All you cats with 275/40/17 rears, consider the 4.3 final drive when swapping diffs!
 

Just got my FD back with the TII diff and 4.3 gears installed (along with RP diff bushings and RE toe links and trailing arms).

A few weeks ago, a fellow forum member (quicksilver i believe, Joe from the carolinas) was in town and we went out for a spin. I made some repeated rolling 5 mph to 110 mph pulls and first and second gear felt ok, but the car really ripped through 3rd gear. The party was starting after 70 mph. This really got me thinking....was it just the weight of the rims and tires hurting me?

For some background info on gearing and how larger rolling diameter affects it (and consequently hurts acceleration) see this thread:

https://www.rx7club.com/showthread.p...ighlight=gears


Initial impressions? This is all anecdotal and none of the changes are earth-shattering. However, my R1 accelerates better in the lower gears, turbos spool faster (with non-seq BNRs this is a huge plus), and after shifts the car has better perceived throttle response. The car just feels peppier, whereas before during around town driving it felt kind of.....ponderous, especially after upshifting and accelerating. The cars feels much more responsive to throttle inputs.

Essentially, I had changed my gearing from the stock 4.1 to an effective 3.9 with the fikses and 275/40/17 rear tires. Not the direction I wanted to go in, so the 4.3s move me back to stock 4.1 and as an added bonus correct the speedo deficiency I had before.

I picked up the 4.3s from www.rx7.com. You'll also need some OEM parts for the swap, with a crush sleeve being the one you absolutely need and side oil seals being a good idea. Some people opt to swap over bearings from their torsen to the TII, but I went with all new bearings.

At any rate, food for thought guys. I am very happy with the results :bluesuit:

As a side note, the 285/30/18 rears come very close to retaining the stock rolling diameter. just fyi :).

I'm thinking of going with those next year (if I keep the car). RTS3GEN who lives in my area just did 4.7s. ;)

Thanks for the right up, but any one with any idea of how gearing works should already know this. Plus the taller wider tires add unneeded weight to your car.

Isn't Art primarily an autocrosser?

I looked into the 4.7s, but the highway cruising rpms would have driven me nuts.

Naw, I don't think Art's ever done an AutoX. ;) He's only road racing and the occasional drag race (he does usually one run a year which he waits until the fall cool weather).

He did say the highway cruising kind of sucked. However, he said the car screams through 1st, 2nd and 3rd (probably all .2 seconds of 1st). ;) He usually trailors the car to events so it's not on the highway that much. He had been running the 4.3s for a few years and really enjoyed them.

I have a 4 speed in the car, so a 4.3 is out of the question.

however, I do have 285/30/18 so my 4.10 is effective. If i still had a 5 speed in the car i would no question have a 4.3 in the rear.

Yesterday I just replaced the Kuhmo Supra 255/40/17 tires, all around, with Sumitomo HTR Z 245/40/17, even thought the thread depth on the Kuhmos were practically brand new. The tires came with my car when I purchased it last fall and, were 5 years old. The previous owner preferred the stock wheels and did not hardly used these.

Tires dry out and harden even if you do not use them. So, it was hard to throw away a set of new looking tires but, had to be done. The HTR-Zs are practically the same size, fit my 9.5" rims perfectly, ride hight is maybe 1/8" lower and grip wonderfully.

Two side benefits to the HTR-Z. First, they are nearly 5 lbs per tire lighter than the Kuhmos, second, they cost only $69.00 per tire from TireRack. I got them after reading through a couple of hundred reviews and they are (the HTR-Z) as good as most reviewers claim. With this combo, my tire/wheel weights are within 1.5 lbs to the stock ones. I can live with that for the advantage of 17" rims and wider offsets. With these I finally went below 2700 lbs on the car with PS and Air still installed.

Initial impression is that the car rides much better over road imperfections, holds better in the twisties. These can easily be explained by the fresh rubber compound vs. the dried out hard old ones. It also accelerated (subjective feeling) a lot better, which must be credited to the alignment that I finally got down and did on the car. The car was set up for the 16" tires had way too much negative camber and had way too much toe-in.

