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macjack
Samba Member
Joined: February 26, 2004
Posts: 357
Location: Colorado
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 Posted: Sat May 19, 2018 1:37 pm Post subject: Syncro tire size differences: how much is too much? |
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So I have a formerly matched set of 4 Bridgestone AT KO's on my syncro.
After running with a suspension issue, I have one tire that is more worn.
Currently, I have tread depths of 5/16, 8/16, 8/16, and 9/16th.
Is this too much difference for the differentials, transmission, and VC?
Thanks in advance!
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81 Westy (sold)
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Sodo
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Joined: July 06, 2007
Posts: 9618
Location: Western WA
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| Posted: Sat May 19, 2018 2:31 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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Thats all well within the range.
But let’s not pass up an opportunity to get anal and discuss some drivetrain characteristics.  The ONLY item of concern here, is preservation of your VC. Or politeness to your VC, right?
If you put the 5&9 on one axle, the differential between that pair of left & right wheels will average to 7/16 without a care in the world. At 60mph, for example, your differential will be spinning (differentiating) about 1 full revolution every 8 seconds. Not really whizzing along the path to wear itself out (soon).
With the 5&9 on one axle you have the equivalent of 7/16 on one axle & 8/16 on the other which is “almost perfect” to your VC.
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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
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Jon_slider
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Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Sat May 19, 2018 2:56 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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| macjack wrote: |
| I have tread depths of 5/16, 8/16, 8/16, and 9/16th. |
iow, 10/32 for the smallest, and 18/32nds for the largest, a difference of 8/32nds
and typo alerts, Bridgestone is not the brand of the T/A KO (and another typo T/A KO not AT KO)
the "safe" limit is 2.5/32nds, your tire is way past that.
You could remove the propeller shaft, so the VC is not being overheated, but it might be too late.
you might want to diagnose if your VC is aggressive, that could have been caused by the tire mismatch. Driving on pavement with an aggressive VC, puts added load on the transaxle ring and pinion.
When parking, does your syncro resist rolling, and wants to stop, unless you give more gas, when you turn the steering past 90 degrees?
You might also want to check the magnet on your transaxle drain plug for metal shavings.. and maybe change the fluid too. Has it been more than 30,000 miles since the last drain and fill?
https://www.thesamba.com/vw/forum/viewtopic.php?p=6949341&highlight=2mm#6949341
| OddN wrote: |
| In the Owners Manual, both in the German, and the Norwegian version it is states that a thread Depth difference of more than 2mm should be avoided due to tension and stress in the driveline. |
fwiw, if I did the math right, 2mm = 2.5/32nds
also, are you inflating your tires correctly, by following the 20% pressure differences for front and rear, as printed on your doojamb?
If you have any doubts about any of the above, and you want to keep driving the van, remove the driveshaft until you figure it out. (Or decouple when you are on dry pavement, if you have a Decoupler)
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macjack
Samba Member
Joined: February 26, 2004
Posts: 357
Location: Colorado
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| Posted: Sat May 19, 2018 4:16 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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Yesh, quick mindless typing on my part, mid frustration installing some Reimo hinges for my Zbed. But that's another story.
Back to the tire question, Yes, BF Goodrich A/T KO, is right. And I actually mean to write 5/32-9/32s, not sixteenths. So less different, but still a 4.5 /32nd difference.
The manual seems to put that beyond spec.
Is that a widely adopted spec, from the German and Norwegian manuals?
Probably due to drain and fill the diff and transmission soon, it's at around 20k now on the last service.
Last winter I was running a set of snow tires, so not putting a lot of miles on these tires now.
And Jon, I have appreciated your posts on tire inflation difference front to back. I follow that and am grateful to you for the knowledge.
I finally figured out how to get the hinges installed with the little springs on the right path in the hinges. Now I have a flat bed with my ALH conversion raised lid rear cushion (without using an extra cushion, as I have for the last ten years).
I'm open to purchasing a new set of tires, and had asked about them at the tires shop and they measured and inspected each tire and said that the tread depth differences and general treads were fine. Given that they are in the business of selling me tires, I was temporarily relieved to consider it fine, but that of course is not always the final word.
