Boxer suspension upgrade

Front end float at high speed was a well known aero issue in the entire Boxer line. Its one of a few reasons all the race cars front ends were worked over.

355 had the same issue at even lower speeds and we found dropping the nose helped quite a bit but BB already has ride height related issues so not really a good solution.

Be very careful dialing out understeer. Its followed by pretty dramatic oversteer. Reducing one will enhance the other. They have been known to bite.

Dick Fritz did all the development work on the race cars for NART. I was just with him last weekend and am happy to report he is doing well. Might see if he has any input. He might even have some parts.

 

Exactly correct. I would proceed in baby steps.

 

If you're changing wheels and tires slightly smaller diameter front tires will drop the front without altering steering geometry. A bit of rake imo is always good, gives you a good angle of attack for high speed.
If there is front end float on a BBI its well past 150mph, and how often are we running those speeds, ive found you can pile into a corner blow 140 really securely.

As for understeer, yes its a good idea in many cars, I guess the real question is where its inception starts. With wider rear rubber on the Bb like 275 rears its going to understeer anyway, but youll run out of seat bolstering and be plastered against the door before then, so imo your looking for steering feel at roadable speeds more than worrying about understeer which with modern rubber will be really far off.

That all being said boxer rear geometry and crankshaft height is such that I'll bet even with wider rear rubber snap oversteer/spin will happen near the limit if you rapidly close the throttle on a bend at pace, thats true of many cars. A boxer in general is a steady in in faster out car, the wider rear rubber just gives you a major cushion for correction near the limit otherwise missing in the stock setup.

As for understeer, in my experience you can feel the wheel start to go light and subtle vibration in the rim as the front end starts losing grip and scaberign across the surface, then you know dont push further, you can even subtly play with the front on this limit just with the throttle, easing up ever so slightly to regain grip and sharpen turn in, or adding slight power to run a little wider. Obviously if its a decreasing radius bend and you chop of feather the throttle it can happily spin in a second, once again the wider modern rubber provides a far bigger margin/cushion. in gneral I go fast in to bends I know and once i can see out the bend and are off the apex you can just pour on the coals. Thats a good rule for any fast road driving. However unlike a modern with nannies the boxer will be far more unforgiving of a clumsy hand and rapid weight sifts due to you coming off power on a bend

On TRXs I caught mine once, it took 4 lanes of a 2 lane either direction road, and I spun it once but never hit anything either time, young and lucky. I can say that the spin when it comes on is extremely rapid and superman is not quick enough. In my case it was simply too hot into a corner and I merely then attempted to feather the throttle a little and cowabunga before I could think. Pretty much any mid engine car when it starts to spin is going to be far harder to catch. Think of understeer in a BB and safety fuze, but also realize that with he great shocks youre thinking of and wider rear rubber you'll have to really provoke it to get into trouble, like stabbing the brakes on a bend.

Where those limits are on modern rubber, took min 12 or so years ago to a small track, at the time I had michelin ps2s 275 rear 245 fronts, lets just say in 3rd gear you couldn't provoke the rear out no matter, and body lean seat bolstering were real issues. I imagine somewhere deep into 5th gear too fast on a bend chop the power and its all over but thats true of almost nay car. lest put it thsi way, a boxer with modern rubber is far more stable forgiving etc than an air-cooled 911 with same rubber.

 

I don't know what tires you're thinking of, Im currently running 275 rears and 235 fronts, on 17 in rims seems to work out great. The only reason I'd go with 255 rears is so maybe I could do 225 fronts. Wiht the 275 rears and thre carobu rims I have there was not a good fit for 225 fronts, either diameter would be more or too little. yes my fronts have slightly less diameter than the rears. Don't remember all the math but this gave me overall slightly elss ride height than stock or mayeb the rear was close on the same and slightly less in front adding some rake. Imo the last thing you want is more diameter in the rear, that's just going to blunt performance/acceleration. Tires of course have lots of choices that also depend on rim size and width. Probably even a more modest modern tire rating like an all season performance tire is better than a trx. In my case i went for max performance summer tire, whatever are the latest greatest continentals dont remember the name . While Im mostly a Michelin man, Conti made them in the sizes i was looking for and the tire rack reviews were very good.

Reading my prior post, realize I didn't address understeer. While a Mclaren f1 is clearly a very different and far newer machine, it fronts are 235's, and that car has never been accused of lacking or ana understeerer. True many modern cars have huge width fronts, but those cars are way heavier than a boxer and have power steering, so any feel is artificial.