For street use I think this setup is perfectly sensible, stiking a good balance between unsprung weights, rolling resistance and adhesion. I considered getting the light weight Pirelly Zero Rosso, or Michelin PS2 for 3 times the price of the HTR-Z and now I am glad I did not go that way. These tires are perfectly enough for how ever hard you wish to drive the car on public roads. And, hard I do drive them around our twisties...

Now, I would still like those 4.3s, like I had them before but, one thing at a time...

Albert

What wheels are you using and how's about a pic?

The wheels are actually some 10+ year old Forgeline RS racing wheels that I used to race with my first FD and repurchased from the owner just recently. They're 18.25 lbs and 9.5" wide all around.

I'll have a 4.33 gear for sale or trade for a low mileage 3.90 gear in a few weeks. PM me if interested.

Sent PM on the 4.33 gear set.

what's your crusing speed at 3krpm in 5th gear now?

dude whats up with that muffler?

Albert runs SuperTrapps to reduce noise and boost creep.

If you are asking me, it's 80 mph. As stated above, the 4.3 gearset got me back to the stock 4.1 after my Fikses bumped me to a shitty 3.9.

Albert, is that the Mazdaspeed 15th anny rear wing i spy? you should post a thread of pics of your FD :)

Well, that is a strange Supertrapp setup. It should have a full blocking plate in the back and exit the exhaust flows through several layered plates. However, I had found, while I had boost creep without them, it stopped the creep with the installation of the Supertrapps. More than that, it seems, that all I needed for stopping my boost creep was just a tiny bit of turbulance in the exhaust that the Supertrapp provides with just the 24 plates installed but, not the normally required back blocking plate.

The nice thing about this setup is that you can absolutely fine tune the amount of back pressure you need. As far as looks, I kind of like it because everyone wonders what the heck kind of trick exhaust it is... ;)

Albert

I got this wing from a local, Sacramento, parts dealer. Forgot the manufacturer but, it was not Mazdazpeed. The main reason I like the looks because it makes the car look longer and lower by this wing hanging back out over the rear deck.

Been bummed a bit. Installed my new Tokicos and they happened to raise the lightened rear end of the car by nearly 3/8". I can feel it in the handling. That is why coil overs are nice for adjustment.

Albert

Hm, if that's not a mazdaspeed replica 15th anny wing than it is pretty damn close. what's with the emblem, black dragon motorsports ;)?
https://www.rx7club.com/attachment.p...hmentid=175242

4.3s, MEH

its all about the 4.77s
:D

im at 3000 rpms at 60 i think or somwhere around there.

Well, it could well be. I simply do not know if it is a replica.

The "Drago Rossi" emblem means the "Red Dragon". (The front bumper actually has a RED dragon emblem). It is from an Italian white-water kayak company that happens to sponsor me with their line of boats. They are the "Ferraris" of white water kayaks so, why not use their emblem.... just makes people scratch their heads even more about the origins of the car. :)

Pictures:
1) Blue boat is with me
2) red boat is an Italian kayaker. Both in a Drago Rossi model, called the "Mafia".
3) My newly installed Buddy Club seats. They weight 13.5 lbs (advertise 11 lbs) and with the Cobra side mounts directly to the car (no sliders) I saved 34 lbs of weight over the pair of leather seats. They are excellent, quality seats.

Albert

Regarding 4.77 Gears
 

Other than the higher rpm on the interstate, are there any other negatives going with a 4.77? What benefits has anyone recognized with them.

I'm on stock rims right now, but I do nave some 18" Enkei Aegis wheels that will be going back on my 7. What will these wheels offset the 4.77 too? The width of the wheels in the rear are 9.5".

the ms 15th anniversary was widely copied in asia, but the ones I saw didn't get the profile quite right...

This answer is almost 3 years too late, but I'd need to know your tire size to properly answer the question. If you're mounting 285/30s on those wheels, then your gearing won't be affected as that is pretty much the stock rolling diameter :)