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The Ultimate Syncro Big Tire/Gearing-is going big worth it?
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Surfy Murphy
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PostPosted: Thu Mar 19, 2015 5:27 pm    Post subject: The Ultimate Syncro Big Tire/Gearing-is going big worth it? Reply with quote

Calling all 225/75 R16 and bigger syncro owners! Did you go big and love it? Do you pine for the days of your nimble syncro with small tires and stock springs? Is there an ideal compromise? I'm looking for advice and stories from around thesamba campfire.

What's the best compromise on and off road? Can you still hear the radio with your tires? Does it feel sloppy or too stiff now that you've gone up to 29.5 or 30.5"? After 3 transmissions and trying every set of springs available, what's your favorite setup for on AND off-road?

I've already gone down the rabbithole, widened my arches for trailing arms, and added an extended slider to go for bigger tires. Originally I thought I'd just go as big as I can, but now I'm a little worried the van won't be as highway friendly on the way to the beach/fireroad/trail. Matt at AA transaxle has my spare transmission and I have to tell him to do something with it....eventually.

Currently I'm running 225/70 R16s on audi allroads with spacers from t3. Stock springs, soon to be installing rear trailing arms and an ej25 as soon as it warms up a little in NY.

Any advice or stories would be welcome.

Thanks!!
David
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whynotvw
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PostPosted: Thu Mar 19, 2015 7:18 pm    Post subject: Reply with quote

I currently run 225 75 16 with suby 2.5 engine and I like my set up. I did run the 225 70 16 which was nice but, I felt the gap between the tire and the lip was too far.
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Syncro Jael
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PostPosted: Thu Mar 19, 2015 7:23 pm    Post subject: Reply with quote

Just from listening around the campfire bigger means $$$.

As soon as you get bigger tires you either need to change the gearing in the final of the transaxle or get more HP to push the brick around on them. And you should do a bigger brake upgrade to help slow them down. There has been a lot of discussion about tire size, tire weight, as contributing factors in the transaxles not having much of a life expectancy.

I run modest tires at 215/75/15 and push the brick with an EJ22. Wind and grades are still the enemy. Twisted Evil I can see a big difference just going up to a just under 28" tire from the stock size.

Big tires look great, give you added clearance, but will always cost you more in the long run.

I am sure some of the owners that are running the large tires will chime in. Don't get me wrong, I love em, love the look of a lifted Syncro with big aggressive tires on it but I am still cautious about keeping my transaxle for more than one season.
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PostPosted: Thu Mar 19, 2015 8:29 pm    Post subject: Reply with quote

It all depends on your highway driving habits, If it were me I'd stay with the current setup. Even with the ej25 plans. I run the same tire size and stock springs on our 1.8t and ej25. Couldn't be happier, we've had several spring/shock setups with the following motors Tiico, 1.8t, ej2.5, gowesty 2.3

For the trans I would keep the r&p and gearing just the way it is for the ej25

We have the fox shocks on one and stock shocks on the other with stock springs, both ride good. I have a t3 sway bar yet to install on one of them. I do like being able to adjust the fox shocks, I adjust them often depending on terrain.

When I went to the 16" wheels on the tin top ej25, my wife didn't like it at all. She liked getting up to speed quicker. because we put so many miles on em I like the lower rpm at cruising speed with 225/70/16

I would recommend getting the lightest wheels you can find if your staying 16" on a syncro. As far as brakes go I'd just go with the larger bmw booster and leave everything else stock, not worth the money in my opinion. Our stage2 1.8t stops just fine fully loaded with kids and a dog.
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Syncroincity
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PostPosted: Thu Mar 19, 2015 8:32 pm    Post subject: Reply with quote

I had 235/75-15 BFGs on Audi 5KTQ rims initially with the WBX motor, I found the performance acceptable, a bit pokey up hills... stock gearing with 2" lift Schwenk springs. No fender interference unless I hit a dip with the wheels turned to full lock.

After a diesel AAZ coversion I put on 225/75-16 BFGs on Mefro steels, still with stock gasser gearing. The fenders now need to be trimmed like on the 16" Syncros, the fronts will rub hard on the lower aft lip in turns with very little suspension compression. I have plenty of torque now with the AAZ at 17psi, but I'm still wishing for another gear at highway speeds, it's turning roughly 3700 rpm at 75 and it sounds a bit frantic, although it happily pulls the van on up through 5000 rpm. Can't help think that can't be too great for fuel mileage.

