Yes, this can be informative, but at times of limited reliability if the bridge surface is not flat (frequently, I've found), or the actual positive angle is minimal. As per Parker comment, we should be clear if we are using this to look at the rear segment (he mentions the duplex) or the front.
Original Message:
Sent: 01-14-2026 15:06
From: David Love
Subject: negative bearing in brand new 7' piano
Yes, that's a very good quick check to see if the front bearing is positive. It won't give you actual numbers but will at least tell you if the strings are running up hill to the bridge.
------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 01-14-2026 14:54
From: Parker Leigh
Subject: negative bearing in brand new 7' piano
A good test for any piano is to place a 6 " rule across the bridge in the middle of the melody octave. Check to see if the rule is 1/2 mm or more
above the top of the duplex. I first observed Hans Barth, formerly of Juilliard, do this when selecting new Steinway pianos.
------------------------------
Parker Leigh RPT
Winchester VA
(540) 722-3865
Original Message:
Sent: 01-14-2026 10:03
From: David Skolnik
Subject: negative bearing in brand new 7' piano
Peter -
I have nothing but gratitude for a debate that has provided me with such a wealth of reading material, which I need to print out - the latest "notwithstanding" being 3 single-spaced pages. My regret is that I don't have train-commute time, so I'll have to wait to read David L's most recent, but I can manage a quick response to your's here.
I'm not sure you're actually reading what I've written. Again, to quote from Keith's original: "I didn't think it sounded all that great for the price. I checked bearing using a Lowell bearing gage and found negative bearing"
As for Standard Protocol, I will confess that it is very much mine. Whether one gratuitously shares data with the owner is a subjective and circumstantial decision, but if there IS a cerifiable problem on a new instrument, wouldn't you want to know? Wouldn't the client want to know?
------------------------------
David Skolnik [RPT]
Hastings-on-Hudson NY
(917) 589-2625
Original Message:
Sent: 01-14-2026 07:47
From: Peter Grey
Subject: negative bearing in brand new 7' piano
Notwithstanding all of the above, there must have been SOMETHING that prompted Keith to go to the extent he did in checking downbearing on the first call on a nearly new piano. Is this his standard protocol? Is it anyone's standard protocol? It certainly is not mine (unless I have good reason to suspect something). Something he heard, felt, customer statements...etc.
Peter Grey Piano Doctor
------------------------------
Peter Grey
Stratham NH
(603) 686-2395
pianodoctor57@gmail.com
Original Message:
Sent: 01-14-2026 03:25
From: David Love
Subject: negative bearing in brand new 7' piano
Sorry for the lengthy post here but it required some explanation.
David Skolnik wrote: "Using a Lowell component gauge, how can results be mis-read? I've shared with you in the past (I think) how I've modified the device to signal negative front bearing directly behind the front pin, which can create termination issues, without getting into the outright 'floating' strings that Keith described. If there is some area of negative, even if created by excessive DB around it, do we still identify it as Negative DB?... apart from any question of what (if anything) do do about it? Would it still fall within the manufacturer's characterization as "normal"?"
So I think it's best to first review. The ideal is to have positive front bearing and positive rear bearing of some determined amount. The amount of desired net bearing is subject to varying approaches by manufacturers and techs alike. Then there is the measured bearing before strings are brought to tension (pre-tension bearing, we can call it) and the residual bearing after the strings are pulled to tension and the board deflects--how much bearing we have left. Assuming we start with positive pretension bearing, the residual bearing will always be less. But I don't think anyone favors negative net bearing.
In this case, Keith is measuring the residual bearing. As discussed previously, this tells us something but not everything. To have a complete picture you would have to measure the pretension bearing, pull the strings to tension, and then measure the residual bearing (or vice versa if you are in the teardown phase). You can then determine how much the board has deflected and whether you have positive residual bearing. Assuming that the bearing is set up equally across the board in the pretension phase, there can be no net negative residual bearing. That's because as the bearing approaches zero, so does the force pressing the board down. Negative bearing would mean that the strings are running downhill to the bridge as the bearing passes zero into negative territory but continuing to add downward force to the bridge. That's not theoretically possible, at least not in this universe. Though it can happen for other reasons (keep reading).
If we have a mixture of positive and negative bearing measurements in the residual bearing phase, that means that one section of the bridge most likely had a higher downbearing setting than other section(s) and the section(s) with the higher initial setting has forced the section with the lower initial setting into negative territory. So why does this happen.
