Date: Fri, 18 Dec 2009 18:11:08 -0800
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Syncro Tire Diameter
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Another way this particular situation could have been avoided is -
buy 6 tires, brand new and matching, in the first place.
then do a 6 tire rotation pattern.
That way, if you loose one tire, you still have 5 evenly worn matching tires
.
I read that on this list - thought it was a great idea, because
........sometimes you can't get an identical tire a few years later.
3 mm sounds about right to me, fwiw. 7 mm is a 1/4 of an inch ........so
about 1/8th inch diameter tolerance.
They'd have to allow for the slight difference that tire pressures can make.
They specify different front and rear tire pressures after all.
re the question about buying two other very similar tires.
Find out the revelations per mile of the new tires, and compare to the old
tires - there's a spec for any model tire - see tirerack.com
Here's a 'true' way to get actual 'rolling/dynamic' diameter.
Mark off 100 feet on a straight flat stretch of pavement.
Mark a spot on a tire.
see how many revolutions exactly a tire does in that 100 feet, or make it
200 feet, for more accuracy.
That's one way you can 'amplify' what the in-use actual rolling diameter is,
for comparison purposes.
if the specs of the new and old tires are within a percent or two ........or
the measurements I suggest above are very close, you probably can get by
with slightly different tires, but there is some risk. Syncro's can be
rather demanding .........i.e. - they 'like money' sometimes. The ideal of
course is 6 matching brand new excellent syncro-rated tires.
Scott
----- Original Message -----
From: "Bob Stevens" <mtbiker62@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, December 18, 2009 8:24 AM
Subject: Re: Syncro Tire Diameter
> On Fri, Dec 18, 2009 at 7:06 AM, Anthony Egeln
> <regnsuzanne@yahoo.com>wrote:
>
>> The conventional wisdom on syncro tires is that they should be virtually
>> identical in diameter, to prevent spurious activation of the VC. I
>> believe
>> it has been said that the diameters should not vary more than 3/8 of an
>> inch.
>>
>
> The "tech" info says 3mm. Waaaay different than 3/8".
>
>>
>> But consider this: What if the inflation of the 4 tires is not equal,
>> which is often the case? Wouldn't that affect the diameter by easily 1/2
>> to
>> 3/4 of an inch?
>>
>
> Where did you get that "factual/actual" information? Did you measure the
> diameter? Or are you creating a scenario just for discussion purposes?
> Anyone choosing not to do proper maintenance of their Syncro can develop
> improperly inflated tires, but that's all that is. Laziness can cost $1000
> for a VC ... not my choice. Same with improperly aligned front/rear ends
> which destroys tires and begs for VC and $$ problems.
>
>>
>> Here's my dilemma. On my van I have the Bridgestone Dueler AT Revo, in
>> the
>> 225-70R-15. Bridgestone has discontinued this size....though not the
>> Revo
>> model. I have 3 nearly new tires, but one tire (and the spare) are worn
>> a
>> good deal on the outer 1 inch or so. This is from when they were on the
>> front with a marginal alignment, since adjusted. Although the center,
>> and
>> inside, of these two tires is very good, the conventional wisdom says I
>> really need two more tires in exact diameter, and I can't get them in the
>> Revo.
>>
>> Bridgestone recommended a Firestone tire that was similar to the Revo.
>> My
>> question for the list is this. Can I substitute 2 new tires of a similar
>> tread and diameter to the Revos in a 5 wheel tire rotation without
>> cooking
>> my VC? Right now I hate to throw away 3 perfectly good tires...to say
>> nothing of spending $600 + on new replacements.
>>
>
> This is all due to owning a Syncro. Sell the old tires and get new one's,
> or
> be prepared to deal with getting a replacement VC (IF) it gets destroyed.
> Option: get a decoupler and a solid shaft, put them on and sell the VC
> while
> it's good, if it is now.
> You sound to me like you're trying to justify not abiding by what you have
> already called "conventional wisdom". I'd call it facts about owning a
> Syncro.
>
> bob
>
>>
>>
>>
>>
>>
>>
>>
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