Help Me Choose a Gear Ratio (Final Drive)

[Bimmer-Bob]

Originally Posted by TheAxiom

Wait.. under what? Meaning I can use a 3stage manifold??

In SP yes, in ST no.

[andrey_gta]

As much as I like the 3.46 (or 3.38 or maybe if possible the 330i/130i auto 3.64)...
I believe they are harder and more expensive to achieve because a 3.73 pumpkin is a direct swap and is a cheaper path. While the others need Flange swaps on each side and sometimes the input shaft flange.

[Bimmer-Bob]

Originally Posted by andrey_gta

As much as I like the 3.46 (or 3.38 or maybe if possible the 330i/130i auto 3.64)...
I believe they are harder and more expensive to achieve because a 3.73 pumpkin is a direct swap and is a cheaper path. While the others need Flange swaps on each side and sometimes the input shaft flange.

I had written off the 3.46 because I'd only ever seen them in the "big pumpkin" size for the 135i, too - but like I said, I can apparently get a 3.46 PG diff in the right size at no additional cost.

[andrey_gta]

2004 e60 525i & 530i M54 pre lci has a small pumkin and a fined dif. Only the input flange is odd. I think those have good ratios

[Kgolf31]

Originally Posted by Bimmer-Bob

Good news! Getting deeper into the SCCA rulebook and, although there is no specific allowance for gear ratio swaps in the SP classes, there is an "update/backdate" rule that would allow me to fit any part from another vehicle in the same line of the relevant appendix, so long as I maintain factory mounting point, etc. So that means I can legally fit anything that came stock on any variant of the 128i, 135i, or 1M! While I still don't think the car is very competitive in ASP, and certainly less so than in STX, it's still way better than SM.

I had hoped this discovery would make the decision for me on which ratio to choose, but not so much: AT 128i's came with 3.73 gears and AT 135i's with 3.46 gears. Back to square one, lol.

I'd hold on until this upcoming Fastrack Letter (released the 20th of this month) for a decision on separating the 128 from ASP.

It will be either BSP or DSP. I do not know the final answer. I, along with other wrote letters to reclass it.

If/when that's the case, you will be only allowed to update/backdate within the 128 bloodline

[Bimmer-Bob]

Originally Posted by Kgolf31

I'd hold on until this upcoming Fastrack Letter (released the 20th of this month) for a decision on separating the 128 from ASP.

It will be either BSP or DSP. I do not know the final answer. I, along with other wrote letters to reclass it.

If/when that's the case, you will be only allowed to update/backdate within the 128 bloodline

Thanks for the heads up.

That would mean 3.23 or 3.73. And I had pretty much just decided on 3.46! Although it does make much sense to class the 128i in SP separate forgot the 135i & 1M.

Any idea how long it takes for them to announce a decision? It seems like it would be a long time. I hate to keep my builder in limbo...

Oh wait, I just saw that the decision is due on the 20th. That's not too bad.

[Kgolf31]

Originally Posted by Bimmer-Bob

Thanks for the heads up.

That would mean 3.23 or 3.73. And I had pretty much just decided on 3.46!

Any idea how long it takes for them to announce a decision? It seems like it would be a long time. I hate to keep my builder in limbo...

Oh wait, I just saw that the decision is due on the 20th. That's not too bad.

Letter has been in for like 6 or so months.

Which is good, because if they're going to decline a letter it'll be pretty much instant, however if it stays within the discussion board they feel the move is necessary and try to find the right spot for it.

The 128 will be moved out (from the sources I've heard), just a matter of where.

[Bimmer-Bob]

Originally Posted by Kgolf31

Letter has been in for like 6 or so months.

Which is good, because if they're going to decline a letter it'll be pretty much instant, however if it stays within the discussion board they feel the move is necessary and try to find the right spot for it.

The 128 will be moved out (from the sources I've heard), just a matter of where.

Was there a public proposal in Fastrack or somewhere else? Would be interested in reviewing it.

I do think BSP is a better fit than ASP, for sure. A little annoying as I had convinced myself that a 3.46 final drive ratio was the way to go, and was on the cusp of ordering one. I do greatly appreciate the heads up, as it would've been extremely frustrating to get this news while the diff was being built!