The bridge, because it is a fairly rigid beam distributes the force at any one point to adjacent sections of the bridge. If we apply a downward force to C4, for example, and it deflects at that point some amount, the section that carries the strings at E4 is also deflecting even though there is no string yet attached there. It is most likely somewhat less because the bridge is responding incrementally along its length. The farther you get from the point of measurement, the less the bridge/SB will deflect meaning that the force is diminishing as we move away from that point but it is still deflected under the original load. Among other things, this makes it difficult to assess what exactly the final load is on the board because at any given point of measurement along the bridge, downward (or upward) forces from adjacent sections are contributing.
Historically, empirically derived rule of thumb was that the initial pretension DB setting should be 1/40th of the tension of the string. The total DB force would be 1/40th of the total string tension. If the total string tension is 32,000 lbs then the cumulative DB force would be 32,000/40 or 800lbs. So, for a 160 lb string that means 4 lbs of downward force which can be calculated as follows to determine the DB angle: (sine of the DB angle X) * (160 lbs) = 4 lbs. The sine of 1 degree is .0175. So, .0175 * angle X * 160 lbs = 4 lbs. Solving for X we get ~1.5 degrees. So to achieve a DB force of 4 lbs for a 160 lb string you will have to set the DB at 1.5 degrees (pretension) which was and still is for many manufacturers--but not all--the standard used for the plain wire section.
This setting in the pretension phase was usually done using what's called "distance bearing" and I'll refer you to the various DB articles in the series I mentioned to explain that. The basic idea is that you stretch a string from the agraffe extending beyond the bridge to the string rest and lower the string until it just touches the front edge of the bridge. The gap, or distance, between the string when held in this position, and the string rest behind the bridge is what's called the distance bearing. It is calculated by the (sine of the desired DB angle) * (the length of the backscale). If the desired angle is 1.5 degrees, the sine for which is .026, then to calculate the distance bearing multiply the sine of the angle times the length of the backscale. If the length of the backscale is 100 mm then the distance bearing, or the gap between the string when it is lowered and just touches the bridge, and the stringrest should measure .026 * 100mm = 2.6 mm.
To determine with the Lowell gauge if this setting is correct, knowing that the Lowell Gauge markings are equal to .003, you would need a net difference between front and backscale of .026/.003 = ~ 9 markings. Placing the gauge on the backscale, center the bubble and then move it to the front scale and the bubble should move 9 markings. But that won't tell you if the front or back are negative or positive, only the value of the net bearing. If you want to measure front and rear components, then first set the gauge on the top of the bridge, center the bubble, move the gauge to the front scale and the bubble should move toward the bridge indicating positive (uphill slope) bearing. Count the number of markings it moves. Now do the same for the backscale. The bubble should again move toward the bridge (for positive bearing). Count the number of markings that the bubble moves. The sum between front and rear should be 9. You can have a combination of negative rear and positive front as long as your net bearing is positive. Negative front bearing combined with positive rear bearing is not as desirable, perhaps undesirable, as you would like to have positive front bearing.
So, in the pretension set up phase, you make adjustments as needed, felt, plate adjustments, aliquot shimming etc, and you do this for 2-4 strings in each section and try and get the bearing as uniform as possible, assuming you're targeting equal DB across the bridge. String the piano and then pull the tension to pitch. You can then measure the same strings you used as guides and see how the bearing has changed. It will be less. How much less depends on the board, rib scale, stiffness, etc and the amount of SB deflectiion. Typically you want to see about 1/3 to 1/2 of the original bearing. YMMV. (I'm leaving the bass section out of this discussion for now but my method is typically to bring everything to tension and then set the DB on the bass bridge at about .5 degrees positive. I don't want a lot there but do want it to be positive.)
Now, finally, to David's question. What happens if you have a section that is negative but everything else is positive, does that mean you have negative bearing? Well, not necessarily. If you didn't predetermine uniform bearing in the pretension setup and, say, you have one section that has 2.5 degrees of bearing (pretension) and an adjacent section that has 1 degree, then it's possible that the 2.5 degree section may push the 1.5 degree section negative. But, that doesn't mean that the section that started at 1.5 degrees doesn't have SB deflection indicating positive DB, at least at some point in the deflection. It just means that the residual measured bearing is reflecting that an adjacent section is pushing that part of the board down so that the strings there are now running downhill to the bridge. Confusing isn't it?