The VC on the van currently is about perfect for me. Not binding on pavement and in tight turns in a parking lot, but great in snow. Ring and pinion/transaxle issues are generally to be prevented, as best as one can. Agreed! I'm at about 80k miles into this transaxle, which went in 12 years ago with the engine conversion as a freshly rebuilt unit from German Transaxle. 50k ago, I had a shop do a light rebuild for help getting into reverse, but other than that I keep it drenched in Royal Purple, and go mild on the accelerator when the wheels are tightly turned. Plus, the tall sidewalls at ~7 inches, might even add a squish factor that takes some stress of the system? Who knows?
And I liked picturing the internals being out of rotation once every 5 seconds, Sodo. I am trying to figure out the best arrangement of the tires, should I keep them on without buying new ones. They had just installed them with the 5 and 8 up front and another 8 and 9 on the back, claiming that you want your best tires in the rear. I was feeling that I wanted to rotate the biggest ones to the front to wear faster and "catch up" to the smaller ones in the rear.
But really, I'm tempted to just get a set of Cooper Discoverer AT3s on there, to make it a little quieter than with the BFGs.
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81 Westy (sold)
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vanagonjr
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Joined: October 07, 2010
Posts: 3431
Location: Dartmouth, Mass.
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| Posted: Sat May 19, 2018 4:56 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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| Jon_slider wrote: |
| OddN wrote: |
| In the Owners Manual, both in the German, and the Norwegian version it is states that a thread Depth difference of more than 2mm should be avoided due to tension and stress in the driveline. |
fwiw, if I did the math right, 2mm = 2.5/32nds
also, are you inflating your tires correctly, by following the 20% pressure differences for front and rear, as printed on your doojamb?
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Hard to believe that 2mm would cause a problem on that size tire. The Porsche 996 Carrera-4 (has a VC) stock tire sizes have more difference than that; 6mm between the front and back as specified new.
Specification -Sidewall -Radius-Diameter-Circumference-Revs/km-ifference
225/40-18---90mm---319mm---637mm---2002mm---500-- 0.0%
265/35-18---93mm---321mm---643mm---2019mm---495-- 0.9%
Over time they will balance in diameter, as the rears will wear more than the fronts, especially with nearly 300hp and a 7,000+ rpm redline - fun!
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Jon_slider
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Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Sat May 19, 2018 6:17 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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| macjack wrote: |
| I'm at about 80k miles into this transaxle |
congrats!
I dont envy your decision on what to do with the tires you have. I would be OK using them, decoupled, but they are clearly out of spec to run coupled.
| vanagonjr wrote: |
Hard to believe that 2mm would cause a problem on that size tire. The Porsche... |
believe it or not, Porsche has different rules, so does Audi
(see the link I gave above for more info, here is the cliff notes)
Here are recommendations from some of the manufactures that Tire Rack currently serves for matching the tires used on their four-wheel drive and all-wheel drive vehicles. Additional recommendations from other Original Equipment Vehicle Manufacturers is pending.
Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.
[IF OP had and Audi, he would be just within the limit]
Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.
[5/32 is 55% of 9/32, so OP's tires would violate that rule if he put them on same Porsche axle]
Nissan GT-R when replacing less than four (4) tires, each tire continuing in service must have at least 6/32 inch (5 mm) of remaining tread depth.
[IF OP replaces the 5/32nd tire it would be OK on a Nissan, but IF new tires have 12/32nd tread then it would be 4/32nd more than the two 8/32nd tires, so buying just one tire is not a good option. Besides, a Syncro is not a Nissan ]
Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth.
[OPs tire violates that rule]
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Sodo
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Joined: July 06, 2007
Posts: 9618
Location: Western WA
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| Posted: Sat May 19, 2018 9:14 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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| macjack wrote: |
| I'm at about 80k miles into this transaxle |
{edited May20, emphasis  added WRT our vehicles transitioning into the realm of antiquity, NLA gearbox parts, no good used parts available, new parts not up to OEM quality, a prod to get under the van and LEARN, and stuff.... Like learning about tread depth}
It's time to "know" how much metal is on the magnetic drainplug, and LEARN what your interval should be. Going by the odometer is NOT a great way with an old trans (it seems like transaxle maintenance is something Macjack CAN do ). For many Vanagon owners, checking the magnet is not possible; consequently oil change by odometer (or calendar interval) is ALL they can do. And for some, it's "NO transaxle maintenance" at all. And they will PAY. And WHERE are they going to find a quality rebuilder (and the $$). Quality rebuilders are not waiting at every street corner with floor-jack in hand ready to drop it out. Trans rebuild is a big deal and you need a VW specialist. It's far better to maintain the trans you HAVE.