So now the only question is do I stick with stock or jump up to 3.73? Honestly, I'm leaning towards the latter. Highway driving will be fine, I'm just wondering if I'm going to be bouncing off the limiter all the time during AX? I think short, technical courses should be fine. The faster courses (like we have at Cherry Point) might be more problematic, but I'm moving this summer and so will be competing at a different site for the next 3 years or so don't know what the layout will be like there (Puget Sound area - anyone drive at Bremerton Motorsports Park?).

[Kgolf31]

Originally Posted by Bimmer-Bob

Was there a public proposal in Fastrack or somewhere else? Would be interested in reviewing it.

I do think BSP is a better fit than ASP, for sure. A little annoying as I had convinced myself that a 3.46 final drive ratio was the way to go, and was on the cusp of ordering one. I do greatly appreciate the heads up, as it would've been extremely frustrating to get this news while the diff was being built!

So now the only question is do I stick with stock or jump up to 3.73? Honestly, I'm leaning towards the latter. Highway driving will be fine, I'm just wondering if I'm going to be bouncing off the limiter all the time during AX? I think short, technical courses should be fine. The faster courses (like we have at Cherry Point) might be more problematic, but I'm moving this summer and so will be competing at a different site for the next 3 years or so don't know what the layout will be like there (Puget Sound area - anyone drive at Bremerton Motorsports Park?).

The proposal is to separate out the 128 from the "turbo" variant. It's no question the car doesn't deserve to fit into ASP, especially since the 135i and more importantly the 1M is there. I suppose you could update your 128 into a 1M but at that point why don't you just buy a 1M? lol.

The Letter Number is 17104

The December Fastrack will be available here when updated: https://www.scca.com/pages/fastrack-news

It doesn't go public until published there.

[Fume]

Originally Posted by Bimmer-Bob

Was there a public proposal in Fastrack or somewhere else? Would be interested in reviewing it.

I do think BSP is a better fit than ASP, for sure. A little annoying as I had convinced myself that a 3.46 final drive ratio was the way to go, and was on the cusp of ordering one. I do greatly appreciate the heads up, as it would've been extremely frustrating to get this news while the diff was being built!

So now the only question is do I stick with stock or jump up to 3.73? Honestly, I'm leaning towards the latter. Highway driving will be fine, I'm just wondering if I'm going to be bouncing off the limiter all the time during AX? I think short, technical courses should be fine. The faster courses (like we have at Cherry Point) might be more problematic, but I'm moving this summer and so will be competing at a different site for the next 3 years or so don't know what the layout will be like there (Puget Sound area - anyone drive at Bremerton Motorsports Park?).

I went to Bremerton Motorsports Park maybe half dozen times this summer and the area is basically 2 long runways. This kind of restricts the course layout to be zig zagging from the left side of the runway to the other side with a turn around somewhere. So some of the courses can be pretty fast but often it zig zags enough to restrict speed.

The one other area I did autocross in Washington is at Packwood, which I liked a lot more but it's much further from Seattle. The layout there is a big squarish parking lot. The time I went there the course was much tighter.

There's also autocross at another airfield run by WWSCC but I have not tried going there before so no idea what that one's like.

I have some videos on youtube here if you want to get a sense of what the courses were like (don't mind my terrible driving, I'm still learning!). This one was at Packwood:

This one was at Bremerton:

[Bimmer-Bob]

Originally Posted by Fume

I went to Bremerton Motorsports Park maybe half dozen times this summer and the area is basically 2 long runways. This kind of restricts the course layout to be zig zagging from the left side of the runway to the other side with a turn around somewhere. So some of the courses can be pretty fast but often it zig zags enough to restrict speed.

The one other area I did autocross in Washington is at Packwood, which I liked a lot more but it's much further from Seattle. The layout there is a big squarish parking lot. The time I went there the course was much tighter.

There's also autocross at another airfield run by WWSCC but I have not tried going there before so no idea what that one's like.

I have some videos on youtube here if you want to get a sense of what the courses were like (don't mind my terrible driving, I'm still learning!). This one was at Packwood:

Thanks for the info! I'll be moving to Whidbey Island, which is unfortunately not terribly close to either of those sites. I think Bremerton is 90 or 120 minutes away, and involves a ferry ride. Where is Packwood? East of the Cascades?