It does mean that the board may be loaded somewhat erratically, or unevenly, that the board has uneven amounts of residual DB, that the board may be deflecting in a somewhat non uniform way but are those things disasters? Not necessarily. However, in the section that is now measuring negative, if the frontbearing is negative (i.e. running downhill to the bridge) then you can have problems associated with negative front bearing which are less efficient transfer of energy, possible distortion, especially on ff blows that might compromise continuous contact of string to bridge top. Either way, as I described earlier, the actual load in any one part of the board can't easily be determined because the forces at any one point will be a combination of the DB force directly over the measured area, as defined by the string we are measuring, plus or minus the forces from any adjacent sections.
As to what is "normal", I would not attempt to answer that question. Each manufacturer has guidelines for acceptable bearing. But a belly that has, as Keith has suggested with his data, a preponderance of negative readings, I would consider that, under any circumstances I can think of, not normal. Does it mean the piano won't function? Of course not. But does it mean that the tonal output is optimized based on standard protocols and expectations? I would say no. Does that mean it's a redo? Maybe, but purposes of this discussion, I don't really have enough information. However, as described, it doesn't look great.
Lowell's Component Downbearing gauge – Pianos Bolduc Shop
------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 01-13-2026 14:50
From: David Skolnik
Subject: negative bearing in brand new 7' piano
David Love -
Extremely grateful for your contributions. Let me try to pose a simple (or simplistic) question:
Using a Lowell component gauge, how can results be mis-read? I've shared with you in the past (I think) how I've modified the device to signal negative front bearing directly behind the front pin, which can create termination issues, without getting into the outright 'floating' strings that Keith described. If there is some area of negative, even if created by excessive DB around it, do we still identify it as Negative DB?... apart from any question of what (if anything) do do about it? Would it still fall within the manufacturer's characterization as "normal"?
------------------------------
David Skolnik [RPT]
Hastings-on-Hudson NY
(917) 589-2625
Original Message:
Sent: 01-13-2026 01:34
From: David Love
Subject: negative bearing in brand new 7' piano
Keith:
Several points to address:
I think of "choked" as resulting from a gross imbalance between downbearing and soundboard compression. When the strings press down on the bridge and therefore on the SB, the reaction to the force pressing down is one of equal and opposite force pressing up against it. However, if the force bearing down on the SB is such that it exceeds the elastic limits of the SB, it compromises the ability of the SB to oscillate freely. The board needs to be able to move back and forth (up and down if you prefer) in response to the strings' vibrations. If the DB is too heavy, the SB can be compressed so tightly that it becomes too stiff to move. The resulting sound will be one which lacks sustain, bloom, and the things we ordinarily associate with good piano tone. The piano will tend to produce more of a "thud" with very short sustain.
This can happen if the bridge is set too high (or plate is too low), resulting in excessive DB, an increase in humidity when the set up is already at the elastic limits of the SB because of high DB but it's likely a manufacturing or design error. I've also seen (and heard) it happen on pianos that have gotten rescaled by increasing the overall tension, for example, by just increasing the plain wire section by 1/2 gauge. Remember that the original design of the SB involves an assessment of the DB force as a result of overall string tension and determining the ribscale. panel thickness, etc., by calculating those forces and what the structure must be able to withstand. If you suddenly add a lot of tension then your original calcs are not going to be consistent with that original balanced (hopefully) design. If you are doing that on an older and crown compromised SB, which is where I've seen this, then you've compounded the problem. Another topic.
In this case, as you have described it, since the bearing is negative and if the strings are pulling the board up (which means the board is pulling down with equal force), it seems unlikely that this would result in "choking", as we've defined it; the inability of the board to oscillate. More likely it would result in poor energy transfer and the tonal problems associated with that.
So, with your new information, it seems that you might have positive front bearing and negative rear bearing. But your previous data suggests that the net bearing is mostly negative. That is more likely to produce the latter outcome associated with poor energy transfer, weak tone, low impedance, distortion, short sustain. It's interesting that there is some descriptive crossover though the acoustic response will be somewhat different.
If, in fact, you can lower the rear aliquots such that you have positive front bearing and healthy net bearing, and assuming the board has adequate crown to begin with, then that would likely remedy the problem. The mechanics of achieving that are a bit more complicated.
If you had adjustable perimeter bolts (always a good idea in a rebuild IMO) then you could simply lower the backside of the plate to increase the rear bearing. However, if you have negative front bearing then you can't correct that by lowering the plate that way because the pinblock determines the height of the front end of the plate. That will remain the same.