The tires are true LT rated, with very beefy sidewalls, which makes for confident handling and no worries about bad roads, but there's a definite increase in ride harshness versus the fatter, softer 235s, I find running them at 25psi helps a lot. Also, the LT tire and steel wheel combo weighs in at a whopping 80 lbs each... Shocked
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Jon_slider
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PostPosted: Thu Mar 19, 2015 9:27 pm    Post subject: Reply with quote

> 225/75 R16 = 16% taller than stock, imo requires a Ring and Pinion change to 5.43
> 215x70x15 = 10% taller than stock, imo the largest tire to use with stock 4.86 ring and pinion

I have used 215x75x15, 225x75x16, 30x9.5x15 all with 4.86 ring and pinion, and currently 245x75x16 with 5.43 ring and pinion. Ive had 5 transmissions, and my motor is Diesel with modified 3rd and 4th. But, my granny, 1st, and 2nd are the same as yours.

by far the best power and gearing combo with a 4.86 ring and pinion was with the 215x75x15, which is a very close equivalent to a 215x70x16

Ive also had a Subaru 2.2 powered syncro, with 27x8.5x14 tires. I am very sensitive to tall gearing and I was NOT happy with 215x75x15 on that van.

Similarly I was NOT happy with 225x75x16 with a 4.86 ring and pinion on my Tdi. It lagged off a stop, and ran 200f higher EGT on the freeway than the 215x75x15 tire.

Since you are going with a Subaru 2.5, I think you will be fine with a 215x70x16 and the stock 4.86 ring and pinion. imo you should NOT change 3rd or 4th gear.

Tall gearing is NOT your friend. It makes more heat, and lower fuel mileage. Tall tires also reduce fuel mileage due to more air under the van.

to run a 225x75x16 requires fender cutouts in front, and shaving the lip of a stock 14" trailing arm.

to run 245x75x16 requires fender cutouts in the rear plus an extended trailing arm with the lip shaved, and front fender cutouts

the lightest rim you can buy is the 14.2 pound forged CLK alloy (the 15" Rhein Alloy weighs 23 pounds), however, you will need 10mm rear spacers if you plan to run CLK's with 225x75x16 and stock center caps, and to clear the trailing arms. Do whatever T3technique.com recommends in terms of hardware and spacers for your chosen rims.

note that a 225x75x16 BFG AT Ko weighs 42 pounds, whereas the 215x70x16 weighs 33 pounds, which is 9 pounds less. Even if you run the 9 pound lighter than stock CLK's, the larger diameter tire will have a severe power penalty, not just from the weight, but moreso form the longer radius at which the weight is located.

I STRONGLY caution you NOT to go 225x75x16 with a 4.86 ring and pinion if crawling slow is important to you. These are just MY opinions, bought and paid for with my own experience, not a criticism of anyone who has different priorities.

People interested in load tables, VW tire inflation specs, and effects of inflation on handling, may find my signature links worth browsing.
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Last edited by Jon_slider on Thu Mar 19, 2015 11:20 pm; edited 1 time in total
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WLD*WSTY
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PostPosted: Thu Mar 19, 2015 9:58 pm    Post subject: Reply with quote

Syncroincity wrote:
The tires are true LT rated, with very beefy sidewalls, which makes for confident handling and no worries about bad roads, but there's a definite increase in ride harshness versus the fatter, softer 235s, I find running them at 25psi helps a lot. Also, the LT tire and steel wheel combo weighs in at a whopping 80 lbs each... Shocked


You may want to refer to the load inflation tables for your tires, since at 25 psi they are likely well below the weight rating for your vehicle. OK for a stretch of sand, but extended driving at that pressure is not the best plan. Better to get the non-LT tire to have comfort AND proper load capabilities.
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kbeefy
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PostPosted: Fri Mar 20, 2015 1:05 am    Post subject: Reply with quote

I have 225/75r16 on my syncro w/ a subbie 2.5 and stock gears but larger 3rd and 4rth tranny gears. I run about 5500#.


