Been giving some thought to the suspension/wheels of the DS project car....It should be showing up at the shop in Portland this weekend, but I'm up in Seattle and need to get some preliminary planning done.

What size are the stock rims (diameter, width, backspacing/offset)? What is the common "plus" size? And, what is the absolute maximum size (width), with correct backspacing (no or minimal track change)? How much improvement is there with the standard GT fender flares?

I'm not particularly fond of the GT fender flares, but I have been offered a free set. However, I'm less concerned about doing something the easy/cheap way than I am about doing things "right", in terms of project objectives. We still haven't finalized what those objective will be, but I'm leaning towards making it a "G-monster", requiring a lot of meat all the way around (285s, or so). I presume that kind of tire/wheel width is out of the question with GT flares? Even if we do more of a street/strip project, I'm planning on at least 245/40R17s (or something similar). Will those fit with proper backspacing?

My prime concern is getting the most rubber on the road without excessively changing the track/scrub radius. If I can accomplish this with the stock suspension, that would save me a lot of fabrication. But, if it just won't work, I'll bite the bullet and do a totally custom double a-arm suspension all the way around and change the track the right way (widen the suspension track, not just the wheel track).

How stout are those rear trailing arms? Looks like they might be a bit weak for the kind of loads I might put on them. How about the front a-arm? Is there much suspension adjustment possible with the stock setup (camber, caster)?

Sorry for all the questions, but deadlines for decision making are looming. If there is a good FAQ somewhere, I would appreciate the link. Thanks!

Try Lindsey Racing for custom Fuchs wheels. They are building a set of 17x11 for me with a modified offset to fit under 11" flares. The rear control arms are boxed with a kit from pelican. In the history pages here Mueller posted the wheel specs for me. I think its under the heading rear flares......

Stock wheels on a 914 were all 5.5x15. Actually, 5.5x14 wheels were an option on the 914-6, and the "no extra cost" wheels on the early 914-4 were 4.5x15. The -4 has a 4x130mm bolt circle, while the -6 has the 5x130mm circle. The 5.5" rims all have about 4 3/4" worth of backspacing. (I don't remember what that works out to for offset.)

There is no standard "plus" size wheel. That's because no other wheels besides Bug wheels fit the 914-4 bolt pattern, and even those don't have enough backspacing to fit anything wider than about 165-width tires under stock 914 fenders.

You can fit up to 205s under stock fenders on stock wheels on most 914s, though some 914s will only let you fit 195s. I have heard that there is some 14" wheel you can use that will let you fit 215s, but I cannot confirm that.

245s should fit under GT flares, assuming you get the right wheels to put them on. You may very well be able to go wider--a lot depends on the exact installation of the flare, what wheels you can find, and so on.

The trailing arms in the back are OK, but there are pieces you can buy to "box" them. This adds to their weight and supposedly to their stiffness. And presumably to their strength as well.

The front A-arms are the same as used on early 911s, and they seem to be plenty strong.

The stock suspension gives you a fair amount of adjustability in camber, caster, and toe. You get more negative camber, of course, if you lower the car. JP has run into camber issues at about 2 degrees negative, which sounds a bit unusual to me... I know of 914s with more than that which didn't have to chop up the fender wells.

There's a decent FAQ that lives in the Tech Articles section of the Pelican Parts website.

--DD

If you want 285s you will need to go with 11' rear GT flares and to get really big meat the 9" in front... However 'I still dont think 285s will fit in the front with those 9" flares. The common GT flare that 99 % of people have are the 7" in the front and 9" in the rear... I know that American International Racing sells the 9" and 11" as well as the smaller set. However their flares are not the best I have seen for fiberglass, but not the worst either... If you want to see what 7's in the front and 11" s in the rear look like , see if you can find a picture of Craig M. yellow car ( called JLo).Personally, I think his car looks awesome.

ls6/914 - Do you have pictures of your flares? Did you buy them or have the fabricted?
If you bought them, can you please tell us where?

Later,
Thom

Speaking of flares and Pelican, How are my flares coming Dave? Larry in seattle......

Thanks for the suggestions so far.

For clarification, if I don't run the GT flares, I will be fabricating custom body work all the way around and the suspension is likely to also be fabricated from scratch in that case (meaning anything becomes possible). So, if I were to do the "G-monster" thing, I could accomodate whatever is required (e.g. 285s). Didn't think they would fit the GT flares, but had to ask. I have zero interest in the larger flares, as I'd rather do something custom at that point.

