and, although it was a freakin blast to drive, it definitely slowed me in the tight sections.

I would only add it if stability is a concern in the current config.  I don't think a 318 is a tippy machine so I would leave it alone.

I've got some 195 snows already, so yeah, not worried about them fitting. In all honestly, I was probably trying to figure out a way to put flares on something without sacrificing performance. I'll probably wait and see what the courses typically look like and decide from there. Very few slaloms/tight sections and I might do it since this car will see some autocross use too. I've got a set of 245s I'd like to use.

It depends on how the widening is done.

Spacers and wheel offset will affect handling in other ways.    The leverage will even reduce the wheel rate to a small amount.

 Steering will be affected too.

 All things to think about.  

The amount you intend is not huge, but still.

I guess I should elaborate on how the Datsun was done; the front suspension uses control arms from another model and then those control arms were lengthened to match the wider rear axle (leaf spring car).

That depends on how long that piece of string is.

It might help, it might hurt, depending on what kind of diff you have, what kind of tires you have, swaybar or no swaybar, what kind of driver you are, what kind of courses you run on and what the surface is like...

Try it and see if you like it.  If anything it would look cool.

In reply to iceracer :

E46 front lower control arms bolt on and are wider, so no goofy offset wheels. Just need E90 tie rod ends to make the steering reach and reversed M3 top hats to correct the camber. Similar deal in the back, 6 cyl Z3 trailing arms bolt in and are wider. The motion ratios will change a tiny bit from the lower shock mounts moving out but other than that it should work just like normal. 

My vote is to only do it if you have some cool negative offset wheels or if you have a good reason to switch to E46 control arms.  If you want to run E46 control arms with 0-1 degree of camber, I think you will need flares even for narrow wheels. 

I believe you can run 17x9 wheels for autocross without changing body work if you get your offsets right.

My car is on stock 15x7 wheels and control arms.  I have a whole bunch of space on the outside of the wheel.  I would probably need more than a 15mm spacer to start running into interference issues.  The camber curve in the rear is absolutely silly and stuff fits that looks like it would rub.

Here is an example of a course setup that favors narrow cars: https://youtu.be/U1W95vOwJ-w?t=36  I don't think I lifted from 0:44-0:57.  I was bouncing off the rev limiter earlier than some of the STIs.  It was scarier in the dark during the second session.

In reply to ojannen :

That's some good info, thanks. I was planning on running flares if I did widen it. I haven't been able to find anyone really running wider than 225's on a ti so i wasn't sure what would fit. I may just leave it for now and if our rallycross club tanks, it'll be an autocross only car and I'll widen it and run the widest wheels/tires i possibly can. 

Side note: i see you're in MR, what all have you done to your ti?

A Z3 steering rack will help quicken the steering response.

It won't increase the mass going through tight sections, it'll increase the volume. If you're lifting the inside around any corners, go for it. Especially if lengthening suspension travel isn't currently an option. Longer travel and softer springs would be best, but a moderate widening of track with better arms and a quicker rack would be a decent alternative. 

In reply to shagles :

The frontend is pretty much the same as the 325i and 328i that were the car to have in STX before the twins came out.  Some of those guys are still around and I think they were running 17x9s at the time.  The rear end has a whole bunch of room in board due to the semi-trailing arms.  You just need a high offset wheel.  I think most of the autocrossers used a square setup with a mid sized spacer in the front to clear the control arm and tie rod.

I run locally in MR but my car is prepared legal.  I bumped up because all the good drivers locally were in MR.  I am on Bilstein HDs with stock springs, stock sway bars, lightweight clutch, single mass flywheel, some poly bushings sprinkled around, and a Metric Mechanic LSD.  We have one tarmac-like venue where the sway bars really help or I would have probably removed the front one already.  I welded in a brace in front of the engine to hold the skid plate similar to the one rally.build use to sell.  Take a look at 95maxrider's build thread for how to do it properly.