The clearance is nice but if I did it again, the gearing just isn't right. To make my combo correct, it needs lower diff gearing, even with the subbie 2.5. 1rst and 2nd are amazing, 3 and 4 not so much. Granny isn't low/slow enough to be awesome, but it's handy for goofing off.
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PostPosted: Fri Mar 20, 2015 2:54 am    Post subject: Reply with quote

I have 225x75x16 Cooper Discovery AT3 LT tires on a hightop conversion (5300lbs). No lift, trimmed trailing arm seams, stock R&P but increased 3rd and 4th. CLK wheels (not sure of the weight but light) and 2.2 Subaru. It drives fine, I like the lift and I think larger tires roll over obstacles better and give better grip.

But, I have concluded recently (after buying the tires unfortunately!) from my experience and from what I have read here that it is too big (I think the Coopers are close to 29.2"). I have had transmission problems (2 in about 50K miles), which may or may not be related (both times directly after long distance with heavy load in hot conditions) . Acceleration is a bit poorer and I have to shift down more for hills (I don't think the Suby 2.2 needs larger gearing on 3rd and 4th) and I don't like the thought that granny gear is faster although it has not given me any problems yet. This is compared to my 195x75x15 winter tires. It's the possibility that it is stressing my transmission that bothers me the most.

If doing again I would go with 215's (and maybe 15" wheels) and maybe some lift. The AT3's are great but they don't come in a smaller size.
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insyncro
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PostPosted: Fri Mar 20, 2015 4:52 am    Post subject: Reply with quote

4.86 R&P are the strongest and that is why I use them.
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Surfy Murphy
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PostPosted: Fri Mar 20, 2015 5:16 pm    Post subject: Reply with quote

This is super helpful, and exactly what I was hoping to hear. I'm guess I'll run my stock 4.86 transaxle with the new ej25 until I get my rebuilt transmission back and keep the 225/70 R16s I have on there for now. Sounds like 225/75 R16 sounds like a good safe outer limit tire size with trailing arms for when I get the new transmission back.

Does anyone who's run 225/75 R16s have any opinion about 5.43 vs 5.83 ring and pinion? They look like they're right on either side of stock. Durability issues? 3rd and 4th gearing? Ideal RPMs for the ej25? There seem to be some differing opinions about 4th gear.

Thanks guys for weighing in.
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Jon_slider
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PostPosted: Fri Mar 20, 2015 6:57 pm    Post subject: Reply with quote

Surfy Murphy wrote:
Sounds like 225/75 R16 sounds like a good safe outer limit tire size with trailing arms for when I get the new transmission back.

not with a 4.86, the previous 2 posters told you they regret the 225, and one also regrets changing 3rd and 4th..

read the posts these two quotes come from, carefully:

kbeefy wrote:
I have 225/75r16 ... the gearing just isn't right. ... it needs lower diff gearing, even with the subbie 2.5. 1rst and 2nd are amazing, 3 and 4 not so much. Granny isn't low/slow enough to be awesome...


shepherdsond wrote:
I have 225x75x16... If doing again I would go with 215's


Does anyone who's run 225/75 R16s have any opinion about 5.43 vs 5.83 ring and pinion?

the 225 tire is 16% tall, and the 215 tire you have is 10% tall. So if you put a 5.43 in, both front and rear of course, with the 225 you will be 4% tall, which is 6% shorter than where you are now..

you do not need to go shorter than the 5.43, and the 5.83 may be harder to find, not sure lately..

but you really need to avoid creating a situation that makes you change BOTH front and rear ring and pinions, unless you just have stupid money to throw around


They look like they're right on either side of stock. Durability issues? 3rd and 4th gearing?

no do not change 3rd and 4th, that creates wider shift gaps

Ideal RPMs for the ej25?

stock van gearing is 71mph @ 4000 rpm. with your 10% taller 215 tire, you are shaving 10% of the rpm to still go 71mph. Meaning you are at 71mph @3600rpm.

you do not need to lower rpm, that just lugs the motor, REDUCES gas mileage, and increases heat.. focus on getting your gearing no taller than 10% past stock.


There seem to be some differing opinions about 4th gear.

only in your mind Smile
Im absolutely, definitely Against taller 4th, and BOTH of the previous posters with 225 that I quoted you are NOT recommending taller 4th.. I suspect you THINK taller gearing makes better gas mileage.. it does not!