At 20,000 miles.... your valuable syncro trans could have soiled it's lubricant 5 or 10,000 miles ago. You can't know your lubricant's condition unless you look at the magnetic drainplug. It could be grinding itself up inside. It would be a shame to find a christmas tree on your magnet and think "dang I wish I changed it 10,000 miles ago". And on the other hand, if your magnet still has clean spots, then you KNOW 20,000 is OK, you KNOW your trans is healthy, and summer will be GOOD for Vanagon travels.
If your magnet is clean at 20K, that suggests (knowledge based) that you can increase it to 30K, but there's only one way to know that (you must look at 20K!). And be aware that the oil change interval will be getting less as the trans gets older, so 80K is a little late to be hoping for longer intervals. But a clean magnet would be wonderful, right? I think this was likely, from "VW NEW" and with 90HP, but not so likely after "rebuilt & more power." Note that 'rebuilt' is just new bearings and synchros, using your old gears, old R&P. Just sayin, if you are ABLE to maintain your transaxle, it will run longer. And at next rebuild, if your shafts are still good, that's a couple thousand bucks saved right there.
Using Royal Purple does NOT preclude gearbox maintenance. Specialty oil is often detrimental to your gearbox because the guy thinks he can run it longer. That's like buying the best quality tires under the notion that better tires tolerate non-maintenance (don't have to maintain tire pressure, or monitor tread depth etc). No mechanical system works like that especially ball bearings and roller bearings in a closed lubricant system. Bearing condition is crucial to gearbox life. After your bearings get 'loose,' all your gears start to scrub together instead of 'roll', and they wear faster and generate heat too. For long life, roller bearings need clean lubricant, period, and you have to monitor it, to KNOW. PLUS the hard steel abrasives produced are a further detriment. ALL R&Ps are hypoid which is not just rolling contact like your gears, it has sliding contact, so abrasives are rough on your R&P; especially with more HP. You have to get the abrasives OUT.
If you don't want to look at the oil, and learn how to evaluate it etc, make decisions, then just change it sooner. If your oil is too expensive to "change sooner" then you have made a mistake. If you prefer to run expensive oil, you should learn to monitor its condition too; or you've wasted your money and could be doing your trans WORSE.
That's for long transaxle life. If getting under the van reduces your enjoyment of Van-life, well there's that.....  But if you CAN maintain your transaxle...... it's like low-hanging fruit. Why not do it?
| Jon_slider wrote: |
....Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth. [/i]
[IF OP had and Audi, he would be just within the limit] |
OP's Syncro has open diffs front and rear; thus can put the 5/32 and 9/32 averaging to 7/32 on one axle. With both 8/32 tires on the other axle the van is within 1/32. Well within the Audi comparison. Keep in mind that using ONLY tread depth is a "simplification." An understandable simplification for the general vehicle owner. Macjack asked on a forum, of members who understand the Syncro drivetrain, how to arrange the various tires to mitigate the diameter differences. We can go a little 'deeper' than simple rules.
| Jon_slider wrote: |
Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.
[5/32 is 55% of 9/32, so OP's tires would violate that rule if he put them on same Porsche axle]
....
Nissan GT-R when replacing less than four (4) tires, each tire continuing in service must have at least 6/32 inch (5 mm) of remaining tread depth.
....
Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth.
[OPs tire violates that rule] |
While these mfr rules are interesting in comparison, note that Cayenne, Nissan and Subarus have ABS and traction control systems that likely require tighter tolerances on tread depth.
Syncro has no ABS or traction control systems. It's drivetrain ONLY, and it pretty much comes down to protecting the VC. Our OP, wielding a tread-depth measuring tool and TheSamba has the necessary information to determine that he CAN run those tires, relegating the question whether to purchase new tires into an emotional decision. Can't help ya there. I'm in EXACTLY the same boat. I want the new style BFGs but quieter running is VERY appealing too.