Also, keep in mind that whatever I do will be four-square -- same tire size all around; not just big meats out back with slightly smaller ones up front. Unlike, say, a V8 swap, I am not throwing the weight balance off and having to compensate for that, nor am I dealing with loads of torque just off idle. My turbo rotary conversion will be 50/50 and those 250+ rwhp will come at higher revs, with flat torque. I am trying to be as true to the spirit of the 914 as possible, but simply take it to the next level. Ultra light, well balanced, low Cg, great handling...PLUS real, linear power.

Wider wheels/tires should help improve cornering force, but if the track changes excessively, then there will be negative consequences detracting from the gains (bigger scrub radius, for example). Probably a necessary evil for heavy/torquey V8s, but I'd like to avoid making those compromises.

If I do the street/strip thing, then it appears the compromises are minimal and I might be able to get away with doing things the easy way. Probably not such a bad idea. At least if I stick to GT flares, I can probably still run it in ITE, rather than Super Production....

Jeez, I'm going to need at least two or three of these things, so I can try every combination!

Thanks again guys and gals. Keep the suggestions coming!

BTW, if anyone is interested, this is a concept drawing (plan and side veiws) of the body modifications I was considering. Nothing too radical. Top is stock (obviously) and bottom is modified. Just a rough conceptualization...

First of all, you will need to convert the car from 4 lug to 5 lug.
This is not only needed for wider wheels, but also for upgraded brakes.

Stock GT flares will fit 8" in front and 9" in the rear
Which would mean 225 front and 245 rear width tires in 16" sizes and IIRC 255 and 275 in 17" sizes.
If you want to go any wider, this will probably quadruple your wheel budget (custom offset wheels). And with your hp plans, it would be overkill IMHO

If you still feel the need to go wider, you might consider the Sheridan body kit
But these require at least 10 and 12 inch wheels IIRC

The rear trailing arms are strong enough as they are. If you use the search function on the BBS here, you'll find quite some debates about the need to reinforce these.
You will be better off reinforcing the the rear suspension pick up points (specially the inner ear)
Much of these reinforcements will not so much be dictated by the 250 hp you plan to make, but the spring rates you are planning to run in the rear.
The main consensus is that if you run 200# of heavier in the rear, you will need to start making reinforcements.
You can brace the inner ear to the firewall in front of it and you will need to dig into the area where the rear shock tower meets the framerails.
Ideally, you should also consider a custom cage that ties into the susp.pickup points.

You can swap the front suspension for a 911 suspension. This will cover the 5 lug conversion.
You should get 911 SC or 3.2 Carrera front struts (which have a 3.5" bolt spacing for the brake calipers). This will leave you the most options for bigger brake conversions.
The front suspension should give you close to -1.5 deg. of camber (although real world experiences have also shown a max of -0.8 deg).
If you need more, you can get custom top strut mounts.

Make sure you browse through the classic threads for good info.

cheers,

Jeroen
ps. I hate the way you messed up my art-work

"Nothing too radical"?!?! What is radical then...

-Steve

This car will be done in time for your 100th issue. Or maybe 500th. You might as well build a tube frame car, it will be quicker.

Paul

Radical is all a matter of perspective. I've done radical...this ain't it. Certainly not a weekend project, but not a lifetime one either. Right now, I need to know what's possible. Later, I will decide what is practical and knock it out.

The question is, what are you going to do with the car?
The answer will dictate what to do.

BTW, What is a "G monster"?

There are trade offs due to the 914s design that require some thought. For instance, the 914s suspension allows a limited amount to lowering before you run out of suspension travel. Tall tires make this more of a problem. There are $olutions, of course, but ya better have a plan before you start spending money.....Mazda prices do not apply to this stuff.

As far as "taking it to the next level", 250 hp & "285" tires ain't gonna do it. There are lots of race prepped 914s that exceed those levels by a wide margin.....a few street cars, also. Bring lotso money to put it on those guys.

Stock fenders:
8" wide rims on front (225's), 7" wide rims in back (205), yea, Porsche played a cruel joke on us


I've driven a 914 with 255's on the front(275 in the back), I wouldn't want to drive one with 285's at slowspeeds unless you add powerassist steering........

Lite weight or not, rolling resistance will not be fun to deal, but it can be done as with anything.

The reason for the "small" size rims/tires on a stock fendered car is for a few reasons.