Thanks guys for weighing in.


I hope you share your experience after you make whatever changes you decide on.

if you want to learn a bit more about tires, gearing, and handling, read my signature links, and PM me any questions.

Have a Great Weekend too!

oh, and, post a pic or two of your van.. pics are really fun Smile

heres one of WildBill for your entertainment:
Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Sat Mar 21, 2015 1:46 am    Post subject: Reply with quote

I run 235 70 16s on my syncro, but here in Oz our diff ratios were all 5.43. Standard gears were ok but when I rebuilt the gearbox I put a shorter 3rd & 4th in. Can't remember 3rd, maybe 1.35? but 4th is 0.93.I would like a lower G gear but overall this is a great combo and makes for enjoyable driving without the huge gap between gears 3 & 4. Ed
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PostPosted: Sat Mar 21, 2015 4:37 am    Post subject: Reply with quote

I run 245/75R 16 BF All terrain on 7x16 et23 on my syncro. I also have 5,43 final drive and an AAZ 1,9 TD.

It makes for some extra shifting between 4th and 3rd when going uphill, and a slightly high G-gear off road.

I often think that the 5,83 would have been better for my kind of driving.
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PostPosted: Sat Mar 21, 2015 6:43 am    Post subject: Reply with quote

Surfy Murphy wrote:


Does anyone who's run 225/75 R16s have any opinion about 5.43 vs 5.83 ring and pinion? They look like they're right on either side of stock. Durability issues? 3rd and 4th gearing? Ideal RPMs for the ej25? There seem to be some differing opinions about 4th gear.

Thanks guys for weighing in.


I run 235/65R17s which are almost identical in diameter to the 225/75R16. I run 5:43 R&Ps with stock gearsets and I think it's great. I have a bone stock 2.1 and have traveled all over, did Fins N Things in Moab, Fortune Creek Trail and Hawkins Mountain Mines Trail in the Cascades, including "Crankshaft Hill". This tire size and gear combo handled that and many other things really, really well and it drives great around town and on the highway too. Yes, there are compromises when going with larger tires, but when done correctly, there are benefits too.

I really like my combination and would definitely do it again.
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PostPosted: Sat Mar 21, 2015 8:47 am    Post subject: Reply with quote

OddN wrote:
245/75R 16... 5,43 ... AAZ 1,9 TD.

... I often think that the 5,83 would have been better for my kind of driving.


I agree. I use the same 245 tire and 5.43 ring and pinion in my diesel. Im tempted to go down to 225x75x16 (easier than swapping ring and pinions, and less load on the tranny... shorter ring and pinions just mask all the extra load of big tires.. but the load and heat it generates in the tranny is still there..)

Christopher Schimke wrote:
... almost identical in diameter to the 225/75R16. I run 5:43 R&Ps with stock gearsets and I think it's great. ...
I really like my combination and would definitely do it again.


Yay, another vote for 5.43 with 225x75x16 with a Gasoline motor.

clearly nobody who has posted in this thread so far, with experience, is advocating using a 225x75x16 with a 4.86 and a gas motor.

For that matter, nobody with a diesel has posted that they Love a 4.86 with a 225x75x16 either. (stay tuned, someone will tailgate and argue about that in a minute, but the OP has a Gas motor anyway, so its just academic)
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PostPosted: Sun Mar 22, 2015 4:21 am    Post subject: Reply with quote

It was recommended to me when I was rebuilding my syncro transaxle to add the bigger 3 and 4 for strength.

This could go many ways, I usually find lower gears and overdrives are weakest. 1:1 is usually the strongest. I'm not familiar enough with VW to say how it works.

My biggest regret, after having Daryl rebuild the tranny (w/larger 3/4) and installing a late 2.5 is the gears. 2-3 is a huge jump. Now I'm considering dropping R&P, still a big 2-3 jump.
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PostPosted: Sun Mar 22, 2015 12:22 pm    Post subject: Reply with quote

kbeefy wrote:
It was recommended to me when I was rebuilding my syncro transaxle to add the bigger 3 and 4 for strength.


I think you can get the bigger gears in stock ratios.