Id go with 225 or 235 fronts, if you feel that there is too much understeer that can be easily dialed out by adding the little more negative camber to the front end. However Im willing to bet that with modern rubber you're not going to find understeer an issue, the issue is the TRXs are truly just crap. As to springs, well if youre going with TTX then theres lots of adjustment improvement to p-lay with just on the shocks before you need worry about springs, but its also true that with a TTX you can go stiffer springs and probably get better ride anyway and improved handling body/lean. Not sure why youre contemplating stiffer in the front, as a general rule that will reduce roll in front but increase tendency to understeer, maybe increase front an rear by similar percentages and then work out the sublties with shock settings. If you find the front bottoming out that's more likely to be currently worn shocks. Springs are also a fine art, it is my understanding that some modern quality springs with he same ratings vary in repones by manufacture, the better ones being more linear.


There is also a rule of thumb on track, and it applies on road, when it comes to suspension to the extent possible, change one thing at a time. You can imagine that manufactures spend years getting it all just so on a particular car trying so many options each day almost.

Boxers imo have something many moderns lack, and that is good suspension compliance, but they all have way too much lean esp with the forces modern rubber can generate and in general could be a little more buttoned down. Secondly steering feel, well lets say when i had a countach once above 80mph and it lightened up, that steering was in a different orbit to a boxer.

In my somewhat limited experience front end feel on a boxer comes from new bushings and steering rack, with narrower front tires.

I guess on a boxer were looking for less body lean, ie a flatter cornering stance, with still very good compliance, improved steering feel and greater precision. Shocks tires should take you a good part of the way there, after that maybe springs. The more controlled body movements are (less loose) the more precise handling is especially in transitions from r to l etc., and the biggest contributor there is shocks. lotus and latterly Alfa are two companies that figured out you dont need ultra stiff springs ina road car, what you need is really great shocks to control body movement very well while allowing the suspension to articulate.

 

A cobra has a lot of weight in the front and a pretty unladen rear, so the rear will let go long before prob due to power and be easier to gather up. Front engine cars can do lurid controlled slides, you don't see that too often in mid engine cars, and even then only on modern ones with systems to prevent it all getting too far. Stands to reason with all the mass centred once rotation starts harder to stop, more like a spinning top thana pendulum, thats part of what makes a me car such a fast turn in handler and better able to use the max of all 4 tires but so hard to gather up. the worst imno are modern audis where the a fair bit of the engine sits in front of the front axle, of sourse when a bend comes the heavy part of the car wants to then keep going straight, so they use massive width front tires and electronics, most anything can be made to work even if not ideal. And boxers despite that heavy crankshaft sitting up high and less than mnodern suspesion geometry can be made to work way way better.

yes you can save a boxer esp with modern rubber and some nice rear width. Boxers are also cars that talk to you esp from the front end, so yes you can and should flirt with its limits. the caveat is the rear, doesn't talk nearly much and when it shouts mama mia then its oy vey.

Im curious where in FL we can find any roads to flirt with these limits, besides the odd 3000 degree onramp. I hear up by Ocala somewhere, and there is anew private track being built near ft pierce

i posted here years ago the driving impression at good wood on Nick masons BBLM. A BBLM is basically a reclothed lightened boxer with more hp, the suspension and fame really pretty much the same as a road car. It was faster around goodwood than Nicks F40 on the same day, we know a F40 is lighter and Hp between the two prob similar.

 

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I thought the "A1A" sounded familiar.... Sounds like a beautiful coastal highway. Never been on it.

My 20 cents on lowering:
My BBi was lowered when I bought it and I don't know if it was done correctly or not, but I put it back. Driveways etc were a real PITA. I recall watching a Lambo Diablo taking 10+ minutes to enter a driveway, and there was a helper placing boards to help the car climb up. This is how my car was. The look was cool, but not cool enough. The handling was surprisingly not-good. Windy roads, smooth freeways, didn't matter. Going straight, it seemed to "hunt" or wander. On the winding roads, the body lean was annoying. After I put it back to stock ride height, those issues disappeared.

The other side to suspension work is, it must be possible as I've seen the 512BB race car run at the Historics at Laguna Seca. At turn #1, there's a large digital speedometer mounted to the pedestrian bridge over the fastest turn on the track. The racing Porsche were asymptotic with 120, and that Boxer exceeded 130.

My summary is how do you intend to enjoy the car? If looking cool in the garage is the goal, setting lap records, or just looking for an excuse to get it out of the garage.

 

Thanks for that picture. Does look beautiful. In CA, we have the PCH (Pacific Coast Highway) which has some beautiful stretches.

Darn good question re how much it was lowered.... I think my car was somewhere around the 1" point, but don't know exactly. Fortunately, it was all completely reversible. Just some time and money. If the BBi front spoiler wasn't always at risk, I might have pursued the lower stance. But even at stock ride height, the car is pretty low, compared to AMG cars etc.

 

Cobra, both 289 and 427 had a rear wheel weight bias. It was something like 48/52 F/R.

 

For me, it's my detox / stress reliever on the day. It's also my hobby to move the car closer and closer to my version of "perfect". I take it out for spirited road driving multiple times a week and work on it even more often. It's too involved of a car (when driven hard) to think about the business, etc.. So while it's not a "track car", it does get exercised pretty well.[/QUOTE]

This

 

That bit of A1/A road looks like palm beach maybe Manalapan. In any event a1a from my experience is a cruising road, maybe 45 mph, with the occasional nice3 s-curve thrown in if you don't mind a driveway part way through.

