The Ultimate Syncro Big Tire/Gearing-is going big worth it?

[esmukarlis]

[Steve M.]

So with all the talk of the 6 tooth pinion 35:6 & 37:6 not being as strong as the 4.86 / 34:7 pinions how many of the 6 tooth pinions have broken?
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[T3TRIS]

Well, this has been an interesting read…
We recently discovered (after playing in the pit at Mogfest) that 3 of our 15” steel rims are not true anymore. I’m pretty sure this classy syncro move alone is responsible for 2 of these steelies now being compromised and for our seat boxes to now have plenty of UCA clearance.

To make a long story short, this accelerated our time table for installing our CLK wheels... We were going to wait and source a 5th wheel before putting tires on these but things just changed.
We currently run these 15" steel wheels with 215/75-R15 General Tire Grabber AT2 tires. We've been very happy with the combo so far but have always been jealous of the friends we go off-roading with that have larger diameter wheels and seem to crawl over stuff easier (this was before I understood more about R/P ratios and such, which are still obscure to me).
We have a modest Subaru EJ22 and a recently rebuilt transaxle with all gearings and ratios kept stock.
We don't mind driving slow on the highway (usually averaging under 70mph) and I always keep an eye on our tranny temps, which rarely go over 135º/140º unless it's hot out and/or we are doing some long uphills.
We like to explore and have fun with our van, but might be coming to terms that it's also our camper and the days of ridiculous off-roading might be coming to an end.
Our van can weight up to 5,500lbs loaded for long trips. We, of course, aren't loaded like that when we go off-roading with does happen relatively often.

My thought with the wheels was that spinning mass was an issue, hence our choice of CLK wheels. The idea was that a lighter wheel would allow us to get a larger size diameter tire without significantly increasing our unsprung mass. I have been browsing tire options for hours on end now, trying to find the best compromise between off-road capability, on-road worthiness (including noise), weight, load rating and clearance. For a hot second I was dreaming of fitting 245/75-R16 with some fender trimming and spacers, but I'm now pretty sure that can't happen with 14" trailing arms. In any case, after reading this thread, I'm also thinking it's just not a good idea with our 4.86 R/P, which is not going to change. I also hadn't really considered that our granny gear would be so affected by tire diameter, but it does make a whole lot of sense.

Anyway, I've seen all the comments, especially the ones pointing out that not many people are bragging about have 29" diameter tires with 4.86 R/P and a gas engine, until someone talked about mostly doing road-trips with the occasional off-roading. It really makes me wonder how we should keep treating our van... Again, it is a camper after all, and not a lightweight tintop triple knob machine.

So here we are again... the age old question of, will we be happy with 225/75-R16 tires or will ALL THE PREVIOUS comments here come back and haunt us saying: "we told you so many times not to do 225/75-R16 with 4.86 R/P."

Isn't it weird how we sometimes just don't want to hear things?
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Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery

[danfromsyr]

think of R&P ratios like the size of your OXEN before the cart..
a loaded cart needs stronger (and slower) oxen
a lighter cart can make haste with younger and faster oxen.

bigger tires and stronger R&Ps will just move the items you end up breaking sooner and more costly.

as for how you use (and abuse) your (own personal) Syncro... I can not offer a comment here that wouldn't be censored..
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[tjet]

Looks like those are Passat steel rims in the photo. Those bend easy. Not sure if you already bought the CLK rims, but I prefer steel rims as they bend vs crack. Also, a 15" wheel will give you more tire sidewall which helps to cushion those types of landings (I'm running 31's)

[T3TRIS]

[syncrodoka]

If you don't want to spend a few $K on r&p swaps and rebuilds then stay with the 215/75/15 tires or a similar sized diameter in 16" if you prefer the CLKs. Without changing the gearing your G gear will be incrementally less useful the taller you want to go with tires and your ej22 will seem like less of an upgrade over stock when you are downshifting in the hills or lugging it, trying to stay in the powerband at the speed you desire. It is easier to heat up a motor when lugging it offroad at low speeds and your MPG will likely suffer across the board.
Big tires cost money

Even with the 215/75/15 tires I found that a R&P swap really woke up my ej22.