You could take down the tension and lower the aliquots by moving them closer to the bridge or by grinding away some of the material but that won't address the part of the piano that doesn't happen to have aliquots. For that area you would have to remove the strings and grind down the string rest area, or remove the plate felt if it's there, depending on the piano's construction. You can also slide the aliquots toward the bridge which will increase the rear bearing but also detune the rear duplex if that's the design. Or you could start over and recap the bridge.
With the exception of the adjustable perimeter bolt solution, I would not undertake any of those other options on a new piano.
As far as assessing DB, many of the comments are correct. You can't really know the exact situation unless you measure DB and crown both at full tension and then again with the tension slacked. My general method for assessing at teardown is to first remove the bass strings (see note at the end of this paragraph). Leave the tension alone otherwise. Take several sample measurements across the scale, maybe 6-8, and mark the strings that you measured. Measure the crown as well which you can by using a stretched string from underneath between the ribs, or a straightedge laid across the rim and measure the distance between SB and straightedge at the perimeter and at the center of that span calculating the difference. The diaphragmizing of the board can give a misread there so you may need to determine how much diphragmizing has taken place or measure the perimeter from a point about 6 inches in from the edge. That's typically the extent of the diaphragmizing--the point at which the rib scalloping starts. Record the net crown and DB before and after. (note: I prefer to do this with the bass strings off for a couple of reasons which I won't get into too much here but has to do with the fact that I set the DB on the bass bridge pretty minimally and lower than the rest of the piano. On cantilevered bridges, the DB can distort the panel due to the flexing of the cantilever--more on this another time.)
That will give you two sets of measurements: DB before and after tensioning the strings as well as crown with and without the DB load. On assessing for a rebuild, you can determine from that info if you have adequate crown, how much the crown is deflecting under load, and also how much DB you can set without the risk of oil-canning the crown (pushing it negative). If you have so little crown that you cannot set any appreciable DB then it's time to replace the board. The go, no go amount of crown is usually around 1/8" YMMV. I'm not going to get into the details of how to calculate all that here as it's not really relevant to this situation but the Gravagne Downbearing Series (PTJ 1988) gives a lot of ways to assess and determine that. I would recommend that reading to anyone interested.
In this particular case the question is do you want to try and be the hero and fix this, refer it back to the dealer/manufacturer (which is what I would do) or just leave it alone. I would inform client as to my findings and send a report to the dealer while copying the manufacturer. You will need to send the component bearing readings for front and rear as well as crown data so it can be determined if a plate lowering/aliquot shaping, is an appropriate remedy that's likely to succeed. Be accurate and record humidity as well.
These situations are always awkward. We feel for the customer who may have something that wasn't set up properly (or worse). We have a dealer or manufacturer whose incentive is sometimes to make the problem go away, a customer who is entitled to know what's going on with their piano, which they, presumably, spent a lot of money on, and us, the technicians, who must be sure that the data we provide is both accurate and complete in order to make the proper diagnosis and assessment while not being self-serving or, if we represent the dealer, put us in a position of a conflict of interest. When in those situations, and I get pressure in opposing directions, my tendency is to advise the customer as best I can, while removing myself as a candidate to do the job, should it come to that, avoid any appearance of conflict of interest, and walk away from it. Since I gather this is a new piano, I might be walking pretty fast. DAMHIK.
------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 01-11-2026 23:59
From: Keith Akins
Subject: negative bearing in brand new 7' piano
Thanks for your response, David. Here are my responses and further questions.
Regarding "choking" perhaps your terminology is more granular than mine. I would understand that a soundboard unstrung would be at a "neutral" position. With excessive bearing it would be near/at/beyond its normal downward excursion (recognizing that in actuality the board doesn't just vibrate up-and-down as a whole). But if there was sufficient bridge pin angle, could it not also be true that the string plane which was above the bridge (if not secured by the bridge pins) when captured by the bridge pins could pull the soundboard up towards the limits of its natural excursion and thereby inhibit vibration in a manner parallel to excessive bearing at the other end of excursion? Based on that understanding, I used the term "choked".
I think lowering the aliquot string rests could perhaps bring some sort of improvement. I say this based on two observations: 1) it is evident from looking that if the string were lowered at the hitch (with the aliquot string rest removed) that it would first hit the bridge and then hit the hitch pin = positive front bearing. 2) I didn't report the front/back bearing components, but the Lowell gage confirms that there is positive front bearing and greater negative back bearing. i.e. the string coming from the capo travels uphill to the front bridge pin and then even more radically goes uphill to the aliquot string rest. So, lowering the backscale would result in net positive bearing simply by bringing the back component down to zero bearing.