Im talking more about 50-100+ fast sweepers pucntuated by straights with maybe some 40-60 mph bends thrown in here and there.

or else we gotta find a big track to gently play

I 95 yeah traffic, there are some sections up north a bit that look like maybe at the right time of early am you could perhaps vmax. But realistically I have yet to see a road in fl where you can really sanely exercise a boxer other than for brief staighline bursts. there appear to be a dearth of corners or at least interconnected corners and lots of traffic/cross streets driveways etc.

I do hear up by Ocala and some of the areas around there its different Ill explore.

in the Notheast there are some mountain roads running along rivers and streams where early spring or late fall there are also few leaves on trees so you can see far ahead, or roads running long rovers where when you round a bend you can pretty much see for a mile of so of twists tot he next big cirve and its pretty easy to know there are no cars and or sideroads driveways etc.

There is also the merritt pky in ct 2 lanes each direction separated by a barrier where i have it on good authority you can run for 2-3 miles early am where corners are 4th gear affairs with shift up to 5th before braking and downshifting to 4th mph entry for the next bend power through maybe close on redline just after and then back to 5th.

i woudl say the problem with a BBI is that while it pull great towards redline in say 3rd, realistically the magic is gone by the low 6s, so you may run to redline because youre on a bend and shifting on a bend would be not wise but otherwise you're better off from a speed perspective shifting in the mid 6k range. Thats a function of the flat cams. So just changing the cams will result in a signficantly more enjoyable and realistically quicker car even if headline Hp does not change much. I knmoiw newman has figured out how to make higher lift cams work with the stock FI, Then as the stock rings are not great and realistically the Cr ratio is below 9.0 t0 1 as measured there are gains to be had by doing pistons and going for a real 9.5/1 along with cams, so maybe a real 400hp great tq stock looking motor. Change the FI so you can do some great lift and a bit of overlap and the car will be completly different in very good way. Ina perfect word wed probaly lower 5th gear a touch so its less overdrive given that were unlikely to be cruisng these days for stretched between 120-150 mph might as well have a hard core thrust in 5th up to 170 and redline. gearing ius maybe a complexity and step too far. But whether pistons and cams on a otherwise stock motor or TBU dry stacks and even better cam timing with pistons a BBI boxer woken up is a magical thing.

The nice thing about injection is you still get that low end tractability which is important/useful on modern roads/traffic.

or put another way, imo the BBU boxer is great except that right around 6k when you really want that final charge to the redline it stats going flat, yeah there is TQ there so you can shift and work around it, but realistically its missing that top end charge.

The changes/upgrades being now done will put these cars in another orbit of desirability, certainly for those who drive

 

Maybe Im just getting older (or old) and I don't want my cars to ride like a floor jack anymore, that would be my biggest concern with running solid bushings in my suspension. What are you anticipating your car will ride like with those? How long will they last before they need new spherical bearings? I just put a set of Spax coil overs in a 308 which are lighter than stock and retain a stock type bushing on the ends - and they have adjustable perches which was one of the main reasons for the change. I find coilovers even with poly bushings to be too harsh and they get beat out in a fraction of the time the stock ones do and they transmit a lot of noise into the cabin. Im curious to hear your feedback when it's dialed in.

 

My 02c with solid bushings. On the exige v6 cup when it was new we did a little backroad engine running in and while stiff it worked on road. Over the years moving to ohlins and some way stiffer springs the occasional road test to gather data still yielded a fine road ride. Even solid engine mounts didnt chage much, I gues rubber engine mounts are so at idle running the ac its not too bad.

Howeevr last year we striped the suspension and replaced with solids. On track I noticed the extra precision and to the extent there was way less flex alignments needed to change significantly. However on an engine data gathering trip on the road up the hill behind my house at roadish speed, every crack expansion joint etc ran right through the car.

I think a BB can use more roll control with may be swaybasrs or just swaybar bushings. Shocks certainly can control roll and dive and modern shocks with stiffer springs can yield great ride and better control. There is undoubtably a lot of slop in the BB steering and suspension, and maybe stiffer bushings make sense, but as you alter things other things change and I would be wary on road with solids, so many other gains to make from old rubber bushings before going that far. .

 

Solid suspension bushings, are very hard on chassis control arm mounts.

 

How is the FI project? Nice power increase? I forgot...did you do cams?

 

All sounds good. And it's true...You do sleep better with a Newman diff in the car. Upping compression also sounds like great fun.

Getting a 355 sounds sweet. Prob might be that you get itchy to do a little work on that... Hmmmmm...

 

Well I hope I get mine to Newman before yours does as I have a fairly lengthy list for the internals during the major.