RonC
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PostPosted: Sun Mar 22, 2015 2:20 pm    Post subject: Reply with quote

For my tintop Syncro conversion build, I attempted to find what I hoped to be a happy medium of good highway performance and decent offroad ratios. The transaxle I bought was an AHF 5.43 unit with a factory 0.78 4th gear. I opted for 30X9.5X15 tires (very close in diameter to 225/75/16), which have only minor rubbing issues after suspension lift. After hours of plugging numbers into Derek Drew's Excel spreadsheet (thanks, Derek!), I decided on a 1.14 3rd gear and a 5.83 R&P. This is a few percent shorter than stock in the lower gears, and a few percent taller in 3rd and 4th. I am currently running a tired stock WBX, which will soon be replaced by a RJE 2.3. The results? Nice granny gear, not quite a crawler, but pretty good. No noticeable big gap between 2nd and 3rd. My only beef is a total lack of power in 4th (at 70mph, I'm at 3800 rpm). Hopefully, the new powerplant will help. I have plumbed the tranny for an oil cooler, but this vehicle probably will never have a high HP motor, so I'm not planning on installing one.
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PostPosted: Sun Mar 22, 2015 2:52 pm    Post subject: Reply with quote

example 1 (Reventlos)
this combination 30x9.5x15, 5.83 R&P, 1.14 3rd, .78 4th with a gasoline motor produces the following gearing percentage change from stock

Granny, 1st, and 2nd are -3% (shorter than stock)
3rd is +4% (taller than stock, with a 7% wider than stock shift gap from 2nd to 3rd)
4th is +6% (taller than stock with a 2% wider than stock shift gap from 3rd to 4th)

===
example 2 (kbeefy)
this combination 225x75x16, 4.86 R&P, 1.14 3rd, .78 4th with a gasoline motor produces the following gearing percentage change from stock

Granny, 1st, and 2nd are +15% (Taller than stock)
3rd is +24% (taller than stock, with a 8% wider than stock shift gap from 2nd to 3rd)
4th is +26% (taller than stock, with a 2% wider than stock shift gap from 3rd to 4th)

===
example 3 (Christopher)
this combination 235x65x17, 5.43 R&P, stock 3rd, stock 4th with a gasoline motor produces the following gearing percentage change from stock

Granny, 1st, and 2nd are +3% (taller than stock)
3rd is +3% (taller than stock, with a stock shift gap from 2nd to 3rd)
4th is +3% (taller than stock, with a stock shift gap from 3rd to 4th)

===

In examples 1 and 2, people have chosen to modify 3rd and 4th. I think that is a mistake. In the second example, the tire is 1% smaller, and the ring and pinion is 17% TALLER than example 1

Example 3 is 3% tall in all gears. Christopher unlike Reventlos and Kbeefy, does not feel his 4th is too tall..

Moral of the story, do not change 3rd and 4th gear with a gasoline powered motor
do change ring and pinion when using 29"+ tires (225x75x16 is 29.3", 30x9.5x15 is 29.5", 235x65x17 (29.2")

All calculations done using the fantastic Derek Drew tireandgearingcalculator, to which I added a custom field to convert gearing changes to Percent difference from Stock, for ease of comparing all combinations of tires, R&Ps and gearing.

========


a couple of My Diesel tire and gearing calculations, for reference. I say "My" because these comparisons are at My "stock" baseline reference gearing of [email protected] 3000rpm, which is something I came up with as a rule of thumb, based on the 4000rpm speed of 71mph for a stock Gasoline powered Tranny.

===
I currently have:
245x75x16, 5.43 R&P, 1.08 3rd, 0.70 4th with a Tdi Diesel motor, produces the following gearing percentage change from My stock references for Diesel

Granny, 1st, and 2nd are -19% (shorter than stock)
3rd is -8% (shorter than stock, with an 11% wider than stock shift gap from 2nd to 3rd)
4th is -2% (shorter than stock with a 6% wider than stock shift gap from 3rd to 4th)

because the above configuration is too tall in 4th, if I did it again I would go to a .73 4th, which would be -6% (short) and the gap to 3rd would be only 2%..