Again I appreciate people's engagement on this topic.
------------------------------
Keith Akins RPT
Menominee MI
(715) 775-0022
Original Message:
Sent: 01-11-2026 21:47
From: David Love
Subject: negative bearing in brand new 7' piano
Not entirely true. And you will have to take several measurements across the scale
If you have positive crown and positive bearing you can deduce that the board is experiencing some deflection under load. How much is hard to tell.
If you have zero (or near zero) bearing and positive crown you can't tell if there is deflection under load or not.
if you have negative bearing and positive crown you can't tell much either. The string plane could be holding up the crown.
if you have positive bearing and negative crown you can deduce that the bearing is pressing the crown negative.
Note that you can also have positive and negative bearing on the same board,
You can also determine the relationship between front and rear bearing in a strung piano if you are using a component DB gauge (Lowell type).
Measurements with and without tension will tell you more, of course
------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 01-10-2026 10:40
From: Peter Grey
Subject: negative bearing in brand new 7' piano
I have very good reasons for stating that IMO the true situation of the crown/DB relationship cannot be accurately diagnosed with tension up. It must be destrung (not necessarily strings removed) to truly assess.
I know many will disagree with this, but experience tells me that there are several factors that can lead to a mis-diagnosis...in fact, possibly the diametrically opposite conclusion.
Peter Grey Piano Doctor
------------------------------
Peter Grey
Stratham NH
(603) 686-2395
pianodoctor57@gmail.com
Original Message:
Sent: 01-09-2026 19:03
From: David Love
Subject: negative bearing in brand new 7' piano
Keith
I'm getting into this a little bit late. I haven't read all of the responses so if I'm being redundant, forgive me.
A piano of that age should not have negative bearing. I'm assuming that the humidity levels were somewhat normal. Did you measure crown? Because absolute bearing numbers are only meaningful in their relationship to the amount of crown in the board. If you have a soundboard that has full or adequate crown and you have negative bearing it means that the plate elevation is incorrect though a contributing factor might be the thickness of the pin block, which is difficult to address without replacing it.
If the board has no crown than there's no way to compensate. Since you took downbearing measurements with a Lowell downbearing gauge, What are the front and rear bearing measurements? This would be important to know.
Ten units on a Lowell downbearing gauge means almost 2° of negative bearing. That's a lot.
For the dealer to call that normal is troubling, to say the least. If I rebuilt a Piano and it came out that way, I'd be redoing it
------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 01-07-2026 01:49
From: Keith Akins
Subject: negative bearing in brand new 7' piano
Interesting situation here..
Subject piano: High quality expensive European piano
Findings:
As customer's technician I inspected the piano throroughly at first local service appointment (customer gets grumpy if tuning interval is longer than 6 weeks). Piano doesn't sound bad and has an apparent high build quality although I didn't think it sounded all that great for the price. I checked bearing using a Lowell bearing gage and found negative bearing of 2-10 units in the top two sections and little bearing in the tenor. To verify the situation I removed 2 bridge pins and confirmed that the string was flying visibly above the bridge with no contact and the ability to slide material under the string on the bridge with no friction or drag whatsoever.
I then contacted the dealer who arranged for factory technician to visit. Said factory technician used factory setup jigs and referred to notes taken during manufacture and pronounced the piano to be "normal" with no deviation from factory setup. The dealer than contacted me saying that the matter was considered closed.
Personally, as a rebuilder with soundboard replacement experience plus having visited several piano factories, I don't believe that a piano that is substantially higher priced than a S&S B should have negative bearing at any point regardless of design or assembly philosophy. (Maybe minimal or zero in the low tenor or bass--maybe. But certainly not in the top two treble sections.) The dealer is well meaning but has no direct understanding of the topic--having never repaired a piano, replaced a soundboard or carved a bridge, so he has to accept authority and the authority he accepts is the expensive factory technicians over someone who could be perceived as a backwoods tuner. He sent a technician to the factory but that technician while competent for general service has no background in major rebuilding or other factory visits so is pretty much in awe of this particular manufacturer and dubious that they could do anything wrong.
So, I'd be glad for any feedback on this topic.
------------------------------
Keith Akins RPT
Menominee MI
(715) 775-0022
------------------------------