The only thing I regret is the lsd.  I wanted to stay in prepared so I spent a bunch of money to get a prepared legal diff (3.45 ratio in a small case).  I should have just bumped to mod at that point.

In reply to ojannen :

Ah, true. I keep forgetting that the front is the same as the sedans. I think my wheels are 17x8 et43 so i should be good.

How much difference did the clutch/flywheel make? 

I did them both at the same time.  The clutch is for an M3 and made the pedal quite heavy.  I decided on a medium weight setup so my compressor wouldn't stall the car if it kicked on while idling.

The combination of less rotating weight and a single mass flywheel  made the weight transfer when engine braking much more immediate and predictable.  The downside is that it sounds like it has a rod knock in neutral.  I have had multiple people ask me if I had just lost an engine while sitting at the start line of a rallycross.

I've toyed around with spacers on my e30 (so, same suspension you have, basically). I found that with 15mm spacers on all four it was more stable on higher-speed sections but it definitely felt like it negatively affected tighter turns (perhaps changed the scrub radius and less rear-end rotation). 

Now, one nice thing is that you can use spacers to stagger front or rear depending on course setup. I used to run spacers in a FWD car for autocross to help rear-end rotation. I've messed around with spacers on rear only on the e30 but didn't really love the feel.

For rallycross, I think narrower stance is better for turning, unless you have a tall/tippy car or suspension that tends to lift a wheel off the ground, where a wider track could help a bit.

Tough to say, not knowing exactly what you have going on. I would lean toward "probably won't help anything, but could hurt."

Fender flares.... when trying to get close to cones without actually hitting them, fender flares are just a couple inches "less close" you can get to the inside cone. And additional weight. But I've always said, do what makes you happy. All of us do things on our cars that may not be the best for performance (but look cool).

shagles said:

In reply to ojannen :

That's some good info, thanks. I was planning on running flares if I did widen it. I haven't been able to find anyone really running wider than 225's on a ti so i wasn't sure what would fit. I may just leave it for now and if our rallycross club tanks, it'll be an autocross only car and I'll widen it and run the widest wheels/tires i possibly can. 

Side note: i see you're in MR, what all have you done to your ti?

yikes, why are you going to run 225s?? Even most of the best Subaru guys with more weight and AWD prefer 205s. I usually run 185s or occasionally 205s on the e30. Narrower is better in almost all conditions unless your venue is baked/hard clay or something. 

In reply to irish44j (Forum Supporter) :

Oh no, for rallycross I'm going to run 195's. The 225's comment was about fitting wider tires for autocross.

Good point on the extra space for the flares too. Forgot about that. Man, y'all are bringing up lots of stuff i didn't think about. Glad I asked. 

shagles said:

I haven't been able to find anyone really running wider than 225's on a ti so i wasn't sure what would fit.

In Rallycross or at all? My daily Ti is on 17x8 with a 235. Using the correct offsets I've seen up to 265s front and 295s rear with stock track width.

In reply to buzzboy :

At all. I've been reading through track builds to see what people are running and it's all 205's or 225's. But maybe i've somehow only read builds that were for a specific class that limited tires? Not really sure. That's good to know though, thanks.

shagles said:

In reply to buzzboy :

At all. I've been reading through track builds to see what people are running and it's all 205's or 225's. But maybe i've somehow only read builds that were for a specific class that limited tires? Not really sure. That's good to know though, thanks.

likely because big tires weigh a lot and take more power to turn. And the M42/44 isn't exactly a powerful engine, nor is it a very heavy car. So there's proably a point of diminishing return with going wider than the 205-225 range as far as improving corner grip vs. losing acceleration out of the corners. There are enough guys tracking those cars (and regular e36s, and e30s which are pretty similar suspension) that the "what most people are running" is probably the best answer for tire size. SpecE30 racing series, for what it's worth, uses a 205-width tire. And a Ti is more similar to an e30 than to an e36 underneath.