Charley B

I replaced timing belt a year and half ago, put about 200 miles on the car and parked it. Am I safe to put another 1200 or so miles on it before checking tension, or does the extended time sitting, change the equation?

VehiGAZ

IMHO, for t-belt tension, I would think that mileage is the far more important factor. Yes, the belt will stretch a little just sitting there, but it's the spinning around and around that will loosen it up.

ROG100

Sitting should not have any short term effect on the belt.
Drive it and then check it when convenient

Stephencs601

Milage is the key. The big problem with letting anything sit for a period of time is dry rot.

Gary Knox

I have some experience which differs from the above opinions.

On 4 occasions I've replaced the timing belt on an S4 or GTS in January. Since I don't drive the cars until spring, they sit in the garage, very occasionally started, but hardly driven. Probably a total of less than 5 hours engine operation after the belt installation (tension set at 5.3 on the Porsche shop tool, 90% of the window closed on the Kempf tool) and the time I start driving.

The first time I did this, out of curiosity, I checked the belt on the car in late April, as I had a track event in mid May. Tension on the belt was 3.2 on the Porsche tool (and as I recall, just outside the window on the Kempf tool).
I re-tensioned it (5.1 on Porsche tool), and a year later with about 6K miles, including 1000 track miles it was 5.0.

From that time on, I've always checked the tensions after about 3 months, or 1,200 miles, whichever comes FIRST. All results have been similar in loss of tension (without driving more than 100 miles) to the first experience.

I must also add that these have all been aftermarket belts, and I think they were Conti's. Maybe Porsche belts, or other brands are different. All my future belts will be Gates, so I'll see what results they provide!

So - it's my opinion that if you ignore time and focus on only the mileage there's a bit of risk.

Gary Knox

GlenL

Whose experience matches mine:

Almost all the stretch happens in the first 5 minutes of driving.

Tension, drive it a bit, re-tension and it's good for the life of the belt. Might extend a bit in the next 50k but not falling out-of-spec enough to worry about.

Wish I had numbers. Kudos, Gary.

Bill Ball

Charley:

I don't have a concrete answer to this. I've not seen a belt stretch so much that it is outside the spec window at 1500 miles or whenever the first check is done. Generally they have only required one or two flats at most to get back to where they were originally (near the top of the window). So, I can't say that this adjustment is all that critical. I did have a Conti belt that would not hold tension at 25,000 miles and stopped using them.

We can check the tension any time you are around. Or you could solve this dispute in a couple of days - DRIVE THE CAR!

VehiGAZ

That's the real point - you will likely still be in spec regardless of how the normal stretch occurs (by time or by use).

borland

The time or miles may depend on how you adjust the belt using the Kempf or Porsche Tool.

If you previously adjust the belt at TDC, not observing whether the cams were at TDC on cylinder #1 or #6, the belt could be too loose. Adjusting the timing belt at TDC#6 will result in a slightly looser belt than if it is correctly set per WSM at TDC#1.

I recently retensioned the Conti belt on my 90' S4, as it required 1-1/2 flats of additional tightening after several years of service. Each incremental tension adjustment requires rotating the crank two full turns before tension re-measurement.

Using the Kempf tool, to see how much looser the TDC#6 was, I stopped at TDC#6 on the way back to TDC#1. I found the Kempf tool consistantly read 1/2 window tighter at TDC#6 than at TDC#1.

RyanPerrella

what kind of belt is it?

If its the gates variety you could hold off till mileage comes up

If its a Conti I dont think it would hurt to check it now

I would think its probably not an issue either way really. I dont recall adjusting the tension on the belts ive installed. Although I only used a Conti once and sold the car immediately after changing the thing and never hit 1500 miles.

Charley B

Thanks guy's. Great points. I'm a lot more comfortable now. Yes, Bill, I'm determined to drive it more often. Too many cars, too little time.

mark kibort

I put mine in with the new stroker engine. Im on my 3rd season. is 3 seasons the limit for race cars? I think I only have about 10,000miles on the car's engine.

Tails

An excellent discussion, however, not to side track this thread, can the tensioning of the belt be extrapolated to the changing of the timeing belt related to age of the belt or miles travelled?

Should be belt be changed at a time period, say 5 years, as a preventative maintenance measure or should the belt be change on mileage as recommended by Porsche in the WSMs etc?

Are these two paramaters, time (age or the belt) or recommended mileage affected by the makers of the belt, Gates, Conti or Porsche supplied belts etc?

What therefore is the recommendation for the racing Gates TB that Roger sells, for time and/or mileage?

Tails 1990 928S4 Auto

VehiGAZ

Hooo-BOY!!! Here we go again!

Yes, a belt will fail from time alone, or from accumulated mileage. How those two functions interact is anyone's guess.

If you have a 5 year old belt with low miles on it, it's probably still good and will look like-new if you choose to replace it.

If you have a 10 year old belt, it would be a good idea to replace it regardless of how it looks or how many miles are on it.

What's in between those marks are up to personal opinion and how much you enjoy a good t-belt change!

IcemanG17

I'd check it......chances are its fine then just drive on!!!!!