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Can a Dyno test ruin your tires?
I called a Detroit Diesel Service Center yesterday to inquire about having a dyno performed on an S-60
( for prebuy purposes) and he went on to say ” It is very risky and likely the drive tires will delaminate due to
the extreme heat they will undergo during the test”
So I asked him what about the big rigs ( tractors)? His answer was since they were open wheel’s, not a problem,
but the buses trap the heat, he wouldn’t recommend doing it on a bus.
Is this Balogna or what? Have you guys done this and please tell me what your experinses and results were.
Thanks,
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7 Replies
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I for one think it is baloney, but with that said, I have not had a dyno done on my bus. The normal run is not that long, so I would be hard pressed to think that would ruin tires. If they are worried, blow a couple of fans on them, that should help to keep the temps down.
What part of the country are you talking about?
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Barney,
Like oil analysis I think a dyno test is warranted when you have a base line for comparison.
I know buying a coach is a concern and having a good engine / transmission is a critical concern but between Tom and I we have bought 8 coaches and running the codes and doing a test drive will probably be all you need to do to verify the health of both.
I look for a coach that is warmed up to pull smoothly and strongly from a stop, no smoke, and if possible pull a long enough grade to insure the temps cycle and do not continue to climb. I look for good oil pressure, smooth shifts, and if retarder or Jake brake equipped to get noticeable brake assist from the engine brake or retarder.
If you have good maintenance records to prove continued scheduled service that is worth far more than any dyno test.
Then when you own the coach, hook up with one of us and let’s do a drag race to see whose engine pulls strongest. (Just kidding)
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I’m with Mark, tires being ruined on the Dyno sounds like a fairy tail.
Check the codes, drive it and then put it up on the lift for inspection.
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This was a shop in Dallas, that popped on the DD site search for service centers.
They quoted $800 for a check up plus $350 for a dyno.
I’m just trying to be prepared to make my first purchase and feel a little naked since I’ve never
even driven one I wouldn’t know what acceleration to expect or whats a normal feeling shift of the transmission.
I appreciate all your comments and suggestions. It helps get me ready for the big day.
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Barney.
Out of the thousands of coaches owned over the years by members of this site I would guess the number that have been on a dyno as a condition of sale you could count on your fingers of the left hand. If I am wrong I suspect there will be replies.
If you have never driven a Prevost coach you are like all of us on our first driving experience.
Let me suggest this for consideration. Arrange for a test drive. Make sure it is of long enough duration for the temps to get to normal, and if possible include a very long steep climb. Not a fraction of a mile, but one that is 5 or six miles long and at least a 5 or 6% grade.
The coach should start without hesitation. It should idle smoothly without smoke. You may see a puff of smoke upon starting but it should clear. Depending on the engine / transmission combination the gauges are going to show normal values. During the drive pay attention to those gauge readings. When you are driving the engine should run smooth. The transmission shifts should be smooth.
When under a prolonged load (such as climbing a grade) the coolant temps should cycle up and down. If they continue to climb you may have a problem.
If the coach you are driving is a Series 60 equipped coach it likely has the 6 speed Allison. That transmission has particularly smooth shifts. Sometimes only the tach is the indication of a gear change. But if the transmission is in performance mode (you will see an indication on the shift pad) shifts will be noticeable and the coach will hang in gear longer and downshift sooner.
Normal readings for a Series 60 are temperatures to cycle from around 204 to 208. The engine computer engages the low speed fan at 204 and the high speed fan at 208. If the fan clutch is locked up (not good) the engine thermostat will cycle around 195.
Oil pressure at highway speeds should be around 40 PSI when the engine is warm. Transmission oil temps should track engine temps except when the retarder (if equipped) is engaged.
Under full throttle acceleration you should be able to peg the turbo boost gauge.
Voltages should be around 27.5 when the engine is running.
Air pressures should peak at 120 to 125 and cycle back on at 100. You should not see them cycle up and down significantly. Before you begin to drive you should (or have the owner) do a DOT brake check. If the owner or seller does not know how be concerned. You should learn how to do one just in case.
If everything checks out and you are still not sure, then arrange for the dyno check.
There are so many other things to inspect a dyno check is low on the priority list. But having the codes checked and doing a full coach (including the house) inspection is far more valuable. That alone is going to take at least a couple of days.
http://prevostcommunity.com/articleDetail.asp?ID=86
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For our 5 county area we must do an emissions test annually by placing our coach on a Dyno. We haven’t had any tire issues. Next time I go to Stewart n Stevevson I will ask if they have ever seen Dyno-induced tire failure
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I suspect one has to reflect on what kind of dyno testing is done. I was at Sturgis a few years back and guys were all farting up their starley’s on the dyno to determine power at the real wheel. Frankly is was bloody, rather should I say oily, articulating rods vacated through cases. California does dyno testing as well for smog, however they simply set the vehicle at various speeds rather than tighten the dyno till she stops or blow’s……….
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