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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
Last edited by Sodo on Sun May 20, 2018 8:44 am; edited 2 times in total |
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OddN
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| Posted: Sun May 20, 2018 2:43 am Post subject: Re: Syncro tire size differences: how much is too much? |
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| Sodo wrote: |
| OP's Syncro has open diffs front and rear; thus can put the 5/32 and 9/32 averaging to 7/32 on one axle. With both 8/32 tires on the other axle the van is within 1/32. Well within the Audi comparison. |
This is what I would do.
And since the front wheels travel slightly longer distances when you turn, I would put the two 8/32's in the front and the 5+9/32's in the rear to minimize the loading on the visco.
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Wildthings
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| Posted: Sun May 20, 2018 5:51 am Post subject: Re: Syncro tire size differences: how much is too much? |
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| OddN wrote: |
| Sodo wrote: |
| OP's Syncro has open diffs front and rear; thus can put the 5/32 and 9/32 averaging to 7/32 on one axle. With both 8/32 tires on the other axle the van is within 1/32. Well within the Audi comparison. |
This is what I would do.
And since the front wheels travel slightly longer distances when you turn, I would put the two 8/32's in the front and the 5+9/32's in the rear to minimize the loading on the visco. |
With the tires installed this way, make a 20+ mile hwy run and see how hot your VC is running.
Last edited by Wildthings on Sun May 20, 2018 9:48 am; edited 1 time in total |
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macjack
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Posts: 357
Location: Colorado
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| Posted: Sun May 20, 2018 8:00 am Post subject: Re: Syncro tire size differences: how much is too much? |
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So I don't hear anyone worried about the open differentials in the front or rear. That amount of difference left to right is not a concern? I guess open means open, as opposed to an LSD?
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81 Westy (sold)
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IdahoDoug
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| Posted: Sun May 20, 2018 9:12 am Post subject: Re: Syncro tire size differences: how much is too much? |
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No worries about the L/R split - provided they oil is good.
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Sodo
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Location: Western WA
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| Posted: Sun May 20, 2018 9:31 am Post subject: Re: Syncro tire size differences: how much is too much? |
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| macjack wrote: |
| So I don't hear anyone worried about the open differentials in the front or rear. That amount of difference left to right is not a concern? I guess open means open, as opposed to an LSD? |
With 5/32+9/32 on one axle, at 60mph your differential side gears make one lazy turn every 16 seconds. Count "one,onethousand, two,onethousand up to.....sixteen,onethousand). You get the idea (long before 16)....one lazy turn of the diff side gears isnot a concern at all. As Doug suggests, good oil is good for all kinds of stuff. Better to focus on your gearbox mainshaft bearing that has turned 900 times in this 16 second interval... and is it whizzing along in clean lubricant?
Correct on open vs LSD.
Just for the sake of theSamba discussion....."LSDs" for syncros are so rare... that it's highly unlikely that you have one, but it's not a good practice to use different size tires with a (friction disc) LSD. If you had an LSD on the rear, you would put the two equal 8/32s on the rear. A Peloquin; which is under the general classification of "LSD" is not an LSD nor a TBD, but it's "like a TBD". A Peloquin requires 'funny business' to lock up ("like a WTF") But in any case one turn every 16 seconds makes no difference to a Peloquin, however the prudent owner would put the two 8/32s on the rear for a Peloquin too.
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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 |
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Jon_slider
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Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Sun May 20, 2018 11:55 am Post subject: Re: Syncro tire size differences: how much is too much? |
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| Sodo wrote: |
| With 5/32+9/32 on one axle |
can you offer an educational link to where VW says you can run two tires on the same axle that are 4/32 different?
I cant find that strategy mentioned anywhere
I find stuff like this
https://www.souzastireservice.com/tires-101/tire-matching-awd-4wd.aspx
note the Subaru 2/32nd limit is the same as for a Syncro. No mention of LSD. Most subarus do not have LSD, Syncros dont come with LSD either, but both use a VC, and both have warnings not to exceed 2/32nd tread depth difference.
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Wildthings
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| Posted: Sun May 20, 2018 1:18 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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.
Everyone has their own rules on what works as far as matching tire sizes.
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Sodo
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Posts: 9618
Location: Western WA
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| Posted: Sun May 20, 2018 3:19 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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| Jon_slider wrote: |
| Sodo wrote: |
| With 5/32+9/32 on one axle |
can you offer an educational link to where VW says you can run two tires on the same axle that are 4/32 different?