====

If I don't change gearing and only drop to a smaller tire in order to produce better 4th gear acceleration, here is the result
this combination 225x75x16, 5.43 R&P, 1.08 3rd, 0.70 4th with a Tdi Diesel

Granny, 1st, and 2nd are -23% (shorter than stock)
3rd is -12% (shorter than stock, with an 11% wider than stock shift gap from 2nd to 3rd)
4th is -6% (shorter than stock with a 6% wider than stock shift gap from 3rd to 4th)

as you can see, dropping to a 225 makes 4th gear equivalent to changing the .7 to a .73, without opening the transmission Smile However, it makes 2nd shorter than I would like,

===
so here is my "ideal" Tdi Tranny with 29.3"

225x75x16 tires, 5.43 R&P, 1.88 2nd 1.08 3rd, 0.70 4th with a Tdi Diesel

Granny, and 1st, are -23% (shorter than stock)
2nd is -15% (shorter than stock, with an 8% wider than stock shift gap from 1st to 2nd)
3rd is -12% (shorter than stock, with a 3% wider than stock shift gap from 2nd to 3rd)
4th is -6% (shorter than stock with a 6% wider than stock shift gap from 3rd to 4th)

===
next an example of Tdi gearing with 29.5" tires and a 4.86 ring and pinion

30x9.5x15, 4.86 R&P, 1.14 3rd, 0.77 4th with a Tdi Diesel

Granny, 1st and 2nd, are -13% (shorter than stock)
3rd is -7% (shorter than stock, with a 5% wider than stock shift gap from 2nd to 3rd)
4th is -4% (shorter than stock with a 3% wider than stock shift gap from 3rd to 4th)

notice the very small shift gaps and the relatively tall granny, 1st and 2nd. A good setup for a Van that primarily drives pavement, not as much of a super slow offroad crawler as some of the other examples above.

===
and lastly My favorite Driving feeling gearing with a 4.86 Ring and Pinion for a Tdi

215x75x15 (or 215x70x16), 4.86 R&P, 1.08 3rd, 0.70 4th with a Tdi Diesel

Granny, 1st and 2nd, are -18% (shorter than stock)
2nd is -10% (shorter than stock, with an 8% wider than stock shift gap from 1st to 2nd)
3rd is -7% (shorter than stock, with a 3% wider than stock shift gap from 2nd to 3rd)
4th is -0% (shorter than stock with a 7% wider than stock shift gap from 3rd to 4th)

notes on this configuration, because the 215x75x15 tire weighs 11 pounds less than the 245x75x16, it can handle a taller 4th than the larger tire. This 28" tire with 4.86 combination has everything right, granny is nice and slow, 2nd is tall enough in town to go 25mph, the shift gap to 3rd is smaller than from a stock 2nd, and 4th gear has excellent power and acceleration. The only reason to go past a 28" tire, is for added ground clearance, but imo that Requires a shorter than stock ring and pinion.

===

notes on motor power and tire size
It is a common myth that when you get a stronger motor, you should also get taller gearing. I completely disagree with that philosophy. Taller gearing creates wider shift gaps, and imo gasoline motors do NOT need wider gear spacing. Only with diesel, do I advocate changing gears and spreading them wider, in order to raise the highway cruising speed, at the cost of wider shift gaps.

here are some common tire and gearing percentages

a 28" tire is 10% tall
a 29.3" tire is 16% tall
a 5.43 ring and pinion shortens gearing by 12%
a .77 4th is 8% tall
a 1.14 3rd is 7% tall
a 1.88 2nd is 5% tall
a 1.08 3rd is 12% tall (which is why a 1.88 2nd is a good idea with this 3rd)
a .7 4th is 18% tall (which is why it is paired with a 1.08 3rd to reduce the gap)

rule of thumb, double digit tall is to be avoided
double digit wider percentage gear spacing is to be avoided

common combinations
~28" tire 4.86 ring and pinion, use STOCK gears for gasoline motor, use 1.88 2nd, 1.08 3rd, .7 4th for diesel. Personally this is the largest tire I recommend for 4.86 ring and pinion for both gas and diesel motors.

~29.x" tire 4.86 R&P, NOT recommended for gasoline motor, but if you are there, definitely keep STOCK gears. For diesel use 1.14 3rd and .77 4th. Personally I recommend 5.43 with 29" tires, for both gas and diesel motors in a Syncro that is used offroad to crawl slowly.
_________________
My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco


Last edited by Jon_slider on Sun Mar 22, 2015 6:29 pm; edited 2 times in total
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