[Fume]

If you're in Whidbey, Packwood might be even more annoying to get to unfortunately. It's near Mt Rainier, maybe on the south east side of it, still at a decent altitude. Although, the drive through the mountain to get there is a nice drive when there's no traffic.

Google map link to the town:
https://maps.google.com/?q=Packwood%...hl=en-US&gl=us

[Bimmer-Bob]

Thanks to everyone for your input.

I had all but decided on 3.46 gears as a good compromise between stock and aggressive gearing - I was only hours away from an order, in fact - and then this SCCA re-classing bombshell dropped. I think it's actually a sensible move (if it goes through), but it does affect my choice of gear ratio, at least if I want to compete in SP rather than SM. I'm not 100% sure that that's even important to me, but honestly, if I'm not building for autocross I almost have even more reason to go with 3.73 gears because then I don't care so much about a shorter 2nd gear, and it should be more fun just about all the time.

So it's kind of a catch-22: probably the ideal AX ratio will negatively impact my classing, and the "who cares, I just wanna have fun" gearing nets me more favorable classing.

Oh well, I'm just going to go for it. The fact that Quaife sells a 3.73 gearset for the 130i (which has slightly shorter 1st, 2nd, and 3rd gears) makes me think this will work. Here goes nothing, I guess.

[631twentyeighteye]

I think personally i'd go with 3.46, but that's only because my driving consists of a ton of highway. If that wasn't the case the 3.73 would be ideal. I've always felt that the gears are way too long and shortening the final would really wake the car up. I personally don't care if i have to shift more or if it slows my 0-60 time. As long as the car is fun to drive nothing else matters!

Can't wait to hear your feedback. An LSD is really one thing i've been wanting it just hasn't been in the cards.

[Blacksport]

The transmission's the problem...or rather BMW's choice of gears for the 6 speed. I'm getting ready to install the Wavetrac in mine and would love to put the 3.73 in there, IF I could change tranny gears...

Much taller 1st...
4th is now the "straight-thru" gear, not 5th...
5th is now the old 6th, and 6th is even taller for highway...

[dailowill]

Originally Posted by 631twentyeighteye

An LSD is really one thing i've been wanting it just hasn't been in the cards.

Time to change your cards! Even with the stock gear ratio, I think that it was worth it for me. I definitely have more traction and the traction control kicks in a lot less. If I had to do it over again, I'd spend a bit more to find someone who would put in a 3.46 final drive ratio.

[Kgolf31]

Don't forget you can play around with a bigger sidewall (if possible) to offset gearing

[Bimmer-Bob]

Originally Posted by Kgolf31

Don't forget you can play around with a bigger sidewall (if possible) to offset gearing

Actually, with 18" wheels and the 7200 redline of the AA tune, I can get just to 60MPH in 2nd. I don't have an 18" square set up and don't know if the extra unsprung weight is worth it, though.

[Bimmer-Bob]

Originally Posted by Kgolf31

The proposal is to separate out the 128 from the "turbo" variant. It's no question the car doesn't deserve to fit into ASP, especially since the 135i and more importantly the 1M is there. I suppose you could update your 128 into a 1M but at that point why don't you just buy a 1M? lol.

The Letter Number is 17104

The December Fastrack will be available here when updated: https://www.scca.com/pages/fastrack-news

It doesn't go public until published there.

So it looks like they're agreeing that ASP is the wrong place for the car, but that they think DSP isn't a good fit either. So they're seeking comment about moving the car to BSP. How does this work? Do you just draft a letter and reference the proposal number? Or is there an official form or something you have to use?

Also, what does this mean, really? Are they just kicking the can down the road? How long is his comment period open until they make a decision? And then how long after that until classing is actually changed - 2017, maybe?

[Kgolf31]

Originally Posted by Bimmer-Bob

So it looks like they're agreeing that ASP is the wrong place for the car, but that they think DSP isn't a good fit either. So they're seeking comment about moving the car to BSP. How does this work? Do you just draft a letter and reference the proposal number? Or is there an official form or something you have to use?

Also, what does this mean, really? Are they just kicking the can down the road? How long is his comment period open until they make a decision? And then how long after that until classing is actually changed - 2017, maybe?

They are waiting member comment, but it'll probably end up in BSP. Just write a letter as commenting on that.

Nothing proposed is going into act until 2017