I cant find that strategy mentioned anywhere. |
I don’t think you will find it published. Its not really for public consumption. Its for the one guy who has provided all tread-depth measurements, wants to run his set a little longer, and inquired on a forum containing members who “know” the specific drivetrain well.
That Souzas tire article was very good! Syncro owners should read that for general background , but read it knowing Souza did not address anything similar to a Syncro drivetrain.
This was the last paragraph by Mr/Ms Souza:
It is very possible that a mechanic who specializes in a specific vehicle would know the answer. However, the problem here is that people (especially males!) will often give you an answer without actually knowing, so caution is advised.
Both of these closing statements apply here. If anyone reading this stuff doesn’t understand WHY its true, it is BETTER to err on the side of caution, and buy 4 new tires, than trust internet advice you can’t vet reliably. If you don’t understand why its true you might “apply” the knowledge wrongly, in a manner unforeseen by your Samba brothers/sisters; causing some sort of deviltry. So just buying the 4 new tires is a wsy around that. But Macjack, you can run those tires out this summer, buy new tires before the snow. Probably would help if some others who know the Syncro drivetrain well would chime in.
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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 |
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Wildthings
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| Posted: Sun May 20, 2018 4:08 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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I find it odd that the article says to measure your tires with the air out of them. To me this is making a wild assumption that all tires will expand the same amount when aired up. This may work fine when you are comparing 4 tires of the same brand and age, but I am not sure it would apply well when comparing tires of different brands, different tire designs within a brand, or tires of the same brand but with different mileage on them, i.e. a brand new tire may expand differently the first time it is aired up than an identical tire with 10,000 miles on it. |
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Sodo
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| Posted: Sun May 20, 2018 4:34 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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| Wildthings wrote: |
| This may work fine when you are comparing 4 tires of the same brand and age, but I am not sure it would apply well when comparing tires of different brands, different tire designs within a brand, or tires of the same brand but with different mileage on them, i.e. a brand new tire may expand differently the first time it is aired up than an identical tire with 10,000 miles on it. |
I’d wonder too about polyester belted tire WRT wildthings concerns. But steel is real. Steel “ages well”; probably no difference between old & new. Unless the tire was run flat and not visibly damaged.
Pretty easy to test this you only have to measure a tire new, not drive it, measure again 20 years later. Just gotta find some old duffer with an antique car he never drives, then wait.....this thread may go dark....
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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 |
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Wildthings
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| Posted: Sun May 20, 2018 4:42 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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| Sodo wrote: |
| Wildthings wrote: |
| This may work fine when you are comparing 4 tires of the same brand and age, but I am not sure it would apply well when comparing tires of different brands, different tire designs within a brand, or tires of the same brand but with different mileage on them, i.e. a brand new tire may expand differently the first time it is aired up than an identical tire with 10,000 miles on it. |
I’d wonder too about polyester belted tire WRT wildthings concerns. But steel is real. Steel “ages well”; probably no difference between old & new. Unless the tire was run flat and not visibly damaged.
Pretty easy to test this you only have to measure a tire new, not drive it, measure again 20 years later. Just gotta find some old duffer with an antique car he never drives, then wait.....this thread may go dark.... |
It would be easy enough to check if someone bought a new set of tires. Measure the tires aired up with zero miles on them and then again with say 2000 miles on them and see if the diameter has changed. |
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Sodo
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| Posted: Sun May 20, 2018 6:26 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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You envision a slight increase upon break-in? That would be interesting (to me). I just gotta remember to do it at tire-time. Which I’m in exactly same boat as Macjack, BFGs with just one summer remaining and a woodie for new tires. Remembering to jump past the “employees only, no exceptions” sign, elbow the tire guy away and measure tires would be my biggest problem. Maybe someone else can do it first?
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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 |
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jimf909 
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| Posted: Sun May 20, 2018 8:32 pm Post subject: Re: Syncro tire size differences: how much is too much? |
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Is the idea here that a 215/60 might break-in to be a 215/60.1 and a different tire would become a 215/60.2 at the same pressures?
I think production tolerances have improved to avoid this but who knows. Only multiple measurements would tell.
Maybe I’ll worry about this when I convert my 1WD to a Peloquin LSD with TBD (thanks for the ongoing continuing ed, Sodo  ).
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- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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