[T3TRIS]

[derekdrew]

Just for a bit of perspective if you think about the logic, the choice of ring and pinion is the method that you use to change your G gear (so you can go slower when you are driving slow). THAT'S MOSTLY IT. The reason the choice of ring and pinion are not important to your experiences on the highway are that you can generally choose whatever 3rd and 4th gears that you want. You can usually configure your highway experiences to be *nearly identical* no matter what final drive ratio you are using, just by using the calculator. What you cannot do is to lower your G gear in any other way than changing the ring and pinions. I regard the calculator as especially valid for gasoline engines up to H6 3.0L, but not diesel because the calculator under-emphasizes the effect of making large jumps between gears, a hostile experience for diesels because diesels have a narrower RPM range in which they are really happy and these engines don't like big jumps between gears. If you have ever been driving your van in muddy rocky wet terrain and you said to yourself, "This is impossible..... I am going to wear my clutch out super fast trying to drive slow enough in this terrain" then this is the panic that you would experience that would drive you to a higher number ring and pinion. SVX engines can use the calculator, but the calculator does a poor job of helping you pick 4th gear for that engine because it has so much torque that it can operate at a much lower rpm at 70mph than a 2.1L, 2.2L, 2.5L, or 2.7L that were the typical gasoline engine choices when the calculator was made. I've been wanting to make a diesel engine version of the calculator for many, many years. Such a calculator would be extremely important for diesel folk because the choice of all the gears for diesels is critical, and it would help people avoid mistakes. But every time I have absolute clarity about what needs to be in the diesel calculator, I get distracted and then I am not sure I am remembering the number correctly. ALL numbers in the calculator proceed from the choice of 4th gear..... how many rpm do you want to do on the highway at 70mph. ALL the other gears nearly select themselves once this election is made, with the other choice being.... "How slow do I want to be able to drive in G gear?" The latter question influence$ what final drive you are running. If somebody was bending their wheels driving off-road as mentioned earlier in this thread, one way to reduce this bending for any wheel is to drive slower in G gear. Another benefit to running a higher number ring and pinion is that when driving in terrain like that, the lower speed means there are fewer objects flying around inside the vehicle and threatening the occupants heads and making a huge mess. Having a huge engine like an SVX, because there are gobs of torque for slow driving, in some sense simulates some of the benefits to be had from a higher number ring and pinion. I think such engines would be practical for syncro if one could get digital temperature probes in both the front and rear gearboxes and configure either an intolerable alarm to go off pointed at the driver when the temperature was too high, or alternatively and better yet, cause these thermometers to tell the engine to lower its torque and hp automatically to keep the trans' internal temperatures down. Then all you would need is a passenger good at doofus wacking the driver hard if the driver should throw the full force of such an engine at the trans when the trans is cold.
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Derek Drew
derekdrew - a t - derekmail - dott - com

[T3TRIS]

Well, that’s a lot of interesting information!
You speak of temperatures in the front and rear gearboxes by the way, what are those temperature limits according to your knowledge? I’ve heard 180° is the absolute max-you-gotta-stop for the transaxle (some bearing gets loose), is that the case?
And what’s the minimum temperature? We put a sensor in the oil galley and it rarely goes above 145° under load (uphill when it’s warm). It often takes quite a while for our tranny to get over 100°, especially if it’s cold out.
I’m probably the one who mentioned bending wheels, though honestly that was being stupid and the wheels were from a Passat (a 17lb 15” steel wheel). I forgot to update this thread but we ended up getting 225/70-R16 Hankook Dynapro AT2 tires on our CLK wheels. It took me forever to come to peace with that decision but it ended up making some sense. We were originally committed to CLK wheels before I fully understood gear ratios in relation to wheel diameter. When we got the van, it had 215/75-R15 wheels and that’s all we’ve experienced, including off-roading in granny gear with a stock R/P. So we went from 27.7” to 28.4”… I thought about keeping the diameter similar but that would’ve been at the expense of sidewall. Truth is, we gotta stop using our van as hard as we currently do, we acquired a 1987 Suzuki Samurai for this!
So… we have a slight loss of low gear performance, a slight increase in overall benefit of larger diameter (going over rocks, holes and such, sure not as slowly), a slight clearance increase too. We have stock R/P and overall gearing and our EJ22 just WANTS to drive at about 70mph now. Of course we have to downshift a little sooner on hills… but then again, might as well preserve 4th gear a little more
In the end, staying with stock gearing (we made that choice before I understood all of this) with our EJ22 and having 225/75-R16 wheels on CLK’s that weigh a total of 46lb per wheel (1lb less than our 15” steel wheels with General Tire Grabbers AT2 215/15-R15) seems to work quite well! Freeway performance, which is realistically where most of our miles are done anyway, is GREATLY improved and much more quiet. I also hope that the light weight of the rim/tire assembly will be relatively gentle on the drivetrain.
We went off-roading in slippery conditions and the tires performed admirably, I was very impressed (I doubt the more aggressive Grabbers would’ve done any better). You can see a video of a climb that other rigs couldn’t do without lockers here: https://www.instagram.com/p/CVbjJzfp5y8/
We can still air down quite a bit for forest road comfort and off-road maneuvers. I haven’t missed the slower low gear as much as I’ve enjoyed the other benefits, so that’s good!
The only issue is that I had was we had to trim the back of the front fenders for the wheels not to rub, which really wasn’t that big of a deal.

_________________
Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery

[Sodo]

[snowsyncro]

I just wanted to say how great it is (I think) to see Derek Drew chiming in here.