Front:currently i have 7" rims with a 40mm offset running 204/45/16's......the tire/rim only has approx. 1/4" to 5/16" space in between the strut. There is plenty of room (an inch or so) towards the outside fender...in the past, I had 16x8's on the front with 225's and stock fenders, car lower than stock

rear:i have the same size rim and tire and offset
as the front....about 3/8" between tire/rim and inside fender well (trunk wall)...1/4" to 3/8" clearance between tire/rim and outside fender, rolled lips

"G", as in G-Force; a skid pad/slalom car. "Monster" as in, well, a monster. A G-Monster project would be building an uncompromosed car to give Sir Isaac a wedgie. The other, less extreme, option is a street/strip car, which would be a highly streetable, reliable car with good track manners.



I agree, the suspension is very compromised. It's just a MacPherson packaging job, which provides room for that flat engine and cargo space. This is why I was/am considering changing out everything -- tube the front and back, then run double a-arms (non-parallel unequal length wishbones). The narrower engine will permit this and I don't need no stinkin' cargo space. I can fabricate my own a-arms, acquire components from race shops, or steal the subframes of a number of cars, like the Miata or RX-8. Then, Mazda prices do apply! Hmmm...12.73 inch brake rotors for $150 ea, minus 40% "competition" discount... Math is fun.

I still may stick with the stock suspension layout for a less-extreme street/strip car, but that does not mean I am limited to conventional bolt-ons for hubs/brakes. Once you make the leap to fabrication, anything becomes possible. I can also get pretty much any components at W/D prices, if not outright donated. SEMA is in three weeks.



Racing competitively is not the primary consideration of the project; it only has to be cool. In other words, fun to read about. As I said, this might be a "G-Monster" project to see how great one can be made to turn, or it could be a "street/strip" project where the goals are far more diverse. Road racing is a secondary opbjective that I would not permit to compromise the primary objective. But, it will be fast and I'd like to run ITE or SPM. My real racing effort will remain crewing in Grand Am Cup with production endurance cars (currently an M3, but we have a new car in development). I have no delusions about my driving ability, so any personal track time behind the wheel is just for grins.

Personally, I like the idea of tripling the stock output reliably without weighing more than stock or throwing off the balance. You guys seem pretty happy with less than 100hp. And you are damn near ecstatic over ~130hp. "Taking it to the next level" is adding the dimention of smooth, linear, reliable power to a great handling car without compromising that which made it fun in the first place. BTW, 250rwhp is with a small street port and stock turbo runing low boost. If I want high output, I can run a non-stock turbo, tweek the engine a bit more and get up to 600+ rwhp. My dyno guy puts that much down on his personal 3rd gen RX-7 -- with very conservative ignition timing to boot. Anyway, I'm not a guy who gets too excited about big peak HP numbers. In racing a 600 hp car is rarely much, if any, faster than a 300 hp car. You have to be able to put that power down effectively through four little contact patches and that is not such an easy trick. I much prefer the satisfaction of linear power that doesn't stop until redline...y'know, about 9,000 rpm

Anyway, remember that this is merely an editorial lark -- not a racing program nor a daily driver -- and I am still just in the planning stage. I have yet to 'sell' my ideas to the fabricator, engine builder, body guy, tranny guy, machinist, and whatever vendors I am getting parts from. Oh, and my boss is sure to ask questions when I start turning in receipts, so we all have to be on the same page.

Again, thanks for all the input...especially the critical stuff, as everyone can use a reality check once in a while. Me more than most.

Was the scrub radius increased with that tire setup? In other words, did they just widen the track by sticking the rubber on the outside, thereby creating a mechanical disadvantage? Just curious. 285s would be a nice workout even with proper geometry...

BTW, thanks for the specs on your setup. This sort of info is very valuable for sorting the options. Also, I will probably do a sidebar on stock wheel/tire combos and standard suspension upgrades, so it is usefull there too.

No idea, Larry. I'm not tied in to that side of the house at all.

--DD

Fun discussion. FWIW, I run 8"X15 BBS on all corners with 245/50 s and there is very little clearance on the rear fenders. I don't think I could run 9" wheels with the same backspacing. The 5-bolt wheels came from a 914 track car and I was told they have the stock offset though I never measured to be sure. I'm finding my biggest G limitation is the stock seats!
Also, with the wide front rubber the car seems to follow ruts under braking, particularly at low speeds.
Dave

[QUOTE=Blake,Oct 19 2003, 12:25 PM][QUOTE]
Was the scrub radius increased with that tire setup? In other words, did they just widen the track by sticking the rubber on the outside, thereby creating a mechanical disadvantage? Just curious. 285s would be a nice workout even with proper geometry...

[/QUOTE]
Ayup, the extra width goes outward.

One is limited to about 5 inches backspacing (mounting face to inner rim)....maybe a bit more in front, depending on tire dia.
I use 7 inch rims with 225 X 45 X 15 tiars and they barely clear the works.