RonC

[Jake de Villiers]

What Ron said!
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[Busfixer]

This is all very interesting!

I designed my Syncro transmission for my 1 family owned 1988 2wd Westfalia as follows: 5.43 original R&P, stock 1st and 2nd ratios, 1.18 3rd and .77 4th. All built by Matt at AA. RMW 2wd adapter. Big Shot shifter. Aluminum gear carrier. Oiling plates. Peloquin TBD and air locker. Rhein 15” alloys with 215/75R15 tires - BFG MT in back and Gen AT on front. Gowesty lift springs, Bilstein XHD shocks, T3 parts, SA big brake kit. Fresh Rocky Jennings 2.3 with performance package (numbers matching).

Big thanks to DD for his Excel gearing spreadsheet. This combo should run slightly higher overall ratios in G, 1st and 2nd, stock in 3rd, and lower in 4th.
I still am curious as to whether .82 or .77 4th will be the best choice. I do not have the Bus out of the garage yet, so time will tell.

I live in Texas where the roads are long and flat. 75 mph is desired cruising speed. This combo reflects more of an improved stock approach rather than a conversion engine approach to tire size and gearing.

Will report results once I her ‘er on the road!

Thanks, Busfixer

[Sodo]

I’m currently researching this (Syncr trans in a 2WD)

Where did you get the front mount?
Did you lower the trans for higher body lift?

New rebuilt Syncro trans, not run yet……
Recommend to “keep vigilant” about the break-in trash “until its gone” and magnet comes out clean.
NOT chew on it for 500, 1000, 2000 miles then “wish” you would have dumped it early “& often”.
Gear oil is cheap in comparison, very, very cheap.
Like $20.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Busfixer]

Sodo -

1) I may have purchased one of the last 2wd adapters from RMW 2 or 3 years ago. $650 or $700 if I remember correctly. Had Matt install it during the transmission overhaul.

2) No lowering of engine, just a switch to new Lobro 944 CVJ’s using original VW axle shafts. HD cv bellows sprayed with Wd40 once a month.

3) Read/sourced all of this on the Samba over the years. The best car site I have ever seen!

Thanks, Busfixer

[Russel 235]

Is going big worth it? This is a question that depends on so many personal factors not mechanical factors. As to mechanical factors the awnser in NO.
The bigger you go the more frequently you will need a gearbox rebuild and more likely you will brake things. You will also need more power to push your vehicle and again thin adds to the shorter gearbox lifespan and the chance of braking things.
Pinion ratios: this is not a case of simply deciding I want to cruise at 70 with an RPM of 3000. Different syncros need different ratios. The setup of your syncro determines this. Weight, hightop, tintop, poptop, tire size, tire tread pattern, final drive ratio, engine HP and Torque at specific RPM.
Get this right and it gives you the best drive with the best economy. Get it wrong and it can still give you a decent drive but bad economy or just a bad drive.
5.43 is the nicest crown and pinion ratio for road and off road use.
I personally like the 6.17 as it is great off road but it is the weakest of them all so most of my personal build use the 5.43
4.86 on 215 75 15 tires and a 110 BHP tdi is not bad but with bigger tires than this you lose the slow crawling ability.
A 2.1 with 4.86 and 215 75 15 tires is already on its drivable ( comfort ) limit.

[Busfixer]

My 1988 Westfalia Prerunner is finished and on the road. I reported as above that I installed a Syncro 5.43 transaxle with 1.18 3rd and 0.77 4th. Running 215/75R15 BFG MT tires on Rhein rims. 2.3 RJE w/ performance cam.
The Bus runs great! I shift at 4000 rpm and the wider gearing is not noticeable. The modified WBX is quick in 1st and 2nd, good in 3rd and takes a while to get to 70 in 4th. I'm pretty sure my new target speed is 70 (3600 rpm) instead of 75 mph (3900 rpm). Better mpg (1 and more stable in crosswinds, especially with the GoWesty lift springs. Cruising at 65 doesn't create enough hp and torque to fight our 30 mph headwinds out west.

As a footnote, I would consider a 5.43 r&p with a .82 4th if I had a stock 2.1 MV digifant. The 2.3 RJE just has enough power to run the 5.43 with a .77 4th. In both of these cases I am referring to 215/75R15 tires. Of course, run Derek Drews gear calculator in Excel to determine your final numbers.
Happy Trails,
Busfixer

[Busfixer]

Make that 18 mpg. Not sure where Mr Happy Face jumped into the post!
Busfixer

[chrismsnt]

Just to add to the mix... I have a 1.9 Tdi on my 16" Syncro. I had BF Goodrich All-Terrain T/A LT235/85R16's put on it as well as rebuilt my transmission with:

5.43 R/P
VW M/S - Mainshaft only
1st Gear
GT 3rd 1.18
GT 4th .82 S/C
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1989 T3 Vanagon 16" Syncro
1967